This 4 billion dollars and all the money wasting on power and ASIC chips is a direct tax on the bitcoin ecosystem. This is the incentive you and your currency/consensus model have to beat bitcoin. In addition to the engineering problem, the number of people worldwide who prioritize environmental preservation mean that a currency that can preserve or even improve the environment are going to be preferred. What if we changed proof of work to be proof of not-cutting-down rainforests? 100 secure micro-satellites circle the globe taking pictures of areas prone to deforestation and distribute currency based on the areas not being logged?