Carbon Dioxide Removal Technology

Efforts to tackle climate change involve both reducing emissions and removing carbon dioxide (CO₂) from the atmosphere.

Carbon dioxide removal (CDR) refers to technologies and practices, both nature-based and engineered, that actively take CO₂ out of the air and store it away permanently or over the long-term.

These methods differ from “carbon capture and storage”, which typically refers to technology that targets emissions at the source before they enter the atmosphere (e.g. from factories or power stations).

What’s the Difference Between Carbon Capture & Storage (CCS) and Carbon Dioxide Removal (CDR)?

Carbon Capture & Storage (CCS)
This involves capturing CO₂ from flue gases before it escapes into the air. It is mostly applied at large industrial sites or power stations. Once captured, the CO₂ can either be stored or utilized.

Carbon Removal
This goes one step further by extracting CO₂ already in the atmosphere, helping to reduce the legacy emissions contributing to climate change. These approaches are needed for achieving net-zero and eventually net-negative emissions.

For more, see: Direct Air capture vs Point Source

Below are the main CDR approaches in  use today.

Direct Air Capture (DAC)

For more detail, see: How Does Direct Air Capture Work?

Description

DAC uses machines to draw in ambient air and chemically remove CO₂, which is then stored underground (carbon sequestration) or the CO₂ is utilized in other processes.

Permanence

• Very high. If mineralised and  stored in geological formations, it can last for hundreds of thousands of years, making it a permanent solution.

Co-benefits

• Some DAC solutions (such as NEG8 Carbon’s DAC technology) produce pure water as a by-product.
• The captured CO₂ can be utilized in other processes, such as Sustainable Aviation Fuel or storing the CO₂ in concrete.

Energy Use and Cost

• Energy use can be relatively high. Using waste heat reduces the demand from electricity, for example, in NEG8 Carbon’s DAC, waste heat input reduces it from 1.4 MWh/t CO₂ to 0.4 MWh/t CO₂.
• Current costs ranges from $300–$1000 (for the older tech) per tonne CO₂ captured, although this is falling as the technology develops and costs of $100 to $150 per tonne are in sight.

Advantages

• Can be located anywhere; does not need to be at the source of emissions.
• Precisely measured and verifiable.
• Can capture hard-to-abate emissions
• For more: Advantages of Direct Air Capture

Disadvantages

• Can be costly and energy-intensive.
• Requires reliable storage infrastructure for the captured CO₂.

Afforestation and Reforestation

For more detail, see: Direct Air Capture vs Forestation

Description

Forestation involves planting trees in areas that are either newly forested (afforestation) or recovering from deforestation (reforestation).

Permanence

• Moderate. CO₂ is stored in tree biomass, but can be released through, for example, fires, pests, or logging.

Co-benefits

• Forestation enhances biodiversity, prevents soil erosion, and supports water cycles.

Energy Use and Cost

• Low energy usage.
• Costs vary by region and land value, but generally low to moderate costs ($30 – $50/tonne of CO₂ captured).

Advantages

• Co-benefits to the environment.
• Low tech and easy to implement.

Disadvantages

• Requires large areas of land to be effective.
• Vulnerable to climate impacts and deforestation.
• Forests take time to grow.
• The durability of the carbon captured is only about 100 years.

Biochar

For more detail, see: Direct Air Capture vs Biochar

Description

Biochar is a stable, carbon-rich material produced by heating organic waste, such as wood or crop residues, in a low-oxygen environment through a process called pyrolysis.

Permanence

• High. Carbon is stored in a stable solid form and can remain for hundreds or possibly thousands of years.

Co-benefits

• Biochar enhances soil fertility and water retention.
• It reduces methane and nitrous oxide emissions from soil.

Energy Use and Cost

• Requires moderate energy to produce.
• Low to moderate cost depending on scale.

Advantages

• Durable carbon storage.
• Useful soil amendment.

Disadvantages

• Supply of suitable biomass and land may be limited.
• Variable carbon content and quality.
• Monitoring can be a complex and uncertain process.

