Diesel fuel alternatives

A reduction in emissions can be achieved through the use of cleaner fuels. Alternative fuels to standard diesel include low sulphur diesel (LSD), ultra low sulphur diesel (ULSD), biodiesel, blends of biodiesel with petroleum diesel and emulsified diesel.

Low sulphur diesel has sulphur content of 300 - 500ppm and reduces particulate matter (PM) by 10 - 20% compared to non-road diesel fuel (which can have a sulphur content as high as 3000 - 5000ppm).

Ultra low sulphur diesel is a refined, cleaner fuel with a sulphur content of 15ppm or less that can be used in any diesel engine. It reduces the fine PM emissions between 5 - 9%, depending on the baseline sulphur content, but when combined with a diesel particulate filter (DPF) it can lead to emission reductions of 60 - 90%.

Biodiesel is produced from new and used vegetable oils and animal fats. Biodiesel is safe, biodegradable and leads to a reduction in particulate matter (PM) , carbon monoxide (CO) and hydrocarbons (HC) but it can lead to an increase in the nitrogen oxides (NOx) emissions from the engine. It can be used in its pure form (B100) if engine modifications are made but is more usually blended as 20% biodiesel with 80% regular diesel (B20) which leads to a 10% PM reduction but increases NOx emissions by 2%. Biodiesel can also reduce lifecycle CO2 emissions since its production employs a closed carbon cycle that grows and processes plants to produce new fuel. Biodiesel may also have a cleaning effect on the engine, resulting in an engine that produces less smoke, runs more smoothly and produces less noise.

Emulsified diesel is a blended mixture of diesel, water and other additives and leads to a reduction in both PM and NOx emissions. Emulsified diesel can be used in any diesel engine but the addition of water reduces the energy content of the fuel which in turn reduces engine power and fuel economy. Emulsified diesel can reduce NOx emissions between 10 - 20% and ultra fine PM between 50 - 60%.

Studies have indicated that compared to ULSD both biodiesel (BD) and butanol diesel (DBu)  blends can effectively reduce the PM and elemental carbon emissions with butanol being more effective than bio-diesel. Compared with biodiesel fuels, butanol blended fuels have a lower gas exhaust temperature and emit lower PM and NOx levels although they also exhibited a higher level of CO and unburned HC emissions.

In petroleum-diesel and biodiesel blended fuels the emissions of PM and particulate organic carbon (OC) decrease significantly as the percentage of waste-edible-oil-biodiesel is increased. Addition of acetone and isopropyl alcohol to produce biodieselhols leads to further the concentration reductions of PM and particulate OC emissions.

As biodiesel and biodiesel fuel blends become more widely used in the construction and demolition industry their PM and NOx emissions will become more important and further studies should be carried out.

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