Biogas Production from Agricultural products
Energy Research and Development Institute-Nakornping, Chiang Mai University (ERDI-Nakornping) has conducted research and succeeded in using fresh corn stover and cassava tuber to produce biogas. The biogas yields are up to 50 m3 per ton of corn stover strain 271 and strain CP respectively and up to 300 m3 per ton of Cassava tuber strain Rayong 5. Researchers emphasize that these plants can be developed as renewable energy and can help improving problems of varying price, lack of energy, and, more important, reducing the problem of burning cornfields for land preparation which causes air pollution and global warming.
Associate Professor Prasert Rerkkriangkrai, the director of Energy Research and Development Institute-Nakornping, Chiang Mai University (ERDI-Nakornping) informed that in the past 4 - 5 years government has supported farmers in planting industrial crop widely, together with appropriate atmosphere and topography of the country. However sometimes there was too much supply to the market making price to fluctuate. Therefore, government had to spend some budget to support and guarantee its price. According to this problem, ERDI collaborated with Energy Policy and Planning Office, Ministry of Energy (EPPO) has conducted a research under the title of “Biogas Production from Agricultural Products” focusing on fresh corn stover and cassava tuber which are effective plants for biogas production and grown extensively in the country. By using the technology of anaerobic digestion, creating environment for bacteria in nature to digest organic substances in wastewater in the absence of oxygen, and producing biogas which contains methane approximately 60-70% and can be used as renewable energy in several forms, for examples, heat energy and electrical power. Thus, using agricultural products to produce biogas is another option to decrease the lack of energy and resources, and the fluctuating price of the industrial crop in the market at the same time.
Chayanon Sawatdeenarunat, one of the researchers responsible for this research said that the study of biogas production from agricultural product has been started since October 2009. By finding the efficiency in producing biogas of cassava tuber and corn stover, the result indicated that a ton of Cassava tuber strain Rayong 5 produced maximum biogas about 300 m3 that can be used to replace approximately either 420 units of electricity or 165 liters of heavy oil or 138 kilograms of LPG. For the same principle as cassava tuber, a ton of fresh corn stover strain 271 and corn stover strain CP, biogas can be produced about 50 m3, which can be used to replace approximately either 70 units of electricity or 28 liters of heavy oil or 23 kilograms of LPG. Considering 1 rai (0.4 acres) of cassava field instead, one can obtain 3.6 tons of cassava tuber that can produce about 1,080 m3 of biogas. Also, the same area of corn field provides 2 tons of fresh corn stover, which can produce 100 m3 of biogas.
The process of biogas production from fresh corn stover and cassava tuber begins with grinding fresh substrate by a hammer mill for resizing and then these substrates will be fermented in the close containers for making the silage. Next, the silage will be loaded to the 2 stages-Continuously Stirred Tank Reactor, 2 stages-CSTR. The first unit of this system called “Acid Tank”, the complex and large compounds in the prepared silage will be broken down into small soluble organic substances and then transform into organic acids which are the most important initial substrate in biogas production. After that the mixed liquor from acid tank will be piped to the second unit called “Methane Tank”. In this unit the organic acids can be converted into biogas by anaerobic microorganism. With this digestion principle, methane can be accounted for approximately 50% and 35% for carbon dioxide.
Now this project is still in need of experiments in a laboratory and the next step is pilot scale experiment and expected to be finished within the middle of 2011. The certain information of this research will be published to public for encouraging them to invest in converting agricultural products into suitable renewable energy that will help to reduce the loss of resources, the effect on the environment, and also the burning of cultivated area. Moreover, the digestate from the reactors also can be used as an organic fertilizer to improve soil quality. Last but not least, it supports employment effecting better economy in the area. In conclusion, this research could help the farmer to increase the value of their products as well as create the alternative market for agricultural products at the same time.
Further information : www.erdi.or.th ; Tel.0-5394-2007 # 156 Fax. 0-5390-3763