Energy recovery uncovered

By Mark Loubser, head of environmental services, intu Retail Services

There is sometimes a misconception that waste we can’t recycle is simply sent away to landfill or to be burnt at an incinerator, sending plumes of toxic smoke into the atmosphere. The reality, you’ll be pleased to know, is far more advanced, far more beneficial and far more controlled.

At intu, we’re pretty good at segregating, ensuring that just under 65% of the waste produced at our centre’s can be recycled. And we do a great job in making certain that none of our waste goes directly to landfill. But what happens to the rest?

65%

waste produced at our centre’s can be recycled

Having recently visited the South East London Combined Heating and Power facility (SELCHP), I got the opportunity of understanding a bit more about what typically happens to our waste and what the concept of “energy recovery” means. Whilst SELCHP itself does not process much of intu’s waste, it is representative of many of the facilities that do, both in the UK and in Europe.

The process is complex, technically advanced and extremely well regulated. But it’s actually quite simple. So here goes…

Firstly, waste from households and some commercial businesses is brought to site and dumped into a chute leading to a massive bunker, which holds up to 6,000 tonnes. Huge semi-automated cranes grab up to five tonnes at a time, mix all the waste together and then transfer it to a hopper which feeds the incineration grates that can burn almost 30 tonnes of rubbish per hour! The waste is incinerated at about 850 degrees Celsius and the heat energy is passed into boilers that produce steam. The steam then drives a turbine, which rotates a generator that produces electricity. This produces enough power for 48,000 homes. It’s incredible!

And what about all that toxic smoke? Well, a lime milk is sprayed onto the hot combusted gases, reacting with and removing any acids. The milk then falls as dry powder through the grates. The gases from the waste combustion then pass through a bag house that contains as many as 3,000 individual bag filters (like those in your vacuum cleaner!). Any nasty dusts are captured on the filter material and, along with the dry powder, are safely disposed of at a licensed hazardous treatment facility. The cleaned gases are emitted from the chimney stack where emission limits are strictly controlled and must be in line with stringent EU legislation and regulation. The performance of this is monitored 24 hours a day.

The residue from the incinerated rubbish is called bottom ash. Like the remnants of your cozy fire at home, the ash sometimes contains metals such as copper, aluminium and brass that are able to be recycled by a specialist plant. The remaining ash is then further processed to produce a high performance aggregate that can be used for road construction and other purposes.

So, along with the support of our retailers and customers, you can rest assured that our teams do all they can to make the best use of our rubbish. Our preference is always to reduce, re-use or recycle. But where this is no longer possible, hopefully you have a better idea of where our waste ends up. Who knows, you could be driving home on some of it tonight!