A new fully biodegradable plastic from tomato skin

di Chiara Catgiu

A new fully sustainable and biodegradable plastic has been obtained from the tomato peel and it has been discovered starting from different projects and collaborations.

The EU-funded BIOPROTO (Bioplastic production from tomato peel residues) project main objective is in fact the fabrication of bio-plastics from the tomato fruit peel residues. They are an abundant and inexpensive waste from processing tomato industries rich in polysaccharides (chiefly cellulose, pectin and hemicelluloses) and lipids (soluble waxes and a non-soluble long- chain biopolyester named cutin). Specifically, the project is focused on the bio-mimicry of the plant cuticle that is the protective and outermost membrane that covers the plant epidermis of parts of plant organs exposed to air.

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The main aim in this project, the production of plant cuticle-like plastics has been divided in two: first, the synthesis and characterization of plant cuticle-like polymers from model substances and, second, the production of tomato peel plastics. These agro-wastes have been chosen because they have an elevated amount of cutin and the crop of tomatoes is an important business in the sector of the agriculture.

The European tomato processing industry processed 11,380,100 tonnes of raw tomatoes in 2004. Italy is by far the most important producer of processed tomatoes in Europe with a 53% share of European production followed by Spain (22%) and Portugal and Greece (10% each). Other minor producers include France and some of the new member countries, in particular Hungary and Poland. Nowadays, this inexpensive sub-product, tomato pomace, is used as animal feed.

Since the beginning of the project, different approaches have been developed to produce these new bio-plastics, Basically, they have consisted of a chemical synthesis in a very strong acid medium, a self-assembly process in water and diverse green and soft industrial processes. Also, a comprehensive study of the refinery of the tomato fruit peel residue from a perspective of IR and Raman spectroscopies has been carried out. On the other hand, interestingly, a new set of films and coatings from the lipid fraction of plant cuticles has been produced and characterized.

Despite the inherent difficulty of the combination of polysaccharides and lipids, main results achieved so far are ascribed to the development of a scale-up process for the fabrication of lipid- cellulose materials (bio-plastics) with potential applications in food packaging. Additionally, the critical reviews on IR and Raman features of plant cuticles has generated significant interest among specialists in the field.1

Another interesting and similar research project is taking place at the Italian Institute of Technology in Genova, Italy, in collaboration with the Centre for Scientific Research of Spain and the University of Malaga.

“It takes up to 4 years of research to get a product ready to be launched on the market – says Athanassia Athanassiou, IIT researcher and manager of the Smart Materials research group – taking inspiration from nature we have reproduced in the laboratory a biocompatible, biodegradable plastic coating 100% obtained from pepper and tomato peel and which retains the properties of the original product.“ 2

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Natural occurring polyhydroxylated fatty acids from tomato peels are excellent raw substances for the fabrication of different materials such as free-standing films, cellulose composites and coatings for cans.

They can be easily polymerized, by using a solvent-free melt-state process in very short times. The resultant materials shows a high hydrophobicity, good water and oxygen barrier properties, low opacity values, full biodegradability, and high adhesion to different metal substances.

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The main potentially exploitable markets are packaging, paper industry, textile industry, health care and food industry.

The same project developed at the Centre for Scientific Research of Spain and the University of Malaga aims instead at exploiting the natural viscoelastic properties of tomato peel, as well as its waterproof nature and protection capacity against other liquids, as well as parasites; a discovery that could also in principle be extended to other vegetables, such as bell peppers. However, scientists have prioritized tomatoes, particularly because the industry tends to discard the peel, which is usually discarded after the tomatoes are peeled for canning.

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The Professor of biochemistry Antonio Heredia and the scientist José Jesús Benítez, co-authors of the research study of the IIT, have worked with various kinds of vegetables until this discovery was made and patented. The most notable development from an environmental standpoint, also in this case, is the minimal impact that this use of the peel has, with the plastics produced being also biodegradable in the short term.

In this research, through a process of in vitro depolymerization, the original tomato polymer degrades its monomers and is polymerized again through chemical reactions to obtain a “plastic”

that has the properties of the shell of vegetables, but whose size or thickness can be shaped to meet specific needs.

Also here, in terms of industrial applications, trials have aimed primarily at coating aluminium cans containing beverages with imperceptible nanolayers in some cases. 3

Currently, petroleum-derived products are used to prevent drinks from coming into contact with the aluminium. Some of these components are banned for use in products for children; a problem which could be solved with these new fully sustainable alternatives.

