Dry anaerobic co-digestion of food waste and cattle manure: Impact of total solids, substrate ratio and thermal pre treatment on methane yield and quality of biomanure.

The objective of the present study is to assess the impact of TS concentration, substrate mixing ratio (co digestion) and thermal pretreatment on biogas production, methane yield, VS reduction (%) and quality of biomanure through dry anaerobic digestion (DAD) of food waste (FW) and cattle manure (CM). Results divulged that the optimum methane yield and biomanure of 0.18 and 0.21 m3 CH4/(kg VS reduced) and 3.15 and 2.8 kg/kg waste was obtained from FW at TS of 25% and 30% at an HRT of 41 and 31 days respectively whereas it was 0.32 and 0.43 m3 CH4/(kg VS reduced) and 2.2 and 1.15 kg/kg waste from pretreated FW at an HRT of 16 and 20 days correspondingly. Improvement of methane from 62 to 81% was obtained due to thermal pretreatment. The highest nutrient recovery in terms of N, P, K was found to be 5.14, 2.6 and 3.2 respectively.

Rapid generation of volatile fatty acids (VFA) through anaerobic acidification of livestock organic waste at low hydraulic residence time (HRT).

The purpose of this study was to investigate the effect of pre-treatment and F/M (Food to Microorganism) ratios for the rapid generation of volatile fatty acids (VFA) from livestock organic wastes (cattle manure (CM) and poultry litter (PL)) through an anaerobic acidification process at a pH range of 4.5-5.5. Experiments were organized using CM and PL in batch reactors (1L and 25L) with and with no pre-treatment of substrate at F/M ratios (0.4, 0.6, 0.8 and 1). Among various existing pre-treatments methods, thermal-acidic (120°C; 1% H2SO4) pre-treatment was found effective. The results revealed that 0.31 and 0.47kg VFA/(kg VS reduced) could be obtained from CM and PL respectively with no pre-treatment, whereas it improvised to 0.43 and 0.67kg VFA/(kg VS reduced) correspondingly due to pre-treatment. Aforesaid, better yield of VFA was obtained at F/M ratio of 1.0, pH-5.5 and hydraulic residence time of 4days.

Exploitation of rapid acidification phenomena of food waste in reducing the hydraulic retention time (HRT) of high rate anaerobic digester without conceding on biogas yield.

The aim of the present work was to study and infer a full scale experience on co-digestion of 1000kg of FW (400kg cooked food waste and 600kg uncooked food waste) and 2000L of rice gruel (RG) on daily basis based on a high rate biomethanation technology called "Anaerobic gas lift reactor" (AGR). The pH of raw substrate was low (5.2-5.5) that resulted in rapid acidification phenomena with in 12h in the feed preparation tank that facilitated to obtain a lower hydraulic residence time (HRT) of 10days. At full load, AGR was fed with 245kg of total solids, 205kg of volatile solids (167kg of organic matter in terms of chemical oxygen demand) which resulted in the generation of biogas and bio manure of 140m3/day and 110kg/day respectively. The produced biogas replaced 60-70kg of LPG per day.

Generation of bioethanol and VFA through anaerobic acidogenic fermentation route with press mud obtained from sugar mill as a feedstock.

Acidogenic anaerobic fermentation route was explored for the production of bioethanol and volatile fatty acids (VFA) from the press mud (PM) obtained from sugar mill. Slurry was prepared from PM having 10% of total solids and the same was hydrolyzed under acidic thermal conditions. Both press mud slurry (PMS) and pre-treated press mud slurry (PTPMS) was used as feedstock with mixed microbial consortia (MMC) and enriched mixed microbial consortia (EMMC). Mix of bioethanol and VFA were obtained in all the four cases (PMS-MMC, PMS-EMMC, PTPMS-EMC and PTPMS-EMMC), but, bioethanol and VFA yield of 0.04 g/g and 0.27 g/g, respectively obtained from PTPMS with EMMC was found to be comparatively higher. Control experiments carried out with glucose yielded bioethanol and VFA of 0.042 g/g and 0.28 g/g, respectively demonstrating that the organism was using reducible sugars in the feedstock for the generation of bioethanol by simultaneously producing the VFA from COD.