|Reardon, Catherine - Kate|
|MELLBYE, BRETT - Oregon State University|
Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2017
Publication Date: 1/31/2018
Citation: Phillips, C.L., Trippe, K.M., Reardon, C.L., Mellbye, B., Griffith, S.M., Banowetz, G.M. 2018. Physical feasibility of biochar production and utilization at a farm-scale: a case-study in non-irrigated seed production. Biomass and Bioenergy. 108:244-251.
Interpretive Summary: The use of biochar, a carbon-rich soil amendment, has been shown to improve soil quality and crop productivity by increasing moisture retention, raising pH, improving water infiltration, and increasing the fertility of highly-weathered soils. Although biochar-based amendments have become more common in small-scale horticultural and home gardening, the use of biochar in large-scale agriculture has not been widely attempted because lack of supply chains and the lack of central production facilities limit availability. In the current study, we evaluated the possibility that these economic barriers can be overcome by producing biochar on-farm from abundant agricultural wastes. Specifically, we present a case study of a farm-scale gasification system in NE Washington State, which coproduces biochar and electricity from Kentucky bluegrass (Poa pretensis L.) straw and mill screenings. The resulting biochar was used to amend subprime soils on adjacent fields, which were monitored for one-year. Our study determined that biochar applications at a rate of 8 tons per acre increased the pH of the soil, which significantly increased yield. Biochar outperformed lime in the first year of the study and improved yields by 290%. While commercially produced biochar has not been shown to be practical for large scale afarms, our studies determined that on-farm biochar production and application is a a feasible option for large scale agricultural operations. Specifically, we determined that on-farm feedstocks produced enough biochar to amend 6.3 – 11.8% of the production area annually, translating to a return interval of 9-16 years. Potential co-production of electrical power far exceeded on-farm demand for operating a seed cleaning mill. We conclude that an on-farm biochar production system is physically feasible for meeting demands for both power and liming amendments while simultaneously diverting agricultural wastes.
Technical Abstract: Despite many demonstrated benefits that biochars can have on agricultural soils, there are few examples of profitable biochar utilization on commercial farms. Barriers to profitability include successfully pairing waste streams, production facilities, and farms where biochar is utilized. However, farm-scale biochar systems, which utilize agricultural wastes as feedstocks and produce energy and biochar for on-farm use, may have efficiency advantages over regional, industrial biochar producers. Two critical uncertainties for the feasibility of on-farm production are 1) whether a biochar can be produced from on-farm feedstocks with appropriate qualities for soil amendment, and 2) whether on-farm feedstocks are sufficiently abundant to meet on-farm demand. Here we evaluate these issues for a farm-scale gasification system in NE Washington State that produces biochar from grass seed screenings and straw. Field trials to evaluate the biochar as a liming alternative found it was highly effective when broadcast at a rate of at least 18 Mg ha-1. Biochar outperformed hydrated lime in the first year of the study and improved yields by 290% across both years. Biochar produced from on-farm feedstocks were sufficient to amend 6.3 – 11.8% of the production area annually, translating to a return interval of 9-16 years. Potential co-production of electrical power far exceeded on-farm demand for operating a seed cleaning mill. We conclude that an on-farm biochar production system is physically feasible for meeting demands for both power and liming amendments.