Overall, this should be regarded as good news. On the basis that problems can only be addressed when they have been defined, the true extent of a major source of harmful emissions and, perhaps more importantly, greenhouse gases - has now been identified.
In fact, together with increasing fuel efficiency, reducing harmful emissions has been the key consideration for engine developers for over 20 years. Thus, when greenhouse gases become a major issue about 10 years ago, engine manufacturers could claim to have already been addressing carbon dioxide emissions, since they are directly proportional to fuel consumption.
Given that the engine industry is confident of meeting the next stage of marine exhaust emissions regulations without aftertreatment, (e.g. catalytic converters etc) the focus is still firmly on reducing emissions "at source" during combustion of fuel and the air, and great advances have been made.
On the fuel injection side, computer-controlled common-rail fuel injection technology has given the scope to optimise injection under all operating conditions and, on the combustion air side, advanced turbochargers are capable of giving similar levels of control.
More precisely controlled combustion is now possible and, since combustion is the central science of combustion engine technology, its greater control - and understanding - is central to achieving the ideal of reducing both emissions and fuel consumption at the same time.
Hercules Joins the Fight
Supporting these efforts, around three years ago the European Union decided it was time to encourage engine manufacturers to pool resources, in part to ensure that no new emissions reduction possibility was being missed for lack of knowledge-sharing among competitors.
The result was the EU sponsored, engine industry-wide "Hercules" marine engine development programme aimed at reducing large engine emissions. The programme recently reported on progress, including some very promising lines of attack.
Among them was early experience at engine builder MAN Diesel, based in Augsburg, Germany, with two-stage, high pressure turbocharging. This method promises considerable improvements in both emissions and fuel consumption, the company states. Combined with so-called "Miller" valve timing, which gives a useful reduction in emissions of oxides of nitrogen, two-stage high pressure turbocharging gives the potential to increase fuel efficiency - and hence reduce greenhouse gas emissions - by up to 8% with further reductions expected as the technology is developed to maturity.