I’m very happy to note that the article on “How to Make and Use Garbage Enzymes” has stirred a lot of discussion and this has been an opportunity to clarify where the science lies.

I had endorsed Garbage Enzymes enthusiastically as I have personally heard gardeners speak of the positively about the results. These are from 1) Ground-Up Initiative at Bottle Tree Park, Singapore 2) Kampung Senang Charity Foundation in the Community Garden at Tampines, Singapore 3) Bandar Harapan Organic Farm in Malaysia and 4) Nanyang Technological University Community Medicinal Herb Garden (which I discovered after writing the article).

The sum and substance of the feedback is that Garbage Enzymes (the term itself may be a misnomer) can be used as a homemade vinegar for non-edible cleaning purposes. The efficacy of Garbage Enzymes as a fertiliser or pesticide or an air purifier is not yet verified by scientific research.  Even less obvious is its ability to lessen greenhouse gases. There are varying views on its contribution to waste management – in the local context, is composting a better way to manage waste, instead of adding molasses? Or can this be considered as one additional way to manage waste that would otherwise go to the incinerator?

There are two detailed responses to this and we thank both the contributors for their time to clarify the science behind Garbage Enzymes.

The first response is from Dr Vinisha Khemani Kanjilal, who is a Singapore based scientist and runs science based educational programs for children at Green Dots

I read your piece on Garbage Enzymes (GE), and note a few things here:

• The process you describe without doubt is a natural fermentation/anaerobic oxidation whose products are alcohol (incomplete/partial fermentation) and acetic acid (complete fermentation). These are enzymatically performed by natural and mixed microbial cultures in the starting preparation (fruit dregs and vegetable trimmings).

• Fermentation has been used for time immemorial/centuries (and even before the science was clarified by Louis Pasteur) to produce wines and vinegars, sakes and arrack and other variants of these all over the world. Some native populations have preferred pure starting materials like rice bran or grapes, some have been clever to figure out anything with naturally combustible carbohydrates can be converted to sugars and be directed towards production of ethanol and/or acetic acid (aka vinegar). See Wikipedia on Fermentation.

• Thus GEs are not a new discovery by Dr. Rosukon Poompanvong or anyone else in recent times for that matter. Pubmed is a publically accessible repository of all original research published in peer reviewed journals – there is no mention of any work when a search is done on her. Also, the FAO link on her lists many of her achievements. However couldn’t find any English language literature on the internet of any credibility to all the GE uses you’ve listed out on the blog. She is perhaps to be credited for heightening the awareness around reuse of kitchen waste (traditionally discarded in Thailand?) towards production of vinegar via a method that can be simply executed by almost anybody.

• To the best of my knowledge neither the enzymes/biological catalysts from microbes (mostly proteins) nor the microbes themselves would survive the change in pH that happens during the course of a complete fermentation and none of the fruit based enzymes that I’m aware of viz: papain from papaya, bromelain from pineapple, etc. would function in the final and extreme acidic environment of approx.2 that would result when acetic acid is produced as in the GE method described.

• Thus the terminology GE is a bad one (even if but as a colloquial name) for the process described to recycle organic waste by fermentation (in no way attributable to EWTT), but just to be cautious in what it mistakenly connotes.

• In the scope of 3R principles even while trying to be vegetarian and all consuming there will be some organic waste generated. Whether that kitchen waste goes into composting or more pure vermiculture methods, to generate vinegar at home as a cleaner and by reproducing the process described or otherwise is immaterial. They are all effective as recycling methods and would have little to no difference in their pros and cons with respect to global warming, save the fact that an incomplete fermentation (as for example when yeast cultures are used to produce ethanol) actually produces a greenhouse gas as a byproduct viz: carbondioxide (CO2).

• In the same vein, directed waste management practices (See Wikipedia link on Anaerobic Digestion) that produce methane (an alternative source of energy and potent greenhouse gas) if not channelized towards use are effectively adding to global warming.

• Would not make any claims to use of vinegar whether produced by the GE process or otherwise as a fertilizer or pesticide at any concentration. There is no evidence for this whatsoever.

