ORNL/TM-2007/109

 

 

Historical Perspective on How and 

Why Switchgrass was Selected as a 

“Model” High-Potential Energy Crop 

July 2007 

Prepared by 

Lynn Wright 

Consultant to Bioenergy Resources and Engineering Systems 

Environmental Sciences Division 
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ORNL/TM-2007/109 

. 

Environmental Sciences Division 

HISTORICAL PERSPECTIVE ON HOW AND WHY SWITCHGRASS 

WAS SELECTED AS A "MODEL" HIGH-POTENTIAL ENERGY 

CROP 

 

 

Lynn Wright, 

Consultant to Bioenergy Resources and Engineering Systems 

Date Published: August 2007 

Prepared by 

OAK RIDGE NATIONAL LABORATORY 

Oak Ridge, Tennessee 37831-6283 

managed by 

UT-BATTELLE, LLC 

for the 

U.S. DEPARTMENT OF ENERGY 

under contract DE-AC05-00OR22725 
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CONTENTS 

Page 

LIST OF FIGURES................................................................................................................................ v 

LIST OF TABLES ...............................................................................................................................vii 

EXECUTIVE SUMMARY................................................................................................................... ix 

ABSTRACT ........................................................................................................................................... 1 

1. INTRODUCTION ........................................................................................................................... 1 

1.1 BIOFUELS FEEDSTOCK DEVELOPMENT PROGRAM BACKGROUND .................... 2 

1.2 GOALS OF THE HERBACEOUS CROPS PROGRAM SOLICITATION ......................... 2 

2. HERBACEOUS CROP SCREENING ............................................................................................ 4 

2.1 DESCRIPTION OF THE HERBACEOUS SCREENING PROJECTS ................................ 4 

2.2 SCREENING TRIAL RESULTS AND RECOMMENDATIONS ....................................... 7 

2.1.1 Virginia Tech - Virginia............................................................................................ 8 

2.1.2 Auburn University - Alabama................................................................................... 9 

2.1.3 Geophyta - Ohio........................................................................................................ 9 

2.1.4 Cornell University – New York .............................................................................. 10 

2.1.5 Purdue University - Indiana .................................................................................... 11 

2.1.6 Iowa State University - Iowa................................................................................... 11 

2.1.7 North Dakota State University – North Dakota ...................................................... 12 

2.1.8 Oak Ridge National Laboratory - Tennessee .......................................................... 14 

3. HERBACEOUS CROP PROGRAM CONSIDERATIONS ......................................................... 15 

3.1 HECP GOALS, ANALYSIS AND DATA SYNTHESIS ................................................... 15 

3.2 BFDP FUNDING EFFECTS ON MODEL SPECIES SELECTION .................................. 18 

4. HIGH POTENTIAL FEEDSTOCKS ............................................................................................ 20 

4.1 HERBACEOUS CROPS CONSIDERED HIGH POTENTIAL IN 2006 ........................... 20 

4.2 BIOFUELS FEEDSTOCK SELECTION CRITERIA......................................................... 21 

4.2.1 1980s Selection criteria........................................................................................... 21 

4.2.2 1990s Selection criteria........................................................................................... 22 

4.2.3 2000s Selection criteria .......................................................................................... 23 

5. CHARACTERISTICS OF THE SWITCHGRASS “MODEL”..................................................... 26 

6. CONCLUSION.............................................................................................................................. 30 

7. REFERENCES .............................................................................................................................. 31 

Appendix A: AUBURN UNIVERSITY YIELD RESULTS ............................................................... 35 

Appendix B: GEOPHYTA YIELD RESULTS.................................................................................... 37 

Appendix C: PURDUE UNIVERSITY YIELD RESULTS ................................................................ 39 

Appendix D: IOWA STATE UNIVERSITY YIELD RESULTS........................................................ 41 

Appendix E: NORTH DAKOTA STATE UNIVERSITY YIELD RESULTS.................................... 43 

iii 
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LIST OF FIGURES 

Figure Page 

 1 Location of herbaceous crops field testing sites ................................................................. 4 

 2 Woody and herbaceous species considered by the Department of Energy’s Biofuels 

Feedstock Development Program in 1991 as having high potential as energy crop 

feedstocks.......................................................................................................................... 18 

 3 Funding History of the Biofuels Feedstock Development Program between 1978 

and 1998............................................................................................................................ 19 

v 
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LIST OF TABLES 

Table Page 

 1 Species screened by the Herbaceous Crops Program between 1986 and 1992 .................. 5 

 2 Descriptions of herbaceous crop screening test sites .......................................................... 6 

 3 Mean biomass yield averaged across 12 sites for eight herbaceous biomass species 

on three soil types in the Piedmont of Virginia .................................................................. 8 

 4 Average yields of the three highest-yield consecutive years during the first 5 years 

of production of perennial biomass crops grown in the eastern Great Lakes Region....... 10 

 5 Yields of herbaceous biomass crops grown at four sites in Indiana during the 

drought year of 1988......................................................................................................... 12

 6 Costs and break-even prices of the crop production systems evaluated in Iowa 

1988-1992 ......................................................................................................................... 13 

 7 Computed soil loss (mean of three sites) of eight no-till-planted species at four 

locations (three soils) in the Piedmont.............................................................................. 16 

 8 Estimated soil loss under thirteen crop systems at two Iowa locations using the 

Universal Soil Loss Equation (USLE).............................................................................. 16 

 9 Species recommended for further development or study by the seven herbaceous 

screening projects . ........................................................................................................... 17 

 10 Feedstock criteria, criteria relevance categories, and ranking (high, medium and 

low) of the capability of switchgrass to meet those criteria for cellulosic ethanol 

production systems ........................................................................................................... 26

vii 
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ACKNOWLEDGMENTS 

Thanks to Anthony Turhollow, Shahabaddine Sokhansanj, Ethan Davis, Robert Perlack and Mark 

Downing for their reviews of the document. Much credit goes to Janet Cushman, Anthony 

Turhollow, Sandy McLaughlin and Lynn Kszos for the many reports and papers on herbaceous crops 

they prepared during their tenures as manager and/or project leaders of herbaceous crops research at 

ORNL during the 1980s and 1990s. Those documents provided a great deal of the information 

summarized in this paper. Much credit also goes to the many researchers who carried out the 

herbaceous crops screening trials and concluded those trials with excellent report documenting the 

results. I thank the current managers of the biomass research effort at Oak Ridge National Laboratory 

(ORNL), Jonathon Mielenz and Mark Downing, for allowing me the opportunity to continue to 

contribute to the biomass effort by providing historical documentation of a significant decision made 

by the program during my tenure as a biomass research leader at ORNL. Most importantly, I would 

also like to acknowledge the long term support of energy crops research since 1978 by the 

Department of Energy’s Biomass Program within the office of Energy Efficiency and Renewable 

Energy and particularly the support of John Ferrell, Sarah Sprague and other feedstock program 

managers. 

EXECUTIVE SUMMARY 

The screening trials funded by the U.S. Department of Energy in the late 1980s to early 1990s 

assessed a wide range of about 34 species with trials being conducted on a wide range of soil types in 

31 different sites spread over seven states in crop producing regions of the U.S. While several species 

were identified as having merit for further development, the majority of institutions involved in the 

herbaceous species screening studies identified switchgrass as having high priority for further 

development. Six of the seven institutions either included switchgrass among the 2-3 species with 

highest potential in their region, or recommended that further research be done on switchgrass in their 

region. All institutions recommended that perennial grasses be given high research priority. The 

Virginia and Alabama projects, had the most success with switchgrass and produced some of the most 

persuasive information showing the merits of switchgrass – especially the potential for high yields, its 

deep rooting characteristics, and its potential value in carbon sequestration. The projects in Indiana, 

Iowa, and North Dakota all came to the conclusion that switchgrass merited further development as a 

bioenergy crop primarily after conducting economic analysis, since visual results of crop yields most 

often led toward favoring sorghum systems. In some cases, additional characteristics such as more 

favorable conversion characteristics or lower erosion potential increased the interest in switchgrass. 

In the case of the projects in Ohio and New York, both with several poorly drained test sites, the case 

for switchgrass was not as strong due to problems with establishment and weed control. The New 

York project did conclude that switchgrass had desirable characteristics and should receive more 

evaluation in the region. The Geophyta project did not include switchgrass among the top three 

yielding crops in their trials, but it was the 4th best performer and was achieving yields equivalent to 

or greater than other crops by the 4th year of the study. The other crop(s) which were identified as 

having high potential by several of the projects included some type of sorghum (sweet sorghum, 

forage sorghum or sorghum x sudangrass) and reed canarygrass. Additionally, there were a few 

species or species mixtures unique to a single site that appeared to merit further consideration such as 

sericea lespedeza and energy cane in Alabama and alfalfa/bromegrass in New York. The Oak Ridge 

project and at least three of the screening projects also identified mixed species “meadow”, “old field” 

or “weed” trials as possibly being economically viable production systems even though yields were 

relatively low. 

ix
Economic and environmental assessments by Oak Ridge National Laboratory’s Biofuels Feedstock 

Development Program staff together with the screening project results and funding limitations lead to 

making the decision in 1991 to invest future Department of Energy research funds primarily in 

switchgrass as a “model” or “prototype” bioenergy crop. This selection was justified in the 1992 

Annual Progress Report (1) of the Department of Energy’s Biofuels Feedstock Development Program 

(BFDP) with the following statement: 

“In 1984, a series of ten herbaceous research projects began at widespread locations across 

the eastern and Midwestern United States. A total of 35 species was examined in these initial 

screening studies, which were designed to examine yield potential, biochemical composition, 

and best management practices across a wide diversity of sites. The completion of several of 

these studies and the examination of data on yield potential, production economics, and 

regional site potential, led in 1991 to the selection of a perennial forage grass switchgrass as 

a model species for further research. 

The rational for selection of a single species was to concentrate and thereby improve the 

overall efficiency of the many interrelated aspects of research that were seen as requisite for 

biofuels production. Although more than one species will certainly be required ultimately, 

switchgrass was seen as an excellent beginning with the available programmatic resources. 

The selection of switchgrass as a model species was based on several important 

considerations. As a widely adapted endemic species of the tall grass prairies, switchgrass 

has demonstrated a capacity for high yields on relative poor quality sites. Maximum annual 

yields on test plots in Auburn, Alabama, have been 33 dry Mg ha-1, well above the production 

level considered prerequisite for a successful biofuels industry. A large and deep root system 

is the key to high production and soil improvement on poor quality sites. Research at 

Virginia Polytechnic Institute and State University has shown that soil organic carbon was 

increased by 30% during a 4-year cycle, indicating that switchgrass has a significant 

capacity to improve soil quality by sequestering carbon belowground. Improved erosion 

control, reduced fertilizer and pesticide requirements and a capacity for providing wildlife 

cover are additional positive environmental attributes. An important quality of switchgrass 

is its strong potential appeal to landowners, for whom cultivation of a perennial crop that 

can be grown, harvested, and stored with conventional equipment represents an easy 

interface with current agricultural practices.” 

It should be noted that the exceptionally high yield of 33 dry Mg ha-1 was not an outcome of the 

original herbaceous screening trials, but was observed in 1989 in a 2nd year switchgrass variety trial 

established by Auburn University in 1988, mid-way during the screening trial phase of work. The 

results were published in 1991.(2) This variety trial showed that the original switchgrass variety 

chosen for the screening trials (Cave-in-Rock) was probably not the best selection for many of the 

screening locations. The high yield potential of the new variety, Alamo, was first identified by the 

Auburn trial. 

Selection of switchgrass as a model species in 1991 lead to a switchgrass specific solicitation and 

then to 10 years of switchgrass development at ten institutions under the management of Sandy 

McLaughlin and others at ORNL.(3) More recently switchgrass has been the focus of investigations at 

several additional universities and private institutions. New varieties have been developed and 

released, management techniques have been improved, and much more is now known about how 

switchgrass can be harvested, handled, stored and converted to ethanol or used to produce power. 

Now, in 2007, it is very apparent that while switchgrass may not be a perfect energy crop (and there 

may not be a perfect crop), it has many valuable characteristics that will result in its continuing to be 

x
xi

not only a “model or prototype” for crop development, but also one of the more sustainable 

feedstocks for the production of renewable alternative fuels in the U.S. 

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ABSTRACT 

A review of several publications of the Biofuels Feedstock Development Program, and final reports 

from the herbaceous crop screening trials suggests that there were several technical and non-technical 

factors that influenced the decision to focus on one herbaceous “model” crop species. The screening 

trials funded by the U.S. Department of Energy in the late 1980s to early 1990s assessed a wide range 

of about 34 species with trials being conducted on a wide range of soil types in 31 different sites 

spread over seven states in crop producing regions of the U.S. While several species, including 

sorghums, reed canarygrass and other crops, were identified as having merit for further development, 

the majority of institutions involved in the herbaceous species screening studies identified switchgrass 

as having high priority for further development. Six of the seven institutions included switchgrass 

among the species recommended for further development in their region and all institutions 

recommended that perennial grasses be given high research priority. Reasons for the selection of 

switchgrass included the demonstration of relatively high, reliable productivity across a wide 

geographical range, suitability for marginal quality land, low water and nutrient requirements, and 

positive environmental attributes. Economic and environmental assessments by Oak Ridge National 

Laboratory’s Biofuels Feedstock Development Program staff together with the screening project 

results, and funding limitations lead to making the decision to further develop only switchgrass as a 

“model” or “prototype” species in about 1990. This paper describes the conditions under which the 

herbaceous species were screened, summarizes results from those trials, discusses the various factors 

which influenced the selection of switchgrass, and provides a brief evaluation of switchgrass with 

respect to criteria that should be considered when selecting and developing a crop for biofuels and 

bioproducts. 

1. INTRODUCTION 

Switchgrass was selected as a “model” energy crop species deserving of further research in 1991. 

This selection was briefly explained and justified in at least three previous publications of Oak Ridge 

National Laboratory including the 1992 Annual Progress Report(1) of the BFDP, a proceedings paper 

published in 1992,(4) and the switchgrass research summary paper published in 2005.(3) 

The 1992 proceedings paper by McLaughlin(4) described several important considerations for 

selecting switchgrass as the model species. A very important one was that the land base for 

switchgrass was believed to be quite large and varied because of demonstrated high yields on 

relatively poor quality sites and because of its deep rooting characteristic. McLaughlin noted that the 

land most likely to be used for herbaceous crop production is the approximately 48 million acres of 

marginal land that has severe restrictions for conventional crop production. Given the assumption that 

such land would be utilized for production of switchgrass, then a wide range of environmental 

benefits could occur including improvement of soil carbon by sequestering carbon belowground, 

improved erosion control, reduced fertilizer and pesticide requirements (relative to conventional 

annual crops), and a capacity for providing wildlife cover. Similar reasons were described in the 

1982 Annual Progress Report of the BFDP and quoted in the executive summary of this document. 

The focus on a single species was a departure from the original strategy envisioned by the managers 

of the Herbaceous Crops Program (HECP) at Oak Ridge National Laboratory (ORNL). A 1991 paper 

presented by the ORNL Herbaceous Crops Program managers at a national biomass meeting(5)

described the desirability of selecting at least one annual, one perennial, and one legume for further 

research. 

