- Joint Program Report
The production of cellulosic biofuels may have a large influence on future land emissions of greenhouse gases. These effects will vary across space and time depending on land-use policies, trade, and variations in environmental conditions. We link an economic model with a terrestrial biogeochemistry model to explore how projections of cellulosic biofuels production may influence future land emissions of carbon and nitrous oxide. Tropical regions, particularly Africa and Latin America, are projected to become major producers of biofuels. Most biofuels production is projected to occur on lands that would otherwise be used to produce crops, livestock and timber. Biofuels production leads to displacement and a redistribution of global food and timber production along with a reduction in the trade of food products. Overall, biofuels production and the displacement of other managed lands increase emissions of greenhouse gases primarily as a result of carbon emissions from deforestation and nitrous oxide emissions from fertilizer applications to maximize biofuel crop production in tropical regions. With optimal application of nitrogen fertilizers, cellulosic biofuels production may enhance carbon sequestration in soils of some regions. As a result, the relative importance of carbon emissions versus nitrous oxide emissions varies among regions. Reductions in carbon sequestration by natural ecosystems caused by the expansion of biofuels have minor effects on the global greenhouse gas budget and are more than compensated by concurrent biofuel-induced reductions in nitrous oxide emissions from natural ecosystems. Land policies that avoid deforestation and fertilizer applications, particularly in tropical regions, will have the largest impact on minimizing land emissions of greenhouse gas from cellulosic biofuels production.