This review analyzes over 50,000 data points from nearly 5400 publications to determine how feedstock choice, pyrolysis temperature, and pyrolysis type affect biochar properties, particularly nutrient content. The study suggests that feedstock selection has the biggest impact, with manures/biosolids generally having the highest nutrient concentrations, and that it is possible to predict plant-available nutrients based on total nutrient content for certain feedstocks and elements (like K in wood-derived biochars).

The authors received partial funding from various organizations related to agriculture and bioenergy, including USDA/NIFA and FACCE-JPI. However, the authors explicitly state that the views expressed in the publication are theirs and do not necessarily reflect the view of the USDA.

This is a useful review summarizing a large body of literature on biochar. While the dataset is somewhat outdated and the methodology has some limitations, the overall analysis provides some valuable insights into the relationship between feedstock choice, pyrolysis conditions, and nutrient availability in biochar. The identified weaknesses limit the rating to a 3.