Research on "biogas production from rice straw and water hyacinth: effect of size" was carried out in order to find suitable sizes of rice straw (RS) and water hyacinth (WH) for biogas production. In this research, the anaerobic experiment was conducted with five sizes of RS and WH: 0.05 cm, 0.2 cm, 0.5 cm, 1.0 cm and original size. Each size was conducted with five replications in 21L batch digester for 60 days. The experimental result shows that cumulative biogas production of RS 1cm (158.3 L) and WH (210.4 L) higher than other sizes. In term of biogas yield, the highest value was observed in RS 1cm (764 L/kg VS degraded) and WH (843 L/kg VS degraded). The sizes of RS and WH have no significant effect on the biogas composition. The experimental results reveal that the smaller size of RS and WH the easier dropping pH due to cumulative total volatile fatty acid. Water hyacinth and rice straw can be potential resource for biogas production
Keywords: size, water hyacinth, rice straw, biogas, batch anaerobic
digestion