2020 article

Evaluating anaerobic digestion kinetics for swine manure using BMP assay tests

2020 ASABE Annual International Virtual Meeting, July 13-15, 2020.

By: P. Patil & M. Sharara*

Source: ORCID
Added: March 24, 2021

<b><sc>Abstract.</sc></b> Anaerobic digestion (AD) is increasingly being adopted to reduce swine manure gaseous emissions and to generate a renewable fuel stream. Assessing the ultimate biomethane potential (BMP) of swine manure is a key step to evaluate its potential as anaerobic digestion feedstock. A reliable and reproducible assay is essential for optimizing process design and to estimate greenhouse gas (GHG) emission or mitigation potential. The objectives of the current study are, a) determine BMP of swine manure solids (RM), b) model reaction kinetics for the RM digestion process, and c) assess the effect of blending pretreatment on BMP of swine manure. Three BMP assays were conducted, two with microcrystalline cellulose (MC) alone as a substrate along with blanks, and one with MC, RM and blended manure (BM) and blanks. The observed biogas yields for MC and RM were in the range 571 – 628 mL<sub>Biogas </sub>and 601 to 625 mL<sub>Biogas</sub> per gram of volatile solids (g <sub>VS</sub>).<sub> </sub>These values were higher compared to the biogas yields reported in the literature. Comparing the experimental biogas yield for RM and BM indicated no significant difference due to the blending. However, it was observed that logistic and gompertz model provided a better prediction of ultimate biogas yield for BM and RM, MC respectively. The best replicates identified via cross validation of reaction kinetics predicted an ultimate biogas yield of 535-682 mL<sub>Biogas</sub>/g<sub>VS</sub> (R<sup>2</sup>: 0.98-0.99, RMSE:12.94-27.60), 683 mL<sub>Biogas</sub>/g<sub>VS</sub> (R<sup>2</sup>: 0.99, RMSE:9.20), 588 mL<sub>Biogas</sub>/g<sub>VS</sub> (R<sup>2</sup>: 0.99, RMSE:11.79) for MC, RM and BM respectively. The confirmation of assays reliability and repeatability could not be assessed due to facility shutdown as a result of COVID-19 outbreak.