DDD Conference

Mr. Ran Darzi

Hydrothermal Decomposition of Plastic – A New Technology to Fight the Long-Term Effects of Agricultural Plastic Usage

Technion – Israel Institute of Technology, Israel

Plastic usage in agriculture was recently estimated as 3.5% of global plastic production. Plastics in modern agriculture serve numerous purposes, making it essential for food security. Agricultural plastic waste poses difficulties to recycling processes with the current technologies. It often contains mixed-polymers products, UV-degraded, and with high content of contaminations (soil, organics, chemicals). Thus, agricultural plastic waste is mostly landfilled, and often leaks untreated into the environment. Our research suggests a new platform for plastic waste valorization using a hydrothermal process. The technology is based on decomposition of polymers in a water medium at high temperature (300–400°C), under sufficient pressure (higher than the vapor pressure). This research aims to 1) understand the decomposition mechanisms of various polymers and their mixtures; 2) characterize the resulted end-products; and 3) evaluate the advantages of this technology over commonly used recycling practices for agricultural plastic waste. Selected polymers of different types (LDPE, PET, PA6) were hydrothermally treated. Comprehensive chemical analyses were made for all phases (solid, liquid, and gas). PET and PA6 polymers were converted mainly into valuable monomeric compounds, from which a new pristine plastic can be produced. LDPE decomposition was limited, but its presence did not inhibit the decomposition of other feedstock during co-processing. Our results indicate the potential of the hydrothermal technology to achieve closed-loop recycling of plastic waste and promote complex waste co-processing. Consequential study of decomposition mechanisms and process efficiency is required to improve waste treatment alternatives and move towards a circular economy for more sustainable agriculture.

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