Negative emissions are the removal of carbon dioxide from the atmosphere, the opposite of releasing it. Rather than just reducing the CO2 that factories, cars, and power plants put out, negative emissions technologies and practices actively pull CO2 back out of the air and lock it away in trees, soil, rock, or underground storage. Every major climate pathway that limits warming to 1.5°C relies on some amount of carbon removal, making negative emissions a necessary complement to cutting emissions at the source.
Why Cutting Emissions Alone Isn’t Enough
Some industries, like cement manufacturing, aviation, and agriculture, produce CO2 or other greenhouse gases that are extremely difficult to eliminate with current technology. Negative emissions exist to counterbalance those stubborn sources. The IPCC’s pathways for keeping warming to 1.5°C call for global CO2 emissions to drop roughly 45% from 2010 levels by 2030 and reach net zero around 2050. “Net zero” doesn’t mean zero emissions. It means whatever CO2 still enters the atmosphere is matched by an equal amount being removed.
In most IPCC scenarios, carbon removal also plays a second role: achieving net negative emissions after a temperature peak, essentially drawing down the atmospheric CO2 concentration to bring warming back below 1.5°C after temporarily overshooting it. Without large-scale negative emissions, that correction isn’t possible.
Nature-Based Approaches
The simplest forms of carbon removal work by enhancing what ecosystems already do. Trees absorb CO2 as they grow, so planting new forests (afforestation) or replanting cleared ones (reforestation) increases the planet’s capacity to pull carbon from the air. Soil management practices on farmland, such as cover cropping and reduced tillage, can store additional carbon in the ground. Restoring wetlands and peatlands locks carbon into waterlogged soils where it decomposes very slowly.
These methods are relatively inexpensive and can start immediately. About 2.1 billion tonnes of CO2 are already removed from the atmosphere each year, largely through these conventional, nature-based methods. The limitation is scale. Per-hectare carbon uptake rates are modest, and expanding forests or changing agricultural practices competes with food production and biodiversity. Realistic estimates suggest nature-based approaches alone are unlikely to deliver more than 10 billion tonnes of CO2 removal per year globally.
Bioenergy With Carbon Capture and Storage
BECCS combines biology with engineering. Plants absorb CO2 as they grow, then that plant material is burned or processed to generate energy. Instead of letting the CO2 escape back into the atmosphere, it’s captured at the facility and injected into deep geological formations underground. The net result is energy production that actually removes carbon from the atmosphere rather than adding it.
BECCS features prominently in climate models. The UK, for example, estimates the technology could deliver 20 to 70 million tonnes of CO2 in annual negative emissions by 2050. But BECCS has significant resource demands. Growing enough biomass to remove just one billion tonnes of CO2 per year requires 30 to 43 million hectares of land. Scaling to 10 billion tonnes would consume roughly 40% of the world’s current cropland. Water requirements are similarly large, especially if energy crops need irrigation, creating direct tension with food security and freshwater ecosystems.
Direct Air Capture
Direct air capture (DAC) uses chemical processes to pull CO2 straight from ambient air, then stores it underground or converts it into products. Unlike trees, DAC facilities can be placed almost anywhere and don’t require fertile land. Carbon Engineering launched its first pilot plant in British Columbia in 2015, and several larger facilities are now operating or under construction worldwide.
The main barrier is cost. A 2011 review estimated DAC at around $600 per ton of captured CO2. More recent engineering analyses have brought that estimate down to between $94 and $232 per ton, depending on the plant design and energy source. Even at the lower end, that’s far more expensive than nature-based removal. For DAC to operate at climate-relevant scale, costs need to continue falling, and the energy powering these plants needs to be low-carbon itself, otherwise the process partially cancels out its own benefit.
Enhanced Weathering
When certain rocks, particularly basalt, are exposed to rain and air, they naturally react with CO2 and lock it into stable mineral forms. This happens slowly over geological time, but crushing the rock into fine particles and spreading it on farmland dramatically speeds up the process. The dissolved carbon eventually washes into rivers and oceans, where it remains stored on timescales of thousands of years.
Enhanced weathering is appealing because it can be integrated into existing agricultural systems. Farmers already spread mineral amendments on fields; swapping in crushed basalt could simultaneously remove carbon and improve soil health. Costs vary considerably depending on how far the rock needs to be transported from quarry to field and the local climate conditions that drive weathering rates.
Biochar
Biochar is made by heating waste plant material (crop residues, wood chips, forestry waste) in a low-oxygen environment, converting it into a charcoal-like substance. Burying biochar in soil locks the carbon in a form that resists decomposition for decades to centuries. As a bonus, biochar can improve soil structure, water retention, and nutrient availability, giving farmers a practical reason to adopt it beyond climate benefits.
The Scale Gap
The gap between current carbon removal and what climate targets demand is enormous. Today’s 2.1 billion tonnes of annual removal comes almost entirely from forests and land management. Technological methods like DAC and BECCS contribute a tiny fraction. Meanwhile, global CO2 emissions remain above 35 billion tonnes per year. Closing that gap requires both massive emissions cuts and a rapid scale-up of removal capacity.
Every negative emissions approach involves trade-offs. Nature-based methods are cheap but land-hungry and vulnerable to reversal through wildfires or land-use changes. BECCS can generate energy while removing carbon but competes with food production. DAC avoids land conflicts but is expensive and energy-intensive. Enhanced weathering and biochar are promising but still early in deployment. Most experts agree no single method will be sufficient. Reaching net zero will likely require a portfolio of approaches, each contributing where it’s best suited.