The centre which encourages the early market adoption of low carbon technology – has made the claims following a year-long trial of the fuel by Leeds city council between May 2009 and July 2010, for which it provided technical advice.
Leeds city council began the trial following a review of its total vehicle fleet. This Green Fleet Review showed that while RCVs made up just seven per cent of its fleet, they were responsible for 25% of total fuel use. Following advice from the Centre for Excellence, known as Cenex, biomethane was identified as showing the greatest potential for achieving the necessary savings.
Anaerobic digestion of biological material in landfill sites or purpose-built AD plants – produces a mixture of gases typically referred to as biogas. As the methane content of biogas varies between 30-65%, a variety of technologies are used to purify and concentrate the methane into biomethane. This is considered to have zero net carbon emissions at the point of use as it comes from renewable sources- offering much higher potential greenhouse gas savings compared to natural gas.
The trial vehicle, a Mercedes-Benz Econic LLG with a spark ignition engine running solely on biomethane gas, is estimated to have achieved a 49% saving in well-to-wheel greenhouse gas emissions, compared to the diesel Econics in the councils fleet. However, this was achieved using a temporary filling station a more efficient permanent station raises the GHG saving to 64%, with possible 78%savings estimated if gas was generated on-site.
Additionally, lower fuel expenditure meant that annual vehicle running costs were estimated to be 2,500 less than a diesel equivalent. While gas vehicles currently cost more to purchase than diesel RCVs, Cenex said this gap is expected to narrow as production increases.
Given this success, Leeds city council has extended the trial for a further three to five years and hopes to eventually increase the number of gas vehicles within its 1,100 strong fleet.
With the assistance of the Infrastructure Grants Programme the council has installed a permanent filling station (see letsrecycle.com story), and hopes to eventually increase the number of gas vehicles within its 1,100 strong fleet.
According to Cenex, extrapolating the results of this trial across the UK fleet of RCVs demonstrates the potential for biomethane as a fuel.
It claims that using gas produced from either landfill sites or purpose built anaerobic digesters would save around 80% of emissions compared to diesel, as well as delivering substantial cost savings, due to factors such as the rising cost of diesel and the falling purchase cost of biomethane vehicles.
The trial findings were released at the UK AD & Biogas 2011 conference last month and are available for download at www.cenex.co.uk/resources.
Enormous potential
Richard Crowther , environmental assessment officer in transport policy at Leeds city council, said: Weve already done a great deal to improve the efficiency of our fleet vehicles and reduce unnecessary mileage, but weve reached a point where that in itself wont be enough to meet our environmental targets. We knew we needed to embrace low carbon technologies too and turned to Cenex for independent advice.
“This successful trial shows the enormous potential for switching sections of our fleet over to gas technology and we look forward to further savings following its extension.
Chris Walsh, head of technical support and consultancy at Cenex, added: In the UK, heavy goods vehicles such as refuse trucks contribute a disproportionately high percentage of carbon dioxide emissions. With a pressing need to reduce greenhouse gases, it is imperative that we explore the use of new fuels such as biomethane wherever feasible. This pioneering Leeds city council trial highlights the major advantages of switching the UKs RCV fleet to run on biomethane.
As well as the Mercedes-Benz Econic, the council also trialled a Dennis Eagle Elite modified by Hardstaff to run on a dual-fuel mix of diesel and gas. However this was in a much earlier stage of development at the time of the trial, meaning initial results were inconclusive. Development has continued since then, with a revised configuration now in use delivering increased cost and emissions savings.
The partners in the trial were: Leeds city council; Cenex; Mercedes-Benz; Dennis Eagle; and biomethane supplier Gasrec.
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