1
A review of several publications of the Biofuels Feedstock Development Program, and final reports 

from the Herbaceous Crop screening trials suggests that there were both technical and non-technical 

factors that influenced the decision to focus on one herbaceous “model” crop species. This paper will 

summarize reported results, discuss the various factors which influenced the selection of switchgrass, 

and provide a brief updated evaluation of switchgrass with respect to selection criteria considered 

important then and now. 

1.1 BIOFUELS FEEDSTOCK DEVELOPMENT PROGRAM BACKGROUND 

The Department of Energy became involved in supporting the development of biomass resources as 

early as 1976 when DOE’s Biomass Systems Branch initially funded several systems analysis studies 

on sugar crops, agricultural residues, wood energy farms, grains and grasses and aquatic plant 

production. DOE’s first funded field studies on bioenergy crops in 1977 by co-funding work that had 

been initiated by USDA on woody crops, sugar cane, and tropical grasses. DOE quickly established 

its own energy crop research effort with the issuance of two Program Research and Development 

Announcements on “Fuels from Woody Biomass” and “Fuels from Aquatic Species”. Oak Ridge 

National Laboratory was asked by DOE in 1978 to provide advice and support in the selection and 

management of the woody biomass projects and the Solar Energy Research Institute supported the 

aquatic research effort. By 1982, DOE had fully transferred technical and administrative 

management of the Short Rotation Woody Crops Program to ORNL and by 1984, DOE provided 

funds to ORNL to develop an Herbaceous Energy Crops Program. 

Prevailing assumptions in the early 1980s about best potential herbaceous energy crops species are 

documented by a publication entitled “The Production of Herbaceous Feedstocks for Renewable 

Energy”, published September 1986 by the Solar Energy Research Institute.(6) This document 

described the major reasons for interest in herbaceous crops including: (1) the idea that it would be 

relatively easy for the agricultural production sector to switch to production of herbaceous biomass 

crops, (2) the assumption that alternative crops could be attractive to a depressed farm economy, and 

(3) that herbaceous crops might be more suitable than woody crops as feedstocks for fermentation 

alcohol and anaerobic digestion. However, it is interesting that the twelve “representative” 

herbaceous crops described by the SERI document(6) included crops grown for both carbohydrate and 

cellulosic components. The carbohydrate crops included sugarcane, sweet sorghum, sweet-stemmed 

grain sorghum, Jerusalem artichoke, sugar beets, and fodder beets. The lignocellulosic crops 

described included kenaf, napiergrass, alfalfa, reed canarygrass, common reed, and water hyacinth. 

After reviewing all of the pros and cons of various approaches, the Herbaceous Crops Program 

Managers at ORNL chose to develop a program solicitation that excluded crops grown primarily for 

carbohydrates and instead chose to solicit proposals limited to research on cellulosic crops. The goals 

of the original program solicitation were very important to setting the agenda and the basic criteria for 

selecting species for further development. 

1.2 GOALS OF THE HERBACEOUS CROPS PROGRAM SOLICITATION 

The Herbaceous Energy Crops Program (HECP) was initiated in 1984 with a request for proposals 

(RFP) focused on the southeast (exclusive of subtropical areas) and the Midwest/lake States.(7) The 

focus on grass and legume herbage was based on a government report(8) that had identified these 

biomass resources as second in size only to wood. The overall goal of the HECP was stated to be “to 

develop data and information that will lead to commercially viable systems for producing herbaceous 

biomass for fuels and energy feedstocks.” A very important element of the HECP was the desire to 

achieve the goal in ways that would minimize adverse environmental effects.(9) The direction of the 

2
HECP and some of the important criteria were clearly established in the technical discussion section 

of the initial RFP(7) as evidenced by the following words in the proposal description: 

“Three major factors influenced the initial focus of research in the program. First was the 

desire to increase the production of biomass for energy without significantly reducing food 

production. This led to the decision to concentrate on species for marginal croplands and on 

species that can be grown as winter crops. Second was the decision to produce fuels or 

energy feedstocks rather than chemicals. This meant the program would initially include a 

minimum of research on hydrocarbon crops, because evaluations of hydrocarbon-producing 

species that will grow in the United States have concluded that the hydrocarbon productions 

will be more valuable as specialty chemicals, primarily lubricants, than fuels. Third was the 

desire to have the greatest possible impact on total biomass energy use. This led to the 

decision to emphasize lignocellulosic crops. ” 

Proposals were scored on the basis of (1) demonstration of a through understanding of the proposed 

work, (2) application of the proposed work of the Herbaceous Energy Crops Program to the targeted 

regions, (3) the degree of private sector participation, (4) qualifications of the personnel, and (5) 

availability of facilities and equipment. 

While the initial work focused on screening species to identify high-potential candidates, the 

solicitation’s statement of work(7) recommended that different intensities of management be part of 

the initial screening process. The statement of work also clarified that while the focus was on 

marginal land, the proposals should include a range of site types, including some good agricultural 

land, so that relationships among site quality, management inputs, and yields could be established. 

Land was considered to be marginal if it was limited by erosiveness, excessive wetness, soil 

chemistry constraints, rooting constraints, or climate issues. While the original RFP(7) did not 

explicitly state that environmental concerns would be a factor in the selection of species for further 

research, the fact that an evaluation of soil loss potential was a required component of the proposals 

demonstrated a concern for environmental effects of the cropping systems. 

Responsive proposals were required to screen at least two species, one of which had to be a forage or 

hay crop commonly grown in the test site region. The other crop(s) could be annual or perennial and 

they could be common or less common species, however their inclusion had to be explained and 

justified. Thirteen proposals were received from a total of twelve institutions. Several of those were 

deemed not responsive to the RFP(7) either because of the species proposed or because the trials 

would be located in sub-tropical regions of the country. Thus, only seven proposals merited serious 

review. Five organizations were selected to participate in the southeastern and Midwest species 

screening trials that began in 1985. The HECP annual report for 1985(10) described the recently 

initiated herbaceous crop screening research projects and defended the rational for focusing the 

research in the southeast and Midwest/lake areas. Those regions were chosen for study because large 

areas of marginal cropland are potentially available and there are relatively few environmental 

restrictions on productivity. In 1988, two additional institutions were added to the species screening 

effort to achieve a broader coverage of potentially available site types. 

3
2. HERBACEOUS CROP SCREENING 

2.1 DESCRIPTIONS OF THE HERBACEOUS SCREENING PROJECTS 

Six universities and one private company were selected to participate in the herbaceous screening 

projects (Fig. 1). The universities included Cornell University, Virginia Polytechnic Institute and 

State University (referred to as Virginia Tech), Auburn University, Purdue University, Iowa State 

University, and North Dakota State University. The seventh research group was a small company in 

Ohio named Geophyta. 

Figure 1. Location of herbaceous crop field testing sites 

The proposals included the testing of warm season, cool season, and leguminous perennials in each 

area as well as several annuals. Annuals were also planted for comparison purposes. Table 1 shows 

the full range of species tested by each institution involved in herbaceous screening research. Table 2 

provides information about each of the test sites used for the screening trials in the southeast, 

Midwest/Lake, and Great Plains regions respectively. 

4
Table 1. Species screened by Herbaceous Crops Program 1986-1992 

Species Institution and year of project start 

VA Tech Auburn Geophyta Cornell Purdue ISU1 NDSU2

1985 1985 1985 1985 1985 1988 1988 

Grasses: Annual 

Corn (w) X X X X 

Pearl millet (w) X4

Foxtail millet (w) X 

Rye (c) X3 X3 X3 X3

Sorghum, Forage (w) X X 

Sorghum, Sweet (w) X4 X X 

Sorghum x sudangrass (w) X X X 

Sudangrass (w) X 

Grasses:Perennial 

Bahiagrass (w) X 

Bermudagrass (w) X4

Big bluestem (w) X X 

Crested wheatgrass (c) X 

CRP mixture of grasses (c/w) X 

Eastern gamagrass (c) X 

Energy Cane (w) X 

Intermediate wheatgrass (c) X 

Johnsongrass (w) X4

Napiergrass (w) 

Redtop (c) X 

Reed canarygrass (c) X X X5 X X 

Smooth bromegrass (c) X 

Switchgrass (w) X X X X X X X 

Tall Fescue (c) X X X X5

Timothy (c) /redtop (c)/ clover X X 

Weeping lovegrass (w) X X 

Wheatgrass mixture (c) X 

Legumes: Annual 

Soybeans X 

Legumes: Perennial 

Alfalfa X X6 X X7 X6

Birdsfoot trefoil X X X X 

Crownvetch X 

Flatpea X X 

Serecia lespedeza X X X 

Sweet clover X X 

Other

Forage brassica X 

Kale X 

Meadow (mixed grasses & 

legumes) X 

Note: The grasses are designated as either cool season (c) or warm season (w) crops. 1 ISU = Iowa State University 

2 NDSU = North Dakota State University 

3

 Rye was always interseeded among other species or as the cool season species in a double crop system – most often with 

sorghums 

4

 These crops were frequently the base species in a double-cropping or intercropping systems 5

 Reed canary grass and tall fescue were grown alone and interseeded with sorghum 6

 Alfalfa was intercropped with bromegrass at both Cornell and NDSU, and also grown alone at NDSU 7

 Alfalfa was intercropped with sorghum and sorghum x sudangrass 

5
Table 2. Descriptions of herbaceous crop screening test sites 

Location name Soil type Slope and class Quality Limitation(s) 

Virginia Tech 

(Virginia) 

3 locations, __ sites, soils representative of the piedmont region of the 

southeastern U.S., sloping, southwest facing (hot and dry) (11,12) 

Lunenberg County Appling 

 sandy loam 

6 & 7% slopes Poor, 

Coarse textured 

Strongly acidic 

highly erosive 

low nutrient 

Amelia County 

NE facing slopes 

3 sites 

Cecil 8 & 9% slopes Poor, 

Long-term erosion 

Acidic 

highly erosive 

Orange County Davison 9 &10% slopes Not quite as poor Strongly acidic, 

highly erosive 

Auburn (Alabama) 4 sites represent the physiographic provinces of AL, “all soils good for crop 

production if erosion minimized on slopes” (13) 

Camden – Lower 

coastal plain 

Mabis 

 fine sandy loam 

NA NA Fragipan and 

acidic subsoil, 

erosive 

Winfield – Upper 

coastal plain 

Savannah 

 loam 

2-10% slopes NA Fragipan and 

erosive 

Camp Hill- Piedmont Cecil 

 sandy loam 

NA NA Acidic, erosive 

Crossville- Sand 

Mountain site 

Hartsells 

 fine sandy loam 

2-5% slopes NA Erosive on slopes 

Geophyta (Ohio) 3 sites in northeast part of state with varying levels of wetness compared (14) 

Site 1 Toledo or Lucus 

silty clay 

0-2% Adequate soil pH 

and high fertility 

Occasional wetness 

Site 2 Toledo or Lucus 

silty clay 

2-6% Adequate soil pH 

and fertility 

Moderate wetness, 

no tile 

Site 3 Toledo or Lucus 

silty clay 

0-2% Low soil pH, low 

available P 

Frequent wetness, 

no tile 

Purdue (Indiana) 3 regions of state, range of soil qualities and slope effects compared (15) 

Purdue Agronomy 

Farm 

Chalmers 

 silty clay loam 

0-2% slope Good Minimal 

SIPAC (Southern 

Purdue Agricultural 

Center) 

Zanesville 

 silt loam 

8-12% slope Marginal, Previous 

crop tall fescue 

Fragipan, erosion, 

droughty 

SEPAC (Southeastern 

Purdue Agricultural 

Center) 

Cincinnati 

 silt loam 

8-10% slope Marginal, Previous 

crop tilled corn 

Erosion, fragipan, 

poor drainage 

T-FLAT 

(West central 

Throckmorton Purdue 

Agricultural Center) 

Slidell 

 silt loam 

0-2% slope Excellent, Previous 

crop tilled corn 

Minimal 

T-SLOPE 

(West central 

Throckmorton Purdue 

Agricultural Center) 

Slidell 

silt loam 

6-8% slope Excellent, Previous 

crop tilled corn 

Erosion 

Cornell 

(New York) 

8 sites with 6 soil series, each a unique combination of use and production 

limitations (16) 

Poole farm Geneva, Honeoye, 10% slope Excellent Erosion 

6
NY silt loam 

Aurora, NY Finger 

Lakes area 

Kendia, 

 silt loam 

Minimal Prime None 

Mt Pleasant farm, 

Freeville, NY 

Mid-south NY 

Mardin, 

 acid glacial till 

Minimal Marginal 

 

Strongly acid, 

low fertility, 

fragipan 

Halme farm, Ithaca, 

NY Finger lakes 

Erie soil, 

 fine silt 

Minimal Marginal Wetness, acidity, 

stones, low-fertility 

Caldwell farm, Ithaca, 

NY 

Collamar, 

 fine textured 

Less slope Marginal Erodible 

Caldwell farm, Ithaca, 

NY 

Collamar, 

 fine textured 

More slope Marginal Erodible 

Willsboro farm 

Northeast, NY 

Rhinebeck, 

 fine texture clay 

Minimal Marginal Wetness 

Willsboro farm 

Northeast, NY 

Mardin, 

 fine texture clay 

Minimal Marginal Wetness 

Iowa State 

(Iowa)

2 regions of state plus good and marginal soils compared (17) 

Ames –central Iowa Harps soil 

Silty clay loam 

0-1% slope 

Class I 

SOM = 7% 

Highly productive 

Corn/soybean/oat 

rotation in 1987 

pH of 8.0 

2 m rooting depth 

Chariton – southern 

Iowa 

Clarinda, Cearfield 

and Grundy soils 

2-7% slope 

Class III 

SOM 4% 

Lower productivity 

soil 

Conventional red 

clover prior use 

Erosive 

Droughty 

pH of 6.8 

North Dakota State 

Univ (ND)

5 dryland sites and 1 irrigated site representing 3 major soil areas in North 

Dakota (18) 

(1) Prosper 

Red River Valley 

Gardena 

Silt loam 

level Productive, 

Lacustrine sediments 

Moderate rainfall 

(2) Hettinger 

Missouri Plateau 

Shambo 

Silt loam 

0-2% Productive, Alluvium Very low rainfall 

(3) Glenfield a 

Drift Prairie 

Barnes loam to 

Siva loam 

NA Productive, Glacial 

till 

Low rainfall 

(4) Leonard 

Red River Valley 

Hecla 

Loamy fine sand 

Nearly level Marginal,CRP land Wind erosion 

Moderate rainfall 

(5) Glenfield b 

Drift Prairie 

Buse loam Crests of hills Marginal, CRP land, 

Glacial till 

Low rainfall 

(6) Carrington Emrick loam level Productive with 

irrigation; glacial till 

Requires 

irrigation 

2.2 SCREENING TRIAL RESULTS AND RECOMMENDATIONS 

Yields of each crop were quite variable between investigators, sites, and years representing not only 

site and climate variations but also a lack of experience in growing some of the perennial grasses as 

crops. Yield results derived from tables in the final reports of the herbaceous crop screening trials are 

either included in the descriptions below (if short) or provided in the appendixes (if long). Because 

climate conditions had a large effect on establishment success and yield results, particular notice is 

made of the principal investigators comments about climate conditions during their trials. When final 

reports included recommendations for further research, an effort is made to capture those 

recommendations in the discussion below about each of the herbaceous crop screening projects. An 

eighth project, a study of the potential of successional vegetation to be a bioenergy feedstock, is also 

described. 

