A-Z Knowledge on Wood-derived Chemicals
A-Z Knowledge on Wood-derived Chemicals
The main chemical components of wood are cellulose, hemicellulose, lignin and extractives.
Paper manufacturers, wood bio-refineries and extraction companies already isolate such wood constituents for
the manufacture of a broad range of products. These products are successfully marketed in many applications today, such as:
- Paper and paperboard
- Cosmetics
- Food supplements
- Pharmaceuticals
- Specialty chemicals
- Detergence
- Aroma
- Construction materials
- And more
However, wood chemicals continue to offer opportunities
for new product developments. These products can meet the requirements of various industrial sectors in search for
new effect and bio-based chemicals alternative to oil-based products.
R&D initiatives are currently very dynamic in this area. Let's take a look at the advances in wood biomass-derived chemicals...
R&D Projects for the Valorization of Wood Cellulose
R&D Projects for the Valorization of Wood Cellulose
Nanocellulose
Research initiatives focus on the use of nanocellulose as a strength enhancing additive for renewable and
biodegradable matrix polymers such as PLA. Research also concentrates on the development of porous nanocellulosic materials for insulation &
packaging.
New coatings are also being developed with outstanding barrier properties in food packaging and printing
paper applications.
New developments concentrate on the use of nanocellulose as a rheological modifier in cosmetics
(thickener), pharma (tablet binder) and paint applications.
Levoglucosenone (LGO)
Levoglucosenone (LGO) is a biology derived chemical which can be produced from waste cellulose. Current
developments focus on LGO conversion to new polar aprotic bio-solvents. These new solvents are
alternatives to NMP, DMF and DMAc which are under significant regulatory pressure worldwide due to
their toxicity.
R&D Projects for the Valorization of Lignin from Wood
R&D Projects for the Valorization of Lignin from Wood
Carbon Fiber
Lignin represents a potential low-cost source of carbon suitable for displacing synthetic polymers, such as:
Polyacrylonitrile (PAN) in the production of carbon fiber.
Using lignin in the carbon fiber manufacturing
process improves:
- Raw material availability
- Decreases raw material sensitivity to petroleum cost, and
- Decreases environmental impacts
The goal of replacing steel panels with lightweight, yet strong, carbon
fiber-reinforced plastics is to significantly reduce vehicle weight and improve fuel economy.
Resins and Adhesives
Resins and adhesives offer a large opportunity, especially for formaldehyde-free applications.
Formaldehyde is currently considered a carcinogen and its banishment from consumer and packaging
goods and building products is highly likely in the near term.
Technical needs and challenges for lignin in
this area center on:
- Effective, practical means for molecular weight and viscosity control
- Functional group enhancement to improve oxidative and thermal stability, for example:
- Carbonylation
-
Carboxylation
- Amination
- Epoxidation, and
- De-etherification
- Consistent mechanical processing properties
- Control lignin color, and
- Precise control of cure kinetics
Product consistency in these application targets will also
be a technical challenge.
Polymer Modifiers
Polymer modifiers can be simple, low-cost fillers or may be high-value additives that improve various
polymer physical or performance properties. Currently, lignin use concentrates on the former; Current
research is concentrating on the latter by creating technologies that improve polymer:
- Alloying
- Mutual solubility
- Cross-linking, and
- Control of color
Relevant technologies include:
- Predictable molecular weight control
- Facile introduction of reactive functionality, and
- Polyelectrolytic functionality
Monomeric Molecules
Very selective depolymerization, also invoking C-C and C-O bond rupture, could yield a plethora of complex
aromatics that are difficult to make via conventional petrochemical routes. These complex aromatics include:
- Propylphenol
- Eugenol
- Syringols
- Aryl ethers
- Alkylated methyl aryl ethers
Research is concentrating on developing technology that would allow highly selective bond-scission to capture the monomeric lignin building block structures. However, markets and applications for monomeric lignin building blocks would need to be developed.
This development is therefore longest-term and currently has unknown market pull for large-scale use. Since, most of the chemical industry is used to single, pure-molecule raw materials, using mixtures of products in
a chemical raw material feed, as would arise from lignin processing, constitutes a challenge.
