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Design-in quality

The UK waste management industry is shifting its focus from environmental and sanitary management to resource management and energy generation. But are collection methods and infrastructure keeping pace with this change?

Many of the UK’s older MRFs were designed for a different task than the one asked of them today. As a result, many are out of date or are operating inefficiently by today’s standards.

This obviously affects the intrinsic value of waste. Yet the industry remains caught in a debate about collection methods, and whether commingling accurately reflects the requirements of European legislation.

While the quality and quantity of recycled materials is a key issue, the debate should be more inclusive of waste infrastructure - and the education of consumers and manufacturing industries.

The key to success is ‘cradle-to-cradle’ thinking, which requires participation from all involved in the product life-cycle.

Ensuring the UK has adequately designed and efficient MRFs is paramount to guaranteeing we get the most out of our waste. No matter what the result of the judicial review into commingling - and we look forward to the clarity it will bring - we have to ensure that our MRFs can respond to a wide range of variables. These include waste composition and volumes; new resource recovery technologies; the markets for recyclables; and the legal framework at UK and EU level.

So how can we ensure that waste collection and infrastructure, especially MRFs, can cope with these variations and changes? It is possible to look to our continental neighbours for some answers.

In Flanders, for example, it has taken 10 years of public engagement and education to achieve 50% recovery of recyclables through separate collection of materials. The remaining 50% stays in the black bag to be turned into energy.

In Rotterdam, there is talk of withdrawing from separate collection of recyclables, particularly in high-rise areas where the socio-economic make-up of the population and relatively small living quarters negatively affects residents’ engagement in the scheme. Instead, the city may select dirty MRF or mechanical biological treatment (MBT) plants to recover recyclables from black bag waste, alongside the roll-out of food waste collections in less densely populated areas of the city.

What these experiences in Belgium and The Netherlands show is that the balance between what can be asked of the general public and what can be asked of a MRF is crucial, and that this balance is not constant.

MWH and HTP have worked on several projects in the UK and north-west Europe, either exclusively or in partnership with others, to develop and build efficient MRFs. These projects range from dirty MRFs that sort and treat black bag waste, such as Biffa’s Brookhurst Wood MBT facility in West Sussex, to plastics recovery facilities and dry recyclables processing plants.

A common experience is that actual waste inputs are rarely in line with the anticipated inputs that are used as the basis for plant and equipment design. As such, optimisation and adjustments are needed during commissioning of the plant and during its lifetime.

We have also concluded that state-of-the-art MRFs can efficiently process clean commingled dry recyclables in fully automated plants with minimal manual sorting. High purities and recovery rates can be achieved. When black bag waste is treated in a dirty MRF or, typically, in a MBT plant, the recovery rate is typically less, while meeting purity levels requires subsequent cleaning.

Many MBT plants focus on production of a refuse-derived fuel stream with less emphasis on materials recovery, which is typically limited to recovery of metals, paper, card, and plastic containers. The economics of clean and dirty MRFs are difficult to compare, since most clean MRFs have an annual capacity of between 30,000 and 50,000 tonnes while most dirty MRFs are in the 100,000 to 300,000-tonne range.

Trials demonstrate that it is key to keep wet organic waste separate from non-organic waste, paper and cardboard to ensure optimal recycling results. New MRF design needs to take into account how these facilities may be future-proofed to allow for additional equipment to be installed, facilities to be reconfigured and changing reprocessor requirements.

Has technology now advanced to the extent that we should take a fresh look at the waste hierarchy? Are we putting too much focus on investing in quality end recyclables? Should we be looking at sorting to improve energy derived from waste, focusing on high-quality solid recovered fuel, anaerobic digestion (AD) and biomass, as well as separation for recycling, so that the best overall environmental outcome can be achieved?

MRF design can ensure that we are able to separate waste for these purposes just as effectively as we can for recycling. It is an opportunity for us to change the way in which we think about waste as a sustainable energy resource.

There is no doubt that we need to look at MRF design, as well as waste collection, if we are to maximise the value of waste.

In fact, we will soon have no choice but to change: the MRF Code of Practice will mean that the industry has to do more to ensure high quality and low contamination levels of recycled materials.

The only way to meet these goals, irrespective of the result of the judicial review, is to ensure that our infrastructure can cope with the evolution of waste and resource management objectives.

Marcel Goemans of MWH and Martin Bender of HTP

Case study: Biffa’s Brookhurst Wood MBT facility

MWH provides project management and engineering support services for Biffa’s state-of-the-art Brookhurst Wood MBT facility in West Sussex. Part of a 25-year agreement between Biffa and West Sussex County Council to treat the county’s waste, the facility will treat up to 312,000 tonnes of waste a year, diverting recyclable and biodegradable material from landfill.

Two fuel streams will also be produced by the process: refuse-derived fuel (RDF) from the MBT facility and biogas from the adjacent anaerobic digestion facility. The biogas will power combined heat and power engines, producing up to 4.2MW of electricity and heat.

MWH and HTP reviewed the proposed design of the facility, and ensured that the latest lessons learned from similar plants in Europe were implemented. This included assessing the steps required to obtain higher quality RDF.

MWH also assessed the capability of the facility to handle different waste compositions in the future using its in-house dynamic waste flow modelling tool.

When completed in early 2013, the MBT facility will be one of the largest of its kind in Europe.

It will have the capacity to reduce waste going to landfill by 80%.

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