<< Previous page    Index    Next page >>

English Document

The road to pure plant oil in diesel engines?

Health aspects of running on PPO (pure plant oil) Straight Vegetable Oil (SVO)

In contrast to conventional diesel fuel, PPO is a pure biological product and is also used in food preparation. PPO contains no traces of carcinogens (benzene) and heavy metals, such as in conventional diesel fuels.

Soot particles

The physical-chemical composition24 of particles determine the amount of damage caused by the particle emission. An English test has shown that the particle size distribution for vehicles running on PPO is no different to that of fossil diesel [Ricardo, 2003]. There is little information available on the effect of the chemical composition of particles. Although some PM10 particles, such as those related to combustion processes, seem to be more important for health effects than other fractions (sea salt, inorganic secondary fine particles, and soil particles), there is little clarity on this subject.

It seems that the particle composition from a PPO vehicle is really no different to the particles from a standard diesel vehicle. Emission tests of PPO vehicles also show traces of substances that are damaging to human health, particularly toxic polycyclic aromatic hydrocarbons (PAH) that are released during incomplete combustion, e.g. formaldehyde, acetaldehyde and benzopyrene. These are also found in the same quantities in the exhaust gases of ordinary diesel vehicles [Ricardo, 2003]. There are possibly fewer heavy metals in the exhaust gas, because diesel contains traces of heavy metals, whereas PPO does not.
In short, there is very little evidence to show that the particles from PPO vehicles are far less toxic than fossil soot particles, but further research is required before it is possible to give scientifically proven judgements.

PPO (pure plant oil) compared to fossil-based diesel

Because the more important emissions (NOX and PM10) show no proven differences, the particle-size distribution for PPO and fossil diesel is identical, and PPO emissions also include toxic PAHs, the health effects of PPO vehicles are hardly any better than for diesel vehicles. Since PPO includes less aromatic substances (e.g. benzene) and fewer heavy metals, it is possible that less of these are found in the exhaust gases. An American study into the health effects of biodiesel (which is to some extent comparable to PPO), confirmed these assumptions. A Swedish study even suggests that the combustion of biodiesel produces a higher emission of toxic substances, primarily at relatively low engine temperatures (stationary) due to the low thermic stability. This is particularly important when used as a fuel for shipping, trains and city buses. This could well also be applicable for PPO [EPA, 2002].

Odour

Odour is an aspect that typically plays a role when using PPO as an engine fuel, and which often draws some comment. The exhaust gases have another odour, e.g. of cooking oil.
Modern diesel engines in cars are almost always fitted with an oxidation catalyst and, in these vehicles, there is almost no difference to the smell of conventional diesel25 . However, this does not apply to lorries, as oxidation catalysts are only used to a limited extent.

Costs of using PPO (pure plant oil)

The costs of using PPO as an engine fuel primarily lie in the conversion costs of the engine that, depending on the type of vehicle, are around € 1000. An estimate of the resulting extra costs per ton of rapeseed oil and per kilometre driven, at various annual distances, for an average driver and for someone who drives many kilometres.
A depreciation term of 8 years is assumed for the installation. The costs presented concern the extra vehicle costs, excluding extra maintenance. There is little information available on the extra maintenance costs as a result of blockages and cleaning. The fuel costs in Germany are around € 0.60 per litre. With the current high fuel prices it is possibly economically beneficial for consumers to convert to PPO, since this fuel is exempt from excise duty. This exemption for biofuels aims to encourage the development of these fuels.

Prospects for improvement and conclusions

Over the past few years the EU has achieved considerable emission reduction for traffic
through stricter emission criteria for new vehicles, and tightening the criteria for fuel
composition. When introducing PPO for vehicle use in the Netherlands, it is important to
prevent car emissions increasing. Problems concerning the sustainability of vehicles should
also be prevented. There are two points that require consideration:

• Ensure high-quality vehicle conversion (certification), so that low emissions levels are
  guaranteed;
• Ensure that the fuel produced meet quality norms. This can prevent damage to the
  engine and ensure that emission levels remain low. The German standard forms a good
  basis [Remmele, 2002].

Taxation of fuel

Taxation on SVO as a road fuel varies from country to country, and it is possible the revenue departments in many countries are even unaware of its use, or feel it sufficiently insignificant to legislate. Germany offers 0% taxation, resulting in their leading on most developments of the fuel use. There seems to be no clear taxation system in the USA, however given the low rate of fuel taxation, it is unlikely to face anything unfavourable, although charges could vary from state to state. In Ireland a pilot scheme is currently running (as of April 2006) whereby eight suppliers have been approved to sell SVO for use as a fuel without the payment of excise duty (VAT at 21% still applies, SVO from any other source still attracts exise duty at 36.8058 cents per litre plus 21% VAT). Despite its use being common in France, it would appear there has been no legislation to cover this.

In the UK, drivers using SVO have been prosecuted for failure to pay duty to Her Majesty's Revenue and Customs. The rate of taxation on SVO was originally set at a reduced rate of 27.1p per litre, but in late 2005, HMRC started to enforce the full diesel excise rate of 47.1p per litre. HMRC argued that SVOs on the market from small producers did not meet the official definition of "biodiesel" in Section 2AA of The Hydrocarbon Oil Duties Act 1979 (HODA), and consequently was merely a "fuel substitute" chargeable at the normal diesel rate. Such a policy seemed to contradict the UK Government's commitments to the Kyoto Protocol and to many EU directives and had many consequences, including an attempt to make the increase retrospective, with one organisation being hit with a £16,000 back tax bill. Such a change in the interpretation of excise duty effectively makes use of SVO in the UK nonviable by all but environmentalists, as the combined price of SVO and taxation for its use considerably exceeds the price of mineral diesel. HMRC's interpretation is being widely challenged by the SVO industry.

<< Previous page    Index    Next page >>