• Sometimes soils are more alkaline than required by plants to grow healthily…so diluted vinegar might help set the pH towards a more neutral or favourable setting…also just perhaps aid in soil loosening. This could be seen as largely beneficial but remains to be tested scientifically and would still not qualify GE as a natural fertlilizer.

• Likewise extreme environments would destroy most microbes so acetic acid like any other corrosive acid would kill some bugs on contact and if used carefully might be usable as a pesticide/insecticide. This potential benefit remains to be tested however in dose dependent studies.

In short would agree with John Cussman that the science presented and claims made on GE are  flawed and somewhere effective microbial cultures that would be enzymatically rich (but which I’ve not done any homework on) are being confused with enzymatic byproducts.

Vinegar in Singapore is cheap especially the 1 SGD/- per litre bottles produced from rice bran. Green Dots uses these in numerous experiments. The cheap vinegar will be effective in glass cleaning, toilet bowls, stain removal on floors, etc just like housewives have known the deodorizing properties of sodium bicarbonate for a long time.

Since I recycle my organic kitchen waste into soups, food for my dog, vermiculture, composting in order of priority – have not felt a need to experiment with vinegar production at home – especially not at the cost of purchasing sugar or honey! However do think it makes a fabulously interesting experiment for children to do and learn from and test some hypotheses inhouse.

Kitchen waste recycled vis vermiculture or composting will undoubtedly have a lower carbon footprint than being deployed with sugar (its manufacture has its own carbon footprint) to produce vinegar and anaerobic gases including CO2 by yeast!

Here’s a link to some recent articles (Article 1 and 2) for producing enzymes and methane from organic waste. Pure cultures of specific fungi have also been used in fermentations to produce antibiotics.

Have known of a scientist from the National Chemical Laboratory (NCL) who was tinkering with more scientific composting methods and using lemon peels for effective pH management 20+ years ago. So also Gandhi’s nature cure ashram in Uruli Kanchan  has for last several decades been recycling organic wastes. Such methods that make local and contextual sense have been around for a long time in the world

The second one I received was from Lam Yuen Sean who’s a PhD student, and a volunteer with Ground – Up Initative, an urban gardening intiative by Tay Lai Hock in Singapore.

GE is definitely not well researched at present, so little technical information can be found about it.  More testing or literature reviews would be required to further support my preliminary views, and this account is by no means exhaustive and conclusive.

Ingredients:

The purpose of molasses or brown sugar is to provide “simple” carbon source or energy for the microorganisms to first feed and grow. When growth is sizeable, the microbes may then turn their attention to the additional food source (the waste materials) that is harder to digest due to the complexity in their molecular structures. This process is usually energy consuming for the microorganisms, and the added sugar may provide them the extra energy needed for this. The airtight container is necessary to promote fermentation (minimize oxygen), and biogases will be produced as by-products of the anaerobic breakdown of the sugars (usually hydrogen, CO2, and less likely methane). Thus, releasing the gases produced, especially during the initial stages, is essential.

Duration:

Can’t find the rationale for the stipulated “3 months”, but I guess this is based on past experiences. Definitely, longer durations would be more ideal to ensure a more complete fermentation process, where there will be none (or little) sugars left, and higher concentrations of products could be achieved. Also, the lack of food and the low pH levels would most likely kill/deactivate the microorganisms present (safer for handling).

Components:

Based on the preliminary test using gas chromatography, the major component of a newly prepared GE is acetic acid (in high concentrations), or “vinegar”. Slight ethanol (or “alcohol”) and propionic acid are also found in older GE samples. Do note that the machine used is calibrated to measure the presence and concentration of certain alcohols and fatty acids, and thus, may miss out several other important components (e.g., enzymes, sugars, amino acids, vitamins, etc.) that may also be present in the liquid. The pH measured for freshly prepared GE is ~4.4, and for the older sample is ~3.1, which will vary depending on the materials used.

Enzymes:

With regards to the enzymes present, it is rather difficult to comment, as I do not have the right equipment at hand. One of the comments made is somewhat true, in the sense that microorganisms possess intracellular enzymes within the cells that may not be easily dislodged into the solution. However, there are microorganisms that secrete extracellular enzymes into the external environment to allow the waste to be broken-down outside the cell. Also, the enzymes here may refer to the enzymes present in the waste material itself. For instance, pineapples and papayas are known to contain bromelain and papain enzymes used for tenderizing proteins, respectively. Therefore, the acidic condition and the fermentation process may allow such enzymes to be extracted from the waste materials into the solution.

