Integrating future scenario‐based crop expansion and crop conditions to map switchgrass biofuel potential in eastern Nebraska, USA

Yingxin Gu,Bruce K Wylie

doi:10.1111/gcbb.12468

Abstract

AbstractSwitchgrass (Panicum virgatum) has been evaluated as one potential source for cellulosic biofuel feedstocks. Planting switchgrass in marginal croplands and waterway buffers can reduce soil erosion, improve water quality, and improve regional ecosystem services (i.e. it serves as a potential carbon sink). In previous studies, we mapped high risk marginal croplands and highly erodible cropland buffers that are potentially suitable for switchgrass development, which would improve ecosystem services and minimally impact food production. In this study, we advance our previous study results and integrate future crop expansion information to develop a switchgrass biofuel potential ensemble map for current and future croplands in eastern Nebraska. The switchgrass biomass productivity and carbon benefits (i.e. NEP: net ecosystem production) for the identified biofuel potential ensemble areas were quantified. The future scenario‐based (‘A1B’) land use and land cover map for 2050, the US Geological Survey crop type and Compound Topographic Index (CTI) maps, and long‐term (1981–2010) averaged annual precipitation data were used to identify future crop expansion regions that are suitable for switchgrass development. Results show that 2528 km2 of future crop expansion regions (~3.6% of the study area) are potentially suitable for switchgrass development. The total estimated biofuel potential ensemble area (including cropland buffers, marginal croplands, and future crop expansion regions) is 4232 km2 (~6% of the study area), potentially producing 3.52 million metric tons of switchgrass biomass per year. Converting biofuel ensemble regions to switchgrass leads to potential carbon sinks (the total NEP for biofuel potential areas is 0.45 million metric tons C) and is environmentally sustainable. Results from this study improve our understanding of environmental conditions and ecosystem services of current and future cropland systems in eastern Nebraska and provide useful information to land managers to make land use decisions regarding switchgrass development.

Highlights

Results from this study provide useful information to land managers and biofuel plant investors to make informed land use decisions regarding switchgrass development in eastern Nebraska
The biofuel potential areas are located across the entire study area except a small area in the southeast
Results indicate that marginal croplands potentially suitable for biofuel crop development have the smallest contribution (~8%) to the final biofuel potential ensemble areas (Table 1)

Summary

Introduction

Corn-based (Zea mays) ethanol, the most common biofuel product in the United States (Simpson, 2009; Schnepf & Yacobucci, 2010, 2013), has been suggested as being environmentally unsustainable because of soil erosion and water quality impairment from pesticide and fertilizer leakage (Searchinger et al, 2008; Simpson et al, 2008; Gelfand et al, 2010; Pimentel, 2010; Schnepf & Yacobucci, 2010, 2013; Buyx & Tait, 2011; Leduc et al, 2017). Switchgrass (Panicum virgatum) has been recommended as one potential source for cellulosic biofuel feedstocks (Sanderson et al, 1996, 2006; Mclaughlin & Kszos, 2005; Liebig, 2006; Schmer et al, 2008, 2010; Vadas et al, 2008; Bracmort, 2010; Bracmort et al, 2010; Guretzky et al, 2010; Monti et al, 2012). We estimated switchgrass biomass productivity in the Great Plains (GP) of the United States based on satellite vegetation index and site environmental variables (Gu et al, 2015). We used satellite-derived vegetation and compound topographic indices to identify highly erodible cropland waterway buffers for cellulosic

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