Gas and oil are the most used heating fuels in our regions. Both fossil fuels generate greenhouse gases. Therefore it is better to use other heating methods that are more environment friendly or combine one's existing system with a system based on renewable energy such as heat pumps or solar panels. 

Given that heat yields from oil or gas boilers are relatively the same, the choice will mainly depend on the availability of resources, practical aspects of installing the system, the type of proposed controls (thermostat, etc.) or even the ease or frequency of maintenance of the boilers. 

Fossil fuels

Both natural gas and oil are fossil fuels, obtained from the fossilisation of living organisms.

Oil is a liquid fuel derived from petroleum. Our market has two standard forms of fuel-oil: diesel and diesel extra. This means that despite market liberalisation, the fuel oils offered by suppliers are identical in nature.

On the other hand, the physical and chemical composition of natural gas is not standardised. However, it is still largely made up of methane and contains nitrogen in varying amounts.

There are two types of gas based on their composition:
1. rich gas (or gas H for "High caloric value", higher than pure methane) ;
2. lean gas.

Both are distributed in Belgium.

Emissions of pollutants

• Carbon dioxide: CO2

Oil and natural gas are both fossil fuels. When they burn, they emit CO2. However, natural gas emits about 25% less of CO2 than does oil.

• Sulphur dioxide: SO2

Unlike natural gas, oil emits sulphur dioxide (SO2), an air pollutant that contributes to the formation of acid rain. Regulations on these emissions has changed significantly in recent years.

In January 2008, the conventional oil (diesel) at 2000 ppm (parts per million i.e. 10-6) was replaced by fuel oil at 1000 ppm. This represents a 50% reduction in SO2 emissions!

And this downward trend is continuing. There is now an oil with very low sulphur content called oil extra (earlier maximum 50 ppm of sulphur content and now maximum 10 ppm) that pollutes even less. This oil with very low sulphur content, intended primarily for some condensing boilers, can also be used in other types of installations. Unfortunately, the desulphurisation that it undergoes makes it more expensive than traditional fuel oil.

• Nitrogen oxides: NOx

Nitrogen oxides (NOx) emissions are also very high in oil based heating. They result from the oxidation of nitrogen present in air to a large extent and the presence of nitrogen in the oil to a smaller extent.

NOx are also called "ozone precursors". Under the action of sunlight, NOxcan contribute to ozone formation. And ozone is a risk prone oxidizing agent for sensitive people. The concentration of ozone in the atmosphere can create ozone peaks. These ozone peaks can affect the health of groups of people at risk (elderly, children and other people at risk).

Unlike oil, natural gas produces less nitrogen oxide, but is by no means harmless.

• Methane : CH4

Leakages of gas, and thereby of methane, that escape from distribution pipelines or at the time of extraction represent a real hazard to the environment. In fact, methane is a greenhouse gas that has the greatest effect on global warming.

For example, given equal quantities of emissions, the contribution of methane to global warming is 20-23 times higher than that of CO2. Methane leaks also damage the surrounding ecosystems by asphyxiation of the plant root systems.