Effect of Manures on Food Waste Degradation in Biocell
Zaman, Md Nur Basit
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Proper disposal of food waste is a challenge due to adverse effect on the environment through generation of excessive leachate and greenhouse gas (CH4). After food loss through the food supply chain, the food waste ends up mostly in landfills. A study by EPA showed food waste to be the second largest component found in landfill. However, food waste imposes major cost on landfill management, and demands a potential alternative disposal solution that can negate the adverse effects. Though anaerobic digester and composting are possible solutions for food waste disposal, the former is highly expensive while in later solution, a valuable portion of energy is lost. Among other existing alternatives biocell landfill might offer a sustainable benefit for food waste disposal by retrieving valuable energy in a cost efficient way. In addition of being capable of handling high moisture, the addition of nutrients (e.g. livestock manures) used in biocell accelerates decomposition of waste. For organic waste especially pure food waste, addition of nutrients is necessary to prevent excessive volatile fatty acid (VFA) accumulation and thus reduction of microbial activities. However, limited studies have been conducted to evaluate the effect of nutrients (livestock manure) on food waste degradation and gas generation. Therefore, the major objective of the current study was to find out the potential of nutrient (different types of manures) addition on food waste decomposition and gas generation in biocell. Current research was conducted by preparing laboratory simulated biocell food waste reactors with four combinations; a pair of control reactors containing only food waste and the other combinations including 6% cow manure, pig manure and horse manure respectively in addition to sludge as inoculum. The reactors were operated at 37°C in an environmental growth chamber. Over the operation period, the reactors were monitored for leachate and gas measurement. For leachate, pH, volume, COD and BOD5 tests were conducted while composition and volume measurements were done for the gas generated. Based on the experimental results, it was found that all the food waste reactors showed an extended lag period (more than 100 days) before methane generation. Reactors with cow manure as nutrient presented better result compared to pig manure and horse manure. However, the lag period for the reactors with food waste and cow manure were 100 days and 135 days while the other reactors were still in lag period. During about 180 days of operation peak methane generation rate for these two reactor were 350 mL/wet-lb/day and 355 mL/wet-lb/day while the cumulative methane generation was 16 liter/wet-lb and 9.5 liter/wet-lb respectively and they were still just at the rising stage of methane generation phase; percentage of methane found in these two reactors were 75.9% and 73.4% respectively. However, methane generation from other reactors were found to be negligible; in fact most of the reactors were still in the initial lag phase. Results from the current study suggested cow manure to be a possible nutrient on food waste degradation in biocell landfill. Presence of extended lag period was an issue associated with food waste, however, methane generation was satisfactory and the percentage was comparable to that of anaerobic digester.