Agricultural film | markets feature A rising population combined with decreasing availability of arable land means that food yields must improve – and plastic films can help to do this. Carole Kluth reports photo: basfFilms meet the challenge ofincreased food productionPolyethylene films have made a substantial contribution The key drivers behind the development and use of Biodegradableto the increase in agricultural production over the past agricultural films have been: extending the growing mulching film50 years through the development of products used for season for crops; and raising the yield. With the growth is growing inmulch, silage and greenhouse applications. AMI in world population, issues of food security and scarcity popularityestimates worldwide demand for PE films in agricul- are becoming increasingly important.tural applications at 3.6 million tonnes. Asia holds by far While the availability of arable land is static – andthe largest share of the market at 60%, with China the could even decline in future because of the effects ofworld’s largest single market at around 1.5 million climate change – the world’s need for food risestonnes. However, Europe also makes significant use of inexorably. Improving yield is vital: by 2025, eachagricultural films, accounting for 19% of world demand. hectare of agricultural land may have to feed five peoplewww.filmandsheet.com April/May 2010 | film sheet EXTRUSION 11
markets feature | Agricultural film Figure 1: recent years following the introduction of linear low Distribution of density materials. Because linear materials have higher world tensile strength than conventional LDPE, mulch films demand for have been downgauged by up to 30%. The result is a agricultural more cost-effective agricultural tool, and means films 2009 that rather than being used only for exotic crops – such as tomatoes or asparagus – mulch film is increasingly being used for field crops such as maize. Mulch film must be opaque – to prevent light reaching weeds around growing plants – and impermeable to conserve water, but it can be difficult to recover and recycle after use. This has Source: AMI led to growing interest in the development of Consulting, 2010 biodegradable varieties that would break down in the soil after use. The key issue is attaining the right balance between durability and biodegradability. The – compared with just two people in 1950. mulch film needs to last as long as the crop: if it breaks Agricultural film can be divided into three catego- down too early, the film sticks to the crop and damages ries: mulch film, greenhouse film and silage film. it – and also fails to protect it from weeds. Other issues revolve around its cost, and questions over residues in Mulch better the soil. Although biodegradable films can be up to four Mulch films are the largest segment, globally account- times more expensive than conventional films, suppli- ing for around 40% of the world market. They are used ers argue they are cost competitive because their use in agriculture to raise soil temperature and conserve avoids the cost of collection, transport and recycling. moisture. Crops are able to grow in a modified environ- In Europe standards such as EN 13432 are currently ment, allowing plants to grow earlier and to a better in force, but stricter ones are being developed for size and quality. agriculture such as NF U 52001, which looks at the Pliant Corp estimates the US mulch film market at degradation of the film in the soil. 70m lbs (32,000 tonnes). Around 20% is barrier film, Various companies are developing films based on which is mainly used for pest control and is produced different sustainable feedstocks. Biolice, developed in from materials such as EVOH and nylon. Permeability to France by Limagrain Céréales, is made directly from fumigation gases is the critical property here, and can cereal flour rather than starch. In tests, Biolice film was vary with relative humidity – there are no official compared with PE film and average temperatures in standards at this time. Semi-permeable films include mulch were the same. It has been used in short-term an LDPE sandwich containing HDPE; virtually imperme- crops such as maize, cotton and salad; longer term able films (VIF) typically comprise an LLDPE sandwich films are under development for tomatoes and melons. containing nylon. Mirel is another type of bioplastic – made from corn Mitsui and Kuraray have teamed up to produce a totally impermeable film (TIF) comprising a PE Figure 2: Global sandwich containing two adhesive layers agricultural (“Admer”) and a central layer of ethyl film demand vinyl alcohol (Eval), which provides a by type very effective fumigant barrier. Tests carried out in January 2009 in Argentina, on a pepper crop, showed that the methyl bromide fumigant dose could be cut by 50% due to the low permeability. It has good tear resistance (important for installation) and good overlap adhesion. Production and formulation of films Source: AMI for mulching have improved dramatically in Consulting, 201012 film sheet EXTRUSION | April/May 2010 www.filmandsheet.com
Agricultural film | markets featuresugar and developed by Telles (a joint venture betweenADM and Metabolix). These are aliphatic polyesters withchemical resistance similar to PET. In tests, the mulchfilm produced had completely degraded in soil by thenext growing season. The demand for mulch films overall is expected tocontinue growing although trends in downgauging willlimit the growth from a resin perspective.Silage filmSilage film is used to conserve grass, maize or otherproducts under anaerobic conditions. The product isoften treated with ammonia to transform it intofeedstuff for livestock. Demand occurs primarily in theNorthern, cooler countries where there is greater needfor silage to feed livestock during the winter months. InEurope, the UK and Scandinavia accounted for 45% ofsilage stretch film production in 2009. Traditionallysilage was stored in clamps or bags before being usedas winter feed for animals. With