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Permanent link (DOI): https://doi.org/10.7939/R3QN5ZQ19

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Integration of Anaerobic Digestion and Composting Facilities Open Access

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Other title
Subject/Keyword
Anaerobic digestion
composting anaerobic digestate
Integration of anaerobic digestion and composting
composting
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Arab, Golnaz
Supervisor and department
Daryl McCartney, Civil and Environmental Engineering
Examining committee member and department
Dr. Yang Liu, Civil and Environmental Engineering, University of Alberta
Dr. Grant Clark, Faculty of Agricultural and Environmental Sciences (McGill University)
Dr. Christian Felske, Civil and Environmental Engineering, University of Alberta, (adjunct professor)
Dr. Samer Adeeb, Civil and Environmental Engineering, University of Alberta
Dr. Ian Buchanan, Civil and Environmental Engineering
Dr. Bipro R. Dhar, Civil and Environmental Engineering, University of Alberta
Department
Department of Civil and Environmental Engineering
Specialization
Environmental Engineering
Date accepted
2017-04-24T10:27:12Z
Graduation date
2017-06:Spring 2017
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Interest in organic waste treatment has increased in recent years due to growing rate of organic waste generation. Implementing biotransformation technologies helps to divert organic waste from landfill, reduce greenhouse gas emission, and produce valuable final products. This research was conducted in two parts. The general goal of the first part was to extend the overall knowledge in organic waste characterization, generation rate, sources, and sampling. While in the second part, which is the main part of the dissertation, the focus was on anaerobic digestion and composting processes and integration of these two biotransformation technologies. In the first part (Chapter 2), a sampling methodology was proposed for higher education institutions (HEI’s), as one of the main generators in institutional, commercial, and industrial (ICI) sectors. Representative organic waste was collected according to the proposed methodology and characterized in terms of their physical, chemical, and biological properties. In the second part, different options of digestate post treatment were investigated in an integrated anaerobic digestion and composting system. Co-composting of digestate and organic fraction of municipal solid waste (OFMSW) was studied in terms of physicochemical parameters and microbial population dynamics in Chapter 3 and 4, respectively. Digestate was prepared by running a high solid anaerobic digestion (HSAD) reactor with the working volume of 500 L. Then it was mixed with OFMSW in eight different mixing ratios; 0, 10, 20, 30, 40, 50, 75, or 100% (wet mass). Composting reactors with working volume of 25 L were monitored for 100 days including 30 days of aeration and 70 days of curing. Monitored parameters were temperature, mass changes, total solids, organic matter, pH, and electrical conductivity. Stability and maturity endpoints were also quantified by running respirometry, C:N ratio, ammonium to nitrate ratio, and Solvita® tests. The results revealed that the reactors with 20 to 40% (%ww) digestate had better performance in terms of organic matter (OM) removal, temperature evolution, and also stability time. Results also showed that total ammonia nitrogen (TAN) available in the digestate could be an effective parameter in organic matter degradation and composting performance. Concentration above 5000 TAN mg.kg-1 DM found to be unfavorable for the biological activities where the improvement in composting performance was observed in the lower concentrations of TAN. OFMSW could also enhance the physicochemical properties of the digestate by balancing free air space, moisture content, and C:N ratio parameters. Simpson index calculated from pyrosequencing results also showed that microbial diversity was higher in the reactors with better performance. Proper mixing ratio of the digestate and OFMSW, 20 to 40%, (%ww) probably provided the most favourable condition for bacteria and fungi activities. Higher relative abundance of the two bacterial phyla, Thermoactinomycetaceae and Actinomycetales, in the reactors with 20 to 40% digestate indicated a potential of high efficient and rapid composting. In the fungal community, Galactomyces, Pichia, Chaetomium, and Acremonium were the four genera probably involved in higher OM degradation in the reactors with better performance. In Chapter 5, co-composting of polished digestate and composted OFMSW was studied as another option for further treatment of digestate. 8-day aerated digestate was mixed with composted OFMSW in eight different mixing ratios; 0, 20, 30, 40, 50, 60, 80, or 100% (wet mass) as feedstock for the curing process. Curing process was monitored during 100 days, with the same physicochemical analyses applied in the previous options. The results demonstrated that the two main feedstocks could not take advantages of each other and composting performance decreased when the digestate portion increased. This could be due to loss of N during aeration of the digestate and/or inappropriate inoculation time. Overall, comparing all the investigated options demonstrated that co-composting of the digestate and OFMSW with the mixing ratio of 20 to 40% was associated with higher OM degradation, higher temperature generation, and shorter stability time. Therefore co-composting of digestate with the OFMSW is suggested as a reliable and robust method for further treatment of the digestate.
Language
English
DOI
doi:10.7939/R3QN5ZQ19
Rights
This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
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