Methane Production through Anaerobic Digestion of Various Energy Crops Irrigated with Wastewaters.

It is essential to develop sustainable energy supply systems that aim to consolidate the energy demand from renewable sources and also mitigate the emission of greenhouse gases. Biogas production is a key technology for the sustainable use of biomass as renewable energy source. High energy yields per hectare can be achieved through biogas production by using a wide range of energy crops, animal manures and organic wastes. Maize, sunflower, grass and Sudan grass are the most commonly used energy crops. With biogas production, the key factor to be optimised is the methane yield per hectare. The field experiment covered five different types of energy crops (maize, sugarbeet, sunflower, napier grass, giant reed) grown using two types of wastewaters viz. Abattoir (AWW) and municipal wastewater (MWW) at two different irrigation rates (400 and 800 mm) and tap water (TW). Dry biomass yield (DBY) was assessed from experiment. DBY data obtained from the field trial (all five crops) increased with increasing wastewater irrigation. The plots irrigated with AWW 400 and 800 mm showed significantly higher yield than the MWW (400 and 800 mm) and TW (800 mm) irrigated plots. The amount of biogas production was monitored every day and expressed as norm litre per kg of volatile solids (Nl kg-1 VS). Anaerobic digester was used to determine a reference methane yield for finely ground substrates under optimal conditions. The methane yield per hectare was calculated by multiplication of the biomass yield and the specific methane yield. Methane yields per hectare are given separately for each crop. The present data shows that the methane yield of energy crops depends on their nutrient composition. Maize (A800) exhibited the highest value in terms of potential methane yield (798.23 Nml CH4 g-1 VS). Keywords: Biogas, bioenergy, biomass, methane.