We, schools in the ENO Programme, aim to plant 100 Million Trees by 2017. This commitment was given in Rio+20 Summit and highlighted there. BBC's environmental correspondent said that out of 700 commitments, it was "the most dynamic-sounding pledge on the register". It is, but here are other numbers of how much 100 million trees would tie carbon:
If those trees would stay 100 years and grow to 30 metres we can calculate (optimistic) the amount of carbon like this: Volume PPA 1 m^2 x 30 m / 3 = 10 m^3, biomass 6 tons, and 3 tons carbon.
As the value of a carbon ton is 10USD, those trees would then tie 300 million tons of carbon and the value of carbon would be 3 billion USD.
A more realistic estimation could be 1/10 of that including the loss of trees. And one cannot estimate the value of a carbon ton in a long run. But we will certainly make a difference, schools and children around the world!