This may sound stupid, but hat there been a study...

[slor]

that shows which plants are most efficient at pulling CO2 from the air. Or any other pollutants for that matter? Also is cannabis good at this? Also, I am speaking specifically about outdoor air. TIA

[displacedtexan]

1. I have no idea, but...

a form of marijuana (called Ditch Weed) grows wild in the corn and soybean fields of Central Illinois, despite the heavy use of pesticides. I always figured that nature had a reason for this.

[Viking12]

2. Not exactly

There is a robust, albeit obscure, sub-field in biology that studies the CO2 exchange/sequestion potential of bioregions, plants, soils, algaes, etc... However, I'm not aware of more than a few speculative comparative studies. The most probable reason for the lack of comparative studies is the unique methodologies necessary to study individual areas/species are incompatible for comparison purposes.

Given the vilification of hemp generally, I suspect little has been done to study hemp specifically due to an inability to obtain necessary funding.

As in most other areas of climate science, there are a few industry sponsored charlatans publishing in this area so beware. If you see the name Idso, The Greening Earth Society, Cooler Heads Coalition, or Marshall Institute associated witha study, you can pretyy much dismiss it w/o regard.

[DrWeird]

3. Cannabis is very good for this.

It grows very, very fast. That is, it fixes carbon very quickly. The faster and more massive a plant grows, the more CO2 it uses.

[Massacure]

4. If I recall Algae does a good job at this.

However when it dies, it sucks huge amounts of oxygen out of the water.

[happyslug]

5. The last report I read

Indicated the problem was not the type of plant but other nutrients the plant needed to process the Carbon. It is the shortage of these other Nutrients (Most iron) that is the restriction.

The lack of usable iron appears to be the reason for the large "Ocean Deserts" in the southern Pacific and Indians Oceans. The Southern Ocean is rich in minimals, but the Southern Ocean's circulations system keeps those Nutrients near Antarctica and out of the deserts of the Pacific and Indian oceans. Nutrients from the other land masses are just consumed before any can reach these deserts.

Thus you have a huge area of the Ocean Surface with no Algae, even through it has water and sunlight and everything else needed for Algae to use sunlight and water to fix carbon.

See the following for details on iron and Carbon Cycle:
http://www-ocean.tamu.edu/education/oceanworld/ocean401/ocng401_course_schedule.html

"Why phytoplankton need Fe (iron):
Phytoplankton require very small amounts of Fe for survival and growth. Fe is required for efficient photosynthesis, as photosystem II requires 2 atoms of Fe. In low dissolved Fe conditions inactivation of photosystem II can be as high as 50%. This leads to a marked reduction in efficiency with which light is photochemically converted to chemical energy. Fe is also required by a number of enzymes including nitrate reductase which is used to reduce NO 3 to a form that can be used by the cell. In cells with an adequate Fe supply the ratio of cell carbon:cell Fe is approximately 10 000:1, in comparison to a ratio of 100 000:1 when Fe is limiting growth."
http://www.rsnz.org/education/alpha/alpha106/alpha-106.htm

Other references:
http://www.princeton.edu/~cebic/c-cycle.html