What is an oxo-biodegradable plastic?
It is a general understanding that discarded conventional plastic packaging films & carrier bags will endure in the environment for many years. This is clearly an issue in terms of increasing requirements for landfill sites for those items collected as refuse & also the damage to wildlife & the unsightly nature of these items left as litter. To counter these issues, there is a movement to manufacture packaging products which will have significantly reduced lifetimes once discarded as waste.
One approach to this is to incorporate additives into materials such as polyethylene (PE), polypropylene (PP), polystyrene (PS) & polyethylene terephthalate (PET) which will accelerate the degradation of the plastic in the environment.
These additives (pro-oxidants) use a salt of a transition metal such as cobalt (Co), iron (Fe), manganese (Mn) or nickel (Ni) to drive the oxidation process which, under the action of heat or light, will reduce the molecular weight of the polymer to a level where bacteria & fungi in the soil or disposal environment can further reduce the material into water, carbon dioxide & biomass.
Ref 1: http://www.rapra.net/consultancy/biodegradable-plastic.asp
Biodegradable Plastics: True or False? Good or Bad?
By Brenda Platt
Coordinator, Sustainable Plastics Project, Institute for Local Self-Reliance
In an attempt to position their products as green, several companies have recently introduced biodegradable products made from conventional plastics. Products and claims include:
The Biogreen Bottle™ reusable water bottle made from LDPE: “100% biodegradable, recyclable and reusable” “BioGreen Plastic will fully biodegrade in home compost heaps, commercial composting operations, buried in the ground, buried in landfills, tilled into the soil, having been littered etc. Most importantly, this process is by far the most widely applicable, proven technology for the biodegradation of plastics in the world.”
Aquamantra’s ENSO™ single-use water bottle made from PET: “Launches world’s first 100% biodegradable-recyclable bottle” “ENSO™ bottles are validated through third party ASTM standard tests.” “ENSO Bottles are 100% biodegradable and compostable” “Our PET bottles will biodegrade in anaerobic and aerobic/compostable environments”
Perf Go Green biodegradable plastic bags, including lawn and leaf bags: “Once Perf Go Green products are discarded (whether that be on land, underground, at sea, etc.) they will completely degrade and break down returning to nature in as little as 12-24 months – leaving absolutely NO residue or harmful toxins.”
PolyGreen polyethylene plastic newspaper bags by GP Plastics Corporation: “100% oxo-biodegradable” “Because they are conventional plastics with an additive, they are compatible with the existing recycle stream.”
Planet Green Bottle Corporation’s Reverte™ oxo-degradable PET plastic bottle: “The PGBC oxo-biodegradable PET plastic bottle is compatible with all current recycling streams for PET plastic bottles.” “Reverte™ does indeed firstly break down the PET into fragments but then these fragments are bio-digested until all that ultimately remains is CO2 and water.” “Reverte™ PET bottles will oxo-biodegrade if they find their way into the ocean since in this environment there is usually plenty of oxygen, UV light and heat which are required for the oxo-biodegradation process.”
Discover’s biodegradable PVC credit card: “The biodegradable Discover Card is made of biodegradable PVC, a substance that allows 99 percent of the card plastic to be safely absorbed when exposed to landfill conditions.”
Too good to be true? You bet. Most if not all these claims are unsubstantiated.
The companies selling these products are taking advantage of markets that are unaware of the difference between certifiable compostable and biodegradable products and those that are not.
Truly biodegradable plastics are plastics that can decompose into carbon dioxide, methane, water, inorganic compounds, or biomass via microbial assimilation (the enzymatic action of microorganism). To be considered biodegradable, this decomposition has to be measured by standardized tests, and take place within a specified time period, which vary according to the “disposal” method chosen. The American Society of Testing and Materials (ASTM) has created definitions on what constitutes biodegradability in various disposal environments.
Plastics that meet ASTM D6400, for instance, can be certified as biodegradable and compostable in commercial composting facilities. In Europe the equivalent standardized test criteria is EN 13432. In the US, there is a biodegradability standard test method for soil (ASTM D5988), for marine and fresh water (ASTM D6692 and ASTM D6691), one for wastewater treatment facilities (ASTM D5271), and one for anaerobic digestion (ASTM D5511). Other countries have similar standards and certifications. Belgium is unique in offering “The OK Compost HOME” mark, which guarantees that the product can be composted in home composting systems.
Steve Mojo of the Biodegradable Products Institute (BPI) has repeatedly asked to see Aquamantra’s claims that its PET will fully biodegrade in landfills or marine environments. “Nothing of credible science has come back.”1 On oxo-degradables, Steve acknowledges these plastics can fragment within 3 months but clarifies that fragmentation is not a sign of biodegradation and that no data shows how long these plastic fragments will persist in the soil or the marine environment. According to Dr. Ramani Narayan, an international expert on biodegradability and a professor of Chemical Engineering & Materials Science at the Michigan State University, some evidence presented shows partial degradation but “the key phrase is ‘complete’ – if they are not completely utilized, then these degraded fragments, which may even be invisible to the naked eye, pose serious environmental consequences."2
Oxo-degradable plastics do not meet any standards in place for biodegradability and should not be considered biodegradable. In fact, the US National Advertising Division of the Council of Better Business Bureaus has recommended that GP Plastics Corporation modify or discontinue some of its advertising claims for its oxo-degradable PolyGreen bags.3 In California, a study sponsored by the California Integrated Waste Management Board (CIWMB) and led by Dr. Joseph Greene at California State University showed that oxo-degradable bags on the markets showed no biodegradation.4 Its findings and the proliferation of unsupported biodegradability claims, led the state to pass two laws effective January 2009 that restrict use of the terms “compostable,” “biodegradable” “degradable,” and “marine degradable” on plastic bags.5
Claims of recyclability are likewise unsubstantiated. The largest recycler of plastic bags in the country, TREX plastic lumber company, issued a statement last September that reads in part: “Unless and until the long term durability testing concludes that the oxo-biodegradable polyethylene plastic (OBPE) will not have an adverse effect on our product, Trex cannot support the introduction of OBPE materials into traditional recyclable polyethylene streams.” Indeed even Planet Green’s web site admits “our work with PET recycling has only been conducted within our laboratory facility.”
Even more to the point, perhaps, is that being designed to biodegrade in a landfill does not make a product environmentally sound. In fact, the opposite is true. Landfills are a top source of methane, a greenhouse gas 72 times more potent than CO2 in the short term. Methane results when materials biodegrade under anaerobic conditions in a landfill. To mitigate climate change, we need to STOP biodegradable materials from entering landfills, not encourage more landfill disposal. In fact, in greenhouse gas inventorying protocols, nonbiodegradable plastics get credit for sequestering carbon in landfills. To be considered green or sustainable, products should be designed to be reused, recycled, or composted (among other criteria).6
While many bioplastics are certifiable as compostable in commercial compost facilities, not all can be home composted and not all are biodegradable in the marine environment. Furthermore, a number of petrochemical-based polymers are certified biodegradable and compostable. Biodegradability is directly linked to the chemical structure, not to the origin of the raw materials.
Considering use of biodegradable products? Ask for proof of biodegradable certification and biobased content.
Ref 2: http://www.sustainableplastics.org/spotlight/biodegradable-plastics-true-or-false-good-or-bad