Functions:

The high acetic acid concentration and low pH could be the main reasons for the many purposes of GE, as vinegar is well known to be used a cleaning agent, odor removal, preventing drain blockages, etc. Ethanol is known to have antiseptic properties, while propionic acid is used in food preservation. These substances may allow GE to act as an anti-microbial agent, insecticide and pesticide. When diluted, it could provide nutrients to plants due to the “growth hormones”, minerals, enzymes and/or other organic compounds extracted directly or converted from the waste materials. The highlight of GE is that it is organic and can be homemade at low costs, as compared to other products that contain synthetic chemicals (may be toxic to human health or environment) and consume high energy in their production.

Yeast:

On the contrary, please be careful of the white, black or brown layer formed on top of the liquid. Well, it could be yeast, as certain yeast prefers oxygen, thus forming a top layer in contact with the air in the container; but not all yeast strains are harmless. Similar to moonshine production, GE making involves the growth of the “unknowns”, so it is best not to have long direct contact/exposure with this layer or used for consumption purposes.

CO2 and methane:

Not much is being researched in terms of the CO2 production, but it is definitely there. Theoretically, aerobic processes would generate more CO2 than anaerobic processes, due to the more complete degradation of the carbon sources. Methane will only be produced in the presence of methanogens (certain kind of bacteria that are mostly found in swampy areas). Since the microorganisms present in GE are likely to be found naturally on the waste itself, airborne from the surrounding air, from the container or tap water added, chances of methane-forming bacteria to be present would be low.

Ozone:

This is surely more controversial. Ground-level ozone is known to be an air pollutant, causing adverse health effects, and should not be confused with the ozone layer in the upper atmosphere protecting us from the radiation. The low level ozone is generally formed from hydrocarbons and nitrogen oxides in the presence of sunlight. So, don’t think we are able to generate ozone through the fermentation of GE (shaded, and not much nitrogen oxides present); but if we do, it will be very scary… Therefore, those who claimed the benefits of ozone and its formation through GE should further substantiate their points.

EM:

Well, EM is a proprietary product used as a microorganism culture stock for various uses (e.g. composting), where the microorganisms present are known and well studied by the company. The use of EM will be useful in ensuring consistency between the different batches of GE, and since it is claimed to be non-pathogenic, GE practitioners should feel more relieved in terms of user health and safety. Not too sure on the cost and availability of EM in this region though.

Solid waste management:

Rather than to be disposed and incinerated, these waste materials can further serve additional purposes through GE, and subsequently be composted into organic fertilizer. This will surely help in preventing or reducing all forms of pollutions from the improper solid waste management and incineration, as well as to “close the waste loop” and promote recycling of waste back into the earth. Fruit and vegetable wastes are generated in huge amounts from both households and commercial/industrial sectors, and large-scale GE production would help to put these wastes into better uses.

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In Part 1 of this blog, we had talked of How to compost at home – using container pots outlining the composting process using resources at home, what to compost and what not to compost, the “greens” and “browns” to use and to what proportion, as well as to encourage you to convert your garbage into a useful resource for your garden.

In this second part, we continue on the theme of home composting, using aesthetically designed terracotta pots that can be stacked one on top of the other. This makes it really easy to use in small spaces like in kitchens and balconies or apartments. Conceived by the award winning designer, Poonam Bir Kasturi, these pots are called the Daily Dump and are available as an open source licence for anyone to copy the designs and spread the practice of composting.

We had excluded cooked food including meat, fish and bones in the previous method.  Using the Daily Dump, the main thing to note is that the terracotta pots are heavy, so they are not prone to vermins or pests. The composting method which allows for the usual kitchen waste as well as cooked food, uses an accelerator for decomposition, called Biocullum which is available in India.  You could find an alternative EM (Effective Microorganisms) formula from your local nursery where you live.  Also use equal amounts of “browns” by way of sawdust, dried leaves and so on.

