Potential Environmental Impacts of

Bioenergy Crop Production

September 1993

OTA-BP-E-118

NTIS order #PB94-107521

GPO stock #052-003-01353-3
Recommended Citation:

U.S. Congress, Office of Technology Assessment, Potential Environmental

Impacts of Bioenergy Crop Production-Background Paper, OTA-BP-E-118

(Washington, DC: U.S. Government Printing Office, September 1993).

For sale by the U.S. Government Printing Office

Superintendent of Documents, Mail Stop: SSOP, Washington, DC 20402-9328

ISBN 0-16 -042099-7
Foreword

B

ioenergy crops are receiving increasing attention as a potentially low cost

and large scale renewable source of energy. This report reviews how such

crops could potentially affect soil quality and soil erosion, water quality,

air quality, habitat for a variety of species, and the global environment.

From this analysis, it examines how research and development agendas for energy crops might be expanded to better understand these impacts and to reduce

potential negative environmental impacts and enhance the positive.

The report also briefly reviews other impacts of bioenergy crops, including the potential relationship between energy crops, Federal agricultural supports, rural income, and national dependence on imported fuels. In the wake of

the devastating Midwest floods, energy crops might be considered as a more

robust crop for flood prone areas. Although energy crops have long-term potential, much research and development remains to be done in order to understand

the full range of their environmental impacts, positive and negative, and an

extensive political dialogue is needed to determine how best to balance the

numerous competing economic/environmental, rural/urban, regional and other

interests potentially affected.

This study is the first product of a larger assessment of renewable energy

technology requested by the House Committee on Science, Space, and

Technology and by the House Committee on Energy and Commerce. The full

assessment, to be published in 1994, will address environmental issues more

broadly as well as provide detailed analyses of: renewable energy resources; the

cost and performance of renewable energy technologies; commercialization

issues; and policy options.

OTA appreciates the invaluable advice and assistance of the many people

who contributed to this project, including the advisory panel, participants in the

workshop, reviewers, and contractors. OTA, however, bears the sole responsibility for the contents of this report.

Roger C. Herdman, Director

. . .

Ill
Advisory Panel

Mr. Robert W. Fri

Chairman

Resources for the Future

Dr. Jim Batchelor

SF Services, Inc.

Mr. Art Brooks

Sun Earth, Inc.

Mr. Edward J. Carlough

Sheet Metal Workers International

Association

Mr. John Corsi

Solarex

Mr. J. Michael Davis

Consultant

Dr. David Dawson

Forest Policy Consultant

Mr. W. Densmore Hunter

Weyerhauser Co.

Mr. Renz D. Jennings

Arizona Corporation Commission

Dr. David Kearney

Kearney and Associates

Mr. John Kennedy

Allied-Signal Aerospace

Mr. Alden Meyer

Union of Concerned Scientists

Dr. Roberta Nichols

Ford Motor Co.

Mr. Mike Nicklas

Innovative Design

Mr. Dale Osborn

U.S. Windpower, Inc.

Ms. Elizabeth Paine

State House, Maine

Mr. Bruce Pasternack

Booz, Allen, and Hamilton

Ms. Maria Richter

Morgan Stanley & Co., Inc.

Mr. Victor Shaio

New Energy Corporation of

Indiana

Mr. Scott Sklar

Solar Energy Industries

Association

Mr. Carl Weinberg

Weinberg Associates

Dr. Robert H. Williams

Princeton University

Mr. Kurt E. Yeager

Electric Power Research Institute

INVITED OBSERVERS

Dr. Robert San Martin

U.S. Department of Energy

Mr. William G. Rosenberg

Environmental Protection Agency

Dr. Thomas D. Bath

National Renewable Energy

Laboratory

NOTE: OTA appreciates and is grateful for the valuable assistance and thoughtful critiques provided by the advisory panel

members. The panel does not, however, necessarily approve, disapprove, or endorse this background paper. OTA assumes full

responsibility for the background paper and the accuracy of its contents.

iv
Peter D. Blair

Assistant Director, OTA

Industry, Commerce,

and International

Security Division

(beginning February 1993)

Energy and Materials Program

Manager

(until August 1993)

Lionel S. Johns

Assistant Director, OTA

Energy, Materials,

and International

Security Division

(until February 1993)

Emilia L. Govan

Energy and Materials Program

Manager

(beginning August 1993)

Preject Staff

Samuel F. Baldwin

Project Director

ADMINISTRATIVE STAFF

Lillian Chapman

Office Administrator

Linda Long

Administrative Secretary

Phyllis Aikens

Secretary
contractors and Reviewers of

Workshop Papers

CONTRACTORS

Dr. W. Lee Daniels

Department of Crop and Soil

Environmental Sciences

Virginia Polytechnic and State

University

Dr. Raymond N. Gallaher

Agronomy Research Laboratory

University of Florida, Gainesville

Dr. Phillip E. Pope

Department of Forestry and Natural

Resources Purdue University

Mr. Steve Shaffer

Agricultural Resources Branch

California Department of Food and

Agriculture

Dr. Michael L. Wolfe

Department of Fisheries and

Wildlife

Utah State University

REVIEWERS

Charles Blanchard

Envair

James H. Cook

National Audubon Society

David Dawson

Forest Policy Consultant

Wildon Fontenot

Soil Conservation Service, USDA

Kathryn Freemark

Environmental Protection Agency

Robert B. Grossman

Soil Conservation Service, USDA

Sharon Haines

International Paper

Wayne Hoffman

National Audubon Society

Maurice Mansbach

Soil Conservation Service, USDA

Helga von Miegroet

Utah State University

Walter Parham

Office of Technology Assessment

Fran Pierce

Michigan State University

Jack Ranney

Oak Ridge National Laboratory

Theryl Robertson

Soil Conservation Service, USDA

David Schertz

Soil Conservation Service, USDA

Lawson Spivey

Soil Conservation Service, USDA

James Sweeney

American Forest and Paper

Association

Brent Takemoto

California Air Resources Board

J.T. Touchton

Auburn University

Anthony Turhollow

Oak Ridge National Laboratory

Jane Turnbull

Electric Power Research Institute

Donald D. Tyler

University of Tennessee

Clive Walker

Soil Conservation Service, USDA

Robin White

Office of Technology Assessment

NOTE: OTA appreciates and is grateful for the valuable assistance of the contractors who prepared papers for the workshop

and for the thoughtful critiques provided by the reviewers of these papers. The reviewers and contractors do not, however,

necessarily approve, disapprove, or endorse this background paper. OTA assumes full responsibility for the background paper

and the accuracy of its contents.

vi
workshop Participants

Dr. Jack Ranney, Chairman

Oak Ridge National Laboratory

Dr. Jim Batchelor

SF Services, Inc.

Dr. W. Lee Daniels

Virginia Polytechnic and State

University

Mr. John Ferrell

Department of Energy

Dr. Raymond N. Gallaher

University of Florida, Gainesville

Prof. David O. Hall

University of London

Dr. Wayne A. Hoffman

National Audubon Society

Dr. Robert Jenkins

The Nature Conservancy

Dr. Stan Krugman

U.S. Forest Service

Dr. Gary Margheim

U.S. Department of Agriculture

Dr. Ralph Overend

National Renewable Energy

Laboratory

Dr. Phillip E. Pope

Purdue University

Mr. Steve Shaffer

California Department of Food and

Agriculture

Dr. James Sweeney

American Forest and Paper

Association

Ms. Jane Turnbull

Electric Power Research Institute

Mr. Dale V. Wilhelm

Tennessee Valley Authority

Dr. Arthur Wiselogel

National Renewable Energy

Laboratory

Dr. Michael L. Wolfe

Utah State University

NOTE: OTA appreciates and is grateful for the valuable assistance and thoughtful critiques provided by the workshop participants. The workshop participants do not, however, necessarily approve, disapprove, or endorse this background paper. OTA

assumes full responsibility for the background paper and the accuracy of its contents.

vii
Reviewers and Contributors

Thomas D. Bath

National Renewable Energy

Laboratory

Charles Blanchard

Envair

Elizabeth Chornesky

Office of Technology Assessment

James H. Cook

National Audubon Society

W. Lee Daniels

Virginia Polytechnic and State

University

David Dawson

Forest Policy Consultant

Robert W. Fri

Resources for the Future

Raymond Gallaher

University of Florida

Emilia Govan

U.S. Congress

Office of Technology Assessment

David O. Hall

University of London

John Kennedy

Allied-Signal Aerospace

Stanley Krugman

U.S. Forest Service

Roberta Nichols

Ford Motor Company

Walter Parham

U.S. Congress

Office of Technology Assessment

Philip Pope

Purdue University

Jack Ranney

Oak Ridge National Laboratory

Thyrele Robertson

Soil Conservation Service, USDA

Steve Shaffer

California Department of Food and

Agriculture

Anthony Turhollow

Detailee

Oak Ridge National Laboratory

Jane Turnbull

Electric Power Research Institute

K. Shaine Tyson

National Renewable Energy

Laboratory

Dale V. Wilhelm

Tennessee Valley Authority

Robert H. Williams

Princeton University

Robin White

U.S. Congress

Office of Technology Assessment

Carl Weinberg

Weinberg Associates

Arthur Wiselogel

National Renewable Energy

Laboratory

Michael L. Wolfe

Utah State University

Kurt E. Yeager

Electric Power Research Institute

NOTE: OTA appreciates and is grateful for the valuable assistance and thoughtful critiques provided by the reviewers of and

contributors to this background paper. The reviewers and contributors do not, however, necessarily approve, disapprove, or

endorse this background paper. OTA assumes full responsibility for the background paper and the accuracy of its contents.

. . . Vlll
contents

1

2

3

4

Executive Summary 1

Background 1

Environmental Impacts 2

Rural Economic Impacts 3

Federal Budget Impacts 3

Trade Balance Impacts 3

Baseload Power 3

The Bioenergy Agenda 4

Introduction 7

The U.S. Energy Sector and Bioenergy 8

The Rural Economy and Bioenergy 15

Bioenergy Resources 17

Close 20

Potential Environmental Impacts 23

Introduction 24

Soil Quality 24

Water Quality 34

Air Quality 37

Habitat 39

Greenhouse Gases 50

Cropping Practices 54

Close 55

The Bioenergy Agenda 57

Research, Development, and Demonstration 57

Markets and Barriers 61

Close 64

APPENDIXES

A Related OTA Studies 65

B Units and Conversion Factors 66

INDEX 69
Executive

Summary 1

B

ioenergy crops have the potential to improve the environment, increase rural incomes, and reduce Federal

budget deficits and the U.S. trade imbalance. In the

wake of the devastating Midwest floods, bioenergy

crops may also offer a more robust crop for flood-prone regions.

To realize this broad potential, continuing research and development and environmental monitoring will be required. It will also

be necessary to conduct some long-term and large-scale demonstration programs, and to address a variety of market barriers and

distortions. Haphazardly implementing large-scale bioenergy

programs without such a foundation could damage the environment and reduce potential economic benefits.

BACKGROUND

Bioenergy crops include annual row crops such as corn, herbaceous perennial grasses (herbaceous energy crops—HECs) such

as switchgrass, and short-rotation woody crops (SRWCs) such as

poplar. Annual row crops are grown in essentially the same

manner as their food crop counterparts and consequently offer few

or no environmental benefits over conventional agricultural practices. Because of this, annual row crops are not examined further

in this report. ]

HECs are analogous to growing hay, harvesting the crop for

energy rather than for forage. SRWCs typically consist of a

plantation of closely spaced (2 to 3 meters apart on a grid) trees

that are harvested on a cycle of 3 to 10 years. Following harvest,

The net

environmental impacts

depend on what the land

was previously used for,

the particular energy

crop, and how the

crop is managed.

1 Energy crops (often annual row crops) exist which produce starches, sugars, oils, and other specialty plant products for energy. On a

national basis, however, their energy production potential is much lower and their costs higher than for HECs and SRWCs. Consequently, they

are not considered further in this report.

1
2 I Bioenergy

HECs regrow from the remaining stubble and

SRWCs regrow from the remaining stumps. Such

harvests may continue for 15 to 20 years or more

without replanting. Fertilizer and maintenance

may be required annually, however. These energy

crops may be grown by farmers with only modest

changes in farming practices.

A number of factors are considered in selecting

specific HECs and SRWCs to be grown. These

include their productivity (growth rate); robustness (ability to withstand weather, pests, and

disease); efficiency in using water; overall environmental impacts (soil, water, air, habitat, greenhouse gases); and others.

HECs and SRWCs produce very large quantities of biomass—straw, wood, bark, and leaves—

composed principally of cellulose and lignin.2

These feedstocks maybe used to generate electricity or be converted to liquid fuels or combustible

gases.

ENVIRONMENTAL IMPACTS

Bioenergy crops can be substituted for conventional crops or be grown on agricultural set-aside

or conservation reserve program lands, degraded

lands, or elsewhere. The net environmental impacts depend on what the land was previously used

for, the particular energy crop, and how the crop

is managed. For example, as a substitute for conventional agricultural row crops such as corn or

soybeans, properly managed HECs and SRWCs

can help stabilize erosive soils or perhaps filter

agricultural chemicals and sediments before they

reach water supplies. 3 They may help provide

habitat directly or serve as buffers around, or

corridors between, fragments of natural forest,

wetlands, or prairie. (Such habitat benefits will,

however, also depend on the particular animal

species.) In contrast, substituting energy crops for

hay, pasture, or well-managed Conservation Reserve Program Lands generally will have mixed

environmental impacts, both positive and negative.

It is important to remember that bioenergy

crops are similar to agricultural crops and should

not be confused with natural habitats.4 Current

plant species under consideration for use as bioenergy crops are primarily native species that

evolved in the regions where they may be used.

These crops can provide greater biodiversity on a

landscape level than typical agricultural crops, and

thus can enhance wildlife habitat. The benefits

may be transient, however, depending on the management and harvesting practices required to produce an economically viable crop.

Bioenergy can potentially also improve urban

and regional air quality by reducing SOX and NOX.

If poor-quality equipment or controls are used,

however, emissions of particulate and certain

organic compounds could be increased by the

substitution of bioenergy for conventional fuels.

When grown on a sustainable basis,5 bioenergy

can offset emissions of greenhouse gases from

fossil fuels and thus slow potential global warming. In the long-run, if greenhouse gas emissions

are not reduced, potential warming may cause the

2 Cellulose is the fibrous material in plants and lignin is the “glue” that binds the fibers together. Because of this content, these crops are

also known as lignocellulosic energy crops.

3 To serve as a filter and to be harvested periodically for energy, energy crops may require more complex and careful management than is

typical for energy crops which do not serve such demanding multiple functions.

4 Defining “natural habitat” may be difficult and controversial because past decades—sometimes centuries-of clear cutting, selective

harvesting of economically valuable trees, and fire suppression have altered many U.S. forests, often leading to an increased concentration of

plant species with lower economic or ecological value. Similar alterations have occurred over many other U.S. landscapes, including prairie

and wetlands. Although defining how much modification still qualifies as “natural” is thus challenging, the term will be used broadly here to

include all lands that support a significant quantity and variety of indigenous plants and animals. For this report, only current or former

agricultural lands or highly degraded lands are considered for energy crops.

5 For example, as much new biomass is grown as is burned for fuel. There are also potential sequestration benefits for both soil carbon and

standing biomass.
Chapter l–Executive Summary 13

loss of natural habitats throughout the United

States as well as globally.

RURAL ECONOMIC IMPACTS

Rural economies in the United States have been

hard pressed for many years. Between about 1980

and 1990, the U.S. share of the world’s total agricultural trade dropped from 28 percent to 21 percent. At the same time, the European share grew

from about 13 percent to 19 percent. China is now

the world’s second largest corn exporter, and Brazil is a major exporter of soybeans. Some expect

that parts of Eastern Europe and the former Soviet

Union could become food exporting powerhouses

in the future.6 Roughly half of the ship-loading

grain terminals in the United States are reportedly

closed, about to close, or for sale.’ Due to these

pressures, there is a growing need to find alternative crops for rural agricultural communities: to

provide employment, to stabilize rural incomes,

and to maintain the rural infrastructure of equipment and supplies distribution and service. Bioenergy crops are one such alternative if mechanisms

can be found to overcome a variety of market and

institutional obstacles to their use.

FEDERAL BUDGET IMPACTS

The Federal budget is likewise under great pressure and agricultural programs, like everything

else, are under increased scrutiny for savings. Currently, Federal programs to prevent soil erosion8

and various commodity support programs to

strengthen crop prices cost roughly $10 billion per

year. Bioenergy crops are a potential alternative

cash crop that could protect fragile soils or could

be grown on lands previously idled in order to

strengthen commodity crop prices. Earnings from

the energy crop might then allow Federal supports

to be eased while maintaining farm income. Of

course, the relative environmental benefits of energy crops versus current soil conservation programs such as the Conservation Reserve Program

would again depend on the specific energy crops

grown and how the land was managed. The relative economic and budgetary value of producing

bioenergy crops would have to be compared to

potential alternative uses of the land. Designing

Federal programs to achieve such ends while minimizing disruption and risk to farmers also presents

challenges.

TRADE BALANCE IMPACTS

U.S. expenditures on foreign oil are currently running about $50 billion per year and are destined to

increase sharply as domestic oil production continues to decline. Several U.S. electric utilities are

also now importing low-sulfur coal. Bioenergy

crops could potentially offset some of these imports. Although bioenergy by itself is unlikely to

eliminate fuel imports, it could make a substantial

contribution to our energy needs.

BASELOAD POWER

In addition to the above potential benefits, biomass

energy may play a particularly important role if

there is a greater emphasis in the future on using

renewable forms of energy. In contrast to intermittent renewable such as solar (available when the

sun shines) and wind (available when the wind

blows), biomass energy comes as an already stored

solar energy resource. It can thus be used as

needed rather than as available. Although the intermittency of solar and wind energy can be moderated by gathering them over a large geographic

region, they still require dispatchable backup

power such as can be provided by biomass.

6 In the longer term, population growth in developing countries may surpass agricultural productivity growth and increase demand for food

imports. Some of this demand may be supplied by the United States. No one knows, however, what the net effect is likely to be.

7 Scott Kilman, “U.S. Is Steadily Losing Share of World Trade in Grain and Soy beans,” Wull Street Journal, Dec. 3, 1992, p. Al.

8 An example is the Conservation Reserve Program (CRP) which pays farmers to take lands out of production of a marketable crop for

10 years in order to protect more erodible or fragile soils with permanent cover.
4 I Bioenergy

THE BIOENERGY AGENDA

While bioenergy crops have great potential to help

meet a number of pressing problems, the extent to

which this potential can be realized will depend on

a number of factors. These include:

■ Research and development—Relatively little

R&D has been done on the environmental impacts of energy crops in the United States. Most

studies have been short-term, limited in scope,

and confined to small scales. Although careful

studies have been conducted at a handful of sites

across the United States, the results tend not to

be readily transferable to significantly different

sites, crops, or management practices. Consequently, most practices in the field, as well as

much of the analysis in this report, have been

developed by analogy with conventional agricultural or forestry practices. This approach has

significant limitations. For example, energy

crops can have significantly deeper and heavier

rooting patterns than conventional agricultural

crops, affecting soil carbon balances, water balances, and agricultural chemical fates. Even less

is known about the habitat impacts of energy

crops; some of the very first studies are just now

underway at a few locations. Virtually all proposed habitat practices are based on ecological

theory and by analogy with conventional crops.

Thus, R&D is needed on soil, water, and air

quality issues, and these environmental analyses should be done on a total fuel-cycle basis.

R&D is also needed on how to design desirable

landscapes at the micro and macro level in order

to realize the potential habitat benefits of bioenergy crops, including the relative benefits of

buffers and corridors using energy crops—for

which almost no R&D has been done to date.

Inter-planting multiple species can potentially

improve habitat but may complicate energy

conversion processes which are typically designed for a narrowly defined input feedstock.

Thus, R&D is needed to tailor energy conversion processes to accept a wide variety of mixed

feedstocks, particular] y those with special habitat value. Landscape design and conversion

processes must also maintain high productivity

and reasonable economic returns. Experience

gained in Europe and elsewhere in recent years

may be useful in addressing these issues.

■ Demonstrations-Demonstrations are needed

(and should be closely coupled with the above

R&D agenda) in order to determine how best to

structure energy crops for their environmental

(soil, water, air, habitat) value, to determine

what their environmental value actually is by

field observations, and to establish pilot energy

conversion facilities, such as bioenergy to electricity, bioenergy to liquid (transport) fuels such

as ethanol or methanol, or bioenergy to other

petrochemical substitutes. Such demonstrations

are most useful if they are of sufficient scale to

clarify the characteristics of a fully functional

infrastructure and thus reliably and cost-effectively link the feedstock production activities to

the energy conversion processes.

■ Commercialization—Farmers cannot afford

to grow biomass unless electric power or fuel

conversion facilities are in place to purchase it.

Conversion facilities cannot be built unless the

biomass feedstock is available and an end-use

market is ready. An end-use market is difficult

to develop without assured supplies of fuel.

Infrastructure development may be needed at all

these levels. Mechanisms for addressing this

“chicken and egg” problem of developing

bioenergy production, conversion facilities, and

end-use markets are needed. On the biomass

production side, this may require addressing

issues of farmer risk, flexibility, finances, education and extension, and other issues. Fundamental issues of land use and property rights

may also arise in connection with environmental considerations of energy crops. Studies

of how best to address these issues might be

conducted in parallel with demonstrations.

■ Institutional Issues—The multiplicity of sectors affected by energy crops—agriculture, energy, environment, forestry, etc.—poses a

substantial and, in some ways, unique institu-
Chapter l–Executive Summary 15

tional challenge in developing coherent policy

goals, processes, and effective coordination.

Energy crops may help solve some of our national energy and environmental problems. They

potentially can provide a modest fraction of our

current level of energy needs, perhaps 10 to

30 percent, and they have potential environmental

benefits compared with conventional agricultural

crops. Energy crops are no substitute, however, for

natural habitats on contiguous landscapes; energy

cropping should primarily be considered for surplus agricultural and degraded lands. Finally, the

regional impacts of energy crops will be mixed.

They cannot readily be grown everywhere. They

are most likely candidates where agriculture and

forestry are already well-established industries.

Within these limits, energy crops show promise

to help meet a number of national needs-economic, environmental, budgetary, and national security. The extent to which this potential can be

realized will depend on how well the many competing economic/environmental, rural/urban, regional, and other interests can be balanced. This

background report is intended to contribute to that

national debate.
Introduction

B

iomass is mankind’s oldest energy resource. It has

been periodically misused throughout history, sometimes with serious environmental and other consequences. Cyprus provided the bronze needed by the

ancient Greeks for weaponry; wood shortages are a likely cause

of the reduction in bronze smelting there by 1300 BC which

forced rationing on the Greek mainland and weakened the Mycenaens to outside attack. Aristotle and Plato documented the

destruction of forests in Greece itself and the resulting environmental degradation. The Remans were forced to import wood

from North Africa, France, and Spain to keep their industries,

public baths, and military operational. England suffered severe

deforestation in many areas during her early industrial period—

citizens even rioted over rising wood prices; eventually the transition to coal was made. ] The United States went through a similar

transition among energy resources over the past 150 years (figure

2-l).

Today, a variety of concerns has prompted a new look at

biomass as an energy resource. Biomass, in combination with

advanced combustion and/or conversion technologies, has the

potential to contribute needed energy resources for transport,

electric power, and industry. Bioenergy may provide economic

benefits to the rural economy and possibly to the Nation. By

substituting for imported oil, bioenergy also may provide some

national security benefits. These potential economic, budgetary,

and security values of bioenergy must be weighed, however,

2

Today, a variety of

concerns has prompted

a new look at biomass

as an energy resource.

1 John Perlin and Boromir Jordan, “Running Out--42OO Years of Wood Shortages,” Convolution Quarterly, Spring 1983, pp. 18-25; Erik

P. Eckholm, Losing Ground: Environmental Stress and World Food Prospects (New York, NY: W.W. Norton and Company, 1976).

7
8 I Bioenergy

Figure 2-I —U.S. Energy Consumption Patterns

from 1850 to 1990

Percent of total energy consumption

70 T 1

60

50

40

30

20

10

0

1850 1875 1900 1925 1950 1975

This figure shows the generational shift from one fuel to the next for the

United States, from wood in the 1800s to coal by the turn of the century,

and then to oil and gas from the 1950s on.

SOURCES: Office of Technology Assessment; J. Alterman, A Historical

Perspective on Changes in U.S. Energy-Output Ratios, EPRI EA-3997

(Palo Alto, CA: Electric Power Research Institute, June 1985).

against alternative uses of the land and other

means of meeting these needs.

THE U.S. ENERGY SECTOR AND

BIOENERGY

In the United States,

2 bioenergy accounts for

roughly 4 percent of total energy use, or about 3

Exajoules (EJ).3 Oil, coal, and natural gas contribute 41 percent (35 EJ), 23 percent (20 EJ), and

25 percent (21 EJ) respectively (figure 2-2).4 The

primary uses of bioenergy in the United States are

industrial cogeneration, primarily in the pulp and

paper industry, and for residential heating by wood

stoves. Municipal solid waste and ethanol provide

most of the remaining bioenergy (table 2-1).5

The Transport Sector

Transportation consumes about one-fourth of

total U.S. primary energy use and nearly twothirds of oil use. Of U.S. oil consumption—which

provides 42 percent of the total U.S. energy consumption of about 85 EJ—roughly half is now

imported and this share is increasing. With current

policies, U.S. imports of oil are likely to increase

dramatically over the next several decades (figure 2-3).

Renewable energy resources and technologies—particularly bioenergy-offer the potential

to reduce these trends in the longer term. Technologies for biomass feedstock conversion and use

in the transport sector are given in box 2-A.

Whether or not this potential can be realized,

however, remains uncertain and depends on the

details of their cost and performance compared

Table 2-1—U.S. Biofuel Production and Use, 1989

Fuel ExaJoules

Wood

Industrial

Residential

Utility

Biofuels from waste

Municipal solid waste combustion

Manufacturing waste

Landfill gas

Ethyl alcohol

Total

(::;)

(0.9)

(0.01)

0.36

(0.23)

(0.10)

(0.03)

0.075

3.04

SOURCE: Energy Information Administration, “Estimates of U.S. Biofuels Consumption 1989,” U.S. Department of Energy, Washington,

DC, April 1991.

2 Bioenergy is critical to the economies of developing countries, particularly in rural areas. See, for example: U.S. Congress, Office of

Technology Assessment, Energy in Developing Countries, OTA-E-486 (Washington, DC: U.S. Government Printing Office, January 1991);

U.S. Congress, Office of Technology Assessment, Fueling Development: Energy Technologies for Developing Countries, OTA-E-516

(Washington, DC: U.S. Government Printing Office, April 1992).

3 See appendix B for units, their definition, and their equivalences.

4 U.S. Department of Energy, Energy Information Administration, Annual Energy Review, 1992, Report No. DOIYEIA-0384(92), June

1993.

5 For a de~iled bibliography, see: United States Depmment of Agriculture, “Biofuels: January 1986-August 1992,” National Agricultural

Library Quick Bibliography Series QB 92-63, September 1992.
Chapter 2–introduction 19

Figure 2-2—U.S. Energy and Oil Consumption, 1989

Total energy consumption Total oil consumption

Natural gas, 249% . .

20.5

Coal, 23%

19.9

----

Other, 11°/0 ------

9.3

----

----

Oil, 42%

36.1

... - ----

------

----

-------- -.

Electric power, 1.8 5 %

Residential/commercial, 2.8 8%

Industry, 8.8 24%

Transportation, 22.7 63°/0

(10 MBPD)

Total: 85.8 EJ Total: 36.1 EJ (17 MBPD)

This figure shows U.S. energy consumption for oil, coal, natural gas, and others, and breaks oil consumption down by its end use. About 42 percent

of U.S. energy consumption is in the form of oil and nearly two-thirds of this oil is used for transport.