7
2.1.1 Virginia Tech - Virginia 

Parrish et al. reported in 1990(11) that initial screening results were heavily affected by the severe 

drought that occurred during the first 4 weeks after the initial planting in 1985. Warm season 

perennial grasses survived but cool season grasses had to be reseeded several times in 1986 and grew 

poorly in 1987. These were both years with a moisture deficit. Rainfall was more nearly adequate in 

1988 and 1989, resulting in the cool season grasses and legumes showing a good response to the 

rainfall. However, across the 4 post-establishment years (86-89) with 2 years of drought and 2 years 

of average or above average rain, switchgrass clearly outperformed all the other species being tested 

including sorghum x sudangrass on 3 marginal agricultural soils (Table 3). Yields of sorghum x 

sudangrass were 3 times that of switchgrass in the establishment year (1985) and slightly higher in 

1986, but through the rest of the study sorghum x sudangrass yields trended downward while 

switchgrass yields continued to increase. On one site sorghum x sudangrass experienced near or 

complete failure in 2 years. Averaged over sites and years, the cool season grasses achieved an 

average of between 5 and 6 Mg ha-1 yr-1. Switchgrass averaged 10.6 Mg ha-1 yr-1, and weeping 

lovegrass, also a warm season grass, averaged 9.3 Mg ha-1 yr-1. These two species were 

recommended for further study by the Virginia Tech investigators. Following their own 

recommendations, Virginia Tech researchers initiated management studies focusing on switchgrass 

and weeping lovegrass in 1988.(12) While both species continued to show promise as relatively low 

input energy crops, yields and stand vigor declined in the weeping lovegrass trials after 4 years, thus 

switchgrass seemed to be the most promising species. More detailed studies on switchgrass by 

Virginia Tech demonstrated that no-till management could be successfully used to establish perennial 

grasses and to reduce soil loss on sloping marginal land and that the deep rooting depth of 

switchgrass was a contributor to its productivity and to soil carbon enhancement. 

Table 3. Mean annual biomass yield averaged across 12 sites for eight herbaceous biomass species on 

three soil types in the Piedmont of Virginia. 

Species 1986 1987 1988 1989 4-Year Avg 

----------------------------------------------------Mg ha-1------------------------------------------ 

Warm-Season 

 Sorghum-sudan 8.6 7.9 9.5 4.7 7.7 

 Lovegrass 8.7 8.9 11.2 8.2 9.3 

 Switchgrass 7.8 10.8 11.9 11.8 10.6 

 Sericea 3.1 6.4 7.7 7.4 6.1 

Cool-Season 

 Tall fescue 1.9 7.1 5.2 5.9 5.0 

 Crownvetch 0.9 4.1 8.2 9.7 5.7 

 Trefoil 1.0 6.5 6.0 7.4 5.2 

 Flatpea 1.6 3.5 4.9 10.7 5.2 

Note: Table reproduced from Parish et al.(11) 

8
2.1.2 Auburn University – Alabama 

The rainfall data reported by Bransby et al.(13) showed that across 4 physiographic regions in 

Alabama, growing season rainfall was near normal in the first two years (1985 and 1986), 

substantially below normal in 1987, and normal in 1988 and above normal in 1989. Yields of annual 

species were some to much higher than perennials in years of moderate to good rainfall but lower 

than perennials in lower rainfall years (Appendix A). For example, sweet sorghum yields varied from 

a mean of 17.93 Mg 

ha-1 yr-1 in 1985 to a low of 3.8 ha-1 yr-1 in 1987. Although switchgrass yields were low in the 

establishment year (2.44 Mg ha-1), yields increased over the next 4 years showing relatively little 

response to precipitation. The higher yield variability plus higher production costs of the annuals 

lead to the recommendation to drop annuals and to focus on perennials for future crop development. 

Johnsongrass, a warm season perennial “weed”, performed better than other perennials in the first two 

seasons. This was attributed to its larger seed size but johnsongrass growth decreased over time and 

was correlated with an increase in disease and soil compaction. All other warm season perennials, 

switchgrass, bermudagrass, and sericea lespedeza established more slowly but continued to increase 

yields over the 5 years achieving an average of 9 Mg ha-1 yr-1. The success and reliability of the 

perennials encouraged the Auburn University investigators to add evaluations of sub-tropical tall 

grasses in 1987 and a variety trial of switchgrass to the project in 1988. The tall grasses quickly 

achieved very high annual yields ranging from 12.2 up to 32.4 Mg ha-1 with energy cane showing the 

highest yields (16.5 to 32.4 Mg ha-1). The switchgrass established quickly in the normal rainfall year 

of 1988 and by 1989 the variety, Alamo, had achieved yields of 17.5 Mg ha-1, double that of the 

original test variety, Cave-in-Rock. The final report (13) recommended that further research should 

focus on only a few perennial species such as switchgrass, lespedeza, and energy cane. The 

advantages of switchgrass were described as: (a) it can be established from seed, (b) it can be 

harvested and stored as hay, (c) it can be used for both biomass and forage, (d) it has relatively low 

lignin content, and (e) the high genetic variability with the species provides excellent opportunities 

for improvement by selection and breeding. Bransby’s discovery of the high yield potential of the 

switchgrass variety, Alamo, was a major factor in the acceptance of switchgrass as a suitable model 

species.(2)

2.1.3 Geophyta – Ohio 

Wright reported in 1990(14) that planting efforts in 1985 and 1986 were affected by a combination of 

heavy rains initially followed by no or low amounts of rain. Wetness was a problem for only long 

enough to negatively affecting planting. Rainfall was not mentioned for 1987 and 1989, thus was 

assumed to be normal. 1988 was described as extremely dry. The investigator identified the most 

promising energy crops of the 10 evaluated in a wet area of northern Ohio as forage sorghum, rye 

cropped with sorghum x sudangrass, and reed canarygrass. However an investigation of the data, 

(Appendix C) shows that switchgrass showed the next highest average yields and demonstrated 

greater reliability. The switchgrass did establish at all three sites (which the reed canarygrass did not) 

and the switchgrass yields (4.1 – 9.0 Mg ha-1) were only a little less than those of reed canarygrass 

(5.1-10.3 Mg ha-1) on the two sites where both crops could be compared. Both of these grasses had 

their best yields in the 4th year (1989) when forage sorghum yields were very poor. Rye cropped with 

sorghum x sudangrass (yields ranging from 7.9 to 23 Mg ha-1) produced more reliable yields than 

forage sorghum alone, which had establishment failures in 1988 and 1989. The investigator did note 

that the cool season grasses (including reed canarygrass) always had green leaves (higher nutrient 

levels) at fall harvest, while switchgrass and sorghum had the lowest nutrient concentrations at fall 

harvest (suggesting greater potential for sustainable production). 

9
An interesting side observation of the study was that in control plots with no weed control it was 

noted that weed growth provided the majority of the biomass and weed-only plots provided 

respectable yields. Weed plots fertilized at the same level as the double crop of rye and sorghum x 

sudangrass produced yields in the range of 3.5 to 4.2 Mg ha-1. While the rye/sorghum x sudangrass 

combination produced much higher yields, the investigator noted that compared to the complete 

establishment failures that occurred with some crops in some years the idea of fertilizing abandoned 

fields merited further consideration.(14) 

2.1.4 Cornell University – New York 

Precipitation patterns in the Cornell University trials varied among the seven locations where crops 

were evaluated (15, 19) but followed a similar pattern to that experienced at other screening trials. The 

years of 1985 and 1988 experienced somewhat to seriously below normal precipitation, 1986 was 

closer to normal, 1987 had above and below normal precipitation depending on location, and 1989 

was generally normal or above for all sites. Eight energy crop species plus a “meadow” trial were 

evaluated. Yield results were relatively similar for most of the species tested (in the range of 4 to 10 

Mg ha-1) during the 3 best years (out of 5) of yield results (Table 4). Evaluation of the potential for 

energy crops in the region was based on modeling studies as well as on field trials. The investigators 

concluded that “careful management of better-drained” soil resources and proper selection of plant 

species grown for biomass will provide an annual yield of dry matter in the Great Lakes Region on 

the order of 10-12 Mg ha-1. The recommendations for the species with highest potential as a 

bioenergy crop varied for well drained versus the poorly drained soils. 

On moderately to well drained soils, the legume mixtures, alfalfa-bromegrass and timothy-redtop-red 

clover were considered to be the most promising.(19) Switchgrass was identified as showing promise 

for well-drained sites, but the establishment problems and weed competition experienced in the trials 

were a concern. The investigators did suggest that the variety used in the trials (Cave-in-Rock) was 

possibly not the best choice for the area and that more work on switchgrass was merited for the Great 

Lakes Region. On poorly drained soils, reed canarygrass out yielded all other species with average 

yields of about 7 Mg ha-1yr-1. It was recommended as a high potential species for poorly drained soils 

under a one-cut harvest system timed to coincide with drier soil conditions. The relatively low-input 

meadow plots were also observed to have potential for wet soils where tillage is not possible, with an 

average yield potential of 5 to 7 Mg ha-1 yr-1 with one or two harvests/year. 

Table 4. Average yields of the three highest-yield consecutive years during the first 5 years of production 

for perennial biomass crops grown in the eastern Great lakes Region 

Moderately to well drained sites Poorly drained sites 

Collamer Collamer 

(eroded) 

Honeoye 

(eroded) 

Mardin Madalin Rhinebeck Erie 

Species or 

mixture 

--------------------------------------------Mg ha-1------------------------------------------------------- 

Alfalfa/ smooth 

bromegrass 

8.88ab 10.01a 11.30a 

Eastern 

gamagrass 

6.07b 

Flatpea 9.48a 8.66b 9.49b 7.45a 

Naturalized 

meadow 

5.53ab 5.25ab 5.61b 

Reed canarygrass 7.13a 6.80a 9.02a 

Switchgrass 8.76ab 8.53b 5.79d 4.36b 4.85b 4.17b 

Timothy mixture 8.15b 10.14a 7.04c 7.35a 5.62ab 5.16ab 5.83b 

Note: means within a column followed by the same letter are not significantly different (P> 0.05).

10
2.1.5 Purdue University - Indiana 

Cherney et al. reported in 1990(16) that climate included both normal and droughty conditions during 

the years of 1985-1989 at all four sites used in testing, but no details were provided. The study 

evaluated 12 herbaceous crop species with some being considered both alone and as intercrop species. 

Of the perennial species investigated, switchgrass was deemed to have the greatest biomass potential 

yielding up to 16 Mg ha-1 in one season with two cuttings. When grown with minimal fertilizer inputs 

and one harvest per year, switchgrass was superior in yield to tall fescue, reed canarygrass, alfalfa, 

birdsfoot trefoil, weeping lovegrass, big bluestem, and sericea lespedeza. Annual yields of the 

switchgrass (Cave-in-Rock) were in the range of 7-16 Mg ha-1 with the lowest yield occurring in the 

drought year of 1988. Comparison of yields among crops in 1988 (a drought year) highlights the 

relative similarity of yields of several perennial grasses across good and poor sites in comparison with 

alfalfa and sorghums (Table 5). Advantages of switchgrass were described to be its minimum 

fertilizer input requirements, its persistence, and its effectiveness in reducing soil erosion. 

Establishment problems did occur with switchgrass at the poorest site. Response of switchgrass to 

fertilizer varied from year to year, but the greatest response was always between 0 and 50 kg N ha-1

with higher levels producing some to little additional response (Appendix D). 

Of the annual species evaluated, sweet sorghum produced higher yields than sorghum-sundangrass 

and corn, attaining up to 32 Mg ha-1 with one harvest in 1989. Several varieties of sorghum were 

tested with some attaining high yields on some sites even during the extreme drought year of 1988 

(Table 5). Average yields across the 4 sites for sweet sorghum were 22.2, 19.1, 15.8 and 8.9 Mg ha-1, 

respectively for the years 1985, 1986, 1987, and 1988. The large decline in 1988 was due to very low 

yields at 2 of the 4 testing sites. But additionally Cherney et al.(16) expressed concern that the decline 

in yields observed over the 4 year period was related to continuous sorghum culture as well as 

droughty conditions. Sorghum double cropped with rye was a very productive management option 

but required more inputs than switchgrass. Interseeding sorghum into perennial grasses was not a 

viable option due to its great dependence on environmental variables. However, no-till culture of 

sorghums did appear to be viable. Sweet sorghum yield response to fertilizer varied with year 

(Appendix D) . 

A separate analysis of the Purdue University screening results by Dobbins et al.(20) considered the 

economic potential of the crops in Indiana. The analysis indicated that biomass feedstock production 

could be economically viable on marginal land in the Midwest and could compete favorably for land 

with traditional crops. Sorghum-sudangrass, sweet sorghum, reed canarygrass, and switchgrass were 

all identified as promising crops for Midwest production. Based on production costs alone, the most 

promising crops appeared to be switchgrass and sweet sorghum. The results of a whole farm analysis 

suggested that reed canarygrass, switchgrass, and sweet sorghum were the alternatives that provided 

the best returns for the land, labor, and machinery resources available. 

2.1.6 Iowa State University - Iowa 

Anderson et al.(17) reported in 1994 that in the first two years of field trials rainfall was either 

significantly (1988) or somewhat (1989) below normal early in the season. During the rest of the 

screening period through 1992 rainfall was either significantly above normal (1990) or relatively 

normal. At the Chariton (a marginal site), reed canarygrass totally failed to establish in 1988, big 

bluestem established very poorly, and switchgrass and alfalfa had very low yields in the first year, 

though all perennials were re-established in 1989. However, several sorghum varieties and even corn 

did establish and produce acceptable yields at Chariton even in 1988. All crops successfully 

established at the Ames site. Yield results from both sites are summarized in Appendix E. The 

11
agronomic report from Iowa State University(17) provided an excellent summary of the screening 

Table 5. Yields of herbaceous biomass crops grown at four sites in Indiana during the drought year of 

1988.a

 

Site T-Flat 

(excellent 

cropland) 

T-Slope 

(excellent 

cropland) 

SEPAC 

(marginal 

cropland) 

SIPAC 

(marginal 

cropland) 

Species ---------------------------------------------Mg ha-1--------------------------------------- 

Alfalfa 17.36 13.28 9.98 1.62 

Birdsfoot trefoil 8.03 6.31 5.88 5.25 

Tall fescue 6.22 3.52 4.28 6.73 

Reed canarygrass 5.99 4.10 5.12 6.27 

Switchgrass 9.90 6.49 8.58 7.13 

Rye 3.88 3.29 3.42 2.42 

Sorghum x 

sudangrass 

4.86 4.26 11.19 12.77 

Sweet sorghum 2.20 1.70 12.77 21.03 a Yields averaged across fertilizer levels. 

results, but did not specifically make a recommendation for further energy crop research. Certainly 

the sweet sorghum and sorghum x sudangrass hybrids in a variety of cropping systems produced 

higher yields than any other annual or perennial species and maintained good yields under a variety 

of climate conditions. 

