Incineration is not suitable due to the high moisture contents and low heating value of food waste. So, mesophilic anaerobic digestion has been one of the most favorable options for food waste disposal. In this study, a series of batch experiment was carried out to investigate the effects of mixing ...
Incineration is not suitable due to the high moisture contents and low heating value of food waste. So, mesophilic anaerobic digestion has been one of the most favorable options for food waste disposal. In this study, a series of batch experiment was carried out to investigate the effects of mixing ratio of food waste and swine manure at different volatile solids (VS) loading on biogas production. This study also was carried out to investigate the feed to inoculum (F/I) ratio effect on biogas production. Also, the biogas production from food waste was investigated using lab scale semi-continuous stirred tank reactor (SCSTR) at 35 oC with 30d HRT. Total volume of reactor was 38 liter with working volume of 30 liter. Biogas yields of food waste and swine manure mixture was determined using batch type anaerobic digester at mesophilic (35±2 oC) temperature. The food waste and swine manure mixture initially added to the reactors was composed of 100:00, 60:40 and 40:60, based on the volatile solid (VS) at 1% (10 g VS/L) and 3% (30 g VS/L). Also, the mesophilic digestion of food waste alone was conducted with different F/Is at two different VS loading. At three mixing ratios of food waste and swine manure (100:0, 60:40 and 40:60), the biogas yield was determined to be 925, 1113 and 1148 mL/g VS for the VS concentration of 10 g VS/L; 110, 814 and 586 mL/g VS for 30 g VS/L, respectively, after 30 days of digestion period. The biogas yield was obtained to be 1008, 952 and 720 mL/g VS at F/I of 0.50, 0.72 and 1.14, respectively, for the VS loading of 10g VS/L. Also, the biogas yield was obtained to be 127, 111 and 151 mL/g VS at F/I of 1.50, 2.14 and 3.41, respectively, for the VS loading of 30g VS/L. The results showed that the mixing ratio, VS concentration and F/I ratio significantly affected the biogas production rate. The highest biogas yield of 1148 mL/g VS was obtained at mixing ratio of 40:60 and VS concentration of 10 g VS/L. An experiment of semi-continuous flow anaerobic reactor was carried out to study the VFA effects on biogas and methane yields in mesophilic condition. During the start-up (25d) for semi-continuous operation, 22.5L of food waste (75% of total working volume) and 7.5L of inoculums (25% of total working volume) was used as the mixed slurry (30L). The semi continuous feeding was initiated with comparatively high VFA concentration (1999 mg/L) of food waste (FW-1) during 0-34 days; comparatively low VFA concentration (908 mg/L) of food waste (FW-2) was used during 35-45 days; and again high VFA and other chemical concentration of food waste (FW-3) was used during the last days (46-60 days) of experiment. Food waste VS concentration always was maintained with 3%. During each phase, food waste was changed when steady-state condition, characterized by a constant gas production rate (±5%), was achieved. The results showed that the food waste contained well balanced nutrients for anaerobic microorganisms and the highest biogas yield was determined to be 842.67 mL/g VS loaded at steady condition of stage I (30-34d). The results of this study indicate that the food waste is a highly desirable substrate for anaerobic digesters with regards to its high biodegradability and methane yield.
Incineration is not suitable due to the high moisture contents and low heating value of food waste. So, mesophilic anaerobic digestion has been one of the most favorable options for food waste disposal. In this study, a series of batch experiment was carried out to investigate the effects of mixing ratio of food waste and swine manure at different volatile solids (VS) loading on biogas production. This study also was carried out to investigate the feed to inoculum (F/I) ratio effect on biogas production. Also, the biogas production from food waste was investigated using lab scale semi-continuous stirred tank reactor (SCSTR) at 35 oC with 30d HRT. Total volume of reactor was 38 liter with working volume of 30 liter. Biogas yields of food waste and swine manure mixture was determined using batch type anaerobic digester at mesophilic (35±2 oC) temperature. The food waste and swine manure mixture initially added to the reactors was composed of 100:00, 60:40 and 40:60, based on the volatile solid (VS) at 1% (10 g VS/L) and 3% (30 g VS/L). Also, the mesophilic digestion of food waste alone was conducted with different F/Is at two different VS loading. At three mixing ratios of food waste and swine manure (100:0, 60:40 and 40:60), the biogas yield was determined to be 925, 1113 and 1148 mL/g VS for the VS concentration of 10 g VS/L; 110, 814 and 586 mL/g VS for 30 g VS/L, respectively, after 30 days of digestion period. The biogas yield was obtained to be 1008, 952 and 720 mL/g VS at F/I of 0.50, 0.72 and 1.14, respectively, for the VS loading of 10g VS/L. Also, the biogas yield was obtained to be 127, 111 and 151 mL/g VS at F/I of 1.50, 2.14 and 3.41, respectively, for the VS loading of 30g VS/L. The results showed that the mixing ratio, VS concentration and F/I ratio significantly affected the biogas production rate. The highest biogas yield of 1148 mL/g VS was obtained at mixing ratio of 40:60 and VS concentration of 10 g VS/L. An experiment of semi-continuous flow anaerobic reactor was carried out to study the VFA effects on biogas and methane yields in mesophilic condition. During the start-up (25d) for semi-continuous operation, 22.5L of food waste (75% of total working volume) and 7.5L of inoculums (25% of total working volume) was used as the mixed slurry (30L). The semi continuous feeding was initiated with comparatively high VFA concentration (1999 mg/L) of food waste (FW-1) during 0-34 days; comparatively low VFA concentration (908 mg/L) of food waste (FW-2) was used during 35-45 days; and again high VFA and other chemical concentration of food waste (FW-3) was used during the last days (46-60 days) of experiment. Food waste VS concentration always was maintained with 3%. During each phase, food waste was changed when steady-state condition, characterized by a constant gas production rate (±5%), was achieved. The results showed that the food waste contained well balanced nutrients for anaerobic microorganisms and the highest biogas yield was determined to be 842.67 mL/g VS loaded at steady condition of stage I (30-34d). The results of this study indicate that the food waste is a highly desirable substrate for anaerobic digesters with regards to its high biodegradability and methane yield.
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#Anaerobic digestion Biogas production Substrate loading Swine manure Food waste
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