15 questions about biobased plastics in a sustainable society

Biobased plastics are plastics that are made entirely or partially from biological resources such as sustainably grown biomass and bio-waste. Examples include bio-polyethylene from sugarcane or corn and PLA from plant sugar.

Biodegradable plastics can be broken down by microorganisms into water, carbon dioxide (or methane), and biomass under specific conditions. A common misconception is that biobased plastics are always biodegradable or compostable, but non-biodegradable durable biobased plastics also exist.

For instance, a chemical coating for housing might be biobased but not biodegradable, whereas food packaging materials like tea bags and coffee cups would benefit from being biodegradable.

Biobased plastics can be produced in different ways, namely as 'drop-in' biobased plastics and 'new biobased alternatives':

• ‘Drop-in’ biobased plastics are plastics where biomass, material from plant or animal origin, is used to create the same chemical building blocks and polymers currently derived from fossil fuels. The production process is similar, apart from the feedstock preparation, and the resulting plastics are identical to existing materials.
• A ‘novel biobased alternative’ is a biobased polymer with a different chemical structure but similar or better properties, fulfilling the same function as existing fossil-based plastics. Note that the term ‘novel’ is optional, as some biobased polymers, like PLA, were discovered as early as 1920.

CO2-based plastics use captured CO2 (combined with green hydrogen) to create the same chemical building blocks and polymers currently derived from fossil fuels, making it a drop-in pathway. Like synthetic fuels, polymers from CO2 are sometimes called ‘synthetic’ or ‘syn-’ polymers.

Biobased plastics are expected to play a significant role in global plastic sustainability. Using biomass, a renewable carbon source, for plastics can help mitigate greenhouse gas emissions and, under certain conditions, act as a carbon sink when integrated into durable products.

Determining the best mix of renewable carbon (biomass and CO2) for sustainable plastic production is challenging. Not every renewable carbon application is automatically the most sustainable, but fossil fuel-based production is not sustainable. The share of biobased plastics in a fully non-fossil plastics system is difficult to predict due to dependencies on regulation, approval, adoption, and matching the right feedstocks and conversion technologies with the right products and applications in the right locations.

The 3-step plan presented in the whitepaper ‘Pathways to sustainable plastics’ allows users to compare renewable carbon-based options for plastics for specific applications, identifying where biobased plastics are best used and unlocking opportunities for them.

Recycling plays a significant role in achieving plastic sustainability. It effectively uses plastic waste feedstock, conserving resources. Both mechanical and advanced recycling should be maximised.

However, even if global recycling rates reach their theoretical maximum, only about 60-70% of total volumes can be produced from recycled plastic feedstock.

This estimation accounts for losses during production, usage, collection, biodegradation, and recycling process yield losses. Thus, significant sustainable virgin plastic production will still be required to replace losses and meet growing demand.

A small proportion can be replaced by natural biopolymers such as cellulose, starch, and their derivatives. The production of biobased plastics from biomass and CO2 can help bridge the gap between the amount of recycled plastic and the total demand for plastic. They are the only remaining options for the sustainable production of new plastic and play an important role in the transition to a more sustainable and circular plastic system.

The sustainability of biobased plastics has been debated among experts. They are diverse and can be used for nearly all existing plastic applications. Using biomass as a feedstock for plastics holds promise in reducing greenhouse gas emissions and, under specific conditions, can act as a carbon sink in durable products.

Considerations around biomass use for plastics include competition with feed/food for first-generation feedstocks, land use changes, water use, biodiversity impact, collection and logistics complexity, and competition from fuels and energy. It is crucial that the feedstock is sourced sustainably and that the full life cycle of these plastics is examined to ensure benefits beyond reducing fossil feedstock use

A variety of biomass types can be utilised to produce bioplastics. Typically, biomass feedstock is categorised into first, second, and third generation feedstocks:

• The first generation biomass includes readily fermentable sugars from edible polysaccharide sources (e.g., maize, sugarcane) and edible (vegetable) oils. The use of first-generation biomass remains a topic of debate, primarily due to ethical concerns regarding competition for food resources and changes in land use. However, some studies suggest that sustainable co-production of biomass for both food and materials is feasible.
• The second generation biomass consists of non-edible biowastes such as agricultural and food waste (e.g., non-edible oils, forest residues, agricultural residues, organic waste). Second generation biomass provides a less contentious, more affordable, and widely available feedstock for bioplastics, although it does come with the challenges of complexity and the need for additional pre-treatments.
• The third generation biomass refers to novel biomass feedstocks being explored for use, such as algae. For the global use cases in this whitepaper, all biomass types are currently included, with an emphasis on the importance of focusing on second- and third-generation feedstocks for bioplastics production.

