Production of PHA Bioplastics on side streams

PRODUCTION OF PHA BIOPLASTICS ON SIDE STREAMS WHITE PAPER OCTOBER 2023 1

“SHIFTING TOWARDS PRODUCING AND USING BIOBASED DEGRADABLE PLASTICS REPRESENTS A CRUCIAL STEP FORWARD IN MITIGATING THE ENVIRONMENTAL IMPACT OF OUR PLASTIC CONSUMPTION “

AUTHORS MNEXT/Avans University of Applied Sciences: Jappe de Best Mithyzi Andrade Leal Alexander Compeer Valentin Contin University of Kaiserslautern-Landau: Cora Laumeyer Heidrun Steinmetz Trinity College Dublin: John Gallagher LAB University of Applied Sciences: Ossi Martika Wupperverbandsgesellschaft für integrale Wasserwirtschaft mbH: Inka Hobus

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INTRODUCTION In today’s rapidly evolving world, the use of plastics has become an integral part of our daily lives, offering convenience and versatility like never before. However, our dependence on plastics, often derived from non-renewable fossil fuels, has raised critical concerns about their environmental impact. From the persistent problem of plastic pollution clogging our oceans to the substantial greenhouse gas emissions associated with their production, it has become increasingly apparent that we need to re-evaluate our reliance on these conventional plastics.

This realization has spurred a growing interest in sustainable alternatives, and one promising avenue is the development and utilization of biobased degradable plastics, such as polyhydroxyalkanoates (PHA). The shift towards producing and using biobased degradable plastics represents a crucial step forward in mitigating the environmental impact of our plastic consumption, paving the way for a more responsible and sustainable future.

In this white paper, we will explore the opportunities and challenges of PHA production by mixed microbial cultures using side streams from industries and municipal wastewater. After a brief introduction to PHA, we will explore the following: PHA PRODUCTION CHAIN APPLICATION OF PHA LOGISTICS OF PHA PRODUCTION CIRCULARITY OF PHA PRODUCTION FUTURE CHALLENGES OF PHA PRODUCTION ENJOY READING! This whitepaper gives an overview of (part of) the results of the Interreg NWE project WOW! - Wider business Opportunities for raw materials from Wastewater. More information about this project can be found on the website of WOW!

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What are polyhydroxyalkanoates (PHA)?

PHA are a group of naturally occurring biopolymers that are produced by certain microorganisms as intracellular carbon and energy storage compounds. PHAs are considered biodegradable and biocompatible, which makes them of significant interest in various fields, including biotechnology, materials science, and environmental sustainability.

Here are some key characteristics and properties of PHAs: Microbial Production: PHAs are synthesized by certain bacteria as intracellular granules when they have access to an excess of carbon sources but limited sources of other essential nutrients like nitrogen and phosphorus. The accumulated PHA granules serve as an energy reserve for the microorganisms.

Types of PHAs: There are many different types of PHAs, each with slightly different properties. Common types of PHAs include polyhydroxybutyrate (PHB), polyhydroxyvalerate (PHV), and polyhydroxyhexanoate (PHH).

The specific properties of a PHA depend on its chemical structure, which can be tailored through genetic engineering techniques.

Thermoplastic Properties: Some PHAs exhibit thermoplastic properties, which means they can be melted and moulded into various shapes.

These properties make them useful for the production of biodegradable plastics, films, coatings, and packaging materials.

Applications of PHAs span various industries, including agriculture, packaging, biomedical, and environmental remediation. Researchers and companies continue to explore and develop new ways to produce and utilize PHAs to reduce the environmental impact of plastics and create sustainable alternatives to conventional plastics.

GLOBAL BIOPLASTICS VOLUME

In 2021, the global plastics production increased to 390.7 million tonnes, of which fossil-based plastics comprised 352.7 Mt, recycled postconsumer plastics 32.5 Mt and bio-based 5.9 Mt, i.e., 1.51% of all plastics produced. _PHA covered 3.9% of global bioplastics production capacity, while PLA had the highest capacity by margin, 20.7%. Another notable fact is that of the biobased plastics production capacity, the share of biodegradable plastics was 51.5%.

