I’ll get the jokes out of the way at the beginning. I was concerned that today’s trip would be a load of rubbish and a waste of time. There, now we can move on.
Our u3a Out and About group had considered a trip to a waste centre in Oxfordshire but trips around there were only for residents. The one in Buckinghamshire wasn’t so picky but was too far for the u3a to travel so I went solo.
Greatmoor EFW is a situated halfway between Bicester and Aylesbury but really feels like it’s in the middle of nowhere. Particularly after you turn off the main road and head along the three-mile single-track road to it. This is no ordinary single-track road though as it is straight as a die and has regular passing places, which is just as well as it is busy with lorries for both Greatmoor and HS2, which is being constructed next door.
EfW?
Greatmoor is an Energy from Waste (EfW) facility – it takes any residual household waste that has been collected, burns it and turns that into electricity. By residual they mean anything that is left after you have separated your recycling and food waste.
Built ten years ago by FCC for Bucks Council at a cost of £180M, there is a 30-year contract during which Bucks can bring up to 100,000 tonnes of waste for processing for “free” (i.e. included in the contract). They can send more, but beyond that, they have to pay, but at a rate less than the “gate price” (i.e. less than it would cost for others to deposit there or at landfill). However, the capacity of the site is 300,000 tonnes a year so there is quite a bit of headroom to take in waste for processing from other areas. And if you want to know how they know how much has been sent the lorries are weighed on the way in and then again on the way out with the difference being the amount of waste deposited.
From Waste to Electricity
The tour itself took us right through the process from start to finish. We began in the control room where we could look out onto the cavernous hole below where the lorries come to deposit their loads. A massive claw, capable of grabbing six tonnes, then lifts the waste up and into a grate. The job is not just lifting and moving waste as they also need to be on the lookout for things that shouldn’t be in the waste such as batteries and mattresses.
Next were the furnaces, which run at 850°C. We were encouraged to put our hands on the furnace door, which was warm to the touch but not hot, showing how good the insulation must be. There was also a small window through which you could see the fire burning the waste. During this, there is obviously a lot of heat generated. At the moment, this heat is wasted, but it could in future be used for district heating projects, but that seems unlikely given its location.
The heat is, however, used to create steam to a temperature of 400oc which is then injected into a turbine at a pressure of 60 bar. Given that the tyres on my car are inflated to a measly 2.3 bar that’s an awful lot of pressure. Four turbines are turned and then sent via a gearbox to a magic box which turns it into electricity. I’m fudging it here but it involves something to do with magnets!
The plant generates about 30MW of electricity of which the plant uses 3MW to run, what they call the parasitic load. For comparison the output is 10,000 times more than the output from my solar panels at home. 30MW is about enough to power 60,000 homes.
Environmental Concerns
EfW plants are definitely a good news/bad news thing.
The good news is that Greatmoor is preventing 900 tonnes a day of residual waste from ending up in land fill. Also the output from the plant, other than electricity, is minimal – there is vapour which is 99% water and ash which is used to create kerb stones.
The bad news is that EfW needs water, a lot of water and given that while I am writing this we are in the middle of a drought and have a hose pipe ban that feels a bit off. However, EfW’s are classed as “critical infrastructure” and so can continue to take what water they need while the rest of us cut back.
I’m not a great fan of landfill and all the problems that come with it so the EfW water usage is a trade-off I’m willing to accept. Of course, it would be even better if we all recycled more and they found a way of recycling the water but until then this will have to do.
