How We Recover Energy From Waste
What does MBT/AD mean?
It stands for Mechanical Biological Treatment with Anaerobic Digestion – sounds complicated! Well it’s not. It’s where ‘residual waste’ waste you don’t put in your recycling bin is processed to make sure it’s used as a resource.
Across Greater Manchester we send all of your residual waste to one of our five MBT facilities to separate and treat residual waste to generate end products and electricity.
There are two stages to MBT:
The residual waste is separated by screens, shredded using cutters and sorted into size – what we call ‘fractions.’ Then it is sent through a number of conveyor belts where screen machines remove iron based metals with a magnet and other metals with an Eddy Current separator which are all sent for recycling.
A trommel which is a large cylindrical drum acts like a sieve separating large and small factions of the waste.
The smaller fraction of rubbish is mainly organic and this moves onto the Anaerobic Digestion part of the process. Water is added and specialised machines separate the rubbish even further.
Light items like small bits of non-recyclable plastic, paper, card and textiles will float to the surface and are skimmed off.
What’s left is called ‘slurry’ which is pumped into an enclosed tank which contains water and bacteria. The slurry will stay in the tank for up to 25 days and the bacterial action taking place creates methane which we call ‘bio-gas’ which is used to fuel engines to generate electricity.
The waste material left over from the AD tanks is dewatered and dried and then it’s sent to either our Combined Heat and Power plant to be used as fuel, or refined to be used as a compost-like product.