Waste to watt: Anaerobic digestion of wastewater irrigated biomass for energy and fertiliser production

This study aimed to investigate the potential of energy crops for biomethane production by examining the influence of abattoir and municipal wastewater irrigation on biomass production and the Biochemical Methane Potential (BMP). The experiments covered seven energy crops including sugar beet, alfalfa, maize, giant reed, napier grass, sunflower and canola. The biomass was harvested at three months of planting and BMP of each energy crops was assessed using anaerobic digestion. Giant reed yielded the highest biomass (22.3 t ha−1) from A800 treatment compared to the other species. The best performance for BMP (793.56 Nml CH4 g VS−1) was recorded for maize biomass irrigated with abattoir wastewater which is equivalent to gross energy yield 1041 GJ ha−1 yr−1 or electricity yield 284.8 MW h ha−1 yr−1. The digestate samples collected after anaerobic digestion of biomass from plants were analysed for their nutrient value. Nutrient content of digestates varied between energy crops, waste water sources and irrigation levels. The highest nitrate content was measured for giant reed (A800) and phosphate and sulphate contents for sugar beet leaf (A800). The results indicated that wastewater sources can be used to grow energy crops, thereby producing biomethane for energy and digestate for plant nutrition through anaerobic digestion process. [Display omitted] •Biomass yield influenced by wastewater type and was highest in abattoir wastewater.•BMP was significantly influenced by wastewater type and irrigation rate.•The highest BMP was achieved for maize with abattoir wastewater treatment.•Maize with abattoir wastewater produced highest gross energy or electricity yield.•Both wastewater type and irrigation rates affected the nutrient value of digestates.