The past few years have witnessed the emergence of bio-feedstocks and bio-based commodity polymers production. Rising oil prices, rising consumer consciousness and improving economics of production have heralded commercialization of bioplastics. This sector continues to face many challenges and will continue to be impacted by factors such as quality, economic viability, and scale of operation. A snapshot of some of the better-known products will provide insight into common challenges faced by these processes and products, as reported by ICIS.
Polyethylene Terephthalate (PET): PET faces some of the strongest public pressure to be 100% sourced from renewable feedstocks. This pressure has been augmented by the aggressive plans of beverage giants Coca-Cola and Pepsi. Currently under wide commercial use is PET made with 30% MEG, in part sourced from sugarcane-derived ethylene. Both companies are searching for a route to green purified terephthalic acid (PTA) for the other 70%. In December 2011, Coca-Cola entered into two agreements - 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. Japan's Toyota Motor is investigating using 30% green PET for up to 80% of its car interiors. 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: PLA is already used in manufacturing yogurt cups and other clear food containers, as a green alternative to polymers such as polystyrene (PS). 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). 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 properties. PLA also has poor barrier properties, which limits its areas of application. 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. With larger plants such as NatureWorks' 140,000 tpa Nebraska plant (operating) and Purac's anticipated 750,000 tpa lactide capacity in Thailand, pricing should further approach that of similar petroleum-based plastics.
PVC In Early Stages : Solvay originally announced the production of 60,000 tpa 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.
Sugar-Based Polycarbonate (PC): 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. 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.
Polybutylene succinate (PBS): 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.
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.