A DIFFERENT KIND OF INDUSTRIAL PLANT: Here's and interesting review of phytoextraction/phytoremediation: Phytoextraction of Metals from Contaminated Soils.

While this article deals with phytoextraction as a means for remediating sites polluted with certain metals, there is no reason why this technology couldn't someday be adapted for use on Martian soils. Using plants to extract useful metals and other resources directly from the soil would have several advantages for an early Martian colony:

• Less equipment, and specifically heavy equipment (mining machines and the like), would need to be transported from Mars to Earth, versus subsurface or strip mining.
  
• Extraction crops would require large domed enclosures, along with the equipment to maintain a suitable interior atmosphere, but these need be no different in principle or design from domed enclosures used for growing food crops.
  
• Processing and refining equipment would still be required. Ovens for drying the resulting biomass and chemical/electrolytic systems for refining the bioaccumulated metals, etc. to usable concentrations would be needed, but again it would not be the type of heavy equipment (stamp mills, etc.) associated with typical mining operations.
  
• Extraction farms would eventually become "exhausted", their soils depleted of extractable amounts of useful elements. These farms would then be suitable for food growth, essentially having been "remediated" like a terrestrial brownfield site. The soil could be reconditioned using the biomass byproducts left from the refining process and (later) sewage from nearby settlements, and used to grow traditional food crops to feed colonists.
  
• Since crops are self-producing and self-repairing, the need for spare parts and replacement units imported from Earth is eliminated.
  
• Unlike mining machinery, the crops would produce oxygen as they worked.
  
• I'd hazard a guess that the energy requirements would be somewhat lower, as well. The plants grow by sunlight. They produce breathable oxygen (which doesn't have to be manufactured instead, consuming power). No large trucks, boring machinery, crushing/stamping mills, or other energy-intensive equipment would be required. The refining processes would probably be similar to and therefore no more energy intensive than with methods that take crushed rock as their input.
  
• The farms can be tended in a shirtsleeve environment, with little human input/supervistion required, important considerations where a poisonous micropressure atmosphere necessitates wearing a bulky suit outside and makes such work inherently dangerous at all times, and where labor of any kind would be scarce and therefore expensive.
  
• Such farms would have far less impact on the Martian environment than traditional mining. This is sure to appeal to the Red crowd -- once the soil has given up its goods, the dome and other equipment can be dismantled and moved to another site, leaving behind little (or possibly even no) permanent footprint on the landscape.
  

Just a few ideas off the top of my head. I'm no biologist or mining engineer, so I could be wrong on every one of these points. However, it's hard to imagine this approach being less of a logistics and maintenance headache than traditional mining approaches.

Thoughts?

Posted by T.L. James on September 9, 2002 09:18 PM