Diesel consumption rises, black carbon concentrations drop in California

Black carbon: What is it?

Black carbon, according to the California Environmental Protection Agency Air Resources Board (ARB) in its news release: “California’s efforts to clean up diesel engines have helped reduce impact of climate change on state, study finds: Clean diesel programs slashed black carbon, a powerful short-term contributor to global warming,” consists of tiny particles of soot introduced into the air from the igniting of fuels. It is my understanding black carbon is a component of particulate matter – both PM 10 and PM 2.5. Black carbon was also earlier discussed in “Black carbon a major air pollution culprit.”

Black carbon: What are its sources?

“The major sources of black carbon in California are diesel-burning mobile sources, residential wood burning in fireplaces and heaters, agricultural burning and wildfires,” the ARB notes.

Diesel-smoke[1]In the same ARB news release, presented at the bottom is a graph. Plotted are both “Atmospheric Black Carbon Concentration” (solid black line) and “Diesel Fuel Consumption” (dashed burgundy line).

What is evident from this graph is that “Diesel Fuel Consumption” between 1960 and about 2010 or 2011 shows that this has trended upward meaning consumption of diesel fuel (measured in British Thermal Units) in California has been rising. At the same time, the concentration of atmospheric black carbon (measured in micrograms per cubic meter) has trended downward from about 1963 or 1964 to 2012.

That the overall trend in the consumption of diesel fuel between the years indicated is upward perhaps suggesting the upward trend will continue is disheartening at least it is to me, anyway. The good news, on the other hand, is the notion that “Statewide Annual Average [Black Carbon]” concentration is on the decline.

Explains ARB in the release: “The [Statewide Annual Average BC] reductions occurred during a time when diesel fuel consumption increased by about a factor of five, attesting to the effectiveness of [California] ARB regulations requiring cleaner fuels and vehicle technology.”

It is indeed encouraging that concentration of black carbon in California over the years has trended downward. But statewide diesel consumption having done the exact opposite and irrespective of the state “Atmospheric Black Carbon Concentration” trajectory, I’m just not so sure continued growth in “Diesel Fuel Consumption” is necessarily a good thing. What I’m thinking is less diesel fuel consumption, proliferation of alternative technologies’ and fuels’ use or even of fuel blends and fuel additives to produce even greater emissions reductions is more the way to go.

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