Recently we have seen two new developments in manufacturing 100% biobased PET.
It should be well known to my regular readers that I strongly object so-called biodegradable plastics, and even to a certain extend the so-acclaimed bio-plastics. The reason is simple. Biodegradability is obtained either from additives in fossil plastics (which have in general a very negative effect on the recycling stream) or from bio-based plastics, like PLA, Meril etc, which are manufactured from corn starch occupying huge areas of arable land which should be used solely for food production and to complete their negativity most bio-based plastics frustrate the recycling stream. Let me clarify this. In principal I am not against bio-based plastics in general, I object the renewable resources using arable land.
Note 1: PLA, Mirel and others form a family of bio-based plastic materials that have physical properties comparable to petroleum-based resins, yet are bio-based and biodegradable in natural soil and water environments, in home composting systems, and in industrial composting facilities where such facilities are available. The rate and extent of PLA and Mirel’s biodegradability will depend on the size and shape of the articles made from it. However, like nearly all bio-based plastics and organic matter, PLA and Mirel, are not designed to biodegrade in conventional landfills. To be more blunt: Nothing biodegrades in landfills. Any claim as such is greenwashing.
Note 2: The widely, in websites and promotional flyers, used term “bio-plastics” should be avoided due to its ambiguity. It is sometimes used for plastics that are bio-based and sometimes for plastics that are biodegradable (including those that are made from fossil instead of renewable resources). The correct term to be used is: bio-based plastics.
Bio-based plastics are defined as man-made or man-processed organic macromolecules derived from biological resources and used for plastic and fibre applications (without paper and board).
It is troublesome to see that many a consumer goods company is trying to satisfy the “general consumer desire” to replace “traditional plastics” only for the purpose to greenwash its imago, misusing the all-too-popular image that fossil plastics are somehow negative, and that anything “bio” is somehow positive. Reality is a bit different.
If so, my readers will ask, why do you still write this article about renewable bio-based PET. Well PET, as long as no biodegradable additive is added to the mix, is a bit different. I refer to Gordon Bockner, who wrote in the May 6, 2011 issue of Plastics News:
“The chemistry of the PET molecule, which is the primary determinant of whether PET can be successfully recycled back into PET bottles in a [business-to-business] recycling system, is exactly the same whether its components are sourced from biomass or petroleum. Bio-PET is as recyclable as petroleum-based PET, and/or with petroleum-based PET. The two are interchangeable in the recycle stream.
Whether, on the other hand, it is environmentally or economically sound to source all or some of the components of the PET molecule from biomass is an interesting (and arguably unresolved) question. The answer, however, has nothing to do with the recyclability of the resulting bio-PET molecule in the existing petro-PET recycle stream. It is PET and it is recyclable.” (end quote)
And as PET is PET, it is very interesting to see what new developments in renewability of this material have seen the market recently. Don’t forget that around 50 million tons of PET are produced annually for conversion into films and bottles for packaging and some other products. Logically there is strong market demand for fully renewable, non-petroleum derived PET, to meet the growing consumer demand for environmentally friendly products.
So that was the petro-story, let’s have a look at the bio-based story. We all have read about the recent announcements, by H.J. Heinz Co. to use Coca-Cola’s 30% plant-based PET PlantBottle for packaging its ketchup, and then by PepsiCo announcing the existence of a 100% plant-based PET bottle in the laboratory and shortly thereafter Coca-Cola itself announcing the 100% PlantBottle for Dasani.
Note: Don’t bring Procter&Gamble’s recently introduced plant-based plastic bottles for Pantene in the mix, as they are made from sugar-cane-based PE, the so-called Green PE from Brazilian company Braskem.
There are two new developments in this field worth a closer look, both were introduced last month at the “BioPlastek 2011 Forum”, held at The Waldorf-Astoria in New York. But before we have a look at these two developments, let’s see what is PET, as everybody is talking about PET and few really know what it is. A short story:
PET (Polyethylene Terephtalate) is a tough, temperature resistant polymer. The leading use of PET resin is in bottle production.
