Effect of Recycling Digestate Filtrate for Cow Dung Dilution on Biogas Production

Abstract

Biogas production in the Sahelian zone faces the problem of water shortage during the dry season. This study was initiated in the bioscience laboratory at the University of Maroua with the objective of improving the accessibility of households to biogas in water scarcity conditions. Also another aim is to recycle the filtrate of the digestate into a new dilution of the substrate for biogas production. Thus, the Cow Dung (CD) digestate from the biogas unit was filtered. Two types of filters were made: filter with sand and cotton and filter with sand, biochar and cotton. The filtrate obtained was used to make five treatments with CD to feed mini biodigesters (1st generation) of 1 liter each. After a HRT of 30 days, the digestate from the 1st generation was again filtered into the same treatments (2nd generation). During the anaerobic digestion; the production and pH of each treatment repeated three times were evaluated. The effect of water recycling and the type of filtration were analyzed. This study shows that the dilution of CD with the filtrate from the 1st generation significantly improves on the production of biogas by 47% compared to that of dung diluted with ordinary water. In the 2nd generation, dilution with ordinary water provided the best production which is 7% higher than that obtained from the filtrates without biochar. As the pH is concerned, it varies between 6 and 7.5 when filtrates are used. It was more acidic when water has been used.