Sensorization. The UPCT Materials Science and Metallurgical Engineering group, supported by the Seneca Foundation, is developing a system to timely remove excess sulfur from greenhouse decks to extend life
As a polluting element, plastic is one of the major ones when it comes to seas and oceans. Not only does its accumulation affect marine flora and fauna, but so-called microplastics have increased their presence until they reach the food chain. Faced with this problem, two paths are open: to reduce their use and to extend the life of these materials, so that it has an impact on the reduction of waste.
With regard to the latter aspect, and taking into account the use of plastics in a sector such as the fruit and vegetable sector, here is a point for improvement that has attracted the attention of the Materials Science and Metallurgical Engineering group of the Polytechnic University of Cartagena ( UPS). ).
The problem starts with the accumulation of sulfur on the greenhouse roofs. The fact that this powdered or sublimated sulfur is more present is due to the restriction of pesticide use in the fruit and vegetable industry, making it one of the few treatments allowed against fungal diseases, such as powdery mildew. For this, the sulfur is placed in bowls through the greenhouse that sublimate the sulfur by heating. The problem is that this sulfur can reach the greenhouse roof through evaporation and its accumulation affects the stabilizing additives contained in these plastics. These additives are responsible for the fact that sunlight does not break down polyethylene. That is why sulfur seriously shortens the life of this plastic.
Thus, under the leadership of María Dolores Bermúdez, the group adopted the idea proposed by one of its main collaborators, the Technological Center of Footwear and Plastics of the Region of Murcia (Cetec), to prevent the degradation of these greenhouse plastics. –formed by a polymer called low-density polyethylene– and started developing the project ‘Optical polymeric sensor of accumulated sulfur contained in thermoplastic matrices with applications in plasticulture’. Despite having no direct links with the primary sector, the group has always worked in lines of research aiming at extending the life of materials, from their study and industrial production, with longstanding partnerships with Cetec and companies in the region dedicated to the manufacture of greenhouse plastics with the highest production in the entire national territory. “There is great interest from this sector in offering products with greater sustainability, due to the impact plastic has on the environment. Cetec has long had lines of research and collaborations with companies in this area and suggested to us to develop this product,” says Ramón Pamies, Professor of the Department of Mechanical Engineering, Materials and Production at the UPCT.
The research team is rounded off by Francisco Carrión (university professor) and Pablo Martínez (scholarship holder of the Seneca Foundation), in addition to Alejandro Arribas and Fuensanta Monzó, employees of Cetec.
The project had to be characterized by its simplicity, i.e. no complicated installation was needed to solve this problem. So they focused their efforts on making an indicator sheet that would adhere to the plastic cover and be sensitive to the presence of excess sulfur, making a daily observation.
At the moment there is no commercial product that has this function, but the entire cover is replaced when degradation of the greenhouse is observed.
The process is as follows. The elemental sulfur that reaches the greenhouse roof in the form of a gas is oxidized by contact with the air and turns into SO2 and SO3, gases that, in contact with ambient humidity, are converted into sulfuric acid that reacts with the stabilizers of the greenhouse roof. .
So they use a material that is able to absorb moisture to which they add some chemicals (acid-base indicators) that change color depending on the pH, and act as a sensor to which they can easily relate the amount of sulfur which has evaporated and deposited on the plastic. “In this way it is possible to determine whether excess sulfur is applied to the crop and to remove this element from the scales until the sensor changes color again,” explains Ramón Pamies, adding that they had to try different materials to adjust the adjustment. to suit. one that can absorb enough moisture from the environment.
“With the flasher combinations that we have designed, we have created a kind of sulfur ‘traffic light’. If the sheet is green, we are in optimal working conditions. If it turns an orange color, the correct sulfur values are exceeded. If it is red, the cups should be removed as soon as possible,” explains the researcher.
The reduction in sulfur will improve the stability of the cover plastic’s additives, reducing degradation and extending the average life of the plastic.
Through accelerated aging studies, the research group estimates that they will extend the life of the greenhouse from three to five years. This represents an important technological advancement, as greenhouse horticulture accounts for 750,000 hectares in the world. According to Ramón Pamies, more than 20,000 tons of greenhouse plastic are produced in the region alone.
«Our goal is to reduce plastic waste from plasticulture by about 60%. In this way we have an economic advantage because the plastic has to be replaced every five years instead of every three years and an environmental advantage because we reduce the waste of these plastics,” adds the researcher.
Currently, the project is in the pilot-scale development phase to see if the prototypes can be produced on an industrial scale, with the final prototype available within a year. They also plan to conduct field trials, as they are all currently conducted under controlled laboratory conditions, to evaluate this possibility in several test farms in the Region.
Being a sensor that is easy to apply and use, it can be installed in any greenhouse, so it would have a direct impact on the entire agricultural sector of the Region, reducing both production costs and the amount of plastic waste produced .
“Indeed, with the importance of this sector in the region, together with the need for better environmental management of waste and the increase in material costs, we believe that we will make a positive contribution to the sector,” concludes Ramón Pamies.
The project ‘Polymeric optical sensor of accumulated sulfur embedded in thermoplastic matrices with applications in plasticulture’ has the support of the Seneca Foundation within its ‘Proof of Concept’ helpline, with funding of 30,000 euros, and will be completed by the end of this year be completed. year.
“The support of the Seneca Foundation was essential to develop this sensor, as money was needed to perform all the stability tests and test different materials to manufacture the plates,” explains Ramón Pamies.
“These studies are very complex and the production of the pilot scale plates requires a large amount of materials that we would not have been able to afford without this funding. It has given us the opportunity to concretize a concept,” he adds.
Source: La Verdad
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