Before the discovery of cellulolytic enzymes, processes that could
thermochemically hydrolyze lignocellulosose to produce soluble sugars were
studied and developed with some commercial use during wartime periods.
Most of these processes were operated under fairly severe conditions and
typically utilized concentrated acids at relatively low temperatures (200°C).
Such harsh conditions generally resulted in relatively low recoverable sugar
yields due to sugar degradation reactions that produced primarily aldehydes
and organic acids, along with other undesirable compounds.
Advances have been made in thermochemical acid hydrolysis processes to
improve their commercialization potential in some niche opportunities,
especially for concentrated acid processes.