Biogas production from locally available aquatic weeds of Santiniketan through anaerobic digestion

The current study focused on anaerobic digestion (AD) of aquatic weeds such as water hyacinth and salvinia available in Santiniketan, West Bengal, India. The physico-chemical analysis indicated that water hyacinth and salvinia had a total carbohydrate content of approximately 40, 32 % and C/N ratio of 29, 23, respectively. The AD of the aquatic weeds was carried out in batch mode at 2:1 inoculum to feedstock ratio over a period of 60 days using cow dung as an inoculum. The yield of biogas produced from water hyacinth and salvinia were 552 L kg⁻¹ volatile solids (VS) and 221 L kg⁻¹ VS, respectively. The maximum methane content obtained in the current study was 62 and 63 % for water hyacinth and salvinia. In Salvinia, a maximum volatile fatty acid (VFA) accumulation of 600 mg L⁻¹ was obtained after 16 days of AD and was further reduced to 25 mg L⁻¹ whereas in water hyacinth, little amount of VFA accumulation was observed throughout the digestion period. The chemical oxygen demand was reduced by 66 and 71 % while the VS content was reduced by 27 and 33 % respectively for water hyacinth and salvinia, after 60 days of digestion period. The electricity generation potential from the produced biogas was estimated to be 1.18 kWh for water hyacinth and 0.48 kWh for salvinia.