(608a) Sustainability of Biofuel Production Systems

The Great Lakes Bioenergy Research Center is one of three DOE funded Bioenergy Research Centers in the US and the only one that has a major effort devoted to the study of the sustainability of biofuels production systems.  We have used a Spatially-Explicit Integrative Modeling Framework (SEIMF) to evaluate the productivity and environmental impacts of biofuel production systems.  The modeling framework was implemented to simulate feedstock supply to a cellulosic ethanol bio-refinery located at the center of each of two Regionally-Intensive Modeling Areas (RIMA).  Feedstock sources modeled included crop residues and perennial species.  Each production system was evaluated in terms of its effect on soil erosion, water-use efficiency, soil carbon stocks, nutrient losses, nitrate leaching, and nitrous oxide emissions.  Perennial biomass crops grown on marginal lands can potentially contribute to meet cellulosic feedstock targets while avoiding food-vs.-fuel conflicts and maintaining or even enhancing ecosystem services.  The SEIMF approach together with long-term environmental data and analysis was used to model potential cellulosic ethanol production from perennial mixed prairie systems grown on marginal lands across the 10-state U.S. North Central Region.  These RIMA modeling results used to develop a spatially-explicit bio-economic model for the study of potential cellulosic biomass supply at regional scale.

We have applied ISO 14000 Life Cycle Assessment (LCA) methods to quantify the environmental impacts of a number of complex biofuels production scenarios including: a) four major ligno-cellulosic agricultural feedstocks (corn stover, switchgrass, poplar and mixed-prairie species) for RIMAs in southern Michigan and Wisconsin, b) biomass feedstocks from native forests in Northern Wisconsin, c) use of the primary AFEX pretreatment process for agricultural residues and SPORL and Dilute Acid pretreatment for woody biomass, d) final fermentation for ethanol production, e) logistics for transportation to regional preprocessing centers and final transport to a centralized ethanol production facility, and f) heat and electric power energy generation scenarios from co-products. Further, we have analyzed three potential breakthrough technologies a) creation of oil-rich grasses as dedicated energy crops, combining both the oil platform and cellulosic platform in one crop, b) feedstock pre-processing to potentially allow the use of high-diversity feedstocks (such as mixed prairie grasses) and other species, and c) use of AFEX-treated lignocellulosic biomass for cellulase production.

A paradigm shift to cellulosic biofuels seems unlikely unless several challenges can be met, including reconciling biofuels with food production, improving system environmental performance, avoiding harmful land use changes, and assembling the biomass supply chains.  In particular, local economic and environmental sustainability of the supply system is vital to advance the farmers’ interests.  Appropriately priced, low supply risk feedstocks are needed to insure the growth of the nascent biofuel industry, as is the ability to inexpensively transport and store the biomass.  Local economic and environmental concerns must be resolved in the feedstock supply chain, and diversifying the market for cellulosic feedstocks via multiple co-products would be advantageous as well.  Unfortunately, few of these properties are currently demonstrated by cellulosic feedstocks.  One promising means to address these and other issues is to process the biomass near where it is produced in so-called local biomass processing depots (LBPDs).  RBPDs would increase the stability, uniformity, density, and economic value of a potentially wide variety of cellulosic biomass.