Who Needs to Mine the Sky?

More emerging technology with application to space settlement: Plant Extracts Arsenic from Polluted Soil

The technique of using plants to clean up polluted soil in order to make poisons less harmful is called “phytoremediation,” and has proven viable for removing arsenic. But arsenic collected from the soil is stored in the plant root, which makes safe harvesting and disposal a challenge.

Meagher and his team genetically modified Arabidopsis, a small member of the mustard family, to be arsenic-resistant and to move the arsenic collected in its root up to its shoots. The new method is much more efficient, too, soaking up 16 times more arsenic than normal Arabidopsis plants.

“We want a 35- to 50-fold increase in these plants’ ability to sequester arsenic, and now that we understand the mechanism, we believe that is possible,” Meagher said.

Imagine what further development of this technology will be able to do for settlements on the Moon and Mars, where useful elements may be too diffuse to mine economically by conventional techniques, and where adapting conventional mining techniques to such radically different environments may itself be impractical. This technology would be especially useful in the early years of settlement, as it would employ similar infrastructure to that required for agriculture (or for human occupation, for that matter) rather than the high-energy conventional extraction methods and the complex, integrated industrial base which supports them.

On the other hand, just because the plants concentrate a particular element in their leaves or stems doesn’t mean that you get off this easy. Some processing of the biomass would still be required, and that is likely to be energy intensive.

Of course, phytoremediating bacteria would probably be a better choice for industrial-scale extraction — they could be used in a continuous/bulk process (rather than in discrete growing cycles), and would probably allow a greater efficiency in terms of equipment, energy, and space used.