The pots or “Kambhas” as they are also known, work as in this diagram.

Here’s a video explaining how the Daily Dump can be used (no audio) 

Here’s a cool fridge sheet for the Daily Dump which shows what can and can’t be composted.

Mrs Navneeth Raghavan: Chennai Clone for the Daily Dump

I had the opportunity to visit Mrs Navneeth Raghavan in Chennai, India recently. She is a “Clone” i.e., she has used the open source designs of Daily Dump to manufacture and sell the terracotta pots at her store.  She explained to me how Poonam Bir Kasturi, the Bangalore based originator of the concept had encouraged her to start making Daily Dumps in her city and how the different distributors or clones in India have come together as a supportive network.  Mrs Raghavan hopes to see many more clones in Chennai, and that people start composting on a wider scale.

 
And we hope to see a revolution too, in the way you think of your waste and manage your waste. Composting is an easy, cost-effective, and a wonderful way to convert trash into resource. You’ll also be doing a huge service to the planet and your descendants by helping keep tons of garbage out of landfills, and toxic poisons out of water, air and soil that come from plastic bags.

Happy composting!

Further links you may be interested in:

EWTT : Poonam Bir Kasturi :  Designing the Daily Dump (which features an interview with the lady who behind this innovative design concept)

EWTT: Part 1:  How to compost at home – using container pots

The Daily Dump website

Be a Daily Dump Clone

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Of the various recycling practices that I personally follow, the most satisfying one is converting my kitchen waste into compost - a very valuable resource for my plants.  My family is often amused when I exclaim with glee at the slimy, guey, rotting vegetable and fruit waste that I collect every day and call it my precious “gold!”   When the paradigm shift comes about, we will begin to see all “waste” or “garbage” as something tremendously useful for us and the environment, and realise the tragic futility of bagging it in wasteful plastic bags for landfills or incinerators.

WHAT IS COMPOSTING?
Composting is the process by which microrganisms break down complex organic matter, such as your household kitchen waste into simple and useful nutrients for the soil.

WHY COMPOST? Composting helps to
-  recycle kitchen and garden waste and reduce the volume of waste going to landfills and incinerators
-  convert organic matter into a valuable resource for your plants or community garden. It acts as a soil conditioner, fertiliser, a natural pesticide, an adds to humus in the soil.
-  better the health of the soils. Compost breaks up clayey soil and improves their structure. In case of sandy soils, it enables water and nutrient retention. Healthier soils make for healthier plants
-  mulch when used to cover soil and deter the growth of weeds
-  even make some money, if there is a market for compost in your area

HOW TO COMPOST?
If you google for “how to compost”  the net will no doubt throw may different ways. Some websites recommend buying tumblers and special bins.  I’d like to share  a very simple method which works well for me, using resources I already have at home. Once you understand the broad concepts, you can choose your own containers, and experiment with your kitchen waste to suit the climate where you live and the kind of waste and volume of waste you wish to recycle.  Be bold and get started! You’ll learn a lot along the way as I did, and I’m sure you’ll discover that it’s a lot simpler than it sounds.

Composting using container/flower pots and soil

Things you’ll need :

*  Used flower pot (any material such as ceramic, terracotta or plastic)
* Soil (even degraded or old soil from your garden would do- if not you can get planting soil from the nursery)
*  A lid ( I use old metal plates or lids as they are waterproof, but used cardboard, old thick polyethene sheets or old rags of carpet would do to cover the pots)
*  A dish to keep below the pot for indoor composting
*  Kitchen waste (which we’ll talk about in “What to compost and What not to compost” )

1. Take any used flower pot with holes at the bottom for drainage and aeration. Put a layer of coconut husk (or other material like cork) that decomposes more slowly at the bottom to prevent too much moisture coming out of the pot. Cover with a layer of soil about 5 cm thick.

2. Put all your kitchen waste for the day over this soil.

3. Cover the waste well with soil :

4. You can start all over again with another layer of waste the next day

5. And repeat by completely covering with another layer of soil.  This will ensure there are minimal flies and smell. As you keep layering waste and soil alternately, you will have to stir the contents once or twice a week to ensure proper aeration.

