Potential valorisation of agro-industrial wastewater for bioenergy production

Agro-industries generate a high amount of solid waste, wastewater and emissions. In Indonesia's case, many small and medium-scale agro-industries have problems in treating or in valorising their wastes. Specific to wastewater, due to lack of waste treatment facilities or financial support, as well as lack of policies enforcement, many agro-industries directly disposed of the wastewater to the river bodies. Such practices can have a detrimental effect on the environment due to the accumulation of both organic and an-organic pollutants. This study aimed to investigate the potential of various agro-industrial wastewater (i.e. batik wastewater, tofu-processing wastewater and tempeh-processing wastewater) from Malang City as single feedstock for biogas production. The biochemical methane potential (BMP) test was employed under a mesophilic condition and operated for 28 days. The results indicated that anaerobic digestion (AD) of tempeh-processing wastewater produced more biogas and methane potential compared to other wastewater samples. The specific methane potential (SMP) from the AD of tempeh-processing wastewater was 0.027 m3/kgVSadded. However, the energy potential calculation indicated that using these wastewater samples was not feasible as a single feedstock for an anaerobic digestion system. Therefore, combining with other potential biomass feedstock as co-substrates is recommended for further in-depth investigation.