18 March 2010

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A Guide to Alternative Fuels

Different fuels have different advantages. Compared to petrol, diesel vehicles have significantly lower CO2 emissions per kilometre travelled because of the higher efficiency of diesel engines.

Diesel vehicles also emit lower levels of HC than equivalent petrol vehicles. However, diesel engines emit greater levels of NOx (Nitrous Oxide) and Particles than new petrol vehicles.

Between diesel and petrol it really depends on the mileage your vehicles do. Diesel is currently more expensive than petrol and this trend is set to continue. Diesel is often written off as "dirty" but sometimes it is a better option especially if fitted with particulate filters.

Manufacturers are producing ever greener diesel cars such as the Citroen C2 1.4 HDi L at 113g/km CO2 and 69MPG.

LPG ( liquid petroleum gas )

LPG produces fewer emissions than petrol and diesel but fuel consumption is worse. It has been popular in the past due to its cheaper cost, as it has less road, personal tax and fuel duty. However there are no cars currently manufactured in the UK that are LPG ready, a conversion costing around £2000 is necessary. It’s still a popular choice because overall it’s cheaper and better for the engines as it has a simple chemical make-up. CNG ( compressed natural gas ) is also lower in emissions but limited in places to refill.

Biofuels

Biofuels which usually means Bio-diesel blends natural oil (eg rapeseed) with diesel is compatible with most modern diesel engines. The natural oils do not have the carbon emissions of fossil fuels reducing CO2 emissions. They have drawbacks environmentally, as they increase demand for horticultural land, possible encouraging the destruction of natural habitats and push up food prices due to the increase competition for crops. There is also limited availability of this fuel as of yet.

Bio-petrol

Bio-petrol is a mixture of petrol and ethanol. It is more expensive to covert a petrol car to run on ethanol than it is to convert diesel to run on bio-diesel but it is still a useful, if somewhat developing technology. Most cars will require an adaptation to run on bio-ethanol if the concentration of ethanol exceeds 10%. Most cars can run on what is known as E10. There a very few cars available on the market at the moment that will run on higher concentrations such as E85 (85% ethanol). Again, there are environmental drawbacks with increased demand for crops.

Electric engines

Electric engines are obviously free of emissions, which is good for local air quality but the source of the energy is most likely from burning fossil fuels currently. They are also usually limited in speed and can only make around 60 miles before needing recharging. Watch out for improved models though as the technology is developing.

Hybrid Cars

Hybrid cars offer reduced fuel consumption and therefore lower CO2 with potentially a positive effect on local air quality. Hybrid petrol-electric cars have an electric motor which provides the power at low speeds and move to petrol for driving at higher speeds. They therefore achieve the best fuel economy in urban driving rather than on a motorway run. The batteries are recharged while driving, hybrids use regenerative braking meaning that energy is put back into the battery when braking. This greatly improves energy efficiency. Hybrid diesel-electric is still under development but will achieve even better fuel economy.

Other technologies are still developing such as Hydrogen engines, which are considered to be the one to watch as there only emission is water. Keep an eye on TheGreenCarWebsite.co.uk for updates.

Author: Paul Lucas, February 12, 2010

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