Exhaust emissions – what are they?


Motor vehicles are an essential part of everyday life, from dropping the kids off at school to massive B-trains hauling goods down SH1. These vehicles all have an internal combustion engine which provides the power, the driving force. Unfortunately, where you have internal combustion engines, you also have exhaust emissions. It’s one of the big challenges of our time.

Exhaust emissions are associated with a number of well documented health and environmental issues. Emissions include particulates, such as carbon monoxide, carbon dioxide, nitrogen dioxide, sulphur dioxide and benzene.

Research indicates that the most damaging to people's health are particulates and carbon monoxide. A Ministry of Transport report estimated that around 400 people, aged 30 and over die prematurely each year due to exposure to vehicle emissions.

The good news is that modern vehicle engines are vastly cleaner than old engine designs. Believe it or not, using a petrol powered lawn mower for one hour produces the same amount of hydrocarbons as driving an average modern car for 300 kilometres!

A key component in petrol engine vehicles is the catalytic converter. Modern ‘three-way’ catalytic converters act to change the three main pollutants to less toxic compounds: carbon monoxide, unburnt hydrocarbons and nitrogen oxides to carbon dioxide, nitrogen and water vapour.

Diesel vehicles use a number of emission reduction technologies:

Carbon dioxide and unburnt hydrocarbons: Oxidation catalysts use oxygen to convert carbon monoxide and unburnt hydrocarbons into carbon dioxide and water. The catalysts work best with low sulphur fuels.

Nitrogen oxides: One way to reach Euro 5 limits for nitrogen oxide emissions is for trucks coming into New Zealand to be equipped with Selective Catalytic Reduction (SCR) systems. SCR uses a high purity urea solution called “Diesel Exhaust Fluid” which is injected into a special catalytic convertor. This reduces the nitrous oxides to harmless nitrogen and water.

Z Energy has worked with our largest transport customer, to install specialised dispensers at a test site which deliver Z-DEC, Z Energy’s Diesel Emission Cleaner, into our customer’s Euro 5 tankers. We are now reviewing further possibilities for this product, looking at installing Z-DEC dispensers at selected truck stop sites around New Zealand. We will keep you posted.

Sulphur oxides: Are controlled by reducing the fuel’s sulphur content. Diesel sold by Z Energy has a maximum sulphur content of 10 parts per million; this is classified as an ultra-low sulphur diesel.

Particulate matter, commonly known as soot: Is reduced by low sulphur fuel and the use of diesel particulate filters. These filters trap the particles and periodically heat up so the carbon is oxidised to produce carbon dioxide.

Another way of reducing emissions is to simply reduce fuel usage. Z Energy has made the decision to reduce our emission foot print by changing to hybrid cars for our mobile staff. The change to hybrid cars is projected to reduce our carbon dioxide emissions by 87 tonnes per annum when fully implemented, due to the fact that hybrid engines run at the most efficient and constant rev range and under the optimal load to produce the most power for the least emissions.