SOURCE: Energy Information Administration, Annual Energy Review 1992, U.S. Department of Energy, DOE/EIA-0384(92), June 1993.

with alternative fuels and technologies, as well as

the larger context of urban design, the development of transport infrastructures, and internalizing

the external costs of fossil fuel use and transport

generallyo

6

The Electricity Sector

Coal, nuclear, hydro, and natural gas are the

principal sources of electricity in the United

States. Bioenergy, primarily wood and wood

wastes in the forest products industry, is an important fuel for industrial cogeneration. Independent

power producers are also turning frequently to

bioenergy resources, including wood, municipal

wastes, and landfill gas, for power production

(table 2-2). More than 8 GW of biomass-fired capacity are now installed in the United States.7

Utilities are becoming increasingly interested

in biomass as a fuel for power production. Factors

contributing to this interest include: improved

technologies for burning/gasifying biomass and

generating power (see box 2-A);8 pressure to reduce emissions under the Clean Air Act Amendments of 1990; the 1.5 cent/kWh credit authorized

under the Energy Policy Act of 1992 for closed

loop biomass systems; and others.

In addition, biomass-fueled electricity generation may play a particularly important role if there

is a greater emphasis in the future on using renewable forms of energy. In contrast to intermittent

6 A forthcoming Office of Technology assessment charts a variety of future renewable energy resource and technology paths for transport;

analyzes their relative economic, environmental, and technological performance vis a vis conventional fossil-fueled systems; and examines the

key RD&D and commercialization issues that must be addressed if their potential is to be realized. Technologies examined include ethanol,

methanol, and hydrogen used in internal combustion engines and fuel cell vehicles. Broader issues of urban design, infrastructure development,

and the externalities of transport are also reviewed there.

7 National Wood Energy Association, National Biomass Facilities Directory, Arlington, VA, 1990.

8 Robert H. Williams and Eric D. Larson, “Advanced Gasification-Based Biomass Power Generation,” Thomas B. Johansson, Henry Kelly,

Amulya K.N. Reddy, and Robert H. Williams (eds.), Renewable Energy: Sources for Fuels and Electrcity (Washington, DC: Island Press,

1993).
10 I Bioenergy

Figure 2-3—U.S. Oil and Supply Demand Futures

25 Millions of barrels per day

Total de

20 -

15 - Net Imports

10 -

5 -

4

NGL and other

o“ 1 1 ! 1 1 1

1950 1%0 1970 1980 1990 2000 2010 2020

U.S. domestic oil production is declining, while U.S. oil demand is rising

with population and economic growth. Shown here is the projected rise

assuming that the new cars and light trucks in the United States have

their fuel efficiencies frozen at 1990 levels (28 mpg). “Lower 48” represents oil production in the lower 48 states; “Alaska” is the oil production

from Alaska, and NGL and other are Natural Gas Liquids and other

sources of liquid fossil fuels.

SOURCE: Office of Technology Assessment. Baselines adapted from

Energy Information Administration, Annual Energy Outlook 7997, U.S.

Department of Energy, DOE/EIA-0383(91), March 1991.

renewable such as solar (available when the sun

shines) and wind (available when the wind blows),

biomass energy comes as an already stored solar

energy resource. It can thus be used as needed

rather than as available. Although the intermittancy of solar and wind energy can be moderated

by gathering them over a large geographic region,

they still require dispatchable backup power such

as can be provided by biomass.9

The Industrial Sector

The industrial sector uses roughly one-third of

primary energy in the United States. Wood as a

fuel contributes about 8 percent of total industrial

sector primary energy use, mainly in the pulp and

.

Table 2-2—U.S. Winning Competitive Bids for

New Capacity, 1984-1992

Capacity

MW

Natural gas 6,628

Coal 1,969

Refurbishment 1,127

Coal wastes 720

Oil 340

Coke 165

Total fossil 10,949

Geothermal 825

Wood and biomass 776

Municipal waste 564

Hydro 125

Wind 63

Landfill gas 28

Total other 2,381

Note that these include only winners from competitive bidding solicitations. Many other power plants, primarily fossil-fueled, were built

outside of competitive bidding solicitations.

SOURCE: Robertson’s Current Competition, vol. 3, No. 2, May 1992.

paper industry where it contributes as much as

three-quarters of energy needs (figure 2-4).10

Industry is interested in increasing use of these

fuels. For example, the typical pulp and paper

operation has three principal waste streams which

can provide energy: hog fuel, black liquor, and

forest residues. Hog fuel is the bark, sawdust, and

other scrap produced in reducing logs to feedstock

for the pulping process. Hog fuels could supply

about 3 GJ11 per tonne of pulp produced (GJ/tp).

Black liquor, from the chemical pulping process,

averages an energy content of about 13 GJ/tp.

Other residues are currently left in the forest when

harvesting the trees. A portion of these forest

residues might be collected, but the long-term

impact this would have on forest soils would need

to be examined closely (see ch. 3). If fully recovered, the estimated energy content of forest resi9 Other ~newable energy resources that can similarly provide bmeload power include geothermal ~d hydropower.

10 This i5 the energy used at the site and does not inc]ude energy losses in generation, transmission, and distribution of electricity from

offsite to the plant, the refinery losses of converting crude oil to fuel oil and transporting it to the site, or other such offsite losses.

11 Fifty kilos of dry wood have an energy content of about I gigajOUk (GJ).
Chapter 2–introduction 111

Box 2-A--Bioenergy Conversion Technologies

Biomass can be used directly to generate electricity or it can be converted to a liquid (or gaseous)

transportation fuel.

The physical and chemical composition of biomass feedstocks varies widely, potentially requiring the

tailoring of particular conversion technologies to specific biofuels (with corresponding negative impacts on habitat

if narrowly specified monoculture must be used—-see ch. 3). The relatively low bulk densities of biomass and

large required collection areas limit the amount of biomass transported to any given site. This constrains the

size of individual conversion facilities and limits the extent to which economies of scale in capita! and other costs

can be captured.1

Electricity. Virtually all existing biomass electric plants use steam turbine technology and, due to use of

old, Inefficient, and small-scale technologies, their efficiency tends to be low-l 7 to 23 percent in California, for

example. in comparison, modem coal plants run at efficiencies of perhaps 35 percent. Steam turbine technology

is fairly mature and few advances are foreseen for biomass. Improvements are possible, however, in biomass

handling. Whole-tree energy systems, for example, use the flue gas for drying, reduce the required handling,

increase net energy efficiencies slightly (in part through a higher pressure steam cycle), and avoid chipping

costs.

Of greater potential is to gasify the biomass and use the gas generated to power a gas turbine. Gasifiers

and gas turbines are relatively insensitive to scale and can operate at much higher efficiencies than steam

turbines in the range of sizes suitable for biomass systems.

In a biomass gasifier/gas turbine system, biomass is gasified in a pressurized air-blown reactor and the

products cleaned of particutates and other contaminants before being burned in an efficient power cycle based

on gas turbines, such as the steam injected gas turbine (STIG), intercooled STIG (ISTIG), or a combined cycle.2

Hot gas cleanup avoids cost and efficiency penalties, and pressurized gasification avoids energy losses

associated with compressing the fuel gas after gasification. It is necessary, however, to remove trace amounts

of alkali vapor from the gas before it enters the gas turbine. There appears to be a basic understanding of the

means for adequately cleaning gases for gas turbine applications with either fluidized bed gasifiers3 or updraft

gasifiers, although there has been no commercial demonstration of alkali removal. A demonstration 6 MWe

pressurized fluidized bed plant, however, has recently gone on line in Sweden.

Biomass gasifier/gasturbines (BIG/GTs) are characterized by high conversion efficiencies and low expected

unit capital costs ($/kW) in the 5 to 100 MWe size range.4 The upper end of this range is probably near the

f Typical rates of biomass fuel production, or use at individual sites, range up to a maximum of some 300 to 400 MMU*

&4 to 72 dry tonnes per hour) at large factories that produce biomass as a byproduct and use it for energy (e.g., cane sugar

and kraft pulp factories). This can be compared with the 800 to 4,000 MW of coal consumed at central station eiectric power

plants. Lar~ercon@ntrationsof biomass could be made available, e.g., from plantations dedicated to producing biomass for

energy. Under such schemes, transportation costs and land availability wiil be limiting factors on the quantity of biomass that

can be concentrated at a single site.

2 s~9 E,D, Larson and FI.H, Wiiiiams, ‘steam-injected Gas Turbines,” ASMEJournfd Of Engin@@rlng for Ga$ T@fnes

and Power, vol. 109, 1987, pp. 55-83; R.i-i. Wiiliams and E.D. Larson, “Expanding Roles for Gas Turbines h Power

Generation: Electricity: Efficient End Use and New Generation Technologies, and Their P!anning /mplicatlons (Lund,

Sweden: Lund University Press, 1989), pp. 503-53; R.H. Wiiiiarns and E.D. Larson, “Thermochemical Biomass Gasifier/Gas

Turbine Power Generation and Cogeneratiom” Thomas B. Johansson, Henry Kelly, Amulya K.N. Reddy, and Robart H.

WMiams (s@,), Renewable Energy.- Sources for Fuels and Elect~ciW(Washlngton, DC: island press, 1993).

a E. Kwluda, P. Stahiberg, M. Nieminen, and J. Laatikainen, “Removai of Particulate, Aikafi, and Trace Metals from

Pressurized Fluid-Bed Biomass Gasification Products-Gas Cieanup for Gas Turbine Applications,” in Donald L. Klass,

Bkwr?ass and Wastes XV{Chicago, iL: institute of Gas Technology, 1991).

4 see E.D, Larson and R,H. Wiiliams, ‘Biomass-Gasifier/Steam4njected Gas Turbine Cog@nOratiOn,” Jouma/ of En$7irk?ering for Gas Turbines and Power, vol. 112, April 1990, pp. 157-63; P. Eiiiott and R. Booth, “Sustainable Biomass Energy:

Sslectad Paper (London, England: Sheil International Petroleum Co., Ltd., December 1990).
 .

12 I Bioenergy

practical upper limit on the size of a biomass installation. Capita} costa for gasification and gas cleanup may

be lower for biomass than for coal due to the lower operating temperatures and greater volatility of biomass.

Transport Fuels. Biomass-derived fuels-methanol, ethanol, biodiesel, and possibly hydrogen--offer an

important opportunity to reduce U.S. fossil fuel consumption transport. Of particular interest here are ethanol

and methanol

Ethanol. Much of the attention and funding of biomass fuels has been focused on grain-to-ethanol

production. In the United States, commercial operations annually produce about 850 million gallons of ethanol

from corn by fermentation. This ethanol is blended in a typically 1 to 9 ratio with about 8 percent of U.S. gasoline

as an octane enhancer. (Alternatively, minor engine modifications allow ethanol to be used as a full replacement

for gasoline.) This production is supported by tax incentives arid low prices for alternative uses of the corn crop.

Expansion of supplies sufficient to significantly reduce US. oil imports, however, is not realistic if limited to the

use of grain; nor would it be economical.

Ethanol’s environmental benefits include: a reduction of carbon monoxide when used in blends; possible

reductions in urban ozone;5 and, if produced from biomass on a renewable basis, no or low net contributions

of the greenhouse gas carbon dioxide to the atmosphere.

Advanced bioengineering and other technologies are now enabling researchers at the National Renewable

Energy Laboratory (NREL), Tennessee Valley Authority, and elsewhere to convert cellulosic feedstocks (e.g.,

the corn stalk, not just the grain) to ethanol. This greatly increases the potential volume of feedstock that could

be converted to ethanol and reduces its cost. Although substantial technical hurdles remain, particularly

scale-up of laboratory processes, researchers hope to lower the cost of ethanol to competitive levels with

gasoline by the year 2000.

Woody and herbaceous biomass, referred to generally as Iignocellulosic materials, consist of three

chemically distinct components: cellulose (about 50 percent), hemicellulose (25 percent), and Iignin (25 percent).6 Most proposed ethanol production processes involve separate processing of these components. in the

first step, pretreatment, the hemicellulose is broken down by acids or enzymes into its component sugars and

separated out.7 The Iignin is also removed. The remaining cellulose is then converted into fermentable glucose

through hydrolysis, Following fermentation, the products are distilled to remove the ethanol. Byproducts of the

separation process, such as furfural and Iignin, can be used as fuel or sold separately.

Methanol, Methanol is a liquid fuel that can be produced from natural gas, coal, or biomass via gasification

and catalysis. Methanol does require somewhat greater fuel-system material modifications than ethanol, but

flexible-fueled vehicles, which can operate on methanol, ethanol, gasoline, or a mixture of these fuels, are

already being produced in limited numbers in the United States.8 The use of such vehicles could ease the

transition away from gasoline.

Biomass-to-methanol plants would typically convert 50 to 60 percent of the energy content of the input

biomass into methanol, though some designs have been proposed with somewhat higher conversion efficiencies. Three basic thermochemical processes are involved in methanol production from biomass:9

s US. Congress, Office of Technology Assessment, R8p/aclng Gam//nff;#femative /%els/orL@hf-Duty Vehicles, p. 108.

6 J,D. Wdght, ‘Ethanol from Lignocellulose: An overview,’” /%ergY ~fO~teSS, vOl. 8, No. 2, 1988, PP. 71-78.

7 ~.E. Wyman, N.D. tiinman, and R.L. Bain, “Ethanol and Methanol from Cellulosic Materials,” Thomas B. Johansson,

Henry Keliy, Amuiya K.N. Reddy, and Robert H. Wtlliams (eds.), Renewable Energy; Sources for Fue/s and Electricity

(Washington, DC: island Press, 1993); P.W. Bergeron, J.5. Wright, and C.E, Wyman, “Diiute Acid Hydrolysis of Biomass

for Ethanol Production,” Energy from Biomass and Wastes X//(Chicago, IL: lnstitutefor(3as Technology, 1989), pp. 1277-96;

M.M. Bulls, J.R. Watson, R.O. Lambert, J.W. Barrier, “Conversion of Ceiiulosic Feedstocks to Ethanol and Other Chemicals

Using TVA’s Dilute Sulfuric Acid Hydrolysis Process; Energy from Biomass and Wastes XIV (London, England: Elsevier

Appiied Science, 1991).

% U.S. Congress, Office of Technology Assessment, Replacing Gasoline, OTA-E=364 (Washington, DC: U.S. Government

Printing Office, September 1990), p, 25.

9 C.E. Wyman, N.D. Hinman, and R.L. Bain, “Ethanoi and Methanol from Celiulosic Materials,” in Thomas B. Johan=m,

Henry Kelly, Amuiya K.N. Reddy, and Robert H. Williams (sds.)$ ffer18wab/e Energy; Soumes for Fue/s and EYectricify,

(Washington DC: Island Press, 1993).
Chapter 2–introduction 113

• Production of a “synthesis gas” (a close relative of producer gas) via thermochemical gasification, but

using oxygen rather than air in order to eliminate dilution of the product gas with nitrogen (in air). Oxygen

plants have strong capital cost scale economies, which contributes to most proposed biomass-to-methanol facilities being relatively large (typically 2,000 tonnes/day or more input of dry biomass). Biomass

gasifiers designed for methanol production are not commercially available but research and pilot

demonstrations are in planning or underway.10

● The synthesis gas is cleaned and its chemical composition is adjusted to produce a gas consisting purely

of hydrogen (H2

) and carbon monoxide (CO) in a molar ratio of 2:1. The specific equipment configuration

in the second step in methanol production will vary depending on the gasifier used, A reactor common

to all systems is a “shift”; reactor used to achieve the desired 2:1 ratio of H2 to CO by reacting steam

with the synthesis gas. The shift reactor is a commercially established technology.

. •The gas is compressed and passed through a pressurized catalytic reactor that converts the CO and

H2 into liquid methanol. A variety of commercial processes can be used.

Tests of methanol’s potential to reduce air pollution have yielded mixed results.11 Potential greenhouse

gas benefits of methanol depend on the feedstock: renewably produced biomass feedstocks would make little

or no net contribution to greenhouse gas emissions; fossil fuel feedstocks would increase them for coal and

decrease them for natural gas. Methanol does have some environmental disadvantages, particularly greater

emissions of formaldehyde, which could require special emission controls. Today’s production vehicles,

however, are certified as meeting California’s formaldehyde emissions standards.12

10&3@ A,A.C.M. ~enackers and w.p.td. van Swaaij, “The Biomass to Synthesis Gas pkd plant p~09ramme of the CEC:

A First Evaluation of Results,” Energy from Biomass, 3rd EC Conference (Essex, United Kingdom: Elsevier Applied Science,

1985), pp. 120-45; E. C), Larson, P. Svenningsson, and L Bjerie, “Biomass Gasification for Gas Turbine Power Generation,”

Electricity: Efficient End-Use and New Generation Technologies, and their Planning Implications (Lund, Sweden: Lund

University Press, 1989), pp. 697-739; R.J. Evans, B.A. Knight, et al., Devekpnent of Biomass Gasification to Produce

Substitute I%@, PNL-6518 (Richland, WA: Battelle Pacific Northwest Laboratory, 1988); Chem Systems, “Assessment of

Cost of Production of Methanol from Biomass,” draft (Goiden, CO: Solar Energy Research Institute, December 1989).

11 U.S. Congress, Office of Technology Assessment, Replacing Gasoline, OTA-E-384 (Washington, DC: U.S. Government Printing Office, September 1990).

la Robe~ Nichols, Ford Motor Company, J) WSOflEd communication, Sept. 1, 1993.

dues would be about 25 GJ/tp. Combined, these much as 4000 kWh of electricity per ton of pulp

energy resources total some 41 GJ/tp.12 produced if all of the hog fuel, black liquor, and

Most kraft pulp mills current] y use black liquor recoverable forest residues were used. After meetfor cogenerating steam and electricity onsite. ing onsite needs,

13 this would leave a substantial

High-efficiency steam-injected gas turbines, com- amount of power—worth nearly half the value of

bined cycles, or other high-performance genera- the pulp-that could be sold to the grid.14

tion technologies might be able to generate as

12 Eric D ~~on,*’prosFcts for BiomaSs.Gasifier Gas Turbine Cogeneration in the Forest Products Industry: A ScoPing StudY!” Center

for Energy and Environmental Studies Working Paper No. 113, (Princeton, NJ: Princeton University, February 1990).

13 onsite needs today me typica]]y about 740 kwh/tp of electricity plus some 4,300 kg/tp Of Steam, with the Potential for significant

reductions.

14 Assuming $0.07/kWh, See: Eric D. Mson, “Biomass-Gasifier/Gas-Turbine Applications in the Pulp and Paper Industry: An Initial

Strategy for Reducing Electric Utility C02 Emissions,” Conference on Biomass For Utility Applications, Electric Power Research Institute,

Tampa, FL, Oct. 23–25, 1990; Eric D. Larson, “Prospects for Biomass-Gmifier Gas Turbine Cogeneration in the Forest Products Industry: A

Scoping Study,” Center for Energy and Environmental Studies Working Paper No. 113, (Princeton, NJ: Princeton University, February 1990).
14 I Bioenergy

The Residential Sector

The residential/commercial sector accounts for

about one-fifth of total primary energy use, with

electricity and natural gas the primary fuels used.

Wood fills roughly 10 percent of the space heating

requirements, or roughly 5 percent of the total

energy used in the residential sector. 15 Prospects

for substantially increasing wood use in this sector

are not promising because of the relatively high

level of emissions generated by small household

wood stoves, and the difficult and expensive logistics of delivering wood fuels to highly dispersed

small users.

Impacts of U.S. Energy Demand

Patterns and Bioenergy

Current U.S. energy demand patterns affect the

economy, national security, and the environment

(see ch. 3). Bioenergy could reduce these impacts,

but by itself cannot eliminate them. Its relative

value in meeting these needs will have to be compared with other potential uses for the land, alternative fuels and technologies, and other

approaches.

U.S. expenditures on foreign oil are currently

running about $50 billion per year and are destined

to increase sharply as U.S. oil production continues its decline. Several U.S. electric utilities are

also now importing low sulfur coalo

]6

The economic impacts of these imports are hard

to assess as they depend on: the manner in which

these petrodollars are recycled back into the U.S.

economy; changes in the terms of trade; employment in U.S. export industries; and other factors .17

These economic impacts are also spread unevenly

within the United States.

The ready availability of cost-effective and

high-performance alternative fuels and technoloFigure 2-4-Energy Sources Used by the Wood

and Paper Products industries

Paper products industries

Woodwaste

21 Fuel oil

Spent Iiql

38

Coal

3

Wood products industries

LPG

1 Fuel oil

“--’’J” atU:’gas

This figure shows the extensive use of biomass fuels—woodwaste and

spent liquor—in the wood and paper products industries. Of total enduse energy consumed, 60 to 75 percent is provided by biomass.

SOURCE: Energy Information Administration, Estimates of U.S. Biofue/s Consumption 1989, U.S. Department of Energy, April 1991.

IS u s Department of Energy, Energy Information Administration, . . “Estimates of U.S. Biofuels Consumption 1989,” Report

No. SWCNEAR-91-02, Washington, DC, April 1991.

16 Jane Tumbu]], Electric power Research Institute, personal communication, Sept. 1! ‘99~.

17 H.GO Broadman, “The social Cost of IrnWrted Oil,” Energy Policy, vol. 14, 1986, pp. 242–52; H.G. Broadrnan md W.W. Hogan. “IS An

Oil Tariff Justified? An American Debate: The Numbers Say Yes,” Energy Journal, vol. 9, No. 3, 1988, pp. 7–29; M. Ethridge, “The Social

Costs of Incremental Oil Imports: A Survey and Critique of Present Estimates,” Discussion Paper #25, American Petroleum Institute,

Washington, DC, February 1982; Daniel Sperling and Mark A. DeLuchi, “Transportation Energy Futures,” Annual Review @Energy, vol. 14,

1989, pp. 375-424.
Chapter 2–introduction 115

gies could help reduce oil price volatility, oil price

increases, and oil import costs. In addition, they

would reduce the uncertainty and risk associated

with price volatility and thus might help reduce the

corresponding distortion of investment decisions

toward the short term. Fuels derived from biomass

feedstocks might provide some of these alternatives.

Reliance on imported oil also poses national

security risks. These can be quickly enumerated

but defy quantification. Such risks include: future

involvement in Middle East or other conflicts;

possible pressure on U.S. alliances; economic impacts due to a sudden oil curtailment; and many

others. The likelihood and severity of these impacts will depend on the extent to which potential

anti-Western factions might gain control of key

oil-exporting countries and exercise this power,

the discovery and development of oil resources

outside the Middle East, improvements in secondary oil recovery from existing fields, and the

development of alternative transport fuels and

technologies. 18

THE RURAL ECONOMY AND BIOENERGY19

Rural economies in the United States have been

hard pressed for many years. Between about 1980

and 1990, the U.S. share of the world’s total agricultural trade dropped from 28 to 21 percent. At

the same time, the European share grew from

about 13 to 19 percent. China is now the world’s

second largest corn exporter and Brazil is a major

exporter of soybeans. Roughly half of the shiploading grain terminals in the United States are

reportedly closed, about to close, or for sale.20 Due

to these pressures, there is a growing need to find

alternative crops for rural agricultural communities: to provide employment, to stabilize rural

incomes, and to maintain the rural infrastructure

of equipment and supplies distribution and service. Bioenergy crops might serve such a role if

mechanisms can be found to overcome a variety

of market and institutional obstacles to their use.

The rural economy faces several trends; bioenergy may be able to moderate some of their impacts. Demand for conventional agricultural

products is likely to grow slowly: U.S. population

growth is low2] and the U.S. consumer is reasonably well fed. At the same time, foreign demand

is uncertain.

22 It may be met in the future by new

export powerhouses, particularly eastern Europe

and the former Soviet Union, Latin America, and

elsewhere .

23 Efforts in those regions will be

strongly aided by adoption of the modem agricultural techniques and crop varieties pioneered by

the United States; thus, U.S. farmers are not

18 U.S. Congress, Office of Technology Assessment, U.S. Vulnerability to an Oil Import Curtailment: The oil Replacement capabiW~

OTA-E-243 (Wmhington, DC: U.S. Government Printing Office, September 1984); U.S. Congress, Office of Technology Assessment, U.S.

Vulnerability to an Oil Import Curtailment: The Technical Replacement Capability, OTA-E-503 (Washington, DC: U.S. Government Printing

Office, Octotxr 1991).

19 For broader reviews of the economic impacts of bioenergy crops, see Southemtem Regional Biom&~s Energy program? Tenness~ ValleY

Authority and Meridian Corporation, “Economic Jmpact of Industrial Wood Energy Use in the Southeast Region of the U.S.,” four volumes,

Muscle Shoals, AL, and Alexandria, VA, November 1990; J.W. Onstad, M.S. Lambrides, B.S. McKenna, “Analysis of the Financial and

Investment Requirements for the Scale-Up of Biomass Energy Crops,” National Renewable Energy Laboratory and Meridian Corporation,

Alexandria, VA, September 1992; Ed Wood and Jack Whittier, “Biofuels and Job Creation: Keeping Energy Expenditures Local Can Have

Very Positive Economic impacts,” Biologue, vol. 10, No. 3, September/December 1992, pp. 6-11; Meridian Corporation and Antares Group

Inc., “Economic Benefits of Biomass Power Production in the U.S.,” Biologue, vol. 10, No. 3, September/December 1992, pp. 12-18; R.L.

Graham, B.C. English, R.R. Alexander, M.G. Bhat, “Biomass Fuel Costs Predicted for Eaw Tennessee Power Plant,” Bio/ogue, vol. 10, No. 3,

September/December 1992, pp. 23–29; “Electricity from Biomaw: A Development Strategy,” Solar Thermal and Biomass Power Division,

Office of Solar Energy Conversion, U.S. Department of Energy, DOIYCH1OO93-152, April 1992.

ZO Scott Kilman, “u.s. 15 Steadily Losing Share of World Trade in Grain ~d soy beans,” Wall Street Journal, Dec. 3, 1992, p. Al.

21 U.S. ~pulation growth is one of the highest of the industrial countries, however.

22 In the longer term, Population growth in developing countries may surpass agricultural productivity growth and incre~~e dem~d for food

imports. Some of this demand may be supplied by the United States. No one knows, however, what the net effect is likely to be.

23 Of Courqe thiq will require heavy investment to develop the needed infrastructure of farming equipment, roads, storage facilities, ~d ., .

shipping terminals. Such investment capital is now very limited in these countries.
16 I Bioenergy

assured of a continuing comparative advantage, at

least not of the magnitude they have enjoyed in the

past.

The trend to farming as an agribusiness is likely

to continue as well. This will be an inevitable

result of the need to maintain some competitive

advantage, and will require increased use of modem chemistry, biology, computer, and telecommunication technologies, creating a production

unit with sophisticated stocks and flows of goods

and services.24

Environmental considerations are likely to play

an increasing role in farming practice as well.

Indirectly, increasing attention to environmental

considerations on public lands may push fiber and

other production activities toward private and

marginal lands. At the same time, increasing attention to environmental issues on private lands may

also have an impact on cropping practices,

Energy crops may provide alternative sources

of income and help diversify risk for the farmer.

Energy crops have the potential to redirect large

financial flows from foreign oil or other fossil

energy resources to the rural economy, while simultaneously reducing Federal agricultural expenditures. Realizing this potential, however, will

require further development of economically and

environmentally sound energy crops, their successful commercialization, and carefully crafted

policies to make the transition to energy crops

without injuring the farm sector or exposing it to

undue risk. It will also depend on the relative value

of other uses of this land and the costs and benefits

of other fuels and technologies.

