Feasibility studies on anaerobic co-digestion of food waste, brown water and cultured milk

Over the years, Singapore’s waste generation has been increasing. As of 2010, a total of 6.52 million tons (1250 kg per person) of waste has been generated as compared to 2.8 million tons generated in 1998. Much attention is been given to recycling for waste reduction. However, these recycling programs focuses more on the industrial waste and construction debris. One of the wastes for which is increasingly generated overtime due to higher population influx is food waste. Currently, there is no measure and plan being discussed to enhance food waste (FW) recycling by the government and all food waste generated were sent for incineration. This could probably be due to the lack of knowledge and research in making FW recycling economic viable. As such, this has led to the conductance of study on the feasibility of introducing commercially available cultured milk products (containing probiotics) that may ultimately become food waste when expiry date is met. In accordance to the findings of this report, the incorporation of cultured milk products (namely Vitagen and Yakult Ace Lite) had shown higher energy recovery in terms of the methane composition and volume produced. The concentrations of the cultured milk introduced were 0.2, 0.5, 1, 2 and 5% (v/v) with ≤2% (v/v) showing feasible results and 5% (v/v) inhibitory effect to the anaerobic co-digestion of FW + brown water (BW; feces without urine). Overall, 2% (v/v) Vitagen had been seen to exhibit the highest biogas (0.295 L biogas/L working volume.day) and methane (3.298 L methane/L working volume.day) production for the third experimental run conducted where run three was more representable with errors from trial run one and two negated. However, in terms of the volatile solids (VS), total and soluble chemical oxygen demand (tCOD and sCOD) reductions, compared to the findings by Rajinikanth Rajagopal et al. which investigated on potential of anaerobic co-digestion of FW + BW, 2% (v/v) Vitagen in run three depicted a significantly lower percentage. In summary, the findings of this report had illustrated the results in terms of biogas and methane production, and solids and COD reduction percentage to determine the ultimate feasibility of introducing cultured milk to anaerobic co-digestion of FW + BW. The highest biogas and methane yielded were found to be from 2% (v/v) Vitagen but with the least solids and COD reduction. Further investigations have to be made to ensure and optimize these findings for these experimental runs were done with only batch reactor design.Bachelor of Engineering (Environmental Engineering