Capturing, Removing, Storing, Reusing: The New Frontiers of CO2

Reducing emissions remains the top priority in the fight against climate change. Yet as the scale of the crisis becomes clearer, another approach is gaining ground: removing CO2 directly from the atmosphere. Is it a false solution or a necessary tool? Somewhere between technological ambition, industrial promise and environmental uncertainty, carbon removal is stirring debate. This article takes stock of the issue.

Capture or eliminate CO2: two strategies for the same objective?

The terms "carbon capture" and "carbon removal" are often confused, even though they refer to different strategies with different climate impacts. 

Capturing carbon generally means intercepting CO2 at the point of emission, for example from the flue gases
of industrial plants or power stations. This process, known as Carbon Capture and Storage (CCS), prevents greenhouse gases from entering the atmosphere and is considered to have a neutral climate effect. It offers a potential solution for decarbonising sectors with high emissions.

Carbon removal, on the other hand, focuses on eliminating CO2 that is already present in the air. This can be done through natural solutions such as reforestation, or through technological methods like direct air capture.
In contrast to capture at the source, carbon removal has a negative balance, as it contributes to lowering the overall atmospheric concentration of CO2.

These removal methods play three roles in climate strategies. In the short term, they help reduce net emissions. In the medium term, they are key to balancing out the residual emissions that cannot be fully avoided. Over the long term, their goal is to progressively reduce global warming by drawing down the CO2 already in circulation.

In a world where some emissions are unavoidable, particularly in sectors like aviation and heavy industry, carbon removal will be indispensable for climate stabilisation.

A variety of nature-based solutions

Reaching net-zero requires a wide range of solutions, both natural and technological. These vary in terms of maturity, cost, effectiveness and durability. Among them, nature remains our most powerful ally. So-called "nature-based" solutions such as reforestation, soil restoration, wetland rehabilitation and regenerative agriculture can sequester large volumes of carbon while also supporting biodiversity, local communities and ecosystem resilience.

These approaches work by strengthening or restoring natural carbon sinks. Reforestation (planting trees where forests once stood) and afforestation (creating forests in previously non-forested areas) are two of the most widely used methods today. According to estimates (Sabine Fuss et al, 2018), these methods could sequester up to 3.5 gigatonnes of CO2 per year globally. Their effectiveness is well documented. They store carbon in biomass and soil, improve biodiversity, reduce erosion and support rural incomes. However, they also have limitations. Monoculture plantations can harm biodiversity, and climate stress can reduce the resilience of forests. Additionally, afforestation in non-forest ecosystems can disrupt local environments and land use.

One illustrative project is ReforesTERRA in Brazil. Co-developed by Reforest'Action and the NGO Rioterra, this initiative aims to restore 2,000 hectares of degraded agricultural land in the Baixo Rio Jamari watershed, located in the state of Rondônia. Once covered almost entirely by forest, the region has lost more than half of its tree cover to agricultural expansion and livestock grazing. While forests play a crucial role in climate regulation, that role is only sustainable if the forests themselves remain healthy. Many of today’s forests are already weakened by climate change. A degraded forest stores less carbon, and one that is destroyed can release large amounts of carbon back into the atmosphere. Moreover, these projects require vast areas of land, between 3.4 and 17.8 million hectares per gigatonne removed, equivalent to roughly a third of France’s territory. They can also alter land surface reflectivity (albedo) and compete with food production. Depending on the region, costs vary between 100 and 200 dollars per tonne of CO2. High-impact projects must deliver both environmental and social benefits, including biodiversity protection, community involvement and long-term storage of carbon.

Storing carbon in soil: changing how we farm

Agricultural soils offer a powerful lever for carbon storage. Sustainable farming practices can improve soil health, boost biodiversity and enhance ecosystem resilience while locking in CO2. Methods include agroforestry, compost use, creation of wetlands, high-carbon crops, permanent cover vegetation and crop rotation. These strategies have a potential to sequester up to 8.7 gigatonnes of CO2 per year and can be implemented at relatively low cost, between 0 and 100 dollars per tonne.

One concrete example comes from Soil Capital, a pioneering company in regenerative agriculture in Europe.Its programme, "Soil Capital Carbon," supports over 1,600 farmers in adopting low- carbon practices such as reduced tillage, crop diversification, organic matter application and cover cropping. The resulting carbon savings are certified and monetised as carbon credits, offering farmers additional income while improving their soil's health and resilience.

Avoiding ploughing is central to this strategy. Not turning the soil helps preserve organic matter and increases carbon sequestration. Studies show that adopting no-till farming can reduce agricultural emissions by 20 to 30 percent. Agriculture also heavily relies on fossil fuels, especially through nitrogen fertilisers, which are energy-intensive to produce and emit nitrous oxide, a greenhouse gas 300 times more potent than CO2. Modern farming machinery also contributes significantly to emissions. Reducing chemical inputs and shifting to agroecological methods could lead to major climate gains in this sector.

