air pollution

Particulate matter emissions from diesel engines and other sources

The two most significant pollutants produced by humans (anthropogenic) are NOx emissions and particulates. Information on NOx emissions can be found here.

Q. What are particulate matter emissions?
A. These are solid and liquid particles which are small enough to be suspended in the air (aerosol), and will be inhaled. They are produced by:-

  • Burning fossil fuels or plant matter, ranging from diesel emissions to burning for deforestation. In some areas wood-burning stoves are a particular problem.
  • Dust from human activity such as construction or mining.
  • Liquid droplets formed from combustion products, evaporation, and further reactions in the atmosphere.
  • Other natural events such as volcanic eruptions.

Q. What is Particulate Matter (PM)?
A. Particulate Matter is the name given to these solid and/or liquid particles, and they are defined by their size. If particles are more than 100 microns (a tenth of a millimetre) in size, they won’t stay suspended in the air. Two grades of PM are regulated:-

  • PM10 – are ‘coarse’ particles between 10 and 2.5 microns in size.
  • PM2.5 – are ‘fine’ particles of less then 2.5 microns in size.
  • Really small particles are variously known as ‘ultra-fine’ or ‘nano’ particles, but there isn’t a universally recognised term for them.

hybrid efficient vehicles

Q. How are particulates formed in a diesel engine?
A. Air is compressed in the cylinder of diesel engines, and finely atomised fuel is injected into the cylinder. The fuel burns, but the fuel-rich regions don't burn completely, producing soot particles and partly-burnt fuel. As the exhaust cools, the partially-burnt fuel is adsorbed onto the soot particles, producing a toxic mixture.

Q. Why are more particulates formed in a diesel engine than in a petrol/gasoline engine?
A.Fuel burn is less even in a diesel engines than in a petrol/gasoline engine.

Q. How are particulates removed from diesel exhausts?
A. Modern commercial vehicle have particulate filters in their exhaust systems, which mechanically trap the soot particles. These are mainly ceramic, but some are woven metal. In most cases the filters can be regenerated by increasing the exhaust temperature, which burns off the carbon.

Q. Why are particulates harmful?
A. Small particles can penetrate deep into the lungs and cause respiratory problems. Nano-particles can even enter the bloodstream. It is worth noting that tobacco smoke produces particulates in the most harmful range.

Q. How do you remove particulates from industrial processes?
A. A wide range of equipment is available depending on the size range and quantity of particles produced. These include cyclones, electrostatic precipitators, wet scrubbers and fabric filters.

Omnagen can advise on measuring and mitigating particulate emissions. Contact details are here.

hybrid efficient vehicles

Diesel engines are more fuel-efficient than petrol/gasoline engines, but their NOx and particulate emissions cause problems, most notably in cities. Hybrid vehicles operating in "electric-mode" produce no pollution, which is good for city use. However, fuel efficiency on longer distances needs improvement. Omnagen has a solution. Read more...

industrial emissions

industrial emissions

Industrial carbon emissions are high, and are continuing to rise with increasing economic activity. The need to limit climate change means that carbon emissions have to reduce rapidly. US data shows that the gap between actual and target emissions is already huge. Read more...

sustainable energy

sustainable energy

Oil and gas contain carbon, and energy is released when it reacts with air. By controlling this reaction it is possible to generate electricity, as well as converting the carbon into a useful product instead of carbon dioxide. We call this clean carbon energy. Conversion to CO2 pollutes the atmosphere, and wastes a valuable resource. Omnagen can provide a way to harness this energy. Read more...