Negative emissions techniques are methods that remove CO₂ from the atmosphere and store it for in a permanent manner. Therefore, all negative emissions solutions consist of two components: a method for capturing atmospheric or biogenic carbon and a means of storing the captured carbon for a climate-relevant period (100+ years).

Negative emissions can be achieved through natural and technological approaches, ranging from biomass, soils and oceans, to storage in deep geological formations. Specific approaches like biochar and bioenergy with carbon capture and storage (BECCS) can be considered a mix of natural and technological approaches. Some approaches use biomass to draw CO₂ from the air; others like direct air capture with carbon storage (DACCS) and enhanced weathering, remove CO₂ directly from the air.

The Intergovernmental Panel on Climate Change (IPCC) has stated that carbon dioxide removal (CDR) technologies are essential. They are required in almost all scenarios where the global temperature increase is to be limited to well below 2°C. Furthermore, enabling the delivery of national and corporate net-zero emissions pledges will require the gross removal of atmospheric CO₂ on top of conventional reductions. Therefore, reaching net-zero and staying in line with the long-term goal of the Paris Agreement will require gigatonne-scale CDR deployment by mid-century. And with scaling-up CDR approaches that can take decades, we need to start now to ensure we have the required  capacity in time.

BECCS combines energy production from fast-growing biomass with the capture and storage of the resulting CO₂. Since biomass takes up CO₂ from the atmosphere during its growth, the combination of both processes is equivalent to a net removal of CO₂. The potential of BECCS is estimated at 0.5–5 Gt CO₂. The amount depends on the availability of sustainably produced biomass whose cultivation competes with other uses. The estimated cost per tonne of CO₂ extracted and stored, ranges between $100–$200. Current TRL of 3-7 in the power generation industry and 7-9 in the bioenergy industry with large-scale developments are expected to come online in the 2020s/2030s. The global potential of BECCS is estimated to be between 2 to 5 GtCO₂/yr (by 2030) EU: 92 to 276 MtCO₂/yr (2050).

As olivine is ground down by the Earth’s natural wave energy, it dissolves, sequestering CO₂ into a molecule in the water known as bicarbonate. This locks away CO₂ for thousands of years. Over time this can also turn into limestone trapping carbon at the bottom of the ocean. Accelerating and scaling this process offers a significant solution to climate change by enhancing one of Earth’s oldest processes to sequester carbon. The process is included in a number of terms including ocean alkalinity enhancement or coastal enhanced weathering.

EW occurs when CO₂ is permanently bound from the atmosphere into rock. EW accelerates this process by spreading finely ground silicate rock, such as basalt, onto land. This speeds up the chemical reactions between rocks, water and air; which remove CO₂ from the atmosphere and store it permanently in solid carbonate minerals.
Co-benefits include increasing crop yields through improved soil pH and nutrient addition. The current TRL ranges from 1-5, with most projects in the R&D phase. The global potential of EW is estimated to be between 1 to 4 GtCO₂/yr (by 2050) EU: 77 to 206 MtCO₂/yr.at $50–200 per tonne of CO₂ removed.

Combinations of different capture methods exist. Methods like Ocean CDR and recycled CO₂ from construction material, are grouped into this category. Ocean CDR can include photosynthesis by macroalgae that converts dissolved CO₂ into organic carbon. The macroalgal biomass can be harvested, compressed and sunk to the deep ocean, where the organic carbon is effectively sequestered. Macroalgae can be grown in most ocean areas, and productivity is mostly driven by biological characteristics, nutrient availability, seawater temperature and sunlight.

Waste can be harnessed for energy in the form of synthesis gas (syngas) and biochar, which capture and remove carbon without emissions. Waste to energy and CCS therefore present a sustainable alternative to landfill and incineration, where non-recyclable plastics and other biogenic waste would otherwise be burnt or buried. Biogenic carbon removal from WtE in the EU is expected to be between 40-47 MtCO₂/yr by 2050.

When biomass is put through a process called fast pyrolysis, it breaks down into bio-oil. This liquid is rich in carbon but low in energy content; it is then injected into wells, where the bio-oil sinks and solidifies for permanent storage.

Biochar is produced in a process called pyrolysis. This term describes a thermo-chemical conversion of organic compounds, especially biomass, in an oxygen-limited environment at high temperatures.
In addition to being a powerful soil improver, biochar can also act as a carbon sink that can remain stable in soil for thousands of years. Biochar has an extremely high carbon content, 94%, each dry ton of biochar contains 2,5 tonnes of CO₂. The potential of biochar as a CO₂ removal option is about 0.5–2 GtCO₂/yr. The cost per tonne of CO₂ is estimated at $30–120.

The mineral carbonation process uses CO₂ from waste products or from DAC to produce building material. Mineral carbonation offers an attractive route to CO₂ utilisation because (1) solid carbonates, the main products of mineral carbonation reactions, are already used in construction materials markets; (2) the chemistry involved in making carbonates based on calcium (Ca) and magnesium (Mg) is well known; (3) carbonation can consume large amounts of CO₂ by chemically binding it into stable, long-lived mineral carbonates; and (4) the reaction of CO₂ with alkaline solids is thermodynamically favoured, thereby needing little, if any, extrinsic energy.
The current TRL ranges from 6 to 8, especially regarding cement. Near-term commercial deployment opportunities (3 to 10 years).
The global potential is estimated to be between 0.1 to 1.4 GtCO₂/yr (by 2050) EU: 744 MtCO₂/yr (2050).

The use of the deep ocean to store carbon-rich material is another storage possibility. At sufficient depth, CO₂ can be stored in the water column or on the sea bed. For example, biomass from seaweed farming could be sunk to deep oceans where the organic carbon remains isolated from the atmosphere for hundreds of years to thousands of years.

Mixed storage is a combination of different storage methods. For example, when captured CO₂ is stored underground or transformed into high value carbon-based products, including synthetic fuels, carbon nanotubes and CO₂ enriched concrete.

When CO₂ reacts with certain rocks, solid minerals are created and stored in formations deep underground. In situ mineralisation, or mineral trapping, is a component of underground geologic sequestration, in which a portion of the injected CO₂ interacts with reactive rock formations, such as basalts, to form stable minerals. In addition to accelerating these natural processes, the process captures and permanently removes CO₂, providing a permanent and safe carbon sink.