Critical analysis of two respirometric methods for solid substrates based on continuous and semi-continuous aeration

In the sector of respirometry applied to solid waste many tools are available. Moreover, methods for assessing the oxygen consumption can be significantly different. In Italy the sector is characterized by the adoption of dynamic approaches that are preferred to the static ones. In this paper a comparison between the two respirometers more adopted in Italy is presented. The first one is the Costech respirometer, with continuous aeration and without temperature control. The second one is the AIR-nl respirometer, with temperature control and a semi-continuous aeration based on the principle of avoiding limiting conditions of oxygen. Results were obtained during an experimental research that involved on one hand the construction of an analytical model for evaluating the respirometric index (RI) for various substrates and on the other, the critical analysis of the obtained measurements. In this paper the relationship between the output of tests conducted in parallel with two different instruments on the same samples is analyzed. Some differences between the results of the measurements and obtainable parameters (RI24) are underlined. Considerations on reference moisture, temperature role, respirometric index calculation method allow understanding more in details the characteristics of the two methods.