Carbon
Element 6 · chemical symbol: C
These Vrulum profiles mention Carbon by name. Read each profile for its specific context; a mention alone does not establish composition, performance or use of the pure element.
For periodic-table data and other properties, consult the Royal Society of Chemistry periodic table.
Related technology profiles
2D semiconductor electronics
Two-dimensional semiconductors such as molybdenum disulfide (MoS2) form sheets only a few atoms thick and could make transistors that keep working at very small sizes. Lab devices and a small 1-bit processor have been demonstrated, but no production chips built from these materials are described in the sources reviewed here.
Artificial photosynthesis
Artificial leaves are devices that use sunlight to split water into hydrogen and oxygen in one integrated unit. Laboratory modules have reached about 11% solar-to-hydrogen efficiency under one-sun illumination, but durability and outdoor performance at useful scale have not yet been shown.
Asteroid sample return missions
An asteroid sample return mission collects material from an asteroid in space and brings it back to Earth for laboratory study. Hayabusa2 and NASA's OSIRIS-REx have both done this, and peer-reviewed analyses of the returned material are now being published.
Biochar
Biochar is a carbon-rich solid made by heating biomass with little or no oxygen, which can be added to soil to store carbon for a long time. Field and laboratory evidence suggests much of its carbon persists for decades or longer, but yield effects vary widely by region and soil, and credited volumes are reported inconsistently.
Carbon-storing building materials
Carbon-storing building materials add carbon-rich biochar to concrete, or cure cement-based products with CO2 so that the gas becomes solid minerals. Pilot and small field trials were reported in 2025, but whether they give a net climate benefit over a full lifecycle is not yet established.
Catalytic converters
A catalytic converter is a device in a petrol car's exhaust that uses a catalyst to turn carbon monoxide, unburnt fuel and nitrogen oxides into less harmful gases. It has been fitted to new petrol cars in the United States since the mid-1970s, and it depends on lead-free petrol.
Crops with boosted photosynthesis
Plant scientists are engineering crops to waste less light energy and carbon, either by recovering faster from the protective heat release that follows shade or by bypassing photorespiration. Several replicated field trials report yield or biomass gains, but the soybean yield result is disputed and no independent multi-site replication is confirmed in the sources reviewed.
Direct air capture of CO2
Direct air capture uses chemical sorbents to pull carbon dioxide from ambient air and concentrate it for storage. The technology is at an early commercial stage, and cost per tonne and energy use are the main open questions.
Electrochemical CO2 conversion
Electrochemical CO2 conversion uses electricity to turn carbon dioxide into chemicals such as formate. Prototype stacks built from 1,526 cm² cells have been reported, but long-term stability, energy use and climate benefit at industrial scale are not yet shown.
Electrolysers for low-carbon hydrogen
Electrolysers use electricity to split water into hydrogen and oxygen. Alkaline and proton-exchange-membrane systems are commercially available, while solid-oxide and anion-exchange-membrane designs offer different trade-offs and maturity levels. Hydrogen is only low emissions when the electricity and wider supply chain are low emissions; project announcements and electrolyser capacity do not by themselves establish climate benefit or delivered hydrogen output.
Engineered living materials
Engineered living materials are materials made with the help of living cells or the structures they produce. A 2024 laboratory study made a stretchable, compostable film from engineered bacterial protein fibres, but the work is at prototype stage and does not show a product that can replace plastic.
Enhanced rock weathering
Enhanced rock weathering spreads finely crushed silicate rock, such as basalt, on farmland so that it dissolves and locks CO2 into carbonate. Field trials show measurable removal and some yield gains, but removal is mostly calculated rather than measured, and estimates of scale and cost vary widely.
Hydrogen aircraft
Hydrogen aircraft would use hydrogen either in a fuel cell that drives electric propellers or in a modified gas turbine. Engine and fuel-cell tests, an uncrewed drone flight and airport ground trials have taken place, but no hydrogen passenger aircraft has entered service and the climate benefit depends on how the hydrogen is made.
Industrial steelmaking
Industrial steelmaking turns molten iron into steel by removing carbon and other impurities. The main methods date from the Bessemer process of 1856 and the open-hearth furnace, and today's routes are the basic oxygen furnace and the electric arc furnace.
