Article published in the magazine ACS Sustainable Chemistry & Engineering brings good news for coffee lovers: discarded plastic capsules can now be used as raw material for the manufacture of filaments intended, for example, for 3D printing, minimizing environmental impacts.
This alternative was successfully tested by groups from the Federal Universities of São Carlos (UFSCar), State Universities of Campinas (Unicamp) and Manchester Metropolitan (United Kingdom).
“We produce new filaments, conductive and non-conductive, using the polymer polylactic acid [PLA] from coffee capsules. These filaments can be used for the most diverse applications, including conductive parts for machines and sensors”, Bruno Campos Janegitz, coordinator of the Laboratory of Sensors, Nanomedicine and Nanostructured Materials (LSNano) at UFSCar, in Araras, and co-author of the article.
Brazil is the largest producer, largest exporter and, after the United States, the second largest consumer of coffee in the world. Although low quality coffee largely predominates in the Brazilian market – with Robusta beans (Coffea canephora) and a high incidence of defects and impurities, which manufacturers disguise through excessive roasting and consumers hide by adding large amounts of sugar or sweeteners – , the segment of so-called gourmet and specialty coffees has grown consistently.
Produced with selected beans of the Arabica species (Coffea arabica) and a shorter roasting time, in order to preserve the natural sugar and the olfactory and gustatory qualities of the coffee, the “gourmet” version scores from 75 to 80 on the zero to one hundred coffee scale. Brazilian Coffee Industry Association (Abic). To achieve this classification, the “special” must also have a socio-environmental certificate and score at least 80 on the Brazilian Specialty Coffee Association (BSCA) scale.
In addition to the product, the final quality of the drink also depends on the preparation method. Therefore, the domestic use of equipment such as the French press, the Italian coffee maker and, at a higher price level, the coffee maker filled with encapsulated powder has become widespread. The problem, in the latter case, is what to do with the capsule after use.
Although there are reusable capsules and some manufacturers also promote the recycling of aluminum versions, pure and simple disposal predominates, especially in the case of plastic capsules. Considering all the factors involved, an account carried out at the Institute of Technological Research (IPT) showed that “drinking a cup of coffee from a capsule can be up to 14 times more harmful to the environment than 'passing' it through a paper strainer”.
new destination
With the aim of finding new destinations for this waste, the researchers produced electrochemical cells with non-conductive PLA filaments and electrochemical sensors with conductive filaments, which were prepared by adding carbon black to PLA. Carbon black is a form of paracrystalline carbon resulting from the incomplete combustion of hydrocarbons. “Electrochemical sensors were used to determine the percentage of caffeine in green tea and Arabica coffee”, informs Janegitz.
The researcher says that the production of filaments is relatively simple. “Obtaining a non-conductive material simply consists of washing and drying the PLA capsules, followed by extrusion in a hot system. To obtain conductive material, carbon black must be added before heating and extrusion. The extruded material is then cooled and rolled, giving rise to the filaments of interest”, he details.
The entire process is a good example of the so-called “circular economy”, in which waste generated in an economic activity, instead of being treated as problems, impacting the environment, are converted into resources to implement another activity. “The polymeric base obtained from used capsules can generate devices with high added value”, comments Janegitz.
He and Dr. Cristiane Kalinke, from Unicamp, participated in the study during a research internship abroad, under the supervision of Professor Craig Banks, from Manchester Metropolitan University (United Kingdom). Janegitz received support from FAPESP through a Thematic Project and Research Grant Abroad. Kalinke was supported with a Research Internship Abroad Grant. In addition to them, the work also included the participation of professor Juliano Alves Bonacin, from Unicamp.
Article originally published on the Agência Fapesp website.