Biodegradability: PHAs are biodegradable, meaning they can be broken down by microorganisms in the environment, leading to their decomposition into harmless substances like water and carbon dioxide. This makes them environmentally friendly and suitable for various applications where plastic pollution is a concern.

Biocompatibility: PHAs are generally non-toxic and biocompatible, making them suitable for use in medical and pharmaceutical applications, such as drug delivery systems and tissue engineering.

Versatility: PHAs can be synthesized in a wide range of structures and properties by altering the microbial strains used for production and by adjusting the carbon sources fed to these microorganisms. This versatility allows for the customization of PHAs to meet specific requirements for various applications.

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PHA production and extraction To produce PHA from residual streams from the food industry, several process steps need to be performed as depicted in figure 1. The different processes can be clustered in upstream and downstream processes. The upstream process consists of the steps to produce PHArich biomass (step 1, 2 and 3). The downstream process consists of the extraction and processing of the final product (step 4 and 5).

FROM RESIDUAL STREAM TO FEEDSTOCK FOR PHA PRODUCTION (STEP 1)

The feedstock for the PHA production is obtained by an anaerobic decomposition of the different organic compounds that are present in the residual stream: carbohydrates, proteins and fats. These compounds can be converted to different products by microorganisms as shown in figure 2. This process is called acidification.

Few of the products formed are organic acids, so -called volatile fatty acids (VFAs). These VFAs are the feedstock for PHA production.

Figure 2: Consecutive steps of the anaerobic fermentation. To end up with the feedstock for PHA-production, the formation of biogas needs to be suppressed.

During the production, microorganisms can also further convert VFAs to methane (CH4) and carbon dioxide (CO2) as shown in figure 1. As we want to use the VFAs for PHA production, this conversion to methane and carbon dioxide needs to be suppressed. This is achieved by keeping the pH lower than 6 and the sludge age less than 8 days.

Figure 3 and 4 on the next page show the results of the acidification of the residual streams of two different industries: a beer brewery and a fruit juice producer. Substrate 1 to substrate 11 represent the different runs of the reactor.

Figure 1: WOW-PHA production chain.

The results show clearly that the acidification of different residual streams yields a different composition of VFAs. It is striking, that the differences do not only occur between the substrates of the two industries but also between batches of the “same” residual stream, due to changes in the composition of the initial residual stream.

Overall, the residual stream of the fruit juice company resulted in a higher concentration of VFAs, however, the percentage of organic compounds in the residual stream that were converted to VFAs is lower. Furthermore, the residual stream of the brewery had a more stable VFA composition and concentration throughout the batch experiments.

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Figure 3: VFA-composition of the substrate derived by the batch-fermentation of the residual stream of a brewery.

ENRICHMENT – BIOMASS SELECTION (STEP 2)

The process of PHA production starts using activated sludge from a sewage treatment plant. This activated sludge contains different bacteria. Some of them can synthesize PHA as energy storage. In a bioreactor, the VFA-rich substrate that is produced in the acidification step (step 1) is added to the activated sludge as feedstock (food). To favour the growth of PHAproducing bacteria, the process is operated in a feast-and- famine regime. This means that after feeding the activated sludge with VFAs for a certain amount of time (feast), the feeding stops (famine). During this famine phase, the PHAproducing bacteria can survive and reproduce by consuming the PHA they stored inside their cell as energy storage. Other bacteria do not survive.

As a result, the biomass composition changes, and the percentage of PHA-producing bacteria increases.

ACCUMULATION – PHA-PRODUCTION (STEP 3)

For the actual PHA accumulation, a part of the biomass from the enrichment process (step 2) is transferred to another reactor. In this reactor, the VFA-rich substrate of step 1 is supplied in such a way that the bacteria are synthesizing more PHA than they usually would. This is because bacteria have been kept in limited conditions during the enrichment phase. The accumulation was operated as a fed-batch reactor in which VFA feed is added every 30 min over 24h. In this way, up to 90% of the PHA concentrations inside the bacterial cell can be reached.

