The emergence of bio-feedstocks and bio-based commodity polymers production, in tandem with increasing oil prices, rising consumer consciousness and improving economics, has ushered in a new and exciting era of bioplastics commercialization. However, factors such as economic viability, product quality and scale of operation will still play important roles in determining a bioplastic's place on the commercialization spectrum.
A snapshot of some of the better-known products will provide insight into common challenges faced by these processes and products.
Of the bio-commodity polymers profiled, bio-based polyethylene (PE) is in the most advanced stage of commercialization. Brazil-based Braskem is the clear leader in the field, utilizing local sugarcane-derived ethanol/ethylene as feedstock.
In September 2010, Braskem achieved commercial production of bio-based high density polyethylene (HDPE) at its plant in Triunfo, Brazil, which has a capacity of 200,000 tonnes/year. The green PE marketed by Braskem provides the same performance and characteristics as petroleum-based PE.
Currently such green PE products command a price premium of around 15-20%, which is feasible for selected target markets and allows for the higher cost of production when compared to petrochemical-based plastics.
However, as more commercial bio-based PE producers enter the market and as the technology further develops, this price premium is expected to drop.
US-based Dow Chemical and Japan's Mitsui completed a 50:50 joint venture for a sugarcane-to-PE project in Brazil. The project will be the world's largest biopolymers investment.
The plant, with capacity of 350,000 tonnes/year, will produce DOWLEX PE resins and is expected to come on line in 2015. The facility will supply the flexible packaging, hygiene and medical markets.
The product is expected to be cost-competitive with petrochemical-derived PE as the venture will own and operate the entire value chain, from growing sugarcane to producing the biopolymer.
Braskem is currently building a 30,000-50,000 tonne/year bio-based polypropylene (PP) production plant, expected to come on line in 2013, based on ethanol (propylene via ethylene dimerization followed by metathesis).
The company has been researching more efficient biochemical routes through partnerships, including a link with Denmark-based enzyme firm Novozymes. Germany-based chemical company LANXESS stated that it will have a direct pipeline to Braskem's green propylene production site for its rubber production.
Green PP options are also being explored by the automotive industry. This includes Japan-based Mazda's Bioplastic Project, which is developing bio-based PP derived from cellulosic biomass, to be used in vehicles by 2013.
PET arguably faces some of the strongest public pressure to be 100% sourced from renewable feedstocks. This pressure has been augmented by the aggressive plans of US-based beverage giants Coca-Cola and Pepsi. Currently, PET made with 30% MEG, in part sourced from sugarcane-derived ethylene, is widely used commercially.
Research has kicked into high gear, with both companies searching for a route to green purified terephthalic acid (PTA) for the other 70%. In December 2011, Coca-Cola entered into two agreements - the first with US-based technology firm Avantium to develop a commercial route for polyethylene furanoate (PEF) YXY technology. PEF is regarded as a different form of PET that has better heat and barrier properties.
The second agreement with Gevo and Virent is aimed at bringing 100% PlantBottle technology to commercial scale through two different bio-based routes to paraxylene (PX), which is a precursor for PTA.
Challenges to 100% green PET are now focused on scaling these technologies to commercial levels. Another US technology firm, Anellotech, also offers bio-based options to PX using biomass.
Unlike several other bioplastics that focus on niche markets, PET has proven versatile in other sectors. Japan's Toyota Motor is investigating using 30% green PET for up to 80% of its car interiors and in January 2011, a Lexus model was introduced using this PET in the trunk lining. However, unlike other bioplastics such as PE and PP, 100% bio-based PET is still somewhat far from commercialization, despite the drive behind research efforts.
PLA FOR SELECT USERS
PLA is chemically prepared from lactic acid, which is produced from the microorganism- catalyzed fermentation of sugar or starch. Several companies claim technology for PLA production: NatureWorks (Ingeo); Thyssenkrup; Purac; and Teijin, with Mazda (BIOFRONT).
PLA is already used in manufacturing yogurt cups (Danone, Stonyfield) and other clear food containers, as a green alternative to polymers such as polystyrene (PS).
Despite such a relatively strong commercial presence and being 100% green, PLA does not have good resistance to heat or impact, meaning that it is frequently blended with petrochemical-based products or requires additives to alter to properties. One example is US-based compounder PolyOne's reSound.
PLA also has poor barrier properties, which limits its areas of application. In terms of economics, PLA is more advanced in competitive pricing than many other bioplastics. Over the past decade, by optimizing process technology, the price has been reduced significantly.
