Carbon dioxide emissions from the transportation sector areon track to surpass those from electricity generation in 2016, according to newresearch from the University of Michigan Energy Institute.
For seven of the past eight months, the average rate atwhich CO2 is emitted from vehicle tailpipes and other mobile sources hasoutpaced CO2 emissions from electric power plants, research professor JohnDeCicco said in a Sept. 15 technical brief.
"Transportation and electricity generation have longbeen leading sectors for energy consumption and emissions in the UnitedStates," DeCicco noted, adding that this year the two emission trends areexperiencing a crossover.
Emissions from electricity generation have been greater thanthose from transportation since 1979, but both sectors peaked in 2007 and thenlargely converged in 2015, the brief said.
"Just before the recession, CO2 was emitted from powerplant stacks at a rate of 2.5 Pg/y, or petagrams per year while flowing fromcar and truck tailpipes, jet exhausts and other mobile sources at 2.1Pg/y," the brief said. "By last year, however, CO2 emissions from thetwo sectors were essentially tied, both rounding to 2.0 Pg/y."
Energy efficiency improvements and a shift away frompetroleum consumption in sectors other than transportation were triggered bythe oil crisis of the 1970s, the brief pointed out, adding that the CorporateAverage Fuel Economy, or CAFE, standards passed in 1975 augmented theefficiency improvements.
The standards "curtailed what was the largest source ofpetroleum demand and slowed the growth of motor fuel consumption, and itsattendant CO2 emissions, when economic growth resumed and oil pricesfell," DeCicco said. CO2 emissions from electricity production grew withthe economy at a steady pace due to more consumption, he noted.
From 1979 to 2007, electric sector CO2 emissions grew at anaverage rate of 1.8% per year while the transportation sector experienced 1.3%growth per year during the same time period. The research said by 2007,electric sector emissions were 20% higher than those from transportation.
However, the recession that began late that same year causeda decline in all forms of energy use. Additionally, renewable resources likewind and solar gained traction, and a greater supply of natural gas along withlower prices began to displace coal. The "dramatic peak" of world oilprices in 2008, as well as "newly strengthened" CAFE standards andmotor vehicle greenhouse gas emission standards, sped up increases to vehicleefficiency and caused emissions to decline in both sectors, the research said.
The move away from coal helped CO2 emissions from powergeneration fall 20% between 2007 and 2015 even though consumption stayed aboutthe same, DeCicco noted. Fuel demand started rising again after2012, and overall transportation sector CO2 emissions went up 5.4% by 2015.
Current policies like the U.S. EPA's Clean Power Plan willhelp the electric sector continue to reduce emissions, DeCicco said. But ifthat rule is overturned, electric sector emissions are likely to once againoutpace those of transportation, he added.
He also said he expects the Clean Power Plan will be moresuccessful in reducing CO2 emissions from power plants than other policies havebeen in reducing transportation sector emissions. Additional policies will beneeded to curb transportation emissions in the coming decades, DeCicco concluded.