Thermal treatment and densification of manure and biomass blends to produce stabilized soil amendments

Authors: MAINALI, KALIDAS - Oak Ridge Institute For Science And Education (ORISE); Sarker, Majher; Sharma, Brajendra; HOQUE, MOHAMMAD - Washington State University; HAN, YINGLEI - Washington State University; Mullen, Charles; GARCIA-PEREZ, MANUEL - Washington State University

Submitted to: Journal of Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2024
Publication Date: 12/17/2024
Citation: Mainali, K., Sarker, M.I., Sharma, B.K., Hoque, M., Han, Y., Mullen, C.A., Garcia-Perez, M. 2024. Thermal treatment and densification of manure and biomass blends to produce stabilized soil amendments. Journal of Environmental Management. 373:123594. https://doi.org/10.1016/j.jenvman.2024.123594.
DOI: https://doi.org/10.1016/j.jenvman.2024.123594

Interpretive Summary: Concentrated animal feeding operations (CAFOs) produce mountains of dairy manure each year. Historically, the primary use of animal manure is the most common land application due to its nutrient content. Overapplication of manure has several environmental concerns, including pathogen spreading, emissions of odorous chemicals (ammonia and methane), and the pollution of waterbodies with nitrogen and phosphorous containing substances. Low bulk density and water content are the main problems for the storage and transportation of this massive waste. Therefore, some strategies are still needed to tackle these problems. In this research work, manure/biomass thermally treated products were created with the help of experimental design software. The densified product was used to form pellets. This new idea helps farmers store manure long-term and easily transport it. These densified products are rich in nitrogen and carbon and are stable in soil.

Technical Abstract: Land application of dairy manure is the most common practice to dispose of this waste. Agricultural fields surrounding concentrated animal feeding operations (CAFOs) often have high levels of N and P because of manure over-application. A common practice for manure management is to separate solids from the liquid and to handle them separately. However, the low bulk density of manure limits how far manure can be economically transported for use as fuel or fertilizer. Farmers prefer using dry pelletized products that can be easily managed, stored, and applied. This research reports the development of a biomass/manure thermally treated product that contained a maximum fraction of N integrated into the biochar structure. Response Surface Methodology (RSM) was used to identify processing conditions resulting in high C and N conversion efficiencies. Experimental results show that the maximum N conversion efficiencies were achieved at Douglas fir contents higher than 50 wt. % and temperatures close to 260 °C. H3PO4 levels at 2 wt. % seems to be sufficient to catalyze the desired reactions. The KOH treatment did not significantly affect product yield and the efficiency of C and N conversion. The structural strength of densified char was evaluated using dynamic rheometric (amplitude sweep test).