PARIS – In 2003, when several French companies were putting together a plan to jointly market diesel fuel tanks and particle filters, they called the partnership “On the Road to Green Diesel.”

Now that the project also embraces using urea in a selective catalytic reduction system to clean up oxides of nitrogen (NOx) emissions, the decision was fortuitous.

“Clean could mean just stopping the smoke,” says Thierry Seguelong, CEO of Aaqius & Aaqius, a French venture capital company. “Green means clean, no NOx and less CO2 (carbon dioxide).”

“On the Road to Green Diesel” started exhibiting its vision and products at the Society of Automotive Engineers World Congress and other venues in 2004.

Inergy SA, the global leader in plastic fuel tanks, has the central role. It is shouldered by Aaqius & Aaqius, which is invested in diesel aftermarket filter maker Jean Fayard’s Exoclean system, and Rhodia Group, which makes the liquid fuel additive Eolys, containing cerium, that is used to extend the life of ceramic diesel particle filters.

Although the three partners of “On the Road to Green Diesel” are French, they do not take a nationalistic approach to business. “Our biggest customers are German,” says Nicolas Weinstein, chief analyst of Aaqius.

Green Diesel basically markets a liquid solution to the two exhaust problems of diesel engines: soot and NOx.

Ceramic filters capture soot in tiny pores that need to be burned out periodically. Filters treated with platinum last the life of the car but require a 20-minute burnout every 400 to 500 km (248 to 410 miles) at 650° C (1,202° F), according to Rhodia’s François Garcia, business manager for Eolys.

Systems that add Eolys or competitive products, he says, need a 2-3 minute burnout every 800 to 1,000 km (497 to 621 miles) at 400° C (752° F).

NOx can be treated by capturing it in nitrate form within an absorbent mass, then reducing it with carbon monoxide and hydrocarbons produced in the exhaust stream by running the engine in a rich mode. Or it can be treated by adding drops of urea into the catalytic converter where it becomes ammonia, reducing the NOx to nitrogen and water.

For both NOx and soot, the liquid solution requires maintenance – replenishing the liquid – and the non-additive system uses more fuel, reducing the mileage benefit of a diesel.

On the filter side, European diesels in 2006 were split 50-50 between the solid and liquid treatment methods, with Rhodia having 90% of the liquid solutions.

Diesels built by PSA Peugeot Citroen and Ford Motor Co. use the liquid solution, in which a 0.5-gallon (2L) tank of the product dispenses 0.2 oz. (7.5 ml) of additive for every 13 gallons (50L) of diesel fuel.

The third generation of Rhodia’s Elyos, already available in the aftermarket, needs only 0.1 oz. (3.2 ml) per 50L of fuel, bringing the lifetime of a car system to 154,107 miles (248,000 km). “When that happens, Eolys will no longer be an additive,” Garcia says. “It will be a component.”

Inergy’s role is developing the tanks and dispensing pumps for the cerium filter additive and urea – called AdBlue in Europe. Inergy, a joint venture between Plastic Omnium and Solvay, is the global leader in plastic fuel tanks.

At the Paris auto show in September, designer Espera Sbarro worked with Inergy to transform a BMW vehicle into a prototype using Inergy’s fuel technologies, including a urea filler next to the capless diesel fuel filler and a built-in additive tank.

While the Green Diesel group works together, the relationship is not exclusive. For example, Inergy sells fuel and urea tanks to Volkswagen AG, which uses a catalyzed particle filter instead of the additive approach.

However, the partners believe their fluid approach will dominate. “We think that the majority of filters, 50% to 60%, will use the additives,” Aaqius’ Weinstein says, “and urea will play a primordial role in NOx reduction, 80% to 90%.”