The platforms for composting make it possible to produce sludge with homogeneous, stabilized and generally hygienized quality. Accreditation is obtained in terms of “fertilizing matters and supports of culture” near the Ministry for Agriculture. It relates to very few rough sludge from sewage treatment plant because it is difficult to guarantee a homogeneity in product quality
INTEREST OF THE SLUDGE COMPOST
- To improve the capacity of the ground to retain the biogenic salts,
- To improve the water holding capacity (quantity of water available for the plants),
- To improve porosity of the ground for a better root development,
- To optimize the fertilization
Operation of a platform of composting
Upon arrival of the organic matters on the site (green wastes, sludge from sewage treatment plants,…), one person carries out their identification and allots a number of entry, he carries out a qualitative control (source, quantity, absence of products refused on the platform…) and a recycling of undesirable matters which can be present. Then these incoming matters are crushed and mixed. The loader will buid up the mixture of incoming matters in order to validate the proportions. The mixture makes it possible to make the swaths.
The swaths are then stored in ventilated racks equipped with the return line of the juices. One sensor is laid out in each swath in order to ensure a continuous temperature check and to certify that the hygienisation took place.
Information is sent to a PLC management system which regulates the air flow insufflated according to the evolution of the phases of the cycle of fermentation. The oxygen contribution in quantity necessary to the wanted moment, maintains for several days the substrate at temperatures minimum of 70°C. This phase of composting of several weeks, supplemented by 4 other weeks of mechanical turning of the swaths, ensures the perfect homogenisation of the products.
Lastly, the swafts will go through one phase of sieving, carried out using an interchangeable rotary sieving drum supplied with loader. Four meshs of sieving of 10,20,40 and 50 mm are used. This system ensures a separation of the last undesirable matters and coarse pieces of wood (these elements are called waste screenings). These screenings are crushed and mixed with the green wastes used for the production of the compost to come.
The compost is then stored on site during the phase of maturation (phase of stabilization of the product) characterized by a constant temperature, as well as an activity reduced as regards carbon dioxide release and oxygen uptake.