BioCycle May 2006, Vol. 47, No. 5, p. 43
Major companies as well as specialized start-ups are adding to the numbers entering the microbial arena to produce and market compostable plastics. Part I
Diane Greer

GREEN PLASTICS’ sounds like an oxymoron. How can a material manufactured from petrochemicals and resistant to decomposition possibly be green? The answer lies with a new breed of “bioplastics” produced from renewable resources, engineered to look, feel and perform like their petrochemical cousins and then decompose naturally when discarded.
Green plastics are not a new concept. Throughout history, man has employed natural materials to produce plastics. Native Americans fashioned tools from collagen found in animal bones; Henry Ford experimented with soy-based plastics for automotive parts; and cellophane, still used today, is produced from cellulose in wood pulp.
What is new about today’s bioplastics are the processing technologies. Scientists are employing biotechnology and the processing ingenuity of Mother Nature to produce bioplastics from plants such as corn, potatoes and sugar cane and in the cells of bacteria and other living organisms. The resulting bioplastics can be manufactured into products like garbage bags, food containers, cutlery and mulch film.
Interest in bioplastics is moving beyond the Birkenstock crowd. Sam’s Club, a division of Wal-Mart, uses “corntainers” to package fruits, vegetables and herbs. Archer Daniels Midland is teaming with Metabolix to build a manufacturing facility producing bioplastics. Toyota is manufacturing car parts from bioplastic. And Motorola, NEC and Fujitsu are fashioning computer and cell phone cases from bioplastics.
“A confluence of factors – soaring oil prices, worldwide interest in renewable resources, growing concern regarding greenhouse gas emissions and a new emphasis on waste management – has created renewed interest in biopolymers,” said Dr. Donald Rosato, Senior Research Analyst with Frost & Sullivan.
Demand drivers are coalescing with technology advances. Improved bioplastic material properties are narrowing the performance gap with traditional plastics, according to Rosato. As properties improve and prices drop, markets have opened for bioplastics to replace applications formerly associated with conventional plastics such as polyethylene terephthalate (PET), polypropylene and polystyrene.
POLYLACTIC ACID (PLA)
NatureWorks LLC, a subsidiary of Cargill, has refined a technique for producing a natural polyester, called polylactic acid (PLA). At a 140,000-ton/year plant in Blair, Nebraska, dextrose is fed to bacteria in a fermentation process producing lactic acid. Lactic acid, a naturally occurring monomer, forms in the cells of animals and microorganisms as the result of glucose metabolism. Lactic acid is then converted into a lactide in a condensation process, purified and polymerized to produce PLA.
The resulting resin, branded as NatureWorks PLA, replaces PET in selected food packaging and film applications, such as cellophane and garbage bags. Short shelf life bottle applications, including still water, juice and dairy beverages, are also suitable for PLA. Products made from PLA are both biodegradable and compostable.
“For cold food application, PLA is price competitive and performs equal to or better than some of the petroleum-based resins,” says Joe Selzer, Vice President of Marketing and Sales for Wilkinson Industries, a producer of PLA food containers. But the resin is not appropriate for hot applications, explains Selzer. “You can only go up to 105° to 114°F and then you would have some deformation in the product.”
Products packaged in NatureWorks PLA can be found at over 20,000 retail locations including the produce and deli departments at Wild Oats Markets and the produce section at Sam’s Club. Biota is packaging spring water in the first molded bottles made of NatureWorks PLA.
Other companies are also producing PLA. Mitsubishi Plastics is manufacturing plastic film and sheets from PLA. NEC is using a PLA composite with kenaf fibers for laptop computer cases. And Toyota Eco-Plastic combines kenaf with PLA for use in door interiors.
MICROBIAL BIOFACTORIES
In the 1980s, scientists at MIT became intrigued with a peculiar bacteria that could store energy in the form of plastic rather than carbohydrates and lipids, explains Jim Barber, President and CEO of Metabolix. “As they investigated the organism, they discovered ways to harness the machinery of these organisms and improve it to produce plastic materials from renewable resources biologically.”
