Jeff Gibbs and Michael Moore didn't say much about LNG (liquified natural gas) in their inconvenient documentary Planet of the Humans.
But LNG has been one of the spectacular winners in the "anything but coal [and nuclear]" mindset of international climate change campaigners. The expansion of gas production over the past 20 years has been has been globally spectacular and LNG has made it readily exportable. You can see that growth in oil and gas has outstripped growth in wind and solar, particularly over the past few years.
Australia has joined the boom. We now have 11 massive LNG projects each producing more than a million tonnes of LNG per year (and many more smaller ones). We are the world's biggest exporter of LNG.
Our two biggest projects each produce about 16 million tonnes of LNG per year. Gorgon in Western Australia is one of these. It was begun in 2009 as a AU$57 billion project which ended up costing AU$88 billion by the time it produced it's first LNG for export in 2016.
Natural gas is just methane ... it's a fossil fuel and we need to get rid of it. But the stupidity of emission targets meant that we were happy to expand it's production because it was an improvement on coal. That idiocy has left us with vast projects which have to be stranded at massive financial cost. The way engineers solve problems is very different to the way politicians and climate change campaigners have gone about it. Engineers typically design a system that will work and then build it. They don't say, "Oh, this terrible system is better than that terrible system, so lets build it!" ... which is the kind of dumb thinking encouraged by markets and emission targets.
Here's a picture of the Gorgon on-shore processing plant. It's built for a 60 year life span but will have to be trashed when we eventually take climate change seriously.
This LNG processing plant is about 200 hectares of steel and concrete. 200 ha is about 1/4 the size of Melbourne's Tullamarine airport. So it's big ... but not that big.
We export Gorgon's output. It's part of our world leading 66 million tonnes of exported LNG in 2018. Ross Garnaut has been selling plenty of books recently spruiking Australia becoming an energy superpower by exporting clean energy instead of dirty stuff ... like LNG and coal.
To replace LNG with clean energy, the obvious choice would be ammonia. You can put it in supertankers, just like LNG, but it's much easier to ship than hydrogen.
So the plan (CSIRO are working towards this) is to use wind and solar power to make ammonia and then export it.
Let's run the numbers on replacing Gorgon's 15.6 million tonnes of LNG annually with ammonia generated by solar farms.
I'll use Nyngan solar farm as my unit of measurement. Nyngan is about 250 ha and generates about 233 gigawatt hours of energy annually. So the land requirement is similar to the Gorgon processing plant.
But what about the output? A tonne of ammonia has about 1/3 the thermal energy of a tonne of LNG (5.1 MWh compared to 14.9 MWh). So instead of just pulling 15.6 million tonnes LNG out of the ground, we have to make 15.6 x 14.9/5.1 = 45.5 million tonnes of ammonia with solar electricity. Currently it takes about 11 mega watt hours to make a tonne of ammonia, but the CSIRO reckon they can get that down to about 8.5 megawatt hours.
The rest is very basic arithmetic ... the number of Nyngans we need would be:
(15.6e6 x 14.9/5.1) x 8.5e6/233e9 = 1662.6 Nyngan solar farms covering about 1662 x 250 = 415,665 hectares.
And the cost? Nyngan is a $440 million project ... so building 1662 of them would cost about $731 billion.
Alternatively
How else could we export the same amount of energy as embodied in 15.6 million tonnes of LNG? Well we could export uranium to anybody with a nuclear reactor. How many tonnes of uranium would that take? One tonne of uranium has about the same thermal energy as about 8,075 tonnes of LNG. So we'd only need to produce about 1,931 tonnes of uranium. Which is about half the output of the Olympic Dam mine in South Australia. Olympic Dam is a copper mine, producing about 230,000 tonnes of copper and about 4,000 tonnes of uranium.
N.B.
For those who understand such things the wind and solar figures in the top graph are for electricity and have been multiplied by 2.6 to take this into account.