Alternative Uses for Lignin

Lisa Lai

Tuesday, April 28 2009

Outline

• A review of lignin chemistry• Current use and isolation• Arboform: lignin plastic• Lignosulfonates

– In building materials– Other uses

• Conclusions

Lignin

• 3-dimensional phenolic polymer

• Complex structure• Composes ~15-40% of

lignocellulosic biomass• 2nd most abundant

natural polymer

Sakakibara

Lignin monomers

Lignin Source Grasses Softwood Hardwood

ρ-Hydroxyphenyl 10-25% 0.5-3.5% Trace

Guaiacyl 25-50% 90-95% 25-50%

Syringyl 25-50% 0-1% 50-75%

Lignin linkages

O H

O C H 3

C

C

C

1

2

3

45

6

-O -4 L in k a g e

O RH C

O

O C H 3

C H

H C

C H 2O H

H C

H O H 2C

O H

O C H 3

Linkage Softwood Hardwood

β-O-4 50% 60%

α-O-4 2-8% 7%

β-5 9-12% 6%

5-5 10-11% 5%

4-O-5 4% 7%

β-1 7% 7%

β-β 2% 3%

Lignin: proposed structures

Adler Freudenberg

Lignin: more proposed structures

Forss

Nimz

Lignin: current use

• In Kraft pulping, lignin is recovered in black liquor

• 50 million metric tons produced annually worldwide

• ~95% of this is incinerated for thermal electrical energy

• Burning generates an average fuel value of 23.4 Mj/kg

Arboform

• A lignin-based thermoplastic• Made from a mixture of lignin, plant fibers, and waxes• Developed by German company Tecnaro in 1998• Appearance and some physical properties similar to wood• Moldable like plastic

Arboform: chemical properties• Pelletized mixture of lignin,

fine fibers of wood, hemp or flax, and wax– Up to 50% lignin

• Liquifies at temperatures as low as 170°C– Polypropylene: ~160°C– Polyethylene: 105-120°C– Polystyrene: ~240°C

• Thermally stable up to 105°C• Can be injection molded

similar to conventional plastic

Arboform: physical properties

• Better molding capabilities than plastic

• Irregular fiber orientation resists warping– Flooring & building material

• Good acoustic properties (speakers & musical instruments)

• Currently 300 metric tons produced annually

An alternative to plastic?

• More than 100 million metric tons of plastics originating from crude oil are produced annually (worldwide)

• The pacific trash vortex is twice the size of Texas, reaches 300 feet below sea level, and 90% of it is plastic

Arboform: Pros and Cons

Advantages:• Completely

biodegradable• Can be burned after

use• Not made from crude

oil• At least as strong as

plastic

Disadvantages:• Some forms are not

water resistant• Requires removal of

sulfur• Cost: $1.60/lb,

compared with less than $1/lb for polypropylene

Lignosulfonates

• Produced in the acid sulfite pulping process• One metric ton of pulp produces 330-540 kg of

lignosulfonate

Sodium lignosulfonates as plasticizers for concrete

• Concrete is formed by mixing:– Water– Cement– Aggregate

• Lignosulfonates reduce the amount of water needed, making concrete stronger

• World revenue generated from lignosulfonates estimated at $490-550 million

Sodium lignosulfonates as plasticizers for concrete• SEM images of Portland

cement (b) without, and (c) with the addition of lignosulfonate

• Lignosulfonate inhibited hydration of cement

• Exact mechanism is unknown, but adsoption of lignosulfonates on the surface of cement particles is suspected

Other uses for lignosulfonates• Dispersant

– Chemical dyes, plasterboard

• Binder– Dirt roads

• Emulsifier• Chelating agent• Food additives

– Vanillin

Conclusions

• Lignin has a number of potentially valuable uses

• More research will be needed in order to make production of these materials cost-effective

• Market conditions will have to change in order for Arboform to become competitive with conventional plastic

Thank you!

Questions?