Typical CO2 savings for one 20’ container unit 
Washington: 7,000 - 22,000 lbs per year
Afghanistan: 9,000 - 28,000 lbs per year
Djibouti: 10,000 - 32,000 lbs per year
To achieve the same level of CO2 reduction
planting trees instead would require up to 1600 trees.
To put this in context, a camp or building site with 80 containers would have to establish a small forest consisting of up to 128,000 trees covering several acres to achieve the same carbon emission savings that can be achieved by equipping the containers with SolarDrive power units.
Furthermore most of the CO2 absorbed by trees will be released and returned to the atmosphere when the trees eventually die or burn. In comparison the CO2 saved by a SolarDrive Container Power Unit is PERMANENT!
IMPORTANT: Do not let the calculation above stop you from planting trees! On top of the CO2 benefits, they are extremely valuable in many other aspects.