A collection of 'branch' carbon dioxide collectors, or scrubbers, bunched together and displayed in a small box, made by Professor Klaus Lackner at the Lenfest Center for Sustainable Energy, Earth Institute, Columbia University, New York, 2010

This prototype carbon ‘scrubber’ was created by Professor Klaus Lackner during his time as Director of the Lenfest Center for Sustainable Energy, Columbia University, New York (2001-2014). Lackner is one of a small number of scientists who had championed direct air capture – the removing of carbon dioxide from atmospheric air – during the 1990s and 2000s. When he began developing prototype carbon collectors like this one, most people viewed carbon capture as science fiction, considered too complex to be economically feasible. By the early 2020s, many considered that there is no practical way in which the Earth’s temperature can be kept below 1.5 degrees without carbon capture technologies.

This item is a test sample intended to be used for the mechanical tree’s collector branches or ‘leaves’. They are contained bunched within a small plastic box, with the leaves themselves made from a sorbent-impregnated polypropylene. The sorbent is an ion exchange resin called Dowex marathon A, which binds with carbon dioxide as a bicarbonate when dry. When wet, a carbonate ion replaces two bicarbonate ions, resulting in a release of carbon dioxide. This reversible reaction is central to the mechanical tree concept.