No fully sustainable bio-based plastics currently exist

There are no bio-based plastics currently in commercial use or under development that are fully sustainable, according to a new study.

The US researchers also found that a number of environmental and occupational health and safety risks are linked to their production – but acknowledged that bio-based materials may be more sustainable than petroleum based counterparts.

The study - Sustainability of bio-based plastics: general comparative analysis and recommendations for improvement, by Kenneth Geiser et al – was published in the Journal of Cleaner Production.

In two sustainability and safety spectrums to display their analysis the scientists declared that polylactide acid (PLA), starch (pure thermoplastic starch: TPS) and polyhydroxyalkanoates (PHAs), scored highest, while nano-biocomposites were labelled as the least preferable.

Aims and methodology

Sustainable materials reduce impacts to occupational and public health as well as the environment, said the team. The aim of the project was to qualitatively gauge the general sustainability of a raft of different bio-based plastics by reviewing literature and evaluating the environmental, health and safety impacts through their cradle to grave lifecycle analysis (LCA).

Bio-based plastics are those “in which 100% of the carbon is derived from renewable agricultural and forestry resources such as corn starch, soybean protein and cellulose”, said the group, citing the definition from the Business-NGO Working Group for Safer Chemicals and Safer Materials.

The scientists from the University of Massachusetts-Lowell University conducted a LCA that also included occupational and environmental hazards. These included the use of genetically modified organisms (GMOs) and hazardous pesticides to grow feedstocks as well as utilization of dangerous chemicals or petroleum-based co-polymers during plastic production and processing; risky additives, untested nanomaterials, workplaces hazards, disposal options as well as potential impacts to food supply and water and energy usage.

Sustainability spectrum

The study produced the Principles for Sustainable Biomaterials. Although it found that bio-based materials delivered measurable eco-improvements over petroleum-based plastics (PBM), the team said that none were fully sustainable.

"Although bio-based plastics may be more sustainable than petroleum-based plastics in some aspects, this analysis found that there are environmental and occupational health and safety hazards in their production," said the study.

It added: “Although advances have been achieved, fully sustainable bio-based plastics with all the highly valued properties of conventional plastics for all types of products are not yet available.”

The research said PLA production uses 30-50% less fossil energy and generates 50-70% less CO2 emission than PBP but highlighted that feedstock for the material is grown using GMOs and pesticides. Fine starch dust can also cause explosions. Some or all of these concerns were also noted for production of PHA, TPS and poly(trimethylene terephthalate).

Nano-biocomposites, such as cellulose and lignin were evaluated as having relatively high energy and water requirements, emission problems and potential toxicity hazards.

The study said preferred Bioplastics would use non-GMO feedstock, avoid hazardous additives, be energy and water efficient, address environmental and safety concerns during production, not impact the food supply by using by-products rather that primary food feedstocks. They should also have flexible disposal options such as compostability or recyclability.

Source: Journal of Cleaner Production