BTX Molecules (Benzene, Toluene, Xylene)
Developments concentrate on non-selective depolymerization technologies in the form of C-C and C-O
bond rupture. This can lead to the production of aromatics in the form of BTX plus phenol and includes
aliphatics in the form of C1 to C3 fractions.
Development of the required non-selective chemistries is part of the long-term opportunity. But, it is likely to
be achievable sooner than highly selective depolymerizations. In fact, some of the past hydro-liquefaction
work with lignin suggests that, with further development, this concept is a good possibility.
R&D Projects for the Valorization of Sugars from Wood
R&D Projects for the Valorization of Sugars from Wood
Single Cell Protein (SCP)
SCP consists of microorganisms such as filamentous fungi, yeast, algae, and bacteria that are rich in
protein. R&D projects are ongoing to use sugar streams generated by wood biorefineries for the
production of single cell protein.
SCP can be used as a protein source in fish feed. SCP can be more a nutritional alternative to the current
products used in the aquaculture such as soybean meal in particular. SCP has a high B vitamin content and
a tunable amino-acid profile. This GMO-free product is safe, nontoxic and contains no fatty acids.
Bio-surfactants
Industrial research focuses on the development of new bio-based surfactants, thickeners, emulsifiers,
texturing agents from C5 and C6 pure sugars derived from wood hemicelluloses.
These research initiatives
are market pull projects to meet the requirements of the cosmetics industry in a continuous search for new
bio-based products and effects.
Bio-based Polymers
There are R&D initiatives which focus on the conversion of C6 sugars (glucose, mannose) derived from
wood hemicelluloses to diacid and diamines monomers. They are then used for the development of bio-based polyamides.
Bio-fuels
R&D initiatives are focused on the development of new biomass fractionation technologies, like:
- Acid-based
- Enzyme-based
- Solvent-based, or combinations of these chemistries
- Supercritical water hydrolysis
- Steam explosion…
All these technologies can economically fractionate the wood biomass to sugar and lignin streams which all
need to be valorized.
Research concentrates on developing the most efficient process (biomass treatment,
enzymes production, fermentation and distillation) to produce a cost competitive 2G ethanol equivalent to 1G
bioethanol.
Bioethanol Production from Biomass
R&D Projects for the Valorization of Extractives from Wood
Wood Chemistry Reinventing Polymers for a Greener Future
Wood Chemistry Reinventing Polymers for a Greener Future
Environmentally friendly materials have become more widely used as consumers became aware of the consequences associated with the use of petrochemical-derived products.
By using renewable resources, the industry reduces the use of fossil resources and the amount of carbon dioxide that is present in the atmosphere.
The development of novel biomaterials derived from wood biomass and produced with a reduced carbon footprint contributes to this sustainable approach. These materials improve resource management and the overall performance and efficiency of our environment. Wood chemistry can contribute to reinvent plastics for a greener future.
Let's take a look at the wood-biomass derived materials...
Biopolymers Derived from Wood Extractives
Bio-based Polymers Derived from Wood-based Lignin
Bio-based Polymers Derived from Wood-based Lignin
Paper-making and other wood-pulping processes produce 70 million tons of lignin byproduct each year, 98% of which is incinerated to generate energy. Lignin can also be an important source of synthetic materials because of its:
- Abundance in nature
- Low cost
- Stable supply, and
- No competition to the human food supply
Lignin, a cross-linked phenolic polymer, contains a large number of aromatic groups that can be used as a substitute for petroleum‐based aromatic fine chemicals.
Explore the following bio-material advances from wood-based lignin.
Lignin-based Composites
Mixing lignin with natural fibers such as flax, hemp or other fiber plants and some natural additive produces lignin-based fiber composites. These can be processed on conventional plastics processing machines. Lignin-based composites can be used for the manufacture of various products such as computer, television or mobile phone casings.
Wood-based lignin can also be used as a copolymer in Bio-composites. Poly-lactide (PLA) is a biodegradable polymer formed from the polymerization of microbially produced lactic acid.
