Oxygen and Carbon Dioxide Distribution And Movement in Passively Aerated Compost Piles

Abstract

Distributions of O2 and CO2 concentrations across a cross section of a full-scale passively aerated, mechanically turned, compost piles were measured as a function of time over an 11 day long period covering two pile turnings. The compost pile had a triangular cross section, was 1.8 m high, 4.4 m wide, 80 m long and consisted of sewage sludge, yard/park waste and screening residue from previously composted materials. The measurements were conducted in one cross section of the pile. The O2 and CO2 concentration measurements were used in combination with earlier published measurements of air permeability and air pressure inside the compost pile to calculate O2 and CO2 fluxes across the pile surface as functions of time and location as well as estimation of total specific oxygen consumption rates in the compost. Distributions of O2 and CO2 concentrations inside the pile were relatively constant with time and exhibited high O2 concentrations near the surface and high CO2 concentrations near the center of the pile. Maximum O2 fluxes in the compost occurred along the lower edges of the pile and equalled up to 15 kg/m−2 h−1 while maximum CO2 fluxes occurred at the center top of the pile and equalled up to 700 g m−2 h−1. Average daily CO2 emissions from the compost were up to 3.4 kg m3 d−1 while the corresponding O2 flux into the compost pile was up to 53 kg m3 d−1. Average O2 consumption was 1.4 kg m−3 d−1 while average CO2 production was 1.5 kg m−3 d−1 at the measurement location over the 11 day experimental period.