Investigation of biochemical methane potential in Thái Nguyên city and Sông Công city in Vietnam

Abstract: Currently Vietnam is facing several problems with waste handling. For instance, a lot of the municipal organic solid waste is dumped at landfills, which contributes to environmental difficulties such as greenhouse gas emissions. Anaerobic digestion has proven to be an adequate method for solving environmental problems such as waste treatment, where biogas can be produced. The methane content in the biogas can subsequently be used as a prosperous energy source for heating, electricity and vehicle fuel. The production and utilization of biogas in Vietnam is in a developing face. However, there are issues that should be tackled to improve and expand the biogas production and use. In Vietnam the main substrate used for anaerobic digestion is animal manure as most of the biogas digesters are placed on farms. The purpose of this master thesis was to identify additional potential substrates for biogas production, with focus on Thái Nguyên city and Sông Công city in the Thái Nguyên province. In order to find suitable substrates, interviews and literature research were carried out in Vietnam. Subsequently biochemical methane potential (BMP) tests were performed for the identified and acquired substrates. The BMP-tests were first performed at Thái Nguyên University but as the results were inconclusive, further experiments were performed at Linköping University (Sweden) where eight substrates from the Thái Nguyên province were investigated. The identified substrates used for the BMP-tests were three types of beer waste from the Vicoba brewery in Thái Nguyên city, food waste from different restaurants in Sông Công city, fruit waste from the fruit market in Thái Nguyên and household vegetable waste. The highest methane yield could be observed for household vegetable waste (543 Nml/g VS) followed by beer waste (yeast) with a methane potential of 497 Nml/g VS. Beer waste (hops boiling) had the lowest methane potential with a value of 230 Nml/g VS. Estimation of the total methane potential in both cities together from food waste from restaurants, beer waste and sewage sludge from the upcoming waste water treatment plant (WWTP) in Thái Nguyen city were made by combining data from interviews, literature values and the BMP-results. The estimation showed that from Thái Nguyên City and Sông Công city about 137,500 m3 CH4/year can be produced from food waste from restaurants, about 1.7 millionCH4 m3/year can be produced from sludge from the WWTP in Thái Nguyên city (under construction) and there is also a possibility to produce about 10,700 m3 CH4/year from the beer brewery in Thái Nguyên city. Thus, the total estimated methane potential sums up to 1.8 million m3 CH4/year. The results show that Thái Nguyên city and Sông Công city have potential wastes that preferably could be used as substrates for biogas production which could add on to the biogas produced currently at farm level in the Thái Nguyên region.