Evaluation of Biogas Production from Food Waste Under Thermophilic and Mesophilic Conditions under Swiss Conditions

Abstract

Green fuel production from food waste can help manage waste disposal. A study was conducted to test the efficiency of biogas production under different temperature conditions in small-scale anaerobic digesters from canteen food waste and biogas slurry from waste water treatment plant as starter culture of Yverdon Les Bains, under Swiss conditions, which have potential for waste disposal and energy supply in urban areas. This anaerobic digester was operated first at thermophilic then mesophilic temperature ranges with specific bacteria active in each range. Efficiency of the biogas digester was checked with varying the temperature in the digester from thermophilic to mesophilic conditions, with and without stirring for a period of three months. Temperature, methane concentration and biogas flow rate were continuously acquired using a Labview® Data Acquisition System, developed in-house with a lab-scale digester. The digester was constructed of stainless steel with a water jacket heated by an electric water heater with a circulating pump and agitation provided by impellers and baffles. The study shows anaerobic digestion can recover from abrupt changes between thermophilic and mesophilic conditions without intervention or changing the feeding regime. ATP analysis showed that microorganisms stress was higher under thermophilic than under mesophilic conditions. We can conclude that for food waste and mixtures of food-waste and cow-dung under thermophilic conditions result in increased biogas flow and an 11% increase in methane concentration compared to mesophilic condition, without stirring. Results also show biogas production reached 66% of methane at pH of 7.48 and volume concentration within the first month under thermophilic condition (56-58⁰C). Later the same digester was set to mesophilic conditions, i.e. 30-40⁰C with an efficiency of 55%. Maximum and continuous biogas was recorded above 57⁰C until 59⁰C with better solid destruction and biogas yield.