Industry

One of the main issues with methane removal is that atmospheric methane concentrations are very low. This means that very large volumes of air, and related energy demands, are required, making the use of ventilators like those used for DACCS (see direct air capture) more complicated (Nisbet-Jones et al. 2021).

Passive daytime radiative cooling (PDRC) promises to provide energy free cooling through thermally-emissive surfaces that reflect incoming solar radiation whilst simultaneously enhancing longwave heat transfer to space through the infrared window of the atmosphere (8–13 µm) (Yin et al. 2020).

Tropospheric Iron Salt Aerosol injection (ISAI) has recently received significant attention as a potential methane mitigation technique.

Apart from proposals to destroy atmospheric methane or capturing it, some have suggested it could be possible to prevent methane from reaching the atmosphere or flaring it.

The built environment takes up an ever greater portion of the earth’s surface. This mostly unused surface area could be coated in albedo enhancing paints or material which would allow them to reflect incoming sunlight.

The most widely studied carbon storage technique is the large-scale application of biochar. Biochar is produced when biomass is pyrolysed - a thermal process in which oxygen for combustion is lacking.

Inspired by the discovery of CO2 ice caps on Mars, Agee et al. (2013) suggested it might be possible to artificially create similarly cold conditions in the already frigid temperatures of Antarctica that would allow CO2 to 'snow' out of the air.

Some have suggested that it might be possible to capture methane or methane hydrates and transform it into useful materials.

Enhanced weathering (EW) is a measure that seeks to enhance and speed up the process of rock weathering in which CO2 reacts with minerals (Schuiling and Krijgsman 2006) that naturally occurs and already consumes 1.1 Gt CO2 per year (Ciais et al. 2014).

Black Carbon (BC), also known as soot, is produced through the incomplete combustion of fossil fuels and biomaterials. Apart from its negative health impacts, BC also has significant climate effects because it generally has a lower albedo than its surroundings, which increases the amount of radiation absorbed both when BC is present in the atmosphere and when it is deposited on land (Stjern et al. 2017). Due to the large albedo differences, the effects of BC are especially significant in areas that are normally covered in snow or ice (Hadley and Kirchstetter 2012; Sand et al. 2016; Kang et al. 2020).

Direct air carbon capture and storage (DACCS) aims to reduce the amount of carbon dioxide in the atmosphere by taking it directly out of the air, and removing it from the carbon cycle.