Conversion of lignin and forestry/agricultural biomass/residues into bio-energy/bio-fuels and industrial bioproducts (bio-based platform chemicals and functionalized polymeric materials), value recovery from wastewater sludge, food processing/greenhouse wastes and oil sands process-affected water and tailings, and applications of biomass in metallurgical processes, etc. The specific research activities include:
(1) Biorefining technologies: conversion of lignin and agro-forestry biomass/residues into bio-based platform chemicals and functionalized polymeric materials
Being a recognized leader in biorefinery research, Dr. Xu with his group developed novel low-T/low-P lignin de-polymerization processes, realizing cost-effective conversion of kraft lignin (Mw ~ 10,000 g/mol) or black liquor and hydrolysis lignin (Mw unmeasurable) into de-polymerized lignin (DL) of a lower molecular weight (Mw ~ 1,000-2,000 g/mol) at a high yield (70-90 %). PCT/US/Canadian patents were filed (File # PCT/CA2018/050546; File # 62/503376) and have been licensed to the Industrial Partner (FPInnovations) for commercialization. The DL and liquefied woody biomass/barks have been successfully utilized as bio-based platform chemicals such as bio-phenol for production of bio-based phenol formaldehyde (BPF) resins/adhesives/foams, bio-polyols for polyurethane (BPU) resins/foams, or bisphenol-A replacement for the synthesis of lignin-based epoxy resins. On the other hand, an integrated biorefining process has been developed for high-value utilization of two major agricultural bioresources, i.e., starch from crops (corn/ wheat/potato) and cellulose/lignin fractionated from crop residues (e.g., wheat straw/cornstalk) or other energy crops such as switchgrass and mithcanthus, for the production of bioplastics (based on starch/cellulose acetate), carboxymethylcellulose (CMC), BPF wood adhesives, and hydrophilic BPU foams as hydroponic growing media for greenhouse planting, etc.
(2) Hydrothermal conversion technologies for recovery of water and bioproducts from water-containing wastes and bioresources
It has been a long-standing challenge for management of water-containing wastes, such as greenhouse residues, food processing wastes, wastewater sludge, microalgae, manure, etc. as it requires costly de-watering/drying operation for conventional thermal/thermochemical processes (incineration, pyrolysis or gasification), a long HRT (from days to weeks) for biological treatments (AD or fermentation). It generates secondary environmental issues (emissions of leachate and GHG) for landfilling. Our research team is among the world’s pioneering leaders in development of efficient and cost-effective hydrothermal conversion processes for recovery of water and bioproducts from water-containing wastes and bioresources. For example, with hydrothermal liquefaction (HTL) or hydrothermal carbonization (HTC) process, water-containing wastes and bioresources can be treated directly, without the need of drying for the feedstocks, and efficiently converted into valuable bioproducts, i.e., bio-crude oils or bio-char, under mild operating conditions (50-100 bar, 200-350 °C), while recovering water. A two-stage HTL process for co-production of bio-crude and biogas from wastewater sludge while recycling water, has been developed, with US/Canadian/Chinese patents pending (File # PCT/CA2016/051239, China Entry application W-16-013 CN July 27, 2019), which was recently licensed to Energy Research Institute of Jiangxi Academy of Science for commercialization. In addition, we’ve developed a continuous-flow supercritical water gasification (SCWG) process for generation of renewable H2 and CH4 as well as clean water from high-COD wastewater from food processing industry or landfill leachate or other wet bioresources.
(3) Catalytic conversion of glycerol/sugars to platform chemicals
Inexpensive heterogeneous catalysts and continuous-flow processes have been developed for conversion of glycerol (a byproduct or waste stream generated in bio-diesel industry) to high-value green chemicals (such as solketal as fuel additive, 1,2-propanediol, 1-propanol, etc.), and glucose/fructose into platform chemicals, i.e., 5-hydroxymethylfurfural (5-HMF) and furan dicarboxylic acid (FDCA) for the synthesis of polyethylene furanoate (PEF) – a bioplastic replacing PET. PCT/Canadian patents were filed on 29 June 2017 (File # PCT/CA2017/050792).
(4) Treatment of oil sands process-affected water and tailings for value recovery
Highly porous activated petroleum coke (APC), with BET specific surface area up to 2000 m2/g and a total pore volume over 1 cm3/g, has been produced and applied as cost-effective and efficient adsorbents with tailored structure/surface properties in treatment of oil sands process-affected water (OSPW) and tailings for recovery of naphthenic acids (NAs).
(5) Biomass applications as alternative fuels and reductants in metallurgical processes
Steels are by far and will continue to be the most widely used metallic materials in our society. However, production of steel from iron ores is highly energy intensive, demanding substantial amounts of fossil-based coal and coke as energy source and reductant, resulting in immensely high greenhouse gas emissions. The worldwide steel production contributes to approx. 5-6% of the world’s total greenhouse gas emissions. Hence, there have been considerable efforts over the years in examining the use of biomass-based materials in place of coal and coke in metallurgical processes. In recent years, our group have been working utilizing lignocellulosic biomass, lignin or HTC bio-char as alternative fuels and reductants for blast furnace injection or iron-ore sintering, as carbon-containing binders for iron ore carbon composite pellets manufacture, or as activated carbon for sintering flue gas SOx/NOx emission control.
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