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Is LNQ friend or foe?
The BC government has recently reached an agreement to allow the
construction of a liquefied natural gas processing and export facility in
Kitmat
The discussion about the project has been a bit similar to the site C
discussion. Some mention the economic advantage, others mention local
environmental risks. As with the site C, I think that is missing the
point. I think we have to focus on the transition to renewable energy
sources and the climate change impact.
The
bc
green party argument
is at least focused on green house gasses emissions. But it
doesn't look at what LNG might be used for.
According to the lngcanada's website, a target market is Asia, where
the gas would be used as a replacement for coal. Since the gas
production would be in BC and the coal power plants are not, I think
it is important to look at the global balance, not just the BC
emissions.
It is clear that LNG is not a renewable energy source. But if it is
better than sources like coal, we should consider the possibility that
it is a useful tool for the transition. Is it better to burn gas
instead of coal while renewable sources come online?
Lets first look at the difference in emissions by burning gas instead
of coal. Natural gas is mostly methane, which is the simplest
hydrocarbon with a formula \(CH_4\). The first thing to notice is
that the atomic mass of carbon is 12, while that of hydrogen
is 1. That means that even the simplest hydrocarbon is \(12/16\)
or \(75\%\) carbon by mass.
As for \(CO_2\), the atomic mass of oxygen is \(16\), which
means that the the mass of \(CO_2\) is \(2*16 + 12 =
44\). So \(CO_2\) is \(12/44\) or \(27\%\) carbon by
mass.
The
available
energy from burning methane is \(50\) MJ/kg. Since we are
interested about the produced CO2, the energy content is \(50/0.75\)
or \(66\) MJ/kg of carbon. For high grade coal it is \(32.50\)
MJ/kg. This quick calculation matches the
claim that per KWh natural gas produces half as much CO2 as
coal.
So we have that each Kg of carbon from LNG used in electricity
generation saves one Kg of carbon in the atmosphere. Given their
atomic masses, a Kg of carbon is present in \(16/12\) Kg of
methane and \(44/12\) Kg of \(CO_2\). So it looks like burning
1 Kg of methane produces (and saves) \(44/16 = 2.75\) Kg of
\(CO_2\).
The proposed Kitmat project is expected to produce \(14\) mega
tonnes (\(1.4*10^{10}\) Kg) per year of LNG. The estimates on the
green house emissions per year range from \(3.4\) to \(10\)
mega tonnes of \(CO_2\) equivalent. That is surprisingly
inefficient. The reason for the inefficiency seems to be that methane
is, over a \(100\) years time frame, \(20\) times worse than
\(CO_2\) for global warming. So a small leak (\(5\%\) say)
dwarfs other production problems.
Even taking the \(10\) mega tonnes \(CO_2\) equivalent number,
it would seem that if the LNG is used to replace coal than the project
would still save \(14*2.75 - 10 = 28.5\) mega tonnes equivalent
per year.
The total emissions from the project are \(14*2.75 + 10\) mega
tonnes of \(CO_2\) equivalent. That is, \(4.85 * 10^{10}\)
Kg. Given the \(50\) MJ/Kg heat of combustion and a \(50\%\)
efficient generator, the total electricity that can be generated per
year is \(1.4*10^{10} * 50*10^6/2 = 3.5*10^{17}J\) or \(9.72
*10^{10}\) KWh. So the emissions are about \(499\) g/KWh according
to this estimate.
The above leaves out transportation inefficiency for gas, but coal
mining has its
own problems too.
A much more
detailed
paper using data from actual power plants when looking at whether
the US should export LNG arrived at \(655\) g/KWh \(CO_2\)
equivalent. That would still be saving \(550\) g/KWh of electricity if
replacing coal according to the same paper.
LNG is a much more complicated case than site C, but it seems that LNG
can be an useful short/medium term tool for reducing emissions. It is
just important be careful on how much methane is leaked.
This also creates an interesting accounting problem on the carbon
market. BC should receive credit if it lowers emissions in Asia. The
same authors seem to have a
paper on the subject
One last thing that I still agree with the greens is that the project
should not be subsidized. If the above analysis is correct, there
should be plenty of demand for LNG and a subsidy is just giving away
free money.