They find utility for the waste of absorbent hygiene products

The generation of urban solid waste represents around 2,000 million tons a year worldwide, of which 22 million tons are produced in Spain. Of this amount, 164,100 tons are waste from absorbent hygiene products. This waste is considered non-recyclable due to the complexity of its manufacturing materials, since its structure is made up of an outer layer of polyester fibers, an inner layer of cellulose of vegetable origin and a percentage of powdered sodium polyacrylate.

On the other hand, plaster is a material widely used in construction in countries like Spain, because it is abundant and has important qualities. However, it is very fragile. For this reason, manufacturers of plaster products have chosen to use a variety of additives (such as synthetic and vegetable fibers) that have been shown to improve mechanical resistance and, above all, their rigidity.

Researchers at the Escuela Técnica Superior de Edificación (ETSEM) of the Universidad Politécnica de Madrid (UPM) in Spain have studied the feasibility of incorporating waste from absorbent hygiene products (including diapers, compresses or wet wipes) into carbon-based construction materials. plaster, as a replacement for the reinforcing fibers currently used (fiberglass and polymers), in order to reduce the consumption of raw material and improve the mechanical behavior of plaster with circular economy criteria.

For this, and after a detailed bibliographical and documentary search, an experimental plan was designed to verify that including these residues in the plaster could improve the properties of mechanical resistance and the surface hardness required of this material in current regulations.

Absorbent hygiene products. (Photo: UPM)

The investigation was developed in two phases. In a first phase, the recycled fibers, the water / plaster ratio as well as the percentage of added waste were analyzed. In a second phase, physical tests and mechanical tests were carried out on mixtures with different percentages of waste. The physical and mechanical tests were carried out in the materials laboratory of the ETSEM of the UPM.

The waste used came from diaper waste, from which the following formats were obtained: cellulose pulp in wool format, polyester fiber and recycled sodium polyacrylate powder.

The test results show that the mixture with cellulose improves the mechanical behavior of the compounds and increases the surface hardness. In this sense, it can be concluded that it is feasible to replace part of the plaster with waste from absorbent hygienic products, guaranteeing the mechanical resistance values ​​and setting times required by the current UNE-EN 13279-2 standard.

“Based on the results we have obtained, we can state that the waste from absorbent hygiene products can replace some construction raw materials,” says Mercedes del Río, a UPM researcher who has participated in the study. “For example, plaster with the addition of recycled cellulose residues could be used to manufacture construction elements for interior partitions and false ceilings,” concludes the researcher.

The study is titled “Mechanical behavior of a gypsum material with additions of recycled waste from absorbent hygienic products”. And it has been published in the academic journal Construction and Building Materials. (Source: UPM)