High oil prices are driving US consumers to regard
biodegradable plastics as a potential alternative to
petroleum-based products. But there are many misperceptions
to clear up
Ivan Lerner/New York
TELL MOST people that something is biodegradable, and they will more than likely think that the object in question will break down until there is nothing left, if it is buried in a landfill or compost heap, or left out in the sun or dumped in a body of water.
Biodegradable plastic will indeed break down over a period of time - although there are no requirements for the speed of the decomposition - due to the actions of bacteria or fungi.
Biodegradable plastics are made with 5% cornstarch or vegetable oil, and they cannot be recycled because the starch or oil additive compromises the quality of recycled plastics, according to the US Energy Information Administration.
On the other hand, for a plastic to be considered compostable, it has to satisfy three criteria: biodegradation - it has to break down into carbon dioxide (CO2), water and biomass at the same rate as cellulose disintegration - where the plastic becomes indistinguishable in the compost and nontoxicity.
But compostable plastic bags degrade only in industrial-scale composting plants, not in home compost bins, and they cannot be recycled with ordinary plastic bags, because they will contaminate the waste stream.
So the difference between biodegradable plastics and compostable plastics is that the former gets eaten by bacteria, and the latter needs to be processed? Not quite. Biodegradable bags need to be taken to a facility to be broken down as well.
The American Chemistry Council (ACC) points out that a large-scale composting facility is needed to decompose biodegradable and compostable materials - something most people don't know, the ACC concedes.
Bioplastics, meanwhile, are plastics derived from biomass sources, such as hemp oil, soy bean oil, or cornstarch, rather than from petroleum. Some bioplastics are biodegradable, and some are not.
Additionally, some consumers are cool toward biodegradable plastics, because the idea of wrapping food in something that is made to organically break down is considered unappetizing.
TOMBS OF TRASH
"Bags that are landfilled will not biodegrade, just like other highly biodegradable materials such as paper and whole produce," says Keith Edwards, NAFTA business manager for Styroflex biopolymers at German chemical major BASF.
Biodegradation will not solve any landfill shortage, says the Mississauga, Ontario, Canada-based Environment and Plastics Industry Council (EPIC). According to EPIC, solid waste entering a landfill typically contains only 25-30% moisture, whereas it takes about a 65% moisture level to trigger biodegradation.
Modern landfills essentially entomb trash, denying it air, water or sunlight. This is why newspapers from 20 years ago have been found in excavated trash dumps, and they were still readable.
For the biodegradable polymer market to succeed, it is "extremely critical" that an infrastructure for effective composting be developed, notes analyst Mel Schlechter of the Wellesley, Massachusetts, US-based consultancy BCC Research.
"So the key to the value proposition of converting from traditional to biodegradable grocery bags becomes an organics recycling question and not a bag question," points out Edwards. "If bags can be diverted to organic waste programs, either directly or as a carrier for organic waste, then they will quickly biodegrade like other organics, and be converted into a highly valuable soil."
Biodegradable bags are currently being used as organic waste collection bags, can liners and lawn and leaf bags in North America and Europe. "Essentially, where a growing food waste collection or organics recycling program exists, the bags come soon after," says Edwards.
The biodegradable grocery bag is a more complex question, as the value is tied to its collection or reuse. In locations with a growing residential organics collection program, biodegradable bags can be reused at home to line bins and hold organic waste.
"This double use is very attractive, and the biodegradable functionality in the compost process means no bags in the landfill," says Edwards.
While biodegradable plastics have been around for roughly 20 years, the right physical properties for bags are only a recent development, occurring in the past eight years, says Edwards. BASF recently launched a foam version of its biodegradable plastic Ecovio. Ecovio is made from BASF's biodegradable polyester Ecoflex and polylactic acid. This past summer, Ecoflex and Ecovio received the iF material award for 2007 from The International Forum Design (iF), a design center in Hannover, Germany.