The economic report from Iowa State University showed that based on costs alone, the annual 

sorghums dominated the perennials grasses in both locations tested.(21) However, the economic 

analysis (Table 6) showed that the highest yielding perennial, switchgrass, competed well from an 

economic perspective with the sorghums, particularly with the intercropped sorghums which come 

closer to meeting environmental criteria. These results are bolded and highlighted by italics in 

Table 6. 

The Iowa State University economic report summary states: 

“The results for intercropped sorghum are mixed and depend on whether sufficient acres are 

produced to allow optimum equipment use. With optimum equipment use, intercropped sorghums are 

cheaper than switchgrass in central Iowa, but not southern Iowa. Soil conservation considerations 

clearly favor the perennial grasses or the intercrops.” 

2.1.7 North Dakota State University – North Dakota 

Meyer et al.(18) reported in 1994 that the establishment year of 1988 experienced record drought at all 

test locations. All perennial crops had to be reseeded with cool season grasses reseeded in fall 1988 

and warm season grasses reseeded the following spring and watered through summer to aid 

germination. Watering was necessary because 1989 also received below normal rainfall conditions. 

By September reasonable to good stands of grasses had been obtained but the legumes were not 

successful. Annuals successfully established even in 1988 but did not set grain in the driest site and 

produced low yields at most other sites. All sites but the most westerly one received above normal or 

normal rainfall in 1990 and 1991 and 1992 was a near normal rainfall year for 4 of the 6 sites.(22) 

12
 

Table 6. Costs and break –even prices of the crop production systems evaluated in Iowa 1988-1992 (from 

Anderson et al.(21) with English units converted to metric). 

Crop Systems Ames ($283 ha-1 land cost)1 Chariton ($197 ha-1 land1

cost) 

Yield ASC2 AC3 Yield ASC2 AC3

Monocrops dry Mg 

 ha-1

(dollar/dry Mg-1) dry Mg 

 ha-1

(dollar/dry Mg-1) 

 Alfalfa 9.86 41.05 69.81 7.77 52.78 

 Reed Canarygrass 7.46 51.68 89.67 10.60 36.94 55.54 

 Switchgrass 10.08 25.87 53.99 10.51 24.27 43.03 

 Big bluestem 8.60 33.13 66.08 7.95 35.33 60.12 

 Sweet sorghum 15.86 27.53 45.41 16.31 27.24 39.33 

 Sorghum x sudangrass 14.47 29.51 49.09 14.25 30.26 44.10 

Double Crops 

 Sweet sorghum/rye 15.72 36.52 54.54 13.89 41.99 56.18 

 Sorghum x sudangrass/Rye 14.52 38.98 58.51 13.87 41.80 56.02 

 Sweet sorghum3 14.96 26.48 45.42 16.02 25.40 37.71 

 Sweet Sorghum/Rye4 18.21 29.77 45.33 19.67 28.75 38.78 

Intercrop 

 Sweet sorghum/Alfalfa 13.89 31.48 51.89 9.61 45.03 65.55 

 Sorghum x sudangrass/Alfalfa 13.66 31.72 52.47 11.56 37.98 55.18 

 Sweet sorghum/Reed Canary grass 9.74 50.89 79.97 -- -- -- 

 Sorghum x sudangrass/Reed canarygrass 9.88 49.98 78.67 -- -- -- 

Note: the four crops with lowest costs are highlighted for emphasis. 

1

 Estimated based on average Iowa equipment use.

2

 ASC = average specified cost (total specified cost divided by yield) includes all costs excluding land costs. ASC does 

include fixed expenses such as interest payments on and depreciation of machinery and on capital investments. 

3

 AC = average cost (total costs divided by yield) included the land cost and is the equivalent of break-even price. 4

 Sweet sorghum and sweet sorghum rye double crop in rotation with corn and soybean. 

Perennial biomass yields averaged over all years and all fertilization levels was highest at Leonard, a 

“marginal” sandy site with wind erosion limitations. Prosper, the second site in the eastern Red River 

Valley area, produced the next highest perennial crop yields. The highest yielding biomass perennial 

crop at both sites was switchgrass (at 9 to 11 Mg ha-1). Intermediate wheatgrass, crested wheatgrass, a 

CRP mixture (consisting of wheatgrasses), and reed canarygrass followed close behind at about 7-9 

dry Mg ha-1. The warm season grasses did not establish well at the other sites to report yields, thus 

the most robust grass performance across all sites was demonstrated by the wheat grasses and CRP 

mixtures – though yields decreased to between 3-5 dry Mg ha-1 except where irrigated. All annual 

crop yields were highest at the irrigated site in the drift prairie region, with the very highest multiyear 

average yield obtained by forage sorghum (16.9 Mg ha-1). Sorghum x sudangrass had very similar 

yields to that of forage sorghum in most years. Both the forage sorghum and sorghum x sudangrass 

displayed yields higher than the perennials in all locations. An annual weed, Kochia, provided the 

most surprising results. While it did not succeed as a volunteering species, in annually seeded plots, 

the yield of Kochia had yields nearly as high as the sorghums on the better sites and performed much 

better than all other species at the poorest site.(18) 

Economic analysis, done on a whole-farm basis, was reported separately in a 1993 paper by Johnson 

et al.(23) Kochia was the first crop to be included on farm plans in all regions, due to its very low 

input cost. However, there are problems in the management of Kochia. For instance, it must be 

harvested prior to frost to prevent large biomass losses and seed drop must be prevented to avoid 

infesting subsequent crops. If Kochia was excluded, then forage sorghum and sorghum x sudangrass 

13
were the most profitable biomass crops. Switchgrass was more profitable than the common small 

grains grown in the Red River Valley area. 

While the performance of switchgrass in the North Dakota screening trials was limited due to its poor 

establishment at most sites, where adequate stands were obtained, it did show potential. Thus, the 

final report recommended that further research should be done on switchgrass in the Northern Great 

Plains. 

 

2.1.8 Oak Ridge National Laboratory – Tennessee 

An “old field” successional vegetation study conducted at ORNL during the same time frame as the 

herbaceous species screening studies and was affected by the same droughty conditions as many of 

the other studies. It provides a comparison not only with the species screening results, but also with 

recent studies in Minnesota on natural vegetation sites. 

The sites studied by Johnston et al.(24) were located on recently abandoned cropland and long 

abandoned pasture. Species diversity was high in both areas with the abandoned pasture having a 

higher percentage of grasses and lespedeza than the abandoned cropland which had significantly more 

composites that are typical weeds in cropland. Levels of productivity (~3.0 to 8.0 Mg ha-1) indicated 

that successional vegetation harvested during the unusually dry conditions of 1986-1988 was 

generally as productive as perennial, monocultural energy crops established in the southeastern U.S. 

during the same years. The successional vegetation was shown to be responsive to liming and 

fertilizers, although to a lesser extent than crops such as sweet sorghum and switchgrass. The 

fertilizer response was not sufficiently strong, however, to compensate for the added cost of the 

fertilizer applications. A preliminary economic assessment suggested that the most cost-effective 

treatment was no fertilization for an overall cost of about $10/Mg ($1990). After 3 years of biomass 

removal, there were no signs of depletion of the pools for the major or minor plant nutrients in the 

treatments that received no lime or fertilizer at either site. However, it was assumed that over the 

long term some additional lime treatment and nutrient replacement would be required. Nitrogen 

removal rates at harvest ranged from ~40 to 60 kg ha-1 depending on harvest timing and yield levels. 

14
3.0 HERBACEOUS CROP PROGRAM CONSIDERATIONS 

3.1 HECP GOALS, ANALYSIS AND DATA SYNTHESIS 

By late 1987 the goals and objectives of the HECP had been refined to clearly state a sensitivity to 

environmental concerns and to working with industry. Cushman et al. clarified in the 1987 annual 

progress report(25) that the overall goal of the HECP was “to work with industry and university 

researchers to provide a technology base that will allow industry to develop commercially viable 

systems for producing herbaceous biomass for fuels and energy feedstocks”. The objectives of the 

HECP were expressed as follows: 

1. Identify the biotic and physical resources available for the production of herbaceous energy 

crops. 

2. Identify and improve the productivity of the species most appropriate for herbaceous energy 

crops 

3. Define cost-effective management techniques for the production of herbaceous energy crops. 

4. Establish the environmental acceptability and economic feasibility of herbaceous energy 

crops. 

Included in the report(25) was an analysis of the problem of erosion on croplands. HECP research 

managers had noted that the best yields for lignocellulosic crops were coming from annual grasses but 

there was substantial concern expressed about the amount of erosion associated with annual crops. 

An analysis was conducted by ORNL staff to examine the erosion potential of cropland and potential 

cropland that might be used for energy crops. Based on data from the 1982 National Resources 

Inventory,(26) it was noted that about 50% of the total cropland base had a low erodibility factor of < 

10 (based on the Universal Soil Loss Equation (USLE)). Almost any crop can be planted on this land 

and water caused erosion will remain less than the 5 tons/acre which was deemed an acceptable level 

by USDA’s Soil Conservation Service (SCS), but much of that land is susceptible to wind erosion. It 

was further found that while only 12% of the cropland base had an erodibility factor of 50+, it 

accounted for over 42.5% of water caused erosion on U.S. cropland with 70% of the losses associated 

with row crops. The USDA/SCS study (26) stated that in the United States (in 1982), annual row crops 

had an averaged annual soil loss rate of 66 Mg ha-1, while hay crops (perennial and annual) average 

only 5.5 Mg ha-1). This analysis indicated an important niche for perennial energy crops and was 

probably very influential in the final selection of a perennial grass as the single “model” species. 

Quoted from Cushman et al.(25) is the following statement: 

“Annual crops, especially energy crops that will leave little residue on the soil, are not 

appropriate for significant acreages of cropland. Perennial energy crops, especially grasses, 

are suitable for almost all cropland and potential cropland. They provide an opportunity to 

produce a crop on erosive land, yet achieve acceptable levels of soil protection.” 

 

The environmental concerns associated with growing annual crops on the types of marginal land 

included in the herbaceous screening trial studies were verified by analysis conducted by several of 

the collaborators. Examples of calculated erosion loss results comparing sorghum with perennial crop 

production systems are shown below (Tables 7 and 8). In Virginia, all species including sorghums 

were planted using no-till establishment on slopes of 4.5 to 10%. The Virginia no-till management 

resulted in much lower levels of estimated erosion than was found for monoculture sorghums planted 

with conventional tillage on sloping sites in Chariton, Iowa. Of great interest, however, was the low 

amount of soil loss estimated when sorghum was intercropped with alfalfa or reed canary grass at the 

Chariton site (Table 8). ORNL had the responsibility of reviewing all of the herbaceous screening 

15
Table 7. Computed soil loss (mean of three sites) of eight no-till-planted species at four locations (three 

soils) in the Piedmont. Table reproduced from Virginia Tech final report.(11) 

Species/Conditions Amelia South 

(Cecil) 

Amelia North 

(Cecil) 

Orange 

(Davidson) 

Lunenburg 

(Appling) 

Average of 

locations 

-------------------------------------Mg ha-1----------------------------------------------------------- 

Sericea lespedeza 4.19 2.33 4.55 1.70 3.19 

Weeping lovegrass 4.88 2.71 5.63 1.97 3.8 

Flatpea 5.07 2.81 5.33 2.06 3.82 

Tall fescue 5.27 2.93 5.16 2.15 3.88 

Crownvetch 5.12 2.84 5.99 2.07 4.00 

Switchgrass 5.87 3.26 6.71 2.39 4.56 

Birdsfoot trefoil 7.61 4.22 7.91 3.09 5.70 

Sorghumsudangrass 13.98 7.75 14.36 5.67 10.44 

Undisturbed land 3.99 2.21 4.02 1.62 2.96 

Soil loss tolerancea 7 7 11 9 8.5 

Soil formation rateb 1 1 1 1 1 

a Soil loss tolerance levels were derived for soils in the U.S. by soil scientists, agronomists, geologists, soil conservationists, 

and federal and state researchers in 1961 and 1962 (see report for references). b

Soil formation rate for environmental sustainability (see report for references). 

Table 8. Estimated soil loss under several crop systems in Iowa. Table reproduced from Iowa State 

University final report. (17)

Cropping system and crop 

Monocrop Double crop Rotation Intercrop 

_______________________________________ ____________ ________________________ ___________ 

Year ALF RCG SWG BBS SS SSH SS/R SSH/R Corn SB SS/R SS ALF RCG 

---------------------------------------------------Mg ha-1--------------------------------------------------------- 

Ames 

1988 3.79 3.79 3.92 3.92 4.89 4.89 3.06 3.06 4.41 3.92 3.06 4.89 3.79 3.79 

1989 0.25 0.04 0.04 0.04 4.89 4.89 3.06 3.06 4.41 4.88 3.06 4.89 0.25 0.04 

1990 0.25 0.04 0.04 0.04 4.89 4.89 3.06 3.06 4.41 4.88 3.06 4.89 0.25 0.04

1991 0.25 0.04 0.04 0.04 4.89 4.89 3.06 3.06 4.41 4.88 3.06 4.89 0.25 0.04

1992 0.25 0.04 0.04 0.04 4.89 4.89 3.06 3.06 4.41 4.88 3.06 4.89 0.25 0.04

Chariton 

1988 1.90 1.94 1.85 1.99 13.89 13.13 22.27 22.27 13.89 14.53 22.02 11.46 2.02 1.96 

1989 0.58 0.39 0.40 0.47 25.65 24.21 22.27 22.27 25.38 26.71 23.27 37.25 1.68 0.41 

1990 0.58 0.31 0.33 0.36 35.62 33.62 22.27 22.27 33.52 35.26 22.27 35.62 1.68 0.41

1991 0.58 0.31 0.33 0.36 35.62 33.62 22.27 22.27 32.05 37.25 22.04 35.26 2.02 0.41

1992 0.58 0.31 0.33 0.36 35.62 33.62 22.27 22.27 31.73 35.62 23.27 37.25 2.02 0.41

Note: ALF = alfalfa, RCG = reed canarygrass, SWG = switchgrass, BBS = big bluestem, SS = sweet sorghum, SSH = 

sorghum x sudangrass, SS/R = sweet sorghum doublecropped with winter rye, SSH/R = sorghum x sudangrass 

doublecropped with winter rye, Corn = corn in a corn-soybean-sorghum three year rotation, and Rotation = average factor 

for plots in the corn-soybean-sorghum rotation. 

