Biodegradable Definition
A “biodegradable” product has the ability to break down, safely and
relatively quickly, by biological means, into the raw materials of
nature and disappear into the environment.
These products can be solids biodegrading into the soil
(which we also refer to as compostable), or liquids biodegrading
into water.
Biodegradable plastic is intended to break up when exposed to
microorganisms (a natural ingredient such as cornstarch or vegetable
oil is added to achieve this result).
Sustainable disposal of any product requires that its wastes return
to the earth and are able to biodegrade.
Nature biodegrades everything it makes back into basic
building blocks, so that new living things can be made from the old.
Every resource made by 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.
By the time many resources are turned into products, however, they
have been altered by industry in such a way that they are
unrecognizable to the microorganisms and enzymes that return natural
materials to their basic building blocks.
Crude oil, for example, will biodegrade in its natural state,
but once it is turned into plastic, it becomes an unsustainable
pollution problem.
Instead of returning to the cycle of life, these products simply
pollute and litter our land, air and water.
Of all the environmental buzzwords “biodegradable” has perhaps been
the most misused and the most difficult to understand.
Because in the past there have been no guidelines or
regulations, many products have called themselves biodegradable
without any real justification.
Unfortunately, the word biodegradable has frequently been
applied to products that generally aren’t (such as detergents or
plastics) and almost never used for products that really are (such
as soap or paper).
A leaf is a perfect example of a biodegradable product -- it is made
in the spring, used by the plant for photosynthesis in the summer,
drops to the ground in autumn and assimilated into the soil to
nourish the plant for the next season.
The basic concept seems straightforward enough, however,
there are several factors to consider in determining the
biodegradability of a product or material.
The first is the question of the inherent biodegradability of the
material. 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 product has the capability to biodegrade, but products
made from man-made petrochemical compounds generally do not.
When a manmade compound is formulated in a laboratory,
combinations of elements are made that do not exist in nature and
there are no corresponding microorganisms to break them down.
The next issue is how long it takes for the material to actually
break down. 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 to nothing
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 biodegradable?
It really depends on the material itself.
The leaf example 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’s no harm done if it
takes a while for a newspaper to break down.
Plastics, on the other hand, will not biodegrade in anyone’s
lifetime and certainly will never break back down into the petroleum
from which it is made.
And then there is the question of what exactly does the product or
material break down into and are there any toxic substances formed
along the way or as the end result.
In his book The Closing Circle, ecologist Barry
Commoner gives the example of the benzene unit in synthetic
detergents being converted as it biodegrades 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 a
“anaerobic” (lacking oxygen) environment such as sewage treatment
plant digestors, or natural ecosystems such as swamps, flooded soils
or surface water sediments.
Many products that 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. The
Garbage Project, an anthropological study of our waste conducted by
a group at the
Soap, for example, is a natural organic product that is inherently
biodegradable. The
soapy greywater from a single household may biodegrade easily in a
backyard, however, if that same soap went down a sewage line that
fed into a waterway along with the soap used by a million or more
residents that live along that waterway, there may be waves of
soapsuds on the beaches, simply because more soap would be going
into the waterway than it has microorganisms to biodegrade.
Oil spills are devastating not because oil doesn’t biodegrade, but
rather because the amount of oil is much greater than the number of
microorganisms available to degrade it.
It has been estimated that it will take 50 years for the oil
spilled in 1989 by the Exxon Valdez to degrade.
Lakes and streams have become polluted because the amount of
sewage dumped into them has been overwhelming.
As much as we need to consider the biodegradability of the
product, we need to consider the capacity of the system the
biodegradable substance or material is being placed into.
Those who have attempted to define biodegradable for product labels
run into the same dilemma encountered when defining recyclable --
should a product be called biodegradable if it inherently has the
ability to biodegrade, or should it only be called biodegradable if
it also is commonly disposed of in a way in which it really will
biodegrade? For
example, should a paper grocery bag be labeled biodegradable?
It will biodegrade if placed in nature, however, it won’t
biodegrade in a landfill because the conditions aren’t right.
Here’s how long it takes for some commonly used products to
biodegrade when they are scattered about as litter:
|
1-5 months |
|
| Paper |
2-5 months |
| Rope |
3-14 months |
|
6 months |
|
| Wool socks |
1 to 5 years |
| Cigarette butts |
1 to 12 years |
|
Plastic coated paper |
5 years |
| Leather shoes |
25 to 40 years |
| Nylon fabric |
30 to 40 years |
| Plastic 6-pack holder Rings |
450 years |
| Glass bottles |
1 million years |
| Plastic bottles |
Forever |