Comparison of the value of the biogas and fuel sticks of the straw mushroom crop

Abstract

The renewable energy requirement of Thailand was increased continuously. Natural gas was the energy that has been used a lot and it was likely to be exhausted in the future. The farmers who lived in Ban Nong Kra Thum, Moo 3, Phu Luang subdistrict, Pakthong Chai district, Nakhon Ratchasima province. They planted the straw mushroom with houses. The main materials were used in the cultivation of the straw mushrooms that they were cassava pulps, cow manures, fertilizers, bran, molasses, lime and EM as 6000 : 250 : 25 : 20 : 10 : 5 : 1 kilograms, respectively. The solid wastes of the straw mushroom crop were taken for biogas production. The system was anaerobic digestion with the continuous stirred tank reactor. The fermentation was batch process. The hydraulic retention times were the 3 days, 5 days, 7 days, and 9 days. The maximum biogas production was 0.098 m3 / day in the hydraulic retention time as 5 days. The solid wastes of the straw mushroom crop were taken for the production of fuel sticks. The fuel sticks were the green charcoal and the charcoal powder briquette. The green charcoal and the charcoal powder briquette production used starches as a binder. The ratio of the solid wastes of the straw mushroom crop and starches mixing were 3:0.5, 4:0.5, and 5:0.5 kilograms, respectively. The mixtures were applied to bars with screw compressors and dryers to dry. These tests compared the heat energy of the green charcoal, the charcoal powder briquette and the normal wood charcoal. The results found that the charcoal powder briquette provided the maximum of heat energy. The equation of the relation between the heat energy to times was y = 0.293x - 0.8372 at R2 = 1. While the biogas production, the green charcoal, the charcoal powder briquette production were evaluated the value from various economic indicators. They were concluded that the green charcoal production should be most invested. The net present value (NPV) of the green charcoal production was 27,322.54 baht/year. Internal rate of return of investment (IRR) was 48.95 %. The B/C ratio was 1.04. The payback period of the green charcoal production was also the shortest of 1.73 years.