LSE staff visited the Ecopark waste treatment plant in Edmonton, North London. Jon Emmett, LSE Sustainability Projects Officer, looks back at the sights, sounds, and smells of this enlightening trip.
LSE’s Sustainability Team, along with residences staff and green champions, went on a tour of London Waste’s Ecopark waste treatment centre last week. We wanted to see for ourselves what exactly happens when waste leaves your bin, and gets carried away to the fabled, usually unseen land of ‘recycling’ – where rubbish is processed into raw materials, composted, or burned to generate electricity.
Our tour guide, Wendy, summarised the history of the plant, and the waste streams they take. We had an interesting discussion about the nuanced considerations and trade-offs involved when deciding on optimum infrastructure options, local partnership arrangements, operating capacities, and more.
Then we were straight off to the energy-from-waste plant. Walking along a raised gantry, we looked down into the abyss of a row of 70 foot deep concrete hoppers, each containing mountains of household refuse from the seven boroughs served by the North London Waste Authority. The rubbish was grabbed by a giant claw that snatched up two tonnes with each swoop, and deposited onto the grate of the furnace, where it burns at 850°C. The scale and aesthetic of the scene was reminiscent of an epic sci-fi movie.
We moved onto the furnace control room, where we spoke to the engineers who monitor the burning waste, ensuring the process is kept in balance. Live displays of the emissions in the flue gas appeared on giant screens. The engineers have a variety of tricks up their sleeves to control the conditions inside the furnace. For example, if carbon monoxide levels are too high, it means the burn is incomplete due to too much moisture in the mix, so they turn up the heat using gas burners.
The remaining gaseous emissions are scrubbed using a three-stage filtration process. Dust particles are collected on giant electrostatic plates (like rubbing a balloon on your hair), and then knocked off into silos. (This ‘fly-ash’ is transported off site in sealed containers to industries that require alkaline-rich materials, including cement product trials.) The gas is then cooled with water, before lime and activated carbons are injected to neutralise acidity and absorb other pollutants. Last of all, a fine fabric mesh filters out remaining lime and dust. All that is left is water vapour – none of what we see leaving the chimney is smoke. (Annual emissions data is published on their website – hopefully this will go some way to alleviating public concerns over the potentially harmful by-products of incineration.)
We visited the ‘engine room’, which feels like walking through a tropical butterfly house, where steam superheated by the furnace drives turbines that generate electricity – enough to power 72,000 homes per year. Moving outside, we saw a mountain of ‘bottom ash’ – the remains of the incinerated waste. It gets sold for use in aggregates, and Ecopark ash has been used in the construction of the Olympics amongst other things. Nearby was huge pile of iron objects, picked out from the conveyor belt of bottom ash with a magnet, to be sold on for use in manufacturing other products. The mountain of charred white metal forms, some of them just discernible as the remnants of household objects – a bedspring; an oil can; even a shopping trolley – formed an eerie assemblage that could have been on display in the Tate Modern.
I noticed that the architecture is very blunt and ‘to the point’. I recently visited the Victorian sewage pumping station at Crossness in South-East London (not for work, I’m just that tragic), which abounds with brightly painted wrought-iron flowers set into railings, and where even industrial crank shafts are elegantly formed and decorated. This contrasted sharply with the uniform, corrugated iron structures of Ecopark, which served as an interesting reminder of how the social expectations of municipal infrastructure shift over time.
Our last stop on the tour was the compost tunnels. Long, high sheds are filled with such large volumes of green waste that it reaches around 60°C. The sheds are pressurised like an aircraft cabin to keep bad smells in, and the air filtered through bark chips to absorb the odours. After spending about six weeks moving through a succession of tunnels, the compost is ready for use in gardens and farms. According to a friendly passing compost engineer, the smell is seasonal, and with a slight time-delay: March compost smells of discarded Christmas trees, and May compost smells of grass cutting from March. Ecopark do a monthly compost giveaway, where local residents are invited to bring a shovel and help themselves from a 15 tonne heap of compost.
Ecopark isn’t content to rest on its laurels – it has big plans for future development. Designs are underway for a District Heating Network that will supply warmth to local homes and businesses with heat given off by the incinerator. There are even plans to develop amphibious vehicles that could transport materials from Ecopark to manufacturers along the canals. If this idea comes to fruition, I can imagine it actually making big changes to the way that industrial transport infrastructure as a whole operates in the capital – a really interesting opportunity to watch out for in the future.
All photos courtesy of London Waste Ltd, except group photo of LSE staff, by Neil Lawrence.