Although dedicated energy crops will probably be an important feedstock for future cellulosic bioenergy production, it is unknown how they can best be integrated into existing agricultural systems. Here we use the DayCent ecosystem model to simulate various scenarios for growing switchgrass in the heterogeneous landscape that surrounds a commercial-scale cellulosic ethanol biorefinery in southwestern Kansas, and quantify the associated fuel production costs and lifecycle greenhouse gas (GHG) emissions. We show that the GHG footprint of ethanol production can be reduced by up to 22 g of CO₂ equivalent per megajoule (CO₂e MJ^–1) through careful optimization of the soils cultivated and corresponding fertilizer application rates (the US Renewable Fuel Standard requires a 56 gCO₂e MJ⁻¹ lifecycle emissions reduction for ‘cellulosic’ biofuels compared with conventional gasoline). This improved climate performance is realizable at modest additional costs, less than the current value of low-carbon fuel incentives. We also demonstrate that existing subsidized switchgrass plantings within this landscape probably achieve suboptimal GHG mitigation, as would landscape designs that strictly minimize the biomass collection radius or target certain marginal lands.

尽管专用能源作物可能会成为未来纤维素生物能源生产的重要原料，但如何将它们最好地整合到现有农业系统中尚不清楚。在这里，我们使用DayCent生态系统模型来模拟在堪萨斯州西南部商业规模的纤维素乙醇生物精炼厂周围异质景观中生长柳枝switch的各种场景，并量化相关的燃料生产成本和生命周期温室气体（GHG）排放。我们证明，每兆焦耳最多可减少22 g CO ₂当量的乙醇生产的温室气体足迹（CO ₂ e MJ ^–1），通过精心优化耕种的土壤和相应的肥料施用率（美国“可再生燃料标准”要求“纤维素”生物燃料与传统汽油相比，降低56 gCO ₂ e MJ ^-1生命周期的排放量）。以适度的额外成本即可实现这种改善的气候性能，其成本低于低碳燃料激励措施的当前价值。我们还证明，该景观中现有的补贴柳枝plant种植可能实现了次优的GHG缓解，以及严格地最小化生物量收集半径或以某些边缘土地为目标的景观设计。