Bioplastics are a category of plastics made from renewable biomass sources instead of traditional petroleum. The core idea is to create polymers using biological substances as the foundational components, representing a shift away from finite fossil fuels. This approach contrasts with conventional plastics, which are derived from petroleum or natural gas.
What Are Bioplastics Made From?
A significant portion of current bioplastics are derived from agricultural crops rich in carbohydrates. Corn starch is a prevalent feedstock, where its glucose is fermented to create the plastic’s building blocks. Sugarcane and sugar beets provide sucrose for plastic production, and potato starch also serves as a source material. Cellulose, a structural polymer in plant cell walls, is another feedstock from wood pulp and cotton linters used for materials like cellophane and cellulose acetate. These first-generation feedstocks are sourced from crops that could also be used for food, which has prompted research into other sources.
Researchers are focused on next-generation feedstocks that do not divert food resources. Algae is a promising source, as it can be cultivated on non-arable land and in marine environments. Agricultural waste, such as straw and wood chips, along with food waste, are also being developed as valuable sources for bioplastic production.
Types of Bioplastics
The term “bioplastic” encompasses materials with different properties. The two main categories are “bio-based” and “biodegradable,” and these terms are not interchangeable; a bioplastic can be one, the other, or both.
A “bio-based” plastic is made in whole or part from renewable biomass. An example is bio-polyethylene terephthalate (bio-PET), which can be derived from sugarcane ethanol. Although its origin is biological, bio-PET is structurally identical to its petroleum-based counterpart and is not biodegradable. Similarly, bio-polyethylene (bio-PE) is produced from sugarcane but retains the non-biodegradable nature of conventional polyethylene.
“Biodegradable” refers to a plastic’s ability to be broken down by microorganisms into natural substances like water and carbon dioxide under specific conditions. Polylactic Acid (PLA) is a well-known example of a bioplastic that is both bio-based and biodegradable, made from fermented plant starch from corn or sugarcane. Polyhydroxyalkanoates (PHAs) are another type, produced by bacteria, that are also both bio-based and biodegradable.
The Environmental Lifecycle
The environmental impact of bioplastics is complex. The production of first-generation bioplastics relies on agriculture, where growing crops like corn and sugarcane requires land, water, and fertilizers. These agricultural demands can compete with food production and contribute to habitat loss if not managed sustainably.
The end-of-life stage for bioplastics also presents challenges. For biodegradable plastics like PLA, decomposition requires the specific conditions found in industrial composting facilities. These materials do not readily break down in a backyard compost pile or in marine environments. If sent to a landfill, they can undergo anaerobic decomposition, a process without oxygen that releases methane, a potent greenhouse gas.
Recycling bioplastics also poses difficulties. Because their chemical compositions differ from conventional plastics, they can contaminate recycling streams if mixed in. A PLA bottle mixed with PET plastic, for example, reduces the quality of the recycled PET. This necessitates separate collection systems, which are not widely available, so many bioplastics end up in landfills or incinerators.
Common Applications
One of the most widespread uses for bioplastics is in single-use disposable items where biodegradability is an attractive feature. This includes food packaging, such as containers, clamshells, and films, as well as disposable cutlery, straws, and coffee cup lids, often made from PLA.
Beyond packaging, these materials are finding use in more durable goods. In the automotive industry, bioplastics are used to manufacture interior components like dashboards, door panels, and seat fabrics. Consumer electronics companies incorporate bioplastics into casings for phones and laptops. Agriculture utilizes bioplastics for applications like mulch films that can be tilled into the soil after use, and for pots that biodegrade once planted.
The medical field represents a specialized area for bioplastic applications. Because some bioplastics are biocompatible, meaning they do not produce a toxic or immunological response in the body, they are suitable for medical implants. Biodegradable sutures that dissolve over time eliminate the need for removal. These materials are also used in bone plates, screws, and drug delivery systems that release medication as the polymer breaks down.