Bibliometric analysis of the evolution of biochar research trends and scientific production

Biochar has caught great attention over the last decade, yielding a large number of publications in a broad range of disciplines. This scientometric study produces a combined qualitative–quantitative assessment of 10,000 publications recorded in the period 2005–2019 in the Web of Science (WoS) database, based on innovative methods and indicators, and focusing in particular on biochar production and valorization pathways. The cumulated number of publications was analyzed with power and logistic models, and the economic indicator CAGR (Compound Annