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Synthetic trees to extract CO2 from the air (recommended by the Institution of Mechanical Engineers (UK.)
It has been proposed to build 100 foot synthetic trees to filter CO2 from the air and using sodium hydroxide to convert CO2 to Sodium Carbonate and store this deep underground in saline aquifiers or oil reservoirs .
One tree would extract 3650 tonnes of CO2 per year (one real oak tree might process 0.03 tonnes a year.) Therefore 5 million synthetic trees would capture 18 G tonnes of CO2 (5 G tonnes of carbon) a year, approaching the worlds CO2 emissions. These could be located near to source of emissions, industry, motorways etc. Costs could be £12,000 each ($20,000 each.) Professor Klaus Lackner of Columbia University New York has been testing prototypes.
100,000 synthetic trees could fit into 600 hectares (1500 acres) and clean up CO2 emitted in the UK
Comment. The energy used in operation could be prohibitively high.
Amount of manmade CO2 emissions
CO2/ Carbon Storage
The Global Geological site potential for CO2 storage is between 1000 and 10,000 Gigatonnes (Gt) of CO2. The potential for CO2 capture is around 2.6 to 4.9 Gt CO2 (0.7 to 1.3 Gt carbon) per year (ref 160). The Global emissions in 2001 totaled 24 Gt of CO2 (6.5 Gtc) which is estimated to rise to 38 Gt by 2030 so this process could be a help for many years to reduce CO2 in the air.
Potential in UK North Sea areas is for 40 Giga tonnes of CO2 to be liquefied and stored over 200+years in sandstone (porous) capped with mudstone at 3 mile depth. (ref ST p6 news 16 08 09)
The brine filled aquifer (brine in pore spaces) UTSIRA is solid rock 500 km X 50 km and 200 meters thick, 1000 meters beneath the sea bed under the Sleipner Norwegian oil field. 0.8 million tonnes of CO2 per year has been pumped into the pore spaces for ten years. (One power station would provide 4 million tonnes of CO2 per year) ( ref 127).
CO2 takes on a liquid form under 800 metres underground so is unlikely to escape. (Ref 1 p292). It dissolves into saline water and may eventually become solid mineral carbonates.
