Evaluation of methane potential from swine slurry with poultry litter amendments

Abstract

In this study, an evaluation of methane production from swine slurry amended with poultry litter was carried out. Anaerobic batch reactors (250 mL) containing different mixtures of swine and poultry litters were set up to evaluate methane potential from each scenario. As an ancillary study, five scenarios were set up as follows: (1) sterile swine waste and sterile poultry litter; (2) sterile swine waste and non-sterile poultry litter; (3) non-sterile swine waste and sterile poultry litter; (4) non-sterile swine waste and non-sterile poultry litter; and (5) non-sterile swine waste only to study the effect of substrate sterility on biomethanation. Sterilization was carried out by autoclaving and nitrogen gas was used to purge the headspace of the reactors to obtain anaerobic conditions. Biogas productions were sampled and monitored by gas chromatography. The results showed that methane productions increased as the solid concentrations (poultry litter) increased. Rice-hull litter provided a better substrate for methane production than wood-chip litter. In addition, methane productions were the greatest when non-sterile swine waste was used (scenarios 3 and 4). Methane productions were more than several times greater from reactors with swine waste amended with poultry litter (scenarios 3 and 4) than the ones with swine waste only (scenario 5) and sterile swine waste (scenario 2). There was no methane production in the sterile control (scenario 1). Thus, it appears that poultry litter is necessary to increase methane production from swine waste anaerobic digester. Poultry litter appears to provide an additional substrate and microbes for methanogenesis in an otherwise diluted swine waste for optimum methane production.