Carbon Dioxide Recovery from Composting

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Composting is an established waste management option that diverts organic waste from city landfills, stabilizesit and recycles the residue for agriculture. Typically, composting is an outdoor process where the organicmaterial is stockpiled in windrows (long piles) that can be turned periodically to enhance biological activity.The biological activity is enhanced by ensuring adequate oxygen for the microbes, that is moving material frominside the pile to the surface. The biological activity converts a portion of the organic matter to carbon dioxideand water thus releasing heat. These gases, and heat, are vented to the atmosphere with normal compostingproducing carbon dioxide concentrations of about 6% by volume. Carbon dioxide is a valuable industrial gasand will soon be valued through the national carbon plan yet to be unveiled. The coming price on carbon therewill be added costs to consumers of industrial CO2, which is normally sourced from refineries or otherconcentrated, fossil fuel based, sources.We will be investigating a closed system that allows for capturing of the CO2 produced by the compostingprocess while potentially increasing the biological activity rate. The main focus of the project will be toincrease the CO2 concentration in the compost exhaust, capture the exhaust to facilitate the separation processand increase the oxygen availability to the bacteria. This will be accomplished by testing several redesigns ofthe composting process including increasing the air flow, blending exhaust air with fresh air (raising CO2levels), using produced oxygen (e.g. from air separation either pure or blended) and moving the compost on amoving grate system. The performance improvement of these methods will be converted into a cost per tonneof CO2 captured where possible.