Abstract
Environmentally benign, economically viable, and socially acceptable agronomic strategies are needed to launch a sustainable lignocellulosic biofuel industry. Our objective was to demonstrate a landscape planning process that can ensure adequate supplies of corn (Zea mays L.) stover feedstock while protecting and improving soil quality. The Landscape Environmental Assessment Framework (LEAF) was used to develop land use strategies that were then scaled up for five U.S. Corn Belt states (Nebraska, Iowa, Illinois, Indiana, and Minnesota) to illustrate the impact that could be achieved. Our results show an annual sustainable stover supply of 194 million Mg without exceeding soil erosion T values or depleting soil organic carbon [i.e., soil conditioning index (SCI) > 0] when no-till, winter cover crop, and vegetative barriers were incorporated into the landscape. A second, more rigorous conservation target was set to enhance soil quality while sustainably harvesting stover. By requiring erosion to be <1/2 T and the SCI-organic matter (OM) subfactor to be > 0, the annual sustainable quantity of harvestable stover dropped to148 million Mg. Examining removal rates by state and soil resource showed that soil capability class and slope generally determined the effectiveness of the three conservation practices and the resulting sustainable harvest rate. This emphasizes that sustainable biomass harvest must be based on subfield management decisions to ensure soil resources are conserved or enhanced, while providing sufficient biomass feedstock to support the economic growth of bioenergy enterprises.
Highlights
Corn stover (Zea mays L.) has been targeted as a primary herbaceous bioenergy feedstock in the USA because of its abundance and logistical infrastructure [1, 2]
Conventional tillage was not included because (1) this study focused on identifying opportunities for conservation practices to support residue removal and (2) it was assumed that stover harvest would decrease residue management challenges currently faced by land managers that often lead to intensive tillage choices
Economic analysis using Policy Analysis System (POLYSYS) resulted in a residue availability of 56.8 million Mg (4.4 Mg ha−1) for the baseline Billion Ton Update (Table 1; scenario 1)
Summary
Corn stover (Zea mays L.) has been targeted as a primary herbaceous bioenergy feedstock in the USA because of its abundance and logistical infrastructure [1, 2]. While the anticipated 2014 launch of three full-scale corn stover-based conversion facilities is encouraging for lignocellulosic biofuels, sustainable feedstock supplies must increase dramatically to achieve the national goal of 61 billion L year−1 of cellulosic derived fuel by 2022 [3]. To meet this demand, an estimated 242 million Mg year−1 of lignocellulosic biomass is required for conventional biochemical conversion process yielding 252 L Mg−1 [4]. The SCI value generated through RUSLE2 and WEPS is used to qualitatively describe whether soil organic matter is being increased, decreased, or sustained as a function of biomass input, erosion, and management operations. Further details on the function of each of these three major models, their use in LEAF, and examples of other published uses are discussed in Muth et al [20]
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