Black Carbon

Black Carbon (BC) refers to the soot emissions from burning carbon, be it a forst fire or a coal power station. From the 2010 United States Environmental Protection Agency report to Congress on Black Carbon, I'm going to study the impacts of our BC emissions. A signficant source of BC is in producing electricity, and in preparing to meet future eclectricity demand the impacts of BC should be considered.

BC is produced by the incomplete combustion of plant matter: fossil fuels, biofuels and biomass. BC is emitted into the atmopshere in the form of fine particles (PM) At present the majority of BC emissions come from Asia, Latin America and Africa.

Global BC Emissions

The direct environmental impacts of BC emissions are absorbing light, depositng on snow and ice reducing albedo (reflectivity), and interacting with clouds. Through such mechanisms, BC contributes to increased tempeatures and accelerated ice and snow melt. Regarding BC interaction with clouds, the formation of atmopsheric brown clouds, surface dimming and changes in the spatial and temporal varaiton in precipiation are further impacts of BC.

Regions such as the Arcitc and Himalayas, already very sensitive environments, are particually vulnerable to the effects listed above. Environmentally, it is therefore important to try and shift away from BC to minimise anthropogenic climate change and protect these vulnerabe areas.

The report to congress concluded that signficant public health benefits can be achieved by reducing BC emissions. In the US:

"The average public health benefits associated with reducing directly emitted PM are estimated to range from $290,000 to $1.2 million per ton PM in 2030. The cost of the controls necessary to achieve these reductions is generally far lower."

On a global scale, WHO estimates that millions of premature deaths a year are caused by PM, with smoke from solid fuels indoors contributing to two million deaths annually alone.

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Fortunately, BC has a relatively short atmospheric lifespan, especially when compared to emissions like CFCs and HCFCs, of days to weeks. This means that stratergies to reduce BC emissions are likely to have an impact within decades. Achieving such a reduction will require specific policy focus. The US is committed to substantial BC reductions by 2030, but at present only produce 8% of global emissions. The most important BC emission reduction opportunities are in the use of diesel fuel worldwide (see the potential impacts of recent Volkswagen diesel scandal), residential cookstoves, and Asian brick kilns and coke ovens.

There are some uncertainties remaining about BC, but the information available gives strong evidence of the adverse environmental and social affects of BC. As such, mitigation of BC emissions should be a priority when considering the future energy mix.

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