Biogas recovery from a temperate climate covered anaerobic pond

摘要

New Zealand has over 1000 anaerobic waste stabilisation ponds treating wastewater from farmsnand industry. Traditional anaerobic ponds were not designed to optimise anaerobic digestionnto produce biogas and are therefore uncovered, releasing biogas to the atmosphere, which canncause odour problems and contributes to GHG emissions. The biogas production and treatmentnperformance of an anaerobic piggery pond retrofitted with a perimeter cover working under fieldnconditions was monitored over a 14 month period. The cover design proved successfulnin capturing biogas, mitigating odour and GHG issues and coping with New Zealand weathernconditions. High solids removal rates (73% and 86% for TS and VS respectively) were achieved.nAn annual average biogas methane production rate of 0.263m3 CH4/kgVSadded was observed,nwhich is similar to gas production rates of mesophilic farm waste digesters, and indicates thatnthe prolonged hydraulic and solids retention times of covered anaerobic ponds can fullyncompensate for lower operating temperatures. These results suggest that covered anaerobicnponds treating agricultural wastes in New Zealand have great potential to reduce odour andnGHG emissions and recover renewable energy, while producing an easy to handle effluent fornland irrigation or further treatment.