Carbon Capture and Utilisation

The acronyms get used interchangeably in public communication, often by people who should know better. They are two different industries with different economics, different timescales, different climate accounting, and different commercial customers. Conflating them creates real confusion in technical and policy discussions.

CCS, Carbon Capture and Storage, captures CO₂ from a source and injects it permanently underground. Depleted oil and gas reservoirs, deep saline aquifers, and basalt formations are the principal storage media. Once injected, the CO₂ leaves the active carbon cycle. The intended duration is geological: thousands of years, ideally permanent. The objective is climate mitigation through long-term sequestration. The commercial customer is typically the emitter, who pays to dispose of CO₂ that would otherwise enter the atmosphere or attract a carbon price.

CCU, Carbon Capture and Utilisation, captures CO₂ and converts it into useful products. The carbon remains in the active carbon cycle, in most cases. The objective varies. Sometimes the goal is climate mitigation, when the product locks the carbon away for long timescales. Sometimes the goal is feedstock substitution, replacing fossil-derived CO₂ in existing chemical processes with captured CO₂ from biogenic or industrial sources. Sometimes it is both. The commercial customer is typically the user of the downstream product, the buyer of the fuel or the chemical or the construction material.

The same capture technology often serves both pathways. The fork in the road comes after the CO₂ is captured: it can be injected (CCS) or it can be converted (CCU). The capture step is the more mature engineering. The utilisation step is where most of the current innovation, and most of the contested climate accounting, sits.

This page is about the U in CCU. CCS is referenced where relevant for context, but the substantive discussion is about what happens to captured CO₂ once you have decided to use it rather than store it. The two pathways are increasingly being framed as alternatives by climate policy and project developers. Whether they actually are alternatives, or whether they serve different roles in a decarbonising economy, is one of the genuinely interesting open questions in this space.

CO₂ for utilisation comes from three principal source categories, each with different concentrations, different costs, and different climate accounting.

Industrial point sources. Many industrial processes produce concentrated CO₂ streams as a byproduct of their normal operation. The concentration varies widely. Ammonia plants release essentially pure CO₂ from the steam methane reforming step. Ethanol fermentation, biogas upgrading and similar biological processes release CO₂ at near 100 percent purity. Cement kilns release CO₂ at 15 to 30 percent concentration, mixed with combustion gases. Steel plants release CO₂ at 15 to 25 percent. Coal-fired power plants are around 10 to 15 percent. Natural gas-fired power plants are around 4 to 10 percent, the most dilute of the major industrial sources.

Higher concentration means cheaper capture. Pure streams from ammonia and fermentation can be captured for €20 to €50 per tonne. Cement and steel streams cost €40 to €90. Power plant flue gas costs €60 to €150. The capture technology choice also varies with concentration. Amine-based absorption dominates for low-to-medium concentration streams. Solid sorbents are emerging as alternatives with lower energy demand. Membranes work well at higher concentrations. Calcium looping is emerging specifically for cement applications. Oxy-fuel combustion produces a pure CO₂ stream by feeding the combustor with oxygen rather than air, but it requires plant-scale integration that is best done on new builds.

Biogenic CO₂. The same capture technologies, applied to biological sources. The CO₂ has come from the atmosphere through plant photosynthesis within recent biological cycles, so using it does not add net fossil carbon to the atmosphere. The economics are similar to point-source industrial capture, often better because biological streams are typically highly concentrated. The constraint is supply. The total globally available biogenic CO₂ from concentrated sources is on the order of a few hundred million tonnes per year, against gigatonne-scale demand under aggressive decarbonisation scenarios.

Direct Air Capture (DAC). Capturing CO₂ directly from ambient air at roughly 420 parts per million in 2025. Two main technology families dominate. Liquid solvent DAC (Carbon Engineering, 1PointFive) uses hydroxide solutions to absorb CO₂, then regenerates the solvent with high-temperature heat. Solid sorbent DAC (Climeworks, Heirloom, Carbon Capture, others) uses amine-functionalised solid materials, regenerated with moderate temperature. Electrochemical DAC is emerging as a third family but is earlier on the maturity curve.

Costs in 2025 are in the range of €400 to €1,000 per tonne for current operational plants, with credible projections of €200 to €400 per tonne by 2030 and €100 to €200 per tonne later in the decade if substantial scale-up materialises. DAC is the only capture pathway that does not depend on a concentrated source, which makes it geographically flexible and unambiguously climate-positive. It is also currently five to fifteen times more expensive than point-source capture.

The carbon source decision is one of the more consequential decisions in a CCU project. Point-source CO₂ from a fossil emitter, used to make e-fuels, is technically CCU but offers limited net climate benefit because the fossil emitter continues operating. Biogenic CO₂ is genuinely circular. DAC is genuinely additive. The cost differences between these sources, and the regulatory frameworks treating them differently (RED III progressively restricts fossil point-source CO₂ as an RFNBO feedstock through to 2041), mean that the carbon source choice is rarely just an engineering decision. It is a strategic and political decision with engineering implications.

This is the section that matters most, and it is the section that the CCU industry's marketing materials most often dance around.

The fundamental climate accounting truth: the value of capturing one tonne of CO₂ depends on how long that tonne stays out of the atmosphere afterwards. If the CO₂ is released back within weeks, the climate value is minimal. If it stays locked for centuries, the climate value is real. CCU pathways span the full range from one to the other, and the differences are enormous.

