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.