Equilibrium moisture isotherms for synthetic food waste and biosolids composts

Equilibrium moisture isotherms of compost mixtures and a bulking agent were determined to investigate the effect of substrate and extent of degradatio n on the equilibrium relationship between moisture content and relative hum idity. Data were found for composts consisting of synthetic food waste and biosolids using a closed loop, dynamic system. Isotherms were generated by regression analyses of the data using the Chung temperature independent equ ation. Mixtures that had been composted 20 to 30 days had similar isotherms to those for the raw materials, suggesting degradation did not significant ly alter the equilibrium relationships. Materials that contained a high fra ction of bulking agent followed the isotherm for the bulking agent well. Ma thematical analysis of the effect of temperature on the isotherms was perfo rmed using the Chung-Pfost equation. This analysis indicated that temperatu re Flayed a large role in isotherm behavior at very low moisture contents, yet had a small effect at moisture contents greater than 0.18 (g H2O/g wet weight).