Rice Straw: An Alternative for Energy Generation by Anaerobic Co-Digestion to Pig Manure
Anaerobic digestion technology (biogas) has been used to treat husbandry wastes in the Mekong Delta of Vietnam for more than 30 years. However, biogas applications are limited. One major barrier is lack of input material for biogas digesters, because husbandry is normally conducted at the household scale. In contrast, rice straw (RS) is available in huge quantities in the Mekong Delta, but it is seldom put to use. This study tested the suitability and efficiency of anaerobic co-digestion of RS and pig manure (PM) to produce biogas. The study used 21-L lab-scale batches of anaerobic co-digestion of PM and RS, testing different sizes of RS. The mixing ratio for co-digestion was 50:50 based on organic dry matter values of input materials. The results showed that temperature, pH, alkalinity, and redox potential of almost all RS sizes were in the suitable range for activities of methanogenic microorganisms. The biogas yields per kilogram of fermented organic dry matter for the treatments were, for 1.0 cm RS, 691.05 L; 10.0 cm, 687.79 L; 20.0 cm, 685.08 L; and original RS size (uncut), 680.44 L. These values did not significantly differ from that of the 100% PM treatment. The methane content tended to increase with time, starting with the second week, and was well qualified for energy use. Our results strongly confirm that RS can be added to PM to produce biogas and that chopping RS is unnecessary.
KeywordsAnaerobic co-digestion Biogas Rice straw Mekong delta Vietnam
The authors acknowledge financial support of Danish International Development Agency project “Sustainable Production of Biogas from Waste Rice Straw” (11-016AU).
- APHA, AWWA, WPCF. (1995). Standard methods for the examination of water and wastewater (19th ed.). Washington, DC: American Public Health Association, American Water Works Association, and Water Pollution Control Federation.Google Scholar
- Eder, B., & Schulz, H. (2007). Biogas-Praxis: Grundlagen, Planung, Anlagenbau, Beispiele, Wirtschaft-lichkeit: Ökobuch Magnum.Google Scholar
- Fabien, M. (2003). An introduction to anaerobic digestion of organic wastes. Accessed from http://www.biogasmax.co.uk/media/introanaerobicdigestion_073323000101124042007.pdf. Last accessed on 9 May 2015.
- GSO—General Statistics Office of Vietnam. (2016). Statistical yearbook of Vietnam 2015. Vietnam: Statistical Publishing House.Google Scholar
- Ken, S. (2012). What every operator should know about anaerobic digestion. Accessed from http://www.wef.org/WorkArea/Downloadasset.aspx?id=12884902472. Last accessed on 9 June 2015.
- Ngo Thi Thanh Truc, & Duong Van Ni. (2009, November 16–8). Mitigation of carbon dioxide emission: An environmental assessment of rice straw burning practice in the Mekong Delta. In Workshop proceeding MEKARN—Livestock, climate change and the environment. Vietnam: An Giang University.Google Scholar
- Nguyen Cong Thuan, Bui Thi Nga, Truong Van Qui, & Taro Izumi. (2014). Biogas productions of garden weed in biogas digesters. Science and Technology Journal of Agriculture and Rural Development, 14, 27–32 (in Vietnamese).Google Scholar
- Nguyen Vo Chau Ngan, & Klaus, F. (2012). Energy recovery from anaerobic co-digestion with pig manure and spent mushroom compost in the Mekong Delta. Journal of Vietnamese Environment, 3(1), 4–9.Google Scholar
- Nguyen Vo Chau Ngan, Le Hoang Viet, Nguyen Dac Cu, Nguyen Huu Phong. (2011). Biogas production of pig manure with water hyacinth juice from batch anaerobic digestion. In M. A. Stewart, P. A. Coclanis (Eds.), Environmental change and agricultural sustainability in the mekong delta (pp. 355–371). Springer.Google Scholar
- Nguyen Vo Chau Ngan, Nguyen Truong Thanh, Nguyen Huu Loc, Nguyen Tri Nguon, Le Ngoc Phuc, & Nguyen Truong Nhat Tan. (2012). Potential use of water hyacinth and rice straw as additional loading materials for biogas digester. Can Tho University Journal of Science, 22a, 213–221 (in Vietnamese).Google Scholar
- Vo Chau Ngan Nguyen, Trung Hieu Phan, & Hoang Nam Vo. (2012). Review on the most popular anaerobic digester models in the Mekong Delta. Journal of Vietnamese Environment, 1(1), 8–19.Google Scholar
- Wang, X. J., Yang, G. H., Feng, Y. Z., Ren, G. X., & Han, X. H. (2012). Optimizing feeding composition and carbon-nitrogen ratios for improved methane yield during anaerobic co-digestion of dairy chicken manure and wheat straw. Bioresource Technology, 120, 78–83. https://doi.org/10.1016/j.biortech.2012.06.058.CrossRefGoogle Scholar
- Wiese, J., & König, R. (2007). Monitoring of digesters in biogas plants. Düsseldorf: Hach Lange GmbH.Google Scholar