Biodegradable rope developed for greenhouse horticulture

At the end of the harvest period, many entrepreneurs in the greenhouse horticultural sector are forced to dispose of green waste as landfill waste. The reason: the rope present in the waste, which is necessary to grow tomatoes and other vegetables, and which is not compostable. The Applied Polymer Innovations (API) Institute is launching an organic-based, biodegradable alternative.

During cultivation, many vegetables have to be tied with strong ropes; it is indispensable for tomatoes, cucumbers and peppers, however, there is one disadvantage: they are usually made from polypropylene and therefore not compostable. For the grower this means that the rope cannot be disposed of as green waste, but must be manually fished out of the trash. A labour-intensive job, which is therefore only done by a few growers. The result is that many growers dispose of green waste as landfill waste, which entails an extra cost.

"Annoyance is a big word, but it always causes slight irritation," says Ron Peters, grower and owner of a test centre in Klazienaveen. About three years ago, he contacted API and explained them the problem. "I suggested to devise a biodegradable alternative to plastic rope, which is the one most commonly used in greenhouses."

Testing with weight

API started working on Ron Peters' idea. Bas Krins, director R&D at API: "It was obvious we would use PLA (polylactic acid), because we had already seen its qualities in other projects. We have developed a process to spin on a spinning machine to produce greater amounts of PLA yarn; from this we have made thread and then string."

The first tests with biobased rope were carried out by Ron Peters in Klazienaveen. Peters: 'We hung from the rope a similar weight to that of a full-grown tomato plant. We let it hang for a couple of months to see what would happen to the rope."

Among other aspects, it was examined how the rope 'responded' to changes in humidity and high temperatures. Conditions that are normal in a greenhouse, where the rope must remain in optimal condition.

Although API had obtained a fully biodegradable and biobased rope, and according to Peters it responded well to most of the tests, although it was found to be unsuitable for use in the greenhouse. After a few months, the rope was too sensitive under the load of the tomatoes, continuously stretching and not being able to return to its original position. Krins: "After some time, the rope lost its firmness. The PLA that we intended to use was consequently not ideal."

Bas Krins "Internally, we had already discarded the project. Until we found the PLA variant, we previously completely developed another application. After some intensive lab tests, it showed that there was virtually no problems with firmness, so we finally had something that worked. Moreover, the rope can now be disposed of as green waste. Legally, it must be biodegraded within 180 days," says Krins.

More expensive, but lower labour costs

The discovery was made about eighteen months ago. A lot of key work has gone into understand how to prevent the loss in firmness. In the meantime, the first tests in real greenhouses started in September. Krins: "The rope is used for a whole cycle for a few rows of tomatoes in the greenhouse. And it's a big greenhouse, so if something does go wrong, the grower will not be severely affected."

Although the rope is currently being tested on a greenhouse growing tomatoes, it is certainly also intended for use in other greenhouses. It is ultimately intended for everything that grows along a rope, so also for peppers and cucumbers."

In terms of cost, Krins sees an advantage for the longer term. "The purchase price is perhaps a little higher than ordinary rope, but it will certainly pay off. It saves the grower a lot by no longer having to take the rope out of the waste." Peters adds: "It may seem a small step, but for the grower this is a step forward. The sooner it comes on the market, the better."

Source: Agro-Chemie.nl

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