Federal agricultural expenditures play a noted

role in the rural economy. The Federal budget is

under great pressure, however, and agricultural

programs—like everything else—are under increased scrutiny for savings. Currently, Federal

programs to prevent soil erosion (see box 2-B)

and various commodity support programs to

strengthen crop prices together cost roughly $10

Box 2-B-Conservation Compliance Programs

Conservation compliance was enacted under the 1985 Food Security Act, as amended in 1990, in which

all farmers cultivating highly erodible land must fully implement an approved conservation plan by 1995 or risk

losing certain farm benefit programs. At the same time, the Conservation Reserve Program (CRP) pays farmers

with highly erodible or otherwise environmentally fragile or sensitive land to take it out of production under

10-year contracts. At present, some 15 million hectares are enrolled in CRP, with annual payments averaging

roughly $110 per hectare. At the end of the contract, land that is highly erodible must meet conservation

compliance conditions.

Failure to comply with the conservation plan results in the potential loss of a variety of benefits, including:

eligibility for price supports and related programs; farm storage facility loans; crop insurance; disaster payments;

storage payments; any Farmers Home Administration loans that will contribute to erosion on highly erodible

lands; and several other types of assistance.

Conservation compliance affects some 55 million hectares, more than one-third of U.S. cropland. A key

aspect of about three-quarters of the conservation compliance plans to date is the use of agricultural residues

to control erosion. Use of such residues for energy may then conflict with soil erosion concerns (see ch. 3).

For more information, see Jeffrey A. Zinn, “Conservation Compliance: Status and Issues,” Congressional

Research Service, 93-252 ENR, Feb. 24, 1993.

24 u s . .Congress, Office of Technology Assessment, A New Technological Erujor Americun Agriculture, OTA-F-474 (Washington, Dc:

U.S. Government Printing Office, August 1992); William E. Easterling, “Adapting United States Agriculture to Climate Change,” contractor

report prepared for the Office of Technology Assessment, February 1992.
Chapter 2–introduction 117

billion per year. Bioenergy crops are a potential

alternative cash crop that could protect fragile

soils or could be grown on lands previously idled

in order to strengthen commodity crop prices.

Earnings from the energy crop might then allow

Federal supports to be eased while maintaining

farm income. Of course, the relative environmental benefits of energy crops versus current soil

conservation programs such as the Conservation

Reserve Program would again depend on the specific energy crops grown and how the land was

managed. The relative economic and budgetary

value of producing bioenergy crops would have to

be compared with potential alternative uses of the

land. Designing Federal programs to achieve such

ends while minimizing disruption and risk to farmers also presents challenges.

BIOENERGY RESOURCES

Biofuels currently provide about 3 EJ, or 4 percent

of U.S. primary energy. Some researchers estimate that biofuels have the potential to provide

15 EJ of energy annually by 2010 and perhaps

25 EJ by 2030.25 Recent detailed econometric

studies estimate that the agricultural sector could

support the production of roughly 10 EJ of delivered ethanol from cellulosic biomass (not from

grain, sugar cane, etc.) by the year 2030 with net

benefits to the agricultural economy. 26 Projections

based on a business-as-usual estimate nonliquid

biomass fuels will provide 4-8 EJ in 2030.27 These

projections will not be critiqued here. Instead, the

focus of this report is to examine the environmental implications if such large land areas are

converted to energy crops.

Three sets of biomass resources could be used:

municipal solid wastes (MSW); agricultural and

forestry residues; and bioenergy crops. Each of

these resources has unique characteristics and considerations, and differing quantities of material

available at a particular price.

Municipal Solid Wastes

Generation of heat or electricity from MSW can

be technically difficult under some circumstances

due to the variety of materials handled and the

need to control emissions of the numerous toxic

trace materials found in MSW. Nevertheless, more

than 70 waste-to-energy plants are in operation or

under construction and roughly 50 are in an advanced stage of planning. By one estimate, U.S.

MSW could provide the energy equivalent of more

than 10 GW on a continuous basis. 28 Recycling,

the slow economy, and other factors, however,

have reduced the availability of MSW for some

incinerators, increasing costs above those originally projected.

29 In other areas, landfills are filling rapidly yet new sites are controversial, making

the prospects for use of MSW brighter.30 MSW is

not considered further in this report.

25 J 

. . w R~ney and J.H. CUshrnan, “Energy from Biomm “ Ruth Howes and Anthony Fainberg (eds.), The Energy Sourcebook: A Guide

ZO Technology, Resources, and Policy, (New York, NY: American Institute of Physics, 1991); another set of estimates is given in Solar Energy

Research Institute et al., The Potential of Renewable Ener#y: An In(erlaboratory White Paper, SERUTP-260-3674, March 1990 (now known

as the National Renewable Energy Laboratory).

z~ Randa]l A. Reese, Sa(heesh V. Aradhyula, Jason F. Shogren, and K. Shaine Tyson, “Herbaceous Biomass Feedstock Production: The

Economic Potential and Impacts on U.S. Agriculture,” Energy Policy, July 1993, pp. 726-734,

27 Resource Modeling and Technology &onomics Group, “Projections of Wood Energy Use In the United States” (Oak Ridge, TN: Oak

Ridge National Laboratory, July 2, 1990, draft).

28 R.E. Barrett et al., “Municipal Waste-To-Energy Technology Assessment,” EPRI TR-1OOO58 (Palo Alto, CA: Electric Power Research

Institute, January 1992).

29 Jeff Bailey, “Fading Garbage crisis haves Incinerators Competing for Trash,” Wall Street Journal, Aug. 1 I, 1993, p. Al; and Jeff Bailey*

“Poor Economics and Trash Shortage Force Incineration Industry Changes,” Wdl Street Journal, Aug. 11, 1993, p. A2.

30 see for example, u s congress, Office of Technology Assessment, Facing Ameri(.a ‘.Y Trash: w~t Nextf<)r Municipal Solid Waste? . .

OTA-O-4~4 (Washington, DC: U,S. Government Printing Office, October 1989); R.E, Barrett et al,, “Municipal Waste-To-Energy Technology

Assessment,” EPR1 TR-1OOO58 (Palo Alto, CA: Electric Power Research Institute, January 1992); D. Longwell et al., “Waste-to-Energy

Permitting Sourcebook,” EPR1 TR-1OO7I6 (Palo Alto, CA: Electric Power Research Institute, October 1992); Marjorie J. Clarke, Maarten de

Kadt, and David Saphire, “Burning Garbage in the U. S.: Practice vs. State of the Art” (New York, NY: INFORM, Inc., 1991).
18 I Bioenergy

Agricultural and Forestry Residues

As with MSW, agricultural and forestry residues can often be obtained at low or no cost: they

may have already been trucked to a central processing site such as a sugar mill or sawmill and are

available in large quantities. Burning them onsite

usually costs less than hauling them away for

disposal. More of this resource might be collected

and used for energy production,31 and more efficient energy conversion systems could be used.

Residues are an important part of the forest ecosystem, however, and must be carefully guarded

from overuse or misuse (see chapter 3).32

Energy Crops

Energy crops can be divided into three broad

categories: annual row crops such as corn, herbaceous perennial grasses (herbaceous energy

crops—HECs) such as switchgrass, and short-rotation woody crops (SRWCs) such as poplar.

Annual row (energy) crops are grown in essentially the same manner as their food crop

counterparts and consequently offer few or no

environmental benefits over conventional agricultural practices. Because of this, annual row crops

are not examined further in this report.

Crops (often annual row crops) have also been

used to produce starches, sugars, oils, and other

specialty plant products as energy feedstocks. On

a national basis, however, their energy production

potential is much lower and their costs higher than

for cellulosic bioenergy crops (HECs and

SRWCs). Consequently, they are not considered

further in this report either.

HECs are analogous to growing hay, harvesting

the crop instead for energy. SRWCs typically consist of plantations of closely spaced (2 to 3 meters

apart on a grid) trees that are harvested on a cycle

of 3–10 years. Following harvest, HECs regrow

from the remaining stubble and SRWCs regrow

from the remaining stumps. Such harvests may

continue for 15 to 20 years or more without replanting (fertilizer and other inputs, and maintenance may be required annually, however).

These crops can be planted in a variety of

configurations with each other and with agricultural crops to maximize their economic and environmental benefits. Five key variables govern the

viability of woody and herbaceous energy crops:

technical feasibility; availability of suitable land;

economic viability; implementation; and environmental impacts. The first three are described

briefly below and implementation issues are described briefly in ch. 4. The potential environmental impacts are examined in detail in ch. 3.

Technical Feasibility

Research and development on plant species and

methods of planting have greatly enhanced the

technical feasibility of energy cropping. One of the

most important technical characteristics of energy

crops is their ability to perform well in varying

environments. Some energy crops, such as switchgrass and sweetgum, are no more site-specific than

a conventional agricultural crop such as corn. Others can be extremely site-specific if very high

yields are to be realized. In some cases, species

that respond well under research conditions may

not do well under actual site conditions during

operational trials.ss

31 It may a]so ~ possible to increase forest productivity, allowing additional biomass to be extracted, For example, modest applications of

nitrogen and phosphorus increased incremental growth severalfold in Scandinavian forests. See, for example, Sune Linder, “The Relationship

Between Nutrition and Biomass Production in Swedish Coniferous Stands,” Department of Ecology and Environmental Research, Swedish

University of Agricultural Sciences, Uppsala, Sweden, no date.

~z MoR intensive use of forests for energy may be controversial, however, and use of public lands for biomass energY suPPIY could ~

strongly opposed by the environmental community. James H. Cook, National Audubon Society, personal communication, Aug. 26, 1993.

33 A num~r of factors contribute to this change in response. The new site may be substantially different than the test plot, and conditions

may vary across the site itself. These include differences with respect to soil quality, the availability of nutrients and moisture, the presence of

weed competitors or of pests and disease, and others. This ha.. implications for the selection of plants, the management of stands, the was

planted, and the regional distribution of plantings. Jack Ranney, Oak Ridge National Laboratory, personal communication, Sept. 1, 1993.
Chapter 2–introduction 119

Other desirable characteristics of cellulosic energy crops include fast growth; efficient use of

nutrients and water; high density (of wood—high

heat value per unit of volume); robustness (ability

to withstand weather, pests, and disease); nitrogen-fixing capability (a trait that reduces the need

for fertilizer); and good potential for regrowth

from stubble (HECs) or stumps (SRWCs). Since

the 1970s the USDOE and USDA Forest Service

have supported research and development of

SRWCs that incorporate most of these features.34

Bioengineering eventually may further improve energy crops, such as by increasing productivity or reducing vulnerability to pests and

environmental stress. Desirable characteristics,

such as nitrogen fixation and fast growth,also may

be enhanced through bioengineering. Bioengineering technologies that have proven successful

in some cases are cloning and hybridization.35 For

example, USDOE supported research has produced hybrid black cottonwoods that have yields

that exceed those of the parent stock by a factor of

1.5 to 2.36 Genetic engineering of trees is a relatively new field compared with agricultural

biotechnology. Technology transfer from agriculture will speed SRWCs genetic engineering, but

only to a point; trees and shrubs have unique

characteristics, including long generation times.

Nonetheless, the potential to increase yields

through biotechnology is enormous—according

to one researcher, even more significant than the

successes already achieved in agricultural genetic

engineering. 37

Suitable trials and controls, however, will be

needed to ensure that these engineered cultivars do

not injure people, animals, or plants directly or

injure them indirectly by becoming a weed to

agriculture or more invasive of natural habitats

than unmodified cultivars. They must also not

transfer their genes (e.g., via pollination) to wild

relatives whose offspring might become more injurious, weedy, or invasive. Current USDA guidelines require evidence38 that transgenic crops pose

no greater risk to the environment than unmodified

plants from which they were derived.39

Availability of Suitable Land

To be reliable and substantial sources of energy,

energy crops will require significant amounts of

land.40 Estimates of the area available for growing

energy crops in the United States vary widely,

depending on the underlying assumptions about

the types of land to be considered, possible alternative uses for the land, the likely demand for food

or other exports, the projected increases in agricultural productivity, economic constraints, environmental constraints, the time frame considered,

and many others. Estimated areas potentially

available for energy cropping range from

roughly 15 to 100 million hectares.41 At yields

34 David Dawson, Forest policy Consultant, personal communication, Aug. 18, 1993.

35 ~win H. White et al., “Bioenergy Plantations in Northeastern North America,” paper presented at the Conference Energy from Biomass

and Wastes XV, Washington, DC, Mar. 25, 1991, p. 10.

~~ philip A, Abelson, “Improved Yields of Biomass,” .!i’cience, vol. 252, No. 5012, June 14, 1991, p. 1469.

ST EdWWd A. Hansen, “sRIC Yie]dS: A Look to the Future,” Biomass and Bioenergy, vol. 1, 1991.

38 There is debate about how good the evidence is or should be.

39 Peter Kareiva, “Transgenic Plants on TriaI,” Mmme, VOL 363, June 17, 1993, pp. 580-581; M.J. Crawley et al., “Ecology of Transgenic

Oilseed Rape in Natural Habitats,” Ntiture, vol. 363, June 17, 1993, pp. 620423.

40 j Wmen Ranney et al., “Hardwood Energy crops: The Technology of Intensive CUIIUR,” Journal Of FOreStzY> Vol. 85* PP. 17–28.

41 K*K. Shaine Tyson, “Biomass Resource Potential of the United States,” National Renewable Energy Laboratory, October 1990, draft;

James L. Fasterly, “Overview of Biomass and Waste Fuel Resources,” Strategic Benefits of Biomass and Wa..te Fuels Conference, Washington,

DC, Mar. 30, 1993; W. Fulkerson et al., “Energy Technology R&D: What Could Make a Difference? Volume 2, Supply Technology,”

ORNL-6541/V2/P2 (Oak Ridge, TN: Oak Ridge National Laboratory, December 1989); D.O. Hail, H.E. Mynick, and R.H. Williams,

“Alternative Roles for Biomass in Coping with Greenhouse Warming,” Science und GlobalSecurity, vol. 2,1991, pp. 113-151; James H. Cook,

Jan Beyea, Kathleen H. Keeler, “Potential Impacts of Biomass Production in the United States on Biological Diversity,” Annual Review of

Energy and Environment, vol. 16, pp. 401-431, 1991; Thomas B. Johansson, Henry Kelly, Amulya K.N. Reddy, Robert H. Williams (eds.),

Renewuble Ener~y: Sources for Fuels and Electricity (Washington, DC: Island Press, 1993).
20 I Bioenergy

of 15–20 tonnes/ha, roughly 8 EJ or 10 percent of

current U.S. energy demand could be produced on

30 million ha. Some studies estimate the total

bioenergy potential as 15 EJ annually by 2010 and

perhaps 25 EJ by 2030.@ Recent econometric

studies estimate that the agricultural sector could

support the production of roughly 10 EJ of delivered ethanol from cellulosic biomass (not from

grain, sugar cane, etc.) by the year 2030 with net

benefits to the agricultural economy.43 Projections

based on business-as-usual estimate nonliquid

biomass fuels will provide 4-8 EJ in 2030.44

These estimates of perhaps 8–25 EJ of bioenergy are roughly 10-30 percent of current U.S.

energy use of 85 EJ-of which roughly 20 EJ each

is for coal in the power sector and for oil in the

transport sector. Thus, bioenergy crops can potentially contribute a significant fraction of U.S. energy needs.

To the extent that large areas of land are cultivated for energy crops, however, concerns are

raised about the potential environmental impacts

on soil quality and erosion, water use, agricultural

chemical use, and habitat. These are explored in

the following chapter.

Economic viability

Overall, agricultural residues and wood wastes

are available in limited supplies for roughly $0.50-

$1.50/GJ. 45 Gathering additional residues would

raise these costs. The best energy crop sites can

now produce perhaps 15-20 tonnes/year at costs

in the range of $2 to $4 per GJ.46 Conversion of

these biomass feedstocks to useful fuels raises

these costs. In comparison, crude oil at $20 per

barrel is equivalent to $3.30/GJ; coal at the current

price to electric utilities of roughly $30/ton is

equivalent to roughly $1 .50/GJ.47

Even if they are not strictly cost effective compared with fossil fuels, energy crops may still be

desirable if other benefits-such as environmental

advantages, offsets of oil imports, or financial

returns to the rural economy—justify the costs.

CLOSE

Concern over the environmental impacts of fossil

fuel use, the rural economy, oil import bills and

national security, Federal budget deficits, and

other factors have prompted many to take a second

look at biomass as an energy resource. Although

some initially proposed that biomass be used to

store (sequester) carbon released by the burning of

fossil fuels; more recently many groups have explored the potential of biomass to substitute for

fossil fuels.48 Technological advances in biomass

growth, harvesting, transport, and combustion are

lowering costs to where plantation-grown biomass

42 J-w. Ranney and J.H. Cushman, “Energy from Biomaw,” Ruth Howes and Anthony Fainberg (eds.), The Energy Sourcebook: A Guide

10 Technology, Resources, and Policy, (New York, NY: American Institute of Physics, 1991). Another set of estimates is given in Solar Energy

Research Institute et al., The Potentiul t)f Renewable Energy: An lnterklboratofy White Paper, SERlJTP-260-3674, March 1990; see also the

references listed in footnote no. 43.

@ Randall A. Reese, Satheesh V. Aradhyula, Jason F. Shogren, and K. Shaine Tyson, “Herbaceous Biomass Feedstock Production: The

Economic Potential and Impacts on U.S. Agriculture,” Energy P(dicy, July 1993, pp. 726-734.

44 Resource Modeling and Technology ~onomics Group, “Projections of Wood Energy Use 1n the United Stites” (Oak Ridge, ‘N: ‘*

Ridge National Laboratory, July 2, 1990, draft).

45 us. ~p~ment of Energy, “Elec~city from Biomass: A Development Strategy,” DOIYCHIO093-152, APril 1992.

~ J.W. Ranney and J.H. Cushman, “Energy From Biomass,” Ruth Howes and Anthony Fainberg (eds.), The Energy Sourcebook: A Guide

to Technology, Resources, and Policy (New York, NY: American Institute of Physics, 1991); U.S. Department of Energy, “Electricity from

Biomass: A Development Strategy,” DOIYCHIO093-152, April 1992.

47 U.S. ~p~mnt of Energy, Energy Information Administration, Annual Energy Review 1992, MNYEIA-0384(92), June 1993.

48 se, for exmple: solw Energy Resewch Institute et ~., The potential of Renewuble Energy: An Interlub~rutoq White paper,

SERVTP-260-3674, March 1990; Office of Conservation and Renewable Energy, U.S. Department of Energy, Renewable Energy Technology

Evolution Rationales, draft, Oct. 5, 1990; U.S. Environmental Protection Agency, Renewable Electric Generation: An Assessment of Air

Pollution Prevention Potential, EPA/400/R-92/005, March 1992; Thomas B. Johansson, Henry Kelly, Amulya K.N. Reddy, Robert H. Williams

(eds.), Renewable Energy: Sources f{]r Fuels and Electricity (Washington, DC: Island Press, 1993).
Chapter 2–introduction 121

efforts. 49 

may soon be competitive. As the potential scale of The potential environmental impacts of

use of biomass energy has become apparent, how- large-scale bioenergy production is the primary

ever, environmental concerns have been raised focus of the following chapter.

and have begun to be addressed through several

49 This includes: “Towwd biological Guidelines for Large-Scale Biomass Energy ~VdOpmen4° Report of a Workshop Convened by the

National Audubon Society and Princeton University, May 6, 1991; and the National Biofuels Roundtable, convened by the Electric Power

Research Institute and the National Audubon Society.
B

Potential

Environmental

Impacts 3

ioenergy crops may have a wide range of effects on

soils, water, air, habitat, and greenhouse gas emissions. The net effect will depend on the particular type

of energy crop and the previous use of the land, the

cultivation methods practiced, the overall effort to integrate the

crop with the regional landscape ecology, and other factors. The

positive environmental impacts of energy crops range from modest to significant compared with most conventional agricultural

crops under good management practice; the negative impacts are

generally less than those of conventional row crops under typical

management. Letting idled or reserve cropland revert back to

natural forest or prairie may in the longer term provide equal and

usually greater environmental benefits than energy cropping,

particularly in terms of habitat, but the risk of global warming and

consequent habitat loss may substantial] y offset these benefits and

encourage further consideration of energy crops.

Substituting energy crops (such as short-rotation woody crops

or herbaceous perennials like switchgrass) for conventional row

crops (such as corn or soybeans) will under proper management

generally improve soil quality, reduce soil erosion and runoff,

reduce the use of agricultural chemicals (fertilizers, pesticides,

herbicides, fungicides), improve local air quality, and improve

habitat for a variety of animals. On the other hand, substituting

energy crops for hay, pasture, or well-managed Conservation

Reserve Program Lands will generally have mixed impacts.

These projections of the potential environmental impacts of

energy crops are based primarily by analog with conventional

crops; there is as yet little data for actual energy crops in the field

and these data are usually for small field trials collected over short

periods rather than large-scale trials over long periods.

The risk of global

warming and

consequent habitat

loss may. . . encourage

further consideration

of energy crops.

23
24 I Bioenergy

Only current, idled, or former croplands, or

degraded lands are examined here for potential

conversion to energy crops; natural1 forest, prairie, and wetlands are not considered here as the

analysis is beyond the scope of this paper and the

potential habitat and other environmental impacts

are more likely to be substantially negative.

INTRODUCTION

A wide variety of energy crops is under development (figure 3-1 ). These include short-rotation

woody crops such as hybrid poplars, black locust,

silver maple, sweetgum, and eucalyptus; and herbaceous perennials such as switchgrass and reed

canary grass.

Energy crops can be considered to be a less

intensive form of agriculture. The energy crops

considered here are perennials (herbaceous perennial grasses or short-rotation woody crops) and

thus require less cultivation than conventional

crops. These energy crops also have the potential

to be more efficient in the use of fertilizers (i.e.,

there is some nutrient retention and cycling between growing years that does not occur with

annual crops). Overall, the inputs required by energy crops are generally less than for conventional

agriculture for several reasons. They often have

heavier and deeper rooting patterns, allowing the

soil to be utilized to a greater depth for water and

soil nutrients, and providing more time to intercept

fertilizers or other agricultural chemicals as they

migrate downward through the soil. This can also

give energy crops greater capacity to intercept

fertilizers or other agricultural chemicals in lateral

flows from adjacent areas. Heavier rooting puts

more carbon into the soil and so assists in creating

more productive soil conditions such as enabling

the slow continuous release of nutrients or the

binding of chemicals so that they are not leached.

Finally, energy crops are selected on the basis of

their production of cellulosic biomass, which consumes less input energy (light, etc.) per unit of

energy stored than for many specialty plant components.

Each of these crops will have different management regimens and differing impacts on soil,

water, air, and habitat quality. These issues will be

examined broadly here; detailed analysis of specific crop impacts are discussed in the literature.

Much more research, development, and dedicated

field trials are needed to understand the impacts of

these energy crops. Experience gained in Europe

and elsewhere in recent years may be useful in

helping address these issues.

SOIL QUALITY2

Soils are highly complex materials that require a

careful interplay of physical, chemical, and biological processes to support high-productivity

plant growth. Some of the more important qualities are described first, followed by a discussion

of the ways in which energy crops may affect

them.

By volume, soils typically consist of roughly

half mineral matter, 3 to 5 percent organic materials, and roughly one-quarter each of water and air

1 Defining “natural habitat” may be difficult and controversial because pmt decades—sometimes centuries+f clear cutting, selective

harvesting of economically valuable trees, and fire suppression have altered many U.S. forests, often leading to an incremed concentration of

plant species with lower economic or ecological value. Similar alterations have occurred over many other U.S. landscapes, including prairie

and wetlands. Although defining how much modification still qualifies as “natural” is thus challenging, the term will be used broadly here to

include all lands that suppoti a significant quantity and variety of indigenous plants and animals. For [his report, only current or former agricultural

lands, or highly degraded lands, are considered for energy crops.

2 See W. Lee Daniels and Jody N. Booze-Daniels, “Potential Effects of Agricultural Biomass Cropping Systems on Soil Quality,” contractor

report prepared for the Office of Technology Assessment, Apr. 28, 1993; W. Lee Daniels and Jody N. Booze-Daniels, “Biomass Cropping

Systems and Soil Erosion,” contractor report prepared for the Office of Technology Assessment, Apr. 28, 1993; Philip E. Pope, “Impacts of

Increased Use of Forest Resources on Soil Quality,” Office of Technology Assessment contractor report, May 13, 1993; Nyle C. Brady, The

Nature and Properties cf.$oils (New York, NY: Macmillan Publishing Company, 1984), 9th Ed. For a broader discussion of the future of soil

management, see: F.J. Pierce and R. La], “Soil Management in the 21st Century,” R. Lal and F.J. Pierce (eds.), Soil Managementfor Sustuinubility

(Ankeny, IA: Soil and Water Conservation Society).
Chapter 3–Potential Environmental Impacts 125

Figure 3-l—Potential Energy Crops and Regions Applicable in the United States

Hybrid poplars

,

/

Screening ongoing

/

I h \

k

)1 \r k Y

;.; .;

‘-d

4* *

.

● S

Eucalyptus

?

Black locust

Hybrid poplars

Silver maple

Switch grass

Reed canarygrass

This figure shows a limited set of potential energy crops and the regions within the United States where they might be grown. Many other species

might be considered as well, including alder, ash~-kenaf, mesquite, etc.

SOURCE: Oak Ridge National Laboratory.

in the pore space. These proportions change dramatically with geographic region and type of soil,

with soil depth (from more organic matter at the

surface to more rock and less pore space further

down), with how the soil is managed, and even

with the local weather—recent rains or drought

influence moisture and air (in pores) content.

Soils vary widely by the relative amounts of

clay, silt, and sand in them. In effect, this is a

classification of the relative amounts of different

sized particles in the soil. Clays are mineral particles of less than 0.002 mm diameter, silt particles

range from 0.002-0.05 mm in diameter, and sands

range from 0.05–2.0 mm (by the definition of the

USDA). These different sized particles provide

substantially different “feels” to the soil, from the

slick feel of wet clays to the coarse gritty feel of

sand. Size distribution strongly affects such factors as soil porosity and density, soil structure,

aggregation, strength, and other factors.

The particular minerals from which the soil is

formed also play a key role. Soils of the southeastern United States have high iron and/or aluminum

content, while Midwest soils contain a broad mix

of minerals. The particular mix of minerals in a

soil determines many of its properties.

Soil organic matter is typically a small percentage of the total soil mass but plays a critical role.

Organic matter is primarily responsible for making soils loose and porous—i.e., keeping mineral

particles from packing tightly together—and thus

aids aeration and penetration by water as well as
26 I Bioenergy

helping plant roots penetrate into the soil. Organic

matter increases the water-holding ability of the

soil; it is the major source of important mineral

elements for plant growth such as phosphorus,

sulfur, and nitrogen; and it also helps buffer soil

acidity/alkalinity. Biological organisms play a key

role in breaking down soil organic matter and

freeing nutrients from dead plant matter for use by

growing plants. Without constant replenishment

of organic matter, soils can quickly become depleted and barren.

Addition of organic matter to the soil comes

from either leaves, twigs, or other above-ground

residues, or it can come from the dieback of roots

with the seasons or with harvesting. The rate of

turnover of organic matter is determined by many

factors, including the type of organic matter,

whether it is plowed into the soil, the temperature

and moisture levels of the soil, the clay content of

the soil, the degree of aeration of the soil, and

others. Rates of organic turnover in the first year

can be nearly 50 percent of the initial weight; the

rate slows after the first year. Bioenergy crops

such as switchgrass and short-rotation woody

crops may substantially increase soil organic matter compared with conventional row crops, with

overall gains in productivity and soil quality.

Soil nutrients are also provided directly from

soil rocks and minerals and, of course, these are

the original sources of most soil nutrients (other

than nitrogen). The chemical and biological

weathering processes that release these nutrients

are, however, quite slow compared with the release of nutrients from soil organic matter. More

importantly, clay and humus3 particles have large

surface areas and the ability to hold various nutrients (potassium, calcium, magnesium, etc.) on

their surface, preventing leaching and making the

nutrients available for plant growth. Nutrients

such as nitrogen, sulfur, and phosphorus are primarily provided by microorganisms’ conversion

of organic matter in the soil into forms usable by

plants. Soil acidity or alkalinity plays a key role in

the relative availability of these different nutrients.

