Per unit of electricity generated, natural gas is the lowest-carbon fossil fuel. Producing a kilowatt-hour (kWh) of electricity using oil, and especially coal, generates significantly more emissions. While bituminous coal produces about 370g of CO2 per kWh, oil produces about 260g, and natural gas produces about 230g.
In the results of a two-year study, released today, the researchers said electric utilities and other sectors of the American economy will use more gas through 2050. Under a scenario that envisions a federal policy aimed at cutting greenhouse gas emissions to 50 percent below 2005 levels by 2050, researchers found a substantial role for natural gas.
“Because national energy use is substantially reduced, the share represented by gas is projected to rise from about 20 percent of the current national total to around 40 percent in 2040,” said the MIT researchers. When used to fire a power plant, gas emits about half of the carbon dioxide emissions as conventional coal plants.
They claim that nuclear power, renewable energy and carbon capture and sequestration are all more expensive than gas, and thus less viable as low-carbon alternatives. They also claim that by 2050, 15% of the U.S. vehicle fleet will be fueled with natural gas.
I have three big objections to all this:
First, an increasing share of natural gas is coming from unconventional sources, using techniques like hydraulic fracturing. This has associated environmental risks, such as the contamination of groundwater.
Secondly, the amount of climate change humanity will cause depends on the total amount of all fossil fuels burned before society becomes carbon neutral. Burning more gas obviously contributes to this cumulative total, changing the atmosphere and climate in ways that will endure for thousands of years. If humanity ever starts to burn the methane embedded in permafrost of methane clathrates, the total quantity of associated emissions could be very worrisome indeed.
Thirdly, building new gas-fired power plants perpetuates fossil fuel dependence. It keeps us wedded to fuels that are inevitably going to become ever more costly and destructive to access, and which can never form the basis for a truly sustainable society.
None of this is to say that gas has no role to play in dealing with climate change. In the short term, substituting gas for coal may be a promising way to reduce emissions during the transitional period before renewables become dominant. In the long run, however, there is no alternative to moving beyond fossil fuels.
Helpfully, the MIT report does not just take energy demand as constant, or ever-increasing. Rather, they model the economic effect of putting a price on greenhouse gas emissions, and find that doing so would keep demand flat in the next few decades. They project that carbon pricing would raise electricity prices by 30% by 2030 and 45% by 2050 – a small price to pay for reducing the extreme risks associated with climate change.