A rising population combined with dcreasing availability of arable land means that food yields must improve - and plastic films can help to do this.

1. 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: basf
Films meet the challenge of
increased food production
Polyethylene films have made a substantial contribution The key drivers behind the development and use of Biodegradable
to the increase in agricultural production over the past agricultural films have been: extending the growing mulching film
50 years through the development of products used for season for crops; and raising the yield. With the growth is growing in
mulch, silage and greenhouse applications. AMI in world population, issues of food security and scarcity popularity
estimates 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 – and
the largest share of the market at 60%, with China the could even decline in future because of the effects of
world’s largest single market at around 1.5 million climate change – the world’s need for food rises
tonnes. However, Europe also makes significant use of inexorably. Improving yield is vital: by 2025, each
agricultural films, accounting for 19% of world demand. hectare of agricultural land may have to feed five people
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2. 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, 2010
12 film sheet EXTRUSION | April/May 2010 www.filmandsheet.com

3. Agricultural film | markets feature
sugar and developed by Telles (a joint venture between
ADM and Metabolix). These are aliphatic polyesters with
chemical resistance similar to PET. In tests, the mulch
film produced had completely degraded in soil by the
next growing season.
The demand for mulch films overall is expected to
continue growing although trends in downgauging will
limit the growth from a resin perspective.
Silage film
Silage film is used to conserve grass, maize or other
products under anaerobic conditions. The product is
often treated with ammonia to transform it into
feedstuff for livestock. Demand occurs primarily in the
Northern, cooler countries where there is greater need
for silage to feed livestock during the winter months. In
Europe, the UK and Scandinavia accounted for 45% of
silage stretch film production in 2009. Traditionally
silage was stored in clamps or bags before being used
as winter feed for animals. With the advent of silage A good film will also diffuse light, reducing plant Plastic
stretch 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 in
because if the seal fails the silage will go mouldy. UV infrared and allowing visible light to pass for photosyn- Guernsey, help
stabilisers are also important in the film to prevent thesis. to extend the
degradation. This application sees a significant demand In a new development, Plastica Kritis – a manufac- growing season
for high performance octene grades of linear LDPE, turer of agricultural films in Greece, France and China – and produce
such 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 can
showing strong growth as it takes share from non- be provided by surface migrating additives, which last
stretch 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 pest
from silage clamp entering the water course. In Europe, management and control within greenhouses, reducing
the decrease in agricultural subsidies in the dairy the need for the use of pesticides. Common problems
industry has reduced the need for silage. include aphids, white fly, thrips, powdery mildew,
viruses and bacteria. Insects act as vectors in many
Greenhouse effect cases, so preventing access for the vector can protect
This covers films both for large-scale greenhouses and the crop and reduce the need for pesticides. Blocking
for ‘polytunnels’ that are used for the protection and transmission of UV radiation has long been known to
generation 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 a
films, which offer savings in heating fuel, greenhouse study on lettuce in Spain carried out by the Spanish
construction and maintenance. These films have to be National Research Council (CSIC) and reported at AMI’s
highly sophisticated, combining high mechanical Agricultural Films 2009 conference, the aphid and silver
strength, durability, UV stability, antifogging and anti- Y moth infestation was found to be greatly reduced
drip 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 to
materials are now expected to last for five years: develop colour.
durability is affected by many factors including wind, Davis-Standard has developed versatile film
sun, temperature, effects of structural supports and production equipment to allow for seasonal variation in
surface coatings. Pesticides like sulphur can also have demand. Agricultural film ranges from 20 to 300
a big effect on the film – such as deactivating light microns thickness and up to 20 metres width, which
stabilisers. demands large extruders. This, in turn, means that
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4. 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- (js@amiplastics.com).
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