The spectrum of permanence, ordered from shortest to longest:

Hours to days. Beverage carbonation, where the CO₂ is released as soon as the can or bottle is opened. Greenhouse enrichment, where most of the CO₂ is released through plant respiration and ventilation within days. Some industrial uses with short cycles.

Days to months. Most fuels. e-Diesel and e-kerosene release their carbon during combustion, which happens days to weeks after the fuel is produced. e-Methanol consumed as a fuel similarly. The climate value of these pathways is in displacing fossil alternatives, not in storing carbon. They are useful for decarbonising aviation and shipping because nothing better is available, but they are not sequestration.

Months to a few years. Urea fertiliser releases its CO₂ within months of application to soil through hydrolysis. Short-life chemical intermediates that are produced, consumed and metabolised quickly. Single-use plastics that enter combustion or biodegradation.

Years to decades. Many durable plastics, depending on end of life. Polycarbonate window panes, polyurethane insulation, structural plastics in buildings and vehicles. The carbon stays in service for the lifetime of the product, then enters waste streams where its fate depends on disposal practices.

Decades to centuries. Polymers and materials in long-lived applications where they do not enter combustion (some construction polymers, long-life composites). Carbon-fibre structural elements.

Centuries to millennia. Mineralised carbonates, in concrete and aggregates. CO₂ in CaCO₃ and MgCO₃ is thermodynamically extremely stable. The reaction is the same one that locks CO₂ into limestone over geological time, accelerated industrially. Carbon-bound minerals last as long as the rock they are part of, which is geological in scale.

Geological permanence. This is the timescale of CCS (deep saline aquifer injection, basalt mineralisation in situ), not CCU strictly speaking. Though enhanced rock weathering, where ground-up reactive minerals are spread on agricultural land or coastal areas to react with atmospheric CO₂ over years to decades, is sometimes classified as a CCU adjacent pathway.

For climate accounting purposes, most frameworks (the IPCC, the European Commission, the voluntary carbon market) draw a line somewhere between the years-to-decades band and the decades-to-centuries band. Below that line, the climate benefit is treated as marginal or as a displacement claim rather than a sequestration claim. Above that line, the carbon storage is considered durable enough to count meaningfully against emissions.

This creates a useful framing for any CCU project: is this project doing something that will actually keep carbon out of the atmosphere for a climate-meaningful time, or is it primarily doing fossil fuel displacement? Both can be legitimate goals. They are not the same goal. A project that conflates them, or that markets short-permanence CCU as if it were permanent sequestration, is misleading its customers, its investors, and ultimately the climate accounting frameworks that will catch up.

The public and academic critique of CCU includes several arguments that any serious page on the topic should address rather than dodge. They are worth taking seriously even if you ultimately conclude, as Ionect does, that CCU has a legitimate role in a decarbonising economy.

Most CCU does not sequester carbon. It either displaces fossil fuels (in the case of e-fuels) or it cycles carbon temporarily through products before releasing it. The climate value of these pathways is real, but it is the value of avoiding emissions elsewhere, not of removing emissions that have already happened. Conflating the two is the most common rhetorical mistake in the CCU industry.

CCU may justify continued fossil operation. The argument from the critical literature is that CCU on a fossil emitter, paid for in part by carbon credits or RFNBO offtake, can provide political cover for delayed fossil fuel phase-out. The emitter keeps emitting, but reframes the operation as a "CCU project" rather than as an unabated fossil operation. This is the moral hazard argument, and it is taken seriously enough by policymakers that European RED III restricts the use of fossil point-source CO₂ for RFNBO production after 2041.

Energy efficiency is poor. Almost every CCU pathway requires substantial energy input, much of which would deliver more decarbonisation if used directly. A megawatt-hour of renewable electricity used in a heat pump, or to charge a battery electric vehicle, delivers more end-use decarbonisation than the same megawatt-hour used to make an e-fuel through a multi-step CCU chain. This argument does not invalidate CCU, but it does argue for being disciplined about where CCU is deployed.

Scale potential is bounded. Even the most ambitious scenarios for CCU in 2050 capture and utilise on the order of one to two gigatonnes of CO₂ per year. Current global emissions are around 40 gigatonnes per year. CCU is a tool, not a solution. Treating it as a solution risks substituting one form of dependency for another.

Carbon accounting is contested. The lifecycle greenhouse gas accounting of CCU pathways is genuinely complex. Different accounting frameworks reach different conclusions. Some products that claim climate benefit under one framework do not deliver it under another. The voluntary carbon market is currently navigating a credibility crisis driven in part by overstated claims from offset projects, and CCU claims are subject to the same scrutiny.

The honest response to these critiques, as Ionect sees them, is roughly as follows. CCU is genuinely useful where it serves applications that cannot be decarbonised any other way (aviation and deep-sea shipping fuels are the leading examples), where it replaces fossil-derived feedstocks in industries that will continue to need carbon-containing products (ammonia, methanol, polymers), or where it locks carbon away durably in materials that the world is going to keep building (concrete and construction materials at the top of that list). CCU is overrated where it is marketed as carbon-neutral when it is in fact short-permanence carbon recycling, where it is deployed in applications that could be electrified directly, or where it is used to extend the operational life of fossil emitters that should be phasing out. The framing that serves projects and the climate well is to ask, of any CCU project: is this doing something that genuinely needs to be done, and is it doing it in a way that is actually useful for the climate? Both questions need yes-answers. Many announced projects only answer one.