Constructing a forest of 'artificial trees' is one of the most promising technologies to remove carbon dioxide (CO2) from the atmosphere, according to a report published by the Institution of Mechanical Engineers in the UK. The report also calls for a national UK programme for research and development into "geoengineering" projects that could provide a better understanding of the risks and costs of manipulating the climate.

Most attempts to deal with climate change involve reducing emissions of CO2 and in December the United Nations Convention on Climate Change in Copenhagen will attempt to set binding targets for lowering such emissions for the first time. Yet even an agreement to cut CO2 emission by 50% by 2050 may not be enough to stop the planet's average temperature rising by 2 °C by the end of the century.

Geoengineering – deliberate intervention into the climate system to counteract man-made global warming – offers an alternative approach. The new report, Geoengineering – Giving us Time to Act?, looks at different geoengineering options for tackling climate change, including adding iron to the oceans to produce phytoplankton blooms that then absorb CO2 and constructing giant sunshades in space that can reflect the Sun's rays.

Absorbing carbon

The authors – led by Tim Fox, head of environment and climate change at the Institution of Mechanical Engineers – found that constructing fly-swat-shaped "artificial trees" is the most promising approach to reducing CO2. Such a tree would work by letting air pass through into the structure and then catching the CO2 via a "sorbant" material, such as sodium hydroxide. The CO2 is then removed and buried underground in a similar manner to conventional carbon capture and storage.

According to the report, constructing 100,000 such "trees" – each costing around $20,000 – would require 600 hectares of land but would be enough to remove the CO2 from the UK's homes and transport system.

Algae to the rescue

The report also recommends coating buildings with algae, which would absorb CO2 via photosynthesis. The authors state that the algae can then be "periodically harvested from building surfaces and used as biofuel".

The third recommendation is to make building surfaces more reflective. Although the authors claim that this method may not be as effective as the other two, "it does have the additional benefit of reducing temperatures in city centres, [which] can often be several degrees hotter than the surrounding environment".

The report also outlines a 100 year roadmap for geoengineering in the UK, which calls for £10m per year in funding to help bring together climate scientists, economists and engineers as well as the development and deployment of "smart grids" to manage demand by communicating with electricity meters in homes.

A separate report on geoengineering by the Royal Society is due to be published on Wednesday.