3. Results and discussion
3.1. Proximate analysis, ultimate analysis and heating value
Table 1 shows the results of proximate analysis, ultimate analysis and heating values of duckweed and cattle dung. The total solid matter of biomass includes volatile organic matter and non-volatile organic matters. During anaerobic fermentation process volatile solids (VS) undergo digestion and hence is a crucial parameter deciding the amount of biogas generated from a substrate, while non-volatile solids remain unaffected (Yadav et al., 2016). The volatile content of duckweed and cattle dung was found to be 84.24± 0.2% and 62.2 ± 0.5%, approximately 20% more than cattle dung, which is very encouraging. The ash content of duckweed was found to be much lower than cattle dung which indicates that it has lower amount of non-biodegradable fractions of carbon and hence higher digestibility. Also, ash content retards the enzymatic hydrolysis i.e. saccharification of biomass samples (Bin and Hongzhang, 2010). Moisture content of the substrate is an important factor for bio-conversion processes like biogas production (McKendry, 2001). The moisture content of duckweed was found to be almost similar to that of cattle dung.