Figure 4: VFA-composition of the substrate derived by the batch-fermentation of the residual stream of a fruit juice company.

After 24 hours, the fed-batch process is finished by dewatering the biomass using a centrifuge.

After centrifugation, the biomass is transferred to a drying cabinet to dry. Afterwards, the PHA extraction starts (step 4) .

The PHA composition of the dried biomass is analysed using a gas chromatograph (GC) to get information about the monomeric composition of the biopolymer (see “What are polyhydroxyalkanoates (PHA)?”). The results of our experiments with residual streams from the brewery and fruit juice company show that there is a difference in both the amount of PHA produced (Figure 5) as well as in the composition (table 1 and table 2). Both produced PHAs mainly contain HB (hydroxybutyrate). However, besides HB and HV, the fruit juice-derived PHA also comprises small amounts of HH (hydroxy hexanoate). This shows that different residual streams can be used to produce polymers with different compositions and material properties.

Figure 5: Percentage of PHA based on the dry matter of PHArich biomass using different feedstocks from residual streams.

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PHA

FRACTION OF MIN-MAX PHA

HB

0.79 ± 0.27

0.0 – 1.00

HV

0.13 ± 0.16

0.0 – 0.49

HH

1.2 ± 2.2

0.0 – 5.3

Table 1: Monomeric composition of the PHA produced by using the VFA-rich substrate of the fruit juice company’s residual stream.

PHA

FRACTION OF PHA

MIN-MAX

HB

0.81 ± 0.22

0.0 – 1.00

HV

0.13 ± 0.8

0.0 – 0.30

Table 2: Monomeric composition of the PHA produced by using the VFA-rich substrate of the brewery’s residual stream.

PHA EXTRACTION (STEP 4)

After dewatering and drying, the PHA in the bacteria cell needs to be extracted using solvent.

This was done for both the PHA rich biomass that was produced from the residual streams from the brewery- company (brewery-PHA) and the fruit juice company (fruit-PHA).

and when it enters the environment, it will be hydrolysed into harmless products. DMC also shows good results for PHA extraction as can be seen in table 3.

Extraction method PHA was extracted from the biomass via reflux.

This is done by adding dimethyl carbonate (DMC) as a solvent to a 1 L glass reactor with mechanical stirring. This one is connected to a cooling column following the scheme shown in Figure 6. For each 300 g of biomass loaded in the reactor, 800 mL of solvent was added, meaning 0.375 g/mL biomass-to- solvent ratio for each cycle of extraction. The extraction was done in 4 cycles for each batch of biomass added to the reactor. The overall biomass-to-solvent ratio was 0.10 g/ml. The glass reactor was heated up to the boiling point of the solvent (90°C for the DMC) for 30 min in each cycle. After the extraction, a vacuum filtration was performed to separate the biomass from the solution. A rotary evaporator was used to recover the solvent and to separate the PHA. The obtained PHA was left to dry overnight inside the fume hood and then weighed.

Choice of solvent When applying solvent extraction, the choice of solvent has a profound influence on many aspects of the process design.

The criteria for solvent selection follow the list below: • Safety, health, and environment • Biopolymer solubility potential • Solvent recovery from residual biomass • Solvent regeneration • Costs

Figure 6. Laboratory scheme for extraction of WOW-PHA using DMC.

Until recently, mainly organic solvents (chloroform, dichloromethane, acetone, ethyl acetate, 1-butanol) were used. However, these solvents are potentially harmful for the environment. Therefore, in the Interreg NWE WOW! project the recovery of PHA was done through a green extraction method which uses dimethyl carbonate (DMC) as described by de Souza Reis et al. (2020). The advantages of using DMC are the low boiling point, low costs, nontoxicity, can be reused, less reactivity to PHA,

Table 3: Comparative extraction results for the different solvents for PHA rich biomass produced from synthetic feed.