THE COST OF CONSERVATION
Although the bag conversion and freight cost are approximately the same on a bag-to-bag basis, in general, biodegradable or compostable bags cost three to six times more than traditional bags, according to BASF.
The raw materials needed to produce a truly compostable bag (one that biodegrades in compost) are two to three times that of polyethylene (PE).
According to the California Grocers Association, which opposed San Francisco's recently-implemented ban of plastic grocery bags, standard plastic bags cost about 2 cents (1 euro cent), a paper bag 5 to 8 cents, and a biodegradable bag can cost roughly 15 cents.
These relatively high prices are one of the "major problems" still facing the biodegra-dable polymer industry, notes Schlechter.
The US' Textile Bag and Packaging Association, based in Michigan, is promoting bag recycling programs as opposed to outright bans.
Bag bans could create new environmental problems, according to association president Mike Lawrentz. Some degradable bags break down into tiny flakes of PE, which would still persist in landfills, he points out.
The Berlin-based trade group European Bioplastics projects that global bioplastic production (which includes biodegradable as well as nonbiodegradable materials) will triple by 2011, to 3bn lbs (1.36m tonnes). Comparatively, the US produced roughly 114bn lbs of plastic resin in 2006, says the ACC.
US-based market research firm Freedonia Group estimates that degradable plastics demand in the US will grow by 17%/year to around 507m lbs by 2010, with a value of $610m.
According to a recently-released report by BCC Research, the global market for biodegradable polymers reached 541m lbs in 2007, and is expected to increase to over 1.203bn lbs by 2012, representing a compound average annual growth rate (CAGR) of 17.3%.
Compost bags have the largest share of the market, with nearly 242m lbs in 2007. The compost bag segment is projected to reach 586m lbs by 2012, a CAGR of 19.4%.
The major drivers for the US market, according to BCC Research, are mandated legislation and prospective increases in landfill pricing - neither of which are expected to occur within the next five years - as well as the search for alternatives to petroleum-based products. Edwards notes, though, that "compostable bag use will continue to grow along with organics recycling."
PLASTIC BAGS ARE VALUABLE
Doris de Guzman/New York
The ubiquitous plastic bag from your grocery stores is probably worth more than what you didn't pay for, and with the worldwide surge in plastic bag bans, the American Chemistry Council (ACC) is making sure consumers won't find that out the hard way.
"Plastic materials are really too valuable to waste and recycling is the only responsible, right way to go," says Keith Christman, senior director of packaging for the ACC's plastics division.
"Nationwide, over 650m pounds [295,000 tonnes] of plastic bags and film are annually recycled," he notes. "These materials are made into useful new products such as low-maintenance fencing and decking, building and construction products, and new carryout bags."
Christman also points out that most people like to reuse their plastic bags for lining small trash cans, for diaper waste and for picking up after their pets. In an ACC survey, 92% of consumers report that they reuse their plastic bags, making them more beneficial to the environment "because it prevents them from buying another bag for the same purpose," he points out.
"People really value their plastic bags," says Christman. "Plastic bags ultimately provide an opportunity to reduce our environmental footprint by using less energy, less greenhouse gas emissions and less water."
To carry out their multimillion-dollar recycling mission and to prevent further bag ban policies, the ACC's plastics division recently launched a new group called Progressive Bag Affiliates, composed of plastic bag manufacturers and resin producers.
The ACC says it is currently working on implementing a recycling approach throughout California, which already mandated plastic bag recycling. Other states such as Connecticut, Illinois, New Jersey and Rhode Island are said to be considering similar legislation.
"Cities such as New York, Chicago, Philadelphia and Phoenix are already bringing plastic bag recycling to their jurisdictions," says Christman.
To read Doris de Guzman's Green Chemicals blog, go to: https://www.icis.com/blogs/green-chemicals/
For free details on polyethylene, visit: https://www.icis.com/v2/chemicals/intelligence.aspx