The Material Facts About Bioplastics
The Material Facts About Bioplastics
Our recent webcast, "A New Life for Plastics: End-of-life Solutions in the Age of Greener Materials," drew a sizeable audience -- and a sizeable number of questions. We only were able to address a handful of them during the webcast, so we asked the three participants -- William Hoffman, environmental scientist in green chemistry at UL Environment; Robert Whitehouse, Director of Applications Development for Metabolix, Inc., a leading bioplastics company; and Kelly Lehrmann, consultant with the German bioplastics firm FKuR -- to respond to some of the remaining questions.
Here are their thoughts on the benefits of bioplastics, the differences among various biobased plastics, the role of municipal waste agencies in creating a composting infrastructure, and other things.
The archived webcast is available for listening here. Access is free, though registration is required.
What is the best benefit from a bioplastic: the biodegradability or the renewable source reducing the carbon footprint?
William Hoffman: Not all bioplastics are biodegradable. Braskem (Green PE) and PolyOne (ReSound) both produce biobased materials which are not biodegradable. Ultimately, the "right" answer to this question would depend on the application for which the material is designed (and the end-of-life associated with that application). Let's say the material is to be used in a durable application, perhaps an appliance housing where that part needs to last the life of the appliance (approximately 10 years), then biodegradability is not an ideal characteristic. On the other hand, if the material is used in a disposable packaging application, biodegradability would be a desirable characteristic of the end-product since so much single-use plastic packaging end up in landfills.
Robert Whitehouse: The best benefit is a bioplastic that is both biobased and biodegradable. As an example, Mirel™ bioplastics is made from annually renewable resources, corn sugar, and is biodegradable in a wide range of environments including natural soil and water environments, in home and industrial compost facilities where available, and anaerobic digestion. The combination of biobased and biodegradable helps to reduce reliance on petroleum and can help to reduce the amount of waste sent to landfills or incineration.
What about anaerobic degradation in a closed landfill?
WH: Once a landfill is closed, the conditions that encourage biodegradation – recirculating leachate, which carry microbes and elevated moisture levels are removed. Indeed, closed landfills resemble the "dry tombs" that William Rathje studied in his Garbage Project in the 1970s.
RW: Landfills are typically unmanaged with regard to microbial activity and so degradation is very difficult to predict. Managed anaerobic degradation facilities typically take from 20 to 50 days for organic carbon conversion.
How long does it take ASTM D6400 to fully degrade into safe emissions in comparison to the other biodegradable products?
RW: ASTM D6400 was developed around the typical yard waste composting process of around 90 days.
What happens to the CO2 that's produced during the degradation?
RW: It is sequestered in making new plant-based crops.
What are the exact conditions of a landfill to facilitate biodegradation? How many landfills with these conditions currently exist (and in which markets)?
WH: There are two types of landfills. One is set up so that nothing interferes with the garbage, and is meant to be closed off and capped over. The other type is an actively managed landfill. Actively managed landfills are designed to foster biodegradation, which yields methane to produce energy. To break down organic matter, certain conditions need to be present, such as the landfill needs to be kept at a certain temperature, roughly 50 degrees Celsius. Moisture level, solids level and microbial level must be maintained to induce the breakdown process. Microbes live in the recirculating leachate that is distributed around the landfill to foster the biodegradation process. There is some variability depending on regional location, the southeast in the US is likely to be managed at a higher temperature, due to the local climate.
As for the number of landfills with this condition, according to the EPA, of the 2,300 or so currently operating or recently closed MSW landfills in the United States, more than 490 have landfill gas utilization projects. EPA estimates that approximately 515 additional MSW landfills could turn their gas into energy, producing enough electricity to power more than 665,000 homes.
Can you speak a bit about the recyclability of biobased plastics? For example, Coke now has a PET PlantBottle that is 100% recyclable. How is this resin different from other biobased plastics?
WH: Coca-Cola's bio-PET is more similar to Braskem's Green PE than to PLA or PHA. Bio-PET has a biobased precursor: sugar-cane derived ethylene glycol. Despite this biobased feedstock, bio-PET is produced in a traditional PET process and the result is a material identical to 100% fossil fuel-derived PET. Therefore, Coca-Cola's PlantBottle can be put in the same recycling stream as its fossil fuel-derived peers.
PLA and PHA have completely unique routes to polymerization. Since there are no wide-spread programs to segregate and capture these materials for recycling, they need to be excluded from the recycling stream in order to prevent contamination.
RW: Biodegradation of biobased plastics is a full closed-loop recycling process. The CO2 evolved is then sequestered in farm crops to make the feedstock for biobased plastics
Is recycling even a viable option? Why would you want to spend all those resources creating a biobased plastic, to then just bury it in the ground?
RW: The issues are around using a renewable resource product based on farm based crops and not depleting the oil reserves which are better used for energy.
Many composters sell product into organic agricultural markets. Currently, bioplastic resins are not listed as acceptable substances under the National Organic Program. Are you aware of any initiative to address this issue with the NOP?
RW: Yes, BPI and ASTM are working to address this issue which is a process of education
Related to the issue of recyclability of bio-plastics, what is the latest on developing a recyclability standard, whether for biobased plastics or fiber-based, etc?
