Performance Assessment of Simple Covered Lagoon Digester in Large-scale Pig Farm in Cambodia

Abstract

Simple covered lagoons are used to treat wastewater from commercial pig farms in Cambodia into biogas. The electricity is generated from biogas using a generator. However, high level of H₂S corrodes or breaks down the generator. This study aims to desulfurize biogas with commercial ferrous oxide pellets (Fe₂O₃). The effects of desulfurization system on biogas production, electricity generation, and CO₂ reduction are discussed. The results show that H₂S was reduced from 2,000 ppm before treatment to around 50 ppm after treatment. CH₄ (57.7 ± 8.76%) and CO₂ (24.7 ± 2.67%) contents were not affected by desulfurization. O₂ content was changed from 0.3 to 4.8%. High O₂ level was a sign of pipe leakage, lowering CH₄ and eventually electricity production. The increase of O₂ level decreased CH₄, thus lowering generator performance. Actual electrical output power produced from biogas was 368.5 ± 29.3 kW, with loading rates of 57.6 ± 4.6% and generator efficiency of 26.8 ± 1.7%. Estimated amounts of 22,818 tCO₂equ were reduced by the biogas system. The desulfurization system was highly effective in H₂S removal without affecting biogas quality. For the long-term biogas systems in Cambodia, local-made desulfurization systems should be tested and compared with imported products.