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Improving compost process efficiency by controlling aeration, temperature and pH

Sundberg, Cecilia (2005). Improving compost process efficiency by controlling aeration, temperature and pH. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae, 1652-6880 ; 2005:103
ISBN 91-576-6902-3
[Doctoral thesis]

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Abstract

Biowaste composting is rapidly increasing, and many composting plants in Scandinavia have had problems with low pH during the process. The aim of this thesis was to develop methods to improve process efficiency in large-scale composting. The investigations focused on alleviation of acid-related process inhibition and the interrelationships between decomposition rate, temperature, aeration, evaporation and oxygen concentration. Composting experiments were performed at laboratory-, pilot- and full-scale, and the microbial and physical processes were modelled and simulated. In composting of food waste a prolonged initial acidic phase can occur, resulting in low degradation rate. In successful composting, the initial phase is followed by high-rate composting at pH values above neutral. A combination of temperature above 40 °C and pH below 6 severely inhibits the composting process. Experiments at large-scale composting plants showed that it is possible to increase the activity and shorten the acidic phase by increasing the aeration rate, even though the temperature remains above 40 °C. When composting source-separated household waste in controlled 200-litre reactor experiments, the decomposition of organic matter during the high-rate phase was faster at 55 °C than at 40 or 67 °C. The ammonia emissions at 67 °C were more than double those at 55 or 40°C. Experiments were also performed in rotating 3-litre reactors, which were fed daily with fresh waste and water. In reactors with a starting culture more than four times the size of the daily feed, a well-functioning process was established. In reactors with a starting culture less than twice the daily feed, the pH decreased and the composting process failed. A dynamic model was developed for the initial self-heating phase of batch composting. It was possible to describe the process in simulations with a mesophilic microbial community tolerant to low pH and a thermophilic community inhibited by low pH. Simulations showed that in large-scale composting, the water loss is mainly determined by the accumulated decomposition. The process temperature has very little effect on the water loss.

Authors/Creators:Sundberg, Cecilia
Title:Improving compost process efficiency by controlling aeration, temperature and pH
Year of publishing :September 2005
Volume:2005:103
Number of Pages:49
Papers/manuscripts:
NumberReferences
ALLI. Sundberg, C., Smårs, S. and Jönsson, H. 2004. Low pH as an inhibiting factor in the transition from mesophilic to thermophilic phase in composting. Bioresource Technology 95 (2), 145-150. II. Eklind, Y., Sundberg C., Smårs S., Steger, K., Sundh I., Kirchmann H. and Jönsson H. 2005. Carbon turnover and ammonia emissions during composting of biowaste at different temperatures. Manuscript. III. Sundberg, C. and Jönsson, H. 2005. Process inhibition due to organic acids in fed-batch composting of food waste – influence of starting culture. Biodegradation 16 (3), 205-213. IV. Sundberg C. and Jönsson H. 2005. Initial phase of biowaste composting – aeration and pH. Manuscript. V. Sundberg C. and Carlsson B. 2005. Modelling the initial phase of batch composting. Manuscript.
Place of Publication:Uppsala
ISBN for printed version:91-576-6902-3
ISSN:1652-6880
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:Q Food science > Q70 Processing of agricultural wastes
Subjects:Not in use, please see Agris categories
Agrovoc terms:carbon dioxide, composting, degradation, energy, fatty acids, mesophile microorganisms, organic wastes, household wastes, temperature, thermophilic microorganisms
Keywords:carbon dioxide, composting, decomposition, energy, fatty acids, mesophilic, organic waste, temperature, thermophilic
URN:NBN:urn:nbn:se:slu:epsilon-750
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-750
ID Code:950
Department:?? 4072 ??
Deposited By: Cecilia Sundberg
Deposited On:30 Sep 2005 00:00
Metadata Last Modified:02 Dec 2014 10:08

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