Underwater forests: the promise of marine permaculture

Among the more innovative approaches, marine permaculture is attracting interest. Large-scale seaweed cultivation — for example, kelp farming in open water — offers fast carbon uptake. Once mature, some of the algae naturally sink to the ocean floor, storing carbon for decades or even centuries. This solution does not compete for land and adds diversity to climate strategies, particularly in marine ecosystems.

Another method under study is ocean fertilisation, which involves adding nutrients like iron to stimulate phytoplankton growth. These micro-organisms enhance the ocean’s natural CO2 absorption capacity, currently estimated at 20 to 30 percent. However, this technique carries significant risks: ecosystem imbalances, oxygen depletion in treated zones and the release of other greenhouse gases such as methane and nitrous oxide. Scientific understanding is still evolving and cautious oversight is essential.

Other approaches: combining nature, chemistry and engineering

New approaches are being developed that combine natural materials with geochemistry and engineered systems. Their common feature is the long-term storage of carbon using abundant resources like soil, minerals or biomass. Some are operational, others experimental, but they are drawing growing interest in long-term climate strategies.

Enhanced weathering is one such method. It involves accelerating the natural reaction between certain minerals and CO2 to form stable carbonates. Rocks like olivine are crushed and spread over land where they react with water and atmospheric or soil CO2. In the marine environment, a similar approach involves increasing ocean alkalinity to boost CO2 absorption. This technique is still immature but is being tested in pilot projects such as Carbon Time, which explores the dispersal of alkaline rock offshore. These methods could store between 2 and 4 gigatonnes of CO2 per year, but they require substantial material volumes, suitable logistics and careful environmental risk assessments.

Biochar: locking carbon into the soil

Produced by pyrolysis of organic residues such as wood, crop waste or green waste, biochar is a type of charcoal that can be applied to soil to store carbon long-term. It improves soil fertility and raises pH in acidic soils, offering dual benefits for climate and agriculture. Biochar is already in use at small scale and has a potential of up to 6.3 gigatonnes of CO2 per year. Costs range from 30 to 120 dollars per tonne, depending on scale and technology.

However, this solution also has limitations. Pyrolysis can release potentially harmful aromatic compounds, the outcomes vary by climate and soil type, and biochar competes with other biomass uses, such as bioenergy with carbon capture. While promising, biochar should be seen as a complementary tool whose effectiveness depends on the agricultural context, biomass source and traceability of production processes.

Interest in biochar is growing, as illustrated by a major deal between Google and the Indian startup Varaha. In January, Google announced the purchase of 100,000 tonnes of carbon removal credits from Varaha, marking the largest deal of its kind to date. The company plans to set up six industrial-scale biochar reactors in Gujarat, each with a daily capture capacity of about 30 tonnes. Still, the risks and uncertainties linked to production must be carefully considered.

BECCS: combining biomass energy with carbon storage

Bioenergy with Carbon Capture and Storage, or BECCS, is a process that generates energy from biomass while capturing the CO2 released during combustion. Since the plants absorbed that CO2 while growing, storing it creates a negative emissions balance. There are two main applications: generating bioelectricity from biomass combustion and producing biofuels, sometimes alongside biochar.

The biomass can come from various sources including crop residues, forest waste, energy crops and even algae. BECCS has a theoretical capture potential of up to 10.5 gigatonnes of CO2 per year, with costs estimated between 100 and 200 dollars per tonne. Its main challenge is land use. Capturing just one gigatonne annually would require around 78 million hectares, roughly one and a half times the surface area of France. This raises concerns over competition with agriculture, biodiversity and natural ecosystems.

An emblematic example is the Exergi project in Stockholm. The company’s urban heating network provides heat, cooling and electricity to over 800,000 people and 400 key sites including hospitals and data centres. Using bioenergy, the system captures CO2 in cogeneration facilities, compresses it and transports it for storage in geological reservoirs beneath the sea. The project demonstrates both the technical feasibility of BECCS in urban environments and its potential
to contribute to local circular economies.

DACCS: powerful but energy-intensive

Direct Air Capture and Storage, or DACCS, is based on a simple principle: capturing CO2 directly from ambient air and storing it. This method offers a potential of up to 6.6 gigatonnes of CO2 per year, but it remains the most energy- and cost-intensive solution. Capturing one gigatonne could require over 1,300 TWh of electricity, more than twice France’s annual power production. Current costs range from 100 to 300 dollars per tonne, with some estimates exceeding 1,000.

