Household solutions

With the European Union’s Landfill Directive targets for 2020 fast approaching, local authorities in the United Kingdom are finding it necessary to devise innovative ways to deal with household wastes.

This is the situation in Milton Keynes, where its council has taken the groundbreaking decision to implement not one but three separate waste management systems under one roof at a brand new facility, the Milton Keynes Waste Recovery Park.

Milton Keynes currently has a no-mass-burn policy but has also committed to reducing its current landfill percentage to less than 5% by 2019/2020. In a move that will showcase the first facility of its kind, the new Milton Keynes Waste Recovery Park incorporates mechanical treatment (MT), advanced thermal treatment (ATT) and anaerobic digestion (AD) in one site.

The town already enjoys considerable recycling success. The percentage of household waste being recycled in the area stands at 53.5% (2012/13), well above the U.K. average of 42% for the same period. However, the Milton Keynes Waste Recovery Park is an important component in Milton Keynes Council delivering on its ambitious goal of achieving a 70% recycling rate by 2024/25. To achieve this, the new facility, which is positioned as a waste treatment plant as opposed to a recycling plant, will treat 132,000 tonnes of residual municipal waste collected in the area each year.
 

Winning combination

Once inside the facility, any recyclable materials not yet removed will be mechanically separated before the waste moves on to either ATT or AD treatment. By combining these three methods, the new plant will contribute to the local authority delivering effectively on both its “no burn” and its landfill reduction aims.

This is where Stadler UK—the U.K. arm of the Germany-based sorting and processing equipment supplier—comes in. Stadler UK was commissioned for the design and fabrication of the new MT plant by AmeyCespa, the Cambridge, U.K.-based firm responsible for the construction and operation of the facility.

Importantly, as well as recovering viable levels of resources from waste, the plant will significantly contribute to Milton Keynes meeting its targets to reduce waste sent to landfill to less than 5% by 2020. In addition, the ATT facility will produce enough electricity to power 11,000 homes, with the AD plant producing renewable energy and a compost-like product that will be used on brownfield sites around the region. Overall, Milton Keynes Council anticipates savings of what translates to $75 million against the cost of landfill over the life of the facility considering the current landfill cost of around $120 per metric ton.
 

Back to basics

While the new plant’s design is complex, Trevor Smart, U.K. sales manager for Stadler UK, says he believes the first steps in designing every sorting system is answering two basic but crucial questions. “We first need to ascertain what is coming into the plant, i.e., what is the composition of the feedstock, before moving on to then identifying what the plant operator wants the end product to be.”

Smart continues, “The primary consideration when designing this plant was taking into consideration that the MT process sits in between the other two processes and had to be flexible in order to be able to keep processing the waste if the ATT or AD processes are full or offline.”

Municipal waste deliveries do not stop if part of the system needs servicing, upgrading or repairing, notes Smart, and therefore the MT plant design has had to ensure it can cope with a number of operational possibilities. “In response, we have included additional equipment within our design to ensure the process is robust in order to fulfill the service delivery requirements of Amey Cespa to Milton Keynes Council,” he says.

Another significant challenge for the design is keeping the plant clean. As Smart explains, “If you imagine what the bottom of your household waste bin would look like if no refuse bags were used and your rubbish was just piled in, and then multiply this by the sheer volume of household waste that will be heading to the plant, then you have some idea of the challenge we faced in the design.”

In order to keep the plant as clean as possible, Stadler has incorporated a number of features, such as scrapers to clean the machinery and special chutes for getting rid of sludge.
 

An integrated approach

Stadler UK also had to meet the needs of companies involved in the project. It is contracted with AmeyCespa to deliver the sorting system. However, there also is the main building contractor and the process contractors for the AD and ATT plants—all of whom have their own inputs and opinions.

Stadler UK’s design at the new plant will see materials passed through trommels before going through ballistic separation. Once material has been mechanically sorted, it will be diverted to the appropriate treatment system, either AD or ATT. “The technology for AD is fairly robust, so from our point of view, it has straightforward requirements,” says Smart. “With regards to the ATT, the system is capable of operating with a wide range of materials but we still have to meet the fuel in-feed specification so it can operate to maximum efficiency.”

Work started at the Milton Keynes Waste Recovery Park early in 2014. The plant is due to be commissioned in early 2016, with extensive testing to take place before it becomes fully operational in September 2016.

“We are in the advanced stages of the development of this facility and it is an exciting project to be involved with,” Smart says. “This will be the first fully integrated waste treatment plant Stadler has been involved in and we look forward to progressing the installation and seeing it become fully operational in 2016.”

The article was submitted on behalf of Stadler UK, based in Bristol U.K., a subsidiary of Altshausen, Germany-based Stadler. For more information, contact Diane Kenny at diane.kenny@proteuspr.co.uk.