Ponds and anaerobic digestion combination

Abstract

Production of biogas from small farms in China is decreasing because of the decrease in farm animals at these farms. It is needed a replacement for the animal manure. The replacement looked into in this paper is an algae pond with wet organic solid waste (WOSW) in combination with an anaerobic digester (AD). The main focus of the algae type and the type of WOSW were Chlorella Vulgaris and wheat straw respectively. It was developed a chemical oxygen demand (COD) balance in Microsoft Excel to investigate the theoretical production of biogas. The two cases that were tested were the case with algae pond and WOSW and a case with algae pond and silage. The pond was investigated for surface areas of 10, 20, 30, 40 and 50 m2. It was shown that theoretically the increase of biogas is 0.1 m3 CH4 gas per day when you increase the pond size by 10 m2. In the silage case it was investigated on how much mass that was needed to produce twice the volume of biogas from the AD. The same mass that was found in the silage case was then used in different ways to investigate the WOSW. In both cases the production of biogas will increase. How much the biogas will increase depends on the size of the farm and the space available to build the pond. Connecting WOSW and algae pond to an AD looks like a promising way to increase the biogas production. It should be look into in more detail and with experiments.