Standard approaches to green energy are great for consumers, but aren’t very useful for larger machinery, or huge cargo ships. The battery technology powering your Prius or the windmills that dot open landscapes don’t produce enough energy to get a containership from Stockholm to San Francisco. So what’s the answer? Well, it has to be a combustible liquid that produces energy, and that might come from bacteria that produce biofuel as a byproduct of their metabolism. The science still needs to be worked out but includes engineering the proper bacteria to eat the right kind of yeast, but the idea isn’t that far fetched. Similar approaches have been used to make ethanol for years. Who knows, maybe cruise ships of the future will be powered by gas emitting microorganisms eating engineered yeast.