## 3 Results and Discussion
### Estimation of Heat Produced during the Composting Process  
The heat produced during the composting results from the aerobic microbial degradation of the organic waste. The resultant heat can be captured and applied as a bioenergy source. However, before this comes to fruition, the amount of heat that can be generated from the composting needs to be quantified. Unlike combustion, composting does not undergo full oxidation, and therefore the heat produced is relatively lower. Equation (1) was used to estimate the heat produced during our composting experiment. The equation assumes the process is at a constant pressure with a constant specific heat capacity. This is a valid assumption during composting, which has relatively small changes in pressure [38]. \[q=ms\Delta T \tag{1}\]  
where \(q\) is the heat (kJ), \(m\) is the mass (kg), \(s\) is the specific heat (kJ/kg \({}^{\circ}\)C), and \(\Delta T\) is the temperature difference (\({}^{\circ}\)C). The mass was taken to be 400 kg, the initial weight of the compost mixture, and was assumed not to vary within the 30 days. The ambient temperature was taken to be 30 \({}^{\circ}\)C during the entire process. The overall specific heat capacity of the compost, presented in Table 2, was estimated based on the relative amounts of the compost material and their standard specific heats. Therefore, the estimated heat produced from the compost pile in the 30 days was 1194 MJ. This equates to 2.99 MJ/kg of food waste which was higher than the heat produced from the mushroom and municipal waste composting values reported in previous studies (Table 3). However, it was lower than the values reported by [22]. This is because the heat produced during the composting depends on the energy content of the compost mixture, its biodegradability, and the prevailing composting conditions [25]. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Material** & **Amount Present (\%)** & \(s\) **(kJ/kg \({}^{\circ}\)C)** & **Overall \(s\)** \\ \hline Water & 65 & 4.184 & \\ Sawdust & 15 & 1.4 \({}^{\text{b}}\) & 3.1336 \\ Mature compost & 20 & 1.02 \({}^{\text{a,b}}\) & \\ \hline \hline \end{tabular} \({}^{\text{a}}\)\(s\) for soil compost blend, \({}^{\text{b}}\) Values from [39].  
\end{table} 
Table 2: Estimated material composition and overall specific heat for the food waste compost. Figure 5: 2D temperature contour plots of the compost pile at different incubation days. The heat produced on an hourly basis was 1659 kJ/hr. This was similar to the values of the small-scale composting systems reported by previous studies. Table 4 shows the heat production rates from the different composting scale sizes. The heat production rates increased with the increasing scale of the compost system. Besides the operational design and conditions, the amount of heat that can be produced would depend on the scale of the compost facility [25]. This study investigated the optimal initial moisture content and seeding amount required for an effective composting. An attempt was also made to estimate the heat produced during the 30-day composting process. The study showed that the heat produced from composting can be a potential bioenergy source that can find a number of applications, including absorption refrigeration, organic Rankine cycles, and liquid-to-air heat exchangers. However, before this can be accomplished, further investigations on the heat production, capture, and application should be evaluated for different composting scales. To accurately measure the heat production, factors including the operational conditions, heat losses, and operational design should be considered. A cost-benefit analysis can also be performed to provide a comprehensive conclusion on the bioenergy potential of food waste composting. Conceptualization, C.K.Y. and C.L. ; methodology, C.K.Y. and H.C.S. ; validation, C.L., and N.K.C. ; formal analysis, C.K.Y. ; investigation, C.L.W. ; resources, C.L. ; data curation, C.K.Y., H.C.S. and C.L.W. ; writing--original draft preparation, C.K.Y. and M.E.C.