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RESIDUAL STREAM

BREWERY

FRUIT JUICE

Average PHA content [g PHA/ g TS]

20.4 %

19.4 %

PHA like material extracted [g]

204.8

521.4

Purity [g pure PHA/g dried extracted PHA]

78.8 %

81.1 %

Extraction yield [g PHA material like/100 g intercellular PHA]

76.9 % ± 8.2

93.2 % ± 7.2

Table 4. Mass balance for WOW-PHA extraction.

PHA quality and quantity Table 4 shows the mass balance for the extraction of the brewery-PHA and the fruitPHA. In total, 726.26 g of PHA was extracted. The purity of the produced PHA is around 80%. This is considerably lower than the purity of the PHA produced from synthetic feed (table 3). This is as expected since the composition of the residual stream influence directly the solvent extraction due to change in solubility range and, therefore, the end product material. A purification step either in the VFA production step (membrane separation, gas stripping, electrodialysis, etc) or in the downstream processing (anti-solvent or crystallization) of the PHA-rich biomass could increase PHA purity.

The yield of extraction for the PHA from the residual stream from the brewery company (brewery-PHA) was lower (81%) than for the PHA from the residual stream from the fruit juice company (fruit-PHA, 93%). This can be explained by the composition and characteristics of the PHA (see table 5).

Ø HB [%]

Ø HV [%]

Ø Crystallinity HH [%] [%]

Brewery 81,8

17,5

0,7

18,45

Fruit 79,8 15,3 4,9 11,59 Juice

Table 5: PHA monomer composition and characteristics.

HB = hydoxybutyrate, HV = hydroxyvalorate, HH = hydroxyhexanoate.

Figure 7. Brewery - PHA extracted.

The overall PHA recovery for both residual streams is 69.7 % (taking the purity into account). The recovery is calculated based on the amount of pure polymer extracted divided by the theoretical amount of the polymer inside the bacteria cells.

Figure 7 and figure 8 show pictures from the extracted PHAs. As can be seen, the breweryPHA has an orange-red colour compared to the more white/yellow colour of the fruit-PHA. The origin of the orange-red colour is not clear but the extracted solution also shows a similar colour.

When looking at the characteristics of the produced PHA, the brewery-PHA had a flexible texture and was collected mostly as a thick film.

The Fruit-PHA was much more brittle, contained more water and was most of the time collected as pieces, or sometimes, powder.

PHA composition Table 5 gives an overview of the monomer composition (Ø, %) of the extracted Brewery-PHA and Fruit-PHA. Both PHAs mainly consist of HB (around 80%). The HV content is only around 15%. The Fruit-PHA contains a substantial amount of HH (around 5%). A higher HH content means decrease in crystallinity. This lower crystallinity, in combination with an observed lower melting temperature (Tm) and lower enthalpy of fusion (ΔHm), compared to brewery-PHA can also explain the higher yield of extraction for fruit-PHA. More explanation on this can be found in the Technical report on pilot scale testing of PHA production and extraction from industrial residual streams > click here.

Figure 8. Fruit - PHA extracted.

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VFA PRODUCTION

PHA PILOT

THE PROCESS OF PHA EXTRACTION AND PRODUCTION

PHA-ENRICHED BIOMASS

PHA EXTRACTION

DRIED PHA-ENRICHED BIOMASS

EXTRACTED PHA

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Figure 9. Filament production and 3D-printing process; feeding PHA raw-material, extrusion of filament, spooling and 3D-printing.

APPLICATION OF PHA CURRENT APPLICATIONS OF PHA

PHA can be utilized in multiple industries and applications. Its advantage in addition to being biobased and biodegradable, is that it can be processed using the same techniques and machinery, e.g. injection molding and film blowing, that are commonly used with traditional oilbased plastics.

