Energy recovery from source-segregated brown water and food waste co-digestion

• Main Author: Poh, Li Ping.
• Other Authors: Wang Jing-Yuan
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Environmental engineering::Waste management
• Online Access: http://hdl.handle.net/10356/48964
• Institution: Nanyang Technological University

Sustainable development is the greatest challenges of the current world. The definition of sustainable development is to minimize the negative impacts on the current resources and environment without compromising one’s living quality. In order to achieve sustainable development in Singapore, more researches have to be carried out to evaluate the feasibility in managing the misplaced wastes such as activated sludge and food waste via various technologies. The existing hypothesis for transport and centralised treatment of municipal wastewater is not a sustainable solution. In this perception, the wastewater is considered as a pollutant, whereas in the decentralised concept, the wastewater is used as a resource for fertiliser, water, energy and for closing water and nutrient cycles. The decentralised treatment of municipal wastewater based on separation between grey and black water, and even between faeces and urine, represents a sustainable and future solution for waste (water) treatment. This report presents the potential alternative of using source separated brown water as a feed source for bio-energy production. Anaerobic digestion has been a traditional biodegradation method since 1859. The technology has only started to be the lime light in the recent years due to the emphasis of sustainable development. Anaerobic digestion is good at converting organic waste mass into useful biogas. With the introductory of anaerobic digestion, less methane gas is evolved from landfills. Hence, less greenhouse gas is generated which minimizes the global warming effect. Besides using the biogas to generate electricity, the activated sludge from the process is stabilized which can be used as fertilizer for agricultures purposes. According to the statistics from Singapore’s National Environment Agency (NEA), the annual generation of food waste was 542,700 tonnes in 2006 and reached about 640,500 tonnes in 2010, which is about 10% of the total waste output in Singapore. However, only 16% of food waste was recycled and the rest of food waste was sent to waste-to-energy incineration plant. It is not economical to incinerate food waste. Therefore, in this study anaerobic digestion is considered as an alternative in handling the misplaced wastes like food waste and brown water. Few researchers have studied the co-digestion of black water and food waste. However, source separation between faeces and urine, and its subsequent resource recovery approach is limited. Anaerobic co-digestion was performed in single-stage and two-phase CSTR. The results from the study have shown that anaerobic co-digestion of brown water and food waster co-digestion proved to be a potential substrate for biogas production. Additionally, it had been proven that by co-digesting food waste and brown water resulted a significant amount of biogas production in comparison to digesting purely on food waste or brown water.