Can early-stage technologies such as carbon capture, – and planting trees – really suck enough carbon from the air to help us reverse global temperature rise?

The challenge we face

The greenhouse gases already in the atmosphere will push global temperatures to about 2.3 degrees Celsius of warming since pre-industrial times, according to a recent paper in  the journal Nature Climate Change.  That’s if we were to stop all emissions today.

This correlates with other studies and the opinions of many climate scientists.

But it’s complicated to estimate with any accuracy, because of the many assumptions and variables. For example about how soon we can stop emissions of greenhouse gases – and which ones, for example, methane, have a shorter life in the atmosphere than carbon dioxide?

This is why some scientists think that attaining a “peak” rise of 1.5oC, in line with the Paris Agreement, is still possible, before temperatures begin to subside.

How realistic is 1.5oC?

If I were a gambler, I wouldn’t put money on it.

Let’s face it, with fossil fuel producing countries like Australia – and companies like Exxon – still digging their heels in; with blockchain on the rise and using the energy of a medium-sized country; with agriculture a long way from significant reversals of land use change and ruminant methane emission management; and with various positive feedback loops such as Arctic tundra melting releasing huge quantities of methane, it is looking extremely unlikely.

Yet the International Energy Agency’s most recent report argues optimistically that net zero by 2050 remains possible, because its proposed solutions include carbon capture, utilisation and storage (CCUS).

That is, capturing greenhouse gases from many sources including industry and energy production as well as direct air capture.

But these technologies are not yet widely cost-effective, and are some way off being scaleable.

G7 signs up to CCU

Nevertheless, G7 leaders, meeting earlier this month, just after the report’s publication, committed to accepting its recommendations, and more.

They promised to reach net zero carbon emissions by 2050 at the latest, with deep emissions reduction targets earlier on in this decade.

All the G7 members signed up to the global “30 x 30” initiative to conserve or protect at least 30 per cent of the world’s land and at least 30 per cent of the world’s ocean by 2030, and committed to 30 x 30 nationally.

They pledged to end all new finance for coal power by the end of 2021, and increase support for clean energy alternatives like solar and wind.

It was also agreed to accelerate the transition away from unabated coal capacity and to an overwhelmingly decarbonised power system in the 2030s.

This left Australia and Canada looking like the dirty dogs of developed countries.

Yet even supposing these fine words were to be matched by real action, there remain many questions.

The challenge ahead

The proportion of global greenhouse gas emissions due to energy and transport is about 76 per cent. That is what’s covered by the IEA report.

When all sources of greenhouse gas emissions are taken into account – that is, from waste and agriculture/land use change – reaching net zero by 2050 looks extremely challenging. 

Those now scrambling to advocate various means of actively removing carbon from the atmosphere as a way of compensating for our inability to cut emissions will have to prove that the technologies they propose can step up to the mark.

These advocates also include the nine countries whose Paris Agreement-meeting strategies submitted by August 2020 include a role for CCUS: Canada, France, Germany, Japan, Mexico, Portugal, Singapore, the United Kingdom and the United States; and the Australian government, which a year ago announced CCUS would be eligible for existing funding programmes for clean technologies.

Over a fifth of global oil and gas production has also made 2050 net-zero commitments, with CCUS involved in every case. For example, Dalmia Cement, Heidelberg Cement and steel-maker ArcelorMittal are companies pursuing CCUS to meet their goals.

Currently, only 40 million tonnes a year of CO2 is stored globally via CCS — a fraction of the world’s total annual emissions of 36 billion tonnes.

Let’s look at some of these proposals to capture carbon.

Planting trees

Trees absorb carbon dioxide as they grow. They have long been planted as part of carbon offsetting schemes.

Countries are now pledging to plant thousands more hectares with trees to tackle both the climate and nature crises.

So how much land needs to be planted with trees to stop climate change?

According to the Grantham Institute for Climate Change and the Environment at Imperial College London’s Dr Bonnie Waring, “Forests are complex ecosystems, and poorly planned planting efforts can actually increase the amount of carbon dioxide (CO2) in the atmosphere and increase global warming”.

Therefore they need to be planted and managed correctly, she says, and this blog post details some successful and unsuccessful projects financed by big companies.

About two-thirds of land on earth could support trees, Waring says, but much of it is currently used for agriculture.

Waring has calculated that “a massive effort to promote forest regeneration or plant trees on non-croplands across the globe could sequester up to 100 gigatonnes of carbon, an amount equal to 10 years of man-made carbon emissions at current rates.

“Yet it would take these new forests about a century to capture this quantity of carbon.”

And we don’t have that much time. So, although it’s good if we do it right because of the other ecosystem benefits forests provide, we can’t just rely on planting trees to get to net zero.

Direct air capture

This technology involves literally sucking the air through a process that removes and chemically solidifies the gas in a mineral form similar to the formation of lime and concrete, forming compounds with other elements such as calcium, called sorbents.

