Perennial plants, like trees and shrubs,

have the potential to provide large quantities of biofuel feedstock. Given a relatively fixed land base, any agroforestry

practice can be designed to produce a

harvestable product, and at the same time

provide a conservation service which

helps to bridge the competition between

agriculture and forestry land uses for

energy crop production. 

To create integrated biomass production systems, it is essential that agriculture

and forestry work together. This issue of

Inside Agroforestry provides an overview

of the energy potential of woody biomass. k

VOLUME 15 ISSUE THREE

3

JUST HOW MUCH O

ENERGY ARE WE TALKING ABOUT?

ur growing population is faced

with an ever-increasing problem.

Today, working lands must meet more

than simply the demand for food. In

addition to providing an array of ecological services like clean water, soil conservation, and wildlife habitat, working lands

– both forestry and agriculture – are

being challenged to develop sustainable

approaches to produce renewable biomass crops to help meet our nation’s

energy needs. 

8 WOULD YOU LIKE TO

GROW YOUR OWN FUEL?

4 CLIP ‘N’ SAVE! 

Woody biomass is a viable

component of the total

bioenergy system in the US.
Set up an 8’ X 10’ Working Trees

display at your next workshop, 

conference, or even at the post office.

Using one of NAC’s six displays, and

the accompanying brochures, is a sure

way to start conversations about the 

benefits of agroforestry. NAC ships displays free of charge; the only cost you

incur is return shipping to NAC or to

the next user. Visit NAC’s website for

additional photos, information about

how to reserve a display for your event,

and to order free supplemental

Working Trees brochures:

www.unl.edu/nac. k

Back to the future

NAC Director’s Corner

A commentary on the status of agroforestry 

by Dr. Greg Ruark, NAC Program Manager

2 Inside Agroforestry |Volume 15, Issue Three

I n the search for a more sustainable approach tosupplying our nation’s future energy needs we

have come full circle and are again looking at wood as

an essential part of the solution. Rapidly growing tree

and shrub types can be grown in ways that maximize

the production of woody biomass which can then be

harvested and converted to biofuels. Wood, with its

high cellulose and hemi-cellulose content, has a high

weight to energy conversion ratio that greatly exceeds

that of ethanol produced from corn grain. Existing

biochemical and/or thermochemical processes can be

used to convert wood into bio-oil, ethanol, and

syngas products.

The US Department of Energy has recently

increased research funding on cellulose conversion

technology to improve conversion efficiency, reduce

costs, and scale up production levels. Forestry research

over the past few decades has led to substantial

increases in biomass yield for tree species like aspen,

cottonwood, sweetgum, and willow. However, a 

corresponding effort is still needed to develop woody

biomass production systems that are sustainable and

that also factor in ways to protect soil fertility and 

provide wildlife habitat at the landscape level. These

production systems also need to minimize unintended

negative off-site impacts that are often associated with

intensive agriculture, like soil erosion and nutrient

runoff. The opportunity to grow trees and shrubs as an

energy crop will occur both on lands that are currently

forested and on those that are now used for 

agriculture. As such, it will be important to integrate

the production of woody biomass crops with our

nation’s Farm Bill programs. k

Need help marketing 

Working Trees ?

Working Trees displays for six topic areas are available: agriculture, communities 

(pictured), water quality, wildlife, livestock, and treating waste. NAC file photo
Volume 15, Issue Three | Inside Agroforestry 3

Biomass currently provides about 10

percent of the global energy

supply. Developing sustainable

approaches to producing renewable biomass crops that help meet our nation’s

energy needs is an emerging critical challenge. Perennial plants have the potential

to provide large quantities of biofuel

feedstock, while also providing an array

of ecological services and revitalizing

declining rural economics. 

With a relatively fixed land base, the

production of energy crops will compete

with traditional agricultural and forestry

uses of land. Agriculture and forestry

must work together to create integrated

biomass production systems. 

Agriculture today

Agriculture in the United States is highly

mechanized and uses considerable fertilizer and pesticide inputs. The agricultural

sector is increasingly vertically integrated

and in any given year only a few varieties

of corn or soybeans are planted. The

downside of our industrial agricultural

approach has been the loss of most ecological services across the landscape. The

massive spatial scale for cropping and the

uniform vegetation provides little oppor- see Potential on page 11

tunity for species diversity and only minimal structural diversity across the landscape. Conservation challenges include

managing soil erosion, concentrated livestock waste, runoff of fertilizers and pesticides into surface water and groundwater with substantial downstream

impacts. 