Based on their findings, Professors Anthony Sinskey and Dr. Oliver Peoples founded Metabolix. Using advanced biotechnology, they genetically enhanced bacteria by incorporating genes from other organisms. Each gene is programmed to carry out a specific step in a multistep process, which produces the building blocks of a natural plastic and assembles those building blocks within the cell, notes Barber.
Their microbial “biofactories” can now code upwards of nine genes from a number of different species to produce polyhydroxyalkanaotes (PHA) during a fermentation process. Sugars and vegetable oils are used in the fermentation feedstock.
Varying the nature and the relative proportion of the building blocks produced and assembled by the microbe can create a variety of PHA copolymers spanning a range of properties from rigid to highly elastic with a range of melting points, explains Barber. “They are suitable for films, fibers, adhesives, coatings, molded goods and a variety of other applications,” points out Rosato. They are also biodegradable and compostable in aerobic and anaerobic conditions and in marine environments.
Rosato believes PHA copolymers have the potential to replace up to 50 percent of the petrochemical based polymers used in packaging. Metabolix recently announced a 50/50 joint venture with Archer Daniels Midland (ADM) to build a 50,000 ton/year PHA manufacturing facility slated for completion in 2008.
Proctor and Gamble Chemicals is also working on commercializing PHA. It has developed Nodax™, composed of several grades of PHA polymers. The company has a licensing agreement with Kaneka, a Japanese company, to produce and commercialize a variety of products and packaging materials.
PLASTICS DERIVED FROM STARCH
The natural material most commonly utilized to create bioplastics is starch. Starch can be derived from agricultural crops including corn, wheat, potatoes, tapioca, rice and soy and is both inexpensive and plentiful.
EarthShell has created a biopolymer made from potato and cornstarch, limestone and water. Vince Truant, Chairman and CEO of EarthShell Corp., likens the manufacturing process to making waffles. The raw materials are mixed into a batter or slurry, poured into a mold and heated. The heated water turns to steam forming and setting the material. The resulting product is then coated with a protective barrier to provide water resistance and added strength. Both the product and the barrier coating are biodegradable in about two months, says Truant.
Although the EarthShell material can be made into a variety of products, the company is concentrating on the $30 billion food service disposable packaging market. Truant sees a growing, worldwide market and projects “environmentally advantaged products” to have a 20 percent market share in five to seven years.
The company has signed a licensing agreement with ReNewable Products, Inc. (RPI) to produce plates and bowls made from the EarthShell composite in a new manufacturing facility in Missouri. Under a similar licensing agreement, EarthShell Hidalgo will produce products for the Mexican market.
The low cost of EarthShell’s primary raw materials offers an economic advantage, allowing the product to compete with products made from traditional petrochemical-based plastic, according to Truant. The products will compete in price and quality in the mid-range of the market. “That is where we will be competitive, where the volume is,” Truant concludes.
BIOPLASTIC SYNTHETIC BLENDS
Europe’s largest producer of bioplastics is Novamont, which produces Mater-Bi. The company runs a 35,000-ton/year plant located in Italy. Mater-Bi is a blended bioplastics composed of starch (corn, wheat or potato) and synthetic polymers. The synthetic polymers are fully biodegradable despite being produced from nonrenewable resources. Different grades of Mater-Bi, for films/sheets, injection molding and foams, contain between 40 to 95 percent starch content with the remainder composed of various synthetic additives and complexing agents. One company making a range of products with Mater-Bi is BioBag.
Mater-Bi composites are just one example of bioplastics blended with synthetic polymers. Blending overcomes shortcomings in some bioplastic properties, such as water resistance, strength and elasticity. In most instances, the synthetic polymers utilized in blends are biodegradable and compostable, permitting the resulting product to pass the Biogradable Products Institute’s (BPI) certification tests (see sidebar).
BASF also produces a blended polymer called Ecovio, a plastic made from 45 percent NatureWorks PLA and 55 percent Ecoflex, BASF’s existing biodegradable plastic derived from fossil resources. The new product was created to meet what the company sees as the growing demand for bioplastics.
