This report finds 10% as a lower bound and 60% as an upper bound for the energy efficiency of hydrogen oxidizing bacteria: "The energy efficiency of carbon dio

This report finds 10% as a lower bound and 60% as an upper bound for the energy efficiency of hydrogen oxidizing bacteria: "The energy efficiency of carbon dioxide fixation by a hydrogen-oxidizing bacterium" https://sci-hub.ru/10.1016/j.ijhydene.2013.04.153 https://sci-hub.ru/10.1016/j.ijhydene.2013.04.153 The authors found a tradeoff between efficiency and growth rates. The highest efficiency came with the slowest growth rate. But they concluded that 50% efficiency was achievable at practical growth rates. Keep in mind also that potatoes only contain about 10% protein by dry weight while the bacteria cultivated to make single cell protein can contain 50% protein by dry weight. Soybeans are about 40% protein.