We’re standing in what look, at first glance, like a rural farm yard – barns, mud, idyllic countryside setting; the distant clanking of heavy machinery. We loiter, Londoners in the Cambridgeshire countryside, in high-vis jackets and wellies. The affable Dan waits for quiet as a huge truck rumbles through to be weighed on a drive on scales: this is not a normal farm yard – this is the UK’s largest household compost processing facility. The Envar facility in St Ives, near Huntingdon, processes tonnes of waste a year – turning food scraps and garden trimmings into rich soil improver.
Compostable waste comes from all over London and the South East, sometimes further afield when other sites run out of capacity. It’s fed through tunnels, turned over and over, sieved and filtered – but first its weighed then dumped in a large holding bay so that contaminants can be removed. Some people take ‘garden waste’ very literally – as anything they don’t want which happens to be in the garden. Dan tells us they’ve had broken plastic chairs turn up – but more common are plastic bags and excessively large branches. On the doorstep, a woman voiced her surprise when the compost collection folk rejected her bin, which she’d filled with an old carpet. “I don’t understand” she said “It’d been in the garden for years. Why wouldn’t they take it?”. Although unwilling to divulge damning details, Dan says some places have much better quality waste than others – the people of Bexley can be proud that theirs is of an excellent standard.
After large and obvious contaminants have been removed, waste is minced up a bit to make it more manageable and enters the first area – the aerobic digester. This part of the plant is undeniably stinky – though very little of the stench escapes the building (more on this later). Sitting in a series of tunnels at around 60 degrees, air is blown through organic matter allowing bacteria to break it down and render it harmless. It’s regularly probed to make sure that any nasties will be broken down – and then moved on to the next stage. To witness this, we have to walk through an extremely pungent corridor, up a stinking staircase, and cross a repugnant room – and out on to the relative freshness of the roof, bathed in fresh Cambridgeshire breezes.
From the roof, Dan talks us through the rest of the process. A large concreted area lies in front of us, with rows and rows and rows of steaming brown piles of muck which are being turned by a pair of diggers, which ensures everything is broken down evenly. Because of the amount of heat that the breakdown of organic matter creates, smoke appears to rise from the piles – and they have to be watered at this time of year, because the bacteria involved like a nice moist environment. It also prevents overheating and the possibility of fires!
From the roof, we can also see the series of sorting machines the matter travels through after waiting for weeks outside. It’s sieved and graded then heaped up under a barn in neat piles. As we leave the roof, Dan shows us what looks like piles of driftwood. It’s in fact a clever biological filtration system. Micro fauna shelter here – air from the digestion tunnels is pumped through and the resident bacteria munch on the fumes, clearing them up – well, if not entirely, enough that they barely pong.
Before we leave, we go in for a closer look at the finished product. Dan shows us the tag which is used to mark each batch all the way through the process. By time it ends up under this barn, next to where we entered the site, all that’s left is a rich soil improver : all nastiness and stench has left the material. Well – almost all nastiness has been removed… our eagle eyed boss, Steve, spots a 1-direction earring in the pile we’re inspecting!