At the heart of each process relevant to our energy supply — ranging from photosynthesis to the workings of solar cells and batteries — is the movement of electrons from one atom or molecule to another. Understanding the mechanisms of eletron transfer is therefore of vital importance.
Elucidating the electron-transfer processes that take place in plants, for instance, might provide the blueprint for mimicking elements of photosynthesis using simpler, artificial systems1,2. This could allow scientists to realize the old dream of splitting water into hydrogen and oxygen by solar radiation with the help of a catalytic system (currently, molecular hydrogen is mostly extracted from natural gas, which requires large amounts of energy). As hydrogen can be converted to other forms of energy through various pathways, such a cheap and efficient source of clean hydrogen could revolutionize our energy resourses.
A hydrogen infrastructure, which would provide electricity from fuel cells or gas and steam turbines, can only become part of our energy mix if ways are found to store and transport molecular hydrogen. Although high-pressure storage or liquid hydrogen are presently the favoured methods, intense effort is being invested to find chemical compounds that offer higher storage den- sities3 — which is crucial for using hydrogen in cars.
Methane, which is the main component of natural gas, could also herald such a clean energy infrastructure. Not only is methane easier to handle than hydrogen, but there are also a number of pathways by which to produce it. One of the most efficient is to ferment biomass in the absence of oxygen; however, to improve the productivity of fermenters we need to understand these biochemical pathways in greater detail — perhaps to the point where we can use genetically modified organisms instead of natural strains.
Whether pure biological pathways or chemical transformations are employed, a fundamental understanding of the genetic and metabolic requirements for high biomass production will improve energy yields4,5.