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Last December, specialists in the field of biowaste conversion into valuable bio-based products gathered together in the Biorefinery and Bioenergy Centre (BIO2C) of CENER in the framework of PERCAL project. The main aim of this appointment was to discuss around the exploitation of the organic fraction of municipal solid waste (OFMSW) as feedstock to develop intermediate chemical products at high yield and low impurity level with industrial interest.

In the EU over 100 million tonnes of municipal biowaste are thrown away each year. Currently 75% of this biowaste is landfilled or incinerated, causing major environmental problems, since biowaste produces greenhouse gases when it decomposes and contaminates soil and groundwater. Furthermore, landfilling of biowaste is against the principle of a circular economy and is a waste of nutrients, energy and potential resource for biobased products.

For that reason, specialists in the field met together last December 9th and 10th in CENER – National Renewable Energy Centre of Spain, for discussing around innovative solutions to transform OFMSW into high value-added products, using a cascade approach of valorization of this biowaste. Indeed, complementary routes to the bioethanol (current PERSEO technology) production are being developed. The three main pathways are focused on the one side on lactic acid to produce eco-friendly ethyl lactate solvents by reactive distillation from lactic acid & bio-ethanol to be used in cleaning products and inks, and hot-melt adhesives for cardboard and other non-food applications in combination with maleic anhydride by reactive extrusion. On the other side, on succinic acid as an intermediate building blocks to production of polyols for the polyurethane industry. And finally, on the production of biosurfactants by chemical and/or microbiological modification of protein and lipid fraction from remaining fraction of MSW fermentation, for its use in cleaning products. These promising routes to achieve the above mentioned objectives by the use of one or a combination of different technologies, are being developed in the framework of PERCAL H2020 project, coordinated by IMECAL.

Figure: Final products and intermediates produced in PERCAL project

The project is already on its last step, and the main outcomes highlighted during this last year have been related to:

• Despite the variation in composition, the chemical components of municipal biowaste are usually within a relatively short range of values. A concentration of 50-70 g/L of glucose was obtained after the hydrolysis of contained carbohydrates.
• The scale up of the process for lactic acid production reaching high yields and producing lactic acid with a purity over 90% and a stereo chemical purity of L-Lactic acid over 97% (wt) ready for being used later.
• Succinic acid-fermentation using a bacterial strain with a continuous feeding strategy showed high yields and productivities that could be further increased by cell immobilization.
• Lactic acid is used either for ethyl-lactate production by its combination with ethanol from fermentation; for low molecular PLA (poli-lactic acid) and PLA-copolymers; for hot melting adhesives by PLA grafting, regarding shear strength performs similar to reference standard in closing cardboard boxes in non-food applications and shows improvement in Molped and in Bingo cardboards.

In further detail, CENER is leading a workpackage and its research line is focused on biosurfactants production by valorising the bioethanol, lactic acid or succinic acid fermentation by-products in order to increase the recovery from the organic content of MSW. The hydrolysis, extraction as well as biosurfactant production is being carried out in CENER Biochemical Process Unit laboratory.

The OFMSW-derived ethanol fermentation by product tested by CENER in the framework of PERCAL project is being supplied by IMECAL. Once received, the material is characterized and subjected either to an enzymatic hydrolysis process or to lipid extraction. Interesting results have been obtained so far in relation to the amount of total available proteins and lipids from the fermentation by-product, accounting to more than 25% by weight. Consequently, these two recovered fractions can be further valorized through the production of biosurfactants by chemical or enzymatic pathways. In further detail also highlight that the produced biosurfactant has been successfully tested in detergent formulations, showing a similar performance compared to a commercial surfactant. Biosurfactant is a very interesting final product due to the growing market demand of this type of compounds, even more when considering the biological-renewable composition, accounting to approximately 95%, which is aligned with the increasing consumers environmental concerns. Besides, the techno-economic assessment is underway and will help to improve its optimization and further upscaling.

Since the project is on its latest phase, CENER is still working hard in the improvement of the biosurfactant production and its testing in detergent formulations during these last months of the project that have shown very positive results so far.

This project has received funding from the Bio Based Industries Joint Undertaking (JU) under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 745828. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and the Bio Based Industries Consortium. More information:  https://www.percal-project.eu/

IMECAL prepared the OFMSW substrate for the up-scaling of lactic acid production at ATB partner facilities. The 800 Kg of milled urban biowaste were sent in refrigerated conditions to Potsdam (Germany). This substrate will be used to produce  lactic acid for the provision of product samples in high amount and quality in PERCAL project.

So far, rigorous screenings have been carried out to select a specialized bacterial strain to produce lactic acid. The selected strain was then used to evaluate the hydrolysates of OFMSW (Organic Fraction of Municipal Waste) obtained by different sorting methods.

 Exciting results have been accomplished. The samples of OFMSW were proved to be great substrates for the lactic acid fermentation. Without the addition of any extra nutrients, the conversions from total sugars into lactic acid above 70% and the final lactic acid concentrations above 60 g/L have been achieved!

 Currently, experimental work to scale up the fermentation process is being carried out. During this stage the implementation and optimization of the downstream processes are also being performed.

