Part 1: A waste newbie's week of site visits - key takeaways

Our Social Value and Sustainability Intern, Emily Nurse shares her key learnings from her week of visiting various SUEZ locations across the UK.

During October, I was given the opportunity to visit a number of SUEZ recycling and recovery UK waste management sites around the country. Having only been at SUEZ since September, it was a fantastic chance for me to get a behind the scenes look at what really happens to the waste we collect and process on behalf of our customers. Here I’ll give you a run through of what I found out about what happens to waste after it lands in the bin.

Visiting the SRF facility at Malpass Farm

The solid recovered fuel (SRF) facility at Malpass farm is easily identifiable as it sits beside the CEMEX Rugby Cement Plant, which features the largest cement kiln in the UK – I must say, it made a great pointer for directions. The facility processes a mix of commercial black bag waste and transforms it into an alternative fuel, ‘Climafuel’. This is transported to our next-door-neighbour CEMEX, where the fuel is used to power the cement works, displacing coal and supporting with CO2 reduction. Before residual waste is processed into SRF, it is important to note that any recyclables are removed first, before the waste is thoroughly sorted, separated, and shredded.

So what was my biggest takeaway from the SRF process? Any material containing a high chlorine (PVC) or water content (organics), for example, must be removed, as this would negatively affect the cement-making process. To efficiently power the cement kilns, the calorific value (CV) of the waste being incinerated must be at a certain level. The CV of waste refers to the energy content of the waste, and therefore the amount of heat produced through its combustion. Those with a higher CV are more combustible and will produce more energy. Furthermore, an unbalanced amount of chemicals – from poor sourced or mismanaged waste doesn’t simply hinder the cement-making process but can also have an adverse effect on the environment, making the stability of chemicals within the fuel that we provide for CEMEX crucial. So, the SRF facility does more than simply process waste: recyclable material is extracted that may have otherwise been lost, it lowers CEMEX’s use of fossil fuels by providing Climafuel and diverts waste from landfill – it’s a win-win-win situation!

Visiting the MRF and SRF in Birmingham

Nestled within the centre of Birmingham, Landor Street’s material recycling facility (MRF) and SRF plant is an impressive urban waste site. Landor Street’s MRF showcased just how technical waste processing can be through various forms of automation, and highlighted the criticality of materials quality throughout the site and the different stages of sorting. First, from the point of waste receipt, in this case mixed recycling such as paper, card, plastic, metal, and glass enters into a trommel, consisting of three different sized areas. This sorts the waste into three groups. Next, some of this waste is taken to a heavy light separator, where the items with very similar weight and sizing are graded. Air is pushed through into the deck resulting in the light fraction to rise above the heavy fraction – as a result, the heavier items move uphill, and the lighter ones go downhill. The waste continues to follow through numerous other automated processes depending upon its composition, going through a ballistic separator, past ferrous magnets, over an eddy current, and optical sorters – to name a few.

Residual waste that you’ve sorted at home doesn’t simply arrive at a MRF via a collection vehicle, to be shipped off elsewhere ‘as is’. It is a highly complex system, and I have just lightly scratched the surface. Not only is the process technical, but ‘pickers’ who man particular areas of the conveyor belt are essential for quality control. Every single bale of sorted material is also checked by someone for quality before they leave the site, ensuring that customers will be happy with the material they receive, and that contamination levels are as low as possible. On that note, remember to wash out your plastic pasta sauce pots before you put them in the recycling – they can’t recycle it otherwise, and you’ll contaminate everything around it, particularly if it leaks onto the paper and card!

Visiting Surrey’s Eco Park

Situated in picturesque Surrey, SUEZ’s Eco Park in Shepperton was a welcome addition to my tour as this is one of the newest facilities in the SUEZ portfolio. In 1999, SUEZ was awarded a 25-year contract by Surrey County Council to manage the disposal of residents’ recycling and municipal waste. SUEZ and Surrey County Council have a strong partnership in working to divert waste from landfill, raise recycling levels, and to process waste in the most sustainable manner. The Eco Park consists of several facilities: a gasifier (SUEZ’ first) which produces power for the national grid, an anaerobic digestor (AD) used to create fertiliser, a recycling bulking facility (a bit like a transfer station), a community recycling centre (CRC), and a Reuse shop, giving intact items about to be thrown away an extended life.

Let’s talk about the gasifier, which has the ability to transform the 55,000 tonnes of residual (or black bag) waste collected into enough energy to power 8,000 homes. Before gasification, the waste is initially sorted by size, shape, and composition, before being shredded to produce a refuse derived fuel (RDF). The sorting of waste is crucial at this stage, as this is where materials unsuitable for gasification, such as metal, are removed. The RDF then enters the gasifier – where temperatures may reach above 700 degrees – resulting in a syngas being produced. The gas rises up into the top of the unit, and air is added – this is fired, again at a very high temperature, producing energy. Heat generated through burning the syngas is used to heat water to create steam, driving a turbine and electrical generator, and producing energy to power the homes of Surrey.

The AD facility was particularly interesting – food waste can produce a biogas used to generate electricity, and can also produce an organic compost for farmers to use. However, the most eye-opening thing that I learnt was that compostable food bags (or ‘starch’ bags) are in fact a massive hindrance to the AD process. This is because an anaerobic digester functions without air and in the dark – the opposite of the conditions needed for a starch bag to break down – meaning they have to be removed. Yet, the removal of these bags is a challenge in itself, as due to the warm conditions of the AD, they take on an almost glutinous-type quality. But before you panic and decide to stop using compostable food bags – check how your area processes it. If your food waste is taken for in-vessel composting, the starch bag is able to be completely composted depending on the facility.

Visiting Severnside energy recovery centre (SERC)

Of course I saved the best until last. The Severnside energy recovery centre in Avonmouth is a huge energy from waste (EfW) facility. The energy output that Severnside produces from treating 400,000 tonnes of residual waste every year that would have otherwise gone to landfill is immense.

The EfW facility has a contract up until 2041 with the West London Waste Authority, covering six London boroughs, with a total population of 1.7 million. The purpose of Severnside is to recover energy from black bin waste, reducing reliance on landfill, and as a result, 96% of West London’s residual waste is diverted. The waste principally arrives by rail – six trains arrive to the facility every week, each with approximately 1,100 tonnes on board, therefore avoiding the emissions associated with road transport. The output from the SERC is an export of 37MW – enough to power 60,000 homes. In essence, the waste goes through a combustion process, and the outcome is energy, which perhaps appears straightforward. Yet, it was made very clear at the SERC that the quality of the waste brought in can be challenging. The waste should be ‘black bag waste’ but often includes lots of material that could have been recycled, like paper and cardboard. In addition, striking the correct balance between incinerating waste that has a high calorific value or low calorific value is essential, in order to generate a sufficient amount of electricity, but also in consideration of the environment. Not every product with a high CV is always safe to go through the combustion process, and equally, it may not always produce a high amount of energy. As by-products of the EfW process, any metal is recycled, and bottom ash produced by the incinerator is sent to Blue Phoenix, who provide a sustainable solution to handling the ash residue, using it within cement.

End of week reflection

There is so much value in the waste we throw away if we can capture it appropriately. As a society we must think more about our own consumption patterns, and the impact that our waste has on the planet.