6. Always keep the pot covered with a metal lid or thick cardboard or old rags of carpet. I tend to use metal because it’s waterproof and I can control the amount of moisture in the pot better when it’s exposed to sun and rain.

You may want to keep a series of pots and label them Pot 1, Pot 2, Pot 3 and Pot 4. As the first pot fills up, you can move on to the second, third and fourth. By the time the fourth is full, you’ll find that it has been 6-8 weeks in a tropical climate and the first pot is properly composted. Temperate climates may delay composting to about 3-6 months. Check the compost that is being made in the pots and remember to stir regularly once or twice a week.

Keep a dish under the pot to collect the excess moisture that will be released. This water is precious and can be used as fertiliser for plants.  If you’re keeping the pot outdoors directly on the grass, the water will directly go to the soil and fertilise it.

Those with larger garden space can dig a hole and do the same process. Keeping the compost pit covered is a good idea to keep away pests and flies.

WHAT DOES COMPOSTING REQUIRE?
Air – Stir once or twice a week as required. This method is aerobic composting as it requires air.  (The other method is anaerobic composting which is done in an airtight container). Lack of oxygen can lead to unpleasant smells.  You may most likely get harmless fruit flies in the bin, which again will disappear when you cover the food waste with soil and mix and aerate well. Also, a mix of soft and hard materials in the pile will enable better air circulation.

Moisture – if the composting mixture is too wet, it will get smelly and become prone to fungus and slime. Add more browns like shredded paper or cardboard to absorb the excess moisture, which will also help to creat air pockets

Heat – The compost itself will generate heat. You may keep the pot indoors or outdoors. I get better results outdoors, as there’s more external heat which helps decompose matter faster.

It helps to chop or shred the materials into smaller pieces so the decomposition takes place faster. Materials which take longer to decompose should ideally be placed at the bottom of the pile and in moderate quantities.

WHAT MAKES A GOOD COMPOST?

* It smells good, like the smell of soil and rain
* It is crumbly without lumps. If lumpy, you can sieve the compost, and use the fine residue. The lumps can be thrown into the new compost pot as a starter mixture.
* It isn’t too moist and doesn’t have any fungus or moss. It isn’t too dry either.

HOW TO USE COMPOST?
Compost is best used as a top layer around plants. I use my compost once in 6-8 weeks when the pot is done, by applying a two inch layer on the soil bed. The compost can be used directly on a garden bed or for container plants.  I’ve not explored if there’s an expiry date to the compost as my garden is always in need of new compost.

Greens are generally the wet and live matter which decompose quickly and give the required moisture to the compost. They contain and provide the nitrogen - proteins required for the microbes to digest and thrive. Without greens, the decomposition will take much longer, and the compost will become too dry.

* Vegetable and fruit peels
* Rotting Vegetable and Fruit Scraps (uncooked)
* Plant cuttings/Hedge clippings
* Grass Clippings (without the seed heads/roots)
* Tea Bags
* Coffee Grounds
* Crushed Egg Shells
* Flowers

Browns provides the carbon required for the microbes to multiply. Less carbon would make the compost smelly (due to rapidly fermenting nitrogen into ammonia), overly moist and fungus prone.

* Dried leaves
* Chopped straw and small twigs
* Shredded Paper (non-glossy)
* Coffee Filter Paper
* Cardboard (without the use of commercial glues like formaldehyde)
* Shredded Pizza boxes (remove the cooked food residues on the boxes to the extent possible)  * Dryer Lint
* Vacuum Cleaner Bag (contents should be sorted)
* Dryer Lint (provided most of the clothes are natural fabric)
* Corn Cobs (chopped into small pieces)
* Used Kitchen Paper
* Kitchen and Toilet Paper cardboard rolls
* Cotton Wool (non- contaminated)
* Sawdust (non-chemically treated)
* Hair (not as clumps, very slow to decompose)
* Shredded cotton or wool (in small quantities)

Browns that can be composted but prefer to send for recycling

* Newspaper – The paper itself will decompose, but newspaper ink can be laden with heavy metals. So unless you are sure that the ink is non-toxic or soy based, it is better not to add to the compost, especially if you want it to be organic
* Cardboard with lot of print- such as cereal boxes are full of ink like newspapers. So make sure the inks are non-toxic. If in doubt, send for recycling
* Cotton, silk, woollen clothing – due to sheer volume, it’s better to send for recycling where it can be made reused or recycled into other items

What’s a good Greens to Brown ratio?

