Trigger

Development of a Pea Starch Film with Trigger Biodegradation Properties for Agricultural Applications

The main objective was to develop an agricultural plastic film which would maintain its functional properties during its lifespan, and at the same time be able to break down quickly and effectively after harvest. The aim of the project was to develop a trigger to start and accelerate the biodegradation process just when the film has completed its work. This trigger must be activated independently of the crop, the type of soil and the climate conditions.

Trigger investigated two alternative approaches to manufacturing a film with a controlled biodegradation start and rate (trigger system).

• A film based on a biopolymer with a low biodegradation rate, incorporating a salt as a filler that will undergo an exothermal reaction on contact with water. During the lifespan of the film, the salt is isolated from water within the film, so rain or irrigation water cannot begin the biodegradation process. After the crop season, the film is ground, and mixed with the soil and water applied by specially adapted agriculture machinery. The filler then comes into contact with water, increasing the temperature and humidity of the film, accelerating its biodegradation process.
• A film based on a biopolymer with high biodegradation rate whose biodegradation activity will be initially inhibited by the addition of an antimicrobial additive and then promoted when required. Inorganic antimicrobials will be considered, keeping in mind that they must not be toxic (for the soil).

Initially, work focussed on both approaches. Later, the most technical, economical and environmentally viable solution was selected. The needs of the final users were determined to establish the biodegradable trigger fi lm requirements.

The R&D work focused mainly on the trigger systems, but also on the biopolymer made of pea starch, the compounding process, the film extrusion process and the system to initiate degradation, using specially adapted agricultural machinery.

Organisational Information

Budget: €2.8M
Funding: €1.55M
Start Date: June 2005
Finish Date: November 2008
Duration (in months): 42
Lead Partner (Co-ordinator): AIMPLAS, Spain

Participants

• AIC, UK
• ANCA, Italy
• CCI-Dobrich, Bulgaria
• GTV, Italy
• IFR, UK
• Iniciativas Plásticas SL, Spain
• La Unio, Spain
• NFU, UK
• Plásticos Montisón SL, Spain
• S A Enterprise, Bouillet, France
• SCA, Uneal, France
• Smithers Rapra, UK
• THOMSON, UK
• Wells Plastics, UK

Project Progress & Results

One of the major achievements has been to develop a new way of processing starch and monomeric plasticiser to give better properties than standard compounding techniques. This has given a pea starch based film, without chemical modification, that has good physical properties and biodegrades at a high rate, as both the starch and plasticiser are readily biodegradable. This starch compound may have a number of uses due to its low cost and renewable source.

For the specific application in this project, the triggering of the biodegradation has been achieved with a sandwich approach of protecting the starch layer with a thin outer layer of another biodegradable polymer. This was necessary for outdoor uses but may not be necessary for indoor uses.

Multi-layer pea starch films were successfully produced on a laboratory scale blown fi lm line, but scaling up to large production bubble diameters proved more diffi cult. However, the basic starch compound may be suitable for other applications and processing techniques, as well as single layer biodegradable film. Applications are being sought.

Project website: www.aimplas.es/proyectos/trigger