WH: We have not seen any final decisions, but have heard two things: 1) the Association of Postconsumer Plastic Recyclers (APR) and ASTM have been looking at a new recycling code for PLA; and 2) there is only one PLA recycler in the U.S. -- Plarco, in Eau Claire, Wisconsin. Plarco is actually breaking down the PLA and returning lactic acid back to Natureworks to be used as feedstock for new PLA resin.
My company has a huge requirement for poly bagging of apparel product coming out of China. I am told the issue on bioplastic application is too quick of a degradation under warehouse and shipping contributions. Are there ways to get around this?
RW: This is not true from biobased and biodegradable products made in USA and Europe. In the absence of direct contact with the appropriate microorganisms (present in soil or anaerobic digesters) the fabricated products have good stability in the order of years.
Kelly Lehrmann: FKuR GmbH has already commercialized a garment bag for a top-name designer label in Italy. In the past, conventional polymer materials have been designed to resist degradation. The challenge is to design polymers that have the necessary functionality during use, but disintegrate after use. FKuR compounds fulfill these requirements in an optimized way. Biodegradation takes place only under certain conditions -- under the presence of heat, moisture and micro-organisms. FKuR resins are compounded to reach maximum mechanical and barrier properties, as well as achieving longer shelf life when compared to basic bio raw polymers. We can design a resin to meet your specific mechanical property needs, anything from clear to gloss finishes, rigid to flexible. All our Bio-Flex materials can be dry blended with each other to achieve various product requirements as their molecular chains are all similar and compatible.
Ms. Lehrmann's description of municipal involvement places additional costs on local taxpayers; how do we get the manufacturers more involved with the end-of-life management of their products?
RW: Most towns charge some form of tax or levy to manage home waste collection and disposal. Using biodegradation processes, this reduces the amount redirected to landfills and the increasing extra cost to manage the environmental impacts of poorly managed landfill operations with regard to gas emissions and liquid waste into the water table.
KL: The municipal involvement was used as an example of successful projects I've seen within the past eight years. In order to motivate manufacturers in becoming more involved with the end-of-life management, there need to be obtainable certifications and regulations that make sense for the bottom line along with providing a clear path to the consumer for end-of-life disposal. For example, it's beneficial to have a compostability standard (ASTM D 6400), but if the majority of consumers do not have access to a hauler which can bring their waste to a commercial compost facility then the intended end-of-life for the products is not able to be reached
If the focus is solely on compostability, then we need to seek broader solutions besides aerobic commercial compost facilities. Even recycling is limited in many communities and most consumers are still confused as to what can or can't be placed in their recycle bins.
Until the proper channels for disposal are in place the focus can be placed on reducing carbon emission and fossil fuels on the production side rather than on the disposal end. Therefore, using renewable materials in manufacturing can still lessen the environmental impact regardless of the end-of-life solution available. The future for America can be what has been realized in places like Germany. Landfills are allowed to accept only treated waste that is inert to the environment. All plastics, including bioplastics, are banned since they pollute the environment with methane gases.
With respect to the bio-sources of the plastics described by these presenters, are there any conflicts with sources for food products? A few years ago, people started using corn as a plastic feedstock, which increased corn prices to become unaffordable to low-income people. Are there any similar issues with these plastics?
WH: Since the overwhelming majority of bioplastics are derived from the sugars contained in plant-matter, agriculture is an immensely important part of the bioplastics supply chain. Because of the way agribusiness is structured in the U.S., it was logical for corn to be the starting point for industrial biotechnology. However, people are now talking about corn-derived polymers such as Natureworks' Ingeo PLA or DuPont's Serona as "first-generation" bioplastics. Today, most producers are aware that bioplastics will never develop broad market access unless their feedstocks do not compete with food sources. Accordingly, over the past few years, we've seen global players bring to market innovations which involve bioplastics derived from high-biomass sorghum, castor oil or even algae. We expect this trend will continue.
What do you have to say about additives like EcoPure that make petroleum-based plastics biodegradable?
RW: They do not work in converting a major portion of the carbon to CO2 or CH4. The residual material may be of a different chemistry to the original material with unknown toxicological impacts.
KL: Products such as EcoPure do not make regular plastics biodegradable. Combining these types of additives to plastic makes regular plastic break down into barely visible particles. Fragmentation of so-called "oxo-biodegradable" plastics is not the result of a biodegradation process but rather the result of a chemical reaction. The smaller particles of plastic will still move through our eco compartments without breaking down. This kind of degradation results in small fragments that pollute compost, landfill or marine environments.
In addition, these materials do not degrade as fast as compostable plastics and may leave small fragments in the soil. These degraded hydrophobic fragments with high surface areas can migrate into the water table and soil where they can attract and hold hydrophobic highly toxic elements like PCB and DDT with up to one million times the background levels -- effectively functioning as a toxic chemical transport system in the environment. Oxo-degradable additives not based on organic material, but which consist of transition elements, like cobalt, manganese, iron or zinc, are even worse. These transition elements promote oxidation and chain degradation in plastics when exposed to heat, air or light. The customer should always demand a respective certification (e.g. ASTM D 6400), which provides scientific data and proof of claims when purchasing material that claims to be biodegradable or compostable.
Photo CC-licensed by Shira Golding.