Critical issues

While there are many potential benefits of bioenergy? development and use, there are also potential risks and challenges to sustainability. Further, not all of these potential benefits and risks are shared equally by everyone in society, which is itself a challenge for democratic society. Some of the risks and challenges are well understood, although their solutions may not be as well understood. Other risks and challenges require further research to better understand them. Future policy will be needed to address these issues. Below are brief overviews of critical issues in the current development of bioenergy.

Food vs. Fuel

In 2007-08 global agricultural commodity prices spiked causing millions of people in poor and lesser developed countries to suffer food shortages. Subsequent analyses have identified a complex and interconnected set of factors contributing to the crisis, including most notably, futures trading, increased petroleum prices, agricultural price supports and subsidies in developed nations, low grain reserves, increased demand among a growing human global population, and diversion of food crops for making ethanol. That is to say, although industrial large-scale? agricultural production and world trade have many benefits, fundamentally the 2007-08 was an unfortunate consequence of a complex globalized food and fuel commodity system. A complete analysis of the crisis and potential future similar crises is beyond the scope of this document. However, here it is important to acknowledge that during the 2007-08 crisis much attention was directed toward the use of food crops for production of biofuel? as a driver of increased food prices. This attention emerged through the popularized phrase, “food v. fuel.”

Conventional row crops like corn, sugar cane and soybean can be used for food, feed or as bioenergy feedstocks, include that for biofuel. Use of arable farmland for production of bioenergy does present some risk of impact to food supply on the global scale. However, there is lack of consensus about how best to respond to this dilemma. Responses can be generally characterized as supply-focused or demand-focused. Supply-focused approaches emphasize increases in global agricultural productivity and efficiency, and commercial development of second generation biofuels? utilizing non-food crops, for example; demand-focused approaches emphasize such things as reduced per capita consumption of food and energy in developed countries through increased efficiencies and lifestyle changes. This debate suggests that solutions to competing land uses serving increasingly globalized commodity markets may not be in the form of a “silver bullet” – a single remedy, but rather “silver BBs,” - a multi-tactic approach. To fulfill increased demand for food, feed, fiber, fuel and power in Wisconsin and beyond, it may be necessary to embrace a “food and fuel” mentality.


Dorelien A. 2008. Population’s role in the current food crisis: focus on East Africa. Population Reference Bureau, Washington, D.C. Available at:, verified 09/24/10.

Food and Water Watch. 2009. Casino of hunger: how Wall Street speculators fueled the global food crisis. Washington, D.C. Available at:

Global Food Markets Group. 2010. Agricultural price spikes: causes and policy implications. Department for Environment Food and Rural Affairs, United Kingdom. Available at: Verified 09/24/10

Pfuderer S, G. Davies, and I. Mitchell. 2010. Annex 5: the role of demand for biofuel in the agricultural commodities price spikes of 2007/08. Department for Environment Food and Rural Affairs, United Kingdom. Available at: Verified 09/24/10.

Rosegrant M. W. 2008. Biofuels and grain prices: impacts and policy responses. Testimony for the U.S. Senate Committee on Homeland Security and Governmental Affairs, Washington, D.C., May 7. Available at: Verified 09/24/10.

Surowiecki, J. 2008. The perils of efficiency. The New Yorker. Available at: Verified 03/14/11.

UNCTAD. 2008. Addressing the global food crisis: key trade, investment and commodity policies in ensuring sustainable food security and alleviating poverty. United Nations Conference on Trade and Development, Rome, Italy. Available at: Verified 09/24/10.

Ecosystem Services

A major challenge of energy and natural resource use and management is fulfilling multiple and sometimes conflicting demands for agricultural goods, conservation, and environmental quality for the benefit of all. At the heart of this challenge are issues of private land ownership rights and entitlements, public lands policy, public goods such as clean air and water, and finding a balance among competing viewpoints and interests.

In 2005, the Food and Agriculture Organization of the United Nations popularized and formalized the concept and definitions of ecosystem services?. Ecosystem services are the multitude of benefits humans receive from the resources and processes supplied by natural and managed ecosystems. The Millennium Ecosystem Assessment (2005) organized ecosystem services into four broad categories: provisioning, or the goods and products obtained from ecosystems, including food and fiber - both cultivated and wild; regulating, or the benefits derived from ecosystem’s control of natural processes such as erosion and natural hazards; supporting, or services that are necessary for non-humans and maintenance of all other ecosystem services; and cultural, such as recreational or educational benefits.

