Transportation tops Maine greenhouse gas emissions

Cars, trucks and other vehicles used for transportation were responsible for most of the greenhouse gas emissions in Maine in 2017, according to a report released by state environmental regulators this week. Maine's transportation sector has emitted more greenhouse gases than any other sector every year for at least two decades, according to state data, and is the only tracked sector whose greenhouse gas emissions have increased since 1990.

A 2003 state law established a series of greenhouse gas reduction goals for Maine. The law set a target to reduce greenhouse gas emissions within the state, by 2010, to the levels of emissions recorded for 1990; to reduce emissions to 10% less than 1990 levels by 2020; and in the long term, "reduction sufficient to eliminate any dangerous threat to climate." The 2003 law required the Maine Department of Environmental Protection to issue a report every 2 years on progress toward these goals.

In 2019, the Maine State Legislature enacted An Act To Promote Clean Energy Jobs and To Establish the Maine Climate Council, which replaced these goals with requirements that Maine reduce its gross annual greenhouse gas emissions to at least 45% below the 1990 gross emissions level by 2030, and to at least 80% below 1990 levels by 2050. The 2019 law requires the Department of Environmental Protection to adopt rules to ensure compliance with these levels, and authorizes the Department of Transportation to adopt similar rules.

On January 13, 2020, the Maine Department of Environmental Protection issued its Eighth Biennial Report on Progress Toward Greenhouse Gas Reduction Goals. The report shows that Maine’s electric sector has largely been decarbonized, while transportation and heating remain laggards.

As it has for decades, transportation dominates Maine’s greenhouse gas emissions at 54% of the total, because nearly all vehicles burn gasoline or diesel. Homes are the second-largest emitters, contributing 19% of the total, mostly by burning oil for heating. Commercial businesses (11%) and industrial businesses (9%) contribute relatively smaller shares.

Meanwhile electric power generation contributed just 7% of Maine’s CO2 emissions in 2017 (down from 9% in 2015). As Figure 7 from the Department's report shows -- reproduced below -- no sector has cut its carbon emissions by a greater percentage than the electricity sector, while transportation stands out for its dominant and growing share of emissions.

Figure 7, Maine Department of Environmental Protection Eighth Biennial Report on Progress Toward Greenhouse Gas Reduction Goals

The 2019 legislation also created the Maine Climate Council to advise the Governor and state Legislature on ways to mitigate the causes of, prepare for and adapt to the consequences of climate change. Governor Janet Mills also issued an executive order calling for Maine to be carbon neutral by 2045. Achieving these goals will require substantial focus on decarbonizing Maine's transportation sector.