Simulated Biomass Sorghum GHG Reduction Potential is Similar to Maize.

Area of Science:

• Agricultural Science
• Environmental Science
• Bioenergy

Background:

• Cellulosic biofuels require significant greenhouse gas (GHG) reductions compared to corn ethanol.
• Biomass sorghum is explored as a tractable feedstock for cellulosic biofuel production.

Purpose of the Study:

• To compare life-cycle GHG emissions of biomass sorghum and corn (with and without stover) for biofuel production across the rainfed U.S.
• To assess the impact of feedstock production on soil organic carbon.

Main Methods:

• DayCent ecosystem modeling was employed.
• Simulations covered 3,265 rainfed sites across the United States.
• Evaluated feedstock dry matter yield, ethanol energy yield, and emissions intensity (g CO2e MJ-1).

Main Results:

• Biomass sorghum yielded slightly more dry matter than corn but had lower ethanol energy yield.
• High biomass removal in both scenarios led to substantial soil organic carbon losses.
• Average emissions intensity was similar between sorghum and corn with 75% stover removal.
• Southwestern sites showed lower emissions intensity for sorghum compared to corn.

Conclusions:

• Biomass sorghum feedstock production exhibits comparable GHG emissions to corn grain with stover utilization.
• Current biomass sorghum yields are unlikely to meet the Renewable Fuel Standard's emissions reduction threshold for cellulosic biofuels.
• Significant soil organic carbon depletion is a concern with high biomass removal strategies.