Many of the physical, chemical, and biological

properties of soils can be strongly modified by

different management techniques; of particular

concern here is the potential impact of bioenergy

cropping.

Physica l

Key physical properties of soils that can be

influenced by how the soil is managed include:

soil density, porosity, permeability, and waterholding capacity; and soil temperature, thermal

conductivity, and heat capacity.

The density of soils can range from as low as

0.13 g/cm3 in the organic residue at the surface of

the soil and from roughly 1 to more than 1.8 g/cm3

in the deeper mineral soils. Densities above

1.4 g/cm3 can impair the penetration of the soil by

roots; above 1.8 g/cm3 root penetration is virtually

stopped. The use of heavy equipment for soil

preparation or harvesting can compact the soil,

especially on moist, fine textured soils. In some

cases this can result in a “hard pan” just below the

depth of plowing that limits deeper penetration by

roots.

Compaction increases the overall bulk density

and, more importantly, tends to squeeze down the

size of pores in the soil. Smaller pores allow poorer

aeration (depending on how sandy the soil is),

reduced water permeability, and are more easily

water logged than uncompacted soils with larger

pores. Compaction can be minimized by harvesting when the soil is relatively dry and strong, by

harvesting in the winter (if and when the ground

is frozen), by minimizing the number of times that

the soil is crisscrossed by equipment, by using

relatively lightweight equipment with wide tires,

and by avoiding rutting the soil or otherwise excessively disturbing it. These factors will tend to

guide further development of equipment used to

3 Humus is the more s~ble pm of soil organic matter. It typically consists of plant tiSSUeS that are resist~t to soil microbes, slowlY

decomposing feces of various soil fauna, and microbial tissue.
Chapter 3–Potential Environmental Impacts 127

plant, maintain, and harvest energy crops as well

as how the crops are managed.

Energy crops generally have deeply penetrating

roots. If they are restricted by a hard pan from

penetrating below about 0.3 meter (1 foot), crop

growth will be affected at some time after crop

establishment when drought occurs or if nutrients

are in somewhat limited supply. Energy crop

growth can also be affected if a hard pan ponds

water below the soil and generates anaerobic conditions which inhibit root growth and plant vigor.

Where hard pans already exist, there may be

little alternative but to break them up. The extensive root systems of energy crops, fewer equipment passes, and increased carbon contributions

to the soil should generally improve soil density

and porosity, and may moderate the reforming of

the hardpan.

Soil temperatures are influenced by:

vegetative cover—vegetation reduces direct exposure of the soil to the sun, lowering temperatures (although heating can be beneficial in the

northern climates in the spring when crops are

first being established),4 and also reduces loss

of soil moisture;

soil color-determines the amount of sunlight

which is absorbed; and

orientation with respect to the sun-determines

how much of the incoming sunlight is intercepted by the soil.

Soil thermal conductivity and heat capacity are

lower for organic soils than for mineral soils, and

lower for dry than wet soils. Together, soil temperatures, thermal conductivity, and heat capacity

help determine the microclimate for soil biota

when establishing a new bioenergy crop or maintaining an existing crop. Management practices

such as how much vegetative cover is maintained,

how much surface residue is collected, or how

much tillage is practiced then strongly influence

these soil characteristics. For energy crops, soil

temperatures appear to be lower except, perhaps,

when they are first established (when temperatures

are comparable) than for conventional agricultural

crops. This helps maintain a higher level of soil

organic matter with attendant soil quality advantages.

Chemica l

Soil chemistry is determined by a delicate interplay of soil minerals, soil acidity/alkalinity, organic matter content, moisture content, and other

factors. Soil minerals include a wide variety of

clays and other silicate materials, and oxides of

iron and aluminum. As the minerals weather, they

gradually release elements (calcium, magnesium,

potassium, etc.) in a form that plants can use as

nutrients. Some of these minerals also attract and

help to hold nutrients, reducing leaching rates.

Soil acidity/alkalinity strongly influence the

availability of various plant nutrients. Acidic soils

allow nutrients such as calcium, magnesium, and

potassium to be more easily leached or converted

into forms that plants cannot readily use. Similarly, alkaline soils may have little phosphorus,

iron, manganese, or other nutrients. Soil acidity/alkalinity also influence the activity of soil

microorganisms.

Soil acidity/alkalinity is influenced by many

factors:

the type of minerals in the soil and the extent to

which they buffer acidity, etc.;

the acidity of rain or other water inputs, the type

of vegetation grown (soils under conifers are

more acid than those under broadleaf trees), and

the decomposition of organic matter;

local rainfall (wet climates can have greater

leaching of acid/alkaline materials);

local atmospheric inputs such as SOX from air

pollution;

and many others.

4 W.E. Larson, J.B. Swan, and F.J. Pierce, “Agronomic Implications of Using Crop Residues for Energy,” William Lockeretz, (cd.),

Agriculture as u Producer und Consumer of Energy, American Association for the Advancement of Science Selected Symposium No. 78

(Boulder, CO: Westview Press, 1982).
28 I Bioenergy

The use of chemical fertilizers and conditioners

such as lime can allow soil acidity/alkalinity to be

controlled and make up for an y particular nutrients

which are limiting potential biomass productivity.

The nutrient most frequently deficient in soils

is nitrogen.5 The principal source of nitrogen in

natural systems is the conversion of organic matter

by microorganisms to forms that can be used by

plants and by biological nitrogen fixation from the

atmosphere. Losses of soil nitrogen can occur by

leaching, volatilization by burning, erosion, and

by conversion back into gaseous nitrogen (denitrification) through biological activity (by certain

microorganisms when they cannot get sufficient

oxygen due to poor aeration of the soil), or less

frequently by chemical reactions.

Phosphorus is also a frequently limiting nutrient. As for nitrogen, phosphorus is often held

primarily in organic forms, and particularly within

the active microbes in the soil. The most intensive

agricultural soils, however, may have more mineral phosphorus than organic phosphorus.

Energy crops affect soil chemistry because they

generally raise soil carbon (organic matter content) compared with annual row crops. This can

buffer soil acidity or alkalinity.6 The organic matter also provides a surface to which fertilizers and

pesticides will adhere rather than leach on through

the soil. This has considerable benefit in managing

these chemicals and reducing possible offsite migration. Energy crops also generally require substantially less fertilizer, herbicides, pesticides, or

other agricultural chemicals than annual agricultural row crops (table 3-l).

Biologica l

Living organisms are essential to all productive

soils; they digest dead plant matter, cycle nutrients

essential for plant growth, and improve the soil

structure. Such organisms include plants (flora)

and animals (fauna); they range in size from microscopic bacteria to small mammals such as

moles; and they have various roles. Some feed on

plant residues, some on live plants, and some prey

on other soil fauna. Energy crops appear to favor

greater and more diverse microbial populations

than typical agricultural rowcrops.7

Microflora such as bacteria and fungi begin the

decomposition process of organic matter by attacking it chemically. Small animals such as beetles, millipedes, and sowbugs physically—by

chewing into the organic matter (simultaneously

increasing the opportunity for microflora to attack

it)—and chemically (digestion) attack it. Earthworms eat their way through the soil, mixing plant

residues and mineral soil, partially digesting it,

and substantially improving the nutrient availability, soil aeration and drainage. Up to 30 or more

metric tonnes of soil per hectare may pass through

earthworms annually. 8 Microscopic insects and

mites may pass 20 to 100 percent of the fresh

organic matter through their bodies each year.

Larger animals such as gophers, moles, prairie

dogs, etc., burrow into the soil—mixing it and

improving its structure through granulation.

Some fungi enhance plant growth. Mycorrhizae

(“fungus root”) fungi form a symbiotic relationship with the roots of higher plants. The fungi

receive sugars and other food materials from the

root; and, in turn, the fungi improve root uptake of

a number of important plant nutrients, including

phosphorus, zinc, copper, calcium, iron, and others. The fungi also improve drought resistance of

the plant. Bacteria, most notably those which fix

nitrogen, play a key role in maintaining soil fertility as well.

Soil microbes also compete with each other for

food and have developed substances that inhibit or

kill other microbes. Important products from such

microbiota include penicillin and streptomycin.

5 In hotter, more humid climates, phosphorus is often deficient.

6 Thus, it can raise pH (make less acid) for some acid soils and can lower pH for some alkaline soils.

7 Jack Ranney, Oak Ridge National Laboratory, personal communication, Sept. 1, 1993.

8 Nyle C. Brady, The Nature (lnd proper(;e.$ of Soi/,r, (New York, NY: Macmillan Publishing Company, 1984).
Chapter 3–Potential Environmental Impacts 129

Table 3-l—Typical Erosion Levels and Agricultural Chemical Use of

Selected Food and Energy Crops

Fertilizers

Erosion Nitrogen Phosphorus Potassium Herbicide

Crop (Mg/ha-yr) (kg/ha-yr) (kglha-yr) (kg/ha-yr) (kg/ha-yr)

Corn 21.8 135 60 80 3.06

Soybeans 40.9 10 35 70 1.83

HECs 0.2 30 50 90 0.25

SRWCs 2.0 60 30 80 0.39

SOURCE: Lynn L. Wright and William G. Hohenstein (eds.), “Biomass Energy Production in the United States:

Opportunities and Constraints,” U.S. Department of Energy and U.S. Environmental Protection Agency, draft, August

1992.

Based on findings in Germany, the short rotation woody crop (SRWC) hybrid poplar changes

agricultural land biota to biota more resembling

forest soil environments (more worms, fewer beetles and spiders).9 The knowledge of soil biology

and microbial ecology is poor, however, so it is not

known to what extent these results can be generalized—that SRWCs will restore soil biota to preagricultural conditions for different soils, crops,

climates, and management practices. The increased soil carbon, lower soil temperatures, and

more consistent soil moisture conditions, however, may at least partially restore native soil biota

and their attendant benefits.

Before the widespread availability of commercial fertilizers, nutrients recycled by the biota were

recognized as a major component of land productivity, and thus soil ecology ranked high among

the agricultural sciences. In recent decades, however, this aspect of soil science has been largely

10 Use of artificial fertilizers can in- neglected.

crease crop growth to such an extent that organic

matter inputs and soil biota are increased substantially.

11 Energy crops generally will require a

management approach using both fertilizers and

organic matter improvement. This might be considered a hybrid system of low-intensity sustainable agriculture to attain high productivity.

Agricultural scientists generally are not

alarmed about pesticides harming soil ecology in

the near term: some research indicates that pesticides usually have minor and short-term impacts

and side effects on soil microbiota other than those

targeted. Such findings continue to be controver12 Frequent applications of toxic sial, however.

chemicals can change the composition of soil biota

communities, favoring species that can adapt to

the new chemical environment.

13 Further, certain

broad-spectrum pesticides may also kill earthworms or microscopic insects and mites that condition the soil; this can slow the rate of organic

matter turnover and nutrient release for plant

growth.

The impact of long-term use of such agricultural chemicals on land productivity is not known.

Because methods are not sufficiently well developed to make practical differentiation among microbe species in the field, and soil invertebrates are

seldom studied, the cumulative effect of chemical

use on productivity cannot be fully measured.

Crop rotations are also widely effective in disrupt-

~ F MakesChin, University of Munich, 1991; Jack Rm-mey, Oak Ridge National Laboratory, pemon~ communication> SePt. 1! 1993”

lo U.S. Congress, Office of Technology Assessment, Impacn of Technology on U.S. Cropland and Rangeland produ~tivify, OTA-F-166

(Washington, DC: U.S. Government Printing Office, August 1982).

11 Richard p. Dick, ‘{A Review: ~ng-Term Effects of Agricultural Systems on Soil Biochemical and Microbial pmameters,” Agriculture,

Ecosystems and Environment, vol. 40, 1992, pp. 25-36.

12 W. be D~ie]s, Virginia polytechnic and State University, personal cOmmLIniCatiOn, Sept. 1, 1993.

1~ See, for example: D.A. Cross]ey, Jr., Barbara R. Mueller, and Judy C. perdue, “Biodiversity of Microarthropods in Agricultural Soils:

Relations to Processes,” Agriculture, Ecosystems and Environment, vol. 40, 1992, pp. 37-46.
30 I Bioenergy

ing disease cycles and maintaining soil microbial

and enzyme levels and are often preferable to

 Energy crop prac- using agricultural chemicals.14

tices which now rely on multiyear monoculture

need to recognize crop rotation benefits through

innovative practices such as species mixes. Energy crop development has not yet pursued such

innovative practices and may need to look toward

range management and forestry for guidance.

The movement of agricultural chemicals beyond the field to which they are intended is also of

concern. This can occur by groundwater contamination, runoff into streams, misapplication (such

as drifting with the wind during aerial application), or by entering the food chain of animals or

15 During the crop establishment phase, people.

energy crops raise these concerns just as does

conventional agriculture. Compared with annual

agricultural row crops, energy crops do not substantially lower the risk of agricultural chemical

movement until their second or third year of

growth.

Agricultural chemicals such as fertilizers, insecticides, herbicides, and fungicides have a variety of impacts on wildlife. Fertilizer runoff into

surface waters can lead to eutrophication and can

damage some aquatic species (see below). Herbicides generally have low toxicity for birds and

mammals, but some have been shown to affect

reproduction rates directly or indirectly. Insecticides, particularly the organophosphates (which

are the most widely used insecticides in the United

States), can kill some wildlife following application and can affect their reproduction. Overall

impacts of these agricultural chemicals on wildlife

are poorly understood. Some organophosphates

may be used during energy crop establishment.

After the crop becomes well established, herbicides are no longer needed. As the energy crops

considered here are replanted only every 15 to

20 years, the use of herbicides is substantially

reduced compared with usage needed for agricultural crops.

Insect, bird, and mammal predators that control

pests but which have been damaged either through

loss of habitat, agricultural chemicals, or other

means make agricultural, forestry, or energy crops

more susceptible to outbreaks of pests. Eastern

tent caterpillars, southern pine beetles, and cottonwood leaf beetles, for example, are preyed upon

heavily by various birds. This loss of predator

species may require increased use of pesticides to

maintain pest control.

Nutrient Cycling

Most nutrients available for plant growth in

non-agricultural systems (in agricultural systems,

nitrogen, phosphorus, and potassium are generally

added annually) come not from atmospheric inputs or the gradual weathering of minerals (although these are the initial sources of these

nutrients) but from decomposition of plant matter

by microorganisms. Although standing and decaying biomass (above and below ground) might represent just a quarter of the total nitrogen in a forest

system, for example, it accounts for most of that

actually available for plant growth.

Harvesting energy crops can have several impacts on nutrient cycling. Nutrients are removed

with the crop. Immediately following harvesting,

warmer (more direct sunlight) and wetter (less

water is taken up and transpired by vegetation)

conditions in the soil may increase rates of decomposition and nutrient release just when vegetation

is least available to make use of these nutrients.

Leaching and other losses of nutrients then often

follows, but are usually substantially less than the

nutrient losses due to the removal of the biomass

itself.

The quantity of nutrients removed by harvesting depends on the age of the biomass crop, the

specific parts removed, and the time of year of the

14 Rich~d p. Dick, “A ReVieW: LOng.Terrn Effects of Agricultural Systems on Soil Biochemical and Microbial pm~eters,” Agn”culture,

Ecosystems and Environment, vol. 40, 1992, pp. 25–36.

I 15 see, for example: Nation~ Rese~ch council, F’estickfes in (he Diets of hf(mts and Children (Washington, DC: National Academy p~s%

1993). I
Chapter 3–Potential Environmental Impacts 131

harvest. Young trees have proportionately more

nutrients per unit biomass than older trees since

leaves and branches have more nutrients than tree

trunks and are a greater proportion of total

biomass. In a four-year rotation of poplar, for

example, nitrogen, phosphorus, potassium, and

calcium content of leaves were typically 20 times

greater than that of the trunks per unit biomass.16

Timing the harvest for periods when nutrients are

lower and removing primarily nutrient-poor material (tree trunks, bark, and major limbs) can reduce

the tax on nutrients and help move toward more

sustainable biomass energy systems. Nutrient

losses can be reduced by leaving leaves and

branches uniformly distributed across the entire

site. Harvesting of herbaceous perennial energy

crops faces similar considerations, but may nevertheless be somewhat more taxing of nutrients due

to their higher nutrient content per tonne. Nutrient

losses also increase if there is increased erosion,

such as during planting.

Simply counting direct nutrient losses, however, may be insufficient in indicating the total

impact (positive or negative) of energy cropping

on the soil. Changes in the physical structure (i.e.,

compaction), chemistry, biological makeup (species composition and balance), and other aspects

must also be considered.

Overall, annual row crops with complete removal of the biomass can reduce soil quality and

productivity. Longer cycles and reduced biomass

removal—such as with herbaceous perennials or

short-rotation woody crops-can be neutral or can

even improve soil quality in many areas compared

with conventional agricultural monoculture.

Limited tillage and turnover of organic matter to

the soil will also enhance soil quality compared

with systems that have frequent tillage and complete residue removal.

Site preparation for planting energy crops may

involve extensive plowing/disking/subsoiling17 of

the land (although no-till practices have been

evaluated). This can improve soil conditions for

establishing the crop, but may also temporarily

increase nutrient losses and erosion rates for up to

several years—which may lead to reduced growth

rates after three to four years and in the longer

term. Disking also does not help deep compaction

from heavy equipment; deeper disking may be

impractical as it can damage the root systems of

the crop.

Ultimately, rapid rotations and extensive

biomass removal will require use of fertilizers or

other means—including multiple or mixed cropping systems-of replacing lost nutrients. Mixed

crops, for example, might include the use of nitrogen fixing species. This would reduce the need for

applying fertilizers and could potentially improve

habitat, as discussed below, but could also complicate some processes for converting these feedstocks into liquid fuels.

Soil Erosion

1 8

There is little net natural soil erosion in areas

with undisturbed, continuous vegetation. Typical

rates are less than 0.5 tonne/hectare-year of soil

lost, and this is also less than the typical rate at

which new soil is formed through natural

processes.

Erosion is increased above this natural rate

when soils are directly exposed to runoff water

either by tilling the soil or by removing the canopy

lb phi]ip E. pow, “impacts of Increased Use of Forest Resources on Soil Quality,” contractor report prep~ed for the OffiCe of ‘echnO1og)’

Assessment, May 13, 1993, table 2.

IT Subsoiling is done t. break Up compacted soils (hard pan) below the Sutiace.

18 us, congress, Office of Technology Assessment, lnlp(l~.ttf ~~ Te(hn~)[{)8Y {Jn U.S. Crop[(lnd (Ind R(lngel(ind productivi~, OTA-F-166

(Washington, DC: U.S. Government Printing Office, August 1982); W. Lee Daniels and Jody N. Booze-Daniels, “Biomass Cropping Systems

and Soil Erosion,” contractor report prepared for the Office of Technology Assessment, Apr. 28, 1993.
32 I Bioenergy

of plants or plant residues protecting the soil.19

When the protective canopy is removed, rainfall

directly striking the soil can dislodge particles and,

when the soil is saturated with water, carry them 20 The use of heavy down the slope in the runoff.

equipment to plant, work, or harvest the crop can

contribute to its erosion potential by compacting

the soil and reducing the infiltration of water, thus

increasing runoff. Large amounts of erosion can

also occur along access roads to the cropped area.

In contrast, a protective cover of plants or residues breaks the impact of the rainfall and retains

a portion; increases the infiltration of rainfall into

the ground and thus delays the onset of runoff;

helps hold the soil in place; and breaks up the flow

of runoff, allowing suspended soils to drop out of

the runoff before being swept out of the field.

Contour plowing, contour strip cropping, terracing, minimum or no-till, and other techniques, for

example, can also slow the loss of soil, and strips

of vegetation can be used to filter sediments out of

runoff before it leaves the field.

Annual erosion rates for lands with perennial

energy crops will probably be in the range of 0.2

to 3.0 tonnes per hectare, based on projections and

very limited field data. Without conservation

measures during the crop establishment phase (the

first year), however, erosion rates may parallel

com at 10 to 20 tonnes/hectare. Such high rates

drop rapidly in the second and subsequent years of

growth when there is continuous cover, Harvesting is likely to increase erosion rates somewhat,

but rates following harvesting will still be only a

fraction of those during the crop establishment

period. It is therefore important that soil conservation measures be employed during establishment. 21

Soil erosion primarily occurs in a relatively few

catastrophic events. For example, the soil is relatively unprotected following spring plowing and

planting and before the crops have become well

established. At this time, extreme downpours or

high winds can result in large losses of soil, and

particularly soil organic matter and nutrients concentrated in the upper layer of the soil. Energy

crops such as HECs and SRWCs are only replanted every 15 to 20 years, and this greatly reduces the probability that the soil will be

uncovered during an extreme downpour. This also

emphasizes the importance of soil conservation

measures during the energy crop establishment

phase when soils are most vulnerable.

Soil erosion can also degrade soil structure.22

Losses of organic matter and nutrients are especially costly to soil productivity, as discussed

above. In addition, where the remaining soils have

a high silt or clay content, they are even more

susceptible to further erosion. In this case, the clay

tends to form a crust which limits water infiltration. Energy crops should generally reverse the

degradation of soil structure, but field monitoring

is needed to verify this.

As topsoils are eroded, less productive subsoils

must support plant growth. These subsoils are

often low in nutrients, dense, and generally infertile. In much of the southeastern United States, for

example, subsoils tend to be quite acidic, clayey,

very low in available phosphorus and other nutrients, and relatively high in soluble aluminum

which is toxic to plants. It is on such sites that some

of the herbaceous perennial crops may be relatively productive and yet stabilize or partially restore some desired soil functions. Tree crops may

fare less well due to often much lower productivity

on such degraded sites.

19 Erosion rates do not represent net losses of soil because eroded soil does not simply vanish. Much of the soil moved by erosion remains

in the same field, but is farther downslope or downwind, Soil is eventually lost, however, as it moves off fields into waterways or onto

noncroplands. Soil quality is affected by soil movement because organic materials and other lighter components are moved first, leaving behind

poorer soils.

Z(J The fWus here wil] be on water erosion, but similar considerations apply tO wind erOsiOn.

21 Jack Ranney , oak Ridge National ~boratory, personal communication, Sept. 1, 1993.

22 WE. ~son, F-J, Pjerce, and R,H, Dowdy, “The Threat of Soi] Erosion to ~ng.Term Crop production,” Science, VO]. 219, Feb. 4, 1983,

pp. 458-465.
Chapter 3–Potential Environmental Impacts 133

The actual amount of soil erosion varies widely

depending on the intensity of the rainfall, the type

and condition of soil, the slope length and pitch,

the type and quantity of vegetation on it, and other

factors.23 In turn, the resultant productivity ‘f a

crop on eroded soil varies widely by the soil type,

quality, and depth, by the region, by the type of

crop, and other factors. The response of the crop

to erosion is sometimes unpredictable. In general,

loss of soil organic matter and fine clays reduces

availability of plant nutrients, reduces soil nutrient-retention and water-retention capacity, and reduces plant rooting depth as the soil layer thins.

Again, energy crops are believed to generally improve soil quality compared with conventional

agricultural row crops, and early results from field

monitoring in Virginia clay, Midwestern soil, and

elsewhere support this.24

The average annual loss of soil from cultivated

U.S. cropland was about 9.2 tonnes/hectare-year

in 1987,25 far higher than the estimated 1 tonne/hayr rate of natural soil formation and at the high end

of the 2 to 11 tonnes/ha-year guidelines used by

the USDA Soil Conservation Service for acceptable long-term losses. Currently, erosion losses in

many areas exceed the established USDA-SCS

guidelines even when following locally approved

conservation practices. Although these losses can

be serious, in many cases they are not easily observable. For example, 10SS of 10 tonnes/ha-year

corresponds to a loss of 2.5 cm (1 inch) of topsoil

over 30 years.

The impact of energy crops on soil erosion is

potentially mixed, depending on what the energy

crop is compared with, the type of energy crop

grown and how it is managed (especially during

establishment), how much residue is left on the

soil following harvesting, the type of soil, the

slope of the land, and plain luck. The key to low

erosion rates is having continuous, dense cover on

the soil. For example, on a particular type of soil

with a 4 percent slope, soil erosion rates in the

production of soybeans were 41 tonnes/ha, in the

production of corn were 22 tonnes/ha, and in the

production of a continuous perennial grass was

just 0.2 tonnes/ha.26

HECs and SRWCs generally will have lower

levels of erosion than conventional row crops and

similar levels as well-maintained pasture. Detailed

analyses for various energy crops, however, generally remain to be done and estimates of energy

crop erosivity parameters remain to be verified. As

energy crops push into marginal lands,27 erosion

rates could increase28 and crop productivities

could suffer.29

USDA benefits are only provided those farms

with approved soil conservation compliance plans

for their highly erodible lands. Perennial bioenergy crops generally could be used effectively on

these lands. Currently, lands enrolled in the Conservation Reserve Program are taken out of production for 10 years and can only be harvested

during that time if there is an extreme local

drought. Rather than allowing these highly erosive

lands to revert to conventional crops at the end of

that 10 years, some have suggested that reduced

(from CRP levels) incentives be considered to

encourage converting these lands to energy crops.

23 The most common method of predicting potential erosion is with the Universal Soil Loss ~uation which inCOrpOHltf3S empirical factors

for all these parameters. See: W.H. Wischmeier and D.D. Smith, Predicting Rainjid/ Erosion Losses, USDA Agricultural Handbook 537

(Washington, DC: U.S. Government Printing Office, 1978).

24 Jack Ranney, O* Ridge National ~borato~, personal communication, Sept. I ~ 1993.

25 U.S. ~p~mnt of Agriculture, soil Conservation service, “12~timated Average Annual Sheet and Rill Erosion on Cropland, By State

and Year,” 1987 National Resources Inventory, Washington, DC.

26 David Pimntel ad John Kmmm., C~Bioma~s E~rgy ~d Soil ~sion: Assessment of Resource Costs,” Bio~rs, VO1. ]4, 1987, pp. 15-38.

27 That is, if the lands we mmgin~ ~cause of highly er~ible soils or slows, but not if they me m~ginal due to wetness (X heavy SOilS.

28 A.F. ‘J’Urhollow, Jr., s-s, Shen, GE. Oamk, and E.O+ Heady, The p{,~entiul impact.~ of ~qy-scale Biom.r.r Production On U.S.

Agriculture, CARD Report 130, The Center for Agriculture and Rural Development, Ames, IA: Iowa State University, 1985.

z~ F*J. pierce, R.H. Dowdy, WE. ~son, ~d W,A.p. Grah~, “soil productivity in the Com Belt: An Assessment of Erosion’s Long-Term

Effects,” Journal of Soil and Water Conservation, vol. 39, No. 2, March-April 1984, pp. 131-136.
34 I Bioenergy

The environmental impacts of the energy crops are

likely to be mixed, however, compared with continuing the land under CRP.

Summary: Energy Crops and Soil Quality

The impact of energy crops on soil quality

depends on the energy crop, the soil, the climate,

the land use it is replacing, and many other factors.

Extensive removal of biomass residues from energy cropland for use as fuel or feedstock can

reduce soil organic matter levels and associated

soil quality. Some high-productivity energy crops

such as certain herbaceous perennials can, however, provide a net increase to soil organic content

relative to row cropping due to their heavy rooting

alone. Energy crops with limited till age and which

return large quantities of organic matter (e.g., leaf

litter) to the soil can improve soil quality compared with those that rely on frequent tillage or

complete removal of crop residues. Such a protective layer of vegetative cover helps to provide shading, maintain soil moisture content,

prevent erosion, and may offer other environmental services.

Use of heavy equipment for preparing the soil,

or for planting, maintaining, or harvesting the

energy crop must be done cautiously to avoid

compacting the soil or otherwise damaging the soil

structure. For energy crops, this is primarily of

concern during establishment and harvesting on

soils that are heavy and/or wet.