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In packaging and food industry, it is suitable for practically all short-time-of-use applications, e.g., wrappings and disposable food utensils. PHAs are very promising materials for compostable food packaging as they have high barrier properties towards oxygen permeation. This provides good shelf-life for products that are susceptible to oxidative spoiling. PHA is at least as good packaging material in terms of food quality than traditionally used HDPE. As early as 1996, Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) has received European approval for food contact application. Also, PHA oligomers are usable ketone sources in food supplements. PHAs can also be used as coating for paper materials resulting in increased gloss, brightness, and strength.

• As PHA is a nylon, it can be processed into fibers and used in textiles.

• PHA can be used in multitude of medical applications, including implants, heart valves, controlled drug release matrices and tissue engineering materials as result of their biocompatibility. The good biocompatibility manifests so, that e.g. PHB has been found to degrade in vivo to d-3-hydroxybutyic acid, which is a normal component of human blood.

A rising trend in PHA use is in skin-care, as PHAs are exfoliants and humectants. Many PHAs also have antioxidant properties and Gluconolactone has been used in multitude of cosmetic preparations. It has been found also suitable for protection against UV induced damage. Applications that do not require high purity PHA include self-healing concrete.

PRODUCT EXAMPLES MADEOF PHA PRODUCED IN THE WOW! PROJECT

As the PHA produced in the WoW! project is derived from residual streams, this currently limits the possible applications due to, e.g., highquality requirements and impurities present in the PHA. It is, therefore, currently prohibited to use in food-contact applications and medical applications. Thus, the prototype products that have been selected are not limited by the origin of the PHA while they take full advantage of the biodegradability and compostability of PHA in the nature.

The prototype products chosen are used outdoors and have a notable risk of ending up in nature. The demo products selected are a fishing lure, golf tee, pole holder for cross country skiing and a mudguard for mountain bikes (MTB).

They prototypes are produced using 3D printing.

The advantage of 3D printing is that it enables easy personalization of products in small-scale production and especially producing novel shapes and functionalities that are difficult or even impossible to achieve with the current volume processing methods, e.g., the fishing lure.

The 3D printing process is illustrated in figure 9 and the principle of fused deposit modeling (FDM) 3D printing used in the project is shown in figure 10. In following sections, two prototypes are presented in detail.

Figure 10: Principle of Fused deposit modeling (FDM). The filament is melted and extruded on the printer bed. Typically, the printing head (consisting of nozzle, heater and feeder) moves horizontally and the bed vertically.

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USE OF PHA FROM RESIDUAL STREAMS IN 3D PRINTING

The use of PHA produced from residual streams in 3D printing has some challenges if the material is not purified. The PHA could be turned into filament that could be processed without special equipment but the filament was brittle filament and had a distinct stench. The properties of the filament depended on the origin of the PHA (residual stream of brewery or fruit company). This manifested in tensile properties of the filament and 3D printed specimen. These differences can be explained by the composition of the PHA as explained with the PHA extraction. The processability can be improved by blending the PHA with other biobased and biodegradable plastics, such as polybutylene succinate (PBS).

FISHING LURE

Fishing lures were identified as one well suitable application for the PHA produced in the WoW! project. Figure 11 shows an example of a 3D-printed fishing lure from PHA. Mechanical properties and durability of the PHA were determined to be well suitable for lures.

As lures are known to get stuck and lost in rapids, lakes, and seas, the amount of lure waste culminating into the aquatic environment is notable. Considering that if only 1% of lures sold per year are lost, a total of about 10,000,000 lures end up at the bottom of water bodies. The use of biodegradable PHA fishing lures can solve this issue.

GOLF TEE

It has been estimated by the golf industry that approximately 5 million golf tees are used annually in golf games, creating a notable amount of plastic waste. Again, this can be solved by using 3D-printed PHA golf tees. The tee prototypes printed are shown in Figure 12.