As the supporting category implies, ecosystem services are not independent of each other. As a result, attempts to maximize a particular ecosystem service typically lead to reduction of other ecosystem services in what are known as ecosystem service trade-offs? (Rodriguez et al., 2006). These trade-offs are an inherent consequence of human activity that changes the type, magnitude or relative mix of services provided by ecosystems (Rodriguez et al., 2006). To meet the challenge of fulfilling multiple demands for agricultural goods, conservation, and environmental quality for the benefit of all, it will be necessary to weigh the relative trade-offs afforded under various scenarios of biomass? production, bioenergy technologies, and bioenergy consumption. Therefore, ecosystem services and management of potential trade-offs are key issues in policy-making as well as decision-making by individuals and organizations within the biomass supply chain?.

(Millennium Ecosystem Assessment, 2005)


Foley, JA, R DeFries, GP Asner, C Barford, G Bonan, SR Carpenter, FS Chapin, MT Coe, GC Daily, HK Gibbs, JH Helkowski, T Holloway, EA Howard, CJ Kucharik, C Monfreda, JA Patz, IC Prentice, N Ramankutty and PK Snyder. 2005. Global consequences of land use. Science 309:570-574.

Millennium Ecosystem Assessment. 2005. Ecosystems and Human well-being: a framework for assessment. Available at: Verified, Jan. 12, 2011.

Redford KH and WM Adams. 2009. Payment for ecosystem services and the challenges of saving nature. Conservation Biology 23:785-787.

Ribaudo M, C Greene, L Hansen and D Hellerstein. 2010. Ecosystem services from agriculture: steps for expanding markets. Ecological Economics 11:2085-2092.

Robinson K. 2009. Ecosystem services. World Resources Institute, People and Ecosystems. Available at:

Rodrigues, JP, TD Beard Jr., EM Bennett, GS Cumming, SJ Cork, J Agard, AP Dobson & GD Peterson. 2006. Trade-offs across space, time and ecosystem service. Ecology and Society 11: 28-38.

Van Hecken G and J Bastiaensen. 2010. Payments for ecosystem services: justified or not? A political view. Environmental Science and Policy 13:785-792.

Marginal lands

What are marginal lands?

Marginal lands are generally unsuitable for intensive row-crop production due to environmental limitations such as steepness and soil characteristics. Nonetheless, some marginal lands are in row-crop production, which is usually less profitable than prime agricultural land in most years. Some marginal lands are enrolled in conservation programs such as the Conservation Reserve Program (CRP) in an effort to address soil, water, and related natural resource concerns while providing farmers with technical and financial assistance. Some marginal lands have never been cultivated and are the location of intact native ecosystems such as prairies, shrublands and wet meadows.

Marginal lands have been identified as potentially suitable for production of perennial grasses? and grass polycultures for use in bioenergy production. At issue is 1) how much marginal land is potentially available for bioenergy production; 2) what yields can be expected from marginal lands, and how will yields vary from place-to-place and over time; 3) what are the types management practices that will be necessary for ensuring that biomass production on marginal lands is environmentally sustainable; and 4) what will be the impacts to wildlife, farm profitability, and rural economic development.

How much marginal land is available?

Several national studies have estimated the amount of marginal land available in the United States for growing and harvesting biomass for bioenergy. STUDY estimates that there could be 51- 67 million acres of marginal land that could produce as much as 321 million tons of biomass annually. The 2007 U.S. Census of Agriculture identifies approximately 30 million acres of land including idle lands, land currently in cover crops for soil improvements, and fallow rotations. These and similar studies conclude that with careful planning, biomass crops could be suitable for use on these lands.

Preliminary research on availability of marginal lands in Wisconsin puts the estimate at six million acres (M. Ruarke, 2010). Among such areas are lands identified as “open land” - land not currently in agriculture, but capable of producing crops.

In order to avoid degradation of existing ecosystem services and biodiversity, many researchers and resource managers advise against the conversion of native ecosystems to biomass crop production. However, it is thought that many environmental and societal benefits could result from conversion of marginal lands currently in row-crop to perennial biomass cropping systems.

What are the potential benefits of using marginal lands for biomass production?

In addition to biomass yields, it is thought marginal lands could provide environmental benefits such as wildlife habitat, flood protection, and groundwater infiltration when appropriately managed. However, conversion from row crop agriculture to dedicated biomass crop systems, even low intensity systems, may involve tillage during the establishment year, nutrient application annually (at least minimally so), and periodic use of pesticides. Therefore, careful consideration must be given to the site-specific nature of marginal lands and various management options in order to understand potential benefits and risks associated with biomass production.

