I'm kicking around the idea of creating a local offset program. My question is: what is the time basis for offsets? Best seen with an example.
Say I build a solar PV system that costs $10,000 and produces enough electricity to offset a tonne of CO2/year for 25 years. If I'm an institution trying to offset emissions, do I buy all 25 tonnes in one year for $10,000, or do I need to buy 1 tonne for $400 and find the rest elsewhere? Or can I do either, as a tonne is a tonne?