The biggest advantage of utilizing 3D-printing for producing golf tees from PHA is that personalization of the tees can be easily applied, e.g., adding name or logo to the tee. This, in addition to the compostability of PHA, creates significant potential for added value by upgrading the tee from basic commodity to, for example, a notably more valuable personal gift.

CONCLUSION

The findings of the WoW! project demonstrate the potential of wastewater-derived PHA in 3D printing. Also, the properties of the filament and +3D printed products can be altered by varying the raw material source and composition along with blending the PHA with other polymers.

3D printing provides a relatively easy route for the application of PHA produced from residual streams into actual products..

The lures are also an appealing application from the business point of view, as the global fishing lure market has been estimated to be US$ 3.96 bn in 2023. In addition, it has been estimated that approximately 1 billion fishing lures are sold globally each year.

Figure 11. The fishing lure ready to be used. N.B. the flexibility enabled by 3D-printing as the lure was manufactured in one piece.

Figure 12. Two variations of golf tees.

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Geographical journey – exploring the best potential location for PHA production Within the framework of WOW! Project, the market potential and technical feasibility for the production of bioplastic (PHA) from sewage with primary sludge as feedstock has been proved. However, an estimate of economic viability has shown that this requires a production of at least 5,000 tons of PHA per year. For this, a wastewater treatment plant (WWTP) capacity of approximately 2 million people equivalent (PE) is needed. More information can be found in the reports ‘Designing value chains for carbon-based elements from sewage water: A market potential study’ > click here and ‘Techno-economic assessment of producing bioplastics from sewage’ > click here.

Figure 13: Example of a central plant for PHA accumulation, extracting and compounding and decentral plants providing dewatered PHA-rich biomass respective dried PHA-rich biomass.

In most regions of North-West Europe, WWTPs typically have a capacity below 2 million PE. Therefore, research was conducted to strategically place a centralized PHA production facility, where a combination of WWTPs would provide the necessary sludge for the central PHA production plant. This was done for three regions (Scotland, Ireland and Germany) with the help of the decision support tool (DST). The goal was to let geographical information system (GIS) software pick the best location for a centralised PHA production facility with regard to minimized transport. It also shows the participating WWTPs which are required to gather enough primary sludge to produce 5,000 tons of PHA per year.

All of this takes into account technical, economic and environmental aspects.

CONCEPTS FOR PHA-PRODUCTION CONSIDERING SEVERAL WWTPS

The main environmental aspect in this assessment was transportation. By reducing transport distances, you can reduce environmental impact. However, since primary sludge contains a lot of water, the assessment also investigated if it is better to install the first step of the process (which is PHA enrichment from primary sludge) at the participating WWTPs and transport PHA-enriched biomass to the centralized PHA production plant. In this way transport is reduced, but on the other hand more technical installations are needed (PHA enrichment facility, dewatering unit and drier).

From a technical point of view, the assessment only took into account WWTPs with a capacity of 50,000 PE or higher. Having a dryer onsite was only considered feasible at WWTPs of more than 300,000 PE.

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Figure 14: GIS result for the ideal location of a centralised PHA-production and decentralised PHA-enrichment plants in Scotland.

BEST POTENTIAL LOCATION DEPENDING ON REGIONAL BOUNDARY CONDITIONS

The outcome showed that for Scotland, the ideal location for a PHA production facility would be Shieldhall, near Glasgow, including 9 WWTPs that would need to contribute their primary sludge to the PHA production facility at Shieldhall.

The total transport distance per year would be around 310,000 kilometres. When transporting only dewatered or even dried biomass, only 4 WWTPs would need to contribute, reducing the total transport distance to 17,000 kilometres, but additional facilities (PHA enrichment facility, dewatering unit, drier) need to be installed at all 4 contributing WWTPs. For Ireland, Ringsend, near Dublin, was the chosen location, requiring 3 WWTPs at roughly 20 km to bring its primary sludge to Ringsend.

