Non-Esterified Plant Oils as Fuel -Engine Characteristics, Emissions and Mutagenic effects of PM- 2009-24-0097

Plant oils may be used as a sustainable, nearly CO₂ neutral fuel for diesel engines. This work investigates experimentally the particulate and gaseous emissions of diesel engines fuelled with non-esterified, pure plant oils with the quality standard of DIN V 51605 (Weihen-stephan RK-Qualitätsstandard 05/2000). The data are collected from three engines:

• Common rail passenger car engine from OPEL AG
• Truck engine from VOLVO
• Truck engine from MAN AG

All engines have been correctly adjusted to plant oil operation.

The OPEL and VOLVO engines served for the basic investigations. The emissions of the MAN engine have been used to perform AMES tests to analyze possible health impacts of plant oil operation.

The experimental data show a reduction of particulate matter compared to traditional gasoil which may yield up to 50 % for. The particulate matter shows same primary particle sizes but the agglomerates as collected on TEM grids are different - the plant oil soot particles tend to form larger aggregates [4]. The gaseous emissions of CO and hydrocarbons HC are generally lower compared to the operation with gasoil. However, the NO_X emissions are slightly higher. This may be contributed to the measured higher combustion chamber pressures and temperatures when fuelled by plant oils.

Emission samples have been extracted from ESC cycles of 13 step tests to perform the AMES test which give indication on carcinogen substances. The AMES test results gave no indication of mutagenic effects exceeding the detection limits. No significant differences could be found comparing the emissions of plant oil and gasoil operation. Thus, it can be stated that the emission from plant oil operation does not have a health impact different to traditional gas oil. This is in contrast to some other publications — a deeper insight shows that these investigations did not properly modify the engine for plant oils. It is mandatory to make the engine modification to pre-warm the plant oils to approx. 90°C prior to injection. The engine's warm-up phase needs special care to avoid any coking at the injection system and combustion chamber surfaces. The publications where a higher health risk was claimed to be found in the exhaust of plant oil fuels, did not pre-warm the plant oils — cold plant oils have been injected in the combustion chamber instead. This results in incomplete atomization and incomplete combustion with a lot of hazardous emission species (see also [4,11]. Such an operation will damage the engine after relatively short times and is, therefore, not realistic.

The investigated fuels had some influence on the engine characteristics. Higher temperatures and pressures in the cylinder have been detected for some plant oils compared to gasoil. This increase is explained by the higher oxygen content within the plant oils.