The Degree of Aerobiosis in Composting Process Control: Effect of Selective Composting Ecology Parameters on the Respiratory Quotient
Author: M. Klauß
Abstract
The respiratory quotient (RQ) is known to be different under aerobic than under anaerobic conditions. It may thus be a lumped parameter for measuring the overall effect of the various relevant factors influencing matrix aerobiosis.
An investigation was made to examine the influence of the environmental parameters of moisture content, temperature and oxygen level on the respiratory quotient during a certain time span.
To realise the studies an experimental, computer-controlled system was developed and constructed with featuring eight stainless steel vessels each with a capacity of approximately 18 litres. Several sets of tests, each one concerning one of the three main environmental parameters, were carried out. Used material originated from a composting plant and was adjusted to desired conditions in the laboratory. Forced and pre-conditioned air was used for aeration. Exhaust gases from the reactors were analysed for oxygen and carbon dioxide concentrations. These values and the values of the temperature measurement were transferred automatically to the PC. Respiratory quotients, oxygen uptake and carbon dioxide evolution rates were calculated automatically by computer. Oxygen consumption and carbon dioxide evolution rates fluctuated considerably depending on the air supply. Highest rates were achieved during the first day of processing followed by a decrease.
Additional parameters like pH and volatile solids were determined.
From general data on respiratory quotients it could be stated that the RQ time course showed a certain similarity in all trials; greater or close to one the first hours of processing followed by a decrease to values smaller than one.
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