Gaseous carbon dioxide removal from composting of biomass and cotton textile waste

The carbon conversion efficiency of composting with food, yard, and cotton waste is analyzed herein. We demonstrate the ability of air-aerated and oxygen-aerated composting reactors to achieve carbon conversion efficiencies between 23 and 60 % and cotton mass degradation between 37 and 99 %. This carbon conversion efficiency is equivalent to removing 0.32 - 0.97 tonnes of CO₂ per tonne of dry biomass waste processed, which compares favorably to the carbon removal potential of anaerobic digestion (0.04 - 0.40 t-CO₂/t-biomass) and hydrothermal liquefaction (0.49 - 0.62 t-CO2/t-biomass), two BiCRS technologies renowned for their ability to process wet feedstocks. 12 million tonnes of textile waste are landfilled annually, and through composting 10.8 million tonnes of that waste (over 8 % of annual municipal solid waste in the U.S.) could be converted into gaseous CO₂ for capture and soil amendment. Samples containing cotton in the initial feedstock had on average a 1.2 % higher carbon conversion efficiency than those without cotton. Air-aerated reactors consistently generated CO₂ concentrations above 18 % while oxygen-aerated reactors generated CO₂ concentrations above 80 %, which can reduce the minimum work of CO₂ capture by 70 and 93 % relative to atmospheric CO₂ capture, respectively. Microbial diversity decreased throughout the composting process, but samples with cotton and without cotton had virtually the same number of amplicon sequence variants after a thirty-day composting trial.