The rush to develop petrol particulate filters

Volkswagen announced almost three years ago that it would be employing gasoline/petrol particulate filter (GPF) systems to reduce emissions across its range of petrol-powered vehicles – not just the diesels.

Along with other car makers such as Mercedes-Benz, BMW, Ford and Land Rover, the German conglomerate is aiming to keep petrol viable in the face of increasing pressure from electricity as the industry’s dominant power source of the future.

The use of GPF systems comes as a response to ever-tightening emissions restrictions, which address a problem that only came to light in the early 2000s when it was discovered that beneath the already-familiar (10 micron) particulates found in diesel engine exhausts there was a presence of finer particulates (nanoparticles) more than 100 times smaller.

More disturbingly, it was found in a report commissioned by the Swedish National Road Administration that these nanoparticles were produced by some petrol engines too, in certain conditions, in equal numbers to diesel engines.

Capable of penetrating deeper into the lungs when breathed in, these nanoparticles were revealed to be a big, hitherto-unseen health risk inherent in motor vehicle emissions.

The good news is that GPF technology is capable of capturing not just the familiar diesel particulates, but also the nanoparticles found in both diesel and petrol exhausts.

Typically, the particulate filter used in GPF systems is attached close to the turbo where it heats up rapidly so it can perform its functions of dealing with HC, NOx and CO emissions seconds after the engine is fired up. The gases then pass through a conventional catalytic converter, usually located under the vehicle, to finish the clean-up job.

And what about new-fangled diesel tech?

All this cleaner petrol activity comes as various manufacturers announce plans to rid themselves of diesel engines altogether just as they face the prospect of being forced by governments to retrofit emissions-reducing technology in older diesel vehicles.

At the same time, promising new developments are hinting at breakthroughs that have the potential to significantly clean up oil-burners for a lifespan well beyond what is currently being predicted. German auto parts supplier Bosch is working on a revised filter-based system claimed to reduce NOx levels to 13 milligrams per kilometre and academics at two British universities are making progress with ACCT, or Ammonia Creation and Conversion Technology, which is said to drastically reduce NOx emissions.

While there is some scepticism about Bosch’s claim that it has found the Holy Grail guaranteeing diesel’s future, it nevertheless appears there could be some life yet in fossil-fuel power.