PET resin is manufactured by the etherification of PTA (Purified Terephthalic Acid) with ethylene glycol and loss of water, or by the trans-etherification of DMT (Dimethyl Terephthalate) with ethylene glycol and loss of methanol. Both reactions occur at 100 to 150°C in the presence of a catalyst. Bis (2-hydroxyethyl) terephthalate is produced as an intermediate. This intermediate then undergoes poly-condensation under vacuum at 10 to 20°C above the melting point of PET (246°C). Ethylene glycol is distilled over, and PET resin with an I.V. (intrinsic viscosity) of 0.60 to 0.65 is produced. The resulting resin is cooled and pelletized. The final step in PET resin manufacture is a solid state polymerization process. This step raises the temperature of the solid pellets to just below the melting point in the presence of a driving force to further the polymerization. Solid stating increases the final I.V. from 0.72 to 1.04. It also produces a polymer with low acetaldehyde content.
Para-xylene is a direct precursor to terephthalic acid (PTA) production, which accounts for 70% of polyethylene terephthalate’s (PET) monomer component. The other 30% is composed of mono-ethylene glycol (MEG), where renewable-based bio-alternatives are already available. The challenging issue is to replace the PTA component by a bio-based version to cost-effectively achieve 100% renewable bio-based PET.
As said two companies reached this goal recently.
Gevo employed prototypes of commercial operations from the petrochemical and refining industries to make para-xylene from isobutanol. This renewable para-xylene was sent to Toray for conversion into bio-based PET articles. Toray employed its existing technology and new technology jointly developed with Gevo and used Gevo’s para-xylene and commercially available renewable mono ethylene glycol (MEG) to produce fully renewable PET (all of the carbon in this PET is renewable).
Gevo’s commercialization efforts are focused on isobutanol, a naturally occurring four carbon alcohol. Isobutanol is an important platform chemical with broad applications in large chemicals and fuels markets and a “drop-in” product that should allow customers to replace petroleum-derived raw materials with isobutanol-derived raw materials without modification to their equipment or production processes.
Gevo’s isobutanol will be chemically equivalent to those produced from petroleum-based raw materials, except they will be produced via fermentation from renewable sources.
Gevo is currently working with partners to optimize the process technology needed to produce para-xylene from isobutanol at commercial-scale and competitive economics.
I know, I know, Gevo’s process is based on corn. But I give it the benefit of the doubt, as Gevo states that it sees a day when it no longer relies on corn. It has licensed a yeast developed by Cargill that ferments cellulosic sugars in non-food plants and agricultural residue. Minnetonka-based Cargill’s scientists are tweaking the yeast’s properties to produce isobutanol using Gevo biotechnology.
That system will be tested next year at Gevo’s smaller demonstration isobutanol plant in St. Joseph, Mo., using such feedstocks as corncobs, wood chips or switch grass.
At the same forum in New York another company, Virent, introduced its development of …….. yes ….. para-xylene (PX) from 100% renewable plant sugars, the missing link in the manufacturing of 100% bio-based PET.
Virent’s Paraxylene, which has been trademarked as BioFormPX, can be used in bottles, and packaging in general. In contrast to Gevo, which uses fermentation, Virent’s BioFormPX is made through a patented, catalytic process which converts plant-based sugars into PX molecules identical to those made from petroleum. In essence, the bio-based PX fills in the “missing piece” to make a 100% bio-based PET bottle.
The BioForming technology converts water soluble sugars into fuels and can economically utilize many types of carbohydrates from cellulosic and biomass-derived feedstocks.
The ability to process polysaccharides (complex sugars) and mixed sugar streams distinguishes the BioForming process from fermentation technologies. Fermentation microbes are adept at converting single sugar monosaccharides to specific product molecules. The BioForming process works on a broader composition of sugars making desirable, hydrocarbon blends.
Since Virent’s process is feedstock flexible, it enables the use of the lowest cost biomass sources available in each region. Feedstock options include traditional food crops as well as non-food sources such as corn stover, switch grass, wheat straw, woody biomass, sugar cane bagasse, and sugar beet pulp.
As with Gevo, all of Virent’s chemicals are ‘drop in’ replacements that enable full utilization of existing processing and logistics infrastructure without blending limitations. Virent claims that its PX can be blended at any ratio the customer desires, and made from a wide variety of feedstocks.
Virent used US-grown sugarbeets as the feedstock in this demonstration. A similar process has been demonstrated at smaller scale with a variety of feedstocks.