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How to choose the right biodegradable bag?

By Bhavani Prakash

One question that is often asked of us is how to choose the right biodegradable bag as an alternative to plastic bags. This article should hopefully help you make a better decision.

What is the problem with conventional plastic bags?

Photo Courtesy: Waygood on Flickr

Photo Courtesy: Waygood on Flickr

Conventional plastic bags are made from polyethylene, which is derived from finite fossil fuels such as natural gas and petroleum. The problem with plastic bags is that they can hang around in our planet for a thousand years apart from creating other problems:

-          in landfills, plastics leach contaminants into the soil, polluting the water table. They also emit methane which is a greenhouse gas.

-          if incinerated, plastics release dioxins – the most lethal carcinogens made by humans. Only few incinerators in the world have “advanced scrubbers” to remove these dioxins. Even if they do, they are still emitting greenhouse gases into the atmosphere which adds to the global warming problem.

-          They find their way into rivers, seas and oceans and choke and kill animals. The Great Pacific Garbage Patch a large vortex of plastic is in the middle of the North Pacific Ocean. It’s a continuous stretch of plastic about the size of the state of Texas, USA! And there’s another one which has been found in the Atlantic Ocean!  What’s worse is that plastics “photodegrade”- which means they disintegrate into microscopic particles without losing any of their characteristics as polymers, and get into the food chain as they are ingested by aquatic organisms.

Are biodegradable bags the solution?

The term “biodegradable”  is used to describe something that decomposes into tiny fragments. Unfortunately, this doesn’t always mean it’s the most environmentally friendly solution, because manufacturers can make all kinds of green claims about “biodegradability.” For example, a bag may biodegrade about 30% and still pass off as biodegradable. And many manufacturers put their ingredients in fine print, so buyer beware.

Ideally, you’d want a product that ultimately becomes what it is meant to become: water, CO2 and biomass. Water and biomass should go back to the soil to be eaten up by various microorganisms. The process should be carbon neutral because the carbon that was sequestered by the plant matter goes back to the atmosphere at the end of the lifecycle.

Biodegradable bags need specific conditions such as the right amount of light, moisture and oxygen to decompose, which may be provided by industrial composting facilities. So don’t be surprised if it takes much longer under conditions at home. Also,  just because a product claims to be “biodegradable,” it doesn’t say anything about toxicity of the residues.

Biodegradable bags are meant as a solution to managing waste, only if they are meant for composting because:

-          they can’t be recycled. If a “biodegradable” bag is sent for recycling, the entire batch of recyclable stuff will be rejected.

-          there is not much point if the waste is sent to the landfill. In a landfill, there is very little oxygen, and very little water, because landfills are designed to crush and compact waste – not aid waste in biodegrading.  In addition, under “anerobic” conditions, such bags are likely to release methane.

-           if waste is sent to the incinerator, net carbon emissions may be neutral, but it does not lead to reduction of overall waste or close the loop.  As biodegradable plastic (from plant matter) actually slows down the incineration process, countries like Singapore, where most of the waste is incinerated, do not really encourage the reduction of polythene based plastic bags, unfortunately.  So using biodegradable bags in this larger context, may get you the satisfaction of just doing “less bad” without really solving the problem of waste management.

According to the American Society for Testing & Materials (ASTM), in order for a plastic to be called compostable, three criteria need to be met:

Biodegrade – break down into carbon dioxide, water, biomass at the same rate as cellulose (paper)

Disintegrate – the material is indistinguishable in the compost, that it is not visible and needs to be screened out

Eco-toxicity – the biodegradation does not produce any toxic material and the compost can support plant growth

Assuming the biodegradable bag is for composting, how do I choose the right one?

When you pick up a biodegradable bag from the shelves or accept one from the supermarket, ask yourself these questions as you read the labels.

1. Is there any petroleum content?

Choose bags which are made 100% from plant matter.  The label should specify 100% corn, yam, potato, sugarcane, wheat, tomato starch, for example. To confirm, look out for the logo for the ASTM D6866 or the European CEN 15747 standard, which ensures that the raw material used is plant based.

On the other hand, if the bag has petroleum content, it’s a no-no. If the label says polyethylene or  “oxo-degradable” it is basically a petroleum based plastic with additives to speed up biodegradation. Such plastic bags break down into fine dust after coming into prolonged contact with sunlight or heat. They are not environmentally friendly, as they are mostly not suited for recycling or composting where they may have heavy metal residues.

