|Lindsay, Karen - UNIVERSITY OF ARKANSAS|
|Popp, Michael - UNIVERSITY OF ARKANSAS|
|West, Charles - TEXAS TECH UNIVERSITY|
|Rocateli, Alexandre - OKLAHOMA STATE UNIVERSITY|
|Farris, Rodney - OKLAHOMA STATE UNIVERSITY|
|Kakani, Gopal - OKLAHOMA STATE UNIVERSITY|
|Fritschi, Felix - UNIVERSITY OF MISSOURI|
|Green, Steven - ARKANSAS STATE UNIVERSITY|
|Alison, M - LSU AGCENTER|
|Mawg, Michael - UNIVERSITY OF MISSOURI|
|Acosta-gamboai, Lucia - LSU AGCENTER|
Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2017
Publication Date: 11/16/2017
Citation: Lindsay, K.R., Popp, M.P., West, C.P., Ashworth, A.J., Rocateli, A.C., Farris, R., Kakani, G., Fritschi, F.B., Green, S.V., Alison, M.W., Mawg, M.J., Acosta-Gamboai, L. 2017. Predicted harvest time effects on switchgrass moisture content, nutrient concentration, yield, and profitability. Biomass and Bioenergy. 108:74-89. https://doi.org/10.1016/j.biombioe.2017.09.017.
Interpretive Summary: Poultry production is a large economic sector for agriculture in our region, and biorefineries need consistent sources of biomass for ethanol production, but crop composition often changes over time based on fertilizer source. These changes directly impact cost for production, as fertilizers and biomass drying before conversion are among the greatest costs for production. Therefore, to optimize the economic viability of these systems, USDA-ARS and university researchers compared poultry litter as a cheaper source of nutrients to commercial fertilizers in order to determine if lower nutrient costs would substantially alter harvest date recommendations and nutrient content in the harvested biomass. Results showed that a single-pass harvest with fertilizers was not economically justifiable because of the declines in yield that occurred by letting the standing crop dry to low enough moisture levels for direct storage. When poultry litter was used to replace commercial fertilizers, earlier harvests could occur because nutrient cost savings offset in-field yield losses and costs for drying biomass, which allows for greater harvest date flexibility for producers. This study is of interest to farmers, scientists, and agency personnel because it helps identify production practices that reduce economic costs for biofuel production.
Technical Abstract: Production costs change with harvest date of switchgrass (Panicum virgatum L.) as a result of nutrient recycling and changes in yield of this perennial crop. This study examines the range of cost of production from an early, yield-maximizing harvest date to a late winter harvest date at low moisture and low nutrient concentration using different harvest systems as dictated by the moisture content of the standing crop. Harvest systems with a field-drying interval and multiple harvest passes were compared to a single-pass harvest when moisture content had naturally declined to storage-safe conditions or when artificial drying at the plant would be required. Results showed that the single-pass harvest requiring artificial drying was not economically justifiable at all locations, as drying energy requirements were either i) as costly or more so than declines in yield observed with letting the standing crop dry to 20% moisture in the field; or ii) not economically viable in comparison to conventional multi-pass harvest with a field drying interval at higher yield. Sites where yield losses due to harvest delays were small showed promise for the single-pass harvest at storage-safe moisture, as nutrient replacement costs with greater nutrient recycling and harvest cost savings with a single pass offset yield losses with delayed harvest. Extending the harvest season had different producer cost ramifications amongst environments and led to large changes in nutrient concentrations in harvested biomass. This may be problematic for biorefineries seeking stable nutrient content in feedstock.