Does being biodegradable make a pollutant less of an environmental hazard?

Replacing nonbiodegradable materials with biodegradable substances can help decrease the environmental footprint, but simply changing from nonbiodegradable to biodegradable doesn't automatically "fix" pollution problems.

Merriam-Webster defines biodegradable as "capable of being broken down especially into innocuous products by the action of living things (such as microorganisms)." Cambridge English Dictionary states that biodegradable means "able to decay naturally and without harming the environment." Biodegradable materials may also be referred to as degradable materials, but degradable also refers to substances that break down without the help of decomposing bacteria and fungi.

Merriam-Webster defines nonbiodegradable as "not capable of being broken down by the action of living organisms: not biodegradable." Cambridge English Dictionary does not define nonbiodegradable, but the prefix non- adds the meaning "not" to words, so nonbiodegradable becomes not "able to decay naturally and without harming the environment". Non-degradable is an alternate spelling for nonbiodegradable.

Three broad categories of biodegradable pollutants are human and animal waste, plant products (like wood, paper, food waste, leaves and grass clippings) and bodies and body parts of dead organisms.

Other biodegradable examples include plant-based plastics, some oil and petroleum products, certain heavy metals and chemicals. Bioremediation using plants or bacteria is a technique used to clean some contaminants in water and soil.

Types of recyclable nonbiodegradable pollutants include glass, metals (like aluminum and steel), petroleum (including coal and gas) plastics and electronics. Medical waste, radioactive materials, many heavy metals and chemicals including fertilizers, pesticides, petroleum products and mining waste are difficult to biodegrade and generally not recycled.

Plastics have become seemingly indispensable in the modern world. Most plastic materials are made from petroleum, coal and gas. All of these are nonrenewable resources, but only about 9 percent of plastic materials are recycled.

About 150 million metric tons of plastic already float in the ocean, with an estimated 40 percent of the ocean's surface covered with plastic debris. Much of this debris consists of tiny bits and remnants of plastic. In landfills, plastic bags and water bottles can last hundreds of years. Plastic milk jugs last an estimated 500 years.

Point source pollution comes from a defined and accessible source. Non-point source pollution, often resulting from runoff from yards, streets and fields, is much more difficult to capture and treat.

Non-point source pollution includes animal waste, fertilizers, pesticides and petroleum products like oil and gasoline that wash into storm drains, creeks, lakes and the ocean.

Animal Waste, Remains and Fertilizers

Non-point source pollutants like animal waste, animal remains and fertilizers carry bacteria, including pathogens (disease-causing bacteria) into waterways. These bacteria can cause a variety of diseases including cholera, giardia and typhoid fever. In 2015 an estimated 1.8 million people died due to contaminated water.

Worldwide, approximately 1 billion people become sick due to contaminated water each year and in the U.S. an estimated 3.5 million people develop pink eye, respiratory issues, hepatitis or skin rashes due to sewage-contaminated coastal waters.

Animal waste, animal remains and fertilizers also impact the environment by providing nutrients to algae. Too many algae consume the oxygen in the water, killing many fish and other aquatic organisms. These algal blooms may also release toxins that affect fish, whales and humans. Lack of dissolved oxygen has created a dead zone of more than 7,700 square miles in the Gulf of Mexico.

Plant Products

One serious environmental issue with decomposing plant materials is methane. Methane released directly from decomposing plant materials and animal waste, as in stockyards, becomes a serious environmental hazard.

Methane traps 25 times more heat in the atmosphere than carbon dioxide, making methane a more damaging greenhouse gas than carbon dioxide. Methane from decomposing trash in landfills can be captured and used as fuel, but only where gas collecting systems are installed.

Biodegradable Plastics

Bioplastics, plastics made from plant materials, come in three types: degradable, biodegradable and compostable. All plastics degrade, meaning they break down into smaller and smaller pieces. The environmental damage of these particles is becoming increasingly evident.

Biodegradable plastics can be broken completely down by microorganisms, decomposing into water, carbon dioxide and compost. Compostable plastics decompose in compost piles, breaking down into nontoxic water, carbon dioxide, inorganic compounds and biomass.

Bioplastic production, however, creates its own set of environmental issues. Pollution from corn production in the form of fertilizers and pesticides, extensive land use to grow corn, toxic chemicals from the production process, ozone depletion and methane emissions if the bioplastics end up in landfills.

In addition, bioplastics cannot be recycled with petroleum-based plastics. Recycling most bioplastics requires high temperature industrial composters, equipment most cities don't have, at least not yet.