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Agricultural waste and residues such as corn stover, wheat straw, and rice straw are readily available feedstocks for second generation biofuels

Summary​

Agricultural waste and residues serve as a major feedstock for second generation biofuels, primarily consisting of lignocellulosic material that lacks nutritional value for humans and animals. In the United States, corn stover by far represents the largest source of agricultural residue, followed by wheat straw and rice straw. Key environmental considerations include preserving soil organic carbon levels and preventing erosion by leaving sufficient residue on fields. A major benefit of using agricultural residues is the avoidance of induced land use change and food versus fuel competition.

Agricultural wastes and residues have been proposed as a major feedstock for the production of second generation biofuels. Agricultural residues tend to consist primarily of lignocellulosic material which is high in cellulose, hemicellulose, and lignin which generally lack nutritional value for humans and animals and are therefore often considered a low value 'waste' product.

Agricultural residues in the United States​

The primary source of agricultural residue in the United States is from corn production, known as corn stover 1 2. Corn stover consists of all biomass residues from the corn harvest excluding the corn kernels, and can include the stalks, leaves, cobs and husks. Corn has an approximate residue-to-grain ratio of 1:1, meaning that for every 1 ton of corn harvested, 1 ton of corn stover is produced 2. As corn is one of the most grown crops in the United States, the amount of residue produced is enormous, with an estimated 70% of all agricultural residues in the United States consisting of corn stover 2. Interestingly, a significant portion of this residue production is a result of the existing corn ethanol industry, with approximately 35% of all corn grown in the United States being used for ethanol, utilizing over 30 million acres of land 3 4.

After corn, wheat straw is the second most abundant source of agricultural residue in the United States, followed by rice field residues, and cotton field residue and other small grain residues from products such as oats, barley and sorghum 2. Although soybeans constitute a major part of the United States agricultural production coming in at second place behind corn 5, soybean residues cannot be harvested due to environmental concerns, as almost all of the residue needs to be left on the field 1 2.

Environmental considerations​

Environmental concerns regarding agricultural residues primarily revolve around soil organic carbon, erosion control and general soil health. As a general rule, in order to maintain soil organic carbon levels, at least 60-70% of all residue needs to be left on the field; however, this can vary depending on region, soil type, and tillage practices 2. In order for collection of agricultural residues for a second generation biofuels program to be considered sustainable, removal of agricultural residues must not exceed the tolerable soil loss limit as recommended by the USDA’s Natural Resource Conservation Service (NRCS), and removal must not result in long-term soil organic matter loss 2.

The major environmental benefit of using agricultural residues is the fact that it circumvents induced land use change (ILUC) and the resulting issue of food vs fuel competition.

Collection of agricultural residues​

Current collection methods for agricultural residues are capable of collecting a maximum of 50% of available residue, leaving the remaining 50% on the field 1. Collected residues can then be easily baled for storage and transportation. Next generation harvesting equipment is capable of harvesting the corn grains whilst dynamically collecting or distributing residues at the same time to minimize labor and reduce the need for a second harvesting pass over the field 1.

Biomass availability​

Near-term availability of agricultural waste and residue biomass in the United States is estimated to be 140 million dry tons per year.

Sources​

Footnotes​

  1. Langholtz, M. H. (Lead). (2024). 2023 Billion-Ton Report: An assessment of U.S. renewable carbon resources (ORNL/SPR-2024/3103). Oak Ridge National Laboratory. https://doi.org/10.23720/BT2023/2316165 ↩ ↩2 ↩3 ↩4

  2. Downing, M., Eaton, L. M., Graham, R. L., Langholtz, M. H., Perlack, R. D., Turhollow, A. F., ... & Brandt, C. C. (2011). U.S. Billion-Ton Update: Biomass supply for a bioenergy and bioproducts industry (No. ORNL/TM-2011/224). Oak Ridge National Laboratory. ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7

  3. U.S. Department of Energy. (2024). U.S. corn production and portion used for fuel ethanol. Alternative Fuels Data Center. https://afdc.energy.gov/data/10339 ↩

  4. Sturchio, M. A., Gallaher, A., & Grodsky, S. M. (2025). Ecologically informed solar enables a sustainable energy transition in US croplands. Proceedings of the National Academy of Sciences, 122(17), e2501605122. https://doi.org/10.1073/pnas.2501605122 ↩

  5. United States Department of Agriculture. (2025, January). Crop Production 2024 Summary (ISSN: 1057-7823). National Agricultural Statistics Service. https://downloads.usda.library.cornell.edu/usda-esmis/files/k3569432s/nk324887m/qn59s0097/cropan25.pdf ↩