Identification and review of the downstream options for the recovery of value from fibre-producing plants: Hemp, Kenaf, Bamboo
JL Broadhurst, T Chimbganda, G Hangone
Fibre-rich plant
?
Post-mining industrial development from fibre-rich plants
?
Conversion
Lead product
Cultivation HarvestPre-
treatmentProductrecovery
Conversion
Plant
biomass
Fibrous-Part
By-products
SeedWater
Non-Fibrous-part(twigs, leaves, seeds etc)
Fibrous-Part
Additional product(s )
Conversion
Processing Manufacturing
Manufacturing
Biorefinery
Biorefinery
High-end
by-products
Key Processing Stages
Bast fibre plants
Bast fibre
Woody core or hurd
Epidermis or bark
Bast fibre plant Bast fibre plant cross section
Different bast plants have a different ratio of bast to woody core
Bast fibre plant properties
Properties Hemp Kenaf
Bast fibre (% in stalk/stem) 25-30 35-40
Fibre fineness (um) 25 to 40 20 to 35
Fibre length (mm) – long fibre 16 to 40 8 to 18
Cellulose (wt%) 70 – 74 45 - 57
Hemicellulose (wt%) 18 -22 21- 23
Lignin (wt%) 4-6 8-13
Tensile Strength (MPa) 550-1000 195-700
STEM
ENTIRE PLANT SEEDS
LEAVES
Example: Hemp
Example - Bioethanol
Energy
Fibre + Woody tissue Leaves or Medicine
Seeds Oilor
Bast fibre crop-to-product profile
Woody tissue
Shives
Construction materials
Short Fibre
Cordage
Paper Pulp
Long Fibre
Bio-compositesBast Fibre
Hurd
&
&
Bast fibre stem cross-section
Conventional textilesIntermediates End-products
70-90%
10-30%
25-40%
60-75%
Bast fibre plant e.g. hemp
Seeds
Stem
Whole plant
Stem
Seeds
Energy (e.g. bioethanol, biogas)
Bast Fibre
Woody tissue/core fibre
Whole seed
Chemicalextracts
Shives (animal bedding etc)
Insulation boards
Oil
ProteinFood
Long fibre
Short fibre
Paper pulp
Leaves
Edible oil (e.g. hemp seed oil)Personal productsPaint/varnishAnimal Fodder
Conventional textiles
Construction composites
CordagePaper pulp
Biocomposite textilesBioplastics
Bioethanol/biobutanol
Human food
or
&
&
or
&
Part of plant Intermediates End-products
&
Medicine
Bast fibre plant multi-product profile
• Hemp and kenaf fabrics are breathable, warm, moisture-wicking,antibacterial and biodegradable.
• Bast fibres can be easily blended with other fibres such as cotton to makelightweight softer fabrics.
Hemp fabric Blended fabrics
Conventional textiles
• Fibre composites are made by embedding plant fibres in synthetic orbiodegradable resins.
• PFRCs are being incorporated into thermoplastic matrix composites and aregaining traction in the automotive and aerospace industries.
Plant Fibre re-inforced composites
• Hemp and kenaf construction products range from insulating panels, non-woven felts for acoustic damping or levelling from woody tissue/hurds tofibre reinforced polymers for façade panels and concrete.
• The most commonly applied product in the building and constructionsector is hempcrete.
Insulation mats
Insulation matting Fibre boards Concrete (hempcrete)
Construction materials
• Paper pulp can be made either from short bast fibre or woody tissue.• Paper made from kenaf bast fibre is reported to be comparable to paper
from some softwoods and most hardwoods• Paper from core fibre or woody tissue (hurd) is not as strong, but is easier to
manufacture as well as softer, adsorbent and more suitable for hygienicproducts.
Paper products
• Hemp and kenaf seeds can either be used as a whole or crushed andpressed to produce oil and a residual seed cake.
• Hemp seeds contain 30% oil by weight, whereas kenaf seeds contain 20%oil.
• Hemp flowers or leaves can be used to make cannabidiols which have lowTHC levels and are used for medicinal purposes.
Hemp seed oil Kenaf seed oil
Pharmaceuticals
• Stems are pre-treated to soften them through retting or degumming, whichcan be chemical, mechanical or high-pressure/temperature processes.
• Bast fibre is separated from woody tissue, into long & short fibre through aprocess known as decortication.
