Site Suitability Classification for Saturated Bioenergy Buffers and Area Estimates in the U.S. Midwest

Highlights Suitability criteria for saturated bioenergy buffer (SBB) sites were developed. A method to classify cropland areas as suitable SBB sites was demonstrated using public data. The criteria and method for classifying suitable SBBs were generally successful at U.S. Midwest sites. Areas were identified within U.S. Midwest states having the greatest potential for SBB implementation. Abstract. Nutrient loss from tile-drained, row-crop fields is a major component in the impact of agricultural production on surface water quality, because drain tiles provide a short-circuit for nutrient-rich drainage water to reach ditches and eventually downstream waterbodies (e.g., creeks, streams, rivers). Saturated buffers (SBs) help address the tile-drainage water quality problem, and incorporating bioenergy crops into SBs (saturated bioenergy buffers, or SBBs) could provide both environmental protection and an economic benefit to farmers. The objectives of this analysis were to: (1) develop a site suitability classification approach for rapid, cost-effective identification of SBB candidate sites; and, after validation, (2) use it to estimate the size of land in the U.S. Midwest considered suitable for SBB sites. The approach uses several biophysical parameters to identify sites that (1) are likely to be tile-drained, row-cropped agricultural land; (2) have conditions conducive for denitrification; and (3) have stable streambanks. Supporting data came from federally funded and maintained U.S. databases (e.g., Soil Survey Geographic Database). This classification approach was implemented in ArcGIS Desktop and validated using data from various SB field studies in the U.S. Midwest. This approach has proven to be robust because it identified SB sites considered to be either performing or promising in reducing nitrate losses in tile drainage water with an accuracy range of 57% to 63%. SBB candidate areas in the U.S. Midwest totaled up to 225,000 ha and 342,000 ha for buffer widths of 20 and 30 m, respectively. The proposed approach could assist in both local siting and regional-scale implementation of SBBs, which could significantly mitigate nitrate loss in tile-drained U.S. Midwest agricultural lands while providing other environmental benefits and economic incentives for farmers. Keywords: Biomass production, Multi-functional landscapes, Sustainable agricultural land management, Tile-drained agriculture, Water quality protection.