www.filmandsheet.com April/May 2010 | filM & sheet eXtRUsiON 11

Agricultural film | markets feature

Polyethylene films have made a substantial contribution

to the increase in agricultural production over the past

50 years through the development of products used for

mulch, silage and greenhouse applications. AMi

estimates worldwide demand for Pe films in agricul-

tural applications at 3.6 million tonnes. Asia holds by far

the largest share of the market at 60%, with China the

world’s largest single market at around 1.5 million

tonnes. however, europe also makes significant use of

agricultural films, accounting for 19% of world demand.

the key drivers behind the development and use of

agricultural films have been: extending the growing

season for crops; and raising the yield. With the growth

in world population, issues of food security and scarcity

are becoming increasingly important.

While the availability of arable land is static – and

could even decline in future because of the effects of

climate change – the world’s need for food rises

inexorably. improving yield is vital: by 2025, each

hectare of agricultural land may have to feed five people

films meet the challenge of increased food production

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

Biodegradable

mulching film

is growing in

popularity

Ph

OtO

: bA

sf

– compared with just two people in 1950.

Agricultural film can be divided into three catego-

ries: mulch film, greenhouse film and silage film.

Mulch betterMulch films are the largest segment, globally account-

ing for around 40% of the world market. They are used

in agriculture to raise soil temperature and conserve

moisture. Crops are able to grow in a modified environ-

ment, allowing plants to grow earlier and to a better

size and quality.

Pliant Corp estimates the US mulch film market at

70m lbs (32,000 tonnes). Around 20% is barrier film,

which is mainly used for pest control and is produced

from materials such as EVOH and nylon. Permeability to

fumigation gases is the critical property here, and can

vary with relative humidity – there are no official

standards at this time. Semi-permeable films include

an LDPE sandwich containing HDPE; virtually imperme-

able films (VIF) typically comprise an LLDPE sandwich

containing nylon.

Mitsui and Kuraray have teamed up to produce a

totally impermeable film (TIF) comprising a PE

sandwich containing two adhesive layers

(“Admer”) and a central layer of ethyl

vinyl alcohol (Eval), which provides a

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

for mulching have improved dramatically in

recent years following the introduction of linear low

density materials. Because linear materials have higher

tensile strength than conventional LDPE, mulch films

have been downgauged by up to 30%. The result is a

more cost-effective agricultural tool, and means

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

led to growing interest in the development of

biodegradable varieties that would break down in the

soil after use. The key issue is attaining the right

balance between durability and biodegradability. The

mulch film needs to last as long as the crop: if it breaks

down too early, the film sticks to the crop and damages

it – and also fails to protect it from weeds. Other issues

revolve around its cost, and questions over residues in

the soil. Although biodegradable films can be up to four

times more expensive than conventional films, suppli-

ers argue they are cost competitive because their use

avoids the cost of collection, transport and recycling.

In Europe standards such as EN 13432 are currently

in force, but stricter ones are being developed for

agriculture such as NF U 52001, which looks at the

degradation of the film in the soil.

Various companies are developing films based on

different sustainable feedstocks. Biolice, developed in

France by Limagrain Céréales, is made directly from

cereal flour rather than starch. In tests, Biolice film was

compared with PE film and average temperatures in

mulch were the same. It has been used in short-term

crops such as maize, cotton and salad; longer term

films are under development for tomatoes and melons.

Mirel is another type of bioplastic – made from corn

Figure 2: global agricultural

Film demandby type

Source: ami conSulting, 2010

Figure 1: diStribution oF

worlddemand For

agricultural FilmS 2009

Source: ami conSulting, 2010

FILM & SHEET EXTRUSION | April/May 2010 www.filmandsheet.com12

markets feature | Agricultural film

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 filmSilage 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

stretch film the market was transformed in many

European countries.

It is vital that silage film does not get damaged –

because if the seal fails the silage will go mouldy. UV

stabilisers are also important in the film to prevent

degradation. This application sees a significant demand

for high performance octene grades of linear LDPE,

such as Dow Chemicals’ Dowlex.

Trends in this sector are varied. Silage stretch film is

showing strong growth as it takes share from non-

stretch clamp and bag silage films. Another factor is

increasing legislation to prevent agricultural run-off

from silage clamp entering the water course. In Europe,

the decrease in agricultural subsidies in the dairy

industry has reduced the need for silage.

Greenhouse effectThis covers films both for large-scale greenhouses and

for ‘polytunnels’ that are used for the protection and

generation of a ‘greenhouse effect’ for cultivating crops.

A wide variety of crops are now grown using these

films, which offer savings in heating fuel, greenhouse

construction and maintenance. These films have to be

highly sophisticated, combining high mechanical

strength, durability, UV stability, antifogging and anti-

drip effects, thermic effects and disease and insect

control. Expectations are growing and greenhouse

materials are now expected to last for five years:

durability is affected by many factors including wind,

sun, temperature, effects of structural supports and

surface coatings. Pesticides like sulphur can also have

a big effect on the film – such as deactivating light

stabilisers.

A good film will also diffuse light, reducing plant

damage and reflecting some near infrared to offer a

moderate cooling effect. BASF has developed its

Lumogen IR 1050 additive which works by reflecting

infrared and allowing visible light to pass for photosyn-

thesis.

In a new development, Plastica Kritis – a manufac-

turer of agricultural films in Greece, France and China –

found that aluminium particles can be added to

increase the cooling effect. Anti-dripping properties can

be provided by surface migrating additives, which last

around 24 months.

UV-absorbing materials can be used in pest

management and control within greenhouses, reducing

the need for the use of pesticides. Common problems

include aphids, white fly, thrips, powdery mildew,

viruses and bacteria. Insects act as vectors in many

cases, so preventing access for the vector can protect

the crop and reduce the need for pesticides. Blocking

transmission of UV radiation has long been known to

reduce the number of insects as it affects their flight

behaviour. It also reduces sporulation of fungi. In a

study on lettuce in Spain carried out by the Spanish

National Research Council (CSIC) and reported at AMI’s

Agricultural Films 2009 conference, the aphid and silver

Y moth infestation was found to be greatly reduced

through the use of UV-absorbing nets. One disadvan-

tage is that some ornamental plants need UV light to

develop colour.

Davis-Standard has developed versatile film

production equipment to allow for seasonal variation in

demand. Agricultural film ranges from 20 to 300

microns thickness and up to 20 metres width, which

demands large extruders. This, in turn, means that

Plastic

greenhouses,

such as these

ones in

Guernsey, help

to extend the

growing season

and produce

larger crops

www.filmandsheet.com April/May 2010 | FILM & ShEET EXTRUSION 13

Agricultural film | markets feature

temperature control and cooling are key factors.

Greenhouse film needs good bubble stability because of

the large size and often short lengths are needed

(200m) to make the film easier to handle in the field.

Winding is another challenge.

The main markets for greenhouse film are the

Mediterranean area and China, Korea and Japan –

where they help to extend the growing season. Accord-

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 informationThis article is based on presentations made at AMI’s

Agricultural Films 2009 conference held in February

2009 in Barcelona, Spain. Agricultural Films 2010 will

take place on 22-24 November 2010 at the Fira Palace

Hotel in Barcelona. Companies interested in present-

ing a paper or attending (or in copies of proceedings

from last year’s event) should contact Jenny Skinner

(js@amiplastics.com).

Worldwide

demand for PE

films in

agricultural

applications is

around 3.6

million tonnes,

says AMI

markets feature | Agricultural film

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