A new proposal to reduce microplastics from cigarette butts: Production of eco-friendly fired clay bricks

It is estimated that approximately 1.2 million tons of cigarette butts (CBs) are introduced into the environment annually. The aim of this work is to analyze the incorporation of shredded CBs into bricks making by extrusion, for recycling and waste recovery purposes. Samples were prepared in compositions of 0 %, 1 %, 2.5 % and 5 % w/w CBs and fired at 700 degrees C, 900 degrees C and 1000 degrees C. Density, water absorption, apparent porosity, linear firing shrinkage, flexural strength, compressive strength, thermal conductivity, diffusivity and sound transmission loss (TL) were determined. A total of 180 samples were taken, and a Weibull statistical analysis was performed for compressive strength. The results showed a decrease in density and an increase in water absorption and apparent porosity of the clay bricks produced by mixing 1-5 % CBs compared to the control bricks. Firing shrinkage decreased with 1 % CBs and up to 2.5 %, its was lower than standard samples. Samples with CBs showed fewer cracks than standard samples. Compressive strength increased with 1 % CBs incorporation for firing temperatures of 900 degrees C and 1000 degrees C compared to standard samples. It gradually decreased with larger amounts of waste. For flexural strength, up to 2.5 % CBs, the strength increased in most cases. In addition, there was an improvement in the thermal conductivity of bricks prepared with 5 % CBs and fired at 700 degrees C and 900 degrees C (0.46-0.58 W/mK) compared to the reference samples (0.51-0.76 W/mK). All waste samples showed higher TL than the reference pieces. Above 2.5 % CBs, TL decreased, but remained larger than the reference. Thus, the results showed that the use of CBs in fired clay bricks in amounts of up to 5 % w/w is capable of forming porosity in the samples, making the part lighter, in addition to possibly reducing thermal conductivity and sound transmission, being an economical and sustainable alternative for the final disposal of CBs.