Additionally, with larger plants such as NatureWorks' 140,000 tonne/year Nebraska plant (operating) and Purac's anticipated 750,000 tonne/year lactide capacity in Thailand, pricing should further approach that of similar petroleum-based plastics.
PVC IN EARLY STAGES
The polyvinyl chloride (PVC) industry has been subject to steady decline as a result of claimed environmental drawbacks and use of various plasticizers that carry their own environmental challenges.
Belgium-based Solvay originally announced the production of 60,000 tonnes/year of bio-based ethylene for the production of PVC. It halted its project development largely because of the 2008 economic downturn, but has now resumed development.
Efforts to replace traditional plasticizers are also under study. For example, scientists from several companies have created bio-based plasticizers to replace phthalates, reportedly with no reduction in PVC flexibility or other properties.
Polycarbonate (PC) from isosorbide (derived from sugar) has aroused the interest of several leading companies, to the extent that some of these firms - such as Japan's Mitsubishi and France's Roquette - operate or plan to operate pilot plants for making isosorbide and incorporating it into PC. Production from isosorbide and a diaryl carbonate removes the need to use toxic phosgene and controversial bisphenol A (BPA) in the process.
Isosorbide-based PC is quite far from commercialization, as the economics and quality are still problematic. The process is more expensive than the conventional melt or interfacial processes, and most of the isosorbide polycarbonates are oily solids with low melting points and poor heat resistance unless specific reactants are used under very stringent conditions.
Moreover, most of the firms involved in research - such as Saudi Arabia-based SABIC and Japan-based companies Mitsui Chemicals, Mitsubishi Chemical and Teijin - still use BPA or another glycol in the production of commercial polycarbonate, indicating a quality dependence on BPA.
PHAS FACE CHALLENGE
Polyhydroxyalkanoates (PHAs) mostly refer to PHB (poly (3-hydroxybutyrate)) and its copolymer PHBV (poly (3-hydroxybutyrate-co-3-hydroxyvalerate)). These are polyoxoesters that are produced by bacteria through sugar or lipids fermentation. They have superb barrier properties and, as they are biodegradable, are attractive for biomedical uses.
PHAs are sold under the name Mirel by US-based bioplastics firm Metabolix. However, its production joint venture with US agribusiness ADM, featuring a 50,000 tonne/year plant in Clinton, Iowa, US, was terminated in February. Metabolix is exploring options for more limited production of 10,000 tonnes/year.
Derating capacity highlights one of the problems with bringing PHA to commercialization. Sales volumes are too low to realize economies of scale, even with optimized technology. As a result, this bioplastic is priced at a premium of roughly $0.75/lb to comparable polymers.
Metabolix was recently awarded two new patents for different routes to PHAs, which they believe will provide cost advantages through recovery of downstream products such as acrylic acid.
There are other disadvantages to be dealt with before commercialization, including brittleness, a narrow processing window, a slow crystallization rate and sensitivity to thermal degradation. Similar to PLA, shortcomings are overcome through blending with other additives and polymers.
PBS LIFTED BY BIO-SUCCINIC
Polybutylene succinate (PBS) is made from succinic acid and 1,4-butanediol (BDO). Bio-succinic acid technology is owned by several US firms, including BioAmber, Reverdia and Myriant, as well as Purac, based in the Netherlands. Most of these producers are expected to begin commercial production of bio-succinic acid in the next two years, several with joint venture partners, to produce PBS.
One of the key issues with PBS is its marginal performance when used by itself. To address this, current versions of bio-PBS are usually modified by mixing with other polymers.
An example is BioAmber's soon-to-be-released modified PBS (mPBS), which touts better properties such as higher heat distortion, greater cost and lower strength. Such a modified version is able to compete in the food packaging and utensils industry with petroleum-based PBS.
With consumer consciousness and sustainability becoming a new market driver, the push to bring bioplastics to commercialization has become even more pronounced.
Products such as green PE and PET have identical properties to their petrochemical counterparts, and this has accelerated their commercialization. Conversely, new bioplastics such as PLAs continue to face challenges as producers struggle to develop markets, improve properties and performance, and reduce production cost.
Despite having a long way to go on the road to commercialization, bioplastics promise to become a much more significant source of the world's plastics in coming years.
Ria Harracksingh is a senior analyst in Nexant's Energy and Chemicals Consulting group based in White Plains, New York, US. Ria is a recent graduate of Yale University with a Bachelor of Science degree in chemical engineering.