Process optimization tunnel composting

At the Composting and Digestion (C&V) Department, we process about 100,000 tons of organic waste and about 15,000 tons of other organic waste streams into compost, biofuel, electricity and heat each year.

In late May 2019, a fire occurred in which the pre- and post-processing area of the composting plant went up in flames, in June 2021 the new pre- and post-processing area was put into operation. In the current situation, the delivered GFT in pre-processing is screened into three fractions, namely 0-13, 13-60 and 60-200mm. The 13-60mm fraction goes to the GFT digester (dry digester), the 60-200mm fraction goes together with the 0-13mm fraction and the digestate from the digester directly to the 20 composting tunnels.

The composting process is an aerobic process, the process air blown in through the tunnel floor provides the oxygen required for aerobic decomposition and the removal of water, which also dries the composting material. After a residence time of approximately 10 days in the tunnels, the composted material is screened in two stages in post-processing to produce a fraction <10mm (keurcompost quality class a) and a fraction>10mm which is processed as biofuel in Twence’s biomass power plant (the BEC). The remaining residues are sold to external end processors.

Problem Statement:
Can you help us with the following? With the current operation of the tunnels it appears that insufficient evaporation is taking place among other things due to the addition of wet digestate that contains very little energy, this results in tunnel material that is too wet resulting in insufficient screening efficiency (compost/biofuel ratio).

This project contributes to the following Sustainable Development Goals (SDGs):