Natural conversion of cellulosic biomass to energy by ruminants and fungi is slow partly because it must be compatible with living organisms. Industrial conversion of cellulosic biomass to energy can use a wider range of reaction conditions and intermediates. We propose the use of unnatural enzyme-catalyzed reactions. The unnatural part allows the use of faster more efficient reactions. The enzyme catalysis is efficient and allows multiple simultaneous reactions, which are needed to release sugars from a complex multi-component material like cellulosic biomass. One example reaction is enzyme-catalyzed formation of peractic acid. Peracetic acid is a strong oxidant that effectively alters lignin allowing subsequent release of sugars by cellulases and xylanases. Perhydrolases catalyze the formation of peracetic acid from hydrogen peroxide and acetic acid or acetate esters. The levels of peracetic acid formed are high enough effectively pretreat aspen wood. Another example is cofactor-independent hydrogenation using hydrogen directly. By replacing natural metals in the active site of an enzyme with unnatural hydrogenation catalysts, we have created an enzyme that uses hydrogen directly. The shape of the active site controls selectivity of the hydrogenation.