Plastics serve various functions in society across different applications, ranging from long-lasting construction materials to single-use packaging and mixed waste.

Currently, these functions are fulfilled by 9 common (fossil) polymer materials, which account for 80-90% of today’s global plastic volume:

• LDPE (Low-density polyethylene);
• HDPE (High-density polyethylene);
• PP (Polypropylene);
• PS (Polystyrene);
• PVC (Polyvinyl chloride);
• PET (Polyethylene terephthalate);
• PUR (Polyurethane);
• PA (Polyamide);
• ABS (Acrylonitrile Butadiene Styrene).

The 3-step plan presented in the whitepaper can be applied to all these materials to create a systemic view of pathways to sustainable plastics. Additionally, it is possible to add a polymer material when relevant.

The 3-step plan can be applied to your situation. For industry players, this enables the determination of the best pathway for renewable carbon-based production and material selection for your products.

The whitepaper presents the application of the 3-step plan for four global use cases, showcasing how it works. By setting precise input parameters and defining constraints (such as biomass availability or supplier products), stakeholders like brand owners, polymer producers, and plastic compounders can make informed material choices.

The 3-step plan can be tailored to your situation, incorporating specific input parameters and constraints. It allows companies to assess the impact of potential changes in their production pathways, such as switching from first-generation to second-generation feedstock for the same biobased plastic material.

To specify a novel biobased alternative pathway, the first question is: ‘Which novel biobased alternative polymer can be applied here?’. TNO developed a method to compare the properties of (novel) biobased polymers with existing polymer products in various applications.

A list of over 1,000 potential novel biobased polymers was assessed and compared to existing fossil materials on five key properties: modulus, tensile strength, elongation at break, oxygen transmission rate, and impact strength.

Based on a match in properties, a novel biobased alternative is identified as a close substitute for a specific product application. Initial analysis shows that novel biobased polymer alternatives can potentially fulfil most existing applications, with at least a 90% match in properties. Where no suitable novel biobased alternative exists, biobased polymer design by machine learning could be applied.

Yes, to compare pathways on environmental sustainability, a sustainability impact assessment tool was developed, combining Material Flow Analysis (MFA) and LCA inventories. Environmental sustainability impact includes multiple indicators such as global warming potential, cumulative energy demand, land use, water depletion, and feedstock input required. It is important to include indicators beyond CO2 emissions, as biomass production for plastics can significantly impact water use and biodiversity.

The 3-step plan provides an approach applicable to various scopes. It can incorporate specific situations or potential future scenarios in terms of production processes, technology, or energy/feedstock inputs. It offers a robust tool for assessing the impact of technical advancements on the plastics production system.

As new production pathways for biobased or synthetic polymers emerge or are refined, the 3-step plan allows for immediate assessment and comparison with existing alternatives. It also highlights non-viable or less sustainable pathways, providing insights into areas needing innovation. The 3-step plan can evaluate the impact of technological developments or novel innovations within specific production steps, analysing different technological scenarios like learning curves, yield improvements, and future energy mix assumptions.

Applying the 3-step plan to all major plastic products in the global plastics system can determine optimised pathways towards a sustainable circular plastics system. This approach enables stakeholders to identify the most suitable renewable carbon-based production pathway for each plastic type and application, providing clear guidance on necessary decisions and actions.

Compiling the results allows users to draw conclusions on the overall share of biobased versus CO2-based plastics and identify product applications where bioplastics make the most sense, unlocking market opportunities.

TNO’s 3-step plan supports industry players and policymakers in transitioning to renewable carbon-based plastics by finding the most sustainable and economically feasible solution for their products.

Practically, we will work together through the three steps of the 3-step plan for your situation during a project. We will discuss and agree on parameters, biomass types, technologies, and materials to include or exclude, and iteratively optimise the value chains to be compared.

We will also determine constraints and relevant scenarios to advise on the optimal pathway for your products.