Sequestration

Carbon Sequestration

Carbon sequestration is the processes of removing carbon from the atmosphere in order to help mitigate global warming. Sequestration is a new technology and a variety of ways of artificially capturing and storing carbon are being explored. Research is ongoing to find ways of enhancing natural sequestration processes.

NATURAL SEQUESTRATION also known as carbon sinks:

LAND: Vegetation and soils are widely recognized as carbon storage sinks. The global biosphere absorbs roughly 2 billion tons of carbon annually, an amount equal to roughly one third of all global carbon emissions from human activity. Significant amounts of this carbon remains stored in the roots of certain plants and in the soil. In fact, the inventory of carbon stored in the global ecosystem equals rougly 1,000 years worth of annual absorption, or 2 trillion tons of carbon. Check out Deforestation issues for more. At EP@W, we consider the best place to sequestrate carbon is in the soil.

OCEANS: CO2 is soluble in ocean water, and through natural processes the oceans both absorb and emit huge amounts of CO₂into the atmosphere. In fact, the amount of carbon stored in the ocean dwarfs the carbon stored in terrestrial ecosystems.

ROCK: Carbon dioxide sequestration in geologic formations includes oil and gas reservoirs, unmineable coal seams, and deep saline reservoirs. These are structures that have stored crude oil, natural gas, brine and CO2 over millions of years.

Carbon Capture

Before carbon dioxide (CO₂) gas can be sequestered it must be captured as a relatively pure gas. CO₂ is routinely separated and captured as a by-product from industrial processes such as synthetic ammonia production, H2 production, and limestone calcination. Large point sources of CO₂emissions include electricity generation units, petroleum refineries, and cement and lime production facilities.

Most power plants and other large point sources use air-fired combustors, a process that exhausts CO₂diluted with nitrogen. Flue gas from coal-fired power plants contains 10-12 percent CO₂ by volume, while flue gas from natural gas combined cycle plants contains only 3-6 percent CO2. For effective carbon sequestration, the CO2 in these exhaust gases must be separated and concentrated.

CO2 is currently recovered from combustion exhaust by using amine absorbers and cryogenic coolers.

Research into new capture and sequestration techniques has identified the following options for CO2 separation and capture:

Absorption (chemical and physical)
Adsorption (physical and chemical)
Low-temperature distillation
Gas separation membranes
Mineralization and biomineralization

Sequestration in Soils.

'Best bang for your biomass' estimated carbon sequestration (in tonnes of CO₂e per hectare). (Each european emits about 12 tonnes CO₂e/yr).

1. Planting Trees The trouble with forests (sequesters 4-20 t CO₂e hectare) is that eventually the trees rot and return CO₂ back to the air, so they are a short term (50 - 100 yr) solution.

2. Burying wood 3.7 t CO₂e. Doesnt sound much, but if virtually every forest also buried wood 5-20 m down (employing 1 mil. workers) that would offset our present emissions. Zeng - "carbon balance & Management".

3. Biochar burying - 363 t CO₂e - smoulder food & other domestic waste @ 350oC in absence of air (pressure cook), and the gases are given off leaving carbon whcih added to soil - as Amazonians did 500 yrs ago, and the results of carbon rish soils are still there to prove it. To halt the rise in atmospheric CO₂ pollution, we would need to pyrolise 8% of Earth's Annual biomass production.

4. Peat Restoration 285 tCO₂e This involves replanting water surfaces with marsh grases/bulrushes and allowing them to die & and build up under water replacing the peat at a faster rate than it has declined. One delta project in San Fransisco, is already equivalent to replacing all California's SUV's with high effeciency hybrids. Twitchell Island

Full Picture and Article from New Scientist

Task 1:
Check what sequestration projects are being conducted by your power suppliers and their competitors.

Task 2: Find out what the manufacturers down your supply chain are doing to sequest their point source CO2 if your industrial processes include any of the following:

Synthetic ammonia
H2
Calcinated limestone
Petroleum
Cement and lime products

Members can now go to the database and answer the questions on 'Sequestration'

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CARBON COUNTER Toolkit ...Sequestration										Noticeboard
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