The carbon footprint of SpaceX

How much greenhouse gas is emitted by a Space X rocket to deliver a Starlink satellite to orbit? How much gas is emitted to take a joyride to the edge of space and back?


Last year saw three billionaires – Richard Branson, Jeff Bezos and Elon Musk – launching the space tourism industry, with all three taking jaunts above the earth.

What sort of greenhouse gas warming can we expect from this?

Unusually, for the actual rocket launch, the CO2 isn’t really the biggest deal here. It’s possible to use rocket fuel without any carbon in it at all – NASA has been using liquid hydrogen for decades, and Jeff Bezos’ rocket used it too. But commercial hydrogen is made in a very carbon-intensive way, although it’s possible to make with zero emissions.

SpaceX’s rockets, on the other hand, have kerosene and methane-based fuels, while Virgin Galactic’s Richard Branson zoomed up with a carbon-based fuel too.

While some of these fuels emit CO2, all of them cause other atmospheric problems. The biggest deal is ozone depletion, which can heat the Earth as well as damaging the ozone layer. The soot, carbon dioxide, water vapour, and nitrogen oxides emitted by the rockets all have a warming effect too.

This is compounded by the altitude the gases are emitted at – a recent preprint (not peer-reviewed) study suggests that 0.22% of the upper stratospheric ozone could be lost from three years of space tourism, which could “substantially offset” the progress done by the Montreal Protocol.

The preprint also suggests that black carbon (soot) in the upper atmosphere from rocket launches could be 500 times more warming than soot emitted at ground level, because of its heat absorbing behaviour in the upper atmosphere.

So it’s hard to untangle rocket launch emissions. We need more research before we can be really definitive, although we know it’s not great. As a ballpark, one researcher has suggested that per person, a space tourism flight is 50-100 times worse for the atmosphere than a long-distance plane flight.

But the proto-greenhouse gases in the rocket’s tank are only part of the picture. It’s worth taking a broader look.

We usually think about carbon emissions in three categories, or “scopes”. Scope 1 emissions are emissions that are directly produced by a company, jurisdiction, or other sort of organisation.

In SpaceX’s case, the Scope 1 emissions are the emissions from the rocket fuel, transporting rockets and SpaceX employees about, and any fuel burned during testing and building.

Scope 2 emissions are caused by a company or jurisdiction’s energy use. SpaceX’s electricity use, from office lighting through to rocket manufacture, count towards these.

Scope 3 emissions are caused by a company’s activity in the wider economy. A computer used by a SpaceX employee would have Scope 3 emissions associated with its manufacture and transport, and so would every other material, tool and service the company buys. This means that Scope 3 emissions are typically much larger and harder to count than Scope 1 or 2 emissions.

When countries and companies talk about emissions reduction, they’re usually focussing on Scope 1 and 2 emissions. But Microsoft is planning to be carbon negative in Scope 1, 2 and 3 emissions by 2030, and the Australian Capital Territory has calculated and is aiming to reduce its Scope 3 emissions too.

Microsoft has nearly 20 times the number of employees internationally as SpaceX (over 180,000 versus around 10,000), and the ACT has more than twice as many citizens as that. If a national capital and a global technology giant can dig through their intricacies well enough to count Scope 3 emissions, a literal rocket science company should be capable of it too.

But SpaceX doesn’t publish its emissions widely. Tesla, Inc., one of Elon Musk’s other ventures, is also surprisingly opaque about the emissions required to build its electric cars – something other electric car manufacturers have been much more open about. And Musk himself doesn’t seem particularly interested in addressing this. In fact, he recently tweeted that corporate environmental and social governance – a common method of reporting and addressing environmental impacts – was “the devil incarnate”.

The other thing worth noting, however, is that while many of us find billionaire space tourism tiresome, we do get a range of other benefits from these rocket launches. Earth-monitoring satellites are the clearest example here – giving us a lot of the very data we use to track climate change.

According to the Australian Space Agency, other benefits include massive technological innovations, communications technology, and scientific exploration.

Whether we like it or not, space tourism is now a part of that picture.

Why is the sky blue? What actually is carbon capture and storage? Why does my vacuum cleaner make that noise? How does bitcoin work? And could Yoda really force push Palpatine?

There’s no such thing as a stupid science question, but sometimes the answers can be tricky to find.

This summer we’ve partnered with ACM for the Summer of science: Ask us anything! Send us your curliest chemistry conundrum, perplexing physics problem or any science question at all and we’ll get our journalists onto the case.

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