The Aha! Moment

By Ruben Lenz

Polysaccharide chemist and President of Advanced Micro Polymers Inc.

About ¾ of the way through the project we were still struggling with the longevity of the film. Since the mulch film was based on polysaccharides, primarily starches, it was susceptible to being washed away in the rain. This was unacceptable. The mulch film had to last at least one season.

Everyone else that had developed a spray on mulch film was focused on making a film that duplicated the plastic mulch films that were used to cover the soil. They were based on different polymers. Usually synthetic polymers such as acrylates. Naturally, these polymers were not biodegradable and left residual plastic in the soil.

My concept was very different. The idea was to use the soil itself to create the barrier. So, the spray-on resin would simply be a binder that sufficiently linked the soil particles together to make a barrier against weeds, protect against erosion against the elements such as wind, and hopefully, lock in the moisture.

This meant that the polysaccharide resin would have to penetrate the top layer of the soil. At the time we didn’t know how deep it needed to go. But experiments showed that resin had to only go a few millimeters into the soil to be effective. Experiments also revealed that we could control the properties of the mulch film by how tightly the soil was bound together. We could go all the way to making it impervious to water.

During a previous project, I had developed a unique grafting technique that did not require the use of solvents or heavy metals. We had to answer two important questions: Would we be able to find a good graft that would prevent the film from being washed away in the rain? And would that graft co-polymer still be biodegradable?

We had to make the polysaccharide sufficiently resistant to water to prevent it from being wash away in the rain but still sufficiently miscible with water that it could be consumed and digested by the microbes in the soil.

Using my proprietary grafting technique, we grafted numerous polymers onto different polysaccharides and tested them. We had to make sure that they were fully biodegradable and that they would work at preventing weeds. This is where we ran into difficulty.

1. When we used synthetic polymers, as soon as we reached the point where the resin became water resistant the mulch film lost its ability to fully biodegrade and it lost its ability to properly bind the soil. It reverted back to becoming like a plastic sheet covering the soil. Something like what everyone else had made.

2. By using synthetic polymers we were not really being 100% true to our mission of reducing our reliance on petrochemicals.

Then came the aha moment!

Cellulose, was a polysaccharide that was water resistant and yet still biodegradable! But could we successfully tie the starches and the cellulose together in a way that would achieve our goals? The answer turned out to be yes.

Of course, it also turned out not to be as simple as that. When we linked the cellulose and the starch together before-hand, the mulch film lost its soil binding capacity. A quality that was crucial to the performance of the film. So, we had to design the Liquid Mulch in such a way that the copolymerization would happen after it was sprayed over the soil and after the starch had bound the soil. In addition, this had to occur at room temperature since we could not heat the soil to make it react.

By using the right naturally occurring catalysts, we not only got the starch and the cellulose to form a copolymer in situ, in the soil but also got it to properly bind with the soil. The condition was that the Liquid Mulch had to dry completely for the reaction to occur.

That is why the Liquid Mulch cannot be applied in the rain. It has to dry to bind with the soil and form the mulch film. Once dry, it will not be washed away by rain, it will not be blown away by wind, and it will make a barrier that is dense enough to prevent weed seeds from sprouting and taking root. Any seeds or plants that are in the soil before the Liquid Mulch is applied will grow through the mulch film and will thrive.