Conservation benefits of trees on

agricultural land

Agroforestry practices that incorporate

trees into working agricultural lands have

been used in the US since the time when

windbreaks were employed to abate soil

erosion in the “dust bowl” of the 1930’s.

In the past 15 years, the interest in and

adoption of agroforestry practices have

Short rotation woody crops, like hybrid poplar and willow, can grow 15 to 25 feet in only three years. NAC file photo

Woodys have biomass potential

Perennial woody crops have the potential to contribute

significantly to the production of bio-fuels while at the

same time provide a wide range of conservation benefits.
4 Inside Agroforestry |Volume 15, Issue Three

Whatever the type of farm,there are ways to reduce costs

by integrating energy efficient

improvements into the operation.

Renewable energy adjustments will

not only save producers money, but

will cut input costs, maintain 

production, protect soil and water

resources, and reduce the negative

effects of burning fossil fuels. 

There are several ways to incorporate energy-saving strategies:

• Utilize existing on-farm energy 

by taking advantage of homebased fuels

• Produce and sell energy 

generated on the farm, and 

• Conserve energy

The Natural Resources

Conservation Service (NRCS) has

developed four tools to help a producer identify where energy costs can

be cut. The tools enable the user to

calculate potential cost savings for

animal housing, irrigation, nitrogen,

and tillage. Visit www.nrcs.usda.gov/

technical/energy/index.html to access

this service. k
Volume 15, Issue Three | Inside Agroforestry 5
6 Inside Agroforestry |Volume 15, Issue Three

A

gricultural and forest crops and residues as well as industrial and municipal residues

can be used to provide heat, generate electricity, and make fuels, chemicals, and other 

products. These "biomass" materials are feedstocks that can be converted to energy 

products through various chemical and physical processes and can help address US energy needs.

In general, there are two

approaches to generating energy

from organic material:

1 Grow plants specifically for 

energy use.

2 Use the residue from plants that

are harvested and processed 

for other purposes. 

The production of sustainable energy from farm and

forestry activities may not change what is grown as

much as how crops are marketed and processed. Each

biomass material has different characteristics that

require different processing methods to convert it to

energy. For example, biomass low in ash content and

high in lignin is best utilized in co-firing, whereas high

sugar composition feedstocks are more efficiently 

converted to ethanol.
Volume 15, Issue Three | Inside Agroforestry 7

What’s ahead?

In the United States, biomass already provides about 1.2 percent of our nation’s total electric sales. We also get about two

percent of the liquid fuel used in cars and trucks from biomass.

• Present and near future: Easily processed agricultural 

crops and low-cost industrial residues will likely dominate 

biomass feedstocks. 

• Mid-term: Agricultural and forestry residues should enable 

the biomass industry to expand to make more substantial 

contributions. 

• Future: Ongoing research is discovering new ways to 

replace petroleum-based energy, chemicals, and products 

with bio-based equivalents.

Availability

The ability to cost-effectively

convert woody biomass into

energy presents many challenges. Availability, collection (harvest), and storage

are all issues that will need to

be addressed. Transportation economics may be the

overriding factor since raw

biomass typically can’t be

cost-effectively shipped

more than about 50 miles

for energy conversion.

k
8 Inside Agroforestry |Volume 15, Issue Three

Biomass is an attractive alternative to fossil fuelenergy sources because it is carbon neutral and

renewable. Presently, biomass supplies about 2.9

quadrillion BTUs or 3 percent of

the total energy consumption of

the United States. Over half of this

supply is derived from woody

material through combustion of

spent pulping liquors and mill

residues. While direct combustion

is the most thermodynamically

efficient way to recover energy

from any material, it is limited

because the energy can’t be stored and must therefore either be used on site or converted into another

form such as steam or electricity. Alternative

approaches that may provide more flexible sources of

fuels from woody biomass include biochemical and

thermochemical processes. 

Biochemical

The most familiar biochemically-produced alternative

fuel is ethanol. Ethanol is primarily derived from a

process that involves the fermentation of sugars by

yeast. Today, domestic ethanol is prepared mainly

from the starch in corn kernels, while sugar cane is

used in Brazil. Corn leaves and stalks, referred to as

corn stover, is also a possibility with their processing

to follow the same conversion pathways as other lignocellulosics, like woody biomass, described below. 