Another Senior Research Fellow at the Grantham Institute, Dr Ajay Gambhir, says of most touted carbon removal technologies, “Some are just unicorns; they don’t exist… or we haven’t discovered them yet, but direct air capture is different.”

Some carbon removal strategies are just unicorns: they don’t exist… or we haven’t discovered them yet; direct air capture is different, but it comes at a steep price

He thinks direct air capture is feasible, but it comes at a huge price: the machines use a large amount of energy and the sorbents can cause environmental damage in their manufacturing.

“Our study shows that by the end of the century, direct air capture could require the equivalent of over half of today’s global energy needs if it is the dominant carbon dioxide removal technology,” he says.

He and his co-authors of a recent scientific paper on the topic, emphasise that direct air capture cannot replace action to immediately cut greenhouse gas emissions, but at best, it can complement our efforts to achieve the Paris Agreement goals.

A circular economy of fizziness

Nevertheless, companies are backing the technology. Bill Gates has recently added Climeworks to his portfolio and Carbon Engineering has plans to build a 1 million ton per year plant by 2024. This, it asserts, is 250 times larger than the current largest built so far.

Some of these plants are financed by offsetting deals, for companies like Microsoft willing to pay to offset their unavoidable emissions, other plants will sell their carbon dioxide to manufacturers of fuels or carbonated drinks.

If the gas is used to make fuels, there will be climate consequences – the gases will still end up in the air.

If used in drinks, those bubbles will also escape. Yes, they may replace other bubbles, in a sort of circular economy of fizziness, but they will warm the planet unless they’re kept safely in their bottles and cans.

In both cases, at best they will approach climate neutrality. But utilisation won’t result in net reductions of atmospheric carbon.

Carbon capture and storage

To do this, we have to bury the captured gases.

Taking carbon dioxide from the chimneys of fossil-fuel burning power stations and industrial plants and burying it underground has been around as a pilot-stage dream for about 20 years, and is just about cost-effective enough nowadays to be adopted in some commercial situations – at a cost passed on to consumers.

For this to happen at scale, though, a higher price for carbon – a tax – would be required, of at least $50 a tonne. The EU’s current carbon price is €46 per tonne.

The IEA has documented 30 new integrated CCUS facilities that have been announced since 2017, costing $US 27 billion, with most in the United States and Europe, but some also planned in Australia, China, Korea, the Middle East and New Zealand.

If all went ahead, global CO2 capture capacity would triple, to around 130 Mt/year, a tiny fraction of what is required (see this discussion of the remaining carbon budget).

Increasingly popular are the development of industrial CCUS hubs with shared CO2 transport and storage infrastructure, such as the one envisaged in Humberside, UK.

This is at the mouth of the river Humber, around a cluster of highly carbon-intensive industries. The project intends to deploy carbon capture usage and storage under the North Sea in old gas fields, and low carbon hydrogen technology to preserve jobs by enabling energy intensive industries to continue to operate and thrive.

And this is the point of all these projects: to let carbon emitters carry on as at present.

So what’s the overall verdict on CCUS?

Let’s end with the verdict of Mike Childs at Friends of the Earth UK, quoted in the Financial Times. “On a list of priorities for spending money, CCS would be at the bottom,” he says.

He favours first massively ramping up renewables, investment in hydrogen, and improving energy efficiency.

To which we can add repairing soils and ecosystems, and becoming less reliant on meat products.

CCUS is analogous to treating heroin addicts with methadone. It allows addicts to function but doesn’t remove the base cause of the problem, the dependency.

For dependency to end, a managed withdrawal from the drug is usually preferable to enforced cold turkey.

Unless we can wean ourselves off fossil fuels this decade, we may be left with no choice but to go cold turkey. Then again, addiction does sometimes unfortunately end in the death of the subject.

David Thorpe is the author of ‘One Planet’ Cities: Sustaining Humanity within Planetary Limits and Director of the One Planet Centre Community Interest Company in the UK.

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  1. Forestry – yes please (but don’t sell the offsets) and there just isn’t enough viable land to reafforest to catch up with our overshoot on emissions. Direct air capture – utterly absurd trying to use expensive energy to overcome the entropy of 400ppm CO2. Even if renewable energy is used, this SHOULD be going on the grid to displace fossil fuel electricity first. And DAC is only capture with no final destination – currently pumped into oil wells to maximise extraction of marginal oil – gun see foot pull trigger. Injection into basalt rock does store permanently. But there’s a MUCH simpler, cheaper, better way. Grind up massively abundant basalt sprinkle it on the sea where it will take up the dissolved CO2 where it is 17 times more concentrated than in air. Carbonates will deposit on the ocean floor mimicking natural weathering of alkaline minerals. Then the oceans can dissolve more CO2 from the atmosphere. At the same time raising ocean pH helps protect corals and crustaceans from the acidifying effect of dissolved CO2. Win on cost, win on permanent solution, win on acidification, win on ocean currents doing the hard work of entropy. BUT all geoengineering ideas are highly risky so it needs thorough research first – it may prove to be a mad idea!