Assessment of co-digestion of poultry litter and swine wastewater: the effect of enriched inoculum on biogas production

Abstract

BACKGROUND

Co-digestion of substrates represents a viable strategy to enhance biogas production. This study evaluates biogas generation from the liquid fraction obtained through phase separation of co-digested swine manure and poultry litter, to assess the influence of the inoculum-to-substrate ratio (ISR) and to analyze the effect of microbial inoculum enrichment on the anaerobic digestion process. Methane production potential tests were conducted using a Doehlert experimental design, with co-digestions comprising 0–40% (w/w) poultry litter, and ISR levels of 2, 1.25 and 0.5.

RESULTS

The highest methane production values (286–284 NL kgVS⁻¹) were achieved in co-digestions containing 10% to 20% (w/w) poultry litter, conditions that are compatible with the use of covered lagoon or continuous stirred tank reactor-type digesters. In the microbial inoculum enrichment study, a 34% increase in methane production was observed compared to the use of standard inoculum.

CONCLUSIONS

The co-digestion of swine manure and poultry litter, followed by phase separation and anaerobic digestion of the liquid fraction, proved to be a feasible strategy, achieving up to a sevenfold increase in methane production per ton of added substrate. Microbial enrichment further promoted a significant increase in methane yield; however, this approach requires further development for full-scale application. Gompertz kinetic modeling produced results closely matching the experimental data. © 2025 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).