The world will find it difficult to completely eradicate fossil fuel use. By 2050 some sources see a minimum of 5 billion tonnes of CO2 emissions, down from about 50-55 billion tonnes today. We therefore need to develop a series of technologies for capturing carbon dioxide and permanently storing it in order to achieve ‘net zero’.

Several industries, such as oil extraction, find it difficult to envisage how they might completely abandon their core activity. They have usually suggested, often in the vaguest possible terms, that they could offset the remaining emissions by planting woodland. As it grows, a tree takes in CO2, although this will gradually return to the atmosphere after it dies. Even rapid reforestation across millions of square kilometres is unlikely to fully compensate for the greenhouse gases produced by burning oil. The world needs a much wider variety of different carbon capture technologies.

Stripe and the CO2 capture challenge

Stripe is a payments processing business based in San Francisco. Valued at tens of billions of dollars, it is a world leader in providing robust systems for handling the transfer of money and financial obligations.

In the autumn of last year, it asked for bids from entities offering robust greenhouse gas collection and storage. Stripe said it would pay a total of $1m to the best schemes. It got responses from 24 different companies and research teams around the world and awarded four a quarter each of the funding on offer. May 2020 saw the award of the cash.

These 24 offers illustrate the wide range of possible negative emissions technologies. In an extremely helpful move, Stripe published details of each bid. (See ‘Source Materials here . I split them into ten different categories.

Type of CO2 capture and/or storage + brief description

Soil carbon improvement (4 bids)

Global soil contains about 1.5 trillion tonnes of carbon, far more than is present in vegetation. Modern agriculture and deforestation is tending to reduce the carbon content of soil. Measures to regenerate carbon in soil can result in very long term carbon capture.

Bio-energy with carbon capture and storage (BECCS) (1 bid)

Wood and other organic matter captures CO2 as part of the photosynthetic growth process. If the material is then burnt, perhaps to generate electricity, and the the resulting CO2 is then captured and stored, the lifecycle results in negative emissions.

Woodland Maintenance (2 bids)

Keeping a wood that would otherwise be cut down will, in effect, store carbon.

Reforestation (2 bids)

Putting forests back in areas where they have been lost.

Afforestation (2 bids)

Creating forests in places that currently do not carry trees.

Olivine weathering (2 bids)

Olivine is a rock that naturally absorbs CO2. Large volumes exist and it can be ground into small specks to speed up the permanent capture of carbon.

CO2 capture in building materials (5 bids)

Several building materials either naturally retain CO2 (such as structural bamboo) or can be altered to permanently capture more of it (such as concrete)

Direct Air Capture of CO2 (1 bid)

Although CO2 is only a tiny fraction of the world’s atmosphere, it can be separate out and then stored.

Biochar/Bio-oil (4 bids)

Heating organic material to high temperatures in the absence of air will break it down into gases, oil and nearly pure carbon. The oil and the carbon can be stored permanently in the top soil or deeper.

Ocean storage (1 bid)

The bidder proposed to bring up water from the deep ocean to the surface. Plankton growth will be encouraged (which absorbs carbon from the sea water) and then the water will be returned to the deep. There, the plankton will die and store the carbon on the ocean floor.

The winning bids were from the Olivine, CO2 capture in building materials, Direct Air Capture and Biochar/Bio-oil sectors. No money was awarded to forestry or soil carbon offerings, even though some of these bids were substantially cheaper than the winners in terms of cost per tonne of CO2.

The winners

Climeworks, the Swiss company which has done the most to bring Direct Air Capture into consideration, runs a plant in Iceland which captures CO2 from the air and then injects into deep basalt, permanently absorbing it. Its technology is currently expensive and it will be paid over $700 a tonne for just 322 tonnes of collection and storage. Climeworks says that the potential of its technology for storing CO2 is almost limitless.

Canadian company CarbonCure has a technology for injecting CO2 into concrete before it sets. The carbon dioxide is permanently stored and actually makes the concrete stronger. Carbon Cure estimates a worldwide potential for its group of technologies of about 500 million tonnes a year, about 1% of world greenhouse gas emissions. The company asked for $100 a tonne and agreed to absorb 2,500 tonnes.

Project Vesta will grind up olivine and leave the sand on beaches where it will be weathered by the CO2 in the air. Its says its approach is cheap, requiring a payment from Stripe of only $50 a tonne today. Project Vesta says that olivine weathering could permanently store tens of gigatonnes of CO2 per year since the rock exists in large quantities around the world.

Charm Industrial takes waste biomass, such as shells from farmed nuts, and puts it through a pyrolysis process. A carbon-rich oil is one of the outputs. This can be injected into depleted oil wells where it will be permanently stored. This is currently an expensive process and the company offered to sequester CO2 at $600 a tonne. Charm Industrial claims that its process might be able to store 7 billion tonnes of CO2 in 20 years. However it is still at an early stage in its development.

The bidding process bought Stripe just over 6,500 tonnes of negative emissions at an average price of about $150 a tonne. All four seem very convincing processes. I was slightly surprised to see that all the projects backed by Puro, a highly plausible Finnish operator of an auction system for CO2 storage, failed to get backing from Stripe.

How much will carbon capture and storage cost?

The simple average of the 24 bids to Stripe was $177 per tonne. Participants generally expect very significant reductions in cost, projecting a figure of just $37 a tonne in 20 years time (Simple average). Let’s put these numbers into context.

$177 a tonne – total cost to neutralise 50 billion tonnes of 2020 emissions – about 9% of world GDP

$37 a tonne – total cost to neutralise 10 billion tonnes of 2040 emissions – about 0.4% of current world GDP

Of course the 2040 numbers may be absurdly optimistic. Some - such as the $10 estimated by Project Vesta for olivine weathering - do look highly ambitious. But even at an average figure of $100 a tonne that I suspect may be more reasonable, the costs of storage of 20% of today’s emissions are only about 1% of the world’s economy. This is manageable.

What other lessons should we learn from the Stripe call for bids?

A promise of $1m of funding brought forward 24 bids, most of which seem potentially effective. We need other entities (companies, governments, charities, philanthropists) to go through the same process, encouraging and developing the nascent carbon storage industry. By the way, conventional CCS, particularly on power stations, looks far more expensive than the bids we have just seen.

My first guess is that regenerative agriculture needs active sponsorship to show whether, and at what rate and with what degree of permanence, it can add carbon to the soil. Slightly surprisingly, none of the four offers in this ‘auction’ won funding. I think a prize specifically for soil carbon storage would be particularly beneficial.

Many congratulations to Stripe on carrying out this vital and highly productive task.