Enhanced Rock Weathering (ERW)

For more detail see: Direct Air Capture vs Enhanced Rock Weathering and Accelerated Carbonation Technology Plus Direct Air Capture

 

Description

Crushed silicate rocks are spread on land, where they chemically react with CO₂ in the air and rainwater, forming stable carbonates to accelerate the process of natural weathering.

Permanence

• High. Once converted to carbonates, the CO₂ is locked up for hundreds to thousands of years.

Co-benefits

• ERW can improve soil health and crop yields.

Energy Use and Cost

• Moderate energy use for mining, grinding, and transport.
• Costs range from $50–$200 per tonne.

Advantages

• Durable storage in natural mineral forms.
• Can piggyback on existing agricultural practices.

Disadvantages

• Requires large volumes of rock.
• Logistics and verification still being refined.
• Possible release of toxins into the environment from heavy metals (e.g. chromium and nickel).
• Silicate particles could affect aquatic and marine life.

Bioenergy with Carbon Capture and Storage (BECCS)

For more, see: Direct Air capture vs Point Source

Description

Combines biomass energy production with carbon capture and storage.

Permanence

• Very high when mineralised and stored geologically.

Co-benefits

• Provides energy while removing CO₂.

Energy Use and Cost

• Energy use is moderate to high; depends on energy crop for feedstock, transport, and capture technology.
• Cost ranges from $100–$200 per tonne.

Advantages

• It has a dual-purpose: energy and carbon removal.
• Can be integrated into existing energy systems.
• BECCS is a mature technology.

Disadvantages

• Large land and water demands.
• Risks around food security and biodiversity.

Direct Ocean Capture (DOC)

 

Description

Direct Ocean Capture refers to technologies that extract dissolved CO₂ directly from seawater. Since oceans hold around 150 times more CO₂ than the atmosphere, DOC targets this large, stable reservoir. The process involves drawing in seawater, using chemical or electrochemical methods to isolate the CO₂, and then either storing it underground or using it in products.

Permanence

• High, if the extracted CO₂ is stored in geological formations or mineralised.
• If reused (e.g. in synthetic fuels), permanence depends on the end-use.

Co-benefits

• Helps reduce ocean acidification by removing dissolved CO₂.
• Potential to integrate with desalination or marine infrastructure.

Energy Use and Cost

• Energy use is moderate to high, depending on the process (electrochemical approaches tend to be energy-intensive).
• Cost per tonne is estimated in early-stage pilots at $100–$300.

Advantages

• Oceans are a vast and accessible CO₂ reservoir, providing a consistent source.
• Seawater contains ~150x more CO₂ by volume than air.
• Can be paired with clean energy or offshore renewables.

Disadvantages

• DOC is still at pilot stage and the technical and economic viability are not yet proven at scale.
• Potential environmental impacts on marine ecosystems if not properly managed.
• Requires reliable CO₂ storage or utilisation infrastructure.

Ocean Alkalinity Enhancement

 

Description

Adding alkaline minerals to seawater to increase its capacity to absorb and store CO₂ as bicarbonate.

Permanence

• Relatively high. Bicarbonate ions are stable and circulate in the ocean for hundreds of years.

Co-benefits

• May help counter ocean acidification.

Energy Use and Cost

• Energy needs and costs are variable but likely to be moderate to high.

Advantages

• Massive potential storage capacity.
• Works at a global scale.

Disadvantages

• Limited testing at scale.
• Uncertain ecological impacts.

Peatland and Wetland Restoration

 

Description

Wetland restoration is the rewetting or restoring of damaged peatlands and wetlands, which are naturally carbon-rich environments.

Permanence

• Moderate to high if maintained. CO₂ is stored in anaerobic (oxygen-free) conditions with slow decomposition rates.

Co-benefits

• Supports wildlife.
• Improves water quality.
• Reduces flood risks.

Energy Use and Cost

• Low energy requirements.
• Moderate to high cost depending on site condition and water management needs.

Advantages

• Effective in terms of CO₂ captured per hectare.
• Delivers wide ecological benefits.

Disadvantages

• Complex governance (land rights, drainage, etc.).
• Needs long-term stewardship.

 

 

Interested in NEG8 Carbon’s CO₂ capture technology?

Contact the NEG8 Carbon Team