However, PLA confers low physical properties such as impact strength, small elongation at break, suboptimal thermal properties. The development of lignin/PLA composites can contribute to boosting the thermal and mechanical properties of PLA.
Wood-based Lignin alternative to Bisphenol A
Wood-based lignin a highly available renewable resource, can also be a safer, greener alternative to bisphenol A (BPA) in various applications:
- Adhesives
- Coatings
- Electronic equipment
- Food packaging, and
- Containers
Approximately 3.5 million tons of BPA are produced annually worldwide. The downside is that bisphenol A can mimic the hormone estrogen, potentially affecting the body and brain.
Researchers have found that lignin fragments can be converted into a compound called bis-guaiacol-F (BGF), which has a similar shape to BPA. R&D developments are ongoing to design BGF which cannot interfere with hormones but can keep the desirable thermal and mechanical properties of BPA.
Lignin-based Adhesives
Due to its abundant presence of phenolic groups, wood-based lignin can potentially replace phenol in phenol–formaldehyde (PF) resins in wood composite adhesives. Such adhesives can be used in the production of plywood, particle board and other kinds of wood composites. PF is highly toxic chemical and an irritant to the eyes and respiratory tract. Moreover, PF resins can be very expensive, because of the fluctuating price of phenol. Therefore, replacing current synthetic PF resins based on petrochemicals offers great economic and health benefits.
Lignin-based Adsorbents
Lignin-derived products can be used as adsorbents of selected heavy metals and toxic organic compounds. Black liquor lignin from the pulp and paper industry can be used as a precursor for activated carbon. The lignin is carbonized in an oxygen-free atmosphere and the resulting carbon is then activated with steam. The resulting lignin-based activated carbon is considered to have the potential for use in dye wastewater treatment.
Lignin-acrylamide-based Flocculant
Chemically modified lignin can be used as a flocculant. Flocculants, often positively charged molecules, are used to remove suspended solids from liquids by forming aggregates of colloids and other suspended particles that precipitate and play an important role in wastewater treatment and the removal of contaminants to prepare potable water.
Environmentally friendly flocculants that are nontoxic and biodegradable are highly desirable. Acrylamide grafted onto a lignin backbone has flocculant properties. The positively charged lignin-acrylamide has the ability to coagulate aluminum and enhance the removal efficiency of dissolved organic carbon.
Lignin-based Carbon Materials
Lignin can be used as a precursor for carbon fibers as an alternative to high-cost precursors such as polyacrylonitrile (PAN). Moreover, the impact on the environment caused by toxic by-products such as hydrogen cyanide (during PAN processing) has raised serious concerns. Renewable, bio-based alternatives for carbon precursors are being developed, and the carbonized structure of lignin allows it to be used as renewable, low-cost graphitic carbon materials.
Lignin-based carbon materials such as fibers, mats, nanofibers, and mesoporous carbon have been successfully developed by a number of research groups.
Bio-based Polymers from Wood Sugars
Bio-based Polymers from Wood Sugars
The major component of wood biomass is cellulose. Since about half of the organic carbon in the biosphere is present in the form of cellulose, the conversion of cellulose into valuable chemicals has a paramount importance. The depolymerization of cellulose results in the formation of glucose.
Hemicellulose is the second most abundant polymer. Unlike cellulose, hemicellulose has a random and amorphous structure, which is composed of several heteropolymers including:
- Xylan
- Galactomannan
- Glucuronoxylan
- Arabinoxylan
- Glucomannan, and
-
Xyloglucan
Wood Sugars - Extraction and Value
Hardwood hemicelluloses contain mostly xylans, whereas softwood hemicelluloses contain mostly glucomannan. The depolymerization of hemicellulose results in the formation of glucose as well as the other C5 sugars (xylose, arabinose) and C6 sugars (mannose, galactose, rhamnose).
There are different techniques to extract wood sugars using a variety of wood fractionation technologies such as:
- Dilute acid
- The steam explosion followed by enzymatic hydrolysis
- Supercritical fluid
- Concentrated acid, and
- Organosolv processes
Once isolated, cellulose, hemicellulose, and lignin can be converted and/or incorporated into a wide range of materials.
