BIOEN WORKSHOP ON THE IMPACT OF LAND USE CHANGE AND BIOFUEL CROPS ON SOILS AND THE ENVIRONMENT
PROGRAM
9:00 h Welcome Coffee
9:30 h Opening Ceremony
10:00 h Marcos Jank (UNICA, São Paulo, Brazil)
Prospects of the Sugarcane Bioenergy Sector
10:20 h Evan H. Delucia (University of Illinois, Urbana-Champaign, Illinois, EUA)
Ecology and Sustainability of Biofuels
11:10 h Isaias de Carvalho Macedo (NIPE-Unicamp, Campinas, Brazil)
Emission and Mitigation of Greenhouse Gases in the Production and Use of Ethanol from Sugarcane
12:00 h Discussion
12:30 h Lunch
14:00 h Kristina J. Anderson-Teixeira (University of Illinois,Urbana-Champaign, Illinois, EUA)
Contributions of Land Use Change to the Greenhouse Gas Budget of Biofuels
14:40 h Carlos C. Cerri (CENA/USP, Piracicaba, Brazil)
Stock of Carbon and Greenhouse Gases Production Associated with Sugarcane Cultivation in Brazil
15:20 h Segundo Urquiaga (Embrapa Agrobiologia, Seropédica, Brazil)
Variations in Carbon Stock and Greenhouse Gases Emission in Tropical and Subtropical Soils of Brazil
16:00 h Discussion
16:30 h Conclusions and Research Needs
Speakers and invited debaters: J.E. Corá and C.E.P. Cerri
ABSTRACTS
Ecology and Sustainability of Biofuels
Evan H. DeLucia
Managing global climate change and obtaining a sustainable supply of clean energy represent two of the greatest challenges facing society. Biofuels, particularly those derived from plants, are touted as a way to meet these challenges. In many cases, large scale deployment of biofuel crops (feedstocks) represent a major change in current land use practices that potentially alters the biogeochemical cycles of carbon, nitrogen and water. A thorough understanding of the ecological consequences of the deployment of biofuel crops is essential for understanding their sustainability. We have established side-by-side experimental plots of four biofuel crops (maize, switchgrass, miscanthus, mixed prairie) to quantify their effects on biogeochemical processes. Initial results during the establishment phase suggest that second generation feedstocks (switchgrass, miscanthus, prairie) provide ecological benefits when planted in areas currently used for row crop agriculture (maize and soybean), including restoring soil carbon and reducing nitrogen losses to ground water. A review of life-cycle analyses that quantify the total energy and material costs of producing biofuels from plants revealed enormous inconsistencies but point to unacceptable economic and ecological costs of relying on ethanol production from maize, a so called first generation biofuel. While our initial results suggest that second generation biofuels have the potential to improve the ecology of agricultural landscapes, care must be taken to fully understand the consequences of removing land from grain production on world food security.
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Contributions of Land Use Change to the Greenhouse Gas Budget of Biofuels
Kristina J. Anderson-Teixeira
Mitigation of climate change through reduced greenhouse gas (GHG) emissions is a primary motivation for biofuel cultivation. It is therefore critical to quantify the uptake or release of GHG’s that occurs as a result of biofuel-associated land use change (delta GHG luc). We delineate the terms that contribute to delta GHG luc and show that current life cycle analyses of liquid biofuels fail to account completely for the GHG effects of land use change. To fully quantify delta GHG luc, we quantify the GHG values of pertinent ecosystem types in terms of both storage of materials that would be released as GHG’s upon land clearing and annual fluxes of CO2, CH4, and N2O. We show that delta GHG luc is substantial and generally underestimated in life cycle analyses, and that it will often determine whether or not GHG emissions can be reduced through biofuel cultivation.
One important element of delta GHG luc is the change in soil organic carbon (SOC) that occurs upon conversion of natural or agricultural land to biofuel crops. We assembled estimates of changes in SOC under corn with residue harvest, sugarcane, Miscanthus x giganteus, switchgrass, and restored prairie. We show that conversion of uncultivated land to biofuel agriculture results in significant SOC losses, which would counteract the benefits of fossil fuel displacement. Corn residue harvest consistently results in SOC losses, implying that its potential to offset C emissions may be overestimated. In contrast, SOC accumulates under all four perennial grasses, with SOC accumulation rates averaging <1 mg="" ha="" sup="">-1 yr-1 in the top 30 cm. Thus, SOC sequestration under perennial grasses represents an additional benefit that has rarely been accounted for in life cycle analyses of biofuels.
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Variations in C stock and GHG emissions in tropical and subtropical soils of Brazil
Urquiaga Segundo, Jantalia Claudia P., Alves Bruno J.R., Boddey Robert M.
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