Using the electrical potential created by the electron transport chain to power electrical systems
There are fuel cells that run on alcohols such as ethanol or methanol and on glucose. 

That said, the energy density in current Li-ion cells is quite high - a 18650 cell holds ~30,000 joules, about 9 kCal. By comparison, a  "biochemically" powered shotgun shell (well, the nitrate and carbon of gunpowder can come from bio sources) packs ~2,000 J.