Soil chemistry—nutrient balance and acidity—

can be more easily managed than soil physical

properties, but may nevertheless require a rigorous

program of soil testing and crop-specific additions

of fertilizer, lime, and other inputs. Preliminary

results from studies elsewhere (India, Virginia,

Minnesota) suggest that acidity/alkalinity is buffered and soil structure is improved where HECs

and SRWCs are in production compared with conventional agricultural practices. This is mainly due

to increased organic matter content in the soil.30

A “minimum data set” of important soil properties-physical, chemical, and biological-could

be developed for biomass production systems.31

This data set could then be used to follow changes

in lands used for bioenergy crops. It is much more

important to follow changes over time than to

measure a particular parameter, such as organic

matter content, a single time. Similar data sets

could be developed for surface and groundwater

resources and for habitat (see below). This minimum data set could be developed in conjunction

with extensive and carefully designed field trials. 32

WATER QUALITY33

Energy crops may affect water quality either positively or negatively, depending on the way they

are managed, the land use they displace, and the

specific impact examined. With good management they may significantly reduce nonpoint pollution of surface waters from agricultural

practices, with attendant benefits for water quality

and fish habitat (box 3-A). With poor management, they could increase the runoff of sediment,

So Jack Ranney, oak Ridge Nationa] Laboratov, personal communication, Sept. 1 ! 1993$

S1 As one ~xmp]e, see: W.E. Larson and F.J. pierce> “Conservation and Enhancement of Soil Quality,” Evaluation f{w Suskdnalde Lund

Management in the Developing World, vol. 2: Technical Papers, Bangkok, Thailand, International Board for Soil Research and Management,

1991, IBSRAM Proceedings No. 12(2); M.A. Arshad and G.M. Coen, “Characterization of Soil Quality: Physical and Chemical Criteria,”

American Journal of Altemtitive Agriculture, vol. 7, 1992, pp. 25-30.

32 Monitoring crop yields alone may not IX an adequate indicator of soil quality because crop varieties are frequently changed in order to

improve yields, irrespective of soil conditions.

~~ u s Congress, ., Office of Technology Assessment, Inymts of Technology” on U.S. Croplund and RanKeland productivity, OTA-F-166

(Washington, DC: U.S. Government Printing Office, August, 1982); U.S. Congress, Office of Technology Assessment, Benea/h the Bottom

Line: Agricultural Approtmhes It) Reduce Agrichemical Contamination of Groundwater, OTA-F-418 (Washington, DC: U.S. Government

Printing Office, November 1990), W. Lee Daniels and Jody N. Booze-Daniels, “Biomass Cropping Systems and Water Quality,” contractor

report prepared for the Office of Technology Assessment, Apr. 28, 1993. See also: Jodee Kuske, “Water Quality and Forestry: January 1982–July

1990,” Quick BibliogrcJphy Series: QB 9Z-53, 221 citations from AGRICOLA, Water Quality Information Center, National Agricultural Library,

Beltsville, MD, March 1991.
Chapter 3–Potential Environmental Impacts 135

Box 3-A-impacts of NonPoint Water Pollution

Nonpoint water pollution, whether from agriculture or other activities, has a variety of impacts on U.S.

water resources and fish and other wildlife.

Increased sedimentation of streams and other bodies of water, primarily from erosion, may destroy fish

feeding and breeding areas. Streams may become broader and shallower so that water temperatures rise,

affecting the composition of species the stream will support. Riparian wildlife habitats change, generally

reducing species diversity.

Pollutants and nutrients associated with eroded sediments can have adverse impacts on aquatic

environments. Concentrations of toxic substances may kill aquatic life, whereas nutrients in the runoff can

accelerate growth of aquatic flora. This can aggravate the sedimentation problem and lead to accelerated

eutrophication of water bodies. Eutrophication is a process that usually begins with the increased production

of algae and plants. As they die and settle to the bottom, the micro-organisms that degrade them use up the

dissolved oxygen. Sedimentation also contributes to exhausting the oxygen supply, especially in streams and

rivers, by reducing water turbulence. Thus, the aquatic ecosystem changes dramatically.

Phosphorus and nitrogen are the major nutrients that regulate plant growth. Soil nitrogen is frequently

leached or runs off into water supplies. Phosphorus, on the other hand, is “fixed” in the soil, so runoff typically

contains relatively small amounts. Under normal conditions, therefore, phosphorus is more likely to be the

limiting factor in aquatic plant growth. Since phosphorus (along with potassium, calcium, magnesium, sulfur,

and the trace elements) is held by colloid material, however, it is abundant in waters receiving large amounts

of eroded soil This can lead to eutrophication.

Natural eutrophication is generally a slow process, but man-induced eutrophication can be extremely rapid

and can produce nuisance blooms of algae, kill aquatic life by depleting dissolved oxygen, and render water

unfit for recreation. Replenishing the oxygen supply is a costly remedy because of the energy and equipment

investment on the scale required.

SOURCE: U.S. Congress, Office of Technology Assessment, Impacts of Technology on U.S. Cropi’and and Rangelartd

Pmductlvity OTA-F-166 (Washington, DC: U.S. Government Printing Office, August 1982); U.S. Congress, Office of

Technology Assessment, Beneath the Bottom Line: Agrkultural Approaches to Reduce Agtfchc?mical Com’arnirwtion of

Groundwater, OTA-F-418 (Washington, DC: U.S. Government Printing Office, November 1990). W. Lee Daniels and Jody

N. f300ze-Daniels, “Biomass Cropping Systems and Water Quality,” contractor report prepared for the Office of Technology

Assessment, Apr. 28,1993.

fertilizers, or pesticides into streams during the levels. Conventional agricultural practices have

establishment phase. They may help control, or

contribute to, nonpoint contamination of groundwater. They may influence water table changes,

Nonpoint sources of water pollution may account

for half or more of the remaining water problems

in the United States;34 energy crops may offer a

tool not previously available to help deal with

some of these water quality issues.

Nitrogen in some form is needed for any crop,

including energy crops, to attain high productivity

allowed nitrogen and other agricultural chemicals

to enter water supplies in many areas. Nitrogen (in

the form of nitrate) and, in some cases, pesticides

and herbicides are the most frequent contaminants

of groundwater. A 1990 EPA study found detectable levels of nitrates in half of the 94,000 community water systems tested, although almost all

of these were well below the levels believed to

 primary contributors of nitrates cause problems.35 

to groundwater include improperly functioning

34 Counci] for Agricultural Science and Technology, “water Quality: Agriculture’s Role,” T~/.~k Force Report No. Z20, December 1992.

35 A separate study of 1,347 wells found only 1 to 2 percent exceeding health standards. See: J.W. Ranney and L.K. Mann, “Environmental

Issues,” Lynn L. Wright and William G. Hohenstein, (eds.), Bitmum~ Energy Production in the United States: Opportunities and Constraints,

U.S. Department of Energy and U.S. Environmental Protection Agency, DRAFT, August 1992.
36 Bioenergy

septic tanks, agricultural activities, and animal

wastes at central facilities such as feedlots. Nitrates move readily through the soil and can

quickly reach groundwater unless first taken up by

plant roots and incorporated in plant growth or by

microbes feeding on plant residues.

Energy crops can have significantly deeper and

heavier rooting patterns than conventional agricultural crops, allowing greater uptake of nitrogen

and other agricultural chemicals before they can

migrate offsite. Root zones for many agricultural

crops are less than 0.3 meters. Effective rooting

depths vary from about 0.3 to 1 m for some herbaceous perennials and 0.6 to 2 m for some woody

crops. The likelihood that chemicals can leach

below these levels depends heavily on:

■

■

■

■

■

■

! ■

t

I

the season—root uptake is low during the winter for many crops;

the soil type and condition;

the amount of rainfall;

how heavily the chemicals are applied;

the vigor and amount of energy crop—newly

planted or harvested crops have little ability to

absorb large quantities of chemicals, however

useful they might be;

the extent of soil microbial activity;

and other factors.

Energy crops may also require less nitrogen

I fertilizer than agricultural crops. Extensive re- 1

I search on these and related issues is now underway I

I at Oak Ridge National Laboratory for short-rota1 tion woody crops, but there is little data for most I

1 herbaceous perennials. Results to date indicate a

high degree of nitrogen uptake and cycling except

I when high levels of nitrogen are added during the

first year of crop growth.

Sediment, phosphorus, pesticides, and herbicides are the primary contaminants of runoff.

Phosphorus is strongly bound to the soil and is

readily taken up by soil microbes. Consequently,

there is little migration of phosphorus to groundwater, but erosion can carry large amounts of

phosphorus with it. Runoff of phosphorus to surface waters can cause eutrophication of these waters with all the attendant problems. Energy crops

can potentially reduce the problem of soil and

chemical runoff by lowering the requirements for

these inputs compared with conventional crops, by

controlling and 1imiting erosion and runoff, and/or

by serving as filter strips to limit runoff from

36 The extent to which this po--

agricultural lands.

tential is realized depends on the previous use of

the land, how the energy crop is established and

maintained, the soil type and slope, and other

factors.

Nonfertilizer agricultural chemicals such as

herbicides, fungicides, and insecticides can also

move into groundwater or surface waters; energy

crops are expected to use less of these chemicals

than does conventional agriculture. The 1990 EPA

survey of 94,000 community wells found 10 percent with detectable levels of one or more pesticides from past agricultural practice. Almost all of

these cases were far below standard safety levels

and thus posed little human health threat. They do,

however, indicate the ability of such agricultural

chemicals to migrate through the environment.

The extent to which a chemical is lost depends

on many factors, including:

possible misapplication of the chemical, such as

spray drift to surface waters during aerial application;

runoff during heavy rainfall closely following

application of the chemical during planting,

when erosion and runoff are most likely;

the type of chemical and the strength of its

binding to the soil and plants;

how much is applied;

how quickly it decomposes;

the topography;

the type of crop and how it is managed (no-till

versus conventional row crops);

and other factors.

36 T. serve ~S a fjlter ~d t. ~ h~vested pefiodi~a]]y for energy, energy crops may require more complex ~~ c~eful m~agement ‘han

typical for energy crops which do not serve such demanding multiple functions.
Chapter 3–Potential Environmental Impacts 137

These are of concern for energy crops as well

as for agricultural crops.

It is difficult to generalize about these agricultural chemicals and their fates. Conventional notill agricultural crops, for example, will have

higher soil moisture contents and humidity levels,

perhaps leading to more rapid rates of some

chemical decomposition, but may also require

higher levels of chemical application. Nevertheless, due to lower levels of runoff, no-till crops

tend to have much lower total losses of chemicals

to surface waters. On the other hand, some chemicals that would decay in a relatively short time

under normal aerobic conditions may nevertheless

be fairly stable in the anaerobic soils of wetlands

37 Energy crops and may therefore accumulate.

considered here will generally follow the model of

no-till agricultural crops, but will use less agricultural chemicals.

Their fates are similarly uncertain when agricultural chemicals enter groundwater or surface

water. In general, relatively little is known about

how these chemicals degrade in groundwater.

Some binding of these chemicals to mineral particles and some biodegradation do occur, depending

on the mineral, acidity, temperature, type of bacteria present, etc. Groundwater and surface waters

are also frequently interchanged, so that nitrogen

or other chemicals in groundwater may move into

surface waters and vice versa.

Finally, high-productivity energy crops may

use 300 to 1000 tonnes of water per tonne of

biomass grown.

38 In some areas, such demands

could impact local groundwater supplies. How

overdraft and recharge problems should be handled in the context of energy crops may pose

substantial challenges. Energy crops may, however, offer a tool for water table management in

poorly drained areas or a more robust crop for

flood-prone zones.

AIR QUALITY39

Energy crops can impact air quality in a variety of

ways, again depending on the particular energy

crop, the land use it is replacing, and how it is

managed. Compared with annual row crops, HECs

and SRWCs are likely to reduce wind-blown dust

and tillage dust (except during establishment);

reduce the use of agricultural chemicals; and reduce the use of diesel powered equipment for

preparing the soil and for planting and maintaining

the crop, but in many cases may increase use for

harvesting and transport. HECs and SRWCs are

likely to increase all of these emissions compared

with pasture and Conservation Reserve Program

lands. Energy crops may also affect the emission

of hydrocarbons from growing plants. Finally,

energy crops take up carbon dioxide from the

atmosphere and can sequester the carbon in the

plant biomass and in the soil. The net cost/benefit

of these changes in emissions in producing energy

crops must be measured against the changes in

emissions when they are used as a substitute for

fossil fuels—for transport, electricity generation,

or direct heat applications-considering the ambient air conditions in the locality affected by the

emissions and total greenhouse gas emissions.

Wind-blown dust from land used to grow HECs

and SRWCs should usually decrease compared

with that from agricultural lands as the soil should

37 Atrazine may k ~ examp]e. See: W. he Daniels and Jody N. Booze-Daniels, “Biomass Cropping Systems and Water Quality,” conwactor

report prepared for the Office of Technology Assessment, Apr. 28, 1993.

~~ David O. H~l, Fr~k Rosillo-Calle, Robert H, Williams, and Jeremy woods, “Biomass for Energy: Supply Prospects,” Thorn&s B.

Johansson, Henry Kelly, Amulya K.N. Reddy, and Robert H. Williams, (eds.), Renewable Energy.’ Sources for Fuels and E/ectrici~

(Washington, DC: Island Press, 1993).

39 Steven Shaffcr, ~~Air Quality ]mpacts from Agriculture Biom~\s production ad Residue Utilization as Energy Feed Stocks,” contractor

report prepared for the Office of Technology Assessment, May 13, 1993.
381 Bioenergy

have more continuous cover.40 win&blown dust

could increase, however, in areas where agricultural crop residues are more intensively collected

for energy rather than being left on the field to

protect the soil from wind or water erosion. Dust

generated during tillage-nominally 6 kgha of

PM-10(particulates with a diameter of l0 microns

or less) for each pass through a bare field41—

should also be reduced, as most energy crops will

be perennials, replanted every 15 to 20years.This

is in contrast to the annual planting and maintenance of many conventional agricultural crops.

Field burning of agricultural residues will continue to be practiced in some areas, primarily on

the West Coast, as a means of pest and weed

control, to reduce residue volumes, and for other

reasons. In some cases, however, the creation of a

market for bioenergy may make it sufficiently

attractive for farmers to collect residues and haul

them to market rather than bum them on site. Burning these residues in a properly designed and operating boiler, furnace, gasifier, etc., produces

much fewer emissions than field burning. In some

areas such as California’s Central Valley, clean air

laws may limit field burning and thus encourage

residue collection and use as fuel or feedstock.

Growing plants release a variety of hydrocarbons. Non-methane hydrocarbons are primarily

isoprene, which accounts for 50 to 80 percent of

the emissions from deciduous trees, and monoterpenes, which account for most emissions from

conifers. Agricultural crops emit relatively little

hydrocarbon. Estimated emission rates, with very

large uncertainties, are roughly 5, 50, and 200

kg/ha-yr from agricultural crops, deciduous forests, and coniferous forests, respectively .42

Although such biogenic emissions43 of hydrocarbons may be as much as twice those from

anthropogenic sources during the summertime

peak in the Lower 48 states, the biogenic emissions are spread over a much larger area than

anthropogenic emissions and would result in relatively little ozone formation when NOX concentrations are low, which is typical for many rural

areas.

44 The impact of energy crops on hydrocar--

bon emissions will depend on the particular crop

compared with the previous land use and the area

cropped. Overall biogenic hydrocarbon emissions

are unlikely to be dramatically changed. If there is

a net increase45 in the use of diesel-powered equipment for energy cropping, this could result in a

slight increase in generation of ozone in rural

areas, as this equipment could provide the NOX

that is now often lacking for ozone formation.

Conversely, decreased use of diesel equipment

compared with conventional row crops might reA[) The wind erosivity of a p~icu]m soil depends on the type of soil, the field roughness, the local climate (rainfall ~d wind), the length of

the field (how much time the wind has to loft particles), and the vegetative cover. Average wind erosion levels range from about 100 kg/ha-yr

for wheat to nearly 500 kg/ha-yr for soybeans. Roughly 85 percent of U.S. cropland, pastureland, and rangeland has a potential wind erosivity

too low to be of concern, 11 percent requires moderate conservation measures, and 4 percent requires careful soil management. See Steven

Shaffer, “Air Quality Impacts from Agriculture Biomass Production and Residue Utilization as Energy Feed Stocks,” contractor report prepared

for the Office of Technology Assessment, May 13, 1993.

41 U.S. Environment~ protection Agency, Office of Air Quality Planning ~d Standmds, “Control of Open Fugitive Dust Sources,”

EPA-450/3-88-008, 1988; U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, “Fugitive Dust Background

Document and Technical Information Document for Best Available Control Measures,” EPA-450/2-92-O04, 1992; cited in Steven Shaffer, “Air

Quality Impacts from Agriculture Biomass Production and Residue Utilization as Energy Feed Stocks,” contractor report prepared for the Office

of Technology Assessment, May 13, 1993.

AZ Steven Shaffer, “Air Qua]ity Impacts from Agriculture Biomms Production and Residue Utilization as Energy Feed Stocks,” Conwactor

report prepared for the Office of Technology Assessment, May 13, 1993.

43 Estimates of biogenic emissions may be high or low by a factor of 3 or more due to uncertainty in the measurements of emissions, land

use, and other factors.

44 ch~]es Bl~chmd, Envair, persona] communication, Aug. 24, 1993; U.S. Congress, Office of Technology Assessment, Catching Our

Breath; Nexr Stepsfirlleducing Urban Ozone, OTA-O-412 (Washington, DC: U.S. Government Printing Office, July 1989); J.W. Ranney and

L.K. Mann, “Environmental Issues,” Lynn L. Wright and William G, Hohenstein (eds.), “Biomass Energy Production in the United States:

Opportunities and Constraints,” U.S. Department of Energy and U.S. Environmental Protection Agency, DRAFT, August 1992.

45 This Coukj occur if the ]and was previously idle or if the energy crop required more fUd for hmsting and tr~spoflthan was‘aved bY

reducing planting and maintenance requirements.
Chapter 3–Potential Environmental Impacts 139

duce rural ozone formation. These changes are

unlikely to cause significant regulatory problems

except in regions where ozone standards are already being approached or exceeded, such as California’s Central Valley.

Use of agricultural chemicals and diesel fuel

and their corresponding emissions will increase as

idled or abandoned cropland is shifted over to

energy crops. The intensity with which chemicals

and fuels are used will, however, vary from conventional agricultural crops. Use of fertilizers,

pesticides, herbicides, and fungicides may be less

than conventional crops, depending on the particular energy crop grown and what it is being compared with; and use of diesel equipment will

decrease for planting and maintenance operations

compared with conventional crops but will increase for harvesting and transport due to the sheer

volume of material handled. Standard emissions

factors for diesel equipment are given elsewhere. 46

Energy crops such as HECs and SRWCs typically contain 6 to 18 times47 more energy than is

required to produce them and haul them to the

power plant or conversion facility. New power

plant technology will maintain or reduce most

emissions rates for biomass as compared with

coal, most notably for sulfur. Emissions factors for

renewable fueled (ethanol, methanol) transport are

more complex, depending on a variety of fuel

characteristics, the specific application, and other

factors. The increased emissions due to energy

cropping must also be compared with the potential

emissions changes-potential decreases in SOs

and NOX and increases in particulate and certain

organic compounds—in urban areas .48

HABITAT49

Wildlife have been broadly affected by agricultural activities. The most widespread problems are

a result of expanding cropping and grazing into

wildlife habitats, overgrazing riparian areas, and

agricultural activities that contaminate aquatic

habitats. Carefully designed and implemented, energy crops may moderate these impacts in some

circumstances, depending on the particular energy

crop, the previous land use, how the crop is managed, and which species are targeted. In other

cases, energy crops may have mixed impacts. Energy crops can not, however, substitute for natura150 habitat and are not intended to.

Early efforts to preserve species focused on

captive breeding of particular species, usually

those with considerable anthropomorphic appeal.

46 u s Environmen~] protection Agency, ‘{compilation of Air Pollution Emission Factors, VOI. 2: Mobile Sources,” AP-42, 19*5.

471n” ~ontra~t, the net energy b~~ce for current COrn to ethanol technologies ranges frOm break-even to 3 times more energy. ‘ee~ ‘or

example: Lee R. Lynd, Janet H. Cushman, Roberta J. Nichols, Charles E. Wyman, “Fuel Ethanol from Cellulosic Biomass,” Science, vol. 251,

March 15, 1991, pp. 1318-1323.

M u s Congress, Office of Technology Assessment, Ctltching Our Breulh: Next S~e~.~f~wReducing Urban o.z~me~ OTA-O-412 (Washington,

. .

DC: U.S. Government Printing Office, July 1989); Alan J. Krupnick and Paul R. Portney, “Controlling Urban Air Pollution: A Benefit-Cost

Assessment,” Science, vol. 252, Apr. 26, 1991, pp. 522-528; Jane V. Hall et al., “Valuing the Health Benefits of Clean Air,” Science, vol. 255,

Feb. 14, 1992, pp. 812–817; J.G. Calvert, J.B. Heywood, R.F. Sawyer, and J.H. Seinfeld, “Achieving Acceptable Air Quality: Some Reflections

on Controlling Vehicle Emissions,” Science, vol. 261, July 2, 1993, pp. 37-45; Mine K. Yucel, “Methanol As An Alternative Fuel: Economic

and Health Effects,” Economic Review: Federd Reserve Bank of Dallu.~, September 1991, pp. 9–20.

49 Michael L Wolfe, ~~potential Impacts of Energy -~dicated Biomass Production on Wildlife and Biological Diversity in the United States,”

contractor report prepared for the Office of Technology Assessment, Apr. 30, 1993; U.S. Congress, Office of Technology Assessment,

Technologies to Maintain Biological Diversity, OTA-F-330 (Wmhington, DC: U.S. Government Printing Office, March 1987); U.S. Congress,

Office of Technology Assessment, Technologies to Benejit Agriculture and Wildlfe—Work.dtop Proceedings (Wa..hington, DC: U.S. Government Printing Office, May 1985); James H. Cook, Jan Beyea, and Kathleen H. Keeler, “Potential Impacts of Biomaw Production in the United

States on Biological Diversity,’ ’AnnudReviewofEnergy mdthe Environment, vol. 16, 1991, pp. 401-431. See also: M.G. Paoletti, D. PimenteL

B.R. Stinner, and D. Stinner, “Agroecosystem Biodiversity: Matching Production and Conservation Biology,” Agriculture, Ecosystems and

Environment, vol. 40, 1992, pp. 3-23; Robert M. May, “How Many Species Are There on Earth?” Science, vol. 241, Sept. 16, 1988,

pp. 1441-1449. Elliott Norse, “Threats to Biological Diversity in the United States,” U.S. Environmental Protection Agency, Office of Policy,

Planning and Evaluation, EPA Contract #68-W8-0038, September 1990; “Toward Ecological Guidelines for Large-Scale Biomass Energy

Development,” Report of a Workshop convened by the National Audubon Society and Princeton University, May 6, 1991.

50 op. cit., fOOtnOte 1.
40 I Bioenergy

Although these efforts were partially successful,

scientists and policy makers have gradually recognized that the species which gain publicity are just

the tip of the iceberg (box 3-B), but are useful

icons in helping to save the less telegenic species

as well. Further, they have found that the more

effective means of saving all these species is not

through last-minute desperation efforts but rather

through conserving critical habitat for all the species in the region. Thus, attention has shifted from

species to habitats to regional landscape ecology.

The impact of agricultural, forestry, and other

land use practices on wildlife and habitat will first

be examined below. Lessons will then be drawn

from this experience, and applied to the potential

design and management of energy crops.

Agricultur e

As American settlers cleared forests and

plowed prairie land for cultivation, species that

were adapted to open areas prospered. The cottontail, bobwhite, crow, robin, red fox, skunk, and

meadow mouse, for example, benefited as forests

were opened to fields. Forest edge-loving species—”early successional” species—increased as

more of their favored environment was available,

but later declined as more forest was cleared,

leaving little but fields. Other species—particularly forest interior, wetland, and larger species

(such as wolves and bears) requiring larger home

ranges-could not adapt to the changed environment and have reduced ranges and dimished population sizes or have been displaced. There is some

disagreement as to the extent of the declines and

the causes for some species. Two principal causes

being examined for neotropical songbirds, for example, are tropical deforestation in Latin America

and changes in breeding grounds in North America.

As crop yields on sloping uplands decline with

erosion and fertility loss, farmers sometimes convert upland fields to pasture and drain lowlands for

crops. Wetlands drainage removes habitat for migrating and resident waterfowl, and can remove

the last remaining winter cover for some species

of wildlife such as pheasants. The removal of

fencerows and shelterbelts also reduces wildlife

habitat and, in turn, the wildlife that live there.

Modem agriculture has generally increased the

size of agricultural blocks and shifted from multiple crops to monoculture of just a few cash crops

(table 3-2). Larger fields have less fencerow for

habitat. Studies have found, for example, that five

times as many birds use the perimeter of cornfields

than use the center. Increasing field size is then

found to decrease bird abundance per unit area

logarithmically.

Field margins can also contribute to survival

and health of predatory insects as well as pollinat- 51For many predatory insects, how- ing insects.

ever, the crop type and presence of agricultural

residues plays a more important role.52 These insects, of course, reduce damage from pests on

crops.

Mechanization has led to the destruction of

nests in, for example, hayfields. More generally,

nesting activity is near zero in most conventional

agricultural row crops. Nearly all nesting activity

instead occurs in adjacent fencerows, shelterbelts,

and idle land.

Agricultural waste grains may benefit some

wildlife. For example, 80 percent of the U.S.

population of sandhill cranes depend heavily on

waste corn along the Platte River in Nebraska to

provide the energy they need to continue their

migration north.53 More generally, these grains

only supplement bird diets and, alone, may be

s] Jm Lagerlof, Josef Stark, and Birgitta Svensson, “Margins of Agricultural Fields As Habitats for Pollinating Insects,” Agriculture,

Ecosystems, and Environment vol. 40, 1992, pp. 117-124.

52 C.J.H. Booji and J. Noorlander, “Farming Systems and Insect Predators,“ Agri~ulture, Ecosystems and Environment vol. 40, 1992,

pp. 125-135.

53 James H. Cook, Jan Beyea, and Kathleen H. Keeler, “Potential Impacts of Biomass Production in the United States on Biological

Diversity,” Annual Review of Energy and Ihe Environment, vol. 16, 1991, pp. 401-431,
Chapter 3–PotentiaI Environmental Impacts 141

Box 3-B-What Is Biological Diversity?

Biological diversity refers to the variety and variability among living organisms and the ecological

complexes in which they occur. Diversity can be defined as the number of different items and their relative

frequency. For biological diversity, these items are organized at many levels, ranging from complete ecosystems to the chemical structures that are the molecular basis of heredity. Thus, the term encompasses different

ecosystems, species, genes, and their relative abundance; it also encompasses behavior patterns and

interactions.

Diversity varies within ecosystems, species, and genetic levels. For example:

. Ecosystem diversity: A landscape interspersed with croplands, grasslands, and woodlands has more

diversity than a landscape with most of the woodlands converted to grasslands and croplands.

. Species diversity: A rangeland with 100 species of annual and perennial grasses and shrubs has more

diversity than the same rangeland after heavy grazing has eliminated or greatly reduced the frequency

of the perennial grass species.

. Genetic diversity: Economically useful crops are developed from wild plants by selecting valuable

inheritable characteristics. Thus, many wild ancestor plants contain genes not found in today’s crop

plants. An environment that includes both the domestic varieties of a crop (such as corn) and the crop’s

wild ancestors has more diversity than an environment with wild ancestors eliminated to make way for

domestic crops.

Concerns over the loss of biological diversity to date have been defined almost exclusively in terms of

species extinction. Although extinction is perhaps the most dramatic aspect of the problem, it is by no means

the whole problem. Other aspects include consideration of species having large habitat requirements of

relatively pristine ecological condition, species whose movement is easily prevented with the slightest

anthropogenic changes in the landscape, unique communities of species, and many others. These are just a

few of the aspects of biological diversity that should be considered. Means of coping with these many aspects

of biological diversity in the context of our lack of knowledge of biological diversity are being developed. “Fine

filter” approaches deal with the potential loss of individual species; “coarse filters” focus on maintaining the

integrity of entire ecosystems. Energy crops may offer an additional tool at the regional landscape level to

assist such strategies.

