Effect of Temperature, Aeration, and Moisture on CO ₂ Formation in Bench-Scale, Continuously Thermophilic Composting of Solid Waste

Abstract

A compost production system was employed to supply uniform material for controlled experiments of factorial design. Over a 96-h composting period, the cumulative amount of CO2 evolved was maximal at 56 to 60°C, an aeration rate that left an 02 residual of 10 or 18% in the exhaust gas and a moisture content of 60% wet weight. Carbon dioxide evolution was submaximal at 64°C and higher.

Effects of Oxygen on Aerobic Solid-State Biodegradation Kinetics

“…It is important to note that the selection of 21% O 2 as the saturation value is somewhat arbitrary, as saturation could occur at lower (or higher) oxygen concentrations and there is little experimental evidence to use as a guide. Suler and Finstein's results did indicate a modest increase in degradation rate between 10% and 18% O 2 (20), which is consistent with this choice. There is an additional justification for this value when the model is used as a correction factor as indicated in eq 1, since ambient oxygen levels (20.9%) represent the highest concentration possible in most composting systems.…”

Characterization of a Bench‐Scale System for Studying the Biodegradation of Organic Solid Wastes

“…The optimal moisture content varies with the ability of the feed stock to hold water (Bach et al, 1984). For municipal sewage sludge, the optimal moisture content ranges from 50 to 60% (Suler and Finstein, 1977;Bach et al, 19841, while for yard wastes feed materials it is in the range of 65-70%. Microbial activity is t Department of Chemical Engineering.…”

“…The role of water in microbial activity was extended further by Miller (1989) with the introduction of matric water potential as a measure of the degree to which water is held in small pores on the surface of particles. 0 2 concentration is another important parameter affecting the process (Golueke, 1972;Suler and Finstein, 1977;Haug, 1980;Miller et al, 1991;Nakasaki et al, 1992;Miller, 1993). Predominantly aerobic conditions accelerate the degradation rate of most organic materials (Nakasaki et al, 1992).…”

“…Predominantly aerobic conditions accelerate the degradation rate of most organic materials (Nakasaki et al, 1992). Suler and Finstein (1977) reported that the 0 2 concentration in the exit gas needs to be a t least within the range of 10-18% to prevent a decrease in metabolic activity based on C02 evolution. A recent model by Hamelers (1993) suggests that only the outer shell, equivalent to 40% of the typical compost particle, is aerobic even under "completely aerobic" conditions.…”

“…Ashbolt and Line (1982) classified laboratory scale vessels into rotating drums and stationary cylinders. Several studies have addressed the performance of each type of vessels (Schulze, 1962;Jeris and Regan, 1973;Suler and Finstein, 1977;Ashbolt and Line, 1982;Sikora et al, 1983;Nakasaki et al, 1985;Hogan et al, 1989;Palmisano et al, 1993). Bach et al (1984) combined the advantages of these two types of vessels and used a mixed isothermal reactor.…”