Woody biomass is primarily composed of cellulose and hemicellulose. It contains some sugars, in

the form of long-chain polysaccharides that must first

be broken down into simple sugars prior to fermentation. This limitation accounts for the relative efficiency difference of about 60 gallons per ton and 90

gallons per ton for wood and corn, respectively. This

discrepancy notwithstanding, when other monetary

inputs of growing corn (fertilizer, herbicides, pesticides) are taken into account, the economic competitiveness of wood ethanol grows

more attractive. The processes

necessary to convert lignocelluosics, such as wood and switchgrass, are still being developed and

have not yet been scaled up to

produce commercial quantities.

Thermochemical

The primary thermochemical

methods for processing wood are pyrolysis and gasification. Both use high temperatures with limited

amounts of air to produce varying proportions of

solid, liquid, and gaseous products. 

• Pyrolysis – takes place at about 500°C (932 F). 

The principal product is a liquid, called pyrolysis 

oil or bio-oil. This oil is a complex mixture of 

chemical components that is corrosive and generally needs to be processed further. The process is 

similar to how petroleum oils are refined. The oil 

has also been evaluated as a source of chemicals 

that can be used to produce adhesives. 

• Gasification – requires high temperatures, 800-

900°C (1500-1600 F), and the main product is a

low BTU gas, referred to as syngas. Syngas is a 

mixture of carbon monoxide, carbon dioxide,

Thomas Elder

Research Forest Products Technologist

USDA FS Southern Research Station 

Pineville, LA

see Potential on page 10

New technology makes 

it possible to create 

efficient fuels from 

wood that can be 

transported easily. 
Improve air quality. Woody biomass

recycles carbon out of the air and

releases it again and is carbon neutral,

unlike fossil fuels.

Reduce water pollution. Fewer 

fertilizers and pesticides are used to

grow woody energy crops. Less

nutrient-laden runoff from fields keeps

our streams cleaner.

Improve soil quality. High-yield food

crops tend to pull nutrients from the

soil, whereas perennial crops actually

improve soil quality. Trees and grasses

with deep roots build up topsoil, and

put nitrogen and other nutrients into the

ground.

Reduce soil erosion. Perennial biomass

plants (i.e. trees and grasses) are replanted

only every 10 years resulting in less soil

disturbance.

Improve wildlife habitat. Woody crops

create better wildlife habitat than food

crops. Since many species are native

plants, they attract a greater variety of

birds and small mammals. They improve

habitat for fish by increasing water quality

in nearby streams and ponds. Flexible

harvest schedules make it easier to avoid

disturbing wildlife during critical nesting

seasons. k

Volume 15, Issue Three | Inside Agroforestry 9

Environmental benefits

of biomass energy

Woody biomass is a more 

sustainable energy source than

that derived from fossil fuels or

annual crops. 

Fossil fuel is a limited resource

whereas woody biomass can be

grown again. 

Annual crops require higher inputs

than perennial woody biomass.

Timberbelts

Timberbelts are multiple-row fieldwindbreaks that are planted with

commercially valuable, fast-growing trees

like hybrid poplar or hybrid willow.

Timberbelts provide the conservation

benefits of a properly designed windbreak but also produce commercially

valuable wood products. 

The strategy is to harvest half of the

timberbelt rows at age 7-12, leaving the

other half to provide continued wind

protection. Within a few years the stumps

will have sprouted and re-established to

provide sufficient wind protection at

which time the remaining rows can be

harvested. This provides continuous

wind protection and allows a landowner

to reap the associated economic benefits

for the adjacent crops. 

Hybrid poplar yielded 5 dry

tons/acre/year, a reasonable national

average, in north central United States

and has reached 7 dry tons/acre/year on

high-productivity sites. There are approximately 38 million acres of Conservation

Reserve Program (CRP) lands; if these

acres were planted to hybrid poplar,

annual production could reach 16 million

BTU’s per dry ton/year, that is equivalent

to 3,040 trillion BTUs (3 quads)/year. 