16
studies and determining the patterns observed both within and between projects. Table 9 shows the 

crops recommended for further study and/or development by each project. 

Table 9. Species recommended for further development or study by the seven herbaceous screening 

projects 

Institution Recommended crops 

Virginia Tech Switchgrass, weeping lovegrass 

Auburn University Switchgrass, sericea lespedeza, and energy cane 

Purdue University Switchgrass, reed canarygrass, sweet sorghum and sorghum-sudangrass 

Iowa State University Switchgrass and intercropped sorghums 

North Dakota State 

University 

Switchgrass, forage sorghum and sorghum x sudangrass 

Cornell Switchgrass, alfalfa/bromegrass mixture, and timothy/redtop/red clover for the 

well drained soils; 

Reed canary grass for the poorly drained soils. 

Geophyta Forage sorghum, intercropped sorghum x sudangrass, and reed canarygrassa

a

Switchgrass was the 4th best performer in terms of yields but was probably not identified by Geophyta for further work due 

to establishment and weed competition problems. Even so, over 4 years, switchgrass yields continued to increase and nearly 

equaled that of reed canarygrass in the 4th year. During the same period sorghum yields dropped dramatically. 

Note: Switchgrass is listed first in the list of recommended crops, not because it was always considered to be the highest 

potential crop, but to emphasize that 6 of the 7 projects included it in their recommendations. 

While switchgrass was recommended by six of the seven projects, and performed reasonably well in 

the seventh project, it certainly was not always at the top of the recommendation list. Most of the 

projects that also recommended the sorghums tended to see them as being the more likely choice by 

farmers in their region. Turhollow et al.(27) reported in the HECP Annual Progress Report for 1988 

that the major observation across all screening projects was the superiority of both the sorghums and 

switchgrass under drought conditions. Switchgrass produced higher yields than sorghums in 

Virginia but both survived with no-till management in the poor Virginia soils. In Indiana, where late 

growing season rains did come in, sorghum produced as much as 32 Mg ha-1 at one site but, from an 

economic perspective, switchgrass was judged to have higher potential returns. In northern Ohio, the 

sorghums produced higher yields than the perennial grasses but yield declines over time were a 

concern. Sorghums performed well, while warm season perennials performed poorly when 

established in 1988 during drought conditions in North Dakota and Iowa. From an economic 

perspective, both sorghums and switchgrass generally stood out as having higher potential than other 

crop choices. The conclusions of the report(27) indicate the opinion that sorghum may have potential 

for meeting economic requirements in the Midwest, but not the southeast. The only other crop that 

was recommended by more than one project was reed canarygrass. Energy cane and other subtropical grasses produced some very high yields that suggested further work might be merited in the 

south. 

The ORNL graphic (Fig. 2), drawn in 1991, showing both the woody and herbaceous crops 

considered to be high potential included switchgrass, reed canarygrass, sorghum, and tropical grasses 

as the herbaceous crops of choice. The fact that ORNL scientists/research managers in the early 

1990s still considered sorghum to be a high potential energy crop for some areas is evidenced by 

quotes from a 1991 paper presented by Cushman and Turhollow:(5)

17
“We now feel that sorghums will have an important role as energy crops on good sites, 

perhaps in rotation with conventional food crops where year-to-year flexibility in planting 

will be an advantage. However, their use on many lower quality sites will be limited by low 

production and environmental concerns.”

Figure 2. Woody and herbaceous species considered by the Department of Energy's Biofuels Feedstock 

Development Program as having high potential as energy crop feedstocks in 1991. The striped area had 

not completed herbaceous screening studies. 

Given that ORNL was still identifying several species as having high potential for bioenergy in 1991, 

the question arises as to what really forced the choice to focus on a single model species. While 

switchgrass did stand out as an environmentally and economically sound choice for many parts of the 

country, it was not a clear winner in all locations. It is the opinion of this author that a combination 

of the original criteria established by the BFDP, the screening results, and funding limitations 

imposed by the Department of Energy resulted in selection of only a single herbaceous crop species 

for further development. 

3.2 BFDP FUNDING EFFECTS ON MODEL SPECIES SELECTION 

Funding variations in the program at ORNL in the early 1980s and 1990s (Fig. 3) had to affect 

research decisions in some manner. Substantial funding was received by ORNL to launch the new 

Herbaceous Energy Crops research effort in 1984. At the outset of the herbaceous program the 

expectation had been that at least 3 or 4 different types of herbaceous crops would be carried forward 

to further development after the screening phase. Funding remained relatively steady for 3 years but 

dropped substantially due to changes in government priorities before the planned end of the 

herbaceous crop screening phase. The funding drop coincided with the development of plans for 

18
further herbaceous and woody crop development. At this critical juncture, the decision was made 

jointly with DOE to restrict further crop development funding to very few “model” species. By 

focusing on only one herbaceous crop and one woody crop – it was believed there would be a greater 

chance for proving the value of genetics and biotechnology in increasing yields and improving 

economics. 

0.00

1.00

2.00

3.00

4.00

5.00

6.00

DOE funding, $ Million

1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998

Year

Feedstock Program Funding Distribution

PLN & ASSIST

RES OTHER

HEC SUBS

SRWC SUBS

Figure 3. Funding history of the biofuels Feedstock Development Program between 1978 and 1998. 

While the value of focusing was proven over the next several years, it is interesting to note that as 

feedstock funding at ORNL rebounded, crop development funding for both woody and herbaceous 

crop model species remained level while feedstock research expanded into new areas. In the early 

1990s the woody and herbaceous crop development activities at ORNL were combined under the 

Biofuels Feedstock Development Program (BFDP). This joint program was proposed and accepted 

by DOE as a mission-oriented, national program of research and analysis whose goal was to develop 

and demonstrate environmentally acceptable crops and cropping systems for producing large 

quantities of low-cost, high quality biomass feedstocks. Thus, the goals of the BFDP went far beyond 

just developing crops to encompassing systems integration issues, optimizing economics, and 

considering feedstock quality, carbon sequestration issues, and biotechnology potential. Addressing 

these issues required close coordination with managers and researchers in DOE’s Biofuels and 

Biopower Programs – responsible for developing technologies to convert biomass feedstocks to 

energy. Coordination needs also required more investment in outreach and communication and in 

analytical support to DOE. Thus, when funding increases occurred in the mid-1990s – it was 

allocated to new research topics, analysis, and outreach, rather than to expanding the number of 

species being developed. 

19
4. HIGH POTENTIAL FEEDSTOCKS 

4.1 HERBACEOUS CROPS CONSIDERED HIGH POTENTIAL IN 2006

Research conducted specifically to improve switchgrass as a model biomass energy crop during the 

1990s has been very successful in improving its potential as a dedicated biomass energy crop. 

McLaughlin and Kszos published in 2005 an excellent summary of the results gained by the focus on 

switchgrass.(3) The research developments and the continued national level interest in biofuels 

development in the U.S. have been successful in attracting industry interest in further developing 

switchgrass. For instance, the private biotechnology firms, CERES and Mendal Biotechnology are 

both seriously working on the improvement of switchgrass for bioenergy. 

New research conducted over the past 6 years at the University of Illinois has brought a lot of 

attention in the U.S. to a new crop that was identified as having high potential in Europe in the mid 

1990s.(28) Varieties of this crop, Miscanthus, have been grown for many years in the U.S. as a 

landscape plant, but it was never proposed for evaluation in any of the bioenergy crop screening 

studies. Because of the very high yields that have been obtained in Europe and which are now being 

replicated in Illinois with a single sterile hybrid cultivar, Miscanthus x giganteus (or giant 

Miscanthus), a legitimate question is being asked whether it should also be a “model” bioenergy crop 

and how it compares with switchgrass. Side by side studies in Illinois have certainly demonstrated a 

considerably higher yield potential for giant Miscanthus at the location tested.(29) However, there is 

not yet published information discussing the economics and operational issues associated with 

establishing giant Miscanthus on a commercial scale – so a full comparison with switchgrass is 

difficult. 

Sorghum continues to attract a lot of interest. Two presentations at the 2007 World BioCongress 

meetings held in Orlando, Florida, focused on the importance of sorghum as a cellulosic feedstock. 

The Kansas State University - StrathKirn Sorghum Project, currently focusing on bioconversion 

research, sees sorghum as the next most important crop (after corn) for ethanol.(30) Geoffrey Thomas 

of SorBio Energy Systems made a presentation at the conference providing convincing information 

on why sorghum should be receiving more attention.(31) Some of his arguments were the following: 

1. Sorghums could be a starter crop that would fill the gaps in cellulosic feedstock production 

while perennial crops are becoming fully established. 

2. Sorghums can be intercropped with winter cereals for multi-season cellulosic supplies. 

3. Sorghums are adaptive to a wide range of soils conditions with several different varieties 

available to meet site specific requirements. 

4. Low lignin hybrids are available in all key types of sorghum 

5. Sorghum has a well known, fairly simple genome 

6. The sorghum seed industry is well established and there is a large base of experienced 

producers 

7. Sorghums have a large root system, are efficient water and nutrient users, and are simple and 

cost-effective to grow. 

8. Forage sorghum dry land yields in Texas range from 7 to 22 dry Mg ha-1, sweet sorghum 

yields are up to ~17 dry Mg ha-1 and sorghum-sudangrass yields up to 14 dry Mg ha-1 (with 3 

cuttings). 

9. Opportunities are available for further reduction in lignin levels and enhanced sugar yields 

through genetic improvement. 

There are also downsides associated with sorghum harvest, handling, and storage that were not 

20
mentioned by Dr. Thomas but further consideration of sorghum appears to be merited. 

In 2006, a paper published in Science by Tillman et al.(32) brought a lot of attention to “mixed 

grassland biomass” as an environmentally preferable, low-cost alternative resource for bioenergy in 

comparison to all monoculture crops. The paper focused on the energy input/output comparisons 

between growing corn grain for ethanol, soybeans for biodiesel, and grassland crops for biomass 

electric, biomass ethanol or biomass synfuels. The grassland crop based systems were shown to have 

significantly higher net energy balances (NEB) than either the corn grain to ethanol or soybeans to 

biodiesel. Yields of the grassland crops used in the NEB analysis (found in the published backup 

material) averaged 3.6 Mg ha-1 yr-1 for the high diversity grassland plots on degraded soils and 6.0 

Mg ha-1 yr-1 on fertile prairie soils, both in Minnesota. These yields were estimated from multiple 

replicates of very small samples that were harvested in early August of each year. If harvested in late 

September, yields would have likely been higher. An earlier publication (33) had shown the positive 

relationship between increasing diversity and increasing yields with the mean yields of the highest 

diversity plots generally exceeding the highest yielding monoculture plots. However, the switchgrass 

monoculture plots had not established successfully and were not included in the 2001 comparison. 

Some of the BFDP screening studies also noted the possible potential of mixed species plots (some 

were simply weeds, (14,18) one was meadow grasses and legumes, (15) and one was old field 

successional vegetation).(24) Yields were generally in the range of 3 to 8 Mg ha-1. The results in 

North Dakota (18) suggested that a low-input weed crop (Kochia) could be more profitable than 

conventional crops. Also, the old field successional vegetation study suggested the possibility of lowinput systems being profitable.(24) The primary drawback to the low-input “meadow” biomass 

resource is that very large amounts of land would be required to produce the large supplies that will 

be needed for the large ethanol production facility sizes that are considered to be most cost-effective. 

There are many other herbaceous crops that are still of interest to biomass energy crop developers. A 

DOE sponsored workshop held in 2006 (34) provided a group of crop experts from the southeast an 

opportunity to discuss the advantages and issues associated with potential biomass energy crop 

candidates. Crops that made the list included several annuals and perennials. Annuals included 

sorghum-sudangrass, sweet sorghum, johnsongrass, pearl millet, and industrial hemp. Perennials 

included giant reed, energy cane, switchgrass, giant Miscanthus, bermudagrass, napiergrass, 

bahiagrass, tall fescue, and sericea lespedeza. It would be of interest to evaluate all of the proposed 

bioenergy crops against a set of common criteria. Suggested criteria are described below. 

4.2 BIOFUELS FEEDSTOCK SELECTION CRITERIA 

Some important criteria for bioenergy feedstocks were recognized and established early in the 

screening process. Other criteria or valuable characteristics of bioenergy feedstocks were identified 

later as researchers and project developers began to seriously consider the factors necessary for 

putting together cost-effective feedstock supply systems. In order to maintain a historical perspective 

on which criteria lead to the selection of switchgrass as high potential “model” species, the criteria 

have been grouped by the decade in which there importance was more clearly recognized. 

4.2.1 1980s Selection criteria 

In the early 80s, U.S. agricultural exports were at record levels and in 1984 the world became aware 

of famine in sub-Saharan Africa. Thus at the initiation of the trials in 1984 there was much more 

concern about possible conflicts between the production of food and fuel than existed at the end of 

21
the trials.(5) Accordingly, the “capability of energy crops to perform on marginal cropland” was the 

broad objective at the time the herbaceous crop solicitation was issued. Crops which can meet that 

broad objective, however, have several characteristics that can be used as selection criteria. There is 

not a specific criteria related to conversion technology in this list. In the early 1980s, the conversion 

technologies were presumed to have equal chance of being either biochemical or thermochemical so 

no criteria were established that would favor one type system over another. The only conversion 

related exclusions in the herbaceous crop screening solicitation (7) were those that eliminated crops 

whose primary value lie in the production of specific chemical components, resins, latexes, oils, and 

hydrocarbons, or root, grain, or seed crops. Thus, corn grown primarily for production of grain to 

ethanol and beets grown for their sugar were not considered for further research by the Herbaceous 

Energy Crops Program. 

4.2.1.1 Profitability on marginal land 

The 1984 RFP (7) clarified that the objective of the research being initiated was to result in crop 

systems that were driven by “cost-effective production, not maximizing productivity per acre”, 

recognizing that the crops producing the highest yields might not be the most profitable. 

4.2.1.2 Adaptability 

The trait of adaptability is not only associated with a capability to perform on marginal land, but is a 

necessary criteria for meeting the Herbaceous Energy Crop Program goal of identifying crops that 

would have the greatest possible impact on total biomass energy use. This was understood at the time 

to mean the selection of crops that were highly adaptable to production in many U.S. regions. Traits 

that contribute to adaptability include efficient nutrient use, efficient water use, tolerance of wet and 

dry soils, and freeze tolerance. 

4.2.1.4 Minimal soil loss 

Cropping systems that would minimize erosion were high on the list of desirable traits for an energy 

crop production system. The 1982 National Resources Inventory conducted by the USDA’s Soil 

Conservation Service had determined that in the southeast and Midwest/Lake states, erosion was the 

most important restriction on cropland use and wetness was the second most important.(26)

4.2.1.3 High yield potential and yield reliability 

While profitability, rather than high yields, was the ultimate goal, the identification of crops (and 

specific varieties within crops) with the best genetic potential for high yields and yield reliability was 

(and still is) important. High yield results from small field trials have to be evaluated in the context 

of nutrient and water inputs and variability of the crop yield under several years of variable climate 

conditions. Crops with the lowest input requirements and most stable yields are preferred. 

