Predicting biochar properties and functions based on feedstock and pyrolysis temperature: A review and data syntheses

Biochar has been widely studied as a soil amendment to improve soil properties. When different feedstocks are used to produce biochar under different pyrolysis conditions, the resulting biochar would typically differ in physicochemical properties, which consequently impact the agricultural and environmental performance of biochar in its real-world applications. In this work, based on previously reported data from independent studies, different biochar properties were synthesized as a continuum of pyrolysis temperature and feedstock type. Despite the fact that other factors besides pyrolysis temperature and feedstock type might also impact biochar properties, given the same category of feedstock, many critical properties such as biochar yield, pH, cation exchange capacity, specific surface area, ash content, volatile matter content, and elemental composition have been found to well correlate with pyrolysis temperature, showing p-values smaller than 0.05. At the same time, through meta-analyses, the effects of pyrolysis temperature and feedstock type on the agricultural and environmental impacts of biochar, including nitrogen retention, nitrous oxide emission and crop production, have been evaluated. The study has demonstrated that quantitative approaches such as data syntheses and meta-analyses are potential for revealing predictive relationships that can link biochar production with its properties and performance in real-world applications. (C) 2019 Elsevier Ltd. All rights reserved.