Effects of microbial community, lipids and pretreatment on the performance of the two-phase anaerobic digestion
Compared to conventional anaerobic digestion (AD), two-phase AD strategy, in which acidogenesis and methanogenesis reactions can be optimized separately, offers a robust and flexible means to better control the process of decomposing organic solid waste to renewable energy at an upgraded level. In r...
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| Format: | Theses and Dissertations |
| Language: | English |
| Published: |
2009
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| Online Access: | https://hdl.handle.net/10356/15154 |
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| Institution: | Nanyang Technological University |
| Language: | English |
| Summary: | Compared to conventional anaerobic digestion (AD), two-phase AD strategy, in which acidogenesis and methanogenesis reactions can be optimized separately, offers a robust and flexible means to better control the process of decomposing organic solid waste to renewable energy at an upgraded level. In recent years, a modified two-phase AD system, known as the hybrid anaerobic solid-liquid (HASL) system, was successfully developed by the Nanyang Technological University (NTU). The HASL system is characterized by recirculating alkaline methanogenesis phase broth to buffer the quick food waste acidity that is often encountered in the acidogenesis phase, so as to realize a self-relief of pH inhibition with no need for external chemical addition. Albeit the HASL system has demonstrated excellent capacity in overcoming the inherent pH issue in conventional food waste AD, information about its potential in mineralizing the recalcitrant food waste components is very limited. Technically, food waste is a mixture of organic substances with various biodegradabilities. The recalcitrant fraction tends to pass through the AD system without sufficient degradation. Some hydrolyzed products from food waste may even be toxic to microorganisms responsible for AD. Meanwhile, the efficiency of the hydrolysis, the rate-limiting step in AD, also determines the ultimate methane yield in the overall process. Thus, enhancement of hydrolysis is critical to improve the overall performance. For these regards, this thesis is focused on the influence of the food waste recalcitrant fraction on the performance of the HASL and the enhancement of hydrolysis by thermal and freeze/thaw pretreatments, with molecular biotechnology as an insightful tool. |
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