Abstract: A liquid suspension of lignin-rich microparticles can be recovered from anaerobic digestion of ruminant animal manure. This has similar particle size distribution to that obtained from anaerobic digestion of steam pretreated lignocellulosic feedstocks. This demonstrates that similar lignin-rich microparticles can also be formed biologically, in the absence of thermal treatment that melts lignin. As a consequence, given a sufficiently complete digestion, lignin-rich microparticles will be formed during anaerobic digestion of ruminant manure and of lignocellulosic feedstocks that have never been steam pretreated to temperatures above the lignin melting point. Methods for recovering and valorizing this lignin are disclosed.

Abstract: Where hydrothermal pretreatment of lignocellulosic feedstocks is conducted so as to avoid agitation, melted lignin microdroplets remain very small in size, typically <3 ?m. Carrying a net negative surface charge at neutral pH, the solidified microdroplets can be recovered from biogas digestate or process effluents from other biological conversion systems as a liquid fraction following solid/liquid separation to remove fibers, silicates and other suspended solids. This liquid suspension can be concentrated and used directly in chemical and thermochemical conversion systems with or without catalysts. Alternatively, the lignin microparticles can be flocculated and collected as a purified solid fraction. The solids can be solubilized in NaOH at room temperature as wet filter cake and used for base catalysed depolymerization or as fundamental reagent in production of phenolic resins, binder and dispersants.

Abstract: Hydrothermal pretreatment of mechanically compressed straw in unagitated reactors provides a simple and inexpensive solution to poor C5 monomer yields with autohydrolysis processes. Unlike raw straw, compressed straw pellets or briquettes can be pretreated on commercial scale using unagitated batch reactors or simplified unagitated continuous systems. The chemistry of hydrothermal pretreatment is thereby altered such that loss of C5 sugars to unwanted byproduct reactions is reduced. With compressed straw, water content can be introduced within the reactor while it is pressurized, which reduces energy costs and capital expense. Provided are methods of processing straw feedstocks using semi-continuous or continuous systems and a pretreatment reactor adapted to processes compressed straw with high throughput through a small reactor volume in which water content is added within the reactor under pressure.