MATERIALS | AGRICULTURAL FILM
Right:
Novamont says that using its mulch films have helped to improve rooting systems in many plants
a white external layer. One formulation used 55% Flexus 9211 (a metallocene LLDPE), as well as an LLDPE butane grade and a masterbatch to incorporate pigments and additives. Some of the advantages were: a 30% reduction in weed killer costs; a similar reduction in water consumption; and improved yields on the first commercial harvest. In similar fashion, Australia-based Hydrox
Technologies has developed a solar reactive mulch film that helped to improve yields of melons – among other crops. Rob Trenchard, a director at the company, told
delegates that farmers usually shy away from mulch film because it is expensive – both to buy and dispose of – difficult to use, too thick and can cause damage to plants (such as when it flaps in the wind). One melon farmer trialled the use of Solar Shrink film – which had much higher strength in the machine direction than traditional mulch film, as well as being thinner. It also ‘tightens’ in the sun, so will remain more tense when in place. Overall, the farmer saved around 12% in film costs, cut the use of film by 31,000kg and saved fuel and labour costs by applying the film to the land around 15% faster. “He also saved around 10% on seasonal dispos- al costs,” said Trenchard.
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Mulching is of vital importance in agriculture
Degradable advantage Novamont of Italy said that its biodegradable mulch film has helped to boost crop yields while reducing the job of collecting film at the end of the growing season. Agricultural waste accounts for around 5% of all plastic waste, said the company – and mulch films are generally difficult to recycle because of their high level of impurities. For this reason, degradable films can help to overcome this. The company says that its Mater-Bi mulch film has
helped to boost the growth of a variety of crops, including tomato, asparagus, rice and grapes. “For some crops, like rice and grapes, mulch film is impossible to remove at the end of the crop cycle,” said Novamont’s Sara Guerrini. Tomatoes, for instance, had better-developed
root system and higher yields when using Nova- mont mulch film, while it cut the need for weed control in asparagus. In vineyards, the film had the effect of boosting
rooting systems compared with conventional PE film (or bare soil), while vines under Mater-Bi mulch were harvested 17 months after planting – around one year faster than those planted on bare soil. Repsol of Spain has also developed a biode-
gradable mulch film – in this case, by incorporating an enzyme into the material. Under specific condi- tions of moisture, bacteria and temperature, the enzyme triggers the break-up of the polymer chains. “These serve as a source of carbon and energy for bacteria already in the environment,” said Roberto Gómez Bernardo, polyolefins advisor at Repsol.
Soil samples Biodegradable films break down where they are, sidestepping the need for collection. However, some organisations have looked into what chemi- cal species accumulate in the soil as these films break down.
Sam Deconinck, deputy lab manager at OWS in
Belgium, said that not all the carbon in a biode- gradable polymer is converted into carbon dioxide – and that intermediate degradation products will enter the soil. “These cannot be quantified,” he said. In legislative terms, a biopolymer is classed as being ‘totally degradable’ if it biodegrades by 90%, he said. Some of the ‘unconverted’ portions
14 FILM & SHEET EXTRUSION | April 2018
www.filmandsheet.com
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