Production of biogas from palm oil mill effluent and the potential utilization of its discharge as fertilizer.

Energy demand is increasing with the growth of the human population and the development of technology. In Indonesia, the supply of energy is dominated by fossil fuels which are not sustainable. To reduce the demand for fossil fuels, it is important to develop renewable energy technology and one of them is Biogas. Biogas can be produced from various biomass including Palm oil mill effluent (POME). The utilization of POME as raw material can potentially solve energy problems as well as environmental problems. Several studies have previously been done to produce biogas from POME, however, there is limited study on semi-continuous processes. Thus, in this study, the authors did an experiment to produce biogas from POME in a semicontinuous designed reactor and compared it with a batch process to evaluate and find a better condition to produce higher amount of biogas. In addition, biogas reactor discharge was analyzed and evaluated to be used as fertilizer. In this study, cow manure is used as starter. Biogas production started by preparing cow manure and water and set in the reactor until bubbles appeared in the slurry showing the presence of active microorganisms. The biogas production with a semi-continuous process was done by removing 1 L of biogas slurry from the reactor, then mixing 0.5L of the discharge with 0.5 of POME and recycling it every day. The result shows that the semi-continuous process gives a higher volume of biogas produced. In addition, there is only a small reduction in the number of N and K components after digestion that makes the biogas slurry discharge from POME is as potential as POME to be used as fertilizer. [ABSTRACT FROM AUTHOR]