Bioplastics: PLA, PHA, bio-PE and starch blends: Key terms, quiz and sources

Understanding Chemicals / Module 14: Bioplastics: PLA, PHA, bio-PE and starch blends Wrap-up

Bioplastics: PLA, PHA, bio-PE and starch blends: review

Key terms

Bio-based plastic: A plastic derived from biomass, whatever happens to it at end of life.
Biodegradable: Broken down by micro-organisms to CO2 or methane, water and mineral salts in a named environment within a stated time.
Compostable: Biodegradable under managed composting conditions to a standard such as EN 13432 or ASTM D6400, at 58 C for industrial certification.
Drop-in polymer: A bio-based polymer chemically identical to a fossil one, such as bio-PE or bio-PET, so it uses existing machines and recycling.
Bio-based carbon content: The share of a product's carbon that is recent plant carbon, measured from carbon-14 by ASTM D6866.
Glass transition temperature (Tg): The temperature below which a polymer's amorphous regions are glassy and brittle and above which they are rubbery.
Crystallinity: The fraction of a polymer in which chains pack in ordered regions, raising stiffness, strength and heat resistance.
Lactide: The cyclic dimer of lactic acid, purified and ring-opened to make high-molecular-weight PLA.
Ring-opening polymerisation: Chain building by opening ring-shaped monomers such as lactide, which releases no water and so reaches long chains quickly.
Optical purity: The share of one mirror-image form (L or D) in lactic acid or PLA; below about 78% PLA cannot crystallise.
Polyhydroxyalkanoates (PHA): Polyesters made and stored inside bacterial cells as an energy reserve; PHB is the simplest.
Fed-batch fermentation: A batch fermentation in which substrate is added as the culture consumes it, used for PHA and many other products.
Thermoplastic starch (TPS): Starch whose granules and crystals have been destroyed by heat, shear and plasticiser so it flows like a plastic melt.
Material versus process carbon footprint: Carbon locked in the polymer itself, as opposed to emissions from making, using and disposing of it.
Cradle-to-gate: A life-cycle boundary from raw material extraction to the factory gate, excluding use and end of life.
Oxo-degradable plastic: A conventional plastic with additives that make it fragment by oxidation without full biodegradation; banned in the EU from 2021.
Capacity utilisation: Actual production divided by nameplate capacity; 72% for bio-based plastics in 2025.

Try it in the table

Open the 'Lactic acid and PLA' tile and compare its producers and feedstocks with the Cargill Dow route in Part 2. Which steps would differ for a plant fed by Indian cane sugar instead of corn dextrose?
On the 'Bio-based polyethylene and MEG' tile, compare its price with 'High-density polyethylene' and check whether the gap still sits near the 30-50% markup Toyota accepted.
In the 'PHA bioplastics' tile, list today's producers and compare their plant sizes with the 55,000 t Metabolix and ADM plant written off around 2012.
Use the 'Bioethanol' tile to estimate what share of a country's fuel-ethanol output one 200,000 t bio-PE plant would absorb at 1.7 t of ethanol per tonne of ethylene.
Compare 'Starch and cellulose derivatives' with 'Polystyrene and EPS': which packaging uses could starch-based loose-fill realistically displace?
On 'PET resin', look at recycling rates and ask whether a bio-PET bottle or a PLA bottle would fit better into a collection system like India's.

Final quiz

A firm sells '100% plant-based PE bags that disappear in nature'. Which part of the claim can be true?

Bio-PE can be over 96% bio-based, but it is ordinary polyethylene and persists. Oxo additives only fragment it, and the EU banned oxo-degradables in 2021.

Why does commercial PLA production go through lactide rather than polymerising lactic acid directly?

Removing the final traces of water limits direct condensation. Ring-opening of purified lactide, catalysed by tin octoate, builds long chains in hours with no water released.

