Applying Compost Biochar for Gas Adsorption-Effects of Pyrolysis Conditions

Not all produced compost meets established quality standards, often resulting in environmental challenges. This study investigated the potential of using mature compost as a feedstock for biochar production, with a focus on evaluating the gas adsorption properties of the resulting biochars. Mature compost was utilized as a substrate, and the pyrolysis process involved heating samples within a temperature range of 400-650 °C, at 50 °C intervals, with heating rates of 10 °C·min^-1, 15 °C·min^-1, or 20 °C·min^-1 for a duration of 60 min. The resulting biochars were tested for their adsorption performance against a synthetic gas mixture simulating composting emissions (CO₂, CO, H₂S, NH₃, CH₄ in N₂). Our findings reveal a significant correlation between the pyrolysis temperature and the sorption characteristics of compost biochars. Specifically, biochars produced at temperatures of 550 °C, 600 °C, and 650 °C (with a heating rate of 10 °C·min^-1) demonstrated the highest efficacy in reducing emissions of CO₂, CH₄, and H₂S, achieving reductions of 69%, 69%, and 72%, respectively. However, these biochars exhibited lower adsorption capacity for CO and NH₃. Interestingly, biochars produced at 400 °C and 450 °C showed enhanced performance for CO adsorption. Compost biochar shows strong potential for gas adsorption, particularly for CO, CO₂, and H₂S. Due to its pronounced CH₄ sorption capacity, such biochar is better suited for mitigating emissions during composting rather than for biogas purification.