of three components, each with properties that pose challenges to commercial applications.

*lignin is a heterogeneous, highly crosslinked polymer akin to phenol-formaldehyde resins. It is derived from 3-4 monomers, the ratio of which varies from species to species. The crosslinking is extensive. Being rich in aromatics, lignin is hydrophobic and relatively rigid. Lignin confers structural integrity to plants. Lignin is so heterogeneous and so recalcitrant