As concerns increase about plastic pollution—especially from single-use plastics—bioplastics are garnering interest for their potential role in the development of a circular economy for plastics. Bioplastics, which are made with organic, plant-based resources, are viewed as an important alternative to fossil-produced plastics as a significant means of reducing the influx of conventional plastics. Yet, bioplastics also face limitations in terms of functionality and cost compared to their conventional counterparts.
Given the “bio” in its name, bioplastics can give the impression that they are always all-natural or biodegradable when this is not necessarily true.
To learn more about the characteristics and properties of bioplastics, The Earth & I spoke with Tanya Hart, founder and CEO of Titan Bioplastics, a Seattle-based engineering company that focuses on recycled plastics and (plant-based) bioplastic composites suitable for industrial, energy, military, and commercial retail use.
Bioplastics and ‘Augie Bones’
Titan Bioplastics makes a product that millions of households can relate to—a biobased and biodegradable dog chew toy trademarked Augie Bones. On its website, the company explains that “Our dog Augie was chewing all sorts of [plastic] bones and chew toys, leaving chords of plastic everywhere.” None of those plastics could be recycled since many of the toys were blends of nylon and plastics; plus there were potential health risks for Augie and other dogs “from constantly swallowing the bits off the toys.”
Titan Bioplastics says it found “a better material that was both healthy for our dogs and the planet,” and launched Augie Bones chew toys that contain no nylon or traditional plastics. In fact, if dogs bury an Augie Bone, “it will compost,” the website says.
Background on Bioplastics
Plastics can be generated from either bio-based feedstock, such as plant starches and oils, or fossil-based feedstock, often referred to as “fossil fuels.” Additionally, plastics are classified as either biodegradable or non-biodegradable. It is these four criteria: bio-based, fossil-based, biodegradable, and non-biodegradable, by which plastics are categorized. Conventional plastics are always both fossil-based and non-biodegradable. Bioplastics, on the other hand, are more diverse: they are either bio-based, or biodegradable, or both. However, it’s important to note that some bioplastics can be bio-based but non-biodegradable, or conversely, fossil-based but bio-degradable. Hence, the “bio” in bioplastics refers to “bio-based” or “biodegradable.”
“However, it’s important to note that some bioplastics can be bio-based but non-biodegradable, or conversely, fossil-based but bio-degradable. Hence, the 'bio' in bioplastics refers to ‘bio-based’ or ‘biodegradable’.”
Defining bioplastics is further complicated by the term, “biodegradability,” which typically adheres to industrial standards with conditions not always present in residential or natural settings; exceptions would include specific products that are certified compostable in residential settings, such as those with TÜV Austria’s OK compost HOME certification.
Properties of Bioplastics
Like conventional plastics, bioplastics are manufactured and tailored to suit their specific applications.
“We provide customized composites with plant-based materials and recycled plastics,” Hart says. “Most companies we work with require the materials we develop be ‘fitted’ or customized to existing equipment for a commercial purpose or product. In other words, we don’t have a one-size-fits-all material or product.”
Bioplastics that are biobased and biodegradable include PLA (polylactic acid), PHAs (polyhydroxyalkanoates), and PBS (polybutylene succinate).
PLA is made from lactic acid, which is typically derived from starch, cellulose, kitchen waste, and fish waste. It is considered more environmentally friendly given how it can degrade into carbon dioxide, water, and lactic acid chains. Other advantages include its transparency, biocompatibility, and thermoplasticity, but it also has low toughness and high production costs.
PHAs are notable for being derived from fermentation of renewable feedstocks like sugars or plant oils. Aside from having thermoplasticity and good insulation, they have various medical applications given their biocompatibility with human bones and tissues.
PBS is a polyester traditionally produced from petrochemicals but can also be made from renewable resources such as sugarcane, cassava, and corn with fermentation. It has good mechanical properties and thermal stability, with applications in textile filaments, injection molds, and film production, being comparable to LDPE, HDPE, and PP.
Advantages and Disadvantages of Bioplastics
Aside from their biodegradability, bioplastics can have a lower carbon footprint and advantageous properties over conventional plastics. They also can have lower greenhouse gas emissions; for example, a 2017 study indicated that replacing conventional plastic with corn-based PLA could see a 25% reduction in greenhouse gas emissions from plastic production in the US.