Pilot scale 72 L lactic acid fermenter in ATB 

Here is a video (in German) about the project: https://youtu.be/-AmyDCtNoWw

Several OFMSW samples from the EU were fully characterized showing that despite the heterogeneity and variation in composition, the chemical components of biowaste are usually within a relatively short range of values. 

Pretreatment and enzymatic hydrolysis of biowaste were optimized for the production of the chemical intermediates developed in the project. A production of more than 85% of potential fermentable sugars present in the substrate was achieved by the hydrolysis process. 

Fermentation tests with different strains indicate that bioethanol yeasts, lactic acid and succinic acid bacteria are not inhibited and can effectively use the sugars from OFMSW hydrolysates to produce target bioproducts at high yields.

The PERCAL consortium met in the picturesque town of Potsdam, Germany, to discuss the advancements in the project development as well as determine the future steps of the process.

Highlights

The consortium studied the variability of Organic Fraction of Municipal Solid Waste (OFMSW) due to waste collection system, geographical location and the seasonality. The 10 selected samples of municipal solid waste showed that parameters such as the time and place where they were collected do not have very significant influence on the chemical composition of the material.

Among the 10 most interesting samples, 3 representative OFMSW samples have been selected to carry out further characteristic analysis, which will serve as a basis for selecting the feedstocks in the project. 

Additionally, the consortium has started three different types of pre-treatment with the aim of optimising the hydrolysis pre-treatment step.

Great progresses of the intermediate products have been achieved.

 Lactic acid, an intermediate product in the project, can now be produced from organic municipal solid waste streams feedstocks in at laboratory scale.  Also suitable raw material will be applied for lactic acid production via simultaneous saccharification and fermentation approaches using newly isolated strains. The centrifuged samples achieved high lactic acid purity. Moreover, preliminary screening in the microplates for lactic acid fermentation of new strains has been successfully carried out.

 YPAREX has joined the consortium bringing expertise in extrudable adhesive resins in multilayer applications. Yparex® is a product family of The Compound Company. The Yparex® portfolio consists of a full range of high-quality, high-tech tie-layer resins, coupling agents, and compatibilisers, that meet the demanding needs of customers in a broad range of application areas. 

Progresses of final products have been made.

The characterisation analysis done for the valorisation of fermentation by-products provides a wide overview about their main parts. They have been focused on the protein and lipid fractions since both are the main precursors for biosurfactants production.

 Lab tests to produce and purify lactide from lactic acid have been carried out as well as tests on productions of PLA and PLA-copolymers by reactive extrusion.

In the course of the work for the conversion (hydrogenation) of succinic acid to 1,4-Butanediol, the consortium focused so far on the improvement of the batch reaction systems. 

 We are 13 partners that have come together to bring the best of our expertise to achieve our goal of “Exploiting Municipal Solid Waste as feedstock to develop intermediate chemicals at high yield and low impurity”. We are developing Succinic Acid, Lactic Acid, and bioethanol. These intermediate chemicals serve for the production of highly valued products such as biosolvents, cleaning products, holt melt adhesives, polyols, biosurfactants and many more.

We progress every day and meet every six months to measure our results and strategically plan our next steps. For the 6^th month PERCAL General Assembly we met in Athens at the Agricultural University of Athens on the 17^th and 18^th of January. AUA leads succinic acid purification tasks and the environmental, regulatory and economic analyses’ activities. AUA also participates in the Microbial Conversions of MSW of succinic acid.

At the meeting, the partners revealed important progress within the project work packages. Here below you can see a list of the meeting highlights:

• We have a new partner

YPAREX is joining the consortium bringing expertise in extrudable adhesive resins in multilayer applications. Yparex® is a product family of The Compound Company. The Yparex® portfolio consists of a full range of high-quality, high-tech tie-layer resins, coupling agents, and compatibilisers, that meet the demanding needs of customers in a broad range of application areas. 

• Bioproducts requirements were presented

Within the tasks in the WP1 related to characterisation, handling and pre-processing of Municipal Solid Waste, the requirements for the selected products were discussed. We will produce bioethanol, Lactic Acid, Succinic Acid and Surfactants for the window cleaners, printing inks, PLA, polyols, and polyolefins.

• Food waste recipes and real MSW

The consortium is looking at the best waste methods in order to analyse the optimisation of the processes. As of now, partners have sent waste samples from various countries as the project requires the testing of real MSW which comes mainly from food, kitchen as well as garden and park waste.

• Initial fermentation for microbial conversions to lactic acid

Trials have been carried out showing good performance of the process. After 10 hours of fermentation, the maximum values expected were achieved. Other alternatives are being tested and considered.

• Initial sugar concentration achieved for microbial conversions to succinic acid

The current work is determining factors that affect succinic acid extraction. Initial tests on sugar concentration were carried out for all strains.

• Initial analysis of fermentation by-products to produce biosurfactants

Calculations and required amounts of each fermentation by-product to produce biosurfactants started in February 2018

• Video and other dissemination, communication and exploitation activities

The first PERCAL video together with promotional material were produced at the beginning of the project (watch our video here). Initial activities to analyse the potential of our processes have begun.

• ...and our next meeting is coming on 3rd and 4^th July.

We will be visiting Potsdam in Germany where our partner ATB will host our General Assembly. The Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB) as a nationally and internationally acting institute is researching the interface of biological and technical systems. In PERCAL, ATB is leading the microbial conversions of MSW to lactic acid.