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Biodegradable mulch films replace plastic in the field

Fighting weeds is a headache for all farmers. Plastic mulch films are often used to limit weed growth; however, lifting the used plastic at the end of the growing season is labour intensive. The solution to this is compostable cellulose films that can be ploughed directly into the soil after use.

Mulch film is used globally in agriculture to limit weed growth and prevent the soil from losing moisture and heat. These films are often manufactured from fossil-based materials such as polypropylene or polyester fibre. In Sweden, mulch films must be gathered in after use; however, in many countries they are simply left in the ground, leading to major environmental problems.

“Even when mulch films are taken up, small pieces of plastic remain in the soil. Plastic films are also difficult to recycle, being full of soil, moisture and plant matter. It is also a major, labour-intensive undertaking to pick them up,” says RISE project manager Tomas Johansson. 

Environmentally smart herbicides

The solution may well be to develop a biodegradable cellulose mulch film that can simply be left on the field without increasing the farmer’s workload or impacting on the environment, but maintaining the same level of quality as plastic-based films.

"The herbicidal effect is the important factor here. Limiting weed growth is the greatest problem; however, if it is possible to lay a film that is fossil-free and doesn’t need to be gathered in, there will be major benefits,” says Tomas Johansson.

There are also opportunities available to add further functionality to mulch films.

"As an example, we could add minerals, soil nutrients, seeds or natural insect inhibitors to the film to increase crop yield,” says Susanne Eriksson, project manager at Wargön Innovation, one of the stakeholders in the ENTIS bio-innovation project to establish locally grown textiles in Sweden, which gathers some 60 stakeholders from research institutes, higher education institutions, the public sector and businesses in a number of industries.

Mustn’t degrade too quickly, nor too slowly

Field trials were conducted with 10 films in 2017 and 10 different films in 2018. The challenge has been to identify a sufficiently durable, but not too durable, film – one that will be broken down by the following year, If the mulch film is able to withstand 90 days in the field, weed growth can be limited in the initial period and the crops will have a head start. When the growing season is over and the harvest is in, it should be possible to plough the film into the soil and by the following year it should have broken down.

"One result of the project is that we have now developed a somewhat thicker paper quality, with good tear strength and excellent coverage characteristics," says Tomas Johansson.

Plastics are being phased out in many areas of society and agriculture is no different; so, a high-quality fossil-free mulch film has great market potential.

“In various ways, the majority of the materials we have tested demonstrated good potential. At the tail end of the project, a number of stakeholders have expressed an interest and it is great to see that they appreciate the potential of the concept. I see a bright future for this product, says Susanne Eriksson.