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Using gasoline and diesel as transport fuel causes emissions of both greenhouse gases, driving climate change, and of other air pollutants that are dangerous to human health and the natural environment. Transportation is the fastest-growing source of human-produced greenhouse gases. To prevent destructive climate change and reduce health impacts, the sector needs to move towards fuels that have a lower carbon footprint, and reduced emissions of sulfur and other conventional pollutants.
The most promising lower carbon fuels today are biofuels, natural gas and hydrogen. If these fuels are produced in the right way, they can have a significantly lower carbon footprint than diesel or gasoline. Several jurisdictions, including the USA, the European Union and the state of California have adopted or are considering standards mandating the use of low-carbon fuel pathways.
These standards must be crafted carefully, because there is no molecule that is low carbon in and of itself – biofuel, hydrogen and natural gas production all generate greenhouse gases. The implementation of low carbon fuels policies can also have indirect effects, such as driving indirect land use change. If unmanaged, these indirect effects could increase the net emissions resulting from policy implementation.
Fossil diesel is also often seen as a lower carbon alternative to gasoline, as using diesel causes 20 to 30 percent less carbon dioxide emissions compared to gasoline. As with biofuels, it is crucial that we consider the whole picture. Non-CO2 constituents of diesel exhaust fumes can also contribute to the greenhouse effect, including particulate matter, which contains heat-absorbing black carbon, and nitrogen oxides, which are precursors to the greenhouse gas ozone.
A number of countries have created standards requiring the use of control devices that can nearly eliminate these pollutants from diesel exhaust. There is a barrier to the adoption of similar standards in some developing countries, however, because high-sulfur diesel and gasoline destroy these pollution controls. ICCT is supporting local organizations in several countries that are campaigning for controls on fuel sulfur content.
The ICCT also supports efforts to eliminate the use of octane-boosting fuel additives containing heavy metals such as manganese, iron, and lead. These additives have been banned or voluntarily eliminated from fuels in developed countries, because of their demonstrated or suspected direct harmful consequences to public health and their disabling effects on vehicle pollution control devices such as catalytic converters. However, they are still used in many developing nations—even though alternative, economically feasible methods for boosting octane are widely available.
A full ‘lifecycle analysis’ of the emissions from a fuel pathway is necessary to understand the total emissions associated with producing that fuel. For fossil fuels, a lifecycle analysis should consider extraction, transportation and refining. For biofuels it must include cultivation, processing, land use change and a consideration of any by-products. Depending on the methodology used to assess the emissions associated with different fuels, it is possible for different lifecycle analyses to yield different results. The ICCT is playing an active role in the development of lifecycle analysis techniques, and in helping policy makers to understand and utilise the results.