A bibliometric analysis on the agricultural use of biochar in Brazil from 2003 to 2021: research status and promising raw materials

Abstract Biochar is considered a promising option for the development of sustainable agroecosystems, due to its diverse agronomic and environmental benefits. In this context, the aim of this study was to carry out a bibliometric analysis on biochar research in Brazil within an agricultural context, including investigating the raw materials most employed for its production in the country. The analysis was conducted based on a search for scientific articles (peer-reviewed papers) at the Web of Science database (WoS Core Collection) from 2003 to 2020 specifically in Brazil. A performance analysis was carried out by applying a descriptive and metric approach concerning research constituents (authors, institutions, countries and keywords) and science mapping to clarify scientific collaborations and cognitive and intellectual structure patterns regarding the biochar domain in Brazilian research, using the VOSviewer software. The obtained studies were also analyzed individually to classify the different raw materials employed in biochar production. A total of 261 scientific articles met the screening criteria, indicating that the beginning of biochar publications in Brazil took place in 2003, increasing until 2015 and peaking in 2021. Institutions and authors with the highest publication contributions were the Brazilian Agricultural Research Corporation (EMBRAPA) (Novotny E.), São Paulo University (USP) (Cerri C.) and Federal Lavras University (UFLA) (Melo L.). The United States, Spain, Australia, Germany and the Netherlands present the most collaborations on biochar research with Brazil. The biochar domain was highly associated with the following keywords: biochar, pyrogenic carbon, pyrolysis, charcoal, immobilization, black carbon, soil fertility and soil and characterization. Raw materials of plant origin were the most employed in biochar research in Brazil, with wood residues being the most studied and residues originated from the sugar-energy industry (straw, bagasse and filter cake) identified as exhibiting high potential for future studies. Poultry litter is the most promising animal waste for biochar production, while the use of biosolids can be innovative, contributing to the consolidation of biochar as an option for serious urban waste sanitary management problems.