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Putting discarded waste to use by creating energy – E & T Magazine

vol 7, issue 3

Putting discarded waste to use by creating energy

26 March 2012

By Sean Davies


Landfill site

EFW plant

Energy from waste projects, while appealing for a variety of reasons, have struggled to gain acceptance. But a new scalable method could provide the perfect solution.

Last year almost 300 million tonnes of waste were created in the UK, and almost half of that ended up in landfill. With government regulations aiming to reduce the amount of waste sent to landfill to zero by the end of the decade, the major challenge facing society is just what to do with it all.

One option is to burn it in waste incinerators, but that carries its own environmental challenges. Another, more appealing option is to use the waste as a fuel to generate electricity or heat using Energy from Waste (EFW) technology. This would, on the face of it, appear to be a win-win scenario; disposing of waste as well as helping the UK reach its target of 15 per cent of energy from renewables by 2020, as laid out in the EU renewable Energy Directive.

While all new EFW plants must meet strict emissions standards, including those on nitrogen oxides, sulphur dioxide, heavy metals and dioxins, that does not stop them facing objections from the environmental lobby. Concerns include fine particulate, heavy metals, trace dioxin and acid gas emissions, even though these emissions are relatively low from modern incinerators. Other concerns include toxic fly ash and incinerator bottom ash management.

The traditional method of using incineration to convert municipal solid waste to energy is a relatively old technology. Incineration generally entails burning waste to boil water, which powers steam generators that make energy to be used in our homes and businesses.

However, that is far from the only option and a host of projects around the globe are pushing the boundaries of EFW technologies. There are a number of other new and emerging technologies that are able to produce energy from waste and other fuels without direct combustion; these include gasification, plasma-arc gasification, pyrolysis and, for a non-thermal option, anaerobic digestion.

One option that is particularly appealing is pyrolysis. It can best be described as the thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. It involves the simultaneous change of chemical composition and physical phase, and is irreversible. Pyrolysis of organic substances produces gas and liquid products and leaves a solid residue richer in carbon content.

In pyrolysis, the heating occurs in the absence of oxygen and the released gases are gathered and stored for later use. One company that is developing an EFW system is Farnborough-based Qinetiq. In its system, a large screw-shaped column takes in up to 100kg per hour of untreated mixed waste including glass and tin, and particularly troublesome waste sources for thermal waste approaches. The waste is heated, releasing gases that are removed and used for heat or to power a steam turbine. What exits the system is a glassy substance just 5 per cent the volume of the waste that entered, and 400kW of power.

One of the chief drawbacks of commercial-scale EFW plants is the volume of waste they require. While this would appear to be an advantage, it has the drawback of fleets of lorries driving around the country delivering waste with all the attached environmental and social concerns.

The solution would appear to be smaller, localised EFW facilities, but to date that has proved to be an elusive concept. However, thanks to a solution initially developed for the Royal Navy by Qinetiq that may soon become a reality.

“We understand waste management challenges and we believe that the market is ready for small scale energy from waste solutions,” says John Ryley, managing director of the Technology Solutions Group at Qinetiq. “After eight years of thorough research and delivery, we have built on our waste disposal systems that are currently in service with the Royal Navy to develop the next generation EFW solution.”

The genesis for this technology was born out of a terrorist attack that took place 12 years ago. When the USS Cole entered the Yemeni Port of Aden in October 2000, its dual purpose was to take on fuel and offload several tonnes of rubbish accumulated during its tour of duty. That call into port had tragic consequences when a suicide bomb attack from a small boat left 17 dead and 39 injured.

Waste on naval vessels was becoming such a problem that during the Gulf War it was common to see a Royal Naval frigate towing a barge full of waste that could not be dumped at sea. “The MoD then came up with a requirement to have energy from waste plants deployed on the large ships,” Ryley explains. “This was then deployed eight years ago on HMS Ocean and it allows it to remain on station a lot longer.

“We did an analysis of the technologies available and came to the conclusion that pyrolysis was the cleanest, the most effective and offered the best reliability as well as being the most cost effective to construct and operate.”

The story so far

From those naval origins Qinetiq has refined the process and now has a plant installed at its Farnborough facility, which in the near future will be able to provide heat for use at the site. It will consume around 2,000t of mixed waste each year, enough to generate enough heat for about 300 homes or electricity for 50.

