The optimal pretreatment condition of coconut husk by physicochemical methods for biogas production was investigated. The coconut husk was dried and ground into powder (~0.1 nm) and was then determined for chemical contents such as cellulose hemi-cellulose and lignin respectively. The chemical contents of cellulose hemi-cellulose and lignin were 35.67±2.02 7.41±0.69 and 40.82±0.62 w/w respectively. After pretreatment with 4 different methods the results showed that the pretreatment of sodium hydroxide 30 % (w/w) gave the highest chemical contents of cellulose hemi-cellulose and lignin with 43.30±0.03 33.69±7.48 and 27.36±0.03 w/w respectively. As for the biogas production the result showed that the ratio of coconut husk to cow dung of 1:4 with C:N ratio of 23:1 gave the highest cumulative biogas of 442.6 ml for 30 days. Methane and carbon dioxide contents were 46.1 and 23.1 %. Moreover the removal percentages of the total solids (TS) volatile solid (VS) suspended solids (SS) and COD were 69.3 32.5 50.0 and 58.4 % respectively. The coconut husk could be used as an alternative material for the application of biogas production with cow dung in the near future.

The purposes of this research were to investigate anaerobic digestion of concentrated food waste in biogas production system at mesophilic temperature (37 C). The effect of grinding and pH controlled at 6.20 and 7.00 on methane production were also studied. It was found that the ability of mix bacteria which had initial concentration of 2100 mg/l for digesting concentrated food waste with grinding was higher than that without grinding because of the increase in surface area (about 1.37 time). In this system the optimum condition for bacteria growth was found at pH 7.00. Under optimal condition the digestion efficiency in term of chemical oxygen demand (COD) removal was 18.81% higher corresponding to an increase in methane production rate (19.10%) than other conditions