Boosting climate change mitigation potential of perennial lignocellulosic crops grown on marginal lands

Abstract

Nitrogen fertilizer (N _F ) is a major uncertainty surrounding the greenhouse gas (GHG) emissions of lignocellulosic biofuels. N _F enhances agronomic yields and soil C inputs via plant litters, but results in soil organic carbon (SOC) decomposition, soil N _2 O fluxes, and a large fossil energy footprint. Thus, whether N _F is beneficial or detrimental to the GHG mitigation of biofuels is unknown. Here, we show the potential GHG mitigation of fertilizing switchgrass ( Panicum virgatum ) at the N _F rate that minimizes net GHG emissions across 7.1 million ha of marginal lands in the Midwest US, with long-term production advantages surpassing emitted GHG by 0.66 Mg CO _2 e ha ^−1 yr ^−1 on the aggregate. Marginal lands limited by poor N fertility could see a much greater benefit, but not SOC-rich lands, limited by low precipitation, or short growing seasons. The objectives of maximizing yield and minimizing GHG overlap only in a few environments, suggesting that maximum yield will reduce the climate benefit of cellulosic biofuels.

Keywords

• emulators
• nitrogen
• marginal lands
• biofuels
• switchgrass
• ensemble models