The most efficient way to use such a plant is to make use of the direct heat output, but it can also be coupled with a steam generator to produce electricity.

“We have been talking to some major supermarkets and they would look to take 20-30 units for their distribution centres,” Ryley adds. “The large supermarkets take food in and waste back: so when the waste arrives back at the distribution centre, instead of going to landfill it can go through the plant.

By mid-summer they expect to have any reliability concerns ironed out and a bill of materials standardised that will allow the plant to go into production – something that the company plan to outsource. For the test customers, Qinetiq is looking to select one site each from three key major sectors – health, retail and facilities management sector. “We are looking for an early adopter,” he continues. “We need a company that has a desire or requirement to adopt early technologies. Some supermarkets want proven technology so they are at the end of our chasm. Some say, ‘yes, this is a great idea, I want it tomorrow’. We tend to talk to a lot of hospitals who want this tomorrow.”

A model for waste

One big advantage of the EFW system is that there is no sorting of waste streams and no pre-heating required, the only proviso being that the moisture content cannot be too high as that would greatly reduce the efficiency of the plant. It can take mixed plastic, gas and metal. “We are working with Rushmore Council and they are delivering all of their mixed plastic waste and glass waste to us and we are running that through the plant.”

When it comes to optimising the performance of the plant in the future, Ryley admits that they may look at exactly what the optimum fuel would be, but at present they are content to let it run on mixed waste. What they have developed is a simulation tool that allows prospective clients to judge the viability of the system.

“We go to clients with the tool and ask them to input their current landfill and transportation costs, along with monthly waste estimates, and the mix of their waste types. Armed with this information, and their current power and heating spend, we are able to deliver a revenue model. On a simple chart they can see their return on investment allowing the client to see an estimated cost against value for the product.”

As an example Qinetiq pays about ‘90,000 a year to get rid of its waste from the Farnborough site. “From this point forward, that money is going to be channelled into the plant operation, so that will be a saving straight away,” Ryley says. “They will also not be buying as much heat.”

Financial solutions

Ryley suggests that the drivers for adoption of EFW are multiple, but they are primarily a combination of legislation, cost-cutting and the desire to be viewed as an environmental leader. The financial argument is solid. If you funded the purchase of the plant the return on investment would be between three and five years, well inside the usual investment criteria.

But the model that Qinetiq is adopting offers an even more advantageous financial solution. The plan is to lease the plant, and Ryley claims that the monthly payment is often less than the combined cost of fuel and waste removal. “If they are spending £100,000 a month on electricity or heat and this plant goes in on a lease costing, for example, so many thousands a month, it is less than they are paying and there is an immediate saving.”

Aside from making prudent financial sense and ticking the environmental box, there is also the matter of job creation. “For every one of these plants, you need two people to run it per shift. We have done some market research and the market around the UK for this type of product is about £4bn.

“With any new technology that is coming onto a market you need a service infrastructure round it. Whether it’s local or whether it’s remote, so you probably need some regional engineers and some local engineers as well just to monitor it.” Remote monitoring is made available by a multitude of Allen Bradley sensors that can be monitored locally or remotely.

Commercialising MOD IP

Often, for companies working in research and development in the military arena, the commercialisation of IP can be fraught with problems, but in this instance there were no such hoops to jump through. The majority of the IP was owned by Qinetiq, although the company had to acquire some additional IP for the plant. The agreement with the MoD on this project was that they could exploit the technology that they developed and that led to this plant – dubbed EFW7000. But even though this has yet to enter the commercial landscape there are plans afoot to develop even smaller versions, eventually down to single household size, although that would carry a whole new raft of challenges.

The target is 2016 for the mini EFW, but before that happens there need to be further breakthroughs. One of the key challenges is temperature; on the EFW7000 the only use of external power is to get the process up to working temperature, in excess of 700’C, after that it fuels itself.

However, in a household appliance it would almost certainly be fed waste on an intermittent nature, meaning that more external fuel would be required to achieve a working temperature.

“It would need a stand-by mode and you would have to work the plant in such a way that it integrated with the house, so when you put the waste in it holds it for a certain time,” Ryley admits. “It would then fire again and get rid of the waste and produces heat or electricity and if there is too much heat or too much electricity it goes back into the grid.”

But that’s for the future. For now the systems start appearing around the UK this year, to the benefit of the war on waste and the fight to comply with renewables obligations

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