Short rotation woody crops can contribute significantly to the Nation’s

energy fuels. An added benefit would be

the reinvigoration of rural economies,

while producing substantial levels of ecological services. k

Money may not grow on trees, butheat, electricity, liquid fuel, and

even plastics do. Children can learn how,

with the release of The Hidden Treasure,

an educational comic book from the

National Association of Conservation

Districts (NACD). This new teaching tool

shows young people and families how

woody biomass from our nation’s woodlands can provide a wealth of products

and energy resources. The book can be

previewed at www.discoverycomics.com/

review/TheHiddenTreasure.pdf (6.3 MB).

Order copies in quantities of 100 

(min: 500; max: 2,000) by contacting

Nancy Hammond: nhammond@fs.fed.us,

fax 402–437–5712, http://www.unl.edu/

nac/order.htm. k

NACD digs up “The Hidden Treasure”
10 Inside Agroforestry |Volume 15, Issue Three

Conversion

continued from page 8

Short rotation woody crops can be harvested and chipped on site then burned for heating.

The cut stumps will resprout for another crop. NAC file photos

There are several good resources available for more information on 

converting woody biomass to an energy source:

• Thermal energy, electricity and transportation fuels from wood by John I. 

Zerbe. Forest Products Journal 56(1):6-14. 2006.

• Biomass as a feedstock for a bioenergy and bioproducts industry: The 

technical feasibility of a billion-ton annual supply. Perlack, R.D., L.L. 

Wright, A.F. Turhollow, R.L. Graham, B.J. Stokes and D.C. Erbach. 2005. 

DOE/GO-102995-2135 ORNL/TM-2005/66.

• Preliminary screening-Technical and economic assessment of synthesis gas 

to fuels and chemicals with emphasis on the potential for biomass-derived 

syngas. Spath, P.L. and D.C. Dayton. 2003. National Renewable Energy 

Laboratory NREL/TP-510-34929.

hydrogen, water, and methane that can

be used in internal combustion 

engines. These compounds can also 

be readily converted to numerous 

products, including hydrogen, 

methanol, ethanol, and liquid fuels. 

Liquid fuels, such as gasoline and 

diesel, are made from syngas through 

an additional process. This product is 

not the same as bio-diesel, which 

comes from the chemical reaction of 

vegetable or animal oils with methanol. 

Integrating both biochemical and thermochemical processes into one biorefinery, a single facility where biomass

could be converted to either ethanol or

syngas would allow the residuals from the

ethanol stage to be further utilized in the

thermochemical platform. This is similar

to existing petroleum refineries, in that

several energy products are made, along

with numerous value-added products,

maximizing the value of each.

There are various methods that convert energy stored in biomass into forms

that can be used for transportation or

industrial fuels. The products from these

transformations can also be used to

replace products currently derived from

petrochemicals. The advantages of biomass are well-documented with respect

to its renewable nature and environmental benefits. As such, woody biomass has the potential to be scaled up

commercially to make a significant contribution to the energy independence of

the United States. k
Volume 15, Issue Three | Inside Agroforestry 11

Potential

continued from page 3

increased dramatically. The primary reasons for this expanded interest have

been for economic diversification and

conservation benefits. Trees introduce

both vertical and horizontal structural

variation in agricultural landscapes.

Agroforestry adds plant and animal biodiversity to the landscape that might

otherwise contain only monocultures of

agricultural crops. Agroforestry can

serve to connect forest fragments and

other critical habitats in the landscape.

Perennial systems for biofuel 

production and their conservation

benefits

Several woody perennial species can be

grown for bio-fuels, while at the same

time provide conservation benefits and

ecological services that markedly exceed

those associated with conventional

annual crops like corn. In the United

States most research has focused on

willow shrubs and hybrid poplar production systems.

• Willow – High yields, ease of 

propagation, broad genetic base, 

short breeding cycle, and ability to 

resprout after multiple harvests make 

willow ideal. Yields of fertilized and 

irrigated willow grown in three-year 

rotations have exceeded 10.8 dry 

tons/acre/year.

• Hybrid poplar – Genetically 

improved cottonwoods and interspecific hybrids have been selected 

for fast growth. A 5 dry tons/acre/

year yield represents a reasonable 

national average.

Research needs

Although several production systems

have already been devised for hybrid

poplar and willows, more research is

needed to improve the efficiencies and

sustainability of these perennial systems.

