US carbon emissions from gas to surpass coal
Despite gas being a cleaner-burning fuel higher demand has boosted pollutants
This year US carbon dioxide (CO2) emissions from burning natural gas will surpass those from coal for the first time in almost half a century.
Energy-related emissions from natural gas are expected to be 137m tonnes higher than those from coal this year, reaching 1.506bn tonnes, according to the Energy Information Administration (EIA).
This will be the first time that emissions from natural gas will be higher than coal's since 1972, the EIA said.
Last year emissions from burning natural gas were around 0.4% below coal's, at 1.48bn tonnes.
The rise in gas-related CO2 emissions this year is down to surging demand for the fuel from the power sector, while coal use is falling. This is despite gas emitting around 82% less CO2 than coal does.
Burning natural gas releases around 52m tonnes of CO2 per quadrillion British thermal units (qd Btu), whereas coal releases around 95m tonnes/qd Btu. Oil is around a third less polluting, emitting 65m tonnes of CO2/qd Btu.
This year emissions from oil are expected to rise by around 0.6%, reaching 2.297bn tonnes. Oil accounts for a larger share of US energy-related CO2 emissions because the country consumes more of it, particularly in the transport sector.
Last year total energy-related CO2 emissions fell by almost 3%, down to 5.262bn tonnes. This year they are expected to fall by a further 1.5%, down to 5.184bn tonnes.
Despite US natural gas consumption being 81% higher last year than coal consumption, both fuels emitted around 1.5 billion tonnes of energy-related CO2.
In 2015, gas demand increased more than any other energy source, comprising 29% of the country's total primary energy consumption.
Coal accounted for 16% of total US primary energy use in 2015, down from 18% in 2014. Coal consumption, which declined by more than 12% in 2015 alone, is now at its lowest level since 1982, the EIA said.
Gas demand has surged particularly from the power sector. In 2015 gas overtook coal as the country's top fuel for power generation while the sector's demand for reached its lowest level since 1987.
The country's Clean Power Plan has helped to boost its use of natural gas in the power sector while phasing out coal.
On 21 July US consumption of natural gas for power generation reached its highest ever daily level, at 40.9bn cubic feet per day .
Nine of the 10 highest US power burn days on record occurred in July this year. Average US gas consumption in the power sector was 2.7bn cf/d higher in July, than a year earlier, reaching 36.1bn cf/d. That's 1.5bn cf/d above the previous high set in July 2012.
The US' total energy-related carbon emissions have fallen by around 10% over the past decade because of a rise in both gas consumption and higher use of lower carbon fuels.
This is partly because the country uses less coal than a decade ago and partly because low carbon fuels such as nuclear power and renewable energy now make up a higher proportion of the country's energy mix.
EIA data show that in 2014 energy-related emissions from coal were 447m tonnes lower than a decade earlier, at around 1.713bn tonnes. Emissions from oil were 346m tonnes lower in 2014 than in 2004, falling to 2.252bn tonnes.
Meanwhile, CO2 emissions from natural gas were around 234m tonnes higher over the same decade, reaching 1.434bn tonnes in 2014.
Two of the largest factors in year-to-year fluctuations in energy-related CO2 emissions are economic growth and the weather, the EIA said. Over the past decade the largest fall in energy-related CO2 emissions occurred in 2008-09 during the global economic downturn.
Changing weather patterns are also expected to drive US gas consumption higher throughout the coming winter months.
El Niño periods were typically bearish for gas prices because they bring warmer winters to the north and wetter rainy seasons in the west. But La Niña usually brings hotter summers in the north, spurring people to switch on the air conditioning, and stormier hurricane seasons that disrupt supplies followed by colder winters.
As US domestic gas production has soared over the past decade, prices have tumbled, also helping to boost consumption.
US gas prices have averaged around $4.65/m Btu over the past decade, down from a high of $13.40/mBtu in 2005.
By mid-June, the Henry Hub benchmark had risen from its late winter lows of less than $2/m Btu to $2.55/m Btu, its highest level in more than six months. Tightening stocks have bolstered prices after years of a glut.
And by mid- August futures had rallied further, trading around $2.68/mBtu as a combination of rising consumption and depleting stocks are expected to tighten supply ahead of winter.