Are cigarette butts biodegradable?
Most cigarette filters are composed of cellulose acetate, a form of plastic. The white fibers you see in a cigarette filter are NOT cotton, but a plastic that can persist in the environment as long as other forms of plastic. The following article reviews what is known about degradation mechanisms of cellulose acetate.
Degradation of Cellulose Acetate-Based Materials: A Review.
Cellulose acetate polymer is used to make a variety of consumer products including textiles, plastic films, and cigarette filters. A review of degradation mechanisms, and the possible approaches to diminish the environmental persistence of these materials, will clarify the current and potential degradation rates of these products after disposal. Various studies have been conducted on the biodegradability of cellulose acetate, but no review has been compiled which includes biological, chemical, and photo chemical degradation mechanisms. Cellulose acetate is prepared by acetylating cellulose, the most abundant natural polymer. Cellulose is readily biodegraded by organisms that utilize cellulase enzymes, but due to the additional acetyl groups cellulose acetate requires the presence of esterases for the first step in biodegradation. Once partial deacetylation has been accomplished either by enzymes, or by partial chemical hydrolysis, the polymer’s cellulose backbone is readily biodegraded. Cellulose acetate is photo chemically degraded by UV wavelengths shorter than 280 nm, but has limited photo degradability in sunlight due to the lack of chromophores for absorbing ultraviolet light. Photo degradability can be significantly enhanced by the addition of titanium dioxide, which is used as a whitening agent in many consumer products. Photo degradation with TiO2 causes surface pitting, thus increasing a material’s surface area which enhances biodegradation. The combination of both photo and biodegradation allows a synergy that enhances the overall degradation rate. The physical design of a consumer product can also facilitate enhanced degradation rate, since rates are highly influenced by the exposure to environmental conditions. The patent literature contains an abundance of ideas for designing consumer products that are less persistent in the outdoors environment, and this review will include insights into enhanced degradability designs.
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So how long do cigarette butts take to degrade? Various sources have stated that cigarette filters take 18 months to 10 years to degrade. It is safe to say that the cellulose acetate fibers in cigarette filters, like other plastics, are with us for some time after they are discarded. Since environments differsome places are wetter, dryer, sunnier, colder, hotter, windy, etc.so too will the degrading time differ. A cigarette butt that is littered in a dry sunny place will degrade differently than one that is littered into a river or on a sandy beach.
But even if cigarette filters were quick to degrade, we would still have fires caused by lit cigarette butts, and the toxins found in cigarette butts would still be harmful. That is why Clean Virginia Waterways believes the best way to decrease cigarette butt litter is to educate smokers, rather than try to make filters biodegradable.
What do we mean by "biodegradable?"
When we say "biodegrade," we are saying that something living, for example, bacteria, is responsible for "degrading" an item. There are many methods, however, that lead to something being "degraded." Sunlight, for example, can degrade some things. For example, sunlight can make some plastics brittle. Studies done on plastics in the oceans show that most plastics are broken-down by the UV waves of sunlight. Wind and water can cause erosion which is a form of degradation. Freezing and thawing can also physically change and breakdown items.
Degradable: susceptible to chemical breakdown.
Degrade: to break down a compound; to become degraded, weakened, deteriorate, to decompose.
Biodegradable: capable of decaying through the action of living organisms.
Photodegradable: capable of being broken down by light.
Photodecomposition: The breaking down of molecules by radiant energy.
Definitions from the Random House Dictionary, 2nd edition, Unabridged.
Click here for newspaper articles about how communities are trying to reduce cigarette litter.
Read all about cigarette butt litter!
Click here to read an article that was published in the August 2000 issue of the American Littoral Society journal, The Underwater Naturalist. This article, by CVW's Executive Director Kathleen M. Register, includes background data, such as the fact that 2.1 billion pounds of cigarette filters were discarded worldwide in 1998, along with results of her research showing that leached chemicals from cigarette filters are deadly to the water flea Daphnia magna, a small crustacean at the lower end of, but important to the aquatic food chain.
Students and Teachers:
Are you interested in doing a science fair project on cigarette litter? Click here for ideas and information.
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Compiled by Clean Virginia Waterways, Longwood University, Farmville, VA 23909
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