Removing barriers for adoption of biochar treatment to mitigate gaseous emissions from manure: can common binders improve the performance of powder and pelletized biochar?

Abstract

<p>Biochar is a fine carbonaceous powder byproduct that has many potential practical applications to improve the sustainability of crop and animal production systems. Our recent work showed that biochar powder as a surficial manure additive reduces the emissions of odorous volatile organic compounds (VOCs), ammonia (NH3), and highly toxic hydrogen sulfide (H2S) in both the short- and long term. Biochar floating on or near the manure surface improves the mitigation effect in the long-term and reduces the need for reapplication. These recent discoveries improve the potential to mitigate gaseous emissions and the sustainability of manure as a fertilizer. We identified one practical barrier to adopting this technology on a farm scale. Biochar powder can be difficult to store, transport, and apply. We hypothesized that combining biochar treatment with other biomass-derived products and/or pelletizing biochar with common and abundant binders (water, wax, soybean-based epoxy) improves the practical aspects of emissions treatment. The objective was to determine raw biochar, soybean-derived epoxy (BioMAG), and biochar pellets' (made with a combination of water, wax, and BioMAG) ability to float in water. This research was conducted in two stages. First, we tested the floatability of raw (powder) biochar, BioMAG, and biochar layered on BioMAG). The second stage tested the biochar pellets made with water, wax, and BioMAG. All tests were completed in triplicates using red oak biochar. Preliminary observations confirmed the potential for improving biochar floatability in both powder and pelletized forms. A layer of soybean-based epoxy can support raw biochar powder and improve its floatability. The best treatment was the layered BioMAG (6.5 mm) with 6.5 mm of biochar on top that stayed afloat for at least 9 days. Also, biochar powder was held together with combinations of binders and made into pellets with improved application potential. The best pellet treatment was composed of 70% biochar, 15% water, and 15% wax. This mix of biochar and binders stayed afloat for at least 9 days. Both successful results warrant further research and trials of the best treatments to mitigate gaseous emissions from manure. The results of this research are needed for scaling up the surficial treatment of stored manure with biochar powder and pellets on the pilot- and farm-scales.</p>