POWER FROM WASTE
Wight means green in the UK1 July 2007
Isle of Wight residents will be the first in the UK to benefit from pioneering government-backed technology that allows the creation of 'green' energy from waste.
Consent has been granted for the construction of a new domestic waste gasification plant in southern England - the first of its type in the UK - which when completed will generate 2.3 MWe from 30 000 tonnes per year of domestic and general waste that would otherwise go to landfill or incineration. Gasification is an alternative to incineration that in this plant converts waste into fuel gas via a two-stage pyrolysis process, the resulting heat being used to produce steam, which is then used to generate electricity via a steam turbine, a method that is chosen on the grounds of higher generation efficiency. The plant is expected to become operational by early 2008.
The technology for the plant, which will be on the Isle of Wight off the southern UK coast, will be provided by Energos, which is part of the UK-based Ener-g group. The UK government through its Defra (department for Environment, Food and Rural Affairs) office will provide funding of £2.7m to meet 35 % of the £8 m cost of developing and operating the facility during its first year. The project is part of Defra’s New Technology Demonstrator Programme, of which the objective is to promote innovative ways of reducing biodegradable waste sent to landfill, and will re-use part of an existing energy plant on the island, effectively converting it into a new facility. The fuel will be supplied by a ‘resource recovery facility’ operated by Biffa Waste Services subsidiary Island Waste Services, the Isle of Wight Council’s integrated waste management contractor.
Nick Dawber, managing director of Energos said, “The small scale local solution is environmentally beneficial because it cuts out the need to use heavy vehicles to transport domestic waste over long distances to large scale incinerators, reducing road haulage costs and exhaust emissions.
Another benefit of this localised solution is that because the energy will be used on the island, there will be little wastage during the transmission process.”
The Energos patented gasification technology was developed during the nineties in conjunction with the University of Trondheim. This two stage process produces a ‘syngas’ from waste in the first stage gasifier; this syngas is transferred to the second stage oxidation chamber where it is fully combusted. Each stage can be individually controlled and because a syngas is produced, a homogeneous mixture can be burned to produce very low emissions, reaping the benefits of a simple, low-cost, dry flue-gas system.
The plant will consume 30 000 tonnes per year of residual waste out of the 60 000 tonnes currently being processed at the Island Waste Services resource recovery facility. This is intended to demonstrate the capability of the technology to divert post-recycling refuse from landfill, therefore extending the life of the landfill site and helping the Isle of Wight Council to meet its landfill allowance obligations.
The plant is part of a wider policy for the island which is aiming at a degree of self-sufficiency which it is achieving through recycling, composting and now energy from waste. This project will mean that the Isle of Wight will have one of the highest landfill diversion rates in the UK, saving in landfill tax payments and extending the life of its limited landfill space.
As political pressures mount on local authorities to move away from landfill, the companies that can supply leading-edge gasification technology can secure lucrative long term fuel contracts.
“In conjunction with an efficient recycling programme, the thermal treatment of MSW using advanced conversion technologies - pyrolysis, gasification and anaerobic digestion - is a highly effective solution,” says Nick Dawber. In the UK it is also supported by legislation under the Renewables Obligation, meaning that electricity produced from MSW can be sold at a higher price than electricity from non renewable sources.
A single-line standard Energos plant has the capability to produce steam for heating, hot water or electricity production. In the case of electricity, around 3.1 to 3.5MWe, depending on the calorific value of the waste fuel. Its emissions are significantly below EU limits (2000/76/EC) and are checked by environmental agencies at the operating plants.
Other benefits derive from emissions legislation. Energy recovered from the biomass portion of waste (typically more than 60 %) is exempt from CO2 emissions obligations under the EU Emissions Trading Scheme. From Phase 2 of the scheme, companies will be allowed to trade CO2 credits. Energy recovered from waste on site will not be subject to the Climate Change Levy (CCL) and will count towards energy reduction or efficiency targets.
A big hit in Europe
Gasification technology has established a formidable track record in Europe. There are currently six similar Energos plants operating in Norway and Germany and the technology has a ten year track record with over 280 000 hours of operating experience. The compact design of these facilities means they can be sited near the communities they serve and can convert non-recyclable waste into useful energy.
The Energos plant at Forus (Stavanger) in Norway is a powerful illustration of how this patented technology plays a pivotal role in a local waste management strategy, enabling the local authority to meet its obligations under the EU Landfill Directive to divert BMW from landfill.
In the Stavanger region (population 275 000), kerbside collections of paper/card, garden and kitchen waste, together with recycling at ‘bring sites’ enabled the area to achieve 56 % recycling in 2006. Of the regional municipal solid waste (MSW), 32 % was delivered as residual waste and treated at the Energos plant. In addition to residual MSW the plant also received some commercial waste, taking 18 % of its capacity.
“From a total dependence on landfill, only 10% of the MSW collected in 2006 was sent to landfill,” said Nick Dawber. “The 40 000 tonnes per annum EfW plant has been providing an important community function since opening in 2002.” The recovered energy provides electricity into the local grid and hot water into a district heating system for an adjacent industrial and commercial estate.
The 30 000 tonnes per annum Energos plant at Averøy in the Nordmore region of Norway opened early in 2000 - serving a population of 66000 people. In 2004 the region produced 32 000 tonnes of MSW of which 26% was recycled and 19% (of which 1/3 was inert) was sent to landfill.
Of the MSW collected, 50% was residual waste treated by the EfW plant, and as an established regional waste treatment facility it also treats waste from the commercial sector. The major part of recovered energy goes as steam to an adjacent fish feed factory, displacing fossil fuel previously used in its boiler and helping to support the local fish farming industry.
|The pyrolysis concept|
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