Pretreatment of lignocellulose using two stage alkali and mechanical refining processes

A method for treating lignocellulosic biomass for ethanol production, comprising:

• (i) reacting the lignocellulosic biomass with a first alkali to produce a first stage biomass;
• (ii) dewatering the first stage biomass to isolate a first stream of first stage solids;
• (iii) reacting the first stage solids with a second alkali to produce a second stage biomass;
• (iv) dewatering the second stage biomass to isolate a stream of second stage solids;
• and
• (v) mechanically refining the second stage solids, comprising the use of at least one of a single disk mill, a double disk mill, a conical plate mill, a pin mill, a ball mill, a Szego type mill, an attrition mill, an ultrasonics-assisted mill, a stone-wheel grinding mill, or a homogenizer.

A method for upgrading lignin monomers resulting from deacetylation and mechanical refining of a lignocellulosic biomass, comprising:

• (i) reacting the lignocellulosic biomass with a first alkali to produce a first stage biomass;
• (ii) dewatering the first stage biomass resulting from step (i) and isolating a first black liquor stream from first stage solids generated from the reaction of the lignocellulosic biomass with the first alkali;
• (iii) reacting the first stage solids from the step (ii) with a second alkali to produce a second stage biomass;
• (iv) dewatering the second stage biomass resulting from step (iii) and isolating a second black liquor from second stage solids generated from the reaction of the first stage biomass with the second alkali;
• (v) oxidizing lignin monomers in at least one of the first black liquor and the second black liquor to yield one or more quinones;
• and
• (vi) performing a Diels Alder reaction with an alkene and the one or more quinones to yield one or more cyclic adducts.