Zero liquid discharge – from slurry to pellets
Increasing livestock density globally is generating so much slurry that its nutrients cannot be spread on local farmland. Ground water contamination caused by over-fertilisation is lowering the acceptance of our agricultural structures and stricter laws have been passed recently, especially in Germany.
The problem becomes even more visible when considering all the storage volume and transport needed to move the slurry to nutrient-poor areas. Economic and ecological steps towards reducing the water content of slurry must be found, as the substance contains more than 90% water. In the Netherlands, it is not uncommon that slurry is transported to Ukraine, costing up to €40 per cubic metre during winter months.
In regions with lots of livestock, there are many biogas plants to digest the slurry with additional waste, generating gas, producing electricity and heat via a combined heat and power (CHP) plant.
Until now, there have been many installations where solids...