BIODEGRADABLE MATERIALS

"Ashwin, put all biodegradable garbage in one bin and all plastics in the other"Mother said.

"What is biodegradable, Ma? " asked 10 year old Ashwin.

"A "biodegradable" product has the ability to decompose or break down, safely and relatively quickly, by biological means, into the raw materials of nature like carbon dioxide and water that disappear into the environment. Actually, decomposition is a biochemical process by which bacteria, fungi, earthworms, springtails, mites and other microscopic organisms break organic "wastes" into nutrients that can be used by plants and animals. Like, peels of vegetables and fruits, tea leaves, squeezed tamarind, leaves of our plants, paper, cloth etc., get decomposed and change to compost. Try putting some carrot peels into a pot, after a few days you will see it transformed into soil. What caused this transformation ? May be some earthworms or some insects or some bacteria have eaten them. This completes a cycle. We have a saying "what comes out of earth goes back into it" replied mother.

Ashwin was amused, he separated the garbage and gave it to the garbage collector. He went into a deep thought. He started thinking of all the biodegradable things. He remembered that teacher has told not to use the plastic bag for shopping. It means something is wrong with them. One can see them scattered here and there. If they were biodegradable, then they would have been eaten by some organism. He has seen wood being eaten by termites and leaves vanishing into soil. Suddenly the bell rang and when he opened the door, it was his cousin Shashi akka, who is doing research in Ecology.

Ashwin started telling her about what he was thinking about biodegradable items. Then Shashi akka added some more information to it. She said "There are solid biodegradable materials that can be composted and liquid biodegradable materials that can decompose in water. Biodegradable plastic is intended to break up when exposed to microorganisms. Healthy soil and water will have microorganisms like bacteria, fungi etc. and earthworms to do this job"

Ashwin "But, why should we separate the garbage, Shashi akka? "

"Disposal of any product requires that it returns to the earth and are able to biodegrade. Nature breaks down or biodegrades everything it makes, back into basic building blocks, so that new living things can be made from the old. Every thing that comes from nature returns to nature. Plants and animals biodegrade, even raw crude oil will degrade when exposed to water, air, and the necessary
salts. Nature has perfected this system. We just need to learn how to participate in it. " Said Shashi

"But plastics are non- biodegradable items, isn't it Akka?" Aswin started understanding a bit.

Shashi Akka said "Well, yes and no. By the time many natural resources are turned into products, however, they have been altered by industry in such a way that they are unrecognizable to the microorganisms that work on them. Crude oil, for example, will biodegrade in its natural state, but once it is turned into plastic, it becomes a big pollution problem. Instead of returning to the cycle of life, these products simply pollute and litter our land, air, and water."

Ashwin was thoroughly puzzled as he was very sure that plastics are non-biodegradable, but as Shashiakka said the plastics in its initial stage were biodegradable. He asked "Then why do we say that some things are biodegradable and some are not?"

"Of all the environmental buzzwords, "biodegradable" has perhaps been the most misused and is perhaps the most difficult to understand. Because in the past, there have been no guidelines or regulations, many products were called biodegradable without any real justification. Unfortunately, the word biodegradable has frequently been applied to products that generally are not (such as detergents or plastics) and almost never used for products that really are (such as soap or paper)" Shashi said.

Shashi continuing with her talk "A leaf is a perfect example of a biodegradable product: it sprouts in the spring, used by the plant for photosynthesis in the summer, drops to the ground in the autumn, and gets assimilated into the soil to nourish the plant for the next season. Any material that comes from nature will return to nature, as long as it is still in a relatively natural form. Therefore any plant-based, animal-based, or natural mineral-based products have the capability to biodegrade. But many products made by industrial processes generally do not. Man-made compounds have combinations of elements that do not exist in nature, and there are no corresponding microorganisms to break them down."

Understanding a bit, Ashwin asked "How much time does it takes to naturally break down an item, Akka?"

Akka said "Yes, I am coming to that. In nature, different materials biodegrade at different rates. A leaf takes approximately a year to become part of the forest floor. An iron shovel, on the other hand can take years to rust away, and a large tree can take decades to completely break down. Common sense tells us that any material will ultimately biodegrade, even if it takes centuries”.

"So what is the proper rate for a material to be called biodegradable?"

"It really depends on the material itself. The example of leaf suggests that the proper rate is that which is appropriate to the ecosystem. A liquid going into a waterway should biodegrade fairly quickly, whereas there is less harm if it takes a while for a newspaper to break down. Plastics, on the other hand, will not biodegrade in anyone's lifetime" replied Akka (See the box for the life times of various products).

"And then there is the question of what exactly does the product or material breaks down into, and are there any toxic substances formed along the way or as the end result. Right?" queried Ashwin.

"Good question, Ashwin." said Shashi Akka "There is this example of a benzene unit in synthetic detergents biodegrading into phenol (carbolic acid), a substance toxic to fish. To be truly biodegradable, a substance or material should break down into carbon dioxide (a nutrient for plants), water, and naturally occurring minerals that do not cause harm to the ecosystem (salt or baking soda, for example, are already in their natural mineral state and do not need to biodegrade).

The characteristics of the environment that the substance or material is in can also affect its ability to biodegrade. Detergents, for example, might break down in a natural freshwater "aerobic" (having oxygen) environment, but not in an "anaerobic" (lacking oxygen) environment such as sewage treatment plant digestors, or natural ecosystems such as swamps, flooded soils, or surface water sediments."

“What is meant by compost process?”

The compost process is the aerobic decomposition of organic waste through micro-organisms in a controlled setting. These micro-organisms are bacterium, yeast and fungi. This process transforms complex organic substances in to carbon dioxide, water and humus (compost). Composting is nature's own recycling program!

Shashi Akka continued saying "But can you imagine Ashwin, that many products which are inherently biodegradable in soil, such as tree trimmings, food wastes, and paper will not biodegrade when we place them in landfills because the artificial landfill environment lacks the light, water, and bacterial activity required for the decay process to begin. A garbage project, has unearthed newspapers dating back to 1952 that were still easily readable. When the conditions needed for biodegradable materials to naturally biodegrade are not provided, major garbage problems are the result. "

Distrupting Shashi akka, Ashwin said "Now I understand how fossils are formed "

Shashi akka said "That is a different matter, Ashwin, I will tell you about them some other time. Soap, for example, is a natural, organic product that is inherently biodegradable. The soapy water from a single household may biodegrade easily in the backyard. However, if that same soap went down a sewage line that fed into a river along with the soap used by a million or more residents that live along that waterway, there may be waves of soapsuds on the shores. This is due to more soap going into the waterway than the microorganisms can biodegrade."

Ashwin’s mother came out of kitchen bringing some snacks and coffee saying "It is quite interesting Shashi, that I can put all my washing water in to the garden and save on water."

Sipping coffee Shashi said "That is true auntie. That is what our ancestors used to do and they had a better and healthy environment"

Here's how long it takes for some of our commonly used products to biodegrade, when they are scattered about as litter:

-Dr.Vijaya Shukre

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