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Posted March 7, 2008
Carbon Capture

Towards carbon-negative bioenergy: Scientists develop low-cost material for capturing carbon dioxide from smokestacks

Biopact - Scientists and engineers from the Georgia Institute of Technology and the National Energy Technology Laboratory (NETL) are reporting development of a new, low-cost material for capturing carbon dioxide from the smokestacks of electric power plants and other industrial sources before the notorious greenhouse gas enters the atmosphere.

If these carbon capture technologies are coupled to biomass power plants, they can yield "negative emissions" energy - by far the most radically green type of energy. So-called carbon-negative bioenergy, based on capturing and storing biogenic CO2, actively removes carbon dioxide from the atmosphere. Other energy technologies like solar or wind power remain 'carbon neutral' at best, slightly carbon positive in practise: during their lifecycle, they add small amounts of CO2 to the atmosphere, but they can never remove the greenhouse gas from it.

The difference between 'bio-energy with carbon storage' (BECS) and other renewable energy technologies is radical: solar PV adds around +100 tonnes of CO2eq per GWh of electricity generated; wind adds +30 tonnes; hydropower adds between +10 and +20 tonnes. Carbon-negative bioenergy however can remove up to 1000 tonnes (that is -1000 tonnes/GWh, hence "negative emissions").

Driving an electric car the batteries of which were charged by this carbon-negative electricity would imply that you would be fighting climate change. In fact, the more you were to drive it, the more you were to prevent global warming. According to scientists fromt the Abrupt Climate Change Strategy group, such BECS systems can cool the planet and bring back atmospheric CO2 levels to pre-industrial levels by mid-century, if applied on a global scale - either in power plants coupled to carbon capture and storage that burn biomass instead of fossil fuels, or in bio-hydrogen production facilities.

One of the major bottlenecks towards the development of carbon-negative bioenergy is the creation of low-cost, efficient carbon capture technologies. In their new study, Christopher W. Jones and colleagues point out that existing carbon capture technology is unsuitable for wide use. Absorbent liquids, for instance, are energy intensive and expensive. Current solid adsorbents show promise, but many suffer from low absorption capacities and lack stability after extended use. Stronger, longer-lasting materials are needed, scientists say.

But the scientists now describe the development of a promising new solid adsorbent, coined a hyperbranched aminosilica (HAS), that avoids most of these problems:

The HAS was synthesized by a one-step reaction, spontaneous aziridine ring-opening polymerization off of surface silanols, to form a 32 wt % organic/inorganic hybrid material. The adsorption measurements were performed in a fixed-bed flow reactor using humidified CO2.

When compared to traditional solid adsorbents under simulated emissions from industrial smokestacks, the new material captured up to seven times more carbon dioxide than conventional solid materials, including some of the best carbon dioxide adsorbents currently available, the researchers say. The material also shows greater stability under different temperature extremes, allowing it to be recycled numerous times.

"Designing Adsorbents for CO2 Capture from Flue Gas-Hyperbranched Aminosilicas Capable of Capturing CO2 Reversibly"

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