The general rule of thumb is equal amounts of greens and browns should be put in the compost mixture. This will roughly enable a Carbon to Nitrogen ratio of 30:1 in the final compost which is recommended by most gardeners.

WHAT NOT TO COMPOST?

* Cooked foods (more on “What’s the matter with cooked foods?”  below)

Non- Biodegradable and Hazardous Waste which should not be put in the compost, but sent for recycling or for careful disposal :

* Plastics of all kind – bags, bottles, cling film, wrappers
* Drink cartons (as they are layered with plastic or tin foil)
* Styrofoam
* Glass, Porcelein, Ceramic
* Glossy paper, magazines (tend to have high chemical content in the inks and laminations)
* Metal including cans and foil paper and wrappers
* Leather (as they are treated with toxic chemicals)
* Rubber
* Cigarette butts
* e-waste
* Electrical items – bulbs, tube lights, batteries
* Oil waste – cooking oils, fats as in butter, margarine and fuel
* Wood ( is usually chemically treaded and will add heavy metal content to the soil)
* Paints

What’s the matter with cooked food?

You may ask, doesn’t cooked food biodegrade? Yes it does but it is likely to cause problems in the compost. For one, it can smell really bad when the food starts decomposing, especially if you add meat or fish. It may also attract vermins and pests.

However, by using the right composting system (such as one that we will show in Part 2 of this blogpost) you should be able to compost cooked food as well. You may also use the above flower pots method, but you will have to use some kind of culture to accelerate the decomposition of cooked foods so one can avoid smells.

How to make or get accelerators or Biocultures?

Biocultures are not required with the above method, but with cooked foods it is necessary to accelerate the decomposition.

1. You could ask for “Bokashi” at the nursery. Bokashi is a bran containing yeast, fungi and bacteria which ferments cooked food, especially meat and fish in a few days time, without risking pests or flies. Here’s an E-how instruction showing how to make some at home.

2. Another Bio culture recipe that can be made at home is E-how’s How to make active compost microbes (using rice wash and milk to obtain lactobaccillus serum)

3. I have seen organic farmers in India use diluted cow dung (5% dilution in water) over their compost for a similar purpose.

I’ve yet to try these three methods mentioned above for cooked food. If you have had some success with composting cooked foods, do share them with us.

Hope to hear from you about your experiences, comments and queries on the topic. Wish you success in the journey of turning kitchen garbage into riches for your garden! Happy composting!

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Credits: I learnt this method of composting from the article by Zhou Miao-Fei in the Singapore newletter “Lapis News” July-September 2009 edition as translated from Mandarin into English by my friend, Ruyu Gan, a permaculturist.

Further links:

For the many benefits of composting, here’s a very informative article from Permaculture Research Institute of Australia entitled, ” Compost Miracles“ which has found that “Compost microorganisms not only convert organic material into humus, but they also degrade toxic chemicals into simpler, benign, organic molecules. These chemicals include gasoline, diesel fuel, jet fuel, oil, grease, wood preservatives, PCBs, coal gasification wastes, refinery wastes, insecticides, herbicides, TNT, and other explosives.”

This is heartening to read, but would suggest avoiding this in your home compost!! Nevertheless, a very insightful piece.

Read Excerpts from a wonderful book called “The Rodale Book of Composting”

EWTT: Part 2: How to compost at home: Using the Daily Dump

EWTT: Poonam Bir Kasturi: Designing the Daily Dump

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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

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:

• American Society for Testing and Materials ASTM-6400-99
• European Standardization Committee (CEN)  EN13432
• International Standards Organization (ISO)   ISO14855 (only for biodegradation)
• German Institute for Standardization (DIN)  DIN V49000

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

These are the ASTM D6400 and EN 13432 logos  to look out for:

3. Is it suitable for home composting?

If 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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