Many major supermarket chains like Tesco dish out “100% degradable bags” which will most likely end up in municipal waste, complicating both recycling and composting efforts.

2. Does it conform to international standards?

As a buyer, it’s really important to get a product that conforms to a standard that entails rigorous testing. It’s easy to be taken for a ride, especially since the word “biodegradability” is construed as eco-friendly, whereas it may not be the case.

There are currently few international organizations which have established standards and testing methods for compostability, namely:

The ASTM, CEN and DIN standards specify the criteria for biodegradation, disintegration and eco-toxicity for a plastic to be called compostable.

  • Biodegradability is determined by measuring the amount of CO2 produced over a certain time period by the biodegrading plastic.  The standards require 60% conversion of carbon into carbon dioxide within 180 days for resins made from single polymer and 90% conversion of carbon into carbon dioxide for co-polymers or polymer mixes.
  • Disintegration is measured by sieving the material to determine the biodegraded size and less than 10% should remain on a 2mm screen within 120 days.
  • Eco toxicity is measured by having concentrations of heavy metals below the limits set by the standards and by testing plant growth by mixing the compost with soil in different concentrations and comparing it with controlled compost

EN13432 logo ASTM D6400 logoThese are the ASTM D6400 and EN 13432 logos  to look out for:

 

 

3. Is it suitable for home composting?

ok_compost-homeIf you’re going to use the biodegradable product for home composting then you need to look out for a certification such as OK Home Compost which ensures that the bag decomposes at a temperature lower than 55-60 degrees C, specified for industrial composts.  The Belgian Company, Vincotte issues the certification.

4. Where are the raw materials grown and do they replace food crops?

This is probably more difficult to judge from the labels.  Take the extra step and check the manufacturer’s website or write to them for more information.  Ultimately, we should not be replacing one problem (waste management) with a larger problem( food crisis), especially if the plants are products of industrial agriculture and use food starch as opposed to plant residues.

Large scale use of corn may also mean the use of Genetically Modified ingredients. As this Guardian article points out:

Concern centres on corn-based packaging made with polylactic acid (Pla). Made from GM crops, it looks identical to conventional polyethylene terephthalate (Pet) plastic and is produced by US company NatureWorks. The company is jointly owned by Cargill, the world’s second largest biofuel producer, and Teijin, one of the world’s largest plastic manufacturers.

Pla is used by some of the biggest supermarkets and food companies, including Wal-Mart, McDonald’s and Del Monte. It is used by Marks & Spencer to package organic foods, salads, snacks, desserts, and fruit and vegetables.

So, just tell me…which brand do I use?

I have evaluated one brand called BioBag.  (If readers have done their own evaluation or would like us to evaluate some other brands, kindly share with us.  )

BioBag is the largest selling biodegradable bag in the world. The biodegradable plastic is made in Norway.  It

  • is made from 100% corn
  • conforms to US Standards ASTM D6400- 99 and European Standard EN 13432,so it biodegrades, disintegrates in a compost, without toxic residues
  • conforms to OK Home Compost standard so it is suitable for home composting
  • conforms to Debio’s Regulation on Production and Labelling of Organic Agricultural Production, so it has no genetically modified ingredients

In a correspondence with them about 3 years ago, I was told that they use marginal land in Italy and France, not suited for food production. However, I don’t know the latest situation. Considering that there is a rapid growth in the demand for their products, it would be interesting to find out if they need to diversify their sources.

Do I really need a biodegradable bag?

A more fundamental question is whether we really need a single use product at all – especially one that has to travel half-way across the world to reach our home?  If the best use for biodegradable bags is for composting, is there some way we can avoid the use of plastic bags (biodegradable or otherwise)?

Here are some ways to reduce plastic bag consumption specifically for composting:

- Use reusable bags made of compostable fibres such as cotton, canvas, jute and so on.

- Collect plant and kitchen waste in old plastic box or big stainless steel container with a tight lid. I empty it every day into my compost heap and wash and dry the container for use the next day.

- For dog poo, you can make bags with double layered newspapers. The papers compost along with the poo. They should not be mixed with compost meant for the garden, but in a separate compost.

Conclusion:

With so many companies entering the “biodegradable” plastic market, it is easy to take consumers for a ride. Without any certifications, it is difficult to judge claims of biodegradability, compostability and non-toxicity.

