For a long time, the climate debate followed a fairly simple principle: emit less CO₂, become more efficient and expand renewable energy.

That remains essential. But it is not enough.

Even with ambitious decarbonization, residual emissions will remain in sectors such as cement, chemicals, agriculture and aviation. At the same time, large amounts of additional CO₂ are already in the atmosphere.

This is why Carbon Dioxide Removal, or CDR, is becoming increasingly important. The term covers technologies and methods that actively remove CO₂ from the atmosphere and store it as permanently as possible.

One of the best-known approaches is Direct Air Capture, or DAC. Some see DAC as a key technology for reaching net zero. Others consider it too expensive, too energy-intensive and difficult to scale.

The discussion becomes more useful when DAC is compared with other CDR approaches, such as pyrolysis and biochar.

Why carbon removal is needed at all

CO₂ accumulates in the atmosphere. So it is not only about how much we emit today, but also about how much has built up over decades. A simple way to explain this is the bathtub analogy.

Emissions are the running tap. Cutting emissions means turning the tap down further and further. That remains the most important task. But even an almost closed tap does not remove the water that is already in the bathtub. Carbon removal is the drain. In the long term, we need both: significantly lower emissions and methods that remove CO₂ from the system again.

CDR does not replace emissions reduction. It complements it where residual emissions are technically or economically difficult to avoid completely.

Direct Air Capture: removing CO₂ directly from ambient air

Direct Air Capture filters CO₂ directly from the surrounding air. Air is moved through a system, the CO₂ is chemically captured and later released from the sorbent material. It can then be stored, for example in geological formations. The main advantage is that DAC is not tied to a specific emissions source. A plant can in principle be located where low-carbon energy and suitable storage infrastructure are available.

The challenge is the very low concentration of CO₂ in ambient air. It is only around 0.04 percent. Large volumes of air therefore have to be moved and processed to remove meaningful quantities of CO₂. This creates three major challenges.

High energy demand

DAC requires electricity and heat for fans, pumps, sorbent regeneration and further CO₂ processing.

For the overall carbon balance to be attractive, this energy needs to come from very low-emission sources.

High costs

The cost per tonne of CO₂ removed is currently well above conventional carbon prices.

DAC is therefore not yet a low-cost mass-market solution. It is mainly relevant where highly durable and clearly measurable carbon removal is required.

Scaling is still at an early stage

Many DAC projects have been announced in recent years. Actual delivered removal volumes are still small compared with long-term climate targets.

That does not mean the technology does not work. The market is simply still in an early stage.

The key question is whether energy demand, investment costs and operating costs can fall fast enough for DAC to move from pilot projects to real industrial scale.

Biochar: nature takes care of the first step

Pyrolysis works differently.

Plants absorb CO₂ from the atmosphere while they grow and store the carbon in biomass.

Under normal conditions, much of this carbon is released again through decomposition or combustion.

In pyrolysis, biomass is thermally treated under oxygen-limited conditions. Part of the carbon is converted into a very stable form: biochar.

When the biochar is used in a durable way and properly documented, it can become a long-term carbon sink.

The difference compared with DAC is straightforward.

DAC filters CO₂ from highly diluted ambient air. In the case of biochar, the carbon is already concentrated in the biomass.

Why biochar is currently closer to commercial deployment

Modern pyrolysis does not only produce biochar.

It can also generate usable energy in the form of electricity and heat. Suitable biogenic residues can therefore be used in several ways at the same time.

Depending on the site, several economic effects can be combined:

• use of biomass and wood residues
• electricity generation
• heat utilization
• sale of biochar
• sale of biochar carbon credits or carbon removal certificates

This means the economics of a pyrolysis plant do not depend on carbon removal alone.

Energy, residue utilization and biochar can all contribute to the business case.

That is one reason why biochar is currently one of the more practical CDR approaches.

There are still clear limits.

Sustainable biomass is not available in unlimited quantities. Scaling therefore has to stay within ecological boundaries.

Biochar quality also matters. Feedstock, process conditions, carbon stability, contaminants, final application and monitoring all need to meet defined standards.

DAC and biochar compared

Both approaches remove CO₂ from the atmosphere, but they work very differently from both a technical and an economic perspective.

The question is therefore not simply: DAC or biochar?

A more useful question is: which technology can be deployed today, at what cost and at what scale?

Other CDR technologies

There are several other approaches alongside DAC and biochar.

BECCS combines bioenergy with carbon capture and geological storage. The theoretical potential is large, but projects depend heavily on biomass availability and infrastructure.

Enhanced Rock Weathering accelerates natural mineral weathering processes that bind CO₂. The approach is promising, but logistics and measurement remain challenging.

Ocean-based approaches could offer very large theoretical capacities. Many are still at an early technological and regulatory stage.

Nature-based solutions such as forests and peatlands remain essential for climate protection and biodiversity. Their permanence and carbon accounting differ, however, from technical CDR methods.

It is unlikely that one single technology will solve the entire problem.

In the end, economics matter

The CDR debate often focuses on theoretical potential in millions or billions of tonnes.

For real-world deployment, another question matters just as much:

Who pays for the carbon removal?

A technology can work technically and still have limited impact if every additional tonne remains permanently expensive.

This is why approaches that combine carbon removal with additional economic value are particularly interesting.

Pyrolysis can do exactly that.

Residues are utilized, electricity and heat are generated, biochar is produced and carbon is stored for the long term.

CDR becomes part of an industrial value chain rather than a stand-alone cost item.

Conclusion

Direct Air Capture has real potential, especially where very high permanence and clearly measurable carbon removal are required.

Today, however, it still comes with high costs, high energy demand and limited deployment.

Pyrolysis and biochar are at a different stage.

Sustainable biomass availability sets a clear limit. At the same time, carbon removal can already be combined with residue utilization, electricity, heat and biochar production.

That is why we see biochar as one of the CDR approaches that is particularly well suited to practical deployment today.

In the long term, there will not be a simple either-or.

We need lower emissions, several high-quality CDR technologies, clear standards and business models that work economically.

In the end, theoretical potential is not enough.

What matters is how much CO₂ is actually removed, stored durably and verified.