Impact of Residue Removal for Biofuel Production on Soil:

Renewable Energy Assessment Project (REAP)

Project Summary:

Domestic ethanol production is a strategy for reducing dependence on imported energy and release of greenhouse gases from use of fossil-energy-derived motor vehicle fuel. Federal and state governments are encouraging the use of ethanol. In addition to grain, energy crops, such as switchgrass, willow, and poplar, have been targeted as sources of bio-energy. Recently crop residues, especially corn stover and wheat straw, have been identified as an additional and more available source of cellulosic biomass.

However, limits must be placed on the amount of crop residue removed for bio-energy production to protect lands from erosion and to sustain soil organic carbon (SOC). Research over the past century demonstrated conclusively that many prevailing crop production practices result in SOC loss. Typically, loss of SOC has detrimental effects on soil productivity and quality. Soil erosion removes topsoil, which is rich in nutrients (e.g. C, N, P), thus further reducing the quality of soil in the field.  The displacement of soil from the field into waterways increases turbidity and accelerates eutrophication, thereby degrading water quality. Our objectives are to determine the amount of residue needed to protect the soil resource, to compare economic implications of using stover as a bio-energy feedstock vs. as a source of C to build SOC and sequester C, and to provide harvest rate recommendations and guidelines.

Products from this work will be 1) guidelines for management practices supporting sustainable harvest of residue, 2) algorithm(s) estimating the amount of crop residue that can be sustainably harvested, and 3) decision support tools and guidelines describing the economic trade-off between residue harvest and retention to sequester soil C. Delivery of this knowledge and these products to farmers and the biomass ethanol industry will promote harvest of stover and crop residues in a manner that preserves the capacity our soil to produce food, feed, fiber, and fuel. The acronym REAP (Renewable Energy Assessment Project) has been established for this project to aid communication among team members, within ARS, and with clients.

Printable REAP Brochure (pdf)

Participants: