Alternatives to Plastics

Approaches for production of biodegradable plastics

  1. Direct use of renewable plant material (starch, cellulose, fiber, lignin etc)
  2. Genetically engineered microorganisms to produce more ((PHA) polyhydroxyalkonates or lactic acid for bioplastic
  3. Genetic engineering of plants (Alfalfa, oilseed rape, corn, sugarcane, potato, canola, soybean, tobacco etc) to directly produce biodegradable plastics such as polyhydroxyalkonates (PHA),
  4. Fermentation of wastes (Oil mill effluents, whey, excess sludge), to produce ((PHA) polyhydroxyalkonates or lactic acid (Monomer for polylactic acid) for biodegradable plastics
  5. Blends
  6. Microbial fermentations of renewable plant material (like starch, cellulose, oil) to produce materials ((PHA) polyhydroxyalkonates or lactic acid (Monomer for polylactic acid) for plastic

Biodegradable Polymers for Bioplastics

(I)        Natural Polymers

  1. Starch-based Polymers – Plant based
  2. Polylactides (PLA) – Lactic acid by fermentation
  3. Polyhydroxyalkonates (Polyhydroxybutyrate) (PHB) – Microbial source
  4. Cellulose: Cellulose esters, cellulose ethers, cellophane (cellulose pulp from trees or cotton may be used to produce cellophane), cellulose diacetate
  5. A protein in corn gluten meal ‘zein’
  6. Lignin based biopolymers
  7. Soyabean protein and oil
  8. Protein-based polymers that come from bacteria
  9. Proteins – Mainly from animal source – Collagen, casein, albumin, silk, feather, keratin
  10. Agricultural lignocellulosic fiber polymers, Agricultural lignocellulosic residues – Cotton, Jute, Sisal, Flax, Hibiscus, Pinapple leaves, Banana, Date Palm, Coir, Rice, Wheat, Cereal, Sugarcane bagasse
  11. Naturally occurring polymerizable monomers, Agricultural monomers – sugars, castor oil, other vegetable oils, cashew nut shell liquid, natural rubber, shellac, terpenes
  12. Sugarcane plants

  (II)        Synthetic Polymers

Aliphatic polyesters, Poly (ether-esters), Poly (amide-esters), Poly (vinyl-esters),

Poly (ester-urathanes), Poly (aspartic acid), Poly (phosphazenes), Poly (vinyl alcohol), Poly (e) caprolactone (PCL), Polybutylene adipate

i.        Polycaprolactone

ii.        Polyethylene compounded with starch or modified starch

iii.        Polyethylene compounded with photooxidative additives

Blends of Natural and Synthetic materials

i.        Wheat starch with synthetic polymers

ii.        Ground barley grain with recycled plastic

Polymer containing starch and PCL (polycaprolactone)

While biodegradable plastics are not yet widespread – they account for less than 1% of all plastic produced – their use is growing steadily.

Benefits of Biopolymers
  • Can replace many harmful conventional plastics
  • Can be fully biodegradable (capable of being utilized by living matter)
  • Can be made from a variety of renewable resources
  • Can be composted locally into a soil amendment
  • Can contribute to healthier rural economies

Factors affecting Biopolymer Market

  1. Soaring oil prices,
  2. Depleting oil reserves,
  3. Worldwide interest in renewable resources,
  4. Growing concern regarding greenhouse gas emissions and
  5. A new emphasis on waste management
  6. Total Life Cycle Assessment,
  7. Legislative incentives (particularly in European Union),
  8. Suitability of material properties,
  9. Technical feasibility of processing options, and
  10. Commercial viability of production and processing.
  11. Consumer Acceptance
  12. Range of Applications

The use of legislative instruments is a significant driver influencing the adoption of biopolymers in place of the petroleum based polymers. In Europe and Japan, the automotive and packaging sectors are most affected by ratified legislation. The Packaging and Packaging Waste Directive 94/62/EC and the End of Life Vehicle Directive 2000/53/EC are two examples of such legislative drivers. Additionally, in the U.S. Section 9002 of the Farm Security and Rural Investment Act of 2002 confers federal purchasing preference to biopolymer based products.

Biodegradable Plastics’ Promises

  1. Market Demand
  2. Material Variety
  3. Use of Renewable Resources
  4. Sustainable Development
  5. Solution to Solid Waste mgt.
  6. Biodegradable, Compostable
  7. Range of Applications

Biodegradable Plastics Challenges

  1. Cost of Production – High
  2. Scale of Production – Small
  3. Properties Limitations
  4. Processing Limitations
  5. Technology only Two Decades Old
  6. Public Awareness Insufficient
  7. Standardization still in process
  8. Competition with Most Versatile and Most Popular Material Option
  9. Not Totally Free from Fossil Fuel Use
  10. More Energy Required for Production *
  11. More Green-House Gases on Disposal

* 1 Kg PE – 2.2 Kg Fossil Fuel Required

* 1 Kg PHA – 2.6 Kg Fossil Fuel Required

Issues Discussed in favor and against Bioplastics

  1. Environmental Costs must be attached to non-degradable plastics
  2. Exemption from taxes for biodegradable plastics
  3. Fair competition
  4. Life-cycle analysis – From cradle to graveyard
  5. Energy balance – Carbon balance
  6. Only convenience not agreed

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