Cottoning on to a safer exhaust filter

A simple box device containing a series of cotton filters could play a large role in improving global air quality as well as being a huge success for the small engineering business behind it.

Staff at Aerotech Engineering, in Hull, northern England, are talking to potential licensees in a bid to see the company's patented Dert (diesel emission reduction technology) system brought to market.

Mounted on vehicle exhaust systems, Dert safely removes hydrocarbon particles produced by engines and deposited into the air around us.

Dert is in the final stages of development and once manufactured would be much cheaper than rival emission-reduction solutions and also easier to fit, reusable and ideal for developing countries.

Although Aerotech Engineering is focusing on the HGV market first because there are tax incentives for owners to fit emission-reducing devices, the filter could be fitted to any other vehicle.

Julian Hasinski, an aerotechnology engineer and Dert's inventor, formed Aerotech Engineering in 1985 and it was three years later, while looking at devices that filter air entering engines that he came up with the idea behind Dert.

He recalls: "We ran it on a test engine and to our surprise one straightforward cotton filter managed to trap 65 per cent of the particles we could measure. It is basically an arrangement of five to seven cassettes with each cassette carrying a corrugated filter to maximise its surface area.

"The first filter gathers most soot with the remaining ones bringing the percentage of cleanliness higher with the more filters you have. When the first filter starts to clog, a system of bypass valves opens up so you never actually stop filtering the emissions.

"Filtering exhausts is not new but what we have patented are slightly different angles in managing temperature, managing the deposit itself and enclosing it," he added.

Hasinski says that for a 15-ton truck, his Dert system would be eight times cheaper to buy than ceramic-based filters and, unlike the rival system, it would not need turning every 100,000 kilometres (60,000 miles) and replacing every 200,000km, an expensive process that involves dismantling the engine.

"Our system is a bit like plugging a vacuum cleaner hose on to the back of your exhaust pipe," he says. "If I had an ultimate ambition it would be for an emission-free aircraft." He believes the system is perfect for developing countries with pollution problems because it is cheap and can use locally grown natural fibres. In addition the cotton filters can be washed for reuse.

Aerotech Engineering has already received inquiries from local authorities keen to clean up their vehicle fleets and from companies exporting diesel engine parts to the developing world.

Aerotech's commercial director John Cudbertson said: "The market is potentially enormous. In this country alone there are 100,000 heavy goods vehicles (HGVs) on the road without any kind of emission control. If you sell the box for 500 pounds each there's a possible 50 million pounds market. Even with a conservative estimate of selling to one per cent, the market is huge."