Influence of pyrolysis temperature and feedstock on the properties of biochars produced from agricultural and industrial wastes

Pyrolysis of waste materials aiming to produce biochar has been considered as an effective strategy to add value and to recycle such materials. The properties of the produced biochars depends on pyrolysis temperature and feedstock type, for example. Some waste materials have been still poorly studied. The objective of this study was to evaluate the changes in physicochemical characteristics, mineral composition, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) of biochars derived from agricultural and industrial wastes produced by different pyrolysis temperatures and feedstocks. Two agricultural solid wastes (poultry litter - PL and swine manure - SM) and three industrial wastes (construction wood - CW, tire - TR and PVC plastic - PVC) were pyrolyzed at five temperatures (300, 400, 500, 600 and 700 °C) in an oxygen-limited environment at a heating rate of 10 °C min−1 for one hour. Increased pyrolysis temperature reduced the yield of solids and volatile compounds and increased pH in water and Ksoluble in all studied biochars. Nevertheless, the temperature caused no significant changes in electrical conductivity, water-soluble nutrients and total elements, and CEC, in the industrial wastes (CW, TR and PVC). The XRD patterns revealed similarities in mineral formation among the studied biochars, including quartz, sylvite, calcite and dolomite. Data of FTIR spectra evidenced the presence of aromatic and aliphatic functional groups. The results obtained enable the design of biochars for a desired purpose, which might be solutions for agronomic and environmental issues, taking into account the effects of pyrolysis temperature and the type of waste to be processed.