Biodegradable films from agro-food waste: Cost-benefit analysis

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The use of agro-industrial residues as a raw material to produce bioplastics has many advantages. In fact, bioplastics can reduce the amount of food packaging disposed of in landfills, resulting in less plastic leakage into the environment.

Moreover, end-of-life processes of these residues, such as industrial composting or anaerobic digestion, can reduce greenhouse gas emissions and recover organic carbon, which can be further recycled.

Demand for bioplastics is growing: The annual global production of bioplastics is estimated at 2.11 million tons, of which 26.3% is used for flexible packaging applications and 21% for rigid packaging. More than 24% of bioplastics are currently produced in Europe. However, their current market share is <1%, mainly because investments in bioplastics applications suffer from production costs that are too high compared to conventional fossil-based polymers. This situation is due to the chemical complexity of the bio-based feedstocks, the fermentation or extraction conditions and the downstream separation process for product recovery.

In fact, not all bioplastics have high production costs: For example, polylactic acid (PLA) is currently by far the most commercially developed biodegradable polymer due to its relatively low production cost. However, the use of PLA in food packaging is limited due to its stiffness, brittleness, and poor thermo-mechanical properties. To overcome these inherent limitations of PLA, many research activities are focused on developing bioplastic films that combine PLA with other biopolymers, such as polyhydroxybutyrate (PHB).

In this context, recent studies by G. Tassinari et al., conducted by the University of Wageningen (Netherlands) and the Catholic University of Piacenza (Italy) (Science of the Total Environment 856, 2023, 159101), analysed the economic aspects of the production of new packaging films based on a polylactic acid-polyhydroxybutyrate (PLA-PHB) blend plasticized with oligomeric lactic acid (OLA). This activity was supported by the European Union and the Bio-based Industries Consortium. The specific objectives of this study were mainly two:

  • – Evaluate the minimum selling price of material produced for different industrial scales in Europe under conditions that would attract investors, such as a n low payback period between investment and placing on the market. A four-year payback period was chosen, which is generally accepted.
  • – Perform a cost-benefit analysis of the preliminary process because the economic viability of the investment is a very important parameter for establishing the sustainability of the final product. Previous studies have investigated the techno-economic feasibility of PLA and PHB separately, but no one has yet evaluated the profitability of a PLA-PHB blend plasticized with OLA.

Regarding the specifications of the plastic material, it should be noted that all the plastic components of the blend come from renewable resources: The production of PHB uses potato peel residues from agriculture and food industries, while both PLA and OLA can be produced from starch. Film production involves a multi-step process: (i) the production of PHB from potato peels, (ii) the co-blending of PHB with PLA and OLA (as plasticizer) and (iii) film extrusion.

Technology Readiness Level

The final material thus obtained fulfils all biodegradability and compostability standards, as verified by the tests provided. To evaluate the economic aspects related to the production of this material, it would be necessary to have information on the related industrial process, but this is not available because this new material has not yet been produced industrially, so its Technology Readiness Level (TRL) is still low. It may be useful to take a cue from the historical costs of similar commercial installations, but these data are rarely shared by companies or made public.

This lack of information was overcome by simulating the impact of certain parameters on the minimum sales price of the product. The parameters considered were industrial production scales and logistics settings. By adopting this approach, the authors were able to assess the economic aspects of PLA-PHB films at European level. This is an important achievement because this early-stage cost estimation method not only provides information on the economic feasibility of investments in biodegradable and compostable plastics but can also be applied for the economic assessment of other production processes characterized by low TRL.

The results of this study showed that the availability of raw materials of biological origin is the most important factor for the profitability of the production of this new material. The creation of plants to produce these films only pays off when larger plants of the order of 9-18 kt per year are reached. There will be no competition if there is only one large plant that collects all resources within an area, thus creating mono/oligopoly regimes. Alternatively, reducing transport costs is a key element in the production organization of a bio-refinery: Minimising transport distances by developing many small plants close to a single potato processor is more cost-effective.

Although numerous, there will be no competition between the plants for the supply of resources, given their low productivity. According to this study, intermediate-sized plants are unlikely to perform better than other-scale plants, because this increases competition for resources, which affects the cost of acquiring biomass and increases collection distances. It must be said, however, that these results have limitations, because they only consider the number and size of biorefineries as characterizing parameters and assume that all available agro-food waste is recycled.

For a four-year payback period, the calculated minimum product selling price ranges from 9.7 Euro  per kilogram to 37.2 Euro per kilogram, depending, among other factors, on the production capacity of the biorefinery. Unfortunately, this price is much higher than the current market price for fossil plastics, which is around EUR 1-1,5 per kilogram, so the production of this material is currently not competitive on an industrial scale. Without prejudice to the urgent need to redesign plastic for more sustainable production processes, further studies are needed to increase production efficiency at fixed costs.

To sum up, the production of bioplastics from agro-food waste can become economically viable in two situations: (i) the high availability of agro-industrial residues; (ii) the presence of very large or very small plants, which may perform better economically than intermediate-sized plants. These results do not consider the complexity of biorefineries or the environmental impact of the production of this material on an industrial scale and suffer from the lack of information due to the low TRL of the technology studied. A more comprehensive evaluation of the sustainability of PLA-PHB blends requires further research considering all these parameters.

References: Tassinari et al., Science of the Total Environment 856, 2023, 159101.