SOUF?CE: U.S. Congress, Office of Technology Assessment, Technologies to Maintain Biological f)}versity, OTA-F-330

(Washington, DC: U.S. Government Printing Office, March 1987). For a more inclusive definition of biodiversity, see Allen

Cooperrider, “Conservation of Biodiversity on Western Rangelands,” Wendy E. Hudson, (cd.), Landscape Linkages and

Biodiversity, (Washington, DC: Island Press, 1991). For a discussion of fine filters and coarse filters, see: Kathryrt A. Kohm,

(cd.), Balancing on fheBtfnkof Extinction: The Endangered Species ActandLessons for the Future (Washington, DC: island

Press, 1991) [see especially the chapter by Malcolm Hunter); and Malcolm L. Hunter, Jr., Wildlife, Forests, and Forestry:

Principles of Managing Forests for Bio/ogicai CVversity(Englewood Cliffs, NJ: Prentice Hall, 1990).

nutritionally inadequate, especially for the devel- Forestr y

opment of nestlings and young birds.54 Conventional forestry management practices

The abandonment of farms can improve habitat have also had an impact on habitat and wildlife.

for wildlife as it regenerates natural vegetation, On industrially owned or managed lands, forestry

but the diversity of species is still greatly reduced management has generally focused on producing

from the original flora and fauna for long periods. a more uniform product, faster, and at higher pro54 Mj&e] L. Wolfe, “potential impacts of Energy -Dedi~ated Bionxm Production on Wildlife and Biological Diversity in the United Sbtes,”

contractor report prepared for the Office of Technology Assessment, Apr. 30, 1993.
42 I Bioenergy

Table 3-2—Major Cropland Usage, 1992

Area planted

Crop (million hectares)

Corn

Wheat

Hay

Soybeans

Other small grains

Cotton

Sorghum

Other field crops

Orchards

Vegetables

Total active

Idled

Short-term set-aside

Long-term set-aside (CRP)

Total cropland

Total pastureland

Total rangeland

Total agricultural land

30.8

25.9

25.5

23.5

7.7

5.7

4.9

5.3

2.0

1.6

132.9

13.8

7.7

14.2

170.4

53.9

164.4

388.7

SOURCE: Steven Shaffer, “Air Quality Impacts from Agriculture Biomass Production and Residue Utilization as Energy Feed Stocks,”

contractor report prepared for the Office of Technology Assessment,

May 13, 1993.

ductivity. This has often resulted in very large

stands of even-aged, rapid-growth single-species

forests. In contrast, natural forests more often consist of numerous species and a wide range of

habitats, ranging from climax forest to microopenings in the canopy where a large tree has

fallen and torn down the surrounding trees to large

openings following a fire.

Forestry management practices have a variety

of impacts on wildlife. Although early- and midsuccessional species may benefit, species that depend on old-growth or forest interiors do not.

Young, even-age stands of pine do not provide the

large volumes of acorns that older stands of oak

would provide as feed for a variety of animals; the

downed wood and forest floor litter used by many

species; nor the snags with nesting cavities used

by many birds and mammals (see box 3-C). For

example, some 20 species of birds in the southeastern United States use cavities for nesting, but

only 12 have ever been documented using pine

stands less than 50 years old. Patchwork harvesting also opens forest interiors, increasing the vulnerability of forest interior species to predators,

including cats, possums, raccoons, skunks, squirrels, etc., which prey on the birds and/or their eggs

and also encourages nest parasites such as the

brown-headed cowbird.55

Further, conifers contain relatively high levels

of compounds inimical to many insect herbivores;

and conifer needles are relatively acidic, reducing

the turnover of forest floor litter by invertebrates

and making the soil itself acidic, thus allowing

nutrients to leach out of the upper soil layers (see

soil quality, above). Nonconifer energy crops will

avoid this problem.

Together, these factors can reduce the richness

of insect, bird, and other species under modern

forest management. Use of nonindigenous tree

species may similarly reduce species richness.

There may be relatively few native species of

insects that can live off a nonindigenous species

and correspondingly few species of birds that can

then be supported.

Riparian Zones and Wetlands

Riparian—adjacent to surface water—zones

are particularly important habitat, but have been

extensively lost due to clearing for agriculture and

due to increased reliance on pumped irrigation

water rather than ditch-irrigation with its riparian

habitat. Compared with upland areas, riparian areas combine the basic resources of food, water,

and cover; they have greater structural and plant

diversity; they may have a wider range of microclimates for particular species; and they have

55 M c Brjttjngh~m and S.A. Te@e, “Have cowbirds Caused Fores[ Songbirds to Decline?” Bioscience, VO1. SS, lgs~, pp. ~l–ss; J.E.

. .

Gates and L.W. Gysel, “Avian Nest Dispersion and Fledging Success in Field Forest Ecotones,” Eco[ogy,” vol. 59, 1978, pp. 871–883; D.S.

Wilcove, “Nest Predation in Forest Tracts and the Decline of Migratory Songbirds,” Ecoh)gy, vol. 66, 1985, pp. 121 1–1214; Bill Lawren,

“Singing the Blues for Songbirds,” National Wildlve, August-September 1992, pp. 5-11.
Chapter 3–Potential Environmental Impacts 143

Box 3-C-What Is the Value of a Dead Tree?

Traditional forestry practices have generally looked upon dead trees-either standing or fallen-as an

economic loss, or a potential source of disease and insect infestation for the remaining stand, or a fire or safety

hazard, or an impediment to replanting or travel. They have consequently managed forests to ensure use of

as much of the biomass as possible and often burned the rest, leaving little behind. Research is now showing

that dead trees play a key role in forest ecology and forest health.

Snags--standing dead trees-provide hundreds of bird, mammal, reptile, and insect species habitat for

nesting, roosting, or foraging. At each stage in the decay of a snag, different species may make use of it. Birds

such as the red-breasted nuthatch prefer to nest at the top of relatively young (less than 20 years) snags.

Woodpeckers such as northern flickers prefer older snags both for the food they provide and for nesting. Other

species of birds as well as some bats may roost under the loose bark sloughing off older snags. Cavities in

the trunk may be used by a variety of birds as well as squirrels, bats, raccoons, and others. Where such snags

have been removed, there have often been corresponding declines in the populations of birds and other

animals dependent on them.

When a tree falls it continues to provide important habitat. Initially, a variety of wood-boring beetles tunnel

into the tree; with them come various fungi and bacteria that speed the decomposition process. They are

followed by various ants, termites, mites, centipedes, snails, salamanders, shrews, and others. The increasingly spongy tree serves as a nursery for new growth and holds large amounts of water to sustain this growth

through drought. In some areas, downed trees maybe the primary sites for establishing new growth.

Mycorrhizae fungi form symbiotic relationships with the roots of many plant species and aid nutrient uptake

by the roots. When their host dies, these fungi may die unless they encounter another host. Rodents such as

the California red-back vole eat these fungi and help to disperse their spores for attachment to new growth.

Removal of the rotting logs such rodents live in may hurt this virtuous cycle.

‘Trees that fall in streams similarly play a key role in aquatic habitats. The current of the stream tends to

scour a pool around the log, providing aquatic species protection from being washed down the stream during

high water and providing long-lasting pools during low water. Debris trapped behind the log decomposes and

provides important nutrients for aquatic species rather than being washed away by the current.

Finally, in some areas dead trees may provide as much as half of the important organic matter inputs into

the forest soil,

These ecological cycles may take centuries to become re-established in areas where traditional forest

practices have cleared the land and burned the slash. The issue is not stopping use of timber, but rather how

to use the insights from these ecological studies to improve forest health and productivity for both people and

the many other species that use forest resources.

SOURCES: M.G. Raphaei and M. White, “Use of Snags by Cavity Nesting Birds in the !%8rra-NevadtI Catifomk%” Wlk#//@

Mono~rqXwvol. 86,1984, pp. 1-66; V.E. Scott, “Bird Respon$8to Snag Removal in Ponderosa P\ne,” Jouma/ufFor@@~,

VOI, 77, 1979, pp. 26-28, J.W. Thomas, R.G. Anderson, (’2 Maser, and E.L. Bull, “Snags: in Thomas, (sd.), 197$;

Habitatskt ManagedFores/s: The131uefWJuntainsof Oregon and Washington, USDA Forest Servic@Agricultural bkm!fbook

No. 553, Washington, D.C.; Jerry Franklin, ‘?oward a New Forestry,” Arneticen Forests, vol. 95, No. 11-12, NoverribsrDecember 1989, pp. 3745; James H. Cook and Jan Beyea, “Potential Impacts of Biomass Production in th@ United States

cm Bic)fogical Diversl~,” Annaa/Reti&wof Energyar?d Environment, VOL 16, 1991, pp. 401-431; Jon I% Luwna, “An Untidy

Wonder,” Discover, October 1992, pp. 86-95; Catherine DoId, “Study Casts Doubt on Betief In S@lf-R@vlvai uf Cleated

Forests: New York Times, Sept. 1,1992, p. C4; Jane E, Brody, “In Spring, Nature’s Cycle Brings a D@adTree to lifa~ hfew

York Times, Mar. 24,1992, p. Cl; Jennifer Ackerman, “when the Bough Breaks: Naturt? Conservancy, May/Jun6! 19fW,

pp. 8-9.
44 I Bioenergy

extended edges. These areas also play a critical

role in protecting water quality—filtering runoff

of sediment and agricultural chemicals, moderating stream temperatures, providing woody debris

important for a variety of aquatic habitats, and

providing food.

Wetlands are some of the earth’s most productive ecosystems. They play a key role in supporting certain fish and shellfish during portions of

their lifecycle, helping support more than 400 of

some 800 species of protected migratory birds,56

and in other areas, even providing some species of

salamanders temporary (vernal) pools for breeding (year-round pools would support fish that

would eat the salamander eggs and young).

Large water projects-dams, canals, irrigation—are the most obvious source of riparian

habitat loss or degradation, but land use changes

due to agriculture, timber harvesting, road building, development, and others are the most widespread and perhaps, overall, the most damaging.

Impacts include increased silt and organic matter

in water, changes in temperature, acidity, salinity,

shading, flow rates, etc., and other factors. Maintaining even a small amount of stream bank forest

can greatly reduce these impacts. Chemical and

organic pollution is also due in large part to agricultural activities, now that industrial sources and

city sewage are better controlled. In fresh water,

fish, amphibians, mollusks, crayfish, insects and

many other invertebrate phyla, and plants may be

imperiled; a number are already extinct.57

The loss of structural diversity has similarly

been detrimental for habitat in rangelands and

elsewhere; details can be found elsewhere .58

Energy Crops and Habitat

The brief review above of the impact of agriculture, forestry, and other activities on wildlife

habitat offers a variety of lessons for designing

energy crops. Properly designed, energy crops can

be used to manage or direct the regional landscape

ecology—potentially serving as buffers around

natural habitat, as corridors between fragments of

natural habitat, or as habitat in themselves. How

effectively the energy crop serves these roles depends on the particular crop, how it is managed

(including use of chemicals, equipment, and harvesting cycle), and how the species it is designed

to assist respond. There is very little field data to

base conclusions on at this time; instead, the analysis here is based largely on theoretical models and

of observations of wildlife interactions with other

crops and altered habitats.

Energy crops are not, however, a substitute for

natural habitat. Instead, they represent a compromise. In terms of habitat value, it would be preferable to let much of the idled crop land or other

lands return to a natural state. Should global warming occur as currently projected, however, much

of the habitat in the United States and elsewhere

may be subject to sufficiently rapid climate change

that the species/habitat that was intended to be

protected may be unable to adjust or move quickly

enough for the changed circumstances (figure 3-

2). To avoid this, and more generally out of concern for potential global warming, it may be

preferable to use idled crop land to produce greenhouse gas neutral 59 biomass energy. Energy crops

are therefore of particular interest to the extent that

they can be designed as a compromise between

habitat concerns and greenhouse gas concerns.

56 Douglas A. Thompson am! Thomm G. YOCOm! “Uncertain Ground,” Technology Review, August/September 1993, pp. 20-29.

ST J David A] Ian and A]exander S. Flecker, “Biodiversity Conservation in Running Waters,” Bioscience, vol. 43, No. 1, January 1993,

pp. 32-43.

58 Michae] L. Wolfe, ~~potentia] Impacts of Energy .Dedicated Biom~s Production on Wildlife and Biological Diversity in the United States,”

contractor report prepared for the Office of Technology Assessment, Apr. 30, 1993.

59 If fossi]-fuel-ba$ed agficultura] ~hemica]s, fe~i]izers, or ~anspofi fue]s are used, bioenergy is not strictly greenhouse gas neutra]. Typically,

however, the net energy return (or greenhouse gas equivalence) is 6 to 18:1 for biomass energy to fossil energy inputs. This is for HECS and

SRWCS. In contrast, current corn to ethanol production has much lower net energy gains.
Chapter 3–Potential Environmental Impacts 145

Figure 3-2—Present geographic range of beech (horizontal lines) and potentially suitable range under

doubled CO2 (vertical lines) for two different climate models

.-. ?s) -. -....,

/

“\..

o 400 km 1

A

f \

$9 “--------

o

Y

o 400 km

A_l

B

These figures show the dramatic shift northward in the suitable range of a particular species. Although the two models disagree in the precise details,

the overall extent of the shift predicted is similar.

SOURCE: Robert L. Peters and Thomas E. Lovejoy, (eds.), G/oba/ Warming arrd Bio/ogica/ Diversify(New Haven, CT: Yale University Press, 1992).

Understanding of biological diversity is grow- of species present) and the species evenness (the

ing rapidly, from simple concepts of species relative number of different species); and the time

counts, to appreciation of the entire ecosystem and scale.

all the varied behavior patterns and interactions of In general, the more complex the vegetation

its components. The ecology of a given region is (with many species, sizes, shapes, and ages of

determined by a number of factors, described plants) in an area, the more complex the commubroadly as the physical environment and species nity of animals—insects, 60 spiders, 61 birds, 62

composition. mammals, 63 etc.—it will support. Conversely, as

Three factors affecting biological diversity will vegetative structure is simplified, the community

be considered here: the relative structural com- supported becomes progressively poorer. For explexity of the ecological system; the species diver- ample, the number of insect species in typical

sity—including the species richness (the number agricultural ecosystems such as corn can be half

m DR. Strong, J.H. ~wton, R. Southwood, ]n.reel.~ on Plants, (Oxford: Blackwell Scientific Publications, 1984).

c1 C.L. Hatley and J.A. MacMahon, “Spider Community Organization: Seasonal Variation and the Role of Vegetation Architecture,”

Environmental Entomology, vol. 9, 1980, pp. 632-639.

62 RHO MacAflhur and J,W. McArthur, “on Bird s~cies Diversity,” Eco/ogy, vol. 42, 1961, pp. 5$)4-5$)8; G.s. Mills, J.B. Dunning, Jr.,

and J.M. Bates, “The Relationship Between Breeding Bird Density and Vegetation Volume,” Wilson Bulletin, vol. 103,1991, pp. 468-479.

63 M. Rosenzweig and J.win&ur, ~fpopulation Eco]o~y of ~Sefi Rodent Communities: Habi~@ and Environmen~] Complexity,” EcoIogy,

vol. 50, 1966, pp. 558–572; R.D. Dueser and W.C. Brown, “Ecological Correlates of Insular Rodent Diversity,” Ecology vol. 61, 1980,

pp. 50-61.
46 I Bioenergy

that found in pasture and one-third to one-tenth

that found in deciduous forests.

64 It is the structural poverty of conventional agricultural monoculture that opens an opportunity for energy crops

to improve habitat and biological diversity in a

region.

Species richness and evenness are also important. In many cases, only the number of different

species are listed without considering the number

of individuals per species and whether it is sufficient to maintain a viable population, particularly

in terms of genetics. Many believe that the goal of

management should not be to maximize the number of species in a given area, but rather to ensure

the conservation of threatened species and ecosystems.65 

. After that is assured, the focus might turn

to improving the conditions for less imperiled

species and ecosystems.66

Finally, the time scale plays a key role. When a

naturally forested area, for example, suffers a fire,

a series of different plants—grasses, shrubs, small

trees-colonize the area as it gradually regenerates back to full forest. Each of these plant ecosystems supports a different set of animals. This

process is known as succession. Some animals,

such as robins, field mice, rabbits, deer, etc., arrive

early in the process. They thrive in the mixed

forest-meadow habitat. Others prefer the low

bushes and small trees of mid-succession. Still

others require late succession or climax forest.

Energy crops tend to favor the early- to mid-successional species, but may be designed to provide

adequate habitat for mid- to late-successional species. This can be accomplished by leaving inclusions of old-growth vegetation within the energy

crop area and by other means, such as artificial

nesting structures, where necessary.

Energy crops can be designed to reduce many

of the detrimental impacts on habitat and wildlife

of conventional agriculture and forestry (see

box 3-D). Energy crops may also serve as buffers

around or corridors between fragments of existing

natural habitat. So designing energy crops, however, involves numerous complex interacting factors that have been little studied in the context of

energy cropping but which can be examined by

analogy with fundamental principles of ecology

and studies of agricultural, managed forest, and

natural ecosystems. Four key issues will be examined here:

■ the impact of habitat fragmentation;

■ the potential of energy crops as buffers around

fragments of habitat;

■ corridors between fragments of habitat; and

■ the impact of energy crop field operations.

Although plant genera native to the region are

preferable, nonindigenous species with particularly favorable characteristics may be brought in

under some circumstances. Especially versatile

species—both herbaceous and woody-include

hybrid poplar, black locust, eucalyptus, silver

maple, switchgrass, sycamore, sweetgum, reed

canary grass, salix (willow), sesbania, and leucaena.

67 Some nonindigenous species may, however, be able to escape cultivation and displace

native vegetation or degrade wildlife habitats.

Once established they become very difficult to

eradicate.

Habitat Fragmentation

The natural landscape has become highly fragmented with several adverse impacts on species.

As the area of habitat decreases, the number of

different species it can support decreases. A single

grizzly bear, for example, may need 75 km2 of

roadless land. On average, as the area of habitat is

64 David pjmentel et a]., “conserving Biological Diversity in Agricultural/Forestry SYstemss” Bio.$cienee, vol. 42, No. 5, May 1992,

pp. 354-362; M.G. Paoletti, D, Pimentel, B,R. Stinner, D. Stinner, “Agroecosystem Biodiversity: Matching Production and Conservation

Biology,” A~riculture, Ecosystems md IZnvir(mment, vol. 40, 1992, pp. 3–23.

65 James wJ, McMinn, “Bio]ogica] Diversity Research: An Analysis,” U.S. Department of Agriculture Forest Service, Southeastern Forest

Experiment Station, Asheville, NC, General Technical Report SE-71, September 1991.

~~ There continues t. be debate about whether this or some other approach is the best strategy to follow.

071 Stjemquist, “Modem Wood FuelS~ “ Bi(jenergy mud /he Environment (Boulder, CO: Westview Press, 1990), pp. 61-65.
Chapter 3–Potential Environmental Impacts 147

Box 3-D-Prototype Ecology-driven Guidelines for Structuring Energy Crops

Plant species under consideration for use as bioenergy crops are primarily native species that evolved

in the regions where they maybe used. These crops can provide greater structural diversity on a landscape

level than typical agricultural crops, and thus can enhance wildlife habitat. The extent to which such habitat

benefits are realized, however, depends on the careful application of ecological principles, as outlined in

prototype guidelines below. These guidelines, however, should be considered only a starting point, requiring

much further research. Further, these guidelines are based on principles drawn from studies of natural

ecosystems and of highly simplified agricultural systems; there is little or no empirical data for energy crops

themselves. Conducting dedicated field-trial research on the ecological interactions of natural systems with

energy crops would be useful in order to guide the development of large-scale energy cropping.

Ecology-driven guidelines for structuring energy crops might include the following:

• Site. Energy crops should be concentrated on current, idled, or former agricultural, pasture, or other

“simplified” or “marginal” lands. Energy crops should not be grown on naturally structured primarygrowth forest land, wetlands, prairie, or other natural lands.1

● Species. Energy crops should combine two or more species in various ways in order to improve species

diversity. This would preferably include the use of leguminous species or others with nitrogen-fixing

capabilities to reduce the need for artificial fertilizers, and other combinations to reduce potential losses

from disease or insects and thus reduce pesticide use. Non-invasive species which will not escape

from cultivated plots are also preferred.

. Structure. Energy crops should combine multiple vegetative structures to enhance landscape diversity

as needed by particular species. This could include various combinations of short-rotation woody crops,

perennial grasses, and other dedicated energy crops, leaving small to large woody debris and other

ground cover, as well as inclusions of natural habitat, as needed. These energy crops could also be

used to provide structure to conventional agricultural monoculture through the addition of shelterbelts

and fencerow plantings. Similarly, monoculture of energy crops should have shelterbelts or fencerows

of other types of vegetation.

Ž Lifetime. Landscape structure can also be made more diverse by harvesting adjacent stands on

different rotation cycles, including leaving some stands for much longer periods, if possible.

• Non-indigenous species. Energy crops should use locally native species to the extent possible. Native

species or close relatives will harbor richer insect and other faunas.

• Chemicals. Crops should be chosen to minimize application of agricultural chemicals such as

herbicides, insecticides, fungicides, and fertilizers, as discussed above.

Ž Unique features. Unique habitats and features such as small natural wetlands, riparian or other

corridors, “old-growth” incisions, and shelterbelts should be preserved and enhanced by the energy

crop.

• Habitat assistance. Artificial nesting structures and other additions to or supplements of habitat

features should be provided where appropriate.

Ž Research. Energy crops should be studied carefully at all appropriate scales and on a long-term basis

to better understand the best means of improving appropriate habitats for desired species, both for the

energy crop itself as well as for related agricultural, managed forest, and natural lands. This should

also be done on a regional basis, as appropriate.

SOURCE: Adapted from: Michael L. Wolfe, “Potential Impacts of Energy-Dedicated Biomass Production on Wildlife and

Biological Diversity in the United States,” contractor report prepared for the Office of Technology Assessment, Apr. 30,

1993; and from the discussion at the “Workshop on Environmental Impacts of Bioenergy Crops,” Office of Technology

Assessment, May 13, 1993.

loefining “natural habitat” maybe difficult and controversial because the paSt decades to centuries of, for example! clear

Mting, selective harvesting of economically valuable trees, and fire suppression have altered many U.S. forests, often

leading to an increased concentration of plant species with lower economic or ecological value. Similar alterations have

ocurred over many other U.S. landscapes, including prairie and wetiands. Although defining how much modification still

qualifies as “natural” is thus challenging, the term will be used broadly hereto include all lands that support a significant

quantity and variety of indigenous plants and animals. For this report, only current or former agricultural lands or highly

degraded lands are considered for energy crops.
48 I Bioenergy

decreased by a factor of 10, the number of species

it can support is reduced by a factor of two. As the

habitat area decreases, the number of individuals

of a particular species decreases. Inbreeding increases, and the local population also becomes

increasingly vulnerable to a single catastrophic

event such as a fire or flood.

Fragments of habitat also have large edge effects. Changes in the type of vegetation, wind

speeds, moisture, and other factors can modify the

forest interior habitat for 20 to 200 meters or more

into the forest.

68 The effective forest interior is

then reduced proportionately, depending on the

size of the forest fragment and the particular plant

or animal species considered. For example, a 5-ha

stand might effectively be all edge-like habitat,

based on the vegetative structure and species supported. As the forest edge allows a variety of

predators greater access to the wildlife inside,

forest fragments may be affected even more than

by the 20 to 200 m of edge effects alone.

Buffers

Energy crops may usefully provide habitat for

some species. Perhaps as important, they might be

useful to help isolate fragments of natural habitat

from the disturbances described above. For example, if a wide strip of short-rotation wood-energy

crop surrounded a 100-hectare fragment of natural

habitat, it would reduce the edge effects described

above. Forest interior species might then be able

to use the habitat up to or even into the energy crop

buffer. Instead of 10 ha of habitat, the effective

area would be increased to 100 ha. In addition,

predation may be reduced, although this is controversial and requires field verification.

For example, initial observations have found

SRWC poplar plantations to provide substantial

habitat value for birds, depending on the particular

species, the age of the particular stand, and proximity to native habitat. From these studies, it appears that older SRWCs are more forest-like than

field-like for many species. At younger ages or

following harvest, however, it appears that

SRWCs are more like old field and edge habitat.69

Corridors 70

Energy crops might also serve as corridors between fragments of natural habitat, providing a

protected habitat for wildlife traversing them. Corridors do not have to supply all of the necessities

of life for a species using it, just those needed as

the species moves along the corridor between

patches of habitat; providing additional ecosystem

services is desirable, but not essential. Corridors

have become much discussed, but there is as yet

little field data on how to design them for different

species or on their overall effectiveness. Corridors

that are effective for one species, such as bear,

might actually harm another species such as salamanders-enticing them out of one fragment of

habitat, but leading them to their death before

reaching the next fragment. Corridors aiding the

movement of desired species may also aid the

movement of nonindigenous or undesirable species, potentially increasing the risk to those spe68 B]air Csuti, “In~oduction: Consemation Corridors-Countering Habitat Fragmenmtiom” Wendy E. Hudson (cd.), Ladcape Linkages

and Biodiversity (Washington, DC: Island Press, 1991); J. Ranney and M. Bruner, “Forest Edge Dynamics in Man-Dominated Landscapes”

Mun-Dominated Landscapes (Spnnger-Verlag, 1978).

@ Wayne Hoffman, Nationa] Audubon Society, presenbtion at the Office of Technology ASSeswnent workshop, May I ~~ 1993; See ~so

Wayne A. Hoffman, James H. Cook, and Jan Beyea, “The Habitat Value of Short-Rotation Poplar Plantations: Avian Population Studies and

Management Alternatives,” Draft.

70 As used here, ‘c

orridors” refers t. landscape features that he]p a particular species move between patches of habi~t; it does not refer to

utility rights-of-way, recreational greenways, or other such systems designed primarily to meet human requirements, although they may

incidentally help wildlife. Literature on wildlife corridors is growing rapidly. See, for example: Wendy E. Hudson (cd.), Lundscape Linkages

and Biodiversity (Washington, DC: Island Press, 1991); Jon E. Rodiek and Eric G. Bolen, (eds.), Wildll~e and Habitats in Managed Landscapes

(Washington, DC: Island Press, 1991); Michael L. Wolfe, “Potential Impacts of Energy-Dedicated Biomass Production on Wildlife and

Biological Diversity in the United States,” contractor report prepared for the Office of Technology Assessment, Apr. 30, 1993.
Chapter 3–Potential Environmental Impacts 149

cies that were targeted for help. Finally, a forest

corridor that helps the movement of a forest species may be a barrier to a meadow species .7] Thus,

a corridor may act as a filter, allowing the passage

of some species and not others.

Corridors may serve three broad needs: to aid

periodic migrations to reproduction sites; to allow

foraging, roosting, or following seasonal food or

other resources; or to allow occasional migration

to ensure the continued viability of small isolated

populations. 72

Corridors must reflect the needs of their target

species. Long corridors can be used only for fastmoving species. A 10-km-long corridor might easily support various species of birds, but not

frogs—particularly if hungry racoons are prowling. A narrow corridor might be satisfactory for

some species, but not for those which require the

temperature, moisture, and other conditions of the

forest interior. A narrow corridor may also increase predation. Many predators—ravens, jays,

raccoons, house cats, etc.—prefer to forage where

they can see and move most freely, near the edge

of a forest. Species traversing a narrow corridor

may then be running a gauntlet. On the other hand,

wide corridors may not help some species as they

will simply wander around in them, moving to the

next patch of habitat only slowly at best.73

These are just a few of many factors that must

be taken into account when designing energy

crops to serve as buffers or corridors. Other factors

must be considered as well, including the minimum viable area required to support a population

of a species, species composition, ecosystem

structure and function, and many others. These

factors are as yet poorly understood and need

detailed field trials to understand more fully these

many complex interactions.