4.2.2 1990s selection criteria 

By 1988, crop surpluses and the high costs of federal agricultural programs were emerging as national 

issues so “food versus fuel” concerns were greatly diminished. Also, late in the 1980s a serious 

attempt was made to begin linking energy crop production selection criteria to specific conversion 

technologies.(35)

22
4.2.2.1 Profitability on productive land 

As research transitioned from screening trials to crop development trials, more research was 

performed on relatively better cropland and economic analysis using the resulting yields suggested 

that some crops had more potential than others to compete with conventional crops on cropland 

currently in production. 

4.2.2.2 Feedstock composition 

The importance of feedstock composition in affecting the success and cost of conversion technologies 

took on greater significance in the late 1980s and early 1990s.(5) A literature review and survey 

published in 1988(36) concluded that all conversion processes are affected by feedstock characteristics. 

 The effects of composition on biochemical and thermochemical conversion were, for the most part, 

predictable – such as the problems caused by high ash contents, the value of high cellulose content for 

ethanol production, and the value of lignin for processes where higher btu levels are important. In 

about 1990, high nitrogen content was found by the Solar Energy Research Institution (now the 

National Renewable Energy Laboratory) to create problems for the simultaneous scarification and 

fermentation (SSF) approach to making ethanol. High nitrogen contributes to undesirable nitrogen 

compounds in the gases produced by thermochemical processes. ORNL funded composition studies 

showed that legumes had protein concentrations 2 to 4 times that of grass crops. Thus, the cost 

reductions that might be gained by the reduced fertilizer requirements of leguminous crops had to be 

weighed against the possible increased costs involved in producing clean fuels.(5) This information 

led to basically dropping legumes from serious consideration by the ORNL/BFDP team. 

4.2.2.3 Reliable stand establishment 

The screening studies had shown the difficulty of establishing switchgrass during times of rainfall 

deficit. Several of the switchgrass crop development projects, focused on identifying causes for the 

problems and succeeded in developing more reliable methods. Reliability in stand establishment is a 

function both of crop characteristics and experience of the crop producer. 

4.2.2.4 Reliable low-cost propagation 

The ability to easily replicate the desired genetic traits using low-cost propagation techniques is 

important to the ability to reliably produce crops with the desired yield and composition traits. It is 

also important for facilitating rapid scale-up of the energy crop. 

4.2.2.5 Soil carbon sequestration 

The potential for herbaceous crops to affect soil carbon sequestration (either positively or negatively) 

also began to be a large issue in the early 1990s. More attention was given to looking at root systems 

and to collecting soil carbon data 

4.2.3 2000s selection criteria 

By the early 2000s, the Biofuels Feedstock Program had already begun scaling up cultural methods 

developed in small research trials to larger scale/pre-commercial trials. Thus, the research community 

became more aware of crop scale-up and environmental issues, and the opportunity was created for 

testing a variety of harvesting, handling, storage, and transportation systems as well as collection of 

data on environmental effects. 

23
4.2.3.1 Rapid scale-up potential 

As the idea of using perennial crop based bioenergy has moved from a concept to a recognized 

component of national energy plans, concerns have increased regarding the time it will take to 

produce sufficient seeds, rhizomes, cuttings, or seedlings to actually get a single large project 

established, much less, millions of acres of these new crops. 

4.2.3.2 Chemical inputs minimal 

With greater interest in bioenergy crops more questions are being asked about the possible impacts of 

the crops on the environment. Crops that can perform well with minimal chemical inputs clearly will 

have more support from environmental groups. 

4.2.3.3 Low pest and disease risk 

Crop that have few pest and disease problems will have greater potential for yield stability, higher 

yield potential, and consequently lower costs of production. This is often one of the attractive 

features of exotic species assuming that they do not have invasive characteristics. 

4.2.3.4 Invasive potential is low 

Increasing attention is being paid to the invasive characteristics of potential energy crops with several 

states excluding crops from consideration that have a high potential for becoming an invasive weed. 

Sometimes, exotic and invasive species are lumped together as though they are the same. In many 

cases, this is true, but not in all cases. Any potential exotic species should be evaluated to determine 

whether it has invasive characteristics before being widely planted in the U.S. and should be rejected 

if that potential exists. However, serious consideration should also be given to the potential yield 

advantages of exotics that are sterile, for example giant Miscanthus. 

4.2.3.5 Sterility 

Sterility is desirable, possibly even a requirement, for exotic species. Some investigators have also 

expressed a concern about the genetic contamination of wild populations of switchgrass from 

widespread planting of improved varieties.(37, 38) 

4.2.3.6 Operational requirements 

There are a number of criteria associated with harvest, handling, and storage that can potentially be 

used in evaluating different species. Some identified in the table below include multiple harvest 

options, broad harvest window, and minimal storage needed. These are not as “fixed” as are basic 

plant characteristics but some crop types facilitate more options than other types and consequently the 

possibility of greater supply reliability at lower cost.(39) 

4.2.3.7 Net energy at feedstock harvest and at point of delivery 

A major point of controversy in recent years has been the amount of energy available in the final 

product versus the energy required to grow, harvest, transport, and convert the crop to its end use. 

Net energy available both in the harvested feedstock and in the delivered feedstock could be used to 

evaluate the relative desirability of different feedstock supply systems. 

24
4.2.3.8 Alternate uses 

Any energy crop will be more attractive to farmers if it has the potential of feeding into several 

possible markets. This will reduce the risk to the farmer in case a specific energy facility fails. 

25
5. CHARACTERISTICS OF THE SWITCHGRASS “MODEL” 

The success that has been achieved in bringing attention to the potential of switchgrass as a feedstock 

for cellulosic ethanol has lead some to equate the term “model species” to mean “best species”. 

When other crops have been found to produce higher yields in a given location, the first response is 

often to question the “model species” status given to switchgrass and to begin marketing the new crop 

as a “better” alternative. A more useful response would be to consider switchgrass as a “prototype” 

species that has been deemed capable of meeting many (though not necessarily all) of the criteria 

desired of a bioenergy crop. 

Switchgrass is a good “prototype” for grass crop genetic improvement research due to its large 

genetic variability and the fact that recent research has elucidated much about the reproductive 

characteristics of the species.(40, 41, 42) Switchgrass is a good prototype for harvest, handling, storage, 

and transport research because it can be grown under a wide rage of climate conditions and is 

amenable to being handled and stored both as a wet or dry feedstock.(39) By focusing the energies of 

many different researchers on a selected prototype energy species, and facilitating the rapid exchange 

of information, it is possible to more quickly and fully develop an understanding of the issues 

involved in developing cost-effective, fully integrated crop supply systems for multiple regions of the 

U.S. 

Table 10 attempts to (1) describe the current characteristics deemed desirable for bioenergy systems 

(and why they are desirable), (2) describe how well the switchgrass species and the assumed cropping 

systems meet those desired characteristics, and (3) provide references for further information. 

Table 10. Feedstock criteria, criteria relevance categories, and ranking (high, medium and low) of the 

capability of switchgrass to meet those criteria for cellulosic ethanol production systems. 

Criteria Relevance 

categories 

Rank Notes and References 

Cost- effective 

production 

Producer profitability H Screening trials found switchgrass to be more 

profitable than alternative conventional crops and 

most grasses on marginal cropland in several parts of 

the U.S. (13, 21, 23) Later analysis has demonstrated 

that profitability depends greatly not only on 

switchgrass technology (inputs, yields, storage, 

transport) but also on farm, environmental and 

energy policies and energy costs, all of which can 

affect land prices and fertilizer and transport costs. 

Broad adaptability Producer 

profitability, Supply 

reliability 

H The wide adaptability range of switchgrass was 

demonstrated by the screening trials described in this 

paper and by summary papers.(3,4) pH ranges from 

4.9 to 7.6 are tolerated.(41) 

Tolerant of wet 

and dry soils 

Producer 

profitability, Supply 

reliability 

(subcomponent of 

broad adaptability) 

M Lowland varieties are naturally found in floodplains 

and upland varieties are found in more well drained 

areas.(43) Screening studies found survival and 

growth in both wet and dry areas.(12, 13, 14, 15, 16, 17, 18)

Freeze tolerant Producer 

profitability, Supply 

reliability 

(subcomponent of 

broad adaptability) 

H Switchgrass has a range well into Canada and into 

Mexico, thus some varieties are more freeze tolerant 

than others.(43) 

26
Efficient nutrient 

use 

Producer 

profitability, 

Environmental 

benefit (needs little 

fertilizer) 

M Fertilizer inputs in the range of 40 to 120 kg N ha-1

per year appear to be the most cost-effective levels 

depending on region of the country and rainfall 

levels.(3, 43, 44, 45, 46, 47, 48) Nutrient loss is greater with 

2 or more cuts per year; best nutrient use efficiency 

is 1 cut per year after senescence.(49, 50)

Efficient water use Producer 

profitability, 

Environmental 

benefit (needs little 

or no irrigation) 

H The case for low water requirement derives primarily 

from the observation that switchgrass remains green 

when other forages turn brown from drought stress. 

Roots are deeper than many grasses. Recent studies 

on transpiration show differences among varieties.(11, 

51, 48) Precipitation levels may be critical to 

successful establishment(3) but yields are not strongly 

affected by precipitation after fully established.(3)

High yield 

potential 

Producer 

profitability, 

Environmental 

benefit (efficient land 

use) 

H-M High yields in the 20 to 30 dry Mg ha-1 range have 

been demonstrated in a few locations, average yields 

following switchgrass selection and development 

tend to be in the range of 10-20 dry Mg ha-1.

(3) 

Breeding studies have indicated a potential to 

improve yields at a rate of 5% or greater per breeding 

cycle.(40)

Alternate uses Producer profitability H A farmer’s co-op in Iowa is developing several 

markets for switchgrass including forages, mulch for 

landscaping, fiberboard and paper, plastics filler, 

stove pellets, fireplace logs, and animal bedding.(60)

Yield reliability Supply reliability H Yield reliability in many soil and climate conditions 

is higher than most annuals and better than many 

perennials based on screening trial results(12, 13, 14, 15, 

16, 17, 18)

Pests and disease 

problems are 

minimal 

Supply reliability, 

Producer 

profitability, 

Environmental 

benefit (low 

chemical use) 

H Pest and disease incidence has been very low thus far 

but some pests and diseases have been identified.(57)

Research in Virginia has shown an advantage to 

using a granular systemic insecticide in rows at time 

of planting reducing need for any further insecticide 

use.(53)

Easily/reliable 

propagation 

Supply reliability, 

Producer profitability 

M Seed production is easy but controlled crossing is 

required. High demand for improved varieties is 

already increasing seed costs. Micro propagation of 

genotypes is possible but costly.(56)

Quick/reliable 

stand 

establishment 

Supply reliability, 

Producer profitability 

M to 

L 

Many of the screening trials reported very slow 

establishment rates (3~4 years) while some later 

studies achieved full yield by the 2nd year. Seeding 

failures may occur if seed dormancy is not broken(47, 

48, 53, 54), or if rainfall is not sufficiently frequent.(55) 

Soil carbon 

sequestration rate 

potential is high 

Environmental 

benefit (soil 

improvement, low 

GHG emissions) 

H The deep rooting system of switchgrass allows crop 

to initially sequester carbon at a high rate (1 to 1.6 

Mg C ha-1

) if production site is carbon depleted.(3, 12, 

58, 59)

Soil loss is 

minimal 

Environmental 

benefit (sustainable 

productivity) 

H Most perennials result in lower soil loss than annual 

crops even when planted into conventionally tilled 

soils, but no till establishment results in the least soil 

loss.(12,17)

27
Chemical inputs 

minimal 

Environmental 

benefit (low GHG 

emissions), Producer 

profitability 

M Herbicides are generally required in first year for 

successful establishment, but rarely thereafter; 

mowing above the new seedlings is sometimes 

sufficient; there has been little need for pesticides.(46, 

47, 53)

Chemical inputs 

minimal 

Addresses an 

important 

environmental 

criteria 

H Herbicides are generally required in first year for 

successful establishment, but rarely thereafter; 

mowing above the new seedlings is sometimes 

sufficient; there has been little need for 

insecticides.(46, 47, 53)

Energy input to 

energy crop 

production is low 

Environmental 

benefit (low GHG 

emissions), Producer 

profitability 

H Energy input requirements are between 3 and 4% of 

the HHV of the pre-harvest production at yields 

ranging from 10 to 30 dry Mg ha-1 and optimized 

fertilization levels.(39) 

Energy input of 

delivered 

feedstock is low 

Environmental 

benefit (low GHG 

emissions), Producer 

profitability 

H Total energy input requirements for crop production, 

harvest and storage, and transport with both current 

and mature technologies are estimated to be 8.5% or 

below at current yields (10 Mg ha-1), reducing to 

6.5% at 30 Mg ha-1 with mature technology.(39) 

Invasive potential 

is low 

Environmental 

benefit (low risk) 

H Switchgrass is a native species that is persistent once 

established, but not overly aggressive in spreading to 

new areas.(43) 

Sterility is natural 

or can be created 

Environmental 

benefit (low risk) 

M-L Switchgrass is an out crossing species, thus large 

populations of naturally selected “improved” 

varieties planted near remnant native populations, 

might result in changing some traits in the native 

populations; this area needs more research to 

determine risk levels, distance of effects, and 

potential for creating sterile varieties. 

Rapid commercial 

scale-up possible 

Supply logistics 

(enabler of near-term 

commercial success) 

M Scaling up of stands of select varieties to propagate 

enough seed for several large projects simultaneously 

would be a problem, probably taking 3-5 years at a 

minimum. However, farmers are interested if 

markets emerge.(60)

Multiple harvest 

options 

Supply logistics 

(allows greater 

adaptability of the 

production system) 

H The thin stemmed switchgrass at current yield levels 

is amenable to conventional mowing and 

conditioning, and can be field chopped and ensiled, 

or swathed and baled in either round bales, small or 

large square bales or “loafs” for dry storage or 

further handling (e.g. pelletizing). Higher yield 

levels will likely require modifications to equipment 

and/or development of more innovative designs.(39)

Harvest window is 

broad 

Supply logistics 

(increases probability 

that majority of crop 

can be harvested) 

M While switchgrass can theoretically be harvested 2 or 

more times during the growing season, in fall and 

even in the following spring – the most sustainable 

system for most regions is one harvest per year in 

fall after senescence. Spring harvests risk a 30 to 

40% yield reduction compared to fall harvest.(58, 61) 

Storage time is 

minimal 

Supply logistics 

(reduces cost, 

minimizes loss, 

reduces changes in 

composition) 

L The downside of one harvest per year is that the 

biomass must be stored for longer periods. 

