The Effect of Biodegradable Waste Pyrolysis Temperatures on Selected Biochar Properties.

Katarzyna Wystalska,Anna Kwarciak-Kozłowska

doi:10.3390/ma14071644

Katarzyna Wystalska, Anna Kwarciak-Kozłowska

Open Access

https://doi.org/10.3390/ma14071644

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Abstract

Biochars produced during biodegradable waste pyrolysis are products with a wide range of environmental applications. The effect of impact biochars depends on their properties which determine the course of specific processes. The main aim of the study was to investigate the effect of pyrolysis temperature on selected properties of biochar produced from various plant wastes (beech wood chips, walnut shells, wheat-rye straw), the valorization of which is of key importance for the implementation of the circular economy. Biochars were produced at temperatures of: 400 °C, 500 °C, 600 °C and 700 °C in a nitrogen atmosphere. An increase in the pyrolysis temperature caused a drop in the biochar production yield. As the temperature increased, higher carbon content and lower hydrogen content could be seen in the products obtained. An increase in the pH and total organic carbon (TOC) values also found. The influence of temperature on ash content, observed in the case of BWS (biochar from walnut shell) and BWRS (biochar from wheat and rye straw), did not occur in the case of BWC (biochar from beech wood chips). Another parameter that demonstrated a growing tendency with increasing temperature was the BET specific surface area (except for biochars from wheat and rye straw). An increase in pyrolysis temperature caused a decrease in the diversity and density of the surface functional groups of biochars. The influence of the type of precursor used in the production of biochar on the presence of surface functional groups was demonstrated. The presence of intense stretching vibrations of C–O bonds, having a potential impact on the sorption capacity of biochars, was determined in the FTIR spectra of BWC600 and BWC700 biochars, this feature, combined with the large BET surface area, may affect the sorption potential of these biochars. The presence of this type of high-intensity vibrations was also observed in the spectra of biochar BWRS600 and BWRS700. This can compensate for the low BET surface value and play an important role when using these biochars in sorption processes for organic and inorganic compounds.

Highlights

One of the challenges of the circular economy, i.e., an economy which aims, among others, at minimizing the quantities of waste generated, is the capacity of recovering useful products from waste materials
The highest total carbon content was found in beech wood chips and walnut shell, while a slightly lesser content of that component was determined for wheat and rye straw
This dependence results from the decomposition of organic compounds as the process temperature grows [10]

Summary

Introduction

One of the challenges of the circular economy, i.e., an economy which aims, among others, at minimizing the quantities of waste generated, is the capacity of recovering useful products from waste materials Such a solution requires systemic transformations and changes in management, and the development of new environment-friendly waste treatment technologies. This manner of waste handling makes it possible to reduce the use of natural resources and to generate energy and new materials. Appropriate waste management would eliminate their adverse environmental impacts (among others, greenhouse gas emissions, water and soil pollutants), and, in line with the current expectations, enable new value added products to be derived [1,2,3,4,5]. These products could be incorporated into the environmental cycle while, at the same time, closing the nutrient cycles [6]

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