Field Operations

Finally, it is useful to consider the practice of

energy cropping. For all energy crops, the timing

of harvesting will have to be done to minimize

interference with nesting or other key lifecycle

activities of particular species. Bird reproduction

rates, for example, are best on lands that remain

undisturbed for at least three to five years or more.

Harvesting should also leave sufficient cover for

winter, for protection from predators, and for

spring nesting activities.

Ground cover for wildlife is important in both

herbaceous and woody crop systems. Woody debris, for example, increases the structural diversity

of the site. Logs can serve as lookout sites; for

nesting inside, alongside, or underneath; for courtship displays (certain grouse species); for food

storage sites; or for food (insects for birds, mushrooms for red squirrels, etc.). Small mammals

living inside decaying logs play a role in supporting coniferous forests by helping disperse the

spores of mycorrhizal fungi which form an important symbiotic relationship with conifer roots and

improve root function. Larger logs generally serve

many of these functions better than small logs or

woody debris. Box 3-C described some of these

roles of dead trees in more detail.

Of course, all of these factors will have to be

weighed against the economics of energy crop

harvesting. The logistics and economics of harvesting small or irregular areas may limit use of

such approaches to provide energy feedstocks.

71 Reed F. No~~, ~~~ndscaP connectivity: Different Functions at Different scales>” Wendy E. Hudson (cd.), Lundscape Linkages and

Biodiversity (Wmhington, DC: Island Press, 1991).

72 Michael E, Soule, “Theory ~d Strategy,” Wendy E, Hudson (cd.), Lmdscwpe Linkqes and Biodiversio (Washington, DC: Island press>

1991).

73 Michael E. sou]e, ~~Theov ~d strategy,” Wendy E, Hudson (cd,), ~4nd.~~(/pe Li&/ge,~ ~lnd Biodiver.Yify (Wa..hington, DC: Island pESS,

1991 ).
50 I Bioenergy

Table 3-3-Sources of Greenhouse Gases

Greenhouse Gas Principal Sources

Carbon dioxide Fossil-fuel combustion

Deforestation, land use changes

Cement production

Methane Fossil-fuel production (coal mines, oil and gas wells, gas pipelines)

Fossil-fuel combustion

Landfills

Rice cultivation

Animal husbandry

Biomass combustion and decay

Synthetics used in refrigerators and air conditioners

Used in manufacturing processes as blowing agent, cleaning agent

Fertilizers

Fossil-fuel combustion

Biomass combustion

Deforestation and land use changes

Chlorofluorocarbons

Nitrous oxide

Adapted from: Michael Grubb, Energy Policies and the Greenhouse Effect, Volume tie: Policy Appraisal, (Aldershot,

Hants, England: Dartmouth Publishing Company, 1990); and Dilip R. Ahuja, “Estimating Regional Anthropogenic

Emissions of Greenhouse Gases,” Forthcoming, T.N. Khoshoo and M. Sharma, (eds.), The Indian Geosphere

Biosphere, (New Delhi, India: Vikas Publishing House, 1991).

GREENHOUSE GASES74

The environmental impacts described above are

largely limited to the local rural region. Some

activities—notably, the production and use of fossil fuels-can have a wider impact, including

impacts on the global climate through the “enhanced” greenhouse effect.

The “natural” greenhouse effect is a well-established scientific fact. In the absence of the natural

greenhouse effect, the average surface temperature of the earth would be –18 “C instead of the

actual +15 oC. This +33 OC increase in average

surface temperature is due to the presence of naturally occurring greenhouse gases—principally

water vapor, carbon dioxide, and methane. Today,

increases in atmospheric concentrations of these

and other greenhouse gases due to the burning of

fossil fuels, deforestation, and other human-induced changes in the biosphere are leading to an

enhancement of this naturally occurring greenhouse effect. Table 3-3 lists some of the leading

sources of these greenhouse gases and table 3-4

some of their key parameters. A recent review by

over 200 leading scientists from 25 countries (the

InterGovernmental Panel on Climate Change—

IPCC) estimated that this increase in greenhouse

gas concentrations will raise the average surface

temperature of the earth (box 3-E).

Based on current models and under “Businessas-usual” scenarios, the IPCC scientists predict

that global mean temperature will increase at a rate

of about 0.3‘C per decade during the next century,

a rate higher than that seen over the past 10,000

years.

75 This would mean a nearly 1 O

C increase

7A u,s, Congress, Office of Technology Assessment, Cizanging by Degrees: Steps to Reduce Greerdwwe Gases, OTA-O-482 (WaSh@ton,

DC: U.S. Government Plinting Office, February 1991); Intergovernmental Panel on Climate Change, Scientific Assessment of Climate Change,

Sumnuny and Report, World Meteorological Organization/U.N. Environment Program (Cambridge, United Kingdom: Cambridge University

Press, 1990); Michael Grubb, Energy Policiesandthe Greenhouse Effect, Volume One: PolicyApprui.ral(Aldershot, Hants, England: Dartmouth

Publishing Co., 1990); Intergovernmental Panel on Climate Change, “Policymakers Summary of the Potential Impacts of Climate Change:

Report from Working Group H to the IPCC,” May 1990; J,T, Houghton, B.A. Callander, S.K. Varney (eds.) Climute Change 1992: The

Supplementary Report on tile IPCC Scientific Assessment (Cambridge, United Kingdom: Cambridge University Press, 1992).

75 Very recently, evidence has emerged that past c]imate changes have also sometimes been quite rapid. See, for example: Richard A. Kerr,

“Even Warm Climates Get The Shivers,” .$cience, voi. 261, Juiy 16, 1993, p. 292.
Chapter 3–Potential Environmental Impacts 151

Table 3-4-Parameters for Key Greenhouse Gases

C02 CH4 CFC-11 CFC-12 N20

Atmospheric concentration

Pre-industrial, 1750-1800

Present day, 1990

280 ppmv 0.8 ppmv o pptv o pptv 288 ppbv

353 ppmv 1.72 ppmv 280 pptv 484 pptv 310 ppbv

0.015 ppmv

(0.9%)

10

9.5 pptv

(4%)

65

17 pptv

(4%)

130

0.8 ppbv

(0.25%)

150

Current annual rate of change 1.8 ppmv

(0.5%)

Atmospheric lifetime (years) (50-200)’

Global warming potential relative to carbon

dioxide for today’s atmospheric composition:

Instantaneous potential, per molecule

20-year time horizon, per kg

100-year time horizon, per kg

500-year time horizon, per kg

1

1

1

1

21

63

21

9

12,000

4,500

3,500

1,500

270

290

190

7,100

7,300

4,500

Contribution to radiant forcing,

1765-1990

1980-1990

2 3 %

1570

2.5%

5 %

5.7%

12%

4.1%

6%

61%

55%

Reduction required to stabilize concentrations

at current levels 6 0 % 15-20% 70-75% 75-85 % 70-80 %

KEY: ppm(b,t)v = parts per million (billion, trillion) by volume

● Carbon dioxide absorption by the oceans, atmosphere, soils, and plants cannot be described by a single overall atmospheric lifetime.

SOURCE: Intergovernmental Panel on Climate Change, Scientific Assessment of Climate Change, Summary and Report, World Meteorological

Organization/U.N. Environment Program (Cambddge, United Kingdom: Cam bddge University Press, 1990).

over present-day global average temperatures by

2025 and a 3 ‘C increase by 2100. In addition to

increases in mean global temperature, other effects expected to occur with increases in atmospheric concentrations of greenhouse gases

include: increases in sea level,76 and shifts in

regional temperature, wind, rainfall, and storm

patterns. These changes, in turn, are expected to:

■ submerge low-lying coastal areas and wetlands,

and increase the salinity of coastal aquifers and

estuaries;

■ impact human-built structures;

shift a variety of vegetation zones (or destroy

them if they can not move quickly enough)77

and species ranges;

alter plant metabolisms and productivities; and

have a variety of other effects.

More recent studies have generally reaffirmed

these findings78 and raised even more serious concerns about the potential climate impacts beyond

the year 2100.79 The potential impact of and

means of adapting to climatic change is the subject

of a separate OTA study.80

76 The IpCC working group predicted an average rate of giobal mean sea level rise of about 6 cm per decade over the next century) 20 Cm

by 2030 and 65 cm by the end of the century with significant regional variations. This increase is primarily due to thermal expansion of the

oceans and melting of some iand ice.

77 Diffe~nt Plmt sPcies migrate via different nlech~isms, some through dispersal of airborn seeds, others via animal-borne seeds, etc.

These different modes of seed dispersal result in different time lags for a species to move. Typical rates are 30 km per century; with projected

global warming, dispersal rates needed are 10 times greater.

78 Intergovemmntal panei on Climate Change, J.T. Houghton, B.A. Callander, S.K. Vamey, (eds.), Cliwte Ctin~e Z992: The supplementary Report m the IPCCScientiflc A.we.wrnent (Cambridge, United Kingdom: Cambridge University Press, 1992).

79 Syukuro Mana~ and Renal J. Stouffer, “CentuV-Sca]e Effects of Increased Atmospheric c02 on the Ocean-Atmosphere SYStem!” ‘atureI

vol. 364, 1993, pp. 215-218.

~~ U.S. CongESS, office of Technology Assessment, Preparingforan Uncertain Climate, fofihcoming.
52 I Bioenergy

Box 3-E-Highlights of the Intergovernmental Panel on Climate Change 1990 Scientific Assessment

Several hundred scientists from 25 countries prepared and reviewed the scientific data on climate change

under the auspices of the World Meteorological Organization and the United Nations Environment Program.

This Intergovernmental Panel on Climate Change summarized their findings as follows:

The IPCC is certain that:

• there is a natural greenhouse effect which already keeps the Earth warmer than it would otherwise be.

• emissions resulting from human activities are substantially increasing the atmospheric concentrations

of the greenhouse gases: carbon dioxide, methane, chlorofluorocarbons (CFCs) and nitrous oxide.

These increases will enhance the greenhouse effect, resulting on average in an additional warming of

the Earth’s surface. The main greenhouse gas, water vapour, will increase in response to global warming

and further enhance it.

The IPCC calculates with confidence that:

. atmospheric concentrations of the long-lived gases (CO2, N20, and the CFCs) adjust only slowly to

changes in emissions. Continued emissions of these gases at present rates would commit us to

increased concentrations for centuries ahead. The longer emissions continue to increase at present-day

rates, the greater reductions would have to be for concentrations to stabilize at a given level.

. the long-lived gases would require immediate reductions in emissions from human activities of over

60 percent to stabilize their concentrations at today’s levels; methane would require a 15 to 20 percent

reduction.

Based on current model results, the IPCC predicts that:

. under the IPCC Business-As-Usual Scenario, global mean temperature will increase about 0.3 OC per

decade (with an uncertainty range of 0.2 to 0.5‘C per decade); this is greater than that seen over the

past 10,000 years. This will result in a likely increase in global mean temperature reaching about 1 OC

above the present value by 2025 and 3 ‘C before the end of the 21st century,

. land surfaces will warm more rapidly than the ocean, and high northern latitudes will warm more than

the global mean in winter.

• regional climate changes will differ from the global mean, although our confidence in the prediction of

the detail of regional changes is low. Temperature increases in Southern Europe and Central North

America are predicted to be higher than the global mean, accompanied on average by reduced summer

precipitation and soil moisture.

. global mean sea level will rise about 6 cm per decade over the next century, rising about 20 cm by 2030

and 65 cm by the end of the 21st century.

All predictions are subject to many uncertainties with regard to the timing, magnitude, and regional

patterns of climate change due to incomplete understanding of:

• sources and sinks of greenhouse gases,

Ž clouds,

• oceans, and

. polar ice sheets.

These processes are already partially understood, and the IPCC is confident that the uncertainties can be

reduced by further research. However, the complexity of the system means that surprises cannot be ruled out.

The IPCC judgment is that:

 • Global mean surface air temperature has increased by 0.3 to 0.6 ‘C over the last 100 years, with the

five global-average warmest years occurring in the 1980s. Over the same period global sea level has

increased by 10-20 cm.

● The size of this warming is broadly consistent with predictions of climate models, but it is also of the

same magnitude as natural climate variability. Thus, the observed temperature increase could be largely

due to natural variability; alternatively, this variability and other human factors could have offset a still

larger human-induced greenhouse warming, The unequivocal detection of the enhanced greenhouse

effect from observations is not likely for a decade or more.

SOURCE: World Meteorologkxil Organization, U.N. Environment Program, intergovernmental Panel on Climate Change, Scientific

Assessment of Cfiinate Change, SwrvnaryandRepo rt(Carnbridge, United Kingdom: Carnbtidge University Press, 1990).
Chapter 3–Potential Environmental Impacts 153

In 1985, according to estimates for the IPCC

Working Group III, three-fourths of annual global

energy sector CO2 emissions came from the industrialized market countries and the centrally

planned European countries (including the former

U.S.S.R.); about 20 percent came from the United

States.

Controlling these emissions would slow potential global warming. Emission control strategies

that countries could consider today include improved energy efficiency and cleaner or nonfossil

energy sources. These strategies may also have

economic benefits. Biomass energy could play an

important role in such strategies.

Biomass as a Carbon Sink or Offset

Biomass can be used as a carbon sink or, more

significantly, as a fossil fuel offset in order to slow

the increase in atmospheric concentrations of

carbon dioxide due to fossil fuel combustion. The

potential contribution of biomass energy crops to

other greenhouse gases, such as methane and nitrous oxide, and the potential impact of biomass

energy crops on soil carbon balances should also

be considered.

81 Only the direct carbon impacts

will be considered here.

As a carbon sink, biomass is grown to absorb

carbon dioxide from the atmosphere—which is

then incorporated into the plant itself—and the

biomass is then possibly put into some form of

long-term storage. Storage options range from

simply increasing the standing volume of trees,82

to greater use of wood as a building material,83 to

harvesting the biomass so that more can be grown

and storing it in dedicated sites.

These carbon “sequestration” strategies suffer

several shortcomings. There is often little economic return from the sequestered biomass and

generally an economic cost;84 and if the biomass

is left standing, the amount of biomass that can be

sequestered is limited by the maturing of the tree.

As a fossil fuel offset, biomass can be used as

a fuel in place of coal, oil, or natural gas. 85 If grown

on a renewable basis, biomass makes almost no

net contribution to rising levels of atmospheric

86 In addition, biomass energy carbon dioxide.

crops may provide a net increase in soil carbon as

well as in standing biomass, depending on the

previous use of the land.

87 Biomass can be burned

directly to power steam boilers or gasified to

power gas turbines coupled to electric generators.

Biomass can also be converted to ethanol or

methanol and used to fuel transport. In the longer

term, hydrogen derived from biomass may be a

valued alternative fuel.

Growing, harvesting, transporting, and processing biomass as a fossil fuel offset make this an

initially more costly strategy than carbon sequestration—i.e., simply growing trees. Sale of the

biomass energy partially compensates for these

81 Energy crops Wi]l ~so tend to increase soil carbon inventories to as much as 30 to 40 Mg/ha over 20 to 50 yew when replacing cmpl~d.

This is roughly twice as much carbon as cropland carries and half that found in forestland. See: J.W. Ranney and L.K. Mann “Environmental

Issues,” in Lynn L. Wright and William G. Hohenstein, (eds.), “Biomass Energy Production in the United States: Opportunities and Constraints,”

U.S. Department of Energy and U.S. Environmental Protection Agency, DRAIW, August 1992.

82 “Carbon Storage and Accumulation in United States Forest Ecosystems,” U.S. Department of Agriculture, Forest Service, General

Technical Report WO-59, August 1992.

83 Jim L. Bowyer, “Tree Planting, Wood Use, and Carbon Sequestration,” Testimony before the Subcommittee on Energy and Power,

Committee on Energy and Commerce, U.S. House of Representatives, Washington, DC, July 29, 1993.

8A Kenneth R. Richards, Robrt J. Moulton, and Richard A. Birdsey, “COSLS of Creating Carbon Sinks in the U.S.,” IEA Carbon Dioxide

Disposal Symposium, Oxford, England, Mar, 29–31, 1993; D.H. Rosenthal, J.A. Edmonds, K.R. Richards, and M.A. Wise, “Stabilizing U.S.

Net Carbon Emissions by Planting Trees,” U.S. Department of Energy and Battelle Pacific Northwest Laboratories, Washington, DC, 1993.

85 Do. Hall, l-1.lZ. Myni&, and R.H. Williams, “Alternative Roles for Biomms in Coping With Greenhouse Warming,” Science and Global

Security, vol. 2, 1991, pp. 1 13–151.

M Cumendy, ~ome fo~~i] fuel—typically 5 t. 15 ~rcent of the energy value of the biomass crop---is used in the form of agricultural chemicals

or diesel fuel.

87 L L . .Wright and E.E. Hughes, “U.S. Carbon Offset Potential Using Bioma..s Energy systems,” Journal of Wuter, Air and Soil Pollution,

in press. See also footnote 81.
54 I Bioenergy

costs, however, and with further development

biomass energy may become a lower cost option

than fossil fuels. Biomass is also likely to be one

of the lowest cost of the renewable fuels for many

applications.

88 Land can be used to grow biomass

fuels on a continuous basis. This is in contrast to

sequestration strategies for which the annual carbon storage per unit land area declines as the forest

matures. Figure 3-3 illustrates the relative merits

of carbon sink (sequestration) versus fossil fuel

offset strategies. Offset strategies have greater

long-term potential to control atmospheric carbon

dioxide 89 because they can be continued indefinitely whereas, carbon sink strategies are limited

by maturation of the tree. Offset strategies also

have the potential to control carbon dioxide emissions cost effectively as they can substitute for the

fossil fuel; sink strategies will be a net economic

cost. 90

CROPPING PRACTICES

Numerous cropping systems have been developed

for conventional crops, including double and even

triple cropping (including intercropping and succession cropping); a variety of crop rotations; and

various forms of intercropping and agroforestry.

Hundreds of these systems are in use. These systems have been developed to reduce disease and

insect infestations, control weeds, improve water

utilization, improve soil quality and control erosion, and improve productivity. Multiple cropping

and other systems can also improve the utilization

of farm capital equipment and labor and reduce the

risks of failure of any one particular crop. The

practicability of these various cropping systems

depends on the soil, type of crop, local climate and

rainfall, and other factors. Similar development of

bioenergy cropping systems has not yet been done,

but may have considerable promise. Extensive

Figure 3-3—Schematic representation of

cumulative net emissions of CO2 as a function of

time for various combinations of a coal-fired

electric power plant and energy crop

management strategies

Path A shows the steady increase in cumulative C02 emissions into the

atmosphere from the coal-fired power plant. Path B shows the cumulative

emissions of C02 from the power plant less that taken up by growing

young trees sufficient to initially balance the power plant emissions. As

the trees mature they take up less and less C02 and eventually the

emissions parallel path A. Path C represents emissions from a power

plant which gradually shifts over to complete use of sustainably grown

biomass feedstocks. Planting a large area (strategy B) and then using

the biomass as a substitute for coal could fully offset emissions.

SOURCE: Adapted from: Greg Marland, “Strategies for Using Trees to

Minimize Net Emissions of C02 to the Atmosphere,” Testimony before

the Subcommittee on Energy and Power, Committee on Energy and

Commerce, U.S. House of Representatives, Washington, DC, July 29,

1993.

~~ Ro~~ H. Williams, “Fuel Cells, Their Fuels, and the U.S. Automobile,” First Annual World Car 2001” Conference, University of California

at Riverside, Riverside, CA, June 20-24, 1993.

w Greg Mti]md, ~’strategies for Using Trees to Minimize Net Emissions of C02 to the Atmosphere, “ testimony before the Subcommittee

on Energy and Power, Committee on Energy and Commerce, U.S. House of Representatives, Washington, DC, July 29, 1993.

~ D 0 Ha]l, H.E. Mynick, and R.H. Williams,

. . “Alternative Roles for Biomass in Coping With Greenhouse Warming,” Science& Global

Security, vol. 2, 1991, pp. 113-151.
Chapter 3–Potential Environmental Impacts 155

research and dedicated field trials are needed to

evaluate the relative costs and benefits of various

energy cropping systems. An extensive review of

conventional cropping systems, their impacts, and

their extension to bioenergy crops is given elsewhere.91 In turn, these multiple cropping systems

have a variety of impacts on local biological diversity. 92

CLOSE

Compared with conventional agricultural row

crops, energy crops may have positive environmental impacts, depending on the specific energy

crop, the previous use of the land, management

practices, and other factors. Under these circumstances, energy crops may improve soil quality

and reduce soil erosion, improve water quality—

particularly by reducing runoff and serving as

riparian filters, and may provide habitat benefits

themselves and as buffers around or corridors

between fragments of natural habitat. Compared

with hay, pasture, well-managed Conservation

Reserve Program, and other lands, however,

HECs and SRWCs will have mixed environmental

impacts. Finally, energy crops may provide an

effective offset to fossil fuel emissions of greenhouse gases.

Due to the little energy crop-specific data currently available and the corresponding heavy reliance on conventional agriculture analogs,

dedicated long-term studies of energy crops are

needed. These would focus on soil quality—including physical, chemical, biological, and other

parameters-and overall site productivity, water

quality, air quality, habitat, greenhouse gas emissions, and other issues and should be examined on

a full fuel cycle basis compared with alternative

fuels and technologies or other policies. With

these and other data, lands proposed for extensive

bioenergy cropping could be mapped by their topography, soil type, current usage, habitat value,

and other factors and classified by their potential

environmental impacts. Such Geographic Information Systems could be a valuable tool in realizing the potential of these energy crops at the local

and regional level.

Much research, development, and demonstration is needed to assure environmentally sensitive

and cost-effective energy crops; there are no shortterm answers. The development of a bioenergy

agenda to meet these goals poses substantial

challenges. This is the focus of the following

chapter.

91 Raymond N. Ga]l~er, “Bioenergy Cropping Systems, Sources, Management, and Environmental Considerations,” Contractor Report for

the Office of Technology Assessment, May 13, 1993.

92 David pimntel, et ~,, “ConseNing Biologic~ Diversity in Agricultural/Forestry SYstems>” Bioscience, vol. 42, No. 5, May 1992,

pp. 354-362.
F

or bioenergy to make a substantial contribution to the

U.S. energy mix, a number of technical, economic environmental, commercialization, and policy issues must

be addressed. Two of these will be examined briefly

here: research, development, and demonstration of environmentally sound energy crops; and market distortions and barriers

which threaten to substantial y slow commercial adoption of these

technologies.

RESEARCH, DEVELOPMENT, AND DEMONSTRATION

Research, development, and demonstration (RD&D) is needed at

all levels of biomass energy systems. This includes RD&D on:

high-productivity crop varieties; their planting, maintenance, and

harvesting; their environmental impacts; their transport and storage; and their conversion to fuels or electricity. The focus here

will be on their environmental impacts and how these relate to

other aspects of biomass energy systems.

Chapter 3 discussed the environmental impacts in some detail.

Many of the impacts noted there were based on studies of conventional agricultural crops and were extended by analogy to

energy crops; there have been few large-scale or long-term field

studies of energy crops themselves. These impacts need to be

carefully researched in dedicated field trials of energy crops:

Soil quality. Key areas of RD&D include: the development of

a “minimum data set” of key soil physical, chemical, biological,

and other parameters as a means of monitoring soil quality over

long periods of time for different crops and management regimens; nutrient cycling, particularly of biochemical processes;

the return of organic matter to the soil under various intensive

energy crops and cropping systems; and the impacts of necesThe

Bioenergy

Agenda 4

F or bioenergy

to contribute

substantially to the

energy mix, many

technical, economic,

environmental,

commercialization,

and policy issues

must be addressed.

57
58 I Bioenergy

sary equipment and various tillage systems on

soil quality. It may also be necessary to conduct

this RD&D in parallel with study of adjoining

land uses. This will improve understanding of

the interaction of energy crops with the larger

environment. Agreeing on what constitutes sustainability and means of realizing such systems

are important issues.

Agricultural chemicals. Research on the impact of agricultural chemicals on soil flora and

fauna and on wildlife is needed. This includes

research on the impacts on wildlife behavior

and reproductive processes. Chemical pathways and fate need to be better understood,

particularly when they affect more than the

target species or move out of the target area.

Understanding the dynamics of chemical use on

energy crops, how to reduce movement of

chemicals offsite, and how to reduce their use

generally are important issues.

Water quality. Research is needed on the impact of erosion/sedimentation and agricultural

chemicals from energy crops, especially on riparian zones, and on the potential of various

energy crops to serve as filters and buffers for

riparian areas. Studies are also needed on how

to best minimize potential leaching of agricultural chemicals into groundwater. Energy crops

might be a useful tool for reducing nonpoint

agricultural pollution, but data are needed to

verify this and to provide better crop guidelines

for realizing that end.

Air quality. Research on the total fuel cycle

emissions of various bioenergy crops, conversion, and end-use systems is needed in order to

minimize air quality impacts. This includes better understanding of both rural and urban air

quality issues and how to best trade them off to

maximize benefits. Comparing the potential air

quality impacts of bioenergy systems with those

of a wide range of other fuel and energy technology options is a key issue.

Habitat. Box 3-D listed a number of prototype

guidelines for structuring energy crops in order

to maximize their value as habitat, buffers, or

corridors. Each of these prototype guidelines

needs to be examined through extensive research in dedicated large-scale field trials and

modified as necessary. Such research must consider the impacts of energy crops in the context

of the regional landscape ecology and in the

near- and long-term. Establishing overall goals

for the desired habitat impacts—which species

should be helped-of energy crops in the larger

landscape will also require extensive analysis.

Restoration of degraded soils and ecological

functions. Energy crops may have the potential

to reverse soil deterioration from human abuse

in some cases. This might include improving

problems of soil structure, loss of top soil or

organic content, salinity, acidity or alkalinity, or

even chemical or heavy metal pollution.1 It

might also include restoration of some water

purification or wetland functions, including

moderating flood damage. Research is needed

to identify such opportunities, design systems

to make best use of this potential, and verify

performance in the field. Energy crop yields

may be low on some of these lands, however,

lowering the financial return to the land owner

and discouraging such efforts. Means of overcoming such barriers may need to be explored.

Greenhouse gases. The total fuel cycle (from

crop production to end use) impacts of energy

crops on greenhouse gases (including carbon

dioxide, methane, isoprenes, nitrous oxide, etc.)

needs to be evaluated for the various energy

crops, conversion processes, and end uses. The

development and use of a “minimum data set”

of key emission factors would be useful for

1 Growing plants will take up a variety of chemical or heavy metal toxins, depending on the precise substance and the particular plant species.

This poses a problem for food crops, as it concentrates the toxins and puts them into the food chain. In contrast, for energy crops these toxins

may be removed in the energy conversion process (for example, destroyed by combustion or concentrated in the ash) and so may allow a gradual

cleansing of the soil.
Chapter 4-The Bioenergy Agenda 159

determining these impacts. Related effects such

as on soil carbon balances or vehicle refilling

station VOC emissions should be included.

These fuel cycle emissions can then be compared for agricultural or energy crops and for

fossil or biomass fuels.

■ Crops and multiple cropping. The potential

risks and impacts of various genetically modified energy crops will need to reexamined. A

variety of multiple cropping systems should be

evaluated to determine how to ensure soil quality, habitat benefits, crop productivity, crop disease resistance, and other key economic and

environmental criteria. At the same time, research is needed to determine how to convert

agricultural lands to tree crops and vice versa;

the soils and microflora and fauna are often

much different.

It must be noted, however, that such research is

not being done in a vacuum. Extensive research

has already been done or is underway for many of

these and related topics in parallel systems and can

be made use of here.2

In addition to these factors, designing energy

crops to mitigate or provide these potential environmental costs or benefits may also impact other

aspects of developing energy crops, particularly

their economics. Each of these may need in-depth

study.