What are the potential risks of using marginal lands for biomass production?

Use of marginal lands for biomass production has become a contentious issue. Although marginal lands are suggested as ideal locations for growing nonfood crops for bioenergy production, the necessary biomass supply for meeting national renewable energy? goals will likely require perennial plants to be grown in agronomic systems rather than as systems that mimic managed conservation areas for wildlife or other goals. It is not clear whether land use change within marginal lands, particularly intensification of biomass production through use of tillage, synthetic fertilizers and pesticide inputs will result in overall gains in benefits or overall reduction in environmental and ecological benefits. For example, it is generally acknowledged that perennial crops are a potential a benefit for their carbon sequestering capabilities compared to annual crops. However, carbon emissions rather than sequestration can result if previously unplowed lands are tilled for agronomic production of perennial energy crops. Additionally, tillage and use of heavy equipment of marginal lands risks increases in soil erosion and compaction, respectively. These impacts to marginal soils could reduce their already limited productivity over time. Additionally, use of nitrogen fertilizer on marginal lands can lead to nitrogen emissions that contribute to global climate change, and runoff into nearby waterways leading to water quality reduction within entire watersheds.


Adler, PR, MA Sanderson, PJ Weimer and KP Vogel. 2009. Plant species composition and biofuel yields of conservation grasslands?. Ecological Applications 19: 2202-2209.

Dale, VH, KL Kline, J Wiens and J Fargione. 2010. Biofuels: implications for land use and biodiversity. Ecological Society of America, Biofuels and Sustainability Reports. Available at:

DeHaan, LR, S Weisberg, D Tilman and D Fornara. 2009. Agricultural and biofuel implications of a species diversity experiment with native perennial grassland plants. Agriculture, Ecosystems and Environment 1-2:33-38.

Fargione, JE, RJ Plevin and JD Hill. 2010. The ecological impact of biofuels. Annual Review of Ecological and Evolutionary Systems 41:351-377.

Groom, MJ, EM Gray and PA Townsend. 2008. Biofuels and biodiversity: principles for creating better policies for biofuel production. Conservation Biology 22:602-609.

Hill, J. 2007. Environmental costs and benefits of transportation biofuel production from food- and lignocellulose-based energy crops. A review. Agronomy and Sustainable Development 27:1-12.

Kemp, L and JM Sibbing. 2010. Growing a green energy future: a primer and vision for sustainable biomass energy. The National Wildlife Federation, Washington, D.C. Available at:

Paine, LK, TD Peterson, DJ Undersander, KC Rineer, GA Bartelt, SA Temple, DW Sample and RM Klemme. 1996. Some ecological and socio-economic considerations for biomass energy crop production. Biomass and Bioenergy 10:231-242.

Perlack, RD, LL Wright, AF Turhollow, RL Graham, BJ Stokes, and DC Erbach. 2005. Biomass as feedstock for a bioenergy and bioproducts industry: the technical feasibility of a billion-ton annual supply. U.S. Department of Energy, DOE/GO-102005-2135. AVAILABLE AT:

Robertson, GP, VH Dale, OC Doering, SP Hamburg, JM Melillo, MM Wander, WJ Parton, PR Adler, JN Barney, RM Cruse, CS Duke, PM Fearnside, RF Follet, HK Gibbs, J Goldemberg, DJ Mladenoff, D Ojima, MW Palmer, A Sharpley, L Wallace, KC Weathers, JA Wiens and WW Wilhelm. 2008. Sustainable biofuels redux. Science 322:49-50.

Ruarke, M. 2010. Biofuels in Wisconsin: What we know and what we don’t. Available at:

Searchinger, T, R Heimlich, RA Houghton, F Dong, A Elobeid, J Fabiosa, S Tokgoz, D Hayes and T-H Yu. 2008. Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land use change. Science 319:1238-1240.

Tilman, D, J Hill and C Lehman. 2006. Carbon-negative biofuels from low-input high-diversity grassland biomass. Science 314: 1598-1600.

Anerobic Digestion and Biogas

UW Extension have created seven modules focused on the use of anaerobic digestion technologies. Details of the process are introduced, as well as factors that influence start-up, operation and control of anaerobic digesters at different scales.

Contact Us:


Carol Williams
(608) 890-3858 (office)
(515) 520-7494 (mobile)
Department of Agronomy
1575 Linden Dr.
University of Wisconsin, Madison, WI 53706

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Use of contour buffer strips in commodity crop systems in southwestern Wisconsin helps reduce soil loss and traps nutrients on slopes. Photo courtesy of Wisconsin Farm Bureau Federation.