| Summary: | Composting provides environmental benefits including an alternative method for organic
waste disposal, as well as improving soil fertility. However poor compost quality and odour
emission are often significant problems in the composting industry. Composting process control
can potentially help reduce both of these problems. In spite of the recent development of a
number of process control strategies, very few direct comparisons have been made between
these, particularly in terms of compost quality and odour emission. To help address this need, a
series of experiments was conducted to evaluate the effects of several in-vessel process control
strategies on compost quality and odour emission. The strategies tested focussed on aeration
control, which in turn affects temperature, oxygen, and moisture, the most important conditions
for microbial activity. Fixed aeration (Beltsville method), temperature feedback (Rutgers
method), oxygen feedback, and combined temperature/oxygen feedback were tested. A modified
algorithm based on temperature, called linear temperature feedback, was also developed and
tested. Results showed that while many quality parameters such as C:N ratio and organic matter
loss were similar between process control methods, compost oxygen was maintained more
consistently using oxygen feedback or linear temperature feedback methods; these methods may
also provide greater nitrification and lower phytotoxicity. Linear temperature feedback is
preferable to oxygen feedback in that it does not require oxygen sensors to operate. Odorous gas
(including ammonia) mass emission rates were typically found to increase with higher aeration
rates, such as those used to limit temperature, though the gas concentration was lower. For
maximum retention of nitrogen, adequate supply of readily biodegradable carbon in the
feedstock is vital. === Applied Science, Faculty of === Chemical and Biological Engineering, Department of === Graduate
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