|VOZHDAYEV, GEORGIY - University Of Minnesota
|MOLDE, JOSEPH - University Of Minnesota
|HEILMANN, STEVEN - University Of Minnesota
|WOOD, BRANDON - University Of California
|VALENTAS, KENNETH - University Of Minnesota
Submitted to: Trade Journal Publication
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2018
Publication Date: 2/5/2018
Citation: Vozhdayev, G.V., Spokas, K.A., Molde, J.S., Heilmann, S.M., Wood, B.M., Valentas, K.J. 2018. Impact of two hydrothermal carbonization filtrates on soil greenhouse production. Agronomy Journal. 2(1):48-61.
Interpretive Summary: This article details the evaluation of the liquid residual present after the hydrothermal processing of different manure wastes and their corresponding impact on soil microbial greenhouse gas production. The research demonstrated that at high application rates, these residual liquids are inhibiting the rates of gas prodcution. However, with dilution these inhibitory effects are reduced or eliminated. These results suggest that this liquid product could be considered for fertilizer use. This would represent a renewable source for nitrogen and phosphorus fertilizers, which would improve agricultural sustainability. These results are significant to farmers and policy makers and will assist scientists and engineers in using more sustainable fertilizer sources.
Technical Abstract: Hydrothermal carbonization (HTC) is a thermochemical treatment process that allows for the conversion of wet biomass slurries to new liquid and solid products. A majority of the research to date has focused on the solid HTC product (hydrochar). Less attention has been paid to the utilization of the HTC filtrate, which comprises the larger mass fraction of the process. Finding value added products for this liquid phase is pivotal for HTC to be an economically viable treatment option for waste biomass. Laboratory soil incubations were performed to determine alterations in microbial functionality by quantifying greenhouse gas (CO2, CH4, and N2O) production and nitrogen mineralization rates following filtrate application. Results of these studies confirmed inhibitory effects of high application rates of condensed distiller soluble HTC filtrate (> 0.2 mL g-1) on agricultural soil microbes for a 2-week period after application, but this inhibitory effect was not observed for a swine manure filtrate. On the other hand, lower rates of application stimulated mineralization of the filtrate and increased soil N-availability during the 2-week period. More importantly, the simple storage of filtrate in an open container for 90 days altered the observed impact on soil microbes, reducing the initial inhibitory effects. These observations lead to the conclusion that there are volatile organic chemicals present in the original filtrate that are responsible for the observed negative effects which are lost though storage (volatilization or microbial mineralization). Even though the effects observed here are dependent on feedstock type, applied concentration, and post-treatment of the applied filtrate, this data does support the continued examination of the utilization of HTC filtrates as a renewable source of agricultural nutrients.