Carbon removal — Part 3: starting with the lowest-hanging fruits

Technological readiness levels of CO2 removal solutions are low and, given the scale required, they will all have very significant effects on our environment that must be assessed.

There is no silver bullet and reaching the CO2 removal targets set by the IPCC itself will therefore be extremely difficult.

Being aware of the challenge, two trends for a roadmap:

• The most technical solutions are also the most expensive and involve the greatest risks. But we’ll need them and must pursue our R&D efforts
• In the meantime, we must begin the actual implementation of more natural solutions: we should start grabbing the lowest-hanging fruits now

Part 1: the CO2 genie is out of the bottle

Part 2: fixing the roof despite a pay cut?

Let’s be honest: the lowest-hanging ones might not be the biggest and still require a ladder…

In the first two parts, we found out that there is already too much CO2 in the atmosphere to keep global warming within tolerable limits and that we will not avoid adding some more. We must then, in order of priority:

• Reduce new CO2 emissions
• Deploy CO2 removal solutions, first to offset the remaining emissions and then to decrease the absolute atmospheric CO2 concentration

However we also realised that CO2 removal solutions are hardly directly economically productive as they consume energy. Whatever the technique, they will represent an effort compared to our current model which does not take into account our impact on natural resources.

But where are we on on the road to large-scale coordinated carbon removal?

CCS industrial projects are not CO2 removal facilities

There are 19 large-scale carbon capture & storage facilities in operation over the world and 32 others are being developed. They roughly capture and store 40 million tons of CO2 (less than 0.1% of emissions which stood at 42 billion tons in 2018). Most of them are in the United States.

Source: The Economist

But, beyond noticing the very modest size of this industry, we must note that:

• On the capture side: in 18 facilities out of 19, the CO2 is captured from the combustion of coal, the separation of methane from CO2 in natural gas or from hydrocarbon-based industrial processes. The current facilities capture carbon atoms that were just extracted from the underground, not from the atmosphere. They just limit new emissions, they do not reduce the CO2 concentration in the atmosphere.
• On the storage side: in 14 facilities out 19, this CO2 is stored through enhanced oil recovery (EOR). This involves injecting CO2 into an already widely exploited oil well to reduce the viscosity of the remaining oil and allow the extraction of volumes otherwise difficult to reach. As the CO2 passes through, it is stored in the emptied well. This CO2 storage also enables new carbon atoms to be extracted from the underground.

The world is only counting 1 large-scale industrial carbon removal project*. The Illinois Industrial CCS fermentation plant in the US produces ethanol from corn* fermentation and stores 1 million tons per year of the resulting CO2 underneath the facility (less than 0.1% of what will be needed by 2050).

*atmospheric CO2 was stored by corn during its growth and some of it is captured and then injected underground, resulting in atmospheric carbon removal.

Example of a CCS large scale project: Northern lights. Equinor (formerly Statoil), the Norwegian energy company, already sources and stores CO2 from Norwegian industrial facilities. It now evaluates, with Shell and Total, the feasibility of a pan-European scheme, positioning itself as a “storage service provider”. Given the transport requirements, the CO2 balance must be carefully assessed. The project illustrates the ideal positioning of large industrials on the CCS topic: they have expertise in geological exploration, gas transport, industrial capture technologies and above all the balance sheet to commit (or guarantee) the millions of euros of capex. (Source: Global CCS Institute — 2019 Global Status of CCS report)

Today, industrial CCS is mostly about emission limitation. Some projects are desperate attempts to keep alive a dying model (CCS for coal power plants for example) while others are real efforts to limit emissions from industrial processes that the world needs anyway.

As we saw, that won’t be enough: on the road to large-scale coordinated carbon removal, we are still at the starting point*.

*: yes we plant new trees but the forest area as a proportion of total land area is decreasing (see figure 24)

From the most natural to the most technological CO2 removal solutions

A full range of techniques will be necessary if we want to achieve carbon removal at the necessary scale in 2050. It’s worth asking which ones should be pushed first, based on costs to be pragmatic.

Before jumping in, let’s remind the major carbon removal solutions and split them into 3 groups:

Natural: lower energy practices that could fit into current usages

• Soil carbon sequestration (SCS): changing land management — and agricultural practices — to increase the upper soil organic carbon content
• Afforestation (AR): planting trees on land not forested for a long time

Hybrid: processes requiring the implementation of a supply chain of “raw materials” (minerals, waste or biomass)

• Enhanced weathering (EW): enhancing the natural process of rock decomposition in which atmospheric CO2 is converted to bicarbonates that ultimately flow into the oceans
• Biochar: burying solid organic carbon obtained from pyrolysis of biomass
• BECCS: bioenergy with carbon capture and storage (discussed in part 2)

Technological: highly energy intensive, completely new practices

• DACCS: direct air carbon dioxide capture and storage (discussed in part 2)
• Ocean alkalinization (OA): reducing ocean acidity to enhance its CO2 storage capacity

Only “natural” solutions could make economic sense now

The cost estimates of the different carbon removal techniques come from scientific research papers. And for good reason: for some, there has never been any actual pilot project!