Harvest Retting Decortication
Conversion
Plant biomass
By-products
Leaves &Seeds
Fibre products
Woody tissue
StemConversion
WoodyproductsConversion
FibreStem
Bast fibre processing
Plant
Textiles
Woody tissue
Stem FibreStemHarvest Pre-
treatmentProduct recovery
Spinning
Conversion
Long
ShortCarding
Pulping
Cordage
Composites
Paper
Sorting
PulpingPaper
Conversion
Shives
Seed oilCleaning
Compression
Construction materials
Leaves Cleaning
Conversion
Whole leaves
Seeds Whole seeds
Fibreproducts
Woodytissueproducts
By-products
By-products
Medicine
Spinning
Conversion
Carding
Pulping
Bast fibre multi-product flowsheet options
Environmental & socio-economic impacts
Energy inputs
Water inputs
Job Creation potential
Skills level requirement
Conventional textiles Low Medium High Low
Fibre-reinforced composites
High Low Low High
Construction materials High High Medium Medium
Paper High High Medium Medium
Implications of the various product options
Bamboo plant structure
Culm
Node
Internode
RhizomeShoot
Twigs
Leaves
Roots
Fibre
Endodermis
Exodermis
STEM/CULM
ENTIRE PLANT BRANCHES
Example - Biochar
SHOOTS
Energy
Wood or Fibre or Pulp
Household wood products
Vegetable
Bamboo crop-to-product profile
Fibre
Natural
Rayon
Pulp
Cardboard
Paper Pulp
Wood
OR
OR
Poles
Wood products
Bamboo culm/stem
Intermediates End-products
Whole plant
Culm
Leaves
Energy; biofuels
Strips
Poles
Food
Pulp
Chemical extracts
Fodder (Manure)
Branches Sticks
Medicine
Textiles
Construction materials
FlooringFurniture/decor
Shoots
Part of plant Raw products End-products
Polymer composites
Whole leaves
or
&
&
&
and/or
or
Paper & cardboardRayon fibres
Natural fibres
HandicraftsWoven products
Engineered “wood-based” composites
and/or
Sporting equipment
Mats, blinds, chopsticks
Intermediate products
Culm
Node
Internode
RhizomeShoot
Twigs
Leaves
Roots
Bamboo plant
Bamboo multi-product options
• Bamboo has many applications in the construction and building industriesdue to its woody nature and similar properties to timber.
• The culm is either used whole as poles or split into strips to make wovenproducts or engineered bamboo wood-composites.
Bamboo poles
Woven bamboo strips
Plybamboo boards Strand woven boards
Particle boardsBamboo mat boards
Wood-based products
• There are two types of bamboo textiles – bamboo linen (also called“natural bamboo fibre”) extracted by mechanical or microbial processes.
• Bamboo rayon made through chemical treatments similar to themanufacturing of rayon viscose.
Natural bamboo fibre Bamboo rayon
Fibre-based textiles
• Similar to bast fibre composites, bamboo fibres can be used to reinforcenatural or synthetic polymer matrices.
• Bamboo-fibre reinforced plastic (BFRP) composites’ tensile strength iscomparative to mild steel and have a lower density, making them ideal forstructural applications.
Fibre reinforced composites
• Bamboo has a number of desirable characteristics as a fuel for combustion,such as a low ash content and alkali index compared to other bioenergyfeedstocks.
• Bamboo culm can be processed into pellet form or other forms of fuels,such as biogas, bioethanol and charcoal.
Energy-based products
• Each product type requires a separate treatment or processes.• Bamboo processing is more intensive and extensive than bast fibre
processing
Harvest Splitting Fibre recoveryPlantCulm
By-products
LeavesShootsBranches
Strips
Conversion Wood-basedproducts
Strips
Treatment Poles
Conversion
Energy-based products
Wholeplant
Conversion
Fibre-based products
Pulping/Conversion Paper products
Conversion
Bamboo processing
HarvestPlant
Plybamboo/
Burning
Pulping
Energy
Board making
Splitting
Option 1a
Low quality stems/wastes from options 1 and 2
Whole plant (100%)
Top of culm
Culm (80%) High-end
products
Strand woven boards
Bamboo mats
Particle board Low-End or bulk
products
Fibre recovery
Weaving
Board-making
High quality stems
Option 1b
Option 2a
Board making
Natural fibre
Option 2bMDF boards/
Poles
Medium quality stemsPre-treatment
Bamboo mat boards
Paper pulp Option 3a
Option 3b
Option 3c
Medium-value
products
Bamboo multi-product processing scenarios
Environmental & socio-economic impacts
Energyinputs
Waterinputs
Job Creation potential
Skills level requirement
Wood-based products Low Medium High Low
Fibre-based textiles High High Medium High
Fibre re-inforced textiles High High Medium Medium
Energy products Medium Medium High Medium
Implications of the various product options
Leadproducts
Cultivation HarvestPre-
treatmentFibre-
recoveryPlant Fibrous-Part
SoilWater
FibreFibrous-Part
Additional products
Manufacturing
Non-fibrous parts Leachate (metals)
(metals)
AshingBio-ore
Hydrometallurgical/pyrometallurgical
extraction Metals
Plant-synthesised nano-catalysts
Manufacturing
Potential integrated metal recovery process
• All the fibre-producing plants can generate multiple products however,the range of products and targeted markets differ for the different planttypes.
• There appear to be few holistic or systemic studies on the selectionof products and processing of fibre-rich plants.
• This review shows that the selection of product recovery and treatmentprocesses is highly dependent on desired product types and output oflow-end vs high-end value products.
Summary
Lead to by-product
ratio
Processing methods
Product qualitySite specific
factors
Socio-economic impacts
Environmental impacts
Multi-product potential
The exploitation of fibre-based plants will depend on….
• Bast fibre plants appear to be the best downstream option for the productionof “green” textiles and high-end niche products such as fibre-reinforcedcomposites.
• Bamboo is more suitable as a replacement for conventional timber in theproduction of functional products such as wooden flooring and constructionmaterials and paper.
• Further studies will be required to investigate the effect of contaminants onproducts and processing options.
Summary