Site-Specific Trade-offs of Harvesting Cereal Residues as Biofuel Feedstocks in Dryland Annual Cropping Systems of the Pacific Northwest, USA

• Published in: Bioenergy research 2014-06, Vol.7 (2), p.598-608
• Main Authors: Huggins, David R, Kruger, Chad E, Painter, Kathleen M, Uberuaga, David P
• Format: Article
• Language: English
• Subjects: Agricultural ecosystems; Agricultural practices; Agricultural production; agricultural statistics; Agronomy; Analysis; arid lands; Arid zones; Barley; Biodiesel fuels; Biofuels; Biomass energy; Biomedical and Life Sciences; Carbon; conventional tillage; Corn; Crop production; Crop residues; Crop rotation; Cropping systems; Ethanol; ethanol production; Farming; farms; feedstocks; Fertilizers; Food; Harvest; Harvesting; Hordeum vulgare; Life Sciences; Loam soils; market value; markets; No-tillage; nutrient management; Nutrient removal; peas; Plant Breeding/Biotechnology; Plant Ecology; Plant Genetics and Genomics; Plant Sciences; Raw materials; reduced tillage; simulation models; Soil contaminants; Soil degradation; Soil erosion; soil organic carbon; Soil quality; Soil sciences; Straw; Studies; Sustainable energy; Tillage; Triticum aestivum; Water conservation; Water shortages; Wheat; Wildlife conservation; Wood Science & Technology
• ISSN: 1939-1234; 1939-1242
• DOI: 10.1007/s12155-014-9438-4

Cereal residues are considered an important feedstock for future biofuel production. Harvesting residues, however, could lead to serious soil degradation and impaired agroecosystem services. Our objective was to evaluate trade-offs of harvesting wheat and barley residues including impacts on soil erosion and quality, soil organic C (SOC), and nutrient removal. We used agricultural data from 369 geo-referenced points on the 37-ha Washington State University Cook Agronomy Farm combined with model simulations to develop straw harvest scenarios for conventional tillage (CT) and no-tillage (NT) and both 2- and 3-year crop rotations with sequences of wheat, barley, and peas. Site-specific estimates of ethanol production from 2- and 3-year rotation scenarios ranged from 681 to 1,541 L ha⁻¹ yr⁻¹, indicating that both crop rotation and site-specific targeting of residue harvest are important factors. Harvesting straw reduced residue C inputs by 46 % and resulted in levels below that required to maintain SOC under CT. This occurred as a function of both straw harvest and low residue producing crops in rotation. Harvesting straw under CT was predicted to reduce soil quality as Soil Conditioning Indices (SCIs) were negative throughout the field. In contrast, SCIs under NT were positive despite straw harvest. Replacement value of nutrients (N, P, K, S) removed in harvested straw averaged $14.54 Mg⁻¹ dry straw and ranged from $36.04 to $80.30 ha⁻¹, while straw harvesting costs averaged $34.25 Mg⁻¹, and the current (2014) market value of straw is $65 Mg⁻¹. We concluded that substantial trade-offs exist in harvesting straw for biofuel, that trade-offs should be evaluated on a site-specific basis, and that support practices such as crop rotation, reduced tillage, and site-specific nutrient management need to be considered if residue harvest is to be sustainable.