(220t) Taking Into Account Transport Parameter Evolutions in Composting Process to Improve Energy Consumption

Composting process refers to a biological treatment of wastes thanks to the oxygen conveyed by the flow, humidity within the sludge and temperature increase due to biological activity.

There is a strong coupling existing between transport processes and biological reactions and this generates also a compaction process of the solid porous matrix.

This talk will be dedicated to the understanding of the compaction effects on the whole process. This compaction comes from the initial rearrangement (in the first hours) of the porous medium. Due to biodegradation reactions and drying, some pieces of the porous matrix are decomposed in smaller parts and a second slow compaction process appears (from the second day to the end of the aeration process). It is then necessary to characterize those effects during these two periods.

A coupled experimental and numerical macroscale approach (Darcy's scale) has been followed. We have obtained a data bank for effective transport parameters but also mass balances. Then, we have make use of those relations using our numerical tool and compare the numerical results to the experimental ones.

This shows a good agreement and allows us to propose new developments in order to improve the efficiency of the industrial process. Some perspectives of aeration limitations will be given in order to reduce the consumption cost of energy.