The Future of Wrap Developments

2 March 2009

Approximately 0.5 million ha of UK grass silage are scheduled to be wrapped into 33 million big round bales this year, requiring 30,000m tonne of film, and between 70% and 80% of the work will be carried out by contractors, explains Volac’s Jeannie Everington.

As tractors and wrappers  become faster and more efficient,  global research is leading to the development of a new generation of wrap which enables these machines to show their true potential and allows farmers and contractors to realise the benefits of these new technologies. New generation wrap is also meeting the challenges of economy and reduced environmental impact, factors which are becoming increasingly important, if not paramount to its future development.

The introduction of  pre-stretched wrap is among the latest successful developments. An in-line film manufacturing process has been developed which in combination with novel raw material mixes has enabled the film’s performance to be improved. The film is thinner, so uses approximately 24% less wrap per bale than conventional film, a figure that would amount to a massive saving of 7,000 tonnes of film, if conventional was swapped for the new product in all UK baling operations. As an alternative, bale wrappers are emerging which stretch conventional film further, up to 85%, before it is wrapped around the bale, giving the same end result of less plastic per bale.

Although pre-stretched film is thinner, trials demonstrate that it performs just as well, if not better than standard film. Take research findings at the Swedish Agricultural University, one of the leading international institutes for bale silage studies, where conventional film was compared with Volac Topwrap 2000 one of the new generation pre-stretched films and the various performance parameters were put to the test. The findings demonstrate that thinner film can be used to replace standard wrap with equal success in terms of forage quality and that the ability of the film to create an air-tight seal is almost 25% better. See table 1.

Table 1: Pre-stretch v Conventional film:

        Source: Swedish Agricultural University

So how does it work?  This is a film that is subjected to an extra stretch during manufacture.  Imagine that plastic has a memory.  After stretching, the molecules want to return to their pre-stretched state; they ‘remember’ their original positions and this is what causes bale wrap to shrink back on the bale.  After passing through the pre-stretch unit on your wrapper, film that has already been given a stretch during manufacture will shrink back even further, giving a tighter cling and excellent air-tight seal. 

To the future biodegradable films are also coming under the microscope, however so far their progress has been disappointing, simply because they are very difficult to control. Once the biodegradable film covers the silage and is exposed to the elements, it starts to degrade and consequently the forage is exposed to air and is destroyed; it is very hard to manage the process.

The ultimate ‘green’ wrap for the future could feature a ‘bio’ source as a substitute for oil, which is currently used to make polyethylene, the major ingredient for stretch film. Possible bio-sources may be the agricultural or forestry industries. So far, there are limited amounts of a green polyethylene product available, but it is still at the research stage. Green polyethylene technology ticks the boxes as far as reduced environmental impact is concerned, however it will require further development for cost to become competitive and to make significant volumes available.

-ends-

Back to news