DAC systems use chemical sorbents (e.g., amines or hydroxides) or solid filters to bind CO₂, which is then released and stored or repurposed. Companies like Climeworks and Carbon Engineering have scaled plants to capture thousands of tons annually, with efficiencies improving via nanotechnology and optimized airflow designs. Energy intensity remains a challenge, requiring 1-2 MWh per ton of CO₂ captured.

Pairing DAC with solar or wind power reduces its carbon footprint, aiming for net-negative emissions. Iceland’s Orca plant, powered by geothermal energy, captures 4,000 tons yearly, demonstrating feasibility. Scaling to gigaton levels (needed for climate goals) demands vast renewable capacity and cost reductions from $600/ton to below $100/ton, a target for 2030.

Captured CO₂, combined with green hydrogen, produces synthetic hydrocarbons like e-fuels for aviation or shipping. Projects like Prometheus Fuels are commercializing this, offering drop-in replacements for fossil fuels. High production costs and energy inputs are barriers, but falling renewable prices are closing the gap.

Biochar, a charcoal-like material from pyrolyzed biomass, locks carbon in soil for centuries while improving fertility. A ton of biochar sequesters 2-3 tons of CO₂-equivalent, with global potential exceeding 1 Gt/year. Its deployment in agriculture, as in Brazil’s Amazonian Terra Preta soils, boosts yields and resilience, though production scalability and distribution networks need expansion.

Practices like cover cropping, no-till farming, and rotational grazing enhance soil organic carbon (SOC). The Rodale Institute estimates regenerative methods could sequester 20% of annual emissions if adopted globally. Benefits include drought resistance and biodiversity, but farmer adoption requires incentives and training to overcome traditional habits.

Fast-growing microalgae absorb CO₂ via photosynthesis, with species like spirulina capable of sequestering 1-2 tons per hectare annually. Large-scale algae farms, like those off California, double as biofuel sources (see Section 5.2). Challenges include nutrient supply and ecological impacts, but co-locating with aquaculture mitigates risks.

These pump nutrient-rich deep water to the surface, stimulating phytoplankton blooms that absorb CO₂. Trials in the Pacific show promise, with 1 km² potentially sequestering 100 tons yearly. Long-term effects on marine ecosystems are under study, requiring careful monitoring to avoid disruptions like oxygen depletion.