The polysaccharides are deconstructed into monomeric hexose C6 and pentose C5 sugars which are then converted into a wide range of value-added building-block chemicals and bio-based polymers:
- C5 and C6 sugar derived building-block chemicals include 1,4-diacids (succinic acid, fumaric acid, malic acid), 2,5-furan dicarboxylic acid (2,5-FDCA), 3-hydroxy propionic acid (3-HPA), aspartic acid, glucaric acid, glutamic acid, itaconic acid, levulinic acid, 3-hydroxybutyrolactone (3-HBL), glycerol, sorbitol and xylitol/arabinitol.
- Examples of important commercial polymers derived from the 1,4-diacid platform are PBS and its copolymers, PBT resins and yarns, PTMEG, P4HB, Polyamides PA-4,6, PA-4,10. Polymers derived from the 2,5-furan dicarboxylic acid platform (2,5-FDCA) can be the 100% bio-based polyethylene-furanoate polymer (PEF) used in bottles, fibers, and films applications.
Polyhydroxyalkanoates (PHAs) are bio-polyesters which can be produced by levulinic acid. Polylactic acid (PLA) is derived from lactic acid (LA) which is mainly produced via the fermentation of glucose and sucrose by lactic acid bacteria. PLA is mostly used in food, beverage, and pharmaceutical and personal care applications.
Therefore, there is a strong potential for the valorization of sugars streams from wood. Indeed, wood biomass presents a growing interest because it does not compete with food or feed production. It can increase sustainability by providing a new source of industrial sugars which are important building blocks for various basic chemicals and intermediates. Wood sugars could, therefore, be a future alternative to sugars currently generated by agro-refineries for the manufacture of biopolymers.
However, the techno-economic viability of efficient and sustainable processes for fractionation of wood into sugars and lignin and to further conversion of both fractions into high added value products still need to be demonstrated. New wood-based value chains need to be achieved for the production of chemical building blocks, materials and biofuels (other than ethanol) in a cascading approach, by a combination of biotechnology and chemical processes.
Bio-based Polymers from Wood Cellulose
Bio-based Polymers from Wood Cellulose
Softwood is the dominant raw material used in the production of cellulose plastics. To isolate cellulose fiber from the biomass:
The wood is cooked or heated in a digester resulting to the production of pulp
(Pulp chemical composition consists of hemicelluloses and alpha cellulose)
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Residues of resins and lignin are removed by treating the pulp with bleaching agents
(This bleaching step also contributes to the reduction of hemicelluloses content of the pulp)
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Water is then taken out of the pulp before processing the pulp with high alpha cellulose content
↓
The pulp is reacted with certain acids and anhydride to produce cellulose esters used in the production of cellulose plastics
Cellulose esters are available in various:
- Types
- Viscosities
- Butyryl and acetyl ratios, and
- Hydroxyl contents
Cellulose acetate is one of the most important esters of cellulose. Depending on the way it has been processed, cellulose acetate can be used for great varies of applications such as films, membranes or fibers. Cellulose acetate butyrate can be used as binders and additives in coatings applications for a variety of substrates, including:
- Plastics
- Textiles
- Metal, and
- Wood
Cellulose acetate propionate is used in various applications such as printing inks, varnishes, nail polish, lacquers, and many more which require:
- Low odor
- Clarity
- Fast solvent release
- Anti-blocking, and
- Good adhesion to a variety of substrates
Barriers to the Development of Wood Biomass-derived Bio-products
Barriers to the Development of Wood Biomass-derived Bio-products
The most important barriers towards the development of wood bio-based products market are their high pricing in terms of purchase and the technological barriers that still face many of the related processes.
Bio-based products are more expensive than their fossil-fuel derived equivalents. This is because of:
- High feedstock prices, and
- High capital and operating costs of related production processes
Many of which are still at an R&D, or demonstration level. The low prices of fossil fuels in the last years worsen the situation as they make the use of wood biomass feedstock economically unattractive.
Let's take a look at the major barriers for a sustainable production and market development of bio-based products derived from wood biomass.
Feedstock Related Barriers
Technology Related Barriers
Market Related Barriers