Temperature, Pressure and Air Flow Distribution In Passively Aerated Compost Piles

Abstract

Distributions of air temperature and pressure across a cross section of a full-scale passively aerated compost pile were measured as a function of time over an 11 day long period covering two pile turnings. The compost pile 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 temperature and pressure data were used in combination with additional measurements of air permeability in the compost pile to calculate air fluxes in and out of the pile as well as internally in the pile. Temperature distributions were generally constant with time while pressure and air flux had greater variability. The results suggested that steady state conditions in the compost between turnings with respect to air flow are not necessarily achieved. Air flow rates in or out of the compost pile were up to 50 Nm³m⁻²h⁻¹ and the average passive air supply to the compost pile over the experimental period was on the order of 4 m³m⁻³ compost h⁻¹.