Aerobic Composting of Palm Oil Mill Biogas Sludge and Empty Fruit Bunches Using Earthworms and a Compost Accelerator

Abstract

This research investigates aerobic composting using palm oil mill biogas sludge, and mixed with shredded empty fruit bunches (EFB). The decomposers used in the process include microorganisms from the composting materials, earthworms (Eisenia fetida and Eudrilus eugeniae in a 1:1 ratio), and Super LDD1 compost accelerator. The experiment was conducted using seven reactors. Reactors 1, 2, and 3 used 100% biogas sludge, while reactors 4, 5, 6, and 7 used a mixture of 50% biogas sludge and 50% shredded EFB. Reactor 1 relied on natural aeration, whereas reactors 2 to 7 were supplied with air using a blower at a rate of 0.7 L/min·kg. Earthworms were added to reactors 3 and 5, Super LDD1 was added to reactor 6, and both earthworms and Super LDD1 were added to reactor 7. The composting process was carried out over a period of 77 days. Parameters analyzed included temperature, pH, electrical conductivity, moisture content, organic carbon, organic matter, C/N ratio, total nitrogen (Total N), total phosphorus (Total P₂O₅), total potassium (Total K₂O), particle size, and germination index. The results showed that most parameters in all reactors met the 2014 organic fertilizer standards of the Department of Agriculture, with the exception of moisture content and organic matter. Reactor 7 produced compost with the highest nutrient content (Total N : Total P₂O₅ : Total K₂O = 1.70% : 2.00% : 1.35%) and a germination index of 201.46 ± 6.28%. The compost from reactor 7 was crumbly, black in color, and had an earthy odor.