Effects of Substrate to Inoculum Ratio on the Biochemical Methane Potential of Piggery Slaughterhouse Wastes

Abstract

The aim of this study was to assess the effect of substrate to inoculum ratio (S/I ratio) on the biochemical methane potential (BMP) and anaerobic biodegradability (Ddeg) of different piggery slaughterhouse wastes, such as piggery blood, intestine residue, and digestive tract content. These wastes were sampled from a piggery slaughterhouse located in Kimje, South Korea. Cumulative methane production curves for the wastes were obtained from the anaerobic batch fermentation having different S/I ratios of 0.1, 0.5, 1.0, and 1.5. BMP and anaerobic biodegradabilities (Ddeg) of the wastes were calculated from cumulative methane production data for the tested conditions. At the lowest S/I ration of 0.1, BMPs of piggery blood, intestine residue, and digestive tract content were determined to be 0.799, 0.848, and 1.076 Nm3 kg−1-VSadded, respectively, which were above the theoretical methane potentials of 0.539, 0.644, and 0.517 Nm3 kg−1-VSadded for blood, intestine residue, and digestive tract content, respectively. However, BMPs obtained from the higher S/I ratios of 0.5, 1.0, and 1.5 were within the theoretical range for all three types of waste and were not significantly different for the different S/I ratios tested. Anaerobic biodegradabilities calculated from BMP data showed a similar tendency. These results imply that, for BMP assay in an anaerobic reactor, the S/I ratio of anaerobic reactor should be above 0.1 and the inoculum should be sufficiently stabilized to avoid further degradation during the assay.

Co-digestion and model simulations of source separated municipal organic waste with cattle manure under batch and continuously stirred tank reactors

“…2). The observations are in agreement with studies examining the effect of substrate to inoculum ratio on wastes from municipalities and livestock industry [16,31]. Indeed, high load of substrate in parallel with limited content of active biomass could lead to reactor's acidification and therefore inhibition [18,22].…”

Valorisation of the liquid fraction from hydrothermal carbonisation of sewage sludge by anaerobic digestion

“…At an ISR below 1 (runs 1–0.5, 1–0.4, 2.5–0.5, 2.5–0.4) and even at 1 for the highest IC (2.5–1), overload takes place, due to the increased availability of easily hydrolysable material in the reactor, which in turn leads to VFA and TAN accumulation, low COD removal, IA/TA ratios ≥ 0.75 and ultimately methanogenesis inhibition. As ISR of 0.5 (on a VS basis) has been reported to inhibit methane production in anaerobic digestion of winery waste, microcrystalline cellulose production wastewater and piggery slaughterhouse …”

“…As ISR of 0.5 (on a VS basis) has been reported to inhibit methane production in anaerobic digestion of winery waste, microcrystalline cellulose production wastewater and piggery slaughterhouse. 42,44,45 The results of the three experiments giving significant methane yields (1-2, 1-1 and 2.5-2), were fitted to a first-order rate equation which is a simple and useful model that has been frequently applied to anaerobic digestion systems. [42][43][44] The basic equation is:…”

Mining of hemicellulose and lignin degrading genes from differentially enriched methane producing microbial community

“…This ammonical nitrogen neutralized the acidic pH produced during food waste digestion, thereby maintaining neutral pH in the system even in absence of co-substrate . Also, it has been reported by Yoon et al (2014) that, lower organic loading and substrate:inoculum (S/I) ratios resulted in lower accumulation of VFAs thereby helping in maintenance of neutral pH during the anaerobic digestion which was conducive to growth and activity of methanogens. The ammonical nitrogen provided sufficient buffering capacity to the system, which was conducive to the activity of methanogens.…”