A better understanding is needed of

how to manipulate the plant’s natural

production of specific components

already found in the crop such as cellulose, hemicellulose, and lignin to

increase energy yields and reduce conversion costs. These efforts will need to

be jointly pursued by the forestry and

agricultural sectors with an understanding of the barriers and challenges

impacting land availability, producer

adoption, and key issues surrounding

soil sustainability. k

Adapted from: Perennial crops for biofuels and conservation, by Gregory Ruark,

Scott Josiah, Don Riemenschneider, and

Timothy Volk.

Short rotation woody crops can be incorporated into agroforestry practices like windbreaks and riparian forest buffers or grown as part of a tree plantation. NAC file photo

Agricultural energy

Agricultural lands can provide nearly 1 billion dry

tons of sustainably collectable biomass and still 

continue to meet food, feed, and export demands. 

This estimate includes 446 million dry tons of 

crop residues, 377 million dry tons of perennial 

crops, 87 million dry tons of grains used for biofuels, and 87 million dry tons of animal manures,

process residues, and other residues generated in 

the consumption of food products. k
USDA National Agroforestry Center

East Campus–UNL

Lincoln, NE 68583–0822

PRSRT STD

POSTAGE & FEES PAID

USDA — FS

PERMIT NO G-40

February 4–8, 2007

Sixty-First Annual Meeting Of The 

National Association Of Conservation 

Districts (NACD): “Power Of 

Conservation.” Los Angeles, CA. 

Contact: 202–547-6223, 2007@

nacdnet.org, http://2007.nacdnet.org.

February 27, 2007

Ecosystem Service Markets: 

Everyone’s Business. Houston, TX. 

Contact: Jan Davis, 979–458–6630, 

jdavis@tfs.tamu.edu, or Dr. Neal Wilkins, 

979–845–7726, nwilkins@tamu.edu,

http://tfsregister.tamu.edu.

April 9–12, 2007

Emerging Issues Along Rural/Urban 

Interfaces II. Atlanta, GA. Contact:

Dr. David Laband, 334–844–1074, 

labandn@auburn.edu, www.sfws.

auburn.edu/urbanruralinterfaces/.

Official Business

Penalty for Private Use, $300

Address Service Requested

InsideAgroforestry VOLUME 15 ISSUE THREE

Upcoming Events

“Inside Agroforestry” is published three times per year by the

USDA National Agroforestry Center. Phone: 402–437–5178;

Fax: 402–437–5712.

• Greg Ruark, NAC Program Manager (256–372–4540)

• Michele Schoeneberger, FS Research Lead (ext. 21)

• Rich Straight, FS Lead Agroforester (ext. 24)

• Bruce Wight, NRCS Lead Agroforester (ext. 36)

• Kimberly Stuhr, Technology Transfer Specialist/

“Inside Agroforestry” Editor (ext. 13)

• Ryan Dee, Technology Transfer Assistant/

“Inside Agroforestry” Designer (ext. 14)

www.unl.edu/nac

Mission

The USDA National Agroforestry Center (NAC) is a partnership of

the Forest Service (Research and Development and State and

Private Forestry) and the Natural Resources Conservation Service.

It is administered by the Forest Service, Southern Research Station;

and its program manager and headquarters are located in Huntsville,

AL, on the campus of Alabama A&M University, while NAC’s staff

are located at the University of Nebraska, Lincoln NE; University of

Idaho, Moscow ID, and in Blacksburg, VA. NAC’s purpose is to

accelerate the development and application of agroforestry technologies to attain more economically, environmentally, and socially

sustainable land use systems. To accomplish its mission, NAC interacts with a national network of partners and cooperators to conduct

research, develop technologies and tools, establish demonstrations,

and provide useful information to natural resource professionals.

Policy

USDA policy prohibits discrimination

because of race, color, national origin,

sex, age, religion, or handicapping condition. Any person who believes he or

she has been discriminated against in

any USDA-related activity should

immediately contact the Secretary of

Agriculture, Washington, DC 20250.

Opinions expressed in “Inside

Agroforestry” are those of the author

and do not necessarily represent the

policy of the USDA Forest Service and

the USDA Natural Resources

Conservation Service.

June 10–13, 2007

Tenth North American Agroforestry 

Conference. Québec, Canada. Contact: 

info@agrofor2007.ca, 

www.agrofor2007.ca.

For more upcoming events, visit our 

website calendar: 

www.unl.edu/nac/calendar.htm.