New trucks could end up running at dramatically redu-ced power levels if they use high-blend bio-diesel, Volvo has warned. The claim came at a CO2-free seminar held last week in Belgium. Lars Martensson, Volvo's environmental director, pointed out that many engines were now being refined to accept up to 100% bio-diesel blends.
And those high blends bro-ught undoubted benefits in net greenhouse gas - principally CO2 - reductions. But the resul-ting increase in NOx meant a trade-off in air-quality benefits. With this in mind, Volvo has set its limit at a 30% blend.
Exceeding the Euro 4 NOx limit on a new truck being fuelled with high-blend FAME bio-diesel is not technically against the law, because type- approval certification of emission level conformity is undertaken using a specified regular ultra-low sulphur fossil diesel fuel. But clearly under EU proposals for future 'in use' - ie roadside - checks on NOx and particulate matter compliance, based on 'never exceed' principles, the legality of B30-plus bio-diesel blends would be jeopardised.
Additionally, the high NOx level produced by some high-blend bio-diesels could trip the NOx sensor on newer trucks, causing the torque limiter to kick in. A different note of caution concerning bio-diesel use came from Anders Kellström, Volvo's alternative drivelines planning manager. He said although the EN14214 European standard set in 2003 for FAME bio-diesel helped ensure minimum requirements for some of the fuel's characteristics, variations could occur within the parameters of the EN standard, relating in particular to the origins of the feedstock.
In Europe, rapeseed oil was the prime source, but several other sources - notably used cooking oils - were now being used. Fuel derived from palm oil, for instance, could cause rapid sooting-up of filters. Resulting differences in the end product could therefore affect the determination of oil change intervals, for example. He said Volvo would like to see a more demanding international FAME fuel standard.
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