REDUCING GREENHOUSE GAS EMISSIONS

Background

The main anthropogenic greenhouse gas is CO2, CO2 is produced from the combined actions of widespread fossil fuel combustion, deforestation and a range of industrial processes. The levels emitted are influenced predominantly by:

Power generation is the largest source of global CO2 emissions, but several other industrial sectors are also responsible for significant contributions. Major energy-using industries include cement manufacture, oil refining, chemicals production, iron and steel manufacture, and aluminum refining of which all emit substantial amounts of CO2 as well as other greenhouse gases. Significant amounts of CO2 are also produced by dispersed sources such as domestic appliances and transport.

Current CO2 emission levels are expected to continue increasing for some years and, based on World Energy Council growth projections, emissions from all sources are estimated to grow by 36% in 2010 (to 18.24 Gt/y) and by 76% in 2020 to 23.31 Gt/y (compared to the 2000 base level).

How can these increasing levels be reduced or stabilised?

Potentially, there is a wide range of ways to reduce emissions of greenhouse gases. In the case of CO2, reductions can be achieved by:

• Reducing the demand for energy;
• Altering the way in which it is used;
• Changing the methods of producing and delivering energy.

Demand for energy can be influenced by a number of means that include fiscal measures and changes in human behaviour. However, in the technical area, there are a number of distinct types of option for reducing emissions which are:

• Improving energy efficiency;
• Switching to low carbon fuel;
• Switching to no-carbon fuels;
• Preventing CO2 from fossil fuel combustion building up in the atmosphere.

In most cases, the first two options are cost-effective and will deliver useful reductions, but on their own, are unlikely to be enough. Greater reductions could be attained by switching to no-carbon fuels such as renewables and nuclear power; however, the world is presently heavily dependent on the exploitation and use of fossil fuels. For this reason, it is important that there should also be technology options that will allow for the continued use of fossil fuels. However, continuous use of fossil fuels needs to be undertaken without substantial emissions of CO2. In this respect, one route forward would be the development and deployment of technologies for the capture and storage of CO2 produced by the combustion of fossil fuels. An alternative way of reducing atmospheric levels of CO2 is through the enhancement of natural CO2 sinks. This could be achieved through enhancing the growth of terrestrial biomass (eg. forests) or biomass in the oceans. Both could make significant contributions towards curbing the growth of CO2 in the atmosphere. However, due to the quantities of CO2 involved, it is likely that a portfolio of measures that include all of the above will prove to be necessary.

Another important greenhouse gas, in terms of impact on the climate, is methane. Once again, there are a range of measures that could be employed to minimise methane emissions. Thus, production of methane could be limited, leakage during transportation and use controlled, and fugitive emissions captured and destroyed or put to use. For instance, in some cases, methane produced during coal mining operations can be captured and used to provide heat and electricity.

CO2 and CH4 are the main two greenhouse gases although there are a number of others such as nitrous oxide and CFCs that also require consideration. In some cases, remedial actions to reduce emissions can be taken or alternatively, their production and use can be monitored and reduced, with the eventual aim of being phased out