These systems use solid or liquid absorbents to extract CO2. Once captured, the gas must be transported to storage sites, either by pipeline or by truck. It can then be injected into saline aquifers or depleted oil and gas reservoirs, or mineralised in basaltic rock formations, which greatly reduces the risk of leakage.

A successful DACCS project depends on robust logistics and is often integrated into existing industrial infrastructure to cut costs. While it also requires land and sometimes water, the footprint is far smaller than reforestation or BECCS. DACCS’s modular design and traceability also make it well- suited for high-quality carbon credit systems, as long as the energy used is fully decarbonised.

A recent example is Climeworks’ Mammoth plant in Iceland, launched in May 2024 near the Hellisheidi geothermal power station. With a capture capacity of 36,000 tonnes per year, ten times that of its predecessor Orca, the CO2 is permanently stored in underground basalt formations thanks to rapid mineralisation technology developed by Carbfix. This project shows that industrial-scale DACCS is technically feasible, although challenges remain in terms of cost, energy demand and infrastructure.

Challenges of carbon capture and storage

The effectiveness of carbon capture solutions depends on the availability of suitable geological storage for CO2, whether in deep saline aquifers or depleted oil and gas reservoirs. These natural formations could, in theory, hold gigatonnes of carbon for thousands of years. However, several risks remain: potential leaks, induced seismic activity and contamination of groundwater. Beyond the technical aspects, large-scale deployment is also limited by high costs and infrastructure requirements, including transport, compression and monitoring. CO2 capture technologies, especially methods like DACCS, are highly energy-intensive. To contribute meaningfully to climate mitigation, the energy used must come from low-carbon sources. If not, the emissions generated during energy production could cancel out a portion of the CO2 captured.

In Luxembourg, interest in CCUS (Carbon Capture, Utilisation and Storage) is growing, particularly in high-emission industrial sectors. Recently, FEDIL (the Federation of Luxembourg Industrialists) issued a set of policy recommendations urging the government to include CCUS in its national strategy, with the aim of strengthening the country’s economic competitiveness. These recommendations call for legislative adjustments to facilitate carbon capture and storage, the promotion of on-site storage options for producers, the development of adequate transport infrastructure, and coordination with European initiatives.

Yet beyond the technical considerations, the economic model remains a crucial question. For carbon capture and storage to be deployed on a significant scale, a clear and reliable financing framework is essential. Currently, the voluntary carbon market is one of the main levers available, enabling companies to purchase carbon credits from sequestration projects as part of their journey towards net-zero. However, this market remains fragile and suffers from a lack of transparency. To ensure widespread adoption of CCS solutions, it is vital to establish a regulated and trustworthy carbon credit system. This requires rigorous project certification, clear tracking of emissions reductions, and the integration of credits into both national and international climate policies. Additional financial incentives such as tax credits or subsidies could also be introduced to encourage investment in CCS technologies. The European Union is already considering incorporating carbon removal into its emissions trading system, which could increase the effectiveness of the carbon credit market.

From storage to reuse: adding value to captured carbon

Another pathway is emerging: reusing captured CO2 as a raw material. Rather than simply storing it, the carbon can be repurposed in various industrial applications, such as the production of synthetic fuels, building materials or chemicals. This approach, known as CCU (Carbon Capture and Utilisation), is fully aligned with the principles of a circular carbon economy. Its goal is therefore to address the root cause of climate change by 'defossilising' the economy, whereas other solutions focus on reducing the symptoms of the problem without questioning the linear and fossil-based economic model.

According to the roadmap of CO2 Value Europe, the international association representing the carbon capture and utilisation value chain, over half of the CO2 captured in Europe could be reused by 2050. This is particularly relevant in hard-to-decarbonise sectors like aviation, chemicals or cement. Mineralising CO2 in construction materials is one especially promising avenue, combining permanent storage with industrial value creation. This approach helps generate value while boosting self-sufficiency in raw materials and low-carbon energy. (See the interview with Célia Sapart, climatologist and scientific director of CO2 Value Europe).

A necessary tool, under clear conditions

Solutions for carbon removal, capture and storage, as well as carbon reuse, are all indispensable in the path toward climate neutrality. However, they can never be a substitute for emission reductions at the source. Their deployment must follow clear guidelines to prevent opportunistic misuse. High costs, environmental risks and energy dependencies are just some of the challenges involved. These solutions will only be effective if embedded within a rigorous strategy, backed by both public and private funding, and guided by climate justice principles. Carbon that is removed must not overshadow the carbon that still needs to be avoided.

It is also essential not to pit nature-based solutions against technological ones. When well-integrated, their complementarity can strengthen regional resilience, amplify environmental benefits and accelerate the transition to climate neutrality.