Kinetics of Biotic and Abiotic CO Production during the Initial Phase of Biowaste Composting

Abstract

Knowledge of kinetic parameters of CO production during biowaste composting is significantly important for the prediction of its course and estimation of total gas quantity. This allows increasing the control of the process, to minimize its negative impact on the environment and to protect the occupational safety of employees exposed to CO in the biowaste composting plant. For the first time, a full study of the influence of temperature and biowaste sterilization on the kinetics of CO production is presented. The lab-scale experiments used a mixture of green waste, dairy cattle manure, and sawdust in two variants: sterilized and non-sterilized samples. The process was carried out in controlled temperature reactors with measuring the concentrations of CO, O2, and CO2 every 12 h.CO production and k value increased with temperature. However, higher CO production was observed in biotic conditions between 10~50 °C, suggesting the biotic CO formation and 1st-order kinetics. The abiotic (thermochemical) process was more efficiently generating CO above 50 °C, described with a 0-order kinetic model. Additionally, the rate constant (k) value of CO production under biotic conditions was increasing up to a temperature of 60 °C, above which a slight decrease in CO production rate was observed at 70 °C. The presented results are the basis for further studies focused on the feasibility of (1) the mitigation and (2) valorization of CO production during the biowaste biostabilization are warranted.

Modeling of CO Accumulation in the Headspace of the Bioreactor during Organic Waste Composting

“…The highest airflow level was obtained for the second, third, fourth, and sixth day of the process when the assumed temperature was maintained at~50 • C. From the ninth day of the process, when thermophilic conditions appeared (temperature close to 70 • C), the airflow required to remove CO dropped almost twice for each variant (1.7× lower values when comparing the aeration between the third and 12th day of the process). On the other hand, this information is in line with our previous article, which shows that the highest CO production is~50 • C [29].…”

“…As a result of the modeling, the level of the required aeration drops due to increasing of CO production constant rate k and connected CO concentration in the bioreactor's headspace from the eighth day of the process. It was influenced by the change of the process temperature from 56 to 67 • C between the seventh and eighth day; as it was observed during the own previous research, the k value of CO production increases at temperatures up to 60 • C, while it decreases at the process temperature close to 70 • C [29]. The recommendations of other researchers confirm the estimated aeration level during this period.…”

“…The experiments were performed in triplicates at 10,25,30,37,40,50,60, and 70 • C. The tests were carried out in 1 L reactors according to [28] at a constant setpoint temperature in the climatic chamber POL-EKO, model ST-3, WodzisławŚląski, Poland. A detailed description of the methodology used is provided elsewhere [29]. The kinetics data for CO production rates during composting of organic waste were also reported elsewhere [29].…”

“…A detailed description of the methodology used is provided elsewhere [29]. The kinetics data for CO production rates during composting of organic waste were also reported elsewhere [29]. [27], ** estimated using raw data in [29].…”

“…The kinetics data for CO production rates during composting of organic waste were also reported elsewhere [29]. [27], ** estimated using raw data in [29]. [27], ** estimated using raw data in [29].…”