While an obvious benefit to the environment, these standards are a challenge for yacht builders, designers and engine manufacturers.
The technology being used to reduce NOx emissions is called a Selective Catalytic Reduction (SCR) unit. It uses a diesel exhaust fluid called urea that that acts as a reductant – when it reacts with NOx it converts pollutants into natural elements such as nitrogen, water and minuscule amounts of CO2.
The SCR units are big and heavy, taking up valuable engine room space and weight. There also needs to be a tank for the urea, a material that’s not widely available in the world’s ports.
Pieter van der Linden, mechanical engineering department manager of Heesen Yachts, says it’s best to think of the new equipment as a necessity rather than a burden. “It’s part of a total yacht now, same as the engine,” he says.
The bad news is there is no single solution for reducing NOx emissions in yachts. The current cure involves a number of parties – engine manufacturer, exhaust company, exhaust after-treatment firm – but most builders will want to deal with as few people as possible.
The good news is this lack of uniformity paves the way for creativity, because after-treatment units can be made in different shapes and customised to a point. Volvo is adapting its decade of on-road SCR experience to the marine environment, with an added focus on fuel efficiency, which will in turn lead to smaller fuel tanks and overall weight savings.