1. Bioenergy production from pretreated rice straw in Nigeria: An analysis of novel three-stage anaerobic digestion for hydrogen and methane co-generation.
- Author
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Ekwenna, Emeka Boniface, Wang, Yaodong, and Roskilly, Anthony
- Subjects
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RICE straw , *BIOENERGETICS , *METHANE , *ANAEROBIC digestion , *WASTE management , *HYDROGEN - Abstract
The response to Nigeria's energy inadequacies and waste management issues is projected in this research to be achieved with hydrogen and methane co-produced from pretreated (PT) rice straw (RS) in a three-stage digestion process. This study also demonstrated a novel pretreatment (PTM) agent to improve biological energy recovery from RS. The objectives were accomplished using acidogenic and methanogenic procedures in batch, semi-continuous and continuous systems after pretreating RS with chemical/potash extract (PE) followed by a biological agent. At the same time, the energy assessments were done using data from the laboratory study and the literature. The research findings indicated that at the acidogenesis stage, specific hydrogen yield was insignificant when chemical agents and PE were employed alone. However, the daily H 2 production increased when the PT RS residues were enzymatically hydrolysed with NaOH-PT (114 NmL H 2 g−1 TS d−1) and PE-PT (103 NmL H 2 g−1 TS d−1) RS substrates having the highest values at steady states and raw RS producing the least (30 NmL H 2 g−1 TS d−1). In the methanogenesis phase, chemical/ PE PTM followed by enzymatic hydrolysis of RS improved the daily specific methane production by 18%, 31.7% and 41.5% for HCl, PE and NaOH-PT RS residues. The methane production efficiency was 80% for NaOH, 75% for PE, and 68% for HCl RS PT samples, while the raw RS was 48%. The total output energy expressed in electricity and thermal production using combined cooling, heat, and power (CCHP) showed that NaOH and PE-PT RS digesters gave the highest electricity (892.43 and 852.00 KWh elect. tonne-1 TS) and thermal (1194.10 and 1140 KWh therm. tonne-1 TS) yield respectively. Similarly, the cooling fluid in KWh cool produced per tonne of TS RS was 835.57, 798.00 and 741.66 for NaOH, PE and HCl PT RS samples. Finally, whereas the Firmicutes, especially the Clostridium , Ruminococcus and Thermoanaerobacterium, were the dominant microbial community in acidogenic digestates, the Euryarchaeota typified by Methanobacterium , Methanosarcina and Methanosaeta were the principal phyla for most methanogenic reactors. [Display omitted] • Co-production of H 2 and CH 2 from PT rice straw in a novel 3-stage digestion process. • Improving rice straw energy recovery via innovative potash extract pretreatment. • Daily H 2 and CH 4 yield from RS improved with chemical/PE and enzyme pretreatment. • NaOH and PE-PT RS digesters generated the highest electricity, thermal, and cooling fluid in CCHP. • Firmicutes and Euryarchaeota dominated acidogenic and methanogenic reactors, respectively. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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