General disadvantages of bioplastics include their sensitivity to heat, humidity, and shear stress. They also face other challenges such as limited ability to replace conventional plastics, higher production costs, and supply chain restrictions over conventional plastic. Additional drawbacks include adverse agricultural impacts, competition with food production (such as corn), and unclear “end-of-life” (EOL) management.
“[Bioplastics] also face other challenges such as limited ability to replace conventional plastics, higher production costs, ... supply chain restrictions over conventional plastic[,] ... adverse agricultural impacts, competition with food production ... , and unclear 'end-of-life' (EOL) management.”
In a 2010 study, seven conventional plastics were compared to four bioplastics and one plastic produced from a mixture of fossil fuels and recycled sources. The bioplastics generated pollutants due to the fertilizers and pesticides applied to the feedstocks and the chemical processing involved in converting organic material into plastic. The bioplastics also contributed to greater ozone depletion and required a larger area of land for production. A 2020 study assessed the in vitro toxicity of various bioplastics, including Bio-PE, Bio-PET, PBAT, PBS, PLA, PHA, and bamboo-based materials. Higher in vitro toxicity measurements were found in the bioplastics than in their respective original raw materials.
The lack of sufficient industrial composting facilities is another issue. Most bioplastics are disposed of in landfill sites because very few cities have the necessary high temperature industrial composting sites. Once in a landfill, PHA, for example, can decompose into methane, which absorbs more heat but lasts shorter than CO2 in the atmosphere.
Research Underway in Bioplastics
Some researchers are investigating the use of microorganisms in bioplastic production. A 2020 study found that bioplastics can be produced using microalgae obtained from wastewater, and there is research on producing PHB from microalgal biomass.
There is also research into using organic chemicals in bioplastic production. Biome Bioplastics partnered with the University of Warwick’s Centre for Industrial Biotechnology and Biorefining to extract organic chemicals from lignin (from cell walls in plants) that potentially can be used for bioplastic manufacture. Initial trials on these chemicals have shown that they could be produced at an industrial scale. The company is also examining how bacteria can help increase the yields of the chemicals and how they can be scaled up.
In 2021, researchers at University of California, Berkeley, discovered a method of making biodegradable plastics break down more easily with heat and water over the course of a few weeks. With the addition of an enzyme, PLA plastic can biodegrade into simple molecules, thereby making it a potentially suitable replacement for non-degradable plastic. This process is also suitable for municipal composting over a period of 60 to 90 days. Degradation can also be achieved by soaking in lukewarm water.
Bioplastics in the Real World
A startup in Australia called Pak360 is focusing on compostable packaging, manufactured from renewable fibers. Bioplastic products include compostable garbage bags and produce bags made from PLA, corn starch, and PBAT.
A French startup, Lys Packaging, manufactures bioplastic bottles using plant-derived biopolymers and a 3D printing and injection stretch blow molding (ISBM) process. It adds organic or vegetable products into the bioplastic in order to vary the products’ technical and visual properties.
Steps Toward Replacing Virgin Plastics
Although bioplastics are not a complete solution, they can decrease the production of conventional, virgin plastics—including single-use products—that end up accumulating in the environment. Bioplastics may become more accessible once their production costs drop and an infrastructure is built to support industrial composting and recycling.
“When using bioplastics and recycled plastics, the goal is always to inhibit the need for more virgin plastics. Recycled plastics have a bad rap; however, if we are reusing a resource that will prevent the further production of virgin plastic, that will make a large environmental impact in the long run.”
“When using bioplastics and recycled plastics, the goal is always to inhibit the need for more virgin plastics. Recycled plastics have a bad rap; however, if we are reusing a resource that will prevent the further production of virgin plastic, that will make a large environmental impact in the long run,” Hart says.
“Same for bioplastics,” she adds. “Biodegradable and recyclable bioplastics will evolve to become more prevalent once there is a greater infrastructure to support more industrial composting and recycling facilities. Science around sustainable materials is more prolific than the availability of these facilities. This, and a greater pipeline of biomaterials at a competitive price point.”
*Robin Whitlock is an England-based freelance journalist specializing in environmental issues, climate change, and renewable energy, with a variety of other professional interests, including green transportation.