Biomaterials from Renewable Resources

Question 1

What is the definition of a lifecycle assessment?

Answer 1

• A systematic set of procedures for compiling and examining the inputs and outputs of materials and energy and associated environmental impacts directly attributable to the functioning of a product or service throughout its lifecycle

Question 2

Draw the Lifecycle assessment diagram

Answer 2

Question 3

Describe the key features of the life cycle assessment diagram

Answer 3

2 inputs
- Raw Materials and energy
2 outputs
- Main product and biproducts
3 environmental impacts
- Atmospheric, water and solid wastes
4 process steps
- raw material acquisition
- Manufacturing
- Operation/use/maintenance
- Recycle/waste management

Question 4

There are actually 8 different impact categories, what are they and how are they measured?

Answer 4

1) Depletion of resources
2) Global warming (kg CO2 equivalent)
3) Ozone depletion (Kg CFC-11 equivalent/kg emission)
4) Human Toxicity (1,4 dichlorobenzene equivalents /kg emission)
5) Freshwater/aquatic/marine/terrestrial ecotoxicity (1,4 dichlorobenzene equivalents /kg emission)
6) Photo-oxidant formation (smog) (kg ethylene equivalents/kg emission)
7) Acidification (kg SO2 equivalents/kg emission)
8) Eutrophication (kg PO4 equivalents/kg emission)

Question 5

What are some benefits and impacts associated to using PLA for bioplastics?

Answer 5

Benefits
+ Renewable source
+ Biodegradable
+ Lower Carbon footprint
Impacts
- Agricultural impact > land use, more pesticides
- Energy use from non-renewable sources
- Waste management, PLA needs specific conditions to biodegrade
- Competition with food supply, the land used to grow corn used to be for food raising local food prices

Question 6

What are the 2 largest sources for energy to transport and supply corn for PLA production

Answer 6

Natural gas and electricity

Question 7

PLA can have a wide range of properties, what are some potential reasons for this?

Answer 7

1) Molecular weight of polymer chains, longer polymer chains = stronger and tougher
2) Crystallinity, higher crystallinity higher stiffness, strength and heat resistance
3) Presents of plasticisers

Question 8

How does molecular weight affect polymer properties?

Answer 8

• polymer chains with higher molecular result in higher tensile strength and toughness
• Low MW results in reduced strength and brittleness

Question 9

How does crystallinity ratio and processing conditions affect polymer properties

Answer 9

The processing conditions determine crystallinity, eg rapid cooling results in more amorphous regions
Higher crystallinity materials are more strong, stiff and heat resistant but less flexible

Question 10

How can aging and environmental conditions affect a polymer?

Answer 10

hydrolytic degradation under high heats and temps can weaken a material
Mechanical stresses can cause micro cracking which can also cause fatigue

Question 11

Why are crystalline structures stiffer?

Answer 11

They are more ordered and tightly packed, less room movement of the chains

Question 12

Are amorphous structures more or less transparent?

Answer 12

Amorphous structures are more transparent, due to the lack of light scattering
- Diamonds block loads of light and are perfect crystals

Question 13

What are some common End of Life options?

Answer 13

landfills, compost heaps, bacterial digestion, incineration and recycling

Question 14

What is meant by biodegradable?

Answer 14

It can be broken down by natural biological processes

Question 15

How is PLA turned into compost?

Answer 15

This requires 3 steps
1) Taking the left over PLA and separating it
2) Grinding it down
3) Composting it

Question 16

How is PLA mechanically recycled for reuse?

Answer 16

1) Separating the scrap PLA
2) Grinding it down
3) washing and drying to remove impurities
4) Extruding the PLA into a die to form a shape
5) Cooling the molten PLA
6) Optional grinding or sieving by size to form uniform pellets

Question 17

How can PLA be chemically recycled?

Answer 17

There are 2 major steps
1) Hydrolysis of PLA
2) Polymerisation of the concentrate PLA solution

It still contains, separating, grinding, washing and drying, then hydrolysing which outputs impurities and lactic acid

Question 18

List a few pros of biopolymers

Answer 18

1) made from Renewable resources conserving fossil fuels
2) Lower CO2 emissions to produce
3) Can come from domestic sources, so less dependence on foreign oil
4) No toxicity or health hazards
5) In countries with plenty of land it offers another source of finance and income

Question 19

List a few cons of biopolymers

Answer 19

1) production of them can compete with food production, this can raise food costs
2) Required intensified farming, processing, deforestation and other actions that increase CO2 emissions
3) Large scale crop monocultures threaten biodiversity and take up land that could be used for other purposes
4) Degrading biopolymer particles are foods and breeding grounds for potentially dangerous bacteria

Question 20

What are a few ethical considerations to be aware of when thinking about biopolymer production? (3)

Answer 20

1) There is a finite amount of land that crops can be grown > there could be better uses for the land
2) Agriculture is already the largest source of greenhouse gasses > leads to reduced biodiversity and deforestation
3) Available freshwater has been collateral damage > Irrigation has drawn so much water away from natural rivers that they have dried up
4) Chemicals used for crop yield > estimated 50% of them run off into local waters impacting the quality

Question 21

What potential avenues are there to reduce the environmental impact or our demand for biopolymers?

Answer 21

1) More conservative light weight packaging
2) Employing green chemistry principles, optimising manufacturing to reduce energy consumption and use less harmful materials
3) Develop biopolymers from algae and microbial fermentation which use up less land than crops
4) Promote recycling