Bio-Plastics

Bioplastics are often touted as being eco-friendly, but do they live up to the hype?

The world has produced over nine billion tons of plastic since the 1950s. 165 million tons of it have trashed our ocean, with almost 9 million more tons entering the oceans each year. Since only about 9 percent of plastic gets recycled, much of the rest pollutes the environment or sits in landfills, where it can take up to 500 years to decompose while leaching toxic chemicals into the ground.

Traditional plastic is made from petroleum-based raw materials. Some say bioplastics—made from 20 percent or more of renewable materials—could be the solution to plastic pollution. The often-cited advantages of bioplastic are reduced use of fossil fuel resources, a smaller carbon footprint, and faster decomposition. Bioplastic is also less toxic and does not contain bisphenol A (BPA), a hormone disrupter that is often found in traditional plastics.

Kartik Chandran, a professor in the Earth and Environmental Engineering Department at Columbia University who is working on bioplastics, believes that compared to traditional plastics, “bioplastics are a significant improvement.”

However, it turns out that bioplastics are not yet the silver bullet to our plastic problem.

How Biodegradable are Bioplastics?

Since there is often confusion when talking about bioplastics, let’s clarify some terms first.

Degradable – All plastic is degradable, even traditional plastic, but just because it can be broken down into tiny fragments or powder does not mean the materials will ever return to nature. Some additives to traditional plastics make them degrade more quickly. Photodegradable plastic breaks down more readily in sunlight; oxo-degradable plastic disintegrates more quickly when exposed to heat and light.

Biodegradable – Biodegradable plastic can be broken down completely into water, carbon dioxide and compost by microorganisms under the right conditions. “Biodegradable” implies that the decomposition happens in weeks to months. Bioplastics that don’t biodegrade that quickly are called “durable,” and some bioplastics made from biomass that cannot easily be broken down by microorganisms are considered non-biodegradable.

Types of Bioplastic

Bioplastics are currently used in disposable items like packaging, containers, straws, bags and bottles, and in non-disposable carpet, plastic piping, phone casings, 3D printing, car insulation and medical implants. The global bioplastic market is projected to grow from $17 billion this year to almost $44 billion in 2022.

There are two main types of bioplastics.

PLA (polylactic acid) is typically made from the sugars in corn starch, cassava or sugarcane. It is biodegradable, carbon-neutral and edible. To transform corn into plastic, corn kernels are immersed in sulfur dioxide and hot water, where its components break down into starch, protein, and fiber. The kernels are then ground and the corn oil is separated from the starch. The starch is comprised of long chains of carbon molecules, similar to the carbon chains in plastic from fossil fuels. Some citric acids are mixed in to form a long-chain polymer (a large molecule consisting of repeating smaller units) that is the building block for plastic. PLA can look and behave like polyethylene (used in plastic films, packing and bottles), polystyrene (Styrofoam and plastic cutlery) or polypropylene (packaging, auto parts, textiles). Minnesota-based NatureWorks is one of the largest companies producing PLA under the brand name Ingeo.

PHA (polyhydroxyalkanoate) is made by microorganisms, sometimes genetically engineered, that produce plastic from organic materials. The microbes are deprived of nutrients like nitrogen, oxygen and phosphorus, but given high levels of carbon. They produce PHA as carbon reserves, which they store in granules until they have more of the other nutrients they need to grow and reproduce. Companies can then harvest the microbe-made PHA, which has a chemical structure similar to that of traditional plastics. Because it is biodegradable and will not harm living tissue, PHA is often used for medical applications such as sutures, slings, bone plates and skin substitutes; it is also used for single-use food packaging.