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Advanced waste treatment technologies

Atkins | 26 Mar 2015 | Comments

Urbanisation is forcing us to rethink the way we power, connect and navigate our urban areas. We’re shifting the balance towards more sustainable solutions but are we moving faster than the problems are mounting up?

A report by the World Bank published in 2012 found that, on average, each city dweller generates over a kilogram of municipal solid waste (MSW) every day – this is the rubbish collected by local authorities that we produce, as do offices, schools and shops. Across the globe, it equates to 1.3 billion tonnes per year. Over the next decade the volume is predicted to double as the population continues to grow.

According to Dr Craig Edgar, head of renewable energy in Atkins’ power business, it’s time to think beyond our traditional responses: “Rapid urbanisation, particularly in the developing world is taking place against the backdrop of an increasing awareness of our finite resources as well as a requirement to reduce greenhouse gas emissions and improve the environment we live in,” he says. “And this extends to the way we manage our waste. Meeting the demands of more and more people, with cleaner, greener technology will require innovation.”

What’s being proposed demonstrates that one man’s trash really is another man’s treasure. It’s building on our existing approach to waste management to address another challenge associated with rapid urbanisation. That is, energy supply and security.

For many years, developed nations around the world have used MSW and commercial and industrial (C&I) waste to generate electricity, and sometimes heat. For example, the energy that is recovered through incineration is sold back to the grid or passed on to local consumers. But to limited effect. In the UK, for example, only 2.5 terawatt-hours (TWh) of electricity was generated in this way in 2012, compared with total supply of 376 TWh.

There are many reasons for not exploiting this potential energy source. The facilities needed to support this approach are usually large-scale and rely on mass burn technology, which is rarely popular with local residents. And overall, it requires a significant investment in infrastructure and the resources needed to maintain the operation. It’s the sort of thing many of us take for granted – our bins are emptied by local authorities each week, and we put our recycling out for kerbside collection. But in developing nations where waste management strategies are less developed, this is not always straightforward.

New technology is emerging that may increase the benefits of producing energy from waste and make it more accessible. Advanced thermal treatment (ATT), uses pyrolysis and/or gasification to process raw waste, chemically altering it in low or no oxygen environments to convert it to gaseous fuel that can then be combusted for energy or used as a chemical feedstock. These technologies themselves are not new (we were making town gas from coal this way nearly 100 years ago), but building and operating these facilities to produce energy from waste is only just starting to take off.

“The difference is that it’s not burning material in the same way as we have done for hundreds of years,” explains Edgar. “You can store the gaseous fuel from the conversion process, inject it back into the gas grid, or combust it to create electricity and heat. You can also use the fuel to make organic materials that might currently derive from oil, or to make hydrogen to power fuel cells. The technology can be adapted to generate the most useful energy source.”

ATT plants are often smaller scale and modular, which allows them to be implemented more widely, and they can offer better emissions performance than traditional incineration facilities. Yet they’re still considered to be relatively unproven technology.

“At the moment it can be difficult to get financing for new plants,” says Edgar. “From an engineering perspective, the technology works. But it is only now starting to be proven commercially. The challenges we need to address are around developing more and bigger projects, but fundamentally, there is a need to do something with the volume of waste we’re creating. And this is a process that will allow us to deliver value, whether it’s through the production of fuel, products or energy.”

The Confederation of European Waste-to-Energy Plants estimates that in 2012 there were 456 facilities across Europe, and collectively they prevented about 79 million tonnes of residual waste from going to landfill. Other facilities are under construction. But there are still very few ATT plants in operation in Europe.

However, some operators are forging ahead. Air Products, the large US integrated gases and chemicals company, is about to open the largest advanced plasma gasification energy facility in the world. The plant is near Billingham in the north east of England. Construction of a second identical scheme is also well underway, and together they will provide just under 100MW of renewable electricity generated from waste, which would be enough to power up to 100,000 homes. It will also stop 700,000 tonnes of household waste going to landfill each year.

The Air Products team worked closely with Atkins to address some of the environmental and social aspects of the project. Stephen Bradley, Air Products’ environmental advisor, European Environment, Health, Safety and Quality Management (EHSQ), explains the approach: “Collaboration was critical to bringing a project of this size and complexity to fruition. Inevitably, we did encounter challenges as we sought to implement this new technology, but we drew on the expertise of our wider team to find solutions. That included navigating the regulatory environment and presenting a robust case to achieve planning consent.

We hope the successful integration of advanced plasma gasification into our operations will encourage others to adopt a similar strategy,” he says. As Bradley points out, this is very much a multidisciplinary challenge.

Atkins is also working with Energos, who have also developed an ATT technology involving gasification of waste, to help deliver an advanced conversion facility as part of Viridor and Glasgow City Council’s £146 million Glasgow Recycling and Renewable Energy Centre. When the facility opens next year it will process the leftover post-recycled waste to generate enough renewable energy to power the equivalent of 22,000 households and heat the equivalent of 8,000 homes. Atkins also supports New Earth Solutions Group with their operational pyrolysis/gasification ATT scheme in Avonmouth.

As with anything new, there are a lot of risks associated with being innovative, and seeing a return on your investment. Atkins’ work with several leaders in the industry to develop ATT projects is aimed at minimising the risks they face as they try to embed this new technology. And according to Atkins’ Paul Yates, who is a client director in Atkins’ water and environment business, their success will provide the evidence needed to get more people on board.

“This could be a really important part of our energy mix,” he says. “By maximising the potential of waste-to-energy technology we’re turning the rubbish we all generate into a resource.” Every winter we hear about a potential energy crisis and our over-stretched infrastructure. ATT gives us the opportunity to reduce the pressure on the grid. “For example, if you’re a manufacturer with an energy dependent process and you’re at risk of grid insecurity, developing the resilience you need could be costly,” explains Yates. “However, smaller scale ATT technology may allow you to process the waste you’re generating, which will deliver the electricity or heat you need to keep your operations going. It’s a living example of what the Circular Economy could mean for energy intensive industry.”

For now, the viability of the projects largely depends on the political landscape. The technology is primarily being adopted in areas where there is a government subsidy or incentive. “This is not the cheapest way to produce electricity. So you need to find another way to make this appealing,” explains Edgar.

“There is complex technology involved so getting the costs down will be challenging. The alternative is making other forms of energy more expensive. You can do this by taxing carbon, or putting a price on CO2 emissions. Importantly, waste-to-energy needs to be classified as a renewable fuel source and that’s not always the case right now.”

Edgar adds: “Power is a policy driven market. If one were to simply select the lowest cost option, then there would be far fewer nuclear plants, offshore wind developments and waste-to-energy facilities. In the UK, market disruptors such as landfill tax and ROCs have created a financial driver for the development of advanced thermal treatment plants as a solution to our waste disposal and electrical generation needs. Providing a secure and stable policy environment to encourage investment in renewable technologies is still a huge challenge in the UK. This alongside the larger scale waste collection infrastructure challenges are perhaps the biggest hurdles that will need to be overcome if we are to see widespread adoption of these techniques on a more global scale.”

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