Acid Hydrolysis of Cellulose

This is ancient technology. I was in St. Petersburg when its name was Leningrad and visited a factory that made ethanol from wood. The workers sampled the ethanol frequently, and I was expected to comment that it tasted great. The carbon dioxide from the fermentation was compressed and sold. About 40 other factories were in operation throughout the Soviet Union, but the economics were marginal.

Batch hydrolysis by adding wood chips to hot, dilute sulfuric acid yields only about 50% of the theoretical fermentable sugars. Research on the reaction kinetics and new reactor design have improved the yield considerably.

Problems are:

sugary side products are formed that may inhibit the ethanol fermentation

the spent acid is neutralized with lime creating a sludge for disposal