|POPP, MICHAEL - University Of Arkansas|
|WEST, CHUCK - Texas Tech University|
Submitted to: Energies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2021
Publication Date: 4/23/2021
Citation: Popp, M., West, C., Ashworth, A.J. 2021. Simulating the feasibility of dual use switchgrass on cow-calf operations. Energies. 14(9):2422. https://doi.org/10.3390/en14092422.
Interpretive Summary: Considerable interest exists to expand the supply of biofuels generated from cellulosic feedstock to avoid direct competition with food production as is currently the case with ethanol generated from corn. Researchers set out to identify how hay feed needs— either sourced from conventional forage species with two cuttings along with attendant yield and quality attributes (leading to subsequent supplemental herd nutrition in the form of corn to meet cow needs) or switchgrass harvested in June— can be met with the intent of holding beef output and land use constant, while modifying fertilizer (poultry litter) and corn use. With anticipated higher cost of production when employing switchgrass rather than conventional forage species (fertilizer, supplemental feed and higher forage establishment and maintenance costs), the second cut of switchgrass in the fall needs to more than offset the added cost to enhance operator profitability. Quantifying these effects in terms of net greenhouse gas emissions and breakeven revenue needed for second-cut switchgrass for operations with spring- and/or fall-calving herds would thus help determine the supply potential from mixed beef cattle, hay, and poultry operations in the mid-southern U.S.
Technical Abstract: With expected demand for lignocellulosic biomass for biorefineries comes the need to find feed-stock sources that do not affect food or feed supply. We analyzed an average-sized mixed operation with 31 ha of hay and 125 ha of pasture, along with 96 cows and poultry production. By converting conventional forage species to switchgrass (SG; Panicum virgatum) for hay lands, we use a cow-calf simulation model that tracks biophysical production aspects of forage species selection along with attendant economic and net greenhouse gas (GHG) emission changes to evaluate the feasibility of maintaining beef output constant in a dual-use system. Rather than using hay land for feed use of the cow herd only, the operation uses the first SG cutting for hay and the second cut for biomass. To remain feed- and beef production neutral with the change to SG, a modest increase in fertilizer-use and supplemental corn to meet nutrition requirements of the herd were estimated. Per farm, a 3.6 to 3.8% reduction in net GHG emissions for fall- and spring-calving operations, respectively, an attendant approximate increase in profit of $2K, and a supply potential of 122 MT of switchgrass using a dry matter switchgrass price of $50 MT-1 regardless of calving-season was observed. Therefore, mixed hay and lignocellulosic operations are expected to not display food production, while suppling second-generation feedstocks and reducing climate forcing gases.