We therefore rely on different simulations. In 2018, Fuss et al. aggregated all of them to obtain ranges of costs (and capture potential):

Source: 2018 IPCC Global Warming of 1.5 degrees report

Let’s put it simply: we have only a vague idea of the costs associated with each solution. 2 facts nevertheless:

• The most “natural” solutions seem much less expensive than the “technological” ones
• Only “natural” solutions seem likely to cost less than €100 per ton

This is a problem because public subsidies or emissions trading schemes such as the EU ETS* which could (and eligibility criteria will be a major debate over the coming years) finance these projects only price CO2 at around €25 per ton.

Only the more “natural” solutions could make economic sense now. Other ones will require a significant increase in CO2 prices, explaining why CCS has not yet expanded into DACCS and BECCS.

What does that mean for our roadmap?

*: EU ETS allows European power and industrial companies to buy and sell emission allowances, currently rewards underground storage and will support new CCS projects through the Innovation Fund

Let’s not wait for moonshots

Even if necessary over the long-term due to the limited potential of other solutions, the development of technological ‘moonshots’ such as Direct Air Capture should not be our only hope:

• Yes, they are incredibly sexy for an entrepreneur because they consist in the development of a single tech, applicable everywhere, infinitely scalable and, conceptually, beautifully simple
• But they are highly energy intensive, they do not fit into existing practices, they have no positive impact other than CO2 capture and therefore they are very, very far from economic profitability

It’s too risky to wait for potentially distant technological breakthroughs before moving on with CO2 removal. In the meantime, we need to implement more “natural” processes that fit better into our current practices.

Agricultural and soil management is key

The topsoil contains a lot of carbon, trapped in organic matter. But in the open air, it decomposes, leading to the release of CO2. Modern agricultural practices have fostered this phenomenon, through deeper ploughing, poor terracing or lack of cover crops* causing erosion. 150 to 350 billion tons of CO2 were released this way in the atmosphere since the beginning of the industrial era.

We must, in addition to reforesting where possible (and where it makes sense in terms of CO2 capture), return to more sustainable agricultural practices that will reverse the phenomenon. These techniques are energy-efficient, positively affect the nutritional quality of the soil and can fit in our current practices. With the right financial incentives, they might already make economic sense.

*: transitional crops between two harvests

Source: Nature

Of course the potential is limited (maybe no more than a few Gt/year cumulatively and it seems quite optimistic) due to the related land requirements and the eventual carbon saturation of the soil. This involves regular monitoring as storage is not irreversible. More importantly, and contrary to the technological shortcuts discussed above, it requires local efforts from many stakeholders (farmers of course but also decision makers to set the right incentives).

Waste products can be leveraged

With the same willingness to adapt to current practices in order to start CO2 removal today, even at a limited scale, solutions relying on “waste” products of our current model can be deployed. Again, we’ll probably have to do so only locally.

• Mining waste piles: the natural weathering of most rocks (silicates, carbonates and oxides) binds carbon dioxide from the atmosphere. By exposing them to the open air in fine powder form, the process can be enhanced. Some of these rocks are already mined: for example basalt to supply aggregate for construction. “ Wasted “ basalt (too fine after the crushing process — up to 15% of the production) could be spread in fields for CO2 removal purposes but also to provide some of the nutrients needed by plants. Of course, again, the potential for capture is limited because the volumes required are very large and the supply chain must be local so that transport CO2 emissions does offset the removal effects.

Source: Project Vesta — Weathering is the long-term process that leads carbon atoms from the atmosphere to the lithosphere

• Organic waste: food waste, green waste, paper waste, manure, human waste, sewage or slaughterhouse waste can be burnt (locally, no need for big facilities) in oxygen-free chambers to form charcoal, a very stable carbon-containing material. When buried, charcoal increases soil carbon stocks as well as improve soil fertility and other ecosystem properties. The potential is limited (maybe 0.7 Gt/year, around 10% of CO2 removal targets at mid-century) and requires changing local habits but the key is that this practice, called biochar, can fit into existing processes and have positive effects in addition to CO2 capture.

As long as the supply chain for “raw materials” is local, some practices can leverage waste products to capture CO2 and improve the quality of our soils.

As for BECCS, it involves both large-scale centralized facilities and a supply chain of “raw materials” (biomass here). Contrary to some of the approaches presented here, it requires heavy investment and the coordination of a complex value chain (biomass sourcing, transport, combustion, storage).

Big changes start with small steps

In the short term, the large-scale implementation of the most centralized technological solutions seems difficult because they are far from being profitable and do not fit into our current practices. But other more “natural” solutions exist.

Since they have a more limited potential and require local efforts more than the widespread adoption of a single new technological breakthrough, they might not appeal to decision-makers and investors, who often choose the slim chance of a moonshot over a bigger probability of moderate success.

Climate issues, however, force us not to wait:

• Not only we must continue research on the most technological solutions, because we will probably need them (see Part 2)
• But we must seize the lowest-hanging fruits now, by starting field pilot projects involving more “natural” solutions. Every tonne of atmospheric CO2 actually captured can help us to avoid a climatic catastrophe

PS: Again, thank you to all those who took the time to discuss this topic with me over the past few weeks. It’s not easy to identify trends in such an emerging field, don’t hesitate to write to me if you have a different opinion!