Development of storage methods that minimize 

losses are a major research effort.(39)

Composition Conversion M Optimal composition for ethanol made with the SSF 

28
(must be specified 

based on planned 

conversion 

process) 

efficiency (final 

product cost) 

process includes high cellulose, low ash, low 

nitrogen and just enough lignin to reduce facility 

power costs. Other biofuel processes may prefer 

more nitrogen (proteins) or more lignin to produce a 

greater variety of co-products. Switchgrass has 

higher cellulose levels and lower ash levels 

compared to many other herbaceous crops 

screened(13,18), but higher ash and nitrogen levels than 

fast growing trees. 

29
30

6. CONCLUSION 

The screening trials funded by the U.S. Department of Energy in the late 1980s to early 1990s 

assessed a wide range of about 34 species with trials being conducted on a wide range of soil types in 

31 different sites spread over seven states in crop producing regions of the U.S. Several species were 

identified as having merit for further development. Six of the seven institutions included switchgrass 

among the species recommended as having high potential in their region and/or deserving of further 

study. Most projects had some to serious problems with switchgrass establishment during drought 

years, but later crop development research identified methods to improve establishment success under 

most conditions. The two southeast projects, in Virginia and Alabama, had the most success with 

switchgrass and produced some of the most persuasive information showing the merits of switchgrass 

– especially the potential for high yields, its deep rooting characteristics, and its potential value in 

carbon sequestration. All of the Midwest projects (in Indiana, Iowa, and North Dakota) came to the 

conclusion that switchgrass merited further consideration primarily after conducting economic 

analysis, since visual results of crop yields most often led toward favoring sorghum systems. In some 

cases, additional characteristics such as more favorable conversion characteristics or lower erosion 

potential increased the interest in switchgrass. Economic and environmental assessments by Oak 

Ridge National Laboratory’s Biofuels Feedstock Development Program staff together with the 

screening project results, and funding limitations lead to making the decision to further develop only 

switchgrass as a “model” or “prototype” species in 1991. 

Selection of switchgrass as a model species in 1991 lead to a switchgrass specific solicitation and 

then to 10 years of switchgrass development at ten institutions under the management of Sandy 

McLaughlin and others at ORNL.(3) More recently switchgrass has been the focus of investigations at 

several additional universities and private institutions. New varieties have been developed and 

released, management techniques have been improved, and much more is now known about how 

switchgrass can be harvested, handled, stored and converted to ethanol or used to produce power. 

Now, in 2007, it is very apparent that while switchgrass may not be a perfect energy crop (and there 

may not be a perfect crop), it has many valuable characteristics that will result in its continuing to be 

not only a “model or prototype” for crop development, but also one of the more sustainable 

feedstocks for the production of renewable alternative fuels in the U.S. 

There are many herbaceous crops that are still of interest to biomass energy crop developers. A DOE 

sponsored workshop held in 2006(34) provided a group of crop experts from the southeast an 

opportunity to discuss the advantages and issues associated with potential biomass energy crop 

candidates. Crops that made the list included several annuals and perennials. Annuals included 

sorghum-sudan grass, sweet sorghum, johnsongrass, pearl millet, and industrial hemp. Perennials 

included giant reed, energy cane, switchgrass, giant Miscanthus, bermudagrass, napiergrass, 

bahiagrass, tall fescue, and sericea lespedeza. Regional and local considerations may well favor use 

of an herbaceous energy crop other than switchgrass. It is important, however, that any crop used for 

bioenergy be capable of being produced in a way that is not only economically sustainable but that 

also meets high standards of environmental sustainability. 
31

7. REFERENCES 

 1. L.L. Wright, J.H. Cushman, A.R. Ehrenshaft, S.B. McLaughlin, S.A. Martin, W.A. McNabb, J.W. 

Ranney, G.A. Tuskan, A.F. Turhollow, Biofuels Feedstock Development Program Annual Progress 

Report for 1992. ORNL-6781. Oak Ridge National Laboratory, Oak Ridge, TN 37831,1993. 

 2. S.E. Sladen, D.I. Bransby, and G.E. Aiken, Biomass, Yields, Composition, and Production Costs for 

Eight Switchgrass Varieties in Alabama, Biomass and Bioenergy Vol 1(2): 119-122, 1991.

 3. S.B. McLaughlin, and L.A. Kszos. Development of switchgrass (Panicum virgatum) as a bioenergy 

feedstock in the United States. Biomass and Bioenergy 28 (2005):515-535, 2005. 

 4. S.B. McLaughlin, New Switchgrass Biofuels Research Program for the Southeast, pp.111-115, In: 

Proceedings of the Annual Automotive Technology Development Contractors’ Coordination 

Meeting. SAE International, Warrendale Pennsylvania, 1992. 

 5. J. H. Cushman and A.F. Turhollow, “Selecting Herbaceou Energy Crops for the Southeast and 

Midwest/Lake States” pp. 465-480 In: Energy from Biomass and Wastes XIV, D.L. Klass (ed), 

Institute of Gas Technology, Chicago, Illinois, 1991. 

 6. SERI. The Production of Herbaceous Feedstocks for Renewable Energy. SERI/SP-273-2302, 

DE85012136 Solar Energy Research Institute, Golden, Colorado 80401-3393, 1986. 

 7. Oak Ridge National Laboratory (ORNL). Request for Proposal No. 19-6233 Entitled “Selection of 

Herbaceous Species for Energy Crops”. Released by Oak Ridge National Laboratory’s Bioenergy 

Feedstock Development program approximately March 1984 with proposals due July 17, 1984. 

 8. OTA. Energy from biological processes. Congress of the United States Office of Technology 

Assessment. U.S. Government printing Office 0-65-498. Washington, D.C., 1980. 

 9. J.B. Berger, and J.H. Cushman, Herbaceous Energy Crops – Planning for a renewed Commitment, 

Environmental Sciences Division Publication No. 2385. Oak Ridge National Laboratory Biomass/ 

Feedstock Development Program, Oak Ridge, TN, 1984. 

10. J.H. Cushman, A.F. Turhollow, and J.W. Johnston. Herbaceous Energy Crops Program: Annual 

Progress Report for FY 1985. ORNL – 6263. Oak Ridge National Laboratory, Oak Ridge, TN, 

19896. 

11. D.J. Parrish, D.D. Wolf, W.L. Daniels, D.H. Vaughan, and J.S. Cundiff. Perennial Species for 

Optimum Production of Herbaceous Biomass in the Piedmont, Final Report 1985-1989. 

ORNL/Sub/85-27413/5, submitted to the Biomass Feedstock Development Program, Oak Ridge 

National Laboratory, Oak Ridge, Tennessee, 1990. 

12. D.J. Parrish, D.D. Wolf, and W.L. Daniels. Perennial Species for Optimum Production of 

Herbaceous Biomass in the Piedmont (Management Study, 1987 – 1991): Final Report. 

ORNL/Sub/85-27413/7, submitted to the Biomass Feedstock Development Program, Oak Ridge 

National Laboratory, Oak Ridge, Tennessee, 1993. 

13. D.I. Bransby, S.E. Sladden, and D.D. Kee, Selection and Improvement of Herbaceous Energy Crops 

for the Southeastern USA, Final Report in a Field and Laboratory Research Program for the period 

March 15, 1985 to March 19, 1990, ORNL/Sub//85-27409/5, Oak Ridge National Laboratory 

Biomass/ Feedstock Development Program, Oak Ridge, TN, 1990. 

14. N. Wright, Screening of Herbaceous Species for Energy Crop Production: Final Report 1985-1990, 

ORNL/Sub/85-27411/5, 1990. 

15. R.A. Pfeifer, G.W. Fick, D.J. Lathwell, and C. Maybee. Screening and Selection of Herbaceous 

Species for Biomass Production in the Midwest/Lake States: Final Report 1985-1989.

ORNL/Sub/85-27410/5, submitted to the Biomass Feedstock Development Program, Oak Ridge 

National Laboratory, Oak Ridge, Tennessee, 1990. 

16. J.H. Cherney, K.D. Johnson, J.J. Volenec, E.J. Kladivko, and D.K. Greene. 1990. Evaluation of 

Potential Herbaceous Biomass Crops on Marginal Crop Land (1) Agronomic Potential. 

ORNL/Sub/85-27412/5&P1, submitted to the Biomass Feedstock Development Program, Oak Ridge 

National Laboratory, Oak Ridge, Tennessee, 1990. 

17. I.C. Anderson, D.R. Buxton, and J.A. Hallam,, Selection of Herbaceous Energy Crops for the 

Western Corn Belt. Final Report Part I: Agronomic Aspects. ORNL/Sub/88-SC264/P1, Oak Ridge 

National Laboratory Biomass/ Feedstock Development Program, Oak Ridge, Tennessee, 1994. 

Available at http://bioenergy.ornl.gov/main.aspx (use search function). 
32

18. D.W. Meyer, W.E. Norby, D.O. Drickson, and R.G. Johnson. Evaluation of Herbaceous Biomass 

Crops in the Northern Great Plains. ORNL/Sub/88-SB844/2. Oak Ridge National Laboratory. Oak 

Ridge, TN 37880, 1994. Available at http://bioenergy.ornl.gov/main.aspx (use search function). 

19. G.W. Fick, R.A. Pfeifer, and D.J. Lathwell. Production Patterns of Perennial Herbaceous Biomass 

Crops in the Great Lakes Region. Energy Sources 16:333-348, 1994. 

20. C.L. Dobbins, P. Preckel, A. Mdafri, J. Lowenberg-DeBoer, and D. Stucky. Evaluation of Potential 

Herbaceous Biomass Crops on Marginal Crop Lands: (2) Economic Potential Final Report 1985-

1989. ORNL/Sub/85-27412/5&P2. Oak Ridge National Laboratory, Oak Ridge, TN. 37880, 1990. 

21. I.C. Anderson, D.R. Buxton, and J.A. Hallam, Selection of Herbaceous Energy Crops for the 

Western Corn Belt. Final Report Part II: Economic Potentials, ORNL/Sub/88-SC264/P2, Oak Ridge 

National Laboratory Biomass/ Feedstock Development Program, Oak Ridge, TN, 1994. 

22. D.W. Meyer, D.E. Lippert, D.O. Erickson, and R.G. Johnson, Evaluation of Herbaceous Biomass 

Crops in the Northern Great Plains: 1990 Annual Report, ORNL/Sub/19X-SB844C/3. Oak Ridge 

National Laboratory, Oak Ridge TN37880, 1991. 

23. R.G. Johnson, R.S. Sell, and D.W. Meyer. Economic Evaluation of Herbaceous Biomass Crops in 

the Northern Great Plains-Economic Analysis. Report on Subcontract No. 19x-SB844c. Oak Ridge 

National Laboratory, Oak Ridge, TN. 37880, 1993b.

24. J.W. Johnston, Jr. Evaluation of the Potential for Using Old-Field Vegetation as an Energy 

Feedstock: Biomass Yield, Chemical Composition, Environmental Concerns, and Economics. 

ORNL/TM-11615 Oak Ridge National Laboratory, Oak Ridge, TN 37880, 1990. Available at 

http://www.osti.gov/bridge/servlets/purl/6467844-Qfkbnw

25. J.H. Cushman, A.F. Turhollow, and J.W. Johnston. Herbaceous Energy Crops Program Annual 

Progress Report for FY 1987. ORNL-6514. Oak Ridge National Laboratory, Oak Ridge, TN, 1989. 

26. U.S. Department of Agriculture Soil Conservation Service, Basic Statistics 1982 National Resources 

Inventory, Statistical Bulletin No. 756, Iowa State University Statistical laboratory. September 1987. 

27. A.F. Turhollow, J.H. Cushman, and J.W. Johnston. Herbaceous Energy Crops Program: Annual 

Progress Report for FY 1988. ORNL-6639. Oak Ridge National Laboratory, Oak Ridge, TN, 1990. 

28. E. Heaton, T. Voight, and S.P. Long. A quantitative review comparing the yields of two candidate C4 

perennial biomass crops in relation to nitrogen, temperature, and water. Biomass and Bioenergy 27 

(2004): 21-30, 2004a. 

29. E.A. Heaton, J. Clifton-Brown, T.B. Voight, M.B. Jones, and S.P. Long. Miscanthus for Renewable 

Energy Generation: European Union Experience and Projections for Illinois. Mitigation and 

Adaptation Strategies for Global Change 9: 433-451, 2004b. 

30. J. McLaren, Sorghum BioConversion Research: Sorghum – The Next Most Important Crop for 

Ethanol, Presented at the 2007 World Congress on Industrial Biotechnology and Bioprocessing, 

Orlando, Florida, Mar 21-24, 2007. more information on project can be found at 

http://www.strathkirn.com/Presentations/ASTAsorghum02.htm

31. G. Thomas, The Role of the Genus Sorghum as a Cellulosic Bio-feedstock, Presented at the 2007 

World Congress on Industrial Biotechnology and Bioprocessing, Orlando, Florida, Mar 21-24, 2007. 

32. D. Tillman, J. Hill, and C. Lehman. Carbon-Negative Biofuels from Low-Input High-Diversity 

Grassland Biomass. Science 8 December 2006:314:1598-1600. DOI: 10.1126/science.1133306. 

33. David Tillman, Peter B. Reich, Johannes Knops, David Wedin, Troy Mielke, and Clarence Lehman. 

Diversity and Productivity in a Long-Term Grassland Experiment. Science 26 October 2001: Vol. 

294. no. 5543, pp. 843 – 845, DOI: 10.1126/science.1060391. 

34. Department of Energy, Office of Biomass Program. 30 x 30 Workshop. 2006. Notes available at 

www.30x30workshop.govtools.us 

35. Turhollow, A.F., J.W. Johnston, and J.H. Cushman. Linking Energy Crop Production to Conversion: 

The Case of Herbaceous Lignocellulosic Crops to Ethanol. RERIC International Energy Journal: 

Vol. 10, No. 2 (41-49), December 1988. 

36. R.S. Butner, D.C. Elliot, L.J. Sealock, Jr., and J.W. Pyne, Effect of Biomass Feedstock Chemical and 

Physical Properties on Energy Conversion Processes, PNL6575 Vols. 1 and 2. Pacific Northwest 

Laboratory, Richland, WA 1988. 

37. K.P. Vogel and G.J. Hans-Joachim, Genetic Modification of Herbaceous Plants for Feed 

and Fuel, Critical Reviews in Plant Sciences 20(1): 15-49, 2001. 
33

38. A.A. Snow, Transgenic crops-Why Gene Flow Matters, Nature Biotechnology 20:542, June 

2002. 

39. S. Sokhansanj, S. Mani, A.Turhollow, A. Kumar, D. Bransby, L. Lynd, M. Laser, Large Scale 

Production, Harvest and Transport of a Switchgrass (Panicum virgatum L.) Current Technology and 

Visioning a Mature Technology. Manuscript submitted for publication to Biomass and Bioenergy in 

June 2007. 

