UA new material that allows the development of biodegradable packaging for use in agriculture is another patent recently filed by researchers from the Institute of Chemistry (IQ) at Unicamp. The new product mixes with the polymer polyhydroxybutyrate-valerate (PHBV), produced from the fermentation of bacteria, a component produced from paper industry waste called lignosulfonate. The expectation, according to the research authors, is to make available to rural producers, for example, packaging for transporting small seedlings, which could be buried in the ground along with the plant.

Nelson Duran and doctoral student Ana Paula Lemes, at IQ: biodegradable, low-cost packaging capable of feeding the plant with the gradual release of nutrients

In addition to offering a highly competitive cost, the new product contributes to preserving the environment by using renewable raw materials. “The search for alternatives that minimize environmental damage is a global trend that is increasingly studied”, states one of the authors of the work, professor Nelson Duran. He signs the patent “Biodegradable composites based on poly(3-hydroxybutyrate – co-3-hydroxyvalerate) and lignosulfonates” with doctoral student Ana Paula Lemes and professor at the Faculty of Chemical Engineering (FEQ), Lúcia Innocentini-Mei.

PHBV is an originally Brazilian biodegradable polymer, which has been on the market for around two years. The biggest revenue, however, comes from exports to countries in Europe, Japan and the United States – on average, between 50 and 60 tons per year. Paper industry waste (lignosulfonate), due to its peculiar properties, has a wide range of applications in agriculture. The challenge of mixing these two materials, creating a new product, ended up enhancing the biodegrading effect of PHBV over time. In the laboratory, scientists deposited the compound in pots with portions of soil, in order to simulate degradation conditions. “After 50 days, we already noticed significant biodegradation, easily noticeable”, celebrates Ana Paula. The data were compared with those attributed to natural biodegradation of PHBV. While the polymer had a mass loss of 8%, the formulation with lignosulfonate lost around 30% in the same period.

The effectiveness of the new product could also be measured by the capacity for controlled release of micronutrients to the plant. Ana Paula explains that lignosulfonate has chelating power, that is, the substance is capable of “sequestering” several metallic ions such as iron, zinc, copper, manganese, magnesium and others, leading them to the formation of soluble metallic complexes. With this, it is able to transport metals to the plant in the form of micronutrients and in a gradual manner. “If the plant needs iron, for example, the metal can be added to the material’s formulation so that it is released into the soil during the biogradation of the packaging, thus being used by the plant”, she explains. The method would also avoid waste, reducing the amount of micronutrients needed, and reduce the risk of contamination of surface and groundwater.

The search - Coming up with a mixture that showed positive results in terms of thermal and mechanical properties took two years of research. It was necessary, like Ana Paula, to achieve compatibility between the substances. PHBV is hydrophobic, while lignosulfonate is hydrophilic. Therefore, it is common to observe in the literature the need for compatibilizing agents in multi-stage formulations. In this sense, the difference in the research was the production of a compatibilizer during the process to reach the material. “We changed the process, which resulted in the elimination of one of the steps. This means less energy and time consumption”, informs Nelson Duran. Ana Paula Lemes adds that research using mixtures of substances to achieve a biodegrading effect is not uncommon, but the use of the PHBV polymer is still very small in Brazil.

Studies have also improved the effectiveness of lignosulfonate application in agriculture. Due to its solubility, it does not remain in the soil for long, especially during rain, when nutrients are washed away with the water. Added to the biodegradable polymer, the lignosulfonate would remain in the soil for a longer period, contributing to the good development of plantations.