Note: This is the third article of a three-part series covering bioplastics (1) trends, (2) material/process advances and (3) applications.

The bioplastics market based on "renewable carbon" is expanding from single-use compostables to durable applications with greater performance demands. The demand for renewable materials in durables is accelerating R&D to meet higher property requirements. Bio-based raw materials will shift to nonfood sources. New technologies will reduce manufacturing costs, and bring new bio-based products to market.

Let's take a look at examples of these new renewable content routes to application development.

Let's start with Wheylayer sustainable barrier packaging film. Approximately 50 million tons per year of whey is produced in Europe as a byproduct of cheese production, with almost 40 percent discarded. Wheylayer 2 is a followup project to the EU-funded Wheylayer 1 project, which successfully developed a whey protein coating for plastic films to replace currently used oxygen-barrier layers in packaging.

Originally formed in 2008 and concluded in 2012, Wheylayer 1 is now being successfully continued under the name Wheylayer 2 with eight of the original partners and two new ones from five different countries. Wheylayer 2 will focus on scaling Wheylayer 1 results to industrialize/commercialize the new material.

A significant problem for the food industry is the oxidation of fats, oils and other food components, which is responsible for producing off-flavors, off-colors and nutrient loss. So protection against oxygen is an important requirement of food packaging.

While polyolefin films such as polyethylene (PE) and polypropylene (PP) provide excellent moisture barriers, they do not provide an adequate oxygen barrier. Multilayer structures are therefore used with polyolefin films coated or laminated with permeation-resistant ethylene vinyl alcohol (EVOH) or polyvinylidene chloride (PVDC) polymers.

The result is a relatively expensive packaging film with excellent barrier properties that is almost impossible to recycle efficiently, due to the difficulties in separating the different layers. The Wheylayer project targeted precisely this aspect.

WheyLayer Wheylayer barrier film layer construction (top left), film (top right) and competitive oxygen/water barrier performance (bottom).

The Wheylayer coating achieves superior oxygen and humidity barrier properties versus most other bioplastics, approaching those of synthetic plastics such as EVOH. Oxygen transmission rates (OTR) of <2cm3/m2 d bar (d is over one day in transmission rates) and water vapor transmission rates (WVTR) of <20g/m2 d bar for a whey layer thickness of 100 microns have been achieved.

The coating on plastic film also has acceptable mechanical integrity. Unlike EVOH multilayer film, which is coextruded, Wheylayer uses lacquering and drying in a reel-to-reel manufacturing process.

During recycling, the whey coating is easily removed by means of enzymatic washing. Washing is already a part of regular recycling operations where recyclers use a wash solution containing detergents to remove grease and dirt from the waste plastic. Studies have shown that it is possible to completely dissolve the barrier coating from the substrate, without leaving any residues. Commercial applications of the whey protein barrier coating are in the European packaging market place.

Next, 100 percent bio-based polyethylene terephthalate (PET) developments are set to accelerate. Around 50 million tonnes per year of PET are produced for conversion into films/bottles for packaging, fibers for nonwovens/textiles and resins for automotive applications. PET is typically made from 15-30 percent monoethylene glycol (MEG) and 70-85 percent terephthalic acid (PTA).

Coca-Cola, Ford Motor Co., Heinz, Nike and Procter & Gamble have formed the Plant PET Technology Collaborative (PTC), a strategic working group focused on accelerating development/use of 100 percent plant-based PET materials and fiber in their products. All five member companies use PET, a durable, lightweight plastic in a variety of products and materials including plastic bottles, apparel, footwear and automotive fabric/carpet.

PlantBottle Coca-Cola PlantBottle manufacturing process.

The PTC collaborative is building upon the success of Coke's PlantBottle packaging technology. At this time only the MEG segment is derived from renewable materials. In this case, that means Brazilian sugar cane/molasses ethanol, which is sent to India for conversion into ethylene and then Indonesia for polymerization into PET.

Bio-based MEG, available from several sources, accounts for approximately 30 percent of Coke's bio-based PET. The bio-PET material has the same properties/functions as traditional PET, and can be recycled just like traditional PET.

Coke introduced Plantbottle to reduce its dependence on nonrenewable petroleum while also lowering potential carbon dioxide emissions that result from their PET plastic bottles. The PTC collaborative was formed to leverage R&D efforts of the founding companies to achieve commercial solutions for PET plastic made entirely from bio-based material.

Finally, let's review bio-based isoprene rubber. Isoprene is a versatile petrochemical building block mainly used in synthetic rubber and thermoplastic elastomer production. About 900,000 tons of isoprene are currently used globally, roughly 60 percent for tires, 30 percent for adhesives and 10 percent for medical or personal care products.

Several companies are pursuing development of bio-based isoprene, including three chemical company/tire manufacturer partnerships interested in bioisoprene for use in bio-based synthetic rubber development. Their goal is to develop low-cost, biomass-based bio-isoprene that will provide a strategic raw material for synthetic polyisoprene production, as well as stabilize costs, decrease dependence on fossil oils and natural rubber sourcing, and improve the environmental footprint of the tire business.

Goodyear Tire & Rubber Company and originally DuPont Industrial Biosciences — which in 2011 was acquired by Danisco and its Genencor division that spearheaded R&D around the bioisoprene product are working together to develop bioisoprene and have demonstrated a prototype tire using the bioisoprene monomer. Goodyear is one of the world's largest users of isoprene for the production of synthetic rubber and elastomers.

Elsewhere, Ajinomoto and Bridgestone will jointly develop isoprene using biomass feedstock. Ajinomoto has already successfully manufactured bioisoprene at a laboratory scale using a fermentation process, and Bridgestone has successfully produced polyisoprene rubber using the material.

Michelin is also working with Amyris Biotechnologies to develop bio-isoprene using Amyris farnesene a 15-carbon isoprenoid as building block. Amyris has begun commercialization of this new, renewable isoprene.

Glyco Biotechnologies and Aemetis are separately also developing bio-based isoprene. Using its bacterial fermentation platform, GlycosBio has built its first commercial facility in southern Malaysia to supply the Southeast Asian region with up to 40,000 tons of bioisoprene annually. Aemetis now owns Zymetis' proprietary aerobic marine organisms, (Saccharophagus degradans 2-40, trademarked as the Z-microbe) that will enable the company to produce bio-isoprene and other bio-chemicals.

Aemetis Bio-based isoprene Z-microbe production route.

Other companies working on biobased chemical feedstock for synthetic rubbers include:

  • Genomatica — bio-based butadiene
  • Global Bioenergies — bio-based butadiene in collaboration with Synthos; Bio-based isobutene (which canbe converted to isoprene) in collaboration with LanzaTech.
  • Elevance — bio-based rubber compounds in collaboration with Hutchinson Worldwide.
  • Gevo — bio-based rubber compounds in collaboration with Lanxess.