29 May 2012

The big forest biomass bonanza: inserting wood fiber into recyled plastics

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Andrea Lazzeri, University of Pisa, Italy, is investigating biomass’ applications from forest-derived materials

The biomass found in forests represents an abundant, renewable, and low cost resource that does not compete with food production. It can play an alternative role to petroleum derived-resources and thus reduce oil dependence.

The forest biomass represents an ideal source of biodegradable materials. Andrea Lazzeri, Associate Professor at the Department of Chemical Engineering, Industrial Chemistry and Materials Science at the University of Pisa, Italy, is investigating biomass’ applications as the co-ordinator of an FP7 project called Forest Resource Sustainability through Bio-Based-Composite Development, dubbed FORBIOPLAST. He shares his views on the future of forest-derived materials developed for the automotive, agriculture and packaging sectors.

What does FORBIOPLAST exactly do?
The idea of the consortium is to create the new materials from forest. This offers the advantage of not competing with agricultural land and of contributing to reducing the greenhouse effect. We extract our raw materials from the soil with a view that they will go back there at the end of their life cycle. Ultimately, they will be reabsorbed so that ,on that soil, a plant or a tree can be re-born.

One possible application involves producing polyurethane that is half-based on renewable resources. Another consists of creating recycled plastics for the automobile sector. We also looked into the field of biodegradable materials, including producing polyhydroxybutyrate (PHB) by genetically engineered bacteria, and polylactic acid (PLA) from corn. Finally, we worked on cellulose derivatives, particularly on cellulose acetate, a material that had been abandoned years ago in favour of the petroleum-based plastics. Now, it has regained interest not only because it comes from a natural resource but also because it is biodegradable.

What is the rationale for recycling pastics?
Often, it makes more economic sense to buy new plastic than recycled one. Indeed, there is not a big enough price difference between the recycled and the new plastic while recycled plastic’s mechanical performance is generally lower.  However, since the amount of plastics used in the automobile sector is massive, certain car manufacturers are committed to recycle as much as possible of the plastic they generate.

We have therefore found applications by which we can recycle and reuse the same plastic several times. This opens the door to make it an economically viable process. For example, we make recycled plastic from cars bumpers.  This can be used to produce parts supporting the weight of cars’ seats in order to reduce the weight and the power consumption.

How do you combine the biomass into the recycled pastics?
What is unique about our approach is that during the recycling process, we use wood fibres to give polymer waste a good mechanical resistance. These fibres are sourced from the waste of the furniture industry. They are significantly less expensive and have a much smaller environmental impact than glass fibres. The latter are traditionally used and require high temperatures and high-energy consumption.

We first treat the plastic bumpers to remove paint. Then, we grind them with mixers similar to kneaders and then we add the wood fibres, which look very much like sawdust. From this process we obtain the granular material that makes up our raw material.

We then worked on removing the need for some kind of additive to help both types of materials to remain together. This helps bypass the problem of additives currently used that are either expensive or have a high environmental impact. We have therefore developed specific enzymes capable of working on the wood fibre and making it compatible with the plastic.

This enabled us to produce plastic containers with a wood component. It has a wooden smell that is pleasant for applications such as plants containers. But it might inappropriate for applications in the food industry. We are now working to overcome the problem of smell.

What do you consider to be the most innovative aspect of the FORBIOPLAST proposal?
What is truly innovative in our concept is the recovery of recycled plastic, using source material whose precise composition is not specifically known. That’s because every car manufacturer has its own suppliers and each of them has its own secret mix of ingredients. This means that the final product is of variable quality. We therefore had to address the issue of product variability. The solution was to find companies able to separate various components of plastics well in order to obtain a fairly consistent product.

Another innovative aspect is the use of biodegradable polymers for structural applications, such as for materials with impact resistant, heat-resistant properties. The biodegradable plastics currently available are very fragile.  So we improved the polymers’ toughness while keeping them biodegradable. For instance we tried to make food containers such as ice cream cups, since those currently available have a limited heat resistance to protect the ice cream from being melted by the external heat.

In addition, we have also improved the biodegradability of the material for applications that require a soft material, such as agricultural containers designed to disappear completely within three to four months. Unlike previous technology, they do not require decanting before being disposed of. They can also be left in a type of soil such as that found in greenhouses.

Have you thought of other possible applications for this substances besides as for the packaging, automobile and agricultural sectors?
Yes, we used the biodegradable plastic to make containers for cosmetics, whose plastic is more difficult to recycle than that of the bumpers because it requires pre-washing of the cosmetics bottle. 
We are working towards ensuring that at the end of their life these containers can be thrown away together with the organic waste and become a good quality fertilizer as they return to raw material.

What remains to be done prior to commercialisation of your products?
Some products, such as the plants containers, are at prototype stage. We still need to make some testing to see whether, over time, the wood is likely to interact with the water from the paint. For some products, we also need a certification of biodegradability. This is delivered by the regulatory authorities, involves eight to nine months of tests and costs around €20,000.
 

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