Use 100% Biodegradable and compostable bags, made fully from plant matter. Ensure they conform to internationational standards such as ASTM D6400-99 or EN 13432 & EN 15457.  Ask yourself whether the end use is meant for composting, as there is little point in using them if the waste is headed for the landfill or incinerators.

Use them if  the waste will reach a community, municipal or industrial compost facility. If it is for your own home use, check for the OK Home Compost Logo. Use sparingly, as you can always collect compostible matter using other containers such as old plastic bins, old wooden crates, stainless steel tins that you already have and can reuse by transferring the contents into your compost bin, pit or tumbler.

If I’ve missed out something or you have some suggestions to make regarding this topic, do write in. We look forward to hearing from you.

Further links you may be interested in:

Guardian Article:  “Sustainable” bio-plastic can damage the environment

Mail Online: Tesco’s “green” bags are WORSE for the environment

BPI : The Myths of Biodegradation

Zero Waste California with Stanford University (for discussion and not for quoting) : Performance Evaluation of Environmentally Degradable Plastic Packaging and Disposal Food Service Ware

 

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Posted by on May 17 2010. Filed under Composting. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry

8 Comments for “How to choose the right biodegradable bag?”

  1. [...] This post was mentioned on Twitter by ecowalkthetalk. ecowalkthetalk said: How to choose the right biodegradable bag? http://bit.ly/bbYctN [...]

  2. another typically comprehensive article from you. :)

    My only concern is that it is too complex and confusing for the typical consumer to choose the right bag, they will simply give up and take the easy way of using plastic bags instead.

    any idea where Biobag could be found in Singapore?

  3. Thanks, Hun Boon…the topic is complex..that’s why it’s so easy for a consumer to think he or she is doing good by using a biodegradable bag, without using it for the right purpose (composting). I hope I clarified with the 4 questions individuals need to ask 1) Does it have petroleum content – choose 100% plant based ones 2) Does it conform to International Standards – how else do we know with certainty it is biodegradable, compostable and leaves non-toxic residues 3) Can it be used for home composting (if that is the intention) and 4) Does the raw material eat into food crop production?

    The easy thing is to use plastic bags…however as a society, we need to move away from plastic bags…and some countries are heading in that direction – Ireland has imposed taxes on plastic bags, Bangladesh has banned the usage of plastic bags.

    You’d find BioBags in Singapore in many Cold Storage outlets, as well as Eco Store at China Town, 26A Pagoda Street. It’s found in many countries, online at least, such as US, UK, other parts of Europe, Australia for example.

  4. 2010 The Second China (Shenzhen) International Biological Plastic Exhibition & Forum

    DATE:Nov 16th~17th 2010
    VENUE: Great China International Exchange Square Shenzhen

    Introduction

    At present,the demand for bio-degradable materials is huge both in China and in the world. The quantity needed at home in the packing industry and catering industry alone totals more than 3million tons.The international market demands even more, with a 30-50% year-on-year increase.,the domestic demand in 2010 is expected to reach 13.437million with a total market value of over 150 billion, while that of the world will be about 20million ton. Recent years, the bio-degradable industry has witnessed a rapid development. National policies are made to escalate the industry to a high-end one, which would hopefully be the key areas in bio-degradable and abosorbable material industry by 2015.
    The 2009 Shenzhen China International Bio-plastic Exhibition, is the most time-honored and professional of its kind in China. It serves as a platform for trade and technology exchanges for business people from all over the world. In 2009, enterpreneurs from about 20 countries and areas paticipated in this fair, many of which were from the U.S.A., the U.K., Germany, Italy, Tailand, New Zealand, Singapore, Taiwan and Hongkong. During the exhibition, world-renowned coropetations like as BSF and INNOR had discussions on the application and future of biodegradable materials.
    To meet the demands of many bio-degradable enterprises, we will hold the Second Shenzhen International Bio-plastic Exhibition will be held in Great China Exchange Plaza from 16th the 17th, November 2010. We will invite business people in plastic manufactoring ,catering, packaging, machine building, and top officials form star-rate hotels.Besides, officials from local government departments for economic development and International Investment Organization will also be invited to the fair. The fair is expected to be of high-level and distictive feature with an inflence on the world bio-degradable industry.