The potential impact on society of this new material is threefold: first, these new bio-plastics are biodegradable with no adverse effects on the environment. Secondly, an inexpensive agro-waste (tomato peel) with costs to be removed is recycled and used as raw material. Last but not least, the fabrication of these bio-plastics and the use of tomato peels could generate new business and employment opportunities in the future.

1 http://cordis.europa.eu/result/rcn/190641_en.html

2 J. Heredia-Guerrero, J. Benítez, P. Cataldi, U. Paul, M. Contardi, R. Cingolani, I. Bayer, A. Heredia and A. Athanassiou, “All Natural Sustainable Packaging Materials Inspired by Plant Cuticles”, Advanced Sustainable Systems, 2017, 1600024

3 http://www.freshplaza.com/article/140244/Tomato-peel-transformed-into-biodegradable-plastic

Materials for the Circular Economy

di Chiara Catgiu

A linear economy, that extracts resources at increasing rates, according to the principles of take-make-dispose, without consideration of the environment in which it operates, cannot continue indefinitely. The concept of a circular economy promises a way out. Here products do not quickly become waste, but they are reused to extract their maximum value before safely and productively returning to the biosphere.1

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Materials play an essential role in circular economy. By designing products with materials that come from, and safely flow, into their respective nutrient cycles, they can be part of creating an optimized materials economy that eliminates the concept of waste.2

Not long ago, materials selection was considered a small part of the design process. The selection of a material for a specific purpose is a lengthy and expensive process. Approximately always more than one material is suitable for an application, and the final selection is a compromise that brings some advantages as well as disadvantages. Material selection is an interdisciplinary effort and it often requires different fields of study such as material science and engineering, mechanical engineering, industrial engineering and other experts in the field of application.3

Schermata 2017-07-14 alle 21.05.03Traditionally, materials selection for the design of facilities is based on economic and technological considerations, given the desired life span of a facility and the program of requirements and codes it must meet.

In design environments where ecological, health, and ethical impacts are increasingly important, often the only way to choose from many different material alternatives is by relying on experience and observation. In selecting materials, designers have to take into account a large number of factors, including sustainability, durability, recyclability and materials impact on environment.

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A sustainable material or a sustainable resource is something whose production is supported indefinitely by nature, which means, a resource is used up at the same speed that it is renewed. From the moment the raw materials are extracted to the moment the final product is disposed of, there must be no permanent damage to the environment.4

By integrating environmentally sustainable materials into design projects, it is possible to significantly reduce environmental impacts through less energy consumption, less natural resource depletion and pollution, plus less toxicity for both the occupants and the entire ecosystem.

These both minimize the negative impacts on the environment and occupants whilst maximizing positive impacts over the lifecycle of a design facility. But little research has yet focused on designers’ choices of sustainable materials and those that have demonstrated on the whole that sustainable materials selection is not a priority.5

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The circular economy illustrates a model, by operating in many different ways, which suggests:

  • Tight inner circles where minimum new materials are used before materials can be re-used, refurbished or re-manufactured. Such products offer the greatest savings in terms of embedded costs, materials, energy and labor. They also offer the greatest savings on environmental effects or externalities such as emissions to air, land or water, including reducing greenhouse gas emissions;
  • Circles of use where the number of times materials can be used through consecutive circles is increased. Re-use, remanufacture or recycling is used to achieve this objective;
  • Cascade use, where materials are recovered, re-engineered and cascaded into new uses from that originally envisaged. Good examples are recovered plastics used as insulation materials rather than packaging or cotton cascaded into a series of uses once it is no longer suitable for recovery and re-use in clothing;
  • Pure circles, where uncontaminated materials are returned for re-use in primary manufacturing. 6

This type of research will continue, as society understands the potential to use secondary materials from waste as a primary source for new design products, in a completely circular economy model.

E. M. Foundation, “Towards the Circular Economy,” 2013.

E. M. Foundation, “The Circular Design Guide,” 2016.

A. Jahan et al., “Material Screening and Choosing Methods – A Review,” Materials and Design, vol. 31, pp. 696–705.

M. F. Ashby, “Materials Selection in Mechanical Design”, Third edit. 2005.

C. S. Hayles, “Environmentally sustainable interior design: A snapshot of current supply of and demand for green, sustainable or Fair Trade products for interior design practice”, International Journal of Sustainable Built Environment, vol. 4, pp. 100-108.

ISWA, “Circular economy: trends and emerging ideas”, 2015.