Energy from Waste : Power and Gas

In my continuing study into the relationship between gas and electricity, I very nicely asked if I could join a tour of the most local waste-to-energy plant to my home, North London Waste Authority’s London Waste EcoPark in Edmonton. The site visit was arranged by the Green Ventures Trade Mission from Germany to the UK. There was room on the tour bus for a “lift home” from the networking event in the morning, at which I represented Herbert Eppel and his enterprise for German-English and English-German translators HE Translations, and after getting over a few initial communication misunderstandings, I was able to join the site visit. I was so glad I went. It was a wonderful afternoon.

Had I known I was destined to be climbing gantry staircases with an orange hard hat and hi-viz yellow jacket on, I would have definitely decided not to wear a fancy blouse and pearls. It was a pretty confused look. Fortunately, I was too old to be able to wear high heels, as that would have been impossible. Or nearly impossible. One of the other women on the site visit was wearing quite elegant and vertical footwear, and she managed just fine.

We saw the plant repair shop – the principle of re-use, reclaim, repair and recycle just right there in action.

As we got outside, the air took on a distinctive farmyard aroma, and most people put on their 3M face masks. I did too, and that really complemented my outfit to a tee. I now looked like some strange mix between a Samurai warrior, a sumo wrestler and a fencing expert.

We saw the post-combustion conveyor belt, and the piles of ash accumulating, and the metal – separated by magnets. The metal, our guide explained, would all be recycled, sold by the tonne. As we were there, a lorry from the neighbouring private company that uses ash to produce aggregate products for projects such as roadways and construction, came for a load of ash and went round to the weighbridge. He had to wipe the ash from his registration licence plate for the recording of his payload. Then he had to drive virtually the same way he had come to reach his plant next door.

We had an overview of some of the other facilities out at the back of the yard, although we didn’t see the anaerobic digestion sheds, where garden trimmings and household food waste gets made into soil that we get back at our local gardening centre.

Then we went to take a look inside the Energy Centre. I had a Toy Story 3 moment when I saw The Claw lifting great mountains of London’s rubbish from 20 metre deep bunkers into the hoppers feeding the 5 furnace/boilers. Everything was so big in there. I could see VHS tape streamers floating like gossamer spider silk in the wind.

Several claws like giant spiders were lying deactivated at the tops of the concrete bunkers in this massive waste hangar.

Our tour guide explained that the EcoPark can no longer accept commercial wastes, but that when it did, security guards would watch while illegal drugs, money, cigarettes and other crime-related materials would be fed into the furnace hoppers to make sure it all got burned. There were bedsheets in the hoppers, but we were told that mattresses were not allowed as they could ruin equipment.

On one of the platforms there was some electrical equipment that looked straight out of a horror movie, with dials and levers and switches and spider webs that had probably been there since 1975. “Don’t touch that”, said one of the tour party, when I pointed it out, “it’s structural”.

We passed into the bunker room, and there was so much scaffolding around the boilers that you couldn’t really see their shape. The hall was full of gentle radiant heat. It properly glowed.

As we walked down to see the turbine hall, I steadied myself on a handrail that was covered in really sticky carbon dust, that ended up sticking to me. We were, as I thought, waste deep.

The turbine hall was electric. No, really. The whole place was vibrating, and the air was pulsating with static and traces of carbon dust. Five huge red engines, and one man with a clipboard. The real business of management was in the Control Room, so that’s where we went next.

Another door alarm went off as we went through to there. Machines and computers and displays mixed with wooden desks and potted plants. And air conditioning. A sign above the instantaneous emissions monitoring screen with the current limits for gas emissions printed in bold letters. Videocams of the fires in the furnaces. And readouts of the various problem gases that needed to be kept within limits : sulfur dioxide (SO2), hydrochloric acid vapour (HCl), carbon monoxide (CO) and so on.

One of the engineers gave us a technical overview of the energy plant. He explained that the temperatures inside the boilers get up to around 850 degrees C. He explained that there is a ramp, and that material coming out by the time you get to the fifth furnace, is just ash. He explained that during the first heat exchange to make steam, the temperatures get up to around 450 degrees C, and that then this steam goes on to be superheated for the electricity generation turbines. For Flue Gas Treatment (FGT), he explained how the “wrapper” takes out particulates, and about the various reactors and additives that clean the output gases. Steam is emitted, as well, but this is clean.

He said that they can get up to 12 megawatts (MW) of generation, and that some is used for the EcoPark, but they also feed the National Grid. He explained that they need to be producing power constantly. “So you’re on 24/7 ?” asked somebody. “Not me personally”, said one of the engineers. They both used to work in coal-fired power stations.

I asked about carbon monoxide, because I know that at the high temperatures of the boilers, a lot of syngas will be produced – a mixture of hydrogen and carbon monoxide – during the combustion. The carbon monoxide emissions reading for the fifth boiler was quite high. I asked what their emergency strategy was if carbon monoxide levels went too high and they had too many excedences of the regulatory limits. He explained that in that case, they moved all the solid material out of the furnace, as it was much easier to deal with the gases on their own.

On our way out I explained that I had seen some of the air filtration equipment that was in a looped tube arrangement, and I asked if the plant recycled flue gas. I was told it did not.

London Waste’s Chairman and Non-Executive Director David Sargent shook my hand several times during the afternoon, even though I explained I didn’t have anything to do with the trade mission management. I told him I lived 5 kilometres away in Waltham Forest, and pointed in the general direction. He told me I probably get some of his electricity. And I told him he probably gets some of mine, as I am a generator too. He asked if he could have a site visit to see my solar panels. I said I could show him my composter, too.

As the tour bus got onto the A406 North Circular road, I saw that the old gasholders in the Lee Valley are being dismantled. From the road you can still see the lift canopy of one of them, in the centre, deflated on the ground. Later, I noticed that the old gasholder frame at Brent Cross is badly rusting, and because it’s so close to the road, it too will probably be removed. It will be such a shame to lose these distinctive pieces of London’s gas history.

In the sky above I saw a sort of rainbow between clouds.

Then I saw a rubbish clearance van marked with “JunkAndDisorderly.com”.

Waste not, want not.

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