Getting soot off the black-list

 Posted by on 27 January 2014
Jan 272014
 
Image: CAS, University of Manchester

Image: CAS, University of Manchester

Attempts to reduce human impact on climate are not just about carbon dioxide. There are problems that, unlike CO2, you can see. Soot containing black carbon from burning fossil and biofuels is just one of those -  experts reckoning it to now be the second-leading cause of global warming; jumping ahead of methane.

Soot particles cause warming by converting sunlight to infrared radiation, whereas greenhouse gases absorb the earth’s heat radiation and reemit it into the air. They also fall on snow, darkening the surface and contribute to polar melting, have a tendency to get coated in other chemicals in the atmosphere, increasing particle size and so their ability to catch sun and produce radiation, and the heating effect.

It won’t come as much of a surprise that this can damage the health of living creatures like us. We blogged last year on the projected illnesses and deaths as a result of air pollution, and also on the targeted regional approaches to cutting damaging emissions at their source.

In the case of soot, the older the particle, the bigger it can get, so it stands to reason that stopping them at earliest possible point would be a very good idea. That’s where technologies like Diesel Particulate Filters, or DPFs, come in – but things are rarely that simple, are they.

It has been suggested that DPFs reduce fuel efficiency by 1-2 per cent by increasing piston pressure in the engine, while an added quandary is that COis produced in the filter by the oxidation of trapped soot, as well as water vapour.

But just how much of a problem is this? Well, the amount of CO2 created via the processes of the filter are relatively small fry compared to the volume coming from the fuel being burnt – an increase of 0.5 per cent. Of course, any increase is not great, but the figures stack up in favour of DPFs in the final analysis, even in a worst-case scenario of a five per cent increase in CO2 emissions from the technology.

In the event of this increase, the cost-to-benefit ratio works out at over a factor of 6.5. And with lower COemissions anticipated, it stands to be even more weighted towards benefit. Some final thoughts from our Transport Certification Manager Colin Smith:

Climate change is generally thought of as more long term but local air pollution and poor air quality is here and now. The diesel engine has its place in moving our economy forward, it is the main power source for vans, trucks buses, taxis, construction machinery and over the last few years we have been buying more diesel passenger cars due their lower CO2 emission levels, however at what cost to air quality and climate change through black carbon emissions?

“The latest vehicles and engines are getting more efficient and cleaner but what about the vast number that are already in operation, this is where retrofitting DPFs can help solve the problem. One area that has been a bit neglected is that of the construction industry, where in terms of particulate matter (PM) the average excavator can emit up to 15 times more than truck which complies to European regulations. By retrofitting a well designed DPF system it has been proven to reduce the PM by around 99% thus significantly reducing the immediate health impact and longer term climate change effect of black carbon.

“We have been certifying DPF systems and suppliers for many years now. So when you’re next passing by a large development, such as Battersea Power Station, imagine 15 trucks in place of each excavator and you may get a better idea of the impact both on air pollution and climate change from the black carbon being emitted.”

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