Which solution had the highest net MTCO2E reductions?

Which solution had the highest net MTCO2E reductions?
Which solution had the highest net savings?
Which solution did you find the most exciting and why?
Which solution do you think is most easily implemented and why?
Which solution do you think will be the most difficult to implement and why?
Select one solution and generate a high-level, conceptual business plan. Do not be shy about scale or ambition when developing your concept. We have an existential crisis facing the human race we need big ideas. Include the following components of your business plan concept:
Description of product/service
Description of the problem your product/service is trying to solve
Rough business model for your concept (i.e. how would it make money? What are the operating costs?)