Response Surface Methodology as an Optimization Tool for Anaerobic Digestion of Food Waste

Biowastes are the main fraction of municipal solid waste (MSW), and of this, food waste (FW) is the predominant component. Given that FW is predominantly biodegradable organic matter, approach strategies such as anaerobic digestion (AD) are suitable to apply on these substrates because these process also produces methane gas as a renewable energy source, particularly important given the depletion of nonrenewable energy sources. This study evaluated the influence of two parameters on AD: substrate-inoculum ratio (S/I: 0.5 to 2.0 gVS substrate gVS inoculum −1 ) and pH (7.0 to 8.0 units) on biochemical methane potential (BMP) using the response surface methodology (RSM), a valuable tool which can be used to establish strategies that allow for the control and optimization of the AD of FW. Of the conditions evaluated, it was found that the optimal S/I ratio and pH conditions to guarantee the highest BMP (297.05 ± 14.38 mL CH 4 gVS −1 ) were S/I ratio = 0.19 gVS substrate gVS inoculum −1 and pH = 7.5. Although the hydrolysis constant ( k h ) was low, in all conditions, it was in the range reported for substrates with a high carbohydrate content, such as FW (0.002–0.25 day −1 ). In this study, pH was found to be the factor that had the most significant effect on k h and BMP.