Using Marginal Lands to Produce Cellulosic Bioenergy Feedstocks in the US Midwest: Production Capacity, Greenhouse Gas Emissions, and Environmental Impacts.

Renewable bioenergy derived from plant biomass has emerged as an important alternative to fossil fuels to reduce greenhouse gas (GHG) emissions and enhance energy security. Current grain based bioethanol production has led to widespread concerns over food security and detrimental environmental impacts. Growing cellulosic crops on marginal lands has the potential to provide positive environmental outcomes while not competing with food production. Here we define marginal lands as those areas poorly suited to field crops due to inherent edaphic or climatic limitations or because of environmental constraints, such as erosion. In this presentation, we describe our research to identify marginal lands in the US Midwest using high resolution (~56 m) land use and soil maps, and use field measurements and an agroecosystem model to estimate potential productivity of cellulosic feedstocks on marginal lands and associated environmental impacts. Our initial assessment showed that growing perennial grasses on marginal lands in the US Midwest has the potential to supply an annual production of approximately 5.5 billion gallons of ethanol or one third of the cellulosic biofuel target mandated by the US Energy Independence and Security Act of 2007. Furthermore, we conducted numerical experiments to compare alternative bioenergy cropping systems on marginal lands, and found that harvesting biomass may increase negative environmental consequences (e.g. soil erosion and nutrient loss). Overall, this analysis illustrates the potential of using marginal lands to produce cellulosic biomass while alleviating food vs. fuel conflict. In doing so, soil conservation practices should be considered in order to avoid detrimental environmental impacts.