Ecovio was developed to achieve new physical properties with biodegradable plastic products by combining two base products. “EcoFlex is a soft material with lower tensile strength and higher elongation,” explains Keith Edwards of BASF Corporation. “PLA is rigid with a higher tensile strength, but no elongation properties. Many applications for plastic fall in between the two points – with some amount of elongation and some amount of tensile strength. For example, disposable cups, plates, knives, forks and drink lids tend to be semi-rigid. EcoVio was born by taking two existing polymers with different characteristics and blending them together with innovative technology.”
Ecovio is being used to make carrier bags (55% Ecoflex/45% PLA), such as grocery store bags, that are 100 percent compostable and 45 percent renewable, says Edwards. Blends of the polymers also can be injection molded (e.g., into plates and cups) and extruded into straws. BASF expects to have the capacity to produce 30 million pounds of EcoFlex in 2006; a new 6,000 ton/year plant is starting up in Germany. The company selected PLA because it is “plentiful, produced in large-scale volumes, has rigid properties and is less expensive than other renewable resins,” adds Edwards.
PLASTICS GROWN IN PLANTS
Metabolix researchers are also working to produce PHA directly in switch grass. “The notion is to apply the same genome engineering directly into the plant,” explains Barber. “So instead of extracting the sugar and then fermenting it, you divert some of that sugar in the plant to create the plastic.”
Eliminating the fermentation step reduces costs. It also improves the economics of energy produced from the residual biomass. Using this method could produce 30 billion tons of natural plastic per year, replacing the equivalent of one million barrels of oil a day and reducing greenhouse gas emissions by 200 million tons/year, according to Barber.
Diane Greer is a freelance writer and researcher based in New York, specializing in sustainable business, green building and alternative energy. She can be reached at dgreer@greerresearch.com.
CERTIFYING BIOPLASTICS COMPOSTABILITY
DETERMINING the “greenness” or sustainability of bioplastics is based on a variety of factors including raw material sources, nonrenewable energy utilization, manufacturing techniques and end of life disposal options. One of the main “green” features touted by the industry is biodegradability and compostability. In the past, the poor performance of early bioplastics, labeled as compostable and/or biodegradable, led to skepticism among commercial composting operations that the bioplastics industry could meet composting standards. To address the problem, the US Composting Council (USCC) teamed with resin manufactures and the scientific community to develop ASTM (American Society for Testing and Materials) specifications.
The resulting specifications, ASTM D6400 and ASTM D6868, require materials to disintegrate and biodegrade under commercial composting conditions and the resulting compost to be able to support plant life, explained Steve Mojo, Executive Director of the Biodegradable Products Institute (BPI). “There are also some heavy metal restrictions.” BPI is a multistakeholder association representing government, industry and academia, which promotes the use, and recycling of biodegradable polymeric materials (via composting). The BPI is open to any materials and products that demonstrate that they meet the requirements in ASTM D6400 or D6868, based on testing in a approved laboratory.
The ASTM definitions that relate to biodegradability and composting are as follows (found at the Cereplast website, www.cereplast.com):
Biodegradable plastic: A degradable plastic in which the degradation results from the action of naturally occurring microorganisms such as bacteria, fungi and algae.
Composting: A managed process that controls the biological decomposition of biodegradable materials into a humus-like substance called compost: The aerobic and mesophilic and thermophilic degradation of organic matter to make compost; the transformation of biologically decomposable materials through a controlled process of bio-oxidation that proceeds through mesophilic and thermophilic phases and results in the production of carbon dioxide, water, minerals and stabilized organic matter (compost or humus).
BPI and the USCC have devised a certification process for products to obtain a BPI Compostable logo. Prior to awarding the logo, BPI verifies the manufacturer passed the ASTM tests in an approved lab, explains Mojo. BPI also looks at company information and employs independent reviewers to examine formulation information. “The program is bringing science to what was previously covered by emotional discussion,” he adds. BPI now lists 22 products certified under the program. Certified resins include Natureworks PLA, Novamont’s Mater-Bi, BASF’s Ecoflex and Cereplast. Manufacturers of compostable bags and films along with food serviceware have also certified their products. The complete list can be found at www.bpiworld.org.