(The opinions expressed here are those of the author, a
columnist for Reuters.)
By John Kemp
LONDON, July 31 Supporters of natural gas
promote it as a clean "bridge fuel" between the coal-and-oil
dominated energy system of the present and the zero-emissions
system of the future based on renewables and nuclear power.
Burning gas rather than coal in a power plant produces
roughly half the carbon dioxide emissions and sharply reduces
airborne pollution from mercury and other heavy metals.
Switching to gas from coal could therefore slow the rise in
global temperatures as well as produce significant health
Shifting to gas is at the heart of the U.S. Environmental
Protection Agency's (EPA) proposed new rules for power plant
But gas is only more environmentally friendly if it is
produced, transported and burned carefully, without too much
leaking into the atmosphere.
Processed natural gas is almost entirely methane, which has
a global warming effect more than 20 times more potent than
carbon dioxide, according to the Intergovernmental Panel on
Climate Change, so leaks are a big problem.
Methane accounted for almost 9 percent of U.S. greenhouse
emissions in 2012, according to the EPA, making it the
second-largest contributor to climate change after carbon
dioxide. ("Inventory of U.S. greenhouse gas emissions and sinks
1990-2012" April 2014).
The Obama administration's Climate Action Plan, therefore,
contains a separate "Strategy to Reduce Methane Emissions",
published in March 2014, designed to tackle the problem.
The administration's methane strategy is a mixture of
practical and political. On a practical level, the global
warming effect from methane emissions is too large to be ignored
and could get worse as gas becomes an increasingly important
fuel in the next few decades.
Methane leaks from natural gas wells and pipelines are also
associated with leaks of other heavier volatile organic
compounds, which are a significant cause of air pollution.
But the White House also has a political motivation in that
it is backing gas as a cleaner alternative to coal.
Some green groups question whether gas really is cleaner,
given the leaks into the atmosphere and its greater potency as a
Precisely how much methane is leaking into the atmosphere is
fiercely disputed. Some green researchers claim enormous
quantities are being released, especially from shale wells.
("Bridge to nowhere: methane emissions and the greenhouse gas
footprint of natural gas", April 2014)
Others are more sceptical, suggesting that if so much gas
were really being lost, it would have created combustible clouds
over oil and gas fields and led to frequent explosions.
In fact there is not really enough evidence to reach a
definitive conclusion, because comprehensive survey data have
not been collected.
But there is a political imperative for the White House to
be seen to be taking the issue seriously to keep the support of
prominent environmental groups for its renewables-plus-gas
strategy for combating climate change.
Agriculture and forestry accounted for almost 40 percent of
anthropogenic methane emissions in the United States in 2012,
according to the EPA.
Methane emitted from enteric fermentation (the digestive
systems of cattle) is estimated to account for 25 percent of all
U.S. methane emissions.
To put that in context, it is the equivalent of 141 million
metric tonnes of carbon dioxide (2 percent of all greenhouse
emissions from all sources).
Other major sources of methane emissions come from manure
management, forestry and rice cultivation.
But farmers are a politically powerful group the White House
cannot afford to offend. Besides, there are currently no easy
ways to tackle enteric and manure-related emissions.
"This strategy addresses emissions from agriculture
exclusively through voluntary actions, not through regulations,"
the White House emphasised when it was launched.
With farming off limits, the methane strategy focuses on
three other sources: gas and oil systems (28 percent of all
methane emissions), landfills (18 percent) and coal mining (10
The administration has promised to introduce new standards
or rules for petroleum, landfill and coal mining systems, using
its powers to regulate air pollution (via the EPA) and
activities on public lands (via the Bureau of Land Management).
Cutting fugitive emissions from the oil and gas systems has
emerged as the priority for the White House as well as for
Of petroleum-linked methane emissions, three-quarters of
emissions come from natural gas production, transportation and
distribution, with the rest from the oil industry, according to
"Within the natural gas industry, approximately 31 percent
of this methane came from production sources, 15 percent from
processing, 34 percent from transmission and storage, and 20
percent from distribution," the White House claimed in its
"As our use of natural gas in manufacturing, transportation
and power generation increases - creating jobs, reducing costs,
cutting carbon pollution, and reducing dependence on foreign oil
in our nation - we must continue to ... reduce methane emissions
from this vital sector of our economy."
Almost half of fugitive emissions come from the production
and initial processing stage, so this has emerged as an early
focal point for the administration's efforts.
A large proportion of the fugitive emissions from gas wells
are thought to occur during the initial "flowback" period,
lasting perhaps ten days after a well has been hydraulically
fractured, when natural gas mixed with fracking water comes to
If the methane is not captured during this period, before
the well is hooked up to the gas-gathering system, large
quantities of natural gas are lost to the atmosphere.
Environmentalists are pushing for companies to use "green
completion" techniques, which capture substantially all this
Gas producers have a strong commercial incentive to use
green completions, since they capture valuable output, and many
are doing it voluntarily. The federal government also is moving
to require green completions for wells drilled on public lands
and perhaps eventually for all wells.
For its part, the U.S. Department of Energy has agreed to
help overhaul the U.S. transmission, storage and distribution
systems with new efficiency standards and research. ("Department
of Energy announces steps to help modernize natural gas
infrastructure" July 29)
The Energy Department has also recommended to the Federal
Energy Regulatory Commission (FERC), an independent regulatory
agency the administration does not directly control, that it
should find ways to help gas transmission companies invest in
leak detection and reduction by giving them more certainty that
they will be able to recover the costs from pipeline users.
Cutting fugitive emissions from trunk pipelines, storage
facilities and local utility networks is set to be a major
feature of the first Quadrennial Energy Review promised for
Being seen to control leaks from the production and
transportation of natural gas is essential to maintaining the
political consensus that gas is a "clean" fuel that will play a
big positive role in countering global warming.
(editing by Jane Baird)