A 10,000 t a year PHB plant runs 330 days at 1.89 kg PHB per cubic metre per hour. Roughly what working fermenter volume does it need?

10,000,000 kg / 7,920 h = 1,263 kg/h; divided by 1.89 kg per cubic metre per hour gives about 670 cubic metres, before allowing for turnaround. With fermenters limited to under 500 cubic metres, that means several vessels.

Why do starch-based plastics score well on resource efficiency?

Using the natural polymer directly avoids fermentation losses. Novamont's authors give a yield close to 100% against generally less than 45% for fermentation-derived monomers.

Narayan's carbon comparison of PE and PLA shows that:

PLA's process emissions are about 385 kg CO2 per 100 kg against about 200 for PE, but PE's carbon is fossil and adds 314 kg at end of life, while PLA's plant carbon nets to zero.

According to Rosenboom's table, which material degrades in ocean water within months?

P3HB degrades in sea water in 1-6 months. PLA takes more than 1.5 years, PBAT more than a year, and bio-PE does not biodegrade.

What did EUBP report about Europe's bio-based plastics capacity in 2025?

The EU27+3 had 0.33 million tonnes, about 14% of global capacity, with PLA at 0.0%. Growth to 0.80 million tonnes by 2030 comes mainly from bio-PP, bio-PE and PHA.

A start-up plans compostable carrier bags for a city with no separate food-waste collection. What is the main risk?

Compostability pays off only if the bag reaches a composter or digester. In landfill, biodegradable plastic can rot to methane, and in litter many compostable materials degrade slowly.

Sources for this module

Kabasci, S. (ed.) (2014). Bio-Based Plastics: Materials and Applications. Wiley (Wiley Series in Renewable Resources). · Ch 1 (sections 1.1-1.3); Ch 2 Starch (2.1-2.6); Ch 7 Polyhydroxyalkanoates (7.1-7.9); Ch 8 Poly(Lactic Acid) (8.1-8.5, 8.7, 8.8.2, 8.10, 8.12-8.15); Ch 11 Polyolefin-Based Plastics (11.1-11.10); Ch 13 Renewable Raw Materials (13.2-13.8); Ch 14 The Promise of Bioplastics (14.1-14.6)
Rosenboom, J.-G., Langer, R. and Traverso, G. (2022). Bioplastics for a circular economy. Nature Reviews Materials 7, February 2022, from p. 117. · pdf pp. 1-16 (journal pp. 117-132), including Box 1, Table 1, Box 2
European Bioplastics and nova-Institute (2025). Bioplastics Market Development Update 2025 (Market Data 2025), December 2025. · pdf pp. 1-3
Kamm, B., Gruber, P. R. and Kamm, M. (eds.) (2006). Biorefineries: Industrial Processes and Products. Wiley-VCH, 2 vols. Vol 1 Ch 10, Rossell et al., Sugar-based Biorefinery: PHB, sugar and ethanol; Vol 2 Ch 14, Gruber, Henton and Starr, Polylactic Acid from Renewable Resources. · Vol 1 pdf pp. 237-252 (book pp. 209-224); Vol 2 pdf pp. 834-855 (book pp. 381-402)
Wittcoff, H. A., Reuben, B. G. and Plotkin, J. S. (2004). Industrial Organic Chemicals, 2nd ed. Wiley. Ch 3 and Ch 15 How Polymers Are Made. · pdf pp. 162-163, 495-496, 538-545
Kent, J. A. (ed.) (2012). Handbook of Industrial Chemistry and Biotechnology, 12th ed. Springer. Ch 10 Synthetic Organic Chemicals; Ch 15 Synthetic Resins and Plastics. · pdf pp. 322, 328, 596-605
IEA Bioenergy Task 42 (2012). Bio-based Chemicals: Value Added Products from Biorefineries. · pdf p. 18
IEA (2018). The Future of Petrochemicals: Towards more sustainable plastics and fertilisers. OECD/IEA. · pdf p. 44