Northumbrian Water has an advanced anaerobic digestion facility at its base in Howden on Tyneside.
Anaerobic digestion is the process where microorganisms break down biodegradable material (in this case sewage sludge), because they don’t have oxygen.
By controlling the process, two useful products are obtained: biogas and residual digestate (a nutrient-rich fertiliser).
Biogas, which contains a mix of methane and carbon dioxide, can be used to produce electricity and heat, or it is purified for injection into the gas network.
Advanced Anaerobic Digestion (AAD) processes have been developed to add even greater performance to the digestion process, as well as reducing the overall mass of solids.
For sewage sludge, conventional anaerobic digestion will destroy 30 to 40% of the organics present, whereas advanced anaerobic digestion may achieve 60% or more.