The problem of the "pay back" is that the CO2 they emit is still in the air: the mill does not absorb CO2.
In addition there are different ways to compute a "pay back":
- you may compare the e-kWh production and the fossil-kWh spent to build... Certainly pointless but useful to display short "pay back" durations.
- you may compare your electricity production with the production of the nearby fossil-plant that you pretend to avoid... More realistic, but your project will have different "pay back" depending on the neighborhood you consider (immediate neighbor, regional mix, national mix...).
I can understand such computations in the transition stage where we are, but in the end, each project should be considered for its own [electricity production]/[fossil emissions] ratio across its construction and lifespan.
As we can't go from polluting forms of generation to more neutral sources without building and replacing... Yet it's still worth doing if that will produce lower emissions going forward compared to simply carrying on with the local coal or gas plant.
Doesn't imply this is merely greenwashing, just a small step on route to zero emissions. Where I want to see more significant and far-reaching progress.
To the general point I agree. I'd far prefer to see full impact required for each project, and overall, as well as labelling showing impact of the things we buy - food, consumer goods, vehicles etc, including all those hidden externalities.
In addition there are different ways to compute a "pay back":
- you may compare the e-kWh production and the fossil-kWh spent to build... Certainly pointless but useful to display short "pay back" durations.
- you may compare your electricity production with the production of the nearby fossil-plant that you pretend to avoid... More realistic, but your project will have different "pay back" depending on the neighborhood you consider (immediate neighbor, regional mix, national mix...).
I can understand such computations in the transition stage where we are, but in the end, each project should be considered for its own [electricity production]/[fossil emissions] ratio across its construction and lifespan.