Energy crops must be cost effective for producers and users. This will require a careful balancing

of environmental considerations—including nearterm local and long-term global environmental

impacts—within the overall bioenergy economics. Detailed integrated analyses of the economics

and environmental impacts of various bioenergy

fuel cycles are needed. The potentially significant

environmental services energy crops may offer

may need some kind of recognition and valuation

by society and landowners. This may be quite

difficult.

As part of such an analysis, the habitat value of

polycultures may need to be weighed against the

difficulty of converting thereto fuels or electricity.

For example, some polycultures may not be easily

converted by current enzymatic hydrolysis processes to ethanol.3 In the near term, it may be more

important to verify the cost and performance of

these conversion processes using R&D already in

progress for narrowly specified (monoculture)

feedstocks. For the longer term, it maybe useful

to begin R&D now to adapt these enzymatic hydrolysis processes to mixed feedstocks as needed

in order to increase habitat benefits. Some research

on mixed feedstocks is underway at the National

Renewable Energy Laboratory. It tends to focus,

however—and rightly so at this early stage-on a

few common farm species that might be mixed

with the primary feedstock by accident rather than

a much wider range of plants that might be considered on the basis of their habitat value.4 Research into the conversion of feedstocks must be

tightly coupled with field research on the habitat

and other environmental benefits of particular

combinations of crops.

To avoid disrupting key lifecycle processes for

wildlife, biomass harvesting and other activities

may need to be restricted during nesting and other

critical times. This may require that sufficient

biomass be stored to keep the conversion plant

operating during this period; it may also require

idling capital equipment used for harvesting and

transport. Alternatively, electricity generation, for

example, might be powered during such periods

by the use of natural gas, and there maybe additional important synergisms between the use of

2 For example, the Electric Power Research Institute, the National Audubon Society, and others have initiated a National Biofuels

Roundtable. This Roundtable is developing a framework for evaluating many environmental, socioeconomic, and policy issues associated with

the development of bioenergy crops and conversion facilities.

? Under ~om conditions, @ycu]tuEs may ~so con~bute to slagging problems (the condensing of ~k~i met~s on su~aces such as biler

.

walls, heat exchangers, etc.) in combustion equipment. Jane Tumbull, Electric Power Research Institute, personal communication, Aug. 31,

1993.

4 Arthur Wiselogel, National Renewable Energy Laboratory, personal communication, Sept. 8, 1993.
60 I Bioenergy

biomass, natural gas, and renewable such as

wind, photovoltaics, and solar therrnal.5 On the

other hand, a well established biomass industry

may have a sufficient variety of crops and rotation

cycles to moderate this disruption. Field trials are

needed to determine the extent of these potential

disruptions and means of moderating them.

Farm labor needs are largely determined by the

intense effort required to plant and harvest conventional agricultural crops during a narrow window of time, usually spring and fall. Once planted,

however, perennial herbaceous or woody energy

crops may last 10 to 20 years, and harvesting may

take place over a wide period of time. Adding such

energy crops to the farmer’s portfolio might then

ease the burden during spring and fall, allowing

better use of labor and capital equipment overall.

Bioenergy crops will also naturally move to

their highest value use. This might be as a transport

fuel, as a baseload backup to intermittent renewable, for industrial chemicals or fiber, or perhaps for environmental benefits. It will be useful

to understand the full range of costs and benefits

for each potential use of bioenergy crops, including budget and trade balance impacts.

These crops might best serve a variety of end

uses simultaneously. In particular, the initial establishment of bioenergy crops might be assisted

by coupling energy production with higher value

uses of the feedstock. For example, an energy crop

might be initially established to serve a higher

value purpose such as the production of pulp and

paper and only secondarily for energy. The experience gained through such partnerships may provide a foundation for further energy crop

development and cost reductions.

Once a substantial market develops for lowquality wood fuels, there is the potential risk that

will encourage owners to harvest low-quality timber that is serving as important wildlife habitat or

to energy crop wetlands which are fertile but inappropriate for conventional agriculture. This is particularly important in regions such as the

Northeast where forests are the primary biomass

resource. Means of addressing such unintended

side effects may be needed.

Increasing land-use constraints—environmental and other-on Federal lands may encourage pulp and paper and other biomass product

users to move elsewhere. Competition for marginal and other lands may become more intense.

At the same time, there maybe increasing land-use

and environmental considerations for these agricultural or marginal lands. This may reduce the

area available for energy crops. As noted above,

however, combining multiple end uses such as

pulp and paper with energy may assist the initial

development and deployment of energy crops and

their associated infrastructure.

The structure of the farm sector also plays a role

in determining these environmental impacts and

needs to be examined carefully. For example,

roughly one-third of farms having fertilizer expenditures and one-quarter having pesticide expenditures in 1986 paid for some custom application

procedures. Training such specialists in the timing

and application of agricultural chemicals to minimize misapplication, potential groundwater leaching or runoff, or other problems may require one

set of extension activities; reaching the two-thirds

or more of farms which use on-farm hired laborers

or do it themselves may require a different appreach.G Extension efforts will also vary between

5 See U.S. CongEss, office of Technology Assessment, Renewable Energy Technology: Research, Development, and Commercial

Prospect;, forthcoming.

G New technologies may dSo help avoid SOTTE of these problems. For example, the development of time-release fertili=rs (or other

agricultural chemicals) would allow farmers to continue the common labor-saving practice of only spreading fertilizer (or other chemicals) once

per year while reducing the amount that must be applied to ensure that the nutrients are available late in the growth cycle. See David O. Hall,

Frank Rosillo-Calle, Robert H. Williams, and Jeremy Woods, “Biomaw for Energy: Supply Prospects,” Thomas B. Johansson, Henry Kelly,

Amulya K.N. Reddy, and Robert H. Williams, (eds,), Renewable Energy: Sources for Fuels and Electricity (Wa..hington, DC: Island Press,

1993).
Chapter 4-The Bioenergy Agenda 161

Table 4-l—Distribution of Farms by Sales Class and Percent of

Total Cash Receipts by Sales Class, 1987

Value of farm Number of Percent of Percent of total

Sales class products sold farms all farms cash receipts

Small, part-time <$20,000 1,380,000 63.4% 5.2%

Part-time $20,000 to $99,999 495,000 22.8 17.3

Moderate $100,000 to $249,999 201,000 9.2 22.0

Large $250,000 to $499,999 71,000 3.2 22.0

Very large >$500,000 29,000 1.3 37.4

Total — 2,176,000 100 100

SOURCE: U.S. Congress, Office of Technology Assessment, Beneath The Bottom Line: Agrcultural Approaches to

Reduce Agrichemical Contamination ofGroundwater,OTA-F-418 (Washington, DC: U.S. Government Printing Office,

November 1990).

the very large farms and the small, part-time farms

(table 4-l). Tenants and part-owners are operating

an increasing proportion of farms and farmland

acres and may have less concern about environmental costs and benefits of various crops and

management systems than owners.7

Finally, to realize the benefits of energy crops

as habitat, buffers, and corridors may in some

cases require a level of regional landscape planning not often seen in this country. This will

require much more RD&D on regional landscape

ecology and its sensitivity to imperfections. It will

also require considerable effort in developing new

policy instruments to encourage participation in

forming such a landscape across many public and

private properties. These issues are examined further below.

MARKETS AND BARRIERS

Agricultural production of energy crops faces a

variety of market distortions and barriers that may

slow their adoption. These will be discussed here

within two broad categories: products and markets; and land use and rights issues. Many of the

issues of commercializing alternative transport fuels themselves have been recently addressed in a

separate OTA assessment,8 particularly the difficulties inherent in developing a new fuel distribution infrastructure. The focus here instead will be

on the difficulties in producing the crops.

Products and Markets9

The first difficulty faced by producers and converters of bioenergy crops is the chicken and egg

problem of developing a market. To justify producing an energy crop, farmers must have a reasonably secure market for their product at a

potentially economic price. On the other hand,

electricity generators or liquid fuels producers

need a reasonably assured and economic supply of

biomass before they can justify building a conversion plant. For both parties, the economics of

energy crops are improving but remain expensive.

Lead times to develop crops and conversion

plants are also long. Typical SRWCs require 3 to

10 years to mature. Farmers are often reluctant to

make the investment due to this long lead time and

the need for interim cash flow, particularly with

current low and uncertain prices for other forms of

energy.

7 U.S. Congress, Office of Technology Assessment, Beneuth The Bottom Line: Agricultural Approaches to Reduce Agrichemical

Contamination ofGroundwater,OTA-F-418 (Washington, DC: U.S. Government Printing Office, November 1990).

8 U.S. Congress, Office of Technology Assessment, Replacing Gasoline: Alternative Fuels for Light-Duty Vehicles, OTA-E-364 (Washington, DC: U.S. Government Printing Office, September 1990).

9 The primary source for much of this section, which contains far more detail than presented here is: U.S. Congress, Office of Technology

Assessment, Beneath The Bottom Line: Agricultural Approaches to Reduce Agrichemical Contamination of Groundwater, OTA-F-418

(Washington, DC: U.S. Government Printing Office, November 1990),
62 I Bioenergy

Energy crops may also reduce the flexibility of

farmers. It maybe difficult to quickly plow under

a tree crop and plant the land with something else

should crop productivity, market conditions, or

other factors limit the return on the farmer’s investment of labor, land, and capital. Thus, while

the Conservation Reserve Program encouraged

U.S. farmers to convert 12 million hectares

10

of

marginal cropland to permanent cover during

1986 to 1989, only 1 million hectares of this was

planted with trees.11

Farmers typically make production decisions

within short timeframes and with maximum flexibility, which discourages investments in potentially longer term and less flexible energy crops.

Economic factors are typically the most pressing

in farmer decisionmaking; market prices, support

levels, credit availability, and debt load are critical

considerations at the individual farm level. Farmers often are forced to make decisions within a

short-term, year-to-year planning horizon that can

prevent them from taking risks or making the most

economically efficient decisions over a longer

term. Farmers asked to respond voluntarily to

public concerns about environmental impacts tend

to evaluate proposed technologies, crops, management, or other aspects for their relative advantage

within the existing set of economic conditions.

Many farmers also make changes slowly. Farm

management changes, even relatively minor ones,

are not decisions made overnight. Farmer adoption of relatively simple, highly profitable technologies such as hybrid com has taken as long as

nine years on average. The decision to change

farming practices requires a considerable degree

of deliberation, and maintaining new practices

frequently necessitates on-farm experimentation

and adaptation beyond that conducted during initial technology development.

Farmers tend to underestimate the severity of

environmental problems on their own farms.

Farmers tend to perceive, for example, that soil

erosion and water quality problems are more severe at the national level than they are in their own

counties. They also tend to perceive these problems as least severe on their own farms. This

“proximity effect” indicates that farmers are

aware of the need to protect soil and water in

general but often underestimate the need on their

own farms. As a potential moderator of such environmental impacts under the right conditions, energy crops are therefore likely to be valued less

than if the severity of these problems was fully

appreciated.

Farmers are most likely to adopt technologies

with certain characteristics. Favored technologies

are those that: 1) have relative advantage over

other technologies (e.g., lower costs or labor,

higher yields, etc.); 2) are compatible with current

management objectives and practices; 3) are easy

to implement; 4) are capable of being observed or

demonstrated; and 5) are capable of being adopted

on an incremental or partial basis. Diffusion research indicates that farmers are probably more

likely to test technologies or practices that they

think have these characteristics. The complexity

of systems-oriented changes will likely slow their

adoption. This poses particular problems for regional landscape planning in order to maximize

habitat benefits of energy crops. Mechanisms for

incrementally realizing habitat benefits may be

needed should these programs go forward.

Individual and farm characteristics appear to

explain only a small portion of behavior associated

with adopting new crops or farming practices;

institutional factors (e.g., farm programs, credit

availability, etc.) probably are highly influential.

Research on individual farm characteristics (e.g.,

10 The total now stands at approximately 15 million hectares. Thyrele Robertson, U.S. Department of Agriculture, soil conse~ationSenice,

personal communication, Aug. 26, 1993.

I I R. Neil Sampson, “Biomass Oppflunities in the United States to Mitigate the Effects of Global warming,” Donald L. Klass> (cd.), EneWY

from Bimna.w and Wastes XV (Chicago, IL: institute of Gas Technology, 1991).
Chapter 4-The Bioenergy Agenda 163

size, specialization, land tenure) and farmer traits

(e.g., age, education) and their relation to conservation adoption has yielded mixed results. Most

researchers consider institutional factors to be

much more influential, but few studies have been

conducted on these to date. Studies on adoption of

farm practices have also rarely examined the

physical settings of adoption decisions or the extent of resource degradation as it relates to adoption of alternative farm practices.

Finally, farmers are a heterogeneous group with

unequal abilities, unequal access to information

and resources for decisionmaking, differences in

willingness to take risks, and a wide range of

objectives in even practicing farming. For example, farmers’ objectives may include: making a

satisfactory living (either as an owner-operator,

tenant, or employee); keeping a farm in operation

for family inheritance or other personal reasons,

perhaps while working at an off-farm job; obtaining a satisfactory return on investments in land,

labor, and equipment; obtaining tax benefits; obtaining recreation or esthetic enjoyment; and others. These objectives will influence the portfolio

of crops, including energy crops, that a particular

farmer will choose to grow.

Land Use and Rights

The potential habitat benefits of energy crops—

as habitat, buffers, or corridors-will increase as

they are integrated on a regional basis with the

local ecology. Pursuing this to its maximum limit

may require a degree of landscape planning that

has rarely been seen in this country. This raises

major issues in terms of land use and property

rights, issues that are also at the center of controversies over the “Multiple Use, Sustainable Yield”

philosophies of public lands management. These

issues have been explored in depth in numerous

publications and so will be only briefly mentioned

here. 12

Public and private properties already face a

variety of environmental and other considerations

in their use. These include zoning and land use

planning, clean water and air laws, forest practice

and pesticide control laws, endangered species

laws, and a variety of other considerations.

Whether and, if so, how such resource considerations might be extended to the production of energy crops will be a difficult but critical aspect of

developing a bioenergy agenda.

Some of these controls maybe counterproductive if they are extended to bioenergy in an inflexible manner. For example, some argue that

improving habitat on private lands may pose risks

to property owners that if endangered or threatened wildlife establishes itself, the property owner

will largely lose control of that land as well as on

adjacent lands where activities might disrupt the

wildlife. 13 As a consequence, anecdotal evidence

.

indicates that some farmers may cut or bum potential habitat to prevent wildlife from using it;

alternatively, the wildlife might simply be driven

off or killed. Whether or not this is a significant

problem or how widespread the problem might be

is unknown. Using energy crops as habitat, buffers, or corridors will require understanding and

carefully addressing these issues.

These issues thus address fundamental assumptions and values of, for example: what actually is

private property (e.g., what is really owned?); to

what extent can a person use or abuse private

property and at what point do larger community

interests become important; how does one value

different environmental goods and services—including clean air and water, quality soils, wildlife,

and aesthetics—and how can that be translated

into functioning markets; and how does one determine and apply discount rates, if at all, to natural

12 SW, for example: Congmssiond Resemch Service, Mu[tiple Use and Sustained Yie[d: Changing Phikmphies fc)r F’ederal tind

Management? Workshop Proceedings and Summary, Mar. 5-6, 1992, Committee on Interior and Insular Affairs, U.S. House of Representatives,

Committee Print No. 11, December 1992.

Is John Miller, “hd of the Free: An Environmental Strategy for Republicans,” Policy Review, Winter 1993, pp. 66-70.
64 I Bioenergy

resources? These issues pose substantial chal- economic development, and improving the envilenges to public policy. ronment. Realizing this potential will require a

long, dedicated effort in terms of research, develCLOSE opment, demonstration, and commercialization of

Energy crops can potentially help meet a number these technologies. Haphazardly implementing

of national goals, including: national energy and large-scale bioenergy programs without such a

security needs, improving the trade balance, re- foundation could damage the environment and

ducing Federal budget deficits, stimulating rural reduce potential economic benefits.
Appendix A:

Related

OTA Studies

OTA has previously published a number of studies addressing issues related to energy crops and their

environmental impacts. Previous studies include the following:

U.S. Congress, Office of Technology Assessment,

Impacts of Technology on U.S. Cropland and

Rangeland Productivity OTA-F-166 (Washington,

DC: U.S. Government Printing Office, August,

1982)

U.S. Congress, Office of Technology Assessment,

Beneath the Bottom Line: Agricultural Approaches

to Reduce Agrichemical Contamination of Groundwater, OTA-F-418 (Washington, DC: U.S. Government Printing Office, November 1990).

U.S. Congress, Office of Technology Assessment,

Energy from Biological Processes, OTA-E-124

(Washington, DC: U.S. Government Printing Office, July 1980), Volume II, Volume III-Appendixes

OTA-E-128 (September 1980).

U.S. Congress, Office of Technology Assessment,

Water-Related Technologies for Sustainable Agriculture in U.S. Arid/Semiarid Lands, OTA-F-212

(Washington, DC: U.S. Government Printing Office, October 1983).

U.S. Congress, Office of Technology Assessment,

Forest Service Planning: Setting Strategic Direction Under RPA, OTA-F-441 (Washington, DC:

U.S. Government Printing Office, July 1990).

U.S. Congress, Office of Technology Assessment,

Forest Service Planning: Accommodating Uses,

Producing Outputs, and Sustaining Ecosystems,

OTA-F-505 (Washington, DC: U.S. Government

Printing Office, February 1992).

U.S. Congress, Office of Technology Assessment,

Technologies to Maintain Biological Diversity,

OTA-F-330 (Washington, DC: U.S. Government

Printing 0ffice, March 1987).

U.S. Congress, Office of Technology Assessment,

Technologies to Benefit Agriculture and Wildlife,

Workshop Proceedings, OTA-BP-F-34 (Washington, DC: U.S. Government Printing Office, May

1985).

U.S. Congress, Office of Technology Assessment,

Changing by Degrees: Steps to Reduce Greenhouse

Gases, OTA-O482 (Washington, DC: U.S. Government Printing Office, February 1991).

65
Appendix B:

Units and

Conversion

Factors

Conversion Factors

Area

1 square kilometer (km2)= 1 acre=

0.386 square mile 0.405 hectare (ha)

247 acres 1.56x10-3 square miles

100 hectares 4.05x10 -3 square kilometers (km2

)

1 square mile= 1 hectare=

2.59 square kilometers (km2) 0.01 square kilometer (km2

)

6.4xl02 acres 3.86x10 -3 square miles

2.59x10 2 hectares 2.47 acres

Weight

1 kilogram (kg)= I metric tonne (mt or “long ton”)=

2.20 pounds (lb) 1,000 kilograms or 2,200 lbs

1 pound (lb)= 1 short ton=

0.454 kilogram (kg) 2,000 pounds or 907 kg

1 quad (quadrillion Btu)=

1.05x10 18 Joules (J)

1.05 exajoules (EJ)

4.20x107 metric tonnes, coal

1.72x108 barrels, oil

2.34x107 metric tonnes, oil

2.56x101° cubic meters, gas

5.8x107 metric tonnes dry wood

2.92x10 11 kilowatthours

Energy

1 kilowatthour=

3.41x10 3 British thermal units (Btu)

3.6x106 Joules (J)

1 Joule=

9.48x10- 4 British thermal unit (Btu)

2.78x10-7 kilowatthours (kWh)

1 British thermal unit (Btu)=

2.93x104 kilowatthours (kWh)

1.05x103 Joules (J)

66
Appendix B–Units and Conversion Factors I 67

1 liter (1)=

2.64x10-1 gallons (liquid, U. S.)

6.29x103 barrels (petroleum, U. S.)

1X10-3 cubic meters (ins)

3.53x10- 2 cubic feet (fi3

)

1 gallon (liquid, U.S.)=

3.78 liters (1)

2.38x10-2 barrels (petroleum, U. S.)

3.78x103 cubic meter (m3)

1.33x10-1 cubic feet (ft3)

1 barrel (bbl) {petroleum, U.S.)=

1.59x102 liters (1)

42 gallons (liquid, U.S.)

1.59x10 -1 cubic meters (m3

)

5.61 cubic feet (ft3

)

From Centigrade to Fahrenheit:

((9/5) X (“C))+ 32 =OF

Volume

1 cubic meter (3)=

1X103 liters (1)

2.64x102 gallons (liquid, U. S.)

6.29 barrels (petroleum, U. S.)

35.3 cubic feet (ft3)

1 cubic foot (ft3)=

2.83x101 liters (1)

7.48 gallons (liquid, U. S.)

1.78x10-1 barrels (petroleum, U. S.)

2.83x10-2 cubic meters (m3)

1 cord wood=

128 cubic feet (ft3) stacked wood

3.62 cubic meters (m3

) stacked wood

Temperature

From Fahrenheit to Centigrade:

(5/9) X (

O

F - 32) -‘C

Temperature changes:

—To convert a Centigrade change to a Fahrenheit change:

9/5 x (change in ‘C) = change in ‘F

—To convert a Fahrenheit change to a Centigrade change:

5/9 x (change in oF) = change in ‘C

—Example: a 3.0‘C rise in temperature = a 5.4‘F rise in temperature
Index

Agricultural chemicals, 4,28-30,58

Energy crops, 29-30

Toxicity, 29-30

Use, 29-30

Water pollution, 34-37

Wildlife, 30

Agriculture

Environment, 16

Farm Sector, 59-63

Habitat impacts, 40-41

Markets, 3, 15

Agroforestry, 54

Air quality, 2, 12-13,37-39,58

Annual row energy crops, 1

Baseload power, 3,9-10,59-60

Bioengineering, 19

Biogenic emissions, 38-39

Biological diversity, 41,4445

Biomass energy

Carbon sink, 51-54

Crop varieties, 18-20,24-25,46,54

Economics, 20,33,49,53-54,55,58-63

Energy balance, 39

Fossil fuel offset, 51-54

History, 7

Installed, 9

Land available, 19-20

Resources, 17-20

See Air Quality

See Habitat

See Soil Quality

See Water Quality

Water needs, 37

Value, 60

Birds, 40-49

Brown-headed cowbird, 42

Cavity nesters, 42

Northern Flicker, 43

Red-breasted nuthatch, 43

Brazil, 3, 15

Buffers, 2,46,48

Carbon, 2,24,49-54

See Biomass Energy

See Global Warming

See Soils

Sequestration, 52-54

Cavity nesters, 42

Cellulose, 2, 12

China, 3, 15

Clays, 25

Clean Air Act, 9

Clean Air Laws, 38

Climax forest, 46

See Old Growth

Coal, 3,8

Commercialization, 4,59-63

Commodity Support Programs, 3, 15-17

Conservation Compliance Programs, 16

Conservation Reserve Program, 2,3,16-17,23,33-34,

37,55,62

Conversion technologies, 11-13

Electricity, 11

Ethanol, 12

Gas Turbines, 11
70 Potential Environmental Impacts of Bioenergy Crop Production

Methanol, 12-13

Steam Turbines, 11

Corn, 1,2, 3

Corridors, 2,44,4849

Crop Rotations, 29-30,54,59

Degraded lands, 5,58

Demonstrations, 4, 18-19,23-24,34,47,57-59

Dust, 37-39

Eastern Europe, 3, 15

Electric Utilities, 3,9-10,53-54,59-60

Electricity Sector, 9

Energy conversion, 4

Problems, 59

Processes, 11-13

Energy crops

See Biomass Energy

Energy demand, 5,8-10, 13-15

Energy Policy Act, 9

Erosion, 24,31-34,35-36,57-58

Ethanol,

See Conversion Technologies

Eutrophication, 35

Farm Sector, 4,60-63

Farmers Home Administration, 16

Federal Budget, 3, 16-17

Fencerows, 40

Fertilizer

See Agricultural Chemicals

Field Burning, 38

Field margins, 40

Filters

Coarse and fine (for species), 41

Riparian, 2,32,35-37

Food Security Act, 16

Forest interior species, 40,42

Fuel cycle, 4,38-39,53-54,58-59

Fungi, 28,43,49

Gas Turbines

See Conversion Technologies

Geographic information systems, 55

Global Warming, 2-3,44-45,49-54,58-59

Greeks, 7

Greenhouse gases, 2, 13,44-45,49-54,58-59

Ground cover, 48-49

Habitat, 2,23-24,39-49,58,63

Agriculture, 40-41

Aquatic, 35,43

Buffers, 44,48,63

Corridors, 44,48,63

Energy crops, 44-49

Field operations, 49,59

Forestry, 41-42

Fragmentation, 46-47

Guidelines, 47

Protecting, 60

RD&D, 58

Restoration, 58

Riparian, 42-44

See Natural Habitat

Succession, 40,42

Wetlands, 42-43

Harvesting, 49,59

HECs (Herbaceous Energy Crops), 1

Harvesting, 1

Lifetime, 2

Potential, 18-20

Selection, 2, 19

Soils, 24-34

Technical feasibility, 18-19

Hedgerows, 40

Herbicides

See Agricultural Chemicals

Insecticides

See Agricultural Chemicals

Insects, 28-30,4049

Institutions, 4

Intercropping, 4,44-49,54,59

InterGovernmental Panel on Climate Change, 50-52

Isoprene emissions, 38

Landfill, 17

Landscape design, 4,3949,55,63

Land

Availability, 19-20

Use, 4,63

Lignocellulosic energy crops, 2, 12, 17-20

Mammals, 40-49

Market barriers, 61-62

Mechanization

Habitat impacts, 40,59
Index 71

Methanol

See Conversion Technologies

Minimum Data Set

See Soil Quality

Mixed feedstocks, 4,59

Monoterpenes, 38

Multiple cropping, 4,29-30,54,59

Municipal solid waste, 17-18

National Biofuels Roundtable, 21,59

National Renewable Energy Laboratory, 12,59

National security, 7, 14-15

Natural gas, 8,59-60

Natural Habitat, 5

Defined, 2,23,47

See Habitat

Non-indigeneous species, 2,4648

No-till agriculture

See Soil Quality

See Water Quality

NOX, 2,38-39

Nutrient Cycling, 30-31

Losses, 34-37

Oil, 8

Imports, 3,7,9-10, 14-15

Old-growth forests, 42,46

Organophosphates, 30

See Agricultural Chemicals

Pollution

See Air Quality

See Soil Erosion

See Water Quality

Polycultures, 59

See Habitat

Population growth, 3

Predators, 30,40,42

Property rights, 4,63

Pulp and paper, 8, 10, 13-14,60

Renewable, 3,9-10,59-60

Research and development, 4,11-13,18-19,34,47,54,

57-59

Residential sector, 14

Residues, 18,30-31,32-34,40,43, 47,49

Restoration of degraded lands, 58

Riparian, 34-37,40,42,44

Remans, 7

Roots, 4,24,36

Rural economy, 3, 15-17,60-63

Salamanders, 44

Site preparation, 31

Snags

See Trees (dead)

soils, 2,24-34,57-58

Acidity/alkalinity, 28-29,34,42

Biological aspects, 26,28-29

Chemical aspects, 27-28,34

Clays, 25

Compaction, 26-27,34

Density, 26

Erosion, 31-33, 34-37

Minerals, 25-28

Minimum data set, 34,57

Nutrients, 28

Organic matter, 25-26,

Physical aspects, 26-27

Rooting depths, 27,36

Temperatures, 27

Soviet Union, 3, 15

Sox, 2,39

Soybeans, 2,3

SRWCs (Short Rotation Woody Crops), 1

Harvesting, 1

Lifetime, 2

Potential, 18-20

Selection, 2, 19

Soils, 24-34

Spacing, 1

Technical feasibility, 18-19

Steam Turbines,

See Conversion Technologies

Succession, 40,42,46

Tennessee Valley Authority, 12

Trade balance, 3, 14

Transport sector, 8-9

Trees

Dead, 43

See SRWCs

Water Quality, 24,34-37,58

Wetlands, 34-37,40,42,44

* US GOVERNMENT PRINTING OFFICE 1993 - 343-283 - 814/96964