    Scope of Exhibits:
    Bio-plastic products: Biodegradable Bags, Biodegradable Bowls, Biodegradable Cups, Biodegradable Containers, Biodegradable Plates, Biodegradable Trays,Biodegradable Cutlery, Biodegradable Knives, Biodegradable Forks, Biodegradable Spoons, Biodegradable Sporks, Cornstarch tableware,Oxo-Biodegradable masterbatches,Bio-plastics additives,Corn Starch Bags, plastic container, Sugarcane Plates and Bowls, Biodegradable plastic bowl,Biodegradable Catering Serving Fork,Biodegradable Compostable Bagasse Plates,Biodegradable Forks, Biodegradable Heavy Duty Picnic Pack,Biodegradable Knives, Biodegradable Catering Salad Tongs,Biodegradable Catering Serving Fork,Biodegradable Catering Serving Spoon,Biodegradable Catering Small Tongs,Biodegradable Spoons,Biodegradable Cutlery,Biobased substitutes to traditional plastics, 100% Biodegradable,100% Compostable,100% Biodegradable Cardboard,Biodegradable shopping bag, Bio-degradable plastics,Biodegradable bags,Pulp environmental tableware,Molded Pulp,Molded Pulp Cup,Medical bio-plastic products,E-Bio Plastic Products,Plastic Food Biotechnology,Bio-plastic cell phone case,Bio-plastic cartridges,Bio-plastic toothpaste box,Bio-plastic comb,Bio-plastic toothbrush,Bio-plastic toothpick,Bioplastics Cup,Bio-plastic products and other products.
    Fees:
    Cost to exhibitors
    standard booth(3m×3m): 2700USD,corner adds 10%
    spare room: 250USD per sqm
    Ads in EXPO magazine : cover:2500USD bottom :2000USD inside:1500USD

    CONCACT:
    ShenZhen Howell Exhibit Scheme CO., LTD

    TEL:86-755-28188469 13684940952 Liu Lu
    EMAIL:mickyny@126.com;lu_liu1989@163.com
    FAX:86-755-83721979 msn:belly201059@hotmail.com
    WEB:www.szhowell.net/en

  5. Bhavani,

    There is a significant error here. You correctly mention ASTM D6866 and then mention again the importance of no petroleum-based content. ASTM D6400, by the way, does not answer the question as to what kind of carbon content is in the bag. You then go on to select the brand name the “BioBag,” and even repeat somebody else’s words that it “is made from 100% corn.” I am sorry, but these are not true. The BioBag’s and Mater-Bi film DO NOT have an ASTM D6866 100% “biobased” rating. See: http://www.cortecvci.com/Publications/Reports/06-037-1125.pdf BioBag is unclear about this, but from even them you will see that they only claim 25 to 55% “biobased” content depending on their particular product in question, meaning they contain almost half fossil fuel derived carbon content. Therefore, they also cannot be 100% from corn. BioBag is the top selling ASTM D6400 “compostable” bag, but they are not 100% from corn, and it cannot be said they have no petroleum based polymer content.

    I have been looking for a poly bag that is compostable and ASTM D6866 100% “biobased” and the only bags that I have found that appear to meet those requirements are the Natur-Tec Naturbag and possibly 3 bags being put out by Wuhan Tankon Co. in China.

  6. Thank you very much for pointing this out, Mauibrad. I’d be most interested in knowing more about the bags you have mentioned. Please share the weblinks related to these. I’m also concerned about the larger picture – whether the biobased material used from plant matter competes with food sources or land that could otherwise be used for growing food.

  7. I have to make a correction myself. It appears that the Natur-Tec Natur-Bag is not 100% biobased, although I am still waiting to hear from them to be certain. Also, the Wuhan Tankon Co. bags are absolutely not 100% biobased.

    In further looking, the source that you mentioned, Vincotte, is a good one to find biobased products. From there it looks like NatureWorks LLC may putting out a film 100% biobased that can be turned into bags. I have to inquire more with them. Also, another Chinese company, Wuhan Huali puts out a corn-based product that may be close to 100% biobased. There are a couple of other 100% biobased products that I have come by, namely a sugarcane polymer from Braskem that is 100% biobased, but I don’t know if it can or is being used to make products like bags yet. Anyway, the one that looks most promising is NatureWorks LLC.

  8. Uh, well, Braskem and NatureWorks both have a 100% biobased resin, but there are apparently no 100% biobased poly bags out there. Maybe just being 100% compostable under ASTM D6400 is good enough?

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