the advent of silage A good film will also diffuse light, reducing plant Plasticstretch film the market was transformed in many damage and reflecting some near infrared to offer a greenhouses,European countries. moderate cooling effect. BASF has developed its such as these It is vital that silage film does not get damaged – Lumogen IR 1050 additive which works by reflecting ones inbecause if the seal fails the silage will go mouldy. UV infrared and allowing visible light to pass for photosyn- Guernsey, helpstabilisers are also important in the film to prevent thesis. to extend thedegradation. This application sees a significant demand In a new development, Plastica Kritis – a manufac- growing seasonfor high performance octene grades of linear LDPE, turer of agricultural films in Greece, France and China – and producesuch as Dow Chemicals’ Dowlex. found that aluminium particles can be added to larger crops Trends in this sector are varied. Silage stretch film is increase the cooling effect. Anti-dripping properties canshowing strong growth as it takes share from non- be provided by surface migrating additives, which laststretch clamp and bag silage films. Another factor is around 24 months.increasing legislation to prevent agricultural run-off UV-absorbing materials can be used in pestfrom silage clamp entering the water course. In Europe, management and control within greenhouses, reducingthe decrease in agricultural subsidies in the dairy the need for the use of pesticides. Common problemsindustry has reduced the need for silage. include aphids, white fly, thrips, powdery mildew, viruses and bacteria. Insects act as vectors in manyGreenhouse effect cases, so preventing access for the vector can protectThis covers films both for large-scale greenhouses and the crop and reduce the need for pesticides. Blockingfor ‘polytunnels’ that are used for the protection and transmission of UV radiation has long been known togeneration of a ‘greenhouse effect’ for cultivating crops. reduce the number of insects as it affects their flight A wide variety of crops are now grown using these behaviour. It also reduces sporulation of fungi. In afilms, which offer savings in heating fuel, greenhouse study on lettuce in Spain carried out by the Spanishconstruction and maintenance. These films have to be National Research Council (CSIC) and reported at AMI’shighly sophisticated, combining high mechanical Agricultural Films 2009 conference, the aphid and silverstrength, durability, UV stability, antifogging and anti- Y moth infestation was found to be greatly reduceddrip effects, thermic effects and disease and insect through the use of UV-absorbing nets. One disadvan-control. Expectations are growing and greenhouse tage is that some ornamental plants need UV light tomaterials are now expected to last for five years: develop colour.durability is affected by many factors including wind, Davis-Standard has developed versatile filmsun, temperature, effects of structural supports and production equipment to allow for seasonal variation insurface coatings. Pesticides like sulphur can also have demand. Agricultural film ranges from 20 to 300a big effect on the film – such as deactivating light microns thickness and up to 20 metres width, whichstabilisers. demands large extruders. This, in turn, means thatwww.filmandsheet.com April/May 2010 | film sheet EXTRUSION 13
markets feature | Agricultural film ing the Spanish National Research Council (CSIC), more than 400,000 hectares of crops are now cultivated in plastic greenhouses in the Mediterranean, of which 80,000 hectares are in Spain. Demand for agricultural greenhouse film is expected to continue growing strongly as farmers of fruit and vegetable cash crops attempt to exploit the early market. However, the largest growth will occur in those markets where the films allow the profitable exploita- tion of previously unsuitable land. This means that the Mediterranean area, parts of the Middle East and Asia are expected to see strong growth for these types of films. More information Worldwide temperature control and cooling are key factors. This article is based on presentations made at AMI’s demand for PE Greenhouse film needs good bubble stability because of Agricultural Films 2009 conference held in February films in the large size and often short lengths are needed 2009 in Barcelona, Spain. Agricultural Films 2010 will agricultural (200m) to make the film easier to handle in the field. take place on 22-24 November 2010 at the Fira Palace applications is Winding is another challenge. Hotel in Barcelona. Companies interested in present- around 3.6 The main markets for greenhouse film are the ing a paper or attending (or in copies of proceedings million tonnes, Mediterranean area and China, Korea and Japan – from last year’s event) should contact Jenny Skinner says AMI where they help to extend the growing season. Accord- (email@example.com). T r a i n i n g Energy Management in Plastics Processing A Masterclass with Dr Robin Kent Thursday 3rd June 2010. Oak Tree Conference Centre, Coventry, UK • Evaluate and benchmark your company’s current approach to energy management • Learn practical tips for identifying and delivering real The painless way energy savings across your plant to cut costs and • Develop action plans for management issues, services, plastics processing and operations boost proﬁts • Discuss your plant with a leading expert in plastics processing and energy management All participants will receive • Help your company through the current economic crisis by cutting costs the painless way a free copy of Robin Kent’s Energy Management book “Dr Kent was an enthusiastic, dynamic, (normal price £90) knowledgeable and entertaining speaker” “Very practical approach and very relevant to my factory”click here for full Limited availabilitybrochure Places for this Masterclass are limited and are available on a strictly first-come, first-served basis. Act now to guarantee your place, and book before 7th May 2010 to receive a £50 discount.