40. C. M. Taliaferro, K.P. Vogel, J.H. Bouton, S.B. McLaughlin, and G.A. Tuskan, Reproductive 

Characteristics and Breeding Improvement Potential of Switchgrass. In: “Proceedings of the 4th

biomass Conference of the Americas – Biomass, A Growth Opportunity in Green Energy and ValueAdded Products” (R. Overend and E. Chornet, Eds.) pp. 147-153. Elsivier Sciences, Oxford, United 

Kingdom, 1999. 

41. C.M. Taliaferro, Breeding and Selection of New Switchgrass Varieties for Increased Biomass 

Production. ORNL/SUB-02-19XSY162C/01. Oak Ridge National Laboratory, Oak Ridge, 

Tennessee. 2002. Available at: http://bioenergy.ornl.gov/main.aspx (search by author).

42. K.P. Vogel, Genetic Improvement of Switchgrass and Other Herbaceous Plants for Use as Biomass 

Fuel Feedstock: Final Report, ORNL/SUB/90-90OR21954/1, Oak Ridge National Laboratory, Oak 

Ridge, TN. Available at: http://bioenergy.ornl.gov/main.aspx (search by author).

43. L.E. Moser and K.P. Vogel, Switchgrass, Big Bluestem, and Indiangrass, pp. 409-420 In: Forages 

Volume 1: An Introduction to Grassland Agriculture (eds R.F. Barnes, D.A. Miller, C.J. Nelson), 

Iowa State University Press, Ames Iowa 50014, 1995. 

44. K.P. Vogel, J.J. Brejda, D.T. Walters, D. R. Buxton, Switchgrass Biomass Production in the Midwest 

USA: Harvest and Nitrogen Management. Agronomy Journal 2002; 94:413-420. 

45. A. Teel, S. Barnhard, G. Miller, Management Guide for the Production of Switchgrass for biomass 

Fuel Production in Southern Iowa, PM 1710, Iowa State University Extension, Revised May 2003. 

Available at: http://www.extension.iastate.edu/Publications/PM1710.pdf. 

46. J. Lawrence, J. Cherney, P. Barney, Q. Ketterings, Establishment and Management of Switchgrass, 

Fact Sheet 20, Agronomy Fact Sheets, Cornell University Cooperative Extension, 2006. Available at: 

http://nmsp.css.cornell.edu/publications/factsheets/factsheet20.pdf

47. L. Rinehart, Switchgrass as a Bioenergy Crop, A Web Publication of ATTRA – National 

Sustainability Agriculture Information Service (www.attra.ncat.org), 2006. Available at 

www.attra.ncat.org/attra-pub/pdf/switchgrass.pdf. 

48. D.J. Parrish, D.D. Wolf, J.H. Fike, W.L. Daniels, Switchgrass as a Biofuels Crop for the 

Upper Southeast: Variety Trials and Cultural Improvements – Final Report for 1997 to 

2001, ORNL/SUB-03-19XSY163/01, Oak Ridge National Laboratory, Oak Ridge, 

Tennessee, 2003. Available at: http://bioenergy.ornl.gov/main.aspx. 

49. J. H. Reynolds, C.E. Sams, H.A. Fribourg, Photosynthesis and Forage Quality of Tall Fescue and 

Switchgrass, TEN00105 University of Tennessee, Department of Plant Sciences – Recent Findings on 

website. 2000. Available at http://plantsciences.utk.edu/sams_ad421_2000.htm.

50. W.E. Thomason, W.R. Raun, G.V. Johnson, C.M. Taliaferro, K.W. Freeman, K.J. Wynnm, R.W. 

Mullen. Switchgrass Response to Harvest Frequency and Time and Rate of Applied Nitrogen. 

Journal of Plant Nutrition 2004; 27:1199-1226. 

51. G.T. Byrd and P.A. May, II, Physiological Comparisons of Switchgrass Cultivars Differing 

in Transpiration Efficiency, Crop Science 40: 1271-1277, 2000. 

52. D.G. De La Torre Ugarte, M.E. Walsh, H. Shapouri, S.P. Slinsky The Economic Impacts of 

Bioenergy Crop Production on U.S. Agriculture, U.S. Department of Agriculture, Office of Chief 

Economist, Office of Energy Policy and New Uses, Agricultural Economic Report Number 816, 

February 2003. Available at http://www.usda.gov/oce/reports/energy/index.htm. 

 

53. D.D. Wolf and D.A. Fiske, Planting and Managing Switchgrass for Forage, Wildlife, and 

Conservation, Publication 418-013, Virginia Cooperative Extension, 1995. Available at: 

http://www.ext.vt.edu/pubs/forage/418-013/418-013.html. 
34

54. A. Teel, S. Barnhard, Switchgrass Seeding Recommendations for the Production of biomass Fuel in 

Southern Iowa, PM 1773, Iowa State University Extension, Revised May 2003. Available at: 

http://www.extension.iastate.edu/Publications/PM1773.pdf. 

55. W. Ocumpaugh, M. Hussy, J. Read, J. Muir, F. Horns, G. Evers, K. Cassida, B. Venuto, J. 

Grichar, C. Tishchler, Evaluation of Switchgrass Cultivars and Cultural Methods for 

Biomass Production in the South Central U.S.- Consolidated Report 2002, ORNL/SUB-03-

19XSY091C/01, Oak Ridge National Laboratory, Oak Ridge, Tennessee, 2003. Available 

at: http://bioenergy.ornl.gov/main.aspx (search by author). 

56. B.V. Conger, Development of In Vitro Systems for Switchgrass (Panicum virgatum): Final 

Report for 1992 to 2002, ORNL/SUB-02-11XSY161/01, Oak Ridge National Laboratory, 

Oak Ridge, Tennessee, 2002. Available at: http://bioenergy.ornl.gov/main.aspx. 

57. B. Nyoka, P. Jeranyama, V. Owens, A. Boe, M. Moechnig, Management Guide for Biomass 

Feedstock Production from Switchgrass in the Northern Great Plains, SGINC2-07, North Central 

Sun Grant Center, South Dakota State Unive5rsity, Brookings, SD 57007, June 2007. Available at: 

http://agbiopubs.sdstate.edu/articles/SGINC2-07.pdf. 

58. D.J. Parrish, J.H. Fike, The Biology and Agronomy of Switchgrass for Biofuels, Critical Reviews in 

Plant Sciences 2005; 24: 423-459. 

59. S.B. McLaughlin, D.G. De La Torre Ugarle, C.T. Garten, Jr., L.R. Lynd, M.A. Sanderson, V.R. 

Tolbert, D.D. Wolf. High Value Renewable Energy from Prairie Grasses, Environmental Sciences 

and Technology 36:2122-2129, 2002. 

60. P.C. Hipple and M.D. Duffy, Farmers’ motivations for Adoption of Switchgrass, In: Trends in new 

crops and new uses, J. Janick and A. Whipkey (eds), ASHS Press, Alexandria, VA. Also available at: 

http://www.hort.purdue.edu/newcrop/ncnu02/pdf/duffy-252.pdf. 

61. P.R. Adler, M.A. Sanderson, A.A. Boateng, P.J. Weimer, J.G. Hans-Joachim, Biomass Yield and 

Biofuel Quality of Switchgrass Harvested in Fall or Spring. Agronomy Journal 2006; 98:1518-1525. 

 

 

 

 
35

Appendix A. AUBURN UNIVERSITY YIELD RESULTS 

Dry matter yields of herbaceous species from 1985 to 1989 at four locations in Alabama analyzed 

separately for each location in each year (table scanned from Auburn final report (13). 
36
37

Appendix B. GEOPHYTA YIELD RESULTS 

Mean dry matter yields for one harvest per season at three locations in Ohio for four years 

(scanned from Geophyta final report (14). 
38
39

Appendix C. PURDUE UNIVERSITY YIELD RESULTS 

Figure C1. Switchgrass yield response to nitrogen fertilization (0, 50, 150, and 2000 kg N ha-1. 

Means of four replicates and one location in 1988 and 1989 (figure scanned from Cornell final 

report (15). 

Figure C2 Sweet sorghum yield response to nitrogen fertilization (0,50,100, and 150 kg N ha-1

averaged over four replicates, four locations, and two tillage treatments (figure scanned from 

Cornell final report (15). 
40
41

Appendix D. IOWA STATE UNIVERSITY YIELD RESULTS 

Yield results for energy crops tested at Ames, a good cropland site and Chariton, a marginal cropland site (17). 

Ames 

YEAR MONOCROP DOUBLE CROP ROTATION INTERCROP 

FERT 

TRT 

ALF RCG SWG BBS SS SSH SWS/R SSH/R CORN SB SWS SWS/R ALF/ 

SS 

RCG/ 

SS 

kgN/ha ---------------------------------------------------------------Mg/ha/year----------------------------------------------------------------- 

1988 

0 5.97 8.1 6.8 15.1 14.4 9.1 9.6 7.7 

70 6.1 5.2 7.7 5.7 15.3 13.6 11.7 11.9 8.6 

140 6.1 5.5 8.3 6.4 17.5 14.6 12.0 14.0 11.3 

280 5.2 7.9 5.5 16.7 14.7 12.3 16.4 11.9 

1989 

0 3.0 5.0 6.2 16.3 13.1 10.1 9.3 10.5 

70 11.1 5.8 8.0 6.9 16.1 14.7 15.8 15.0 15.1 13.1 19.38 16.9 7.5 

140 12.9 7.9 8.3 6.4 15.3 16.3 19.0 19.1 17.8 16.1 22.25 15.9 9.5 

280 10.0 8.1 8.2 15.0 16.4 21.7 22.3 19.0 

1990 

0 5.8 7.2 10.7 11.4 10.8 11.6 9.1 11.1 

70 10.2 7.2 11.6 10.7 15.3 11.4 15.7 12.8 15.1 12.9 18.22 14.9 8.2 

140 12.1 10.3 10.6 11.4 20.7 15.3 19.6 15.1 16.6 16.8 22.53 15.5 10.4 

280 11.6 13.3 11.9 19.6 16.9 18.2 21.9 18.7 

1991 

0 4.6 4.9 7.3 13.5 14.3 19.9 8.9 7.3 

70 10.1 6.8 11.2 8.3 16.7 16.3 14.2 12.0 10.2 12.5 18.69 15.4 10.9 

140 10.3 7.9 10.3 7.7 16.5 16.7 20.5 14.2 11.5 13.3 19.43 17.1 13.5 

280 11.4 9.5 6.9 16.3 14.1 20.7 19.4 12.0 

1992 

0 2.9 7.2 8.4 8.6 11.5 8.5 

70 9.3 4.5 13.8 11.1 17.7 15.1 7.2 17.0 11.1 7.3 

140 8.2 6.8 15.3 12.4 17.4 15.6 11.7 18.4 11.9 9.5 

280 12.3 15.9 14.3 16.4 16.7 12.2 

Chariton 

1988 

0 17.8 12.8 10.3 10.2 7.7 

70 16.8 14.1 9.9 11.1 8.6 

140 17.9 13.9 9.6 11.4 11.3 

280 19.3 14.0 11.4 12.5 11.9 

1989 

0 3.1 16.1 15.1 11.8 10.9 10.5 

70 6.8 3.1 15.8 14.2 11.8 13.7 15.1 10.4 13.81 2.3 - 

140 7.6 2.9 15.6 13.5 11.9 14.0 17.8 12.1 15.53 2.5 - 

280 3.0 16.4 15.7 12.8 14.2 19.0 

1990 

0 7.1 5.8 7.3 16.4 15.2 12.4 0.95 11.1 

70 9.9 11.3 6.6 29.7 20.7 20.4 14.9 15.0 15.1 13.7 20.95 3.8 - 

140 11.0 11.8 8.3 9.4 22.9 21.8 21.1 19.7 16.6 19.5 26.72 3.9 - 

280 13.1 8.3 9.4 19.1 22.7 26.6 24.1 18.7 

1991 

0 4.8 7.8 5.5 13.5 14.1 11.7 10.6 7.3 

70 7.4 7.9 8.9 5.5 17.7 16.5 18.8 15.8 10.2 17.2 24.41 - - 

140 9.1 9.9 10.7 6.4 16.8 16.4 21.3 18.8 11.5 20.2 25.29 - - 

280 10.5 10.9 5.5 17.2 16.9 23.6 21.5 12.0 

1992 

0 6.3 9.7 5.8 8.7 8.7 8.5 

70 8.9 7.9 12.4 9.2 16.1 12.9 7.2 14.2 

140 6.7 10.9 15.8 10.5 16.7 12.6 11.7 15.9 

280 12.8 17.4 12.8 16.5 17.0 12.2 

Notes: ALF = alfalfa, RCG = reed canarygrass, SWG=switchgrass, BBS=big bluestem. SS=sweet sorghum, SSH=sorghum x sudangrass,

SWS/R=sweet sorghum doublecropped with winter rye, SSH/R=sorghum x sudangrass double cropped with winter rye, CORN=corn total plant 

yield in a corn-soybean-sorghum three year rotation, in the corn-soybean-sorghum rotation, ALF/SS is intercrop of alfalfa with sweet sorghum, 

the sum of 3 harvests. RCG/SS involved the planting of sweet sorghum into a reed canarygrass stand, the sum of 3 harvests. 
42
43

Appendix E. NORTH DAKOTA STATE UNIVERSITY YIELD RESULTS 

Mean biomass yields of several perennials at six North Dakota sites, averaged across years and 

Nitrogen levels, (scanned from North Dakota State University final report (18)). 
44
45

ORNL/TM-2007/109 

INTERNAL DISTRIBUTION 

 1. V.H. Dale 19. S. Sokhansanj 

2-13. M.E. Downing 20. A.F. Turhollow 

 14. R.L. Graham 21. T.O. West 

 15. G.K. Jacobs 22. E.G. Wilkerson 

 16. J.R. Mielenz 23-24. L.L. Wright 

 17. R.D. Perlack 25. ORNL Central Research Library 

 18. M.J. Sale 26. ORNL Laboratory Records - RC 

EXTERNAL DISTRIBUTION 

 27. J. Auyong, Oregon State University, 138 Strand Agriculture, Corvallis, OR 97331 

 28. J.A. Beaudry-Losique, U.S. Department of Energy, EE-2E, 1000 Independence Ave., 

SW, Washington, DC 20585 

 29. K.R. Craig, Department of Energy, Golden Field Office, MS 1501, 1617 Cole Blvd., 

Golden, CO 80401 

 30. J.J. Doolittle, South Dakota State University, Box 2120, SAE 221, Brookings, SD 

57007-2141 

 31. T.R. Dutson, Oregon State University, 126 Strand Agriculture Hall, Corvallis, OR 

97331-2212 

 32. A.M. Goss Eng, U.S. Department of Energy, EE-2E, 1000 Independence Ave., SW, 

Washington, DC 20585 

 33. J.E. Ferrell, U.S. Department of Energy, EE-2E, 1000 Independence Ave., SW, 

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Washington, DC 20585 

 35. J.R. Hess, Idaho National Laboratory, P.O. Box 1625, 2525 Fremont Ave., Idaho Falls, 

ID 83415-2210 

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6021 

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57007 

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