Back of the envelope cost estimates for afores…

Please tell me that I made a horrible math error.

A. Amount of CO2

Annual CO2 Emissions (all sources) 32,000,000,000 tons / year Airborn Fraction (not absorbed into existing carbon sinks) 43% Annual accumulation of CO2 in the atmosphere 13,760,000,000 tons / year 

B. Amount of forest required for CO2 capture

Amount of CO2 that can be captured by one mature tree per year 50 lbs / year Number of trees per acre (tree plantation) 1,000 trees / acre 640,000 trees /square mile Amount of CO2 per acre of forest captured annually 50,000 lbs / year per acre 25 tons / year per acre 16,000 tons / year per square mile Square miles of forest needed to capture excess CO2 860,000 square miles (approximately 900 x 900 miles) Comparisons: Australian Outback 2,500,000 square miles Gobi Desert 500,000 square miles Sahara Desert 3,552,000 square miles Total number of trees 550,400,000,000 trees 

C. Water requirements

Amount of water needed per tree (mature oak) 50 gallons / day 18,250 gallons / year 0.056 acre*foot /year Total amount of water needed for CO2 capture trees 30,822,400,000 acre*foot /year 84,444,932 acre*feet/day Comparisons: Lake Superior 9,799,680,000 acre*foot Lake Baikal (Siberia) 19,261,440,000 acre*foot Irrigation efficiency (advanced Isreali drip irrigation techniques) 95% Amount of water to be desalinated 32,444,631,579 acre*foot /year Comparisons: Amount of water consumed by New York City annually 1,120,185 acre*foot /year 

D. Capital Costs

Cost per acre of desert (typical Nevada desert land prices) $200 per acre Total land costs $110,080,000,000 Cost of planting one acre of trees (seedlings) $500 per acre Total planting costs $275,200,000,000 Cost of 250 MGD desalination plants (Ras Al Khair Plant) $7,200,000,000 each Number of 250 MGD desalination plants 110,098 each (equivalent to 767 acre*feet per day) Total cost of desalination plants $792,703,398,760,515 Amount of concrete pipe water mains 2,376,000,000 feet (assume 1,000 each 12 ft dia. concrete pipelines, ave 450 miles) Unit cost of concrete pipe (assume 8 ft lengths) $300 / foot Total costs of water mains $712,800,000,000 Total capital costs (with 10% added for misc.) $873,181,626,636,567 Comparisons: USN aircraft carrier strike group $30,000,000,000 International space station $150,000,000,000 

E. Annual Operating costs

Cost of desalination (large plant, $950 to $1,300 per acre* foot) $1,000 acre*foot $32,444,631,578,947 per year Pumping rate (assume 1,000 pipelines, each 450 miles long) 61,729 acre*foot / minute 18,711,000,000 gpm 18,711,000 gpm per water main Head Losses 82,244,903 feet (assume 12 ft dia. reinf. concrete pipes/tunnels) Cost of Pumping ( $9,776,019 per hour (assume cost rate of $0.10 per kWh) $85,637,926,440 per year Total operating costs (with 10% added for misc) $35,783,296,455,926 Comparisons: World GDP (2014) $78,280,000,000,000 

Found here