Laser and robotic weeding
Robots that weed with lasers, targeted sprays or mechanical tools aim to reduce the blanket herbicide applied to crops. Field trials show strong weed control from lasers on young weeds and substantial herbicide savings from targeted spraying in some trials, but the savings depend heavily on weed pressure and the independent evidence is still thin.
Lithium-ion batteries
Lithium-ion batteries store and release electricity by moving lithium ions between two electrodes, and they power electric cars. Their cost and energy density keep changing, but fire risk, dependence on nickel-containing chemistries and recycling that is still developing remains an open limit.
Making oxygen and fuel on Mars
NASA's MOXIE instrument on the Perseverance rover made oxygen from the Martian atmosphere over 16 runs, reaching 12 grams per hour at its most efficient. Making methane fuel and extracting water on Mars, and scaling oxygen production for crewed missions, remain at model, proposal or concept stage.
Ocean alkalinity enhancement
Ocean alkalinity enhancement adds alkaline material to seawater so that the sea takes up more carbon dioxide from the air. Small field trials and early carbon credits exist, but the removal in those credits was calculated with models rather than measured, ecological effects depend on the material used, and the legal framework is still being developed.
Perennial grains
Perennial grains are cereal crops that live for several years and regrow from the same roots, so farmers do not have to replant them every season. Kernza and perennial rice are the best-documented examples, but yields tend to fall as stands age and soil carbon gains have not been shown at scale.
Petroleum refining
Petroleum refining separates crude oil into fractions and changes their molecules to make petrol, diesel, jet fuel and lubricating oils. Its key steps ran from early kerosene stills to catalytic cracking in the 1930s. EPA reports that refinery sulphur dioxide and nitrogen oxide emissions have fallen since 2000.
Protein made from air and electricity
Gas fermentation grows microbes on hydrogen, carbon dioxide and oxygen, then dries the cells into a protein powder for food or feed. One producer reports a food approval in Singapore and a self-affirmed GRAS conclusion in the United States, but published cost and life-cycle studies depend heavily on low-carbon electricity and are mostly modelled rather than measured at scale.
Recirculating aquaculture systems
Recirculating aquaculture systems (RAS) raise fish in land-based tanks that filter and reuse most of their water. They need large amounts of energy, are costly to build, and have suffered failures and closures.
Satellite methane detection
Satellites can spot methane plumes from large leaks at oil, gas, coal and landfill sites. Detection limits depend on instrument design, wind and surface conditions, and the sources reviewed here do not show how often detections lead to repairs.
Seaweed farming at scale
Farmed seaweed is already produced at scale, and it is being promoted for carbon removal and for cutting methane from cattle. The carbon claim is disputed among ocean scientists. The methane evidence is early, comes from trial results for one red seaweed, and the authors of the summary we checked call for replication.
Sodium-ion batteries
Sodium-ion batteries store energy by shuttling sodium ions between two electrodes, much as lithium-ion batteries do with lithium. They use abundant materials and manufacturers now claim early mass production, but they still store less energy per kilogram than the best lithium-ion cells.
Solar sails
Solar sails are large, very thin reflective membranes that change a spacecraft's speed or orbit using the small, steady push of sunlight rather than fuel. Japan's IKAROS (2010) and NASA's LightSail 2 (2019) showed the method works in space, but the push is very small and the sail must unfold and survive in orbit.
Space biomanufacturing
Space biomanufacturing uses microbes in sealed reactors to turn prepared feedstocks into useful materials, such as bioplastic, for future missions. A 2026 preprint reports laboratory production of bioplastic from simulated Mars-like inputs, but this has not been shown on Mars and the work has not been peer reviewed.
Structural batteries
A structural battery stores electrical energy while also carrying mechanical loads, for example in a composite panel whose carbon fibres act as electrodes. Laboratory cells have reported energy densities from about 30 to 187 Wh/kg, depending on design, electrolyte and mass basis, and high stiffness, but no complete vehicle or aircraft powered by a load-bearing battery structure has been demonstrated in the sources reviewed.