The research group Polymers, Characterization and Applications of the Polytechnic University of Madrid (UPM), in collaboration with the Laboratory of Polymer Engineering of the Department of Chemical Engineering and Environmental Technology of the University of Oviedo, has carried out an investigation that allows to recover plastic waste from agriculture and convert it into new materials with higher added value, low price and improved recyclability.
With them, the environmental impact generated by this type of agricultural waste would be reduced.
The use of plastics in agriculture, both in greenhouse film and in tunnels and mulch, has grown considerably since the 1950s due to the increase in the world population and the greater need to produce food.
Within Europe, Spain is the country with the largest area dedicated to greenhouses in its territory (more than 60,800 hectares), although internationally it is widely surpassed by other countries, such as China, which has more than 1,000,000 hectares.
However, the recovery of used plastics at the end of their useful life is still low.
Only 23% is recycled mechanically, despite the fact that the mechanical recycling of plastic waste makes it possible to obtain new materials from the waste generated and in many cases represents an optimized solution for said waste.
The research carried out is based on two pillars to favor the mechanical recycling of agricultural plastics.
The first is the use of residual cellulose fibers from the papermaking process as reinforcement for agricultural plastic waste.
The mixture of agricultural waste plastics and cellulosic waste allows to obtain eco-composite materials.
The second pillar is the use in the mixture of selected quantities of plastics from urban waste and of chosen additives in order to improve the mechanical properties of the recycled materials obtained.
The use of residual cellulose fibers is of great environmental, economic and social interest, since they are biodegradable materials, low cost, light and of renewable origin.
In the first phase of the project, used agricultural plastics were characterized and ecocomposites with residual cellulose were obtained.
Plastics used in agriculture include diverse polymers and a complex formulation of additives to fulfill their function and improve their durability.
Although due to their application abroad, in very harsh conditions, these plastics experience a great degradation that leads to the loss of properties, it has been observed that these plastic waste still contain traces of valuable light stabilizing additives that can make them interesting for use in Exterior.
The project studied the effects of the percentage of cellulose and the additives added on the properties of the ecocomposites obtained in order to determine the most suitable formulations.
The reinforcing effect of cellulose fibers on residual plastics was demonstrated, resulting in substantial increases in the mechanical strength of ecocomposites.
The investigations carried out made it possible to demonstrate the viability of obtaining these eco-composite materials at the pilot plant scale.
Thus, the manufacture of new recycled eco-composite materials from plastic and cellulosic waste has made it possible to obtain materials with good mechanical properties and suitable for extrusion or injection molding processes. The properties are sufficient for these recycled materials to be used in very diverse applications, including outdoor use.
The demonstration of good properties is essential to favor the recycling of these agricultural and industrial wastes since one of the factors that limits recycling is the market acceptance of products made with recycled materials.
The research carried out can help reduce the proportion of abandoned waste and increase the percentage of mechanical recycling thereof, with the significant savings in raw materials, energy and emissions that this recycling entails.
This research has been supported and funded by the Ministry of the Environment (General Secretariat for the Prevention of Pollution and Climate Change) and the Science, Technology and Innovation Plan of the Government of the Principality of Asturias. Likewise, it has had the support and collaboration of the companies BEFESA Plásticos and CIBA.