For Germany, there are 8 potential locations spread around the country that could each fit a centralised PHA production facility, assuming the boundaries that a maximum of 7 WWTPs may contribute within 45 km distance, each having a capacity of at least 300,000 PE and having a PHA enrichment facility, dewatering unit and drier onsite. The WWTPs with a capacity high enough (> 2,000,000 PE) to have their own PHA production facility were not taken into account in the assessment.

construction of a central plant results in the lowest costs for CAPEX and OPEX. The transport costs for one central PHA extraction plant and several decentralised plants for PHA enrichment are very low. However, the installation of several smaller PHA accumulation plants increases the capital costs (CAPEX) as well as the operating costs (OPEX) due to the higher staff cost.

From a financial point of view, the concept of transporting primary sludge would result in a cost of around €4.90 per kg of PHA, while transport of dewatered or dried PHA-enriched biomass would result in around €6.30 per kg of PHA. The specific production costs for the regional approaches for PHA production are still above the market price of 4 €/kg for PHA products from renewable raw materials.

A detailed overview of the economic assessment can be found in the report Site selection for centralized PHA compounding and processing > click here.

More information can be found in the report Site selection for centralized PHA compounding and processing > click here.

ECONOMIC COMPARISON

For the centralised solution with PHA accumulation, PHA extraction and PHA compounding at one wastewater treatment plant and transport of the primary sludge from other WWTPs, the transport costs are the highest. However, the

Figure 15: Production costs for PHA for a centralised solution (transport of primary sludge) compared to decentralised approaches providing dewatered respective dried PHA-rich biomass

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Circularity measurement and assessment of PHA production A holistic approach to quantify the economic, environmental, and social impacts of PHA recovery from primary sludge from WWTP’s can be achieved by means of a circularity measurement and assessment (CMA). This CMA process (based on a forthcoming international standard, ISO 59020) was undertaken for Scotland, one of the three NWE regions focused upon by the WOW Capitalisation project. It builds upon the technical, economic, and spatial analysis from WOW!. The CMA process accounts for all stakeholders in the PHA value chain and evaluates PHA production against alternative pathways: biogas production or disposal by incineration.

The findings provide a benchmark of PHA’s circular performance and evidence to compare it to traditional polymers, which it could replace as a more circular resource.

CIRCULARITY MEASUREMENT & ASSESSMENT FRAMEWORK

As illustrated in Figure 15, the CMA framework has three steps: (i) boundary setting; (ii) circularity measurement and data acquisition; and (iii) circularity assessment and reporting.

STAGE 1: BOUNDARY SETTING

The valorisation of PHA as a sewage by-product in Scotland represented the system that was studied, processing 2 million population equivalents (p.e.) of 3-5% primery sludge. The goal and scope of the study was to process 25,550 tons of P.S. (90% dried matter) per year as compared with incineration and replacing fossil-derived plastics (polyethylene, PE). Four scenarios representing centralised, decentralised, and standalone systems reflected different system boundaries and resource flows, with the embodied, transport and operational impacts evaluated for a 1-year period (for more information of scenarios). In addition, a system perspective was taken to ensure relevant factors were considered, from product to regional level.

STAGE 2: CIRCULARITY MEASUREMENT AND DATA ACQUISITION

Seven circularity indicators were selected for the evaluation of PHA, with one core indicator (lifetime of product relative to industry average) and six additional indicators (energy, economic and social factors). These indicators were selected based on PHA’s relevance to adding value to sludge by transforming it into a resource.

Formulae were defined to allow these indicators to be evaluated, considering the availability of primary and secondary data sources. Data was collated from WOW! results (TEA PHA report), and published literature sources.

The complementary LCA applied the ReCiPe impact assessment method, and all relevant SDGs were mapped to align PHA production with potential global impact. These methods were also considered as part of the comparison between offsetting PE use or reducing incineration.

