Robert Evans highlights the potential of biomethane to cut greenhouse gas emissions

Robert Evans _ Cenex.

Uniquely positioned between the technology provider and fleet user community, Cenex is always interested in ways low carbon vehicles can deliver real-world benefits. For example recently we were part of a major trial with Leeds City Council that involved the powering of refuse collection vehicles (RCVs) using biomethane fuel. The findings revealed that using biomethane can deliver both greatly reduced greenhouse gas (GHG) emissions and cost savings for UK local authorities.

Leeds City Council began the trial following a review of its total vehicle fleet. This Green Fleet Review, carried out in conjunction with Cenex and Energy Saving Trust, showed that while RCVs made up just seven per cent of its fleet, they were responsible for 25 per cent of total fuel use. Following our advice, biomethane was identified as showing the greatest potential for achieving the necessary savings.

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 GHG emissions, compared to the diesel Econics in the council's fleet. 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, this gap is expected to narrow as production increases.

Extrapolating the results of this trial across the UK fleet of RCVs demonstrates the potential for biomethane as a fuel. 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.

Ultimately, the potential for saving CO2 and other GHG emissions is the biggest strategic driver for the interest in gas vehicles. Although the fuel price differential drives individual decisions, this differential is largely due to a set of incentives set by government to promote GHG savings.

The public sector and especially local authorities, is under increasing pressure to lead by example in reducing emissions. Although the coalition government has largely removed the set of “National Indicators”, local authorities are still expected to report on the GHG emissions of their own estates, and for many such as Leeds, their RCV fleet will be a significant contributor to overall emissions.

Transport offers the biggest technical challenge to reducing emissions, and heavy-duty vehicles offer the smallest range of emissions reduction options. The energy density of diesel is very high, making it ideal for mobile applications and very difficult to replace, which is why transport has been so far excluded from most policies to tackle GHGs.

For heavy duty vehicles, there are very few mature technologies with the potential to offer GHG savings of 50 – 80% compared to diesel. If more mechanisms are introduced to effectively price carbon emissions, the economic case for biomethane as a vehicle fuel will quickly become compelling. With a pressing need to reduce greenhouse gases, it is imperative that we explore the use of new fuels such as biomethane wherever feasible.

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