That Cannabis cigarette carries two pounds of CO2 emissions
Assuming that the entire joint is carbon, and all of it converts to CO2, a 1 gram joint will release 3.7 grams of carbon dioxide.
That's 0.008 pounds of CO2. Two pounds of CO2 is 250 times more than reality. The author must be smoking his topic.
No, he's including the carbon generated by the electrical power requirements to grow the plant to make the joint.
The word “contains” is being used in a peculiar way to denote the total amount of something (in this case CO2) involved in the production (in this case by release into the atmosphere). This strange use of “contains” as applied to “emissions” (that’s already an odd usage) can be found in critiques of “green” projects by other “greens”, for instance use of ethanol as a motor fuel, or use of solar panels — in each case considering the emissions in the production process along with those from the use of the technology.