STAGE 3: CIRCULARITY ASSESSMENT AND REPORTING

The comparison of resource flows between PHA as compared to a fossil-derived plastic i.e. PE, demonstrated the potential for PHA to be easily biodegradable or to have a similar lifespan to conventional plastics. Currently, the proportion of renewable energy for PHA production is 21%, reflecting potential to increase through more generation and energy recovery from non-renewable flows. PHA derived plastics require significant costs relating to infrastructure (embodied) and transport and energy (operational), with a stand-alone system more economically viable than centralised or decentralised scenarios.

However, PHA production is double that of using recycled plastic, and almost four times more expensive than virgin PE (€2,972 vs €920 per ton PHA). Ensuring living wage only adds 0.5% to the total unit cost.

The LCA results evaluated embodied, transport and operational burdens of PHA production. It identified the tanks as the greatest embodied impact, yet electricity and natural gas (for heating) represented the dominant impacts, reflecting 37-91% and 16-53% of the total operational burdens, respectively. The net impacts of PHA production highlighted the need for improvements when compared to biogas and incineration pathways. The EU sustainable developments goals mapping identified links to technical, economic, social, environmental, and social factors: #7 increasing the renewable energy share; #8 changing existing products on the market; #9 developing a new value chain in the region, #10 creating new regional jobs for this sector and #12 reduce the material footprint for the region.

The final CMA findings were mapped against stakeholder priorities, with PHA-producing com-

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Figure 16: Circularity Measurement and Assessment (CMA).

panies, local water authorities and policy-makers representing those who can benefit from PHA entering the commercial market. PHA producers can make informed investment decisions for infrastructure and energy sourcing. With local water authorities having increased knowledge of their resource assets, policy makers recognising how they can incentivise to make PHA a viable by-product from wastewater and divert sewage from biogas or incineration pathways.

CONCLUSIONS

lenges to make it a competitive product. Possible incentivisation is required until it is scaled to a level that is more cost-effective to produce. It requires this evidence to inform key stakeholders who can make decisions to support PHA as a circular resource.

More information on the results of the circularity assessment of PHA production can be found in the report: Circularity assessment of PHA production potential for one NWE region.

The conclusions from the CMA were that PHA has the potential to join the regional and European markets. However, its success relies on a complex mix of technical and non-technical chal-

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Future Challenges The Interreg NWE WOW! project provided many new insights in the production of PHA from residual streams and possible applications of this material. Are we ready for fullscale production? Definitely, we would say. Technically it is possible to produce PHA from residual streams on large scale. There are many applications where the properties of PHA such as biodegradability are an added value.

Last but not least, the market has a lot of interest in PHA. But of course there are also still some remaining challenges that need to be overcome to make fullscale PHA production a success in the long term. Some of these challenges are: Optimization of the PHA production process (VFA production, PHA extraction) in order to establish a wider application of PHA and a reduced price.

Possibilities to predict/model PHA production on different residual streams.

Defining the range of application for PHA and the looking into the possibilities to improve the properties and processability of PHA. A public understanding on the benefits of PHA and a broad public acceptance of bioplastics made from residual streams.

Do you want to be involved in tackling these challenges or do you have ideas on how to overcome these challenges? Do not hesitate to contact us.

“LET’S PAVE THE WAY FOR A MORE RESPONSIBLE AND SUSTAINABLE FUTURE WITHOUT FOSSIL BASED PLASTICS.”

MORE INFORMATION

IMPRINT

WWW.NWEUROPE.EU/WOW

PROJECT PARTNERS WORKING ON PHA

The WOW! project has been finished in October 2023. The project partners will keep continuing the research on PHA. More information about the project can be found on the website:

WOW! Interreg NWE White paper Production of PHA Bioplastic on side streams - © WOW! 2023 Re-use is authorised provided the source is acknowledged.

If you have specific questions please contact: Jappe de Best Professor Biobased Resources and Energy at MNEXT (Avans University of Applied Sciences) jh.debest@avans.nl For media inquiries, please contact the WOW! communications officer: Wendy van Rijsbergen w.vanrijsbergen@avans.nl

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REFERENCES

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