The Effect of Intermediate Ozonation Process on Improving Biogas Production from Co-Digestion of Agricultural Waste and Manure

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Millions tons of solid waste (SW) are generated from agricultural, municipal, and industrial sources every year. The amounts of SW are expected to increase exponentially in the coming decades, due to the growth of the world’s population and the increase in levels of development . Anaerobic digestion (AD) of solid waste and animal manure is an effective way to reduce the impact of the waste and to reduce the amounts of greenhouse gas emission. Although anaerobic digestion is a very well-known technology, a fundamental gap in knowledge still exists regarding the response of AD and embedded microbial communities to solid waste treatment. The aim of this study is to investigate the effect of intermediate chemical oxidation by ozone for improving the digestion of different substrates and enhancing biogas production. In addition, the effect of different operational parameters (total solid content, substrate structure, and volatile solids) on the performance of the AD process and on biogas production will be investigated. The performance of anaerobic digestion (AD) was monitored by assessing VS removal efficiencies, the biogas production rate, and the biogas yield and composition. A number of strategies, including controlling the composition of the substrate and employing chemical oxidation with ozone, were tested to determine if they resulted in an increase in amount of biogas produced. The cumulative biogas production for 30 days of single digestion range from 36.2 to 156.8 L/kgVS.h, with the highest production rate occurring for substrates with C/N ratios in the 20–30 range, COD in the 185–240 mgCOD/L range, and TS in the range 10–15%. Finer substrates showed an increase in biogas production by 56% over coarser substrate. The production of biogas increased with increasing substrate VS/TS ratio, reaching a cumulative biogas production of (40 NL) at a VS/TS ratio of 45% and (181 NL) at a VS/TS ratio of 76. An intermediate ozonation step was introduced to measure the effect of interstage chemical oxidation on the biogas yield. Experiments using AgrMun-1, 5, and 6 were carried out by digesting these substrates in AD for 10 days; the substrate was then oxidized with ozone for 10 min with different inlet ozone doses (1, 3, and 5 mg/L). Following this, the substrate was digested again for another 10days. Using ozone to oxidize the sludge produced from the first digestion increases the biogas by 19%–31.3% for the same substrate.

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Journal: TechConnect Briefs
Volume: 2, Materials for Energy, Efficiency and Sustainability: TechConnect Briefs 2016
Published: May 22, 2016
Pages: 170 - 174
Industry sectors: Advanced Materials & Manufacturing | Energy & Sustainability
Topic: Biofuels & Bioproducts
ISBN: 978-0-9975-1171-0