The grit particles can cause issues by settling in the bottom of the digestion tank, reducing the efficiency of the system and potentially causing damage to equipment.
Currently, a number of biogas plants are Continuously Stirred Tank Reactor (CSTR) type AD plants. When first commissioned most were built without pre-treatment to remove unwanted materials. To deal with this, digestate tanks will need to be emptied and cleaned before material compacts and solidifies.
These materials will not compost under regular conditions, making responsible disposal difficult.
Envar composts the grit, in a mix along with food and green waste, through our in-vessel composting (IVC) technology before being arranged into open windrows. After 6-8 weeks the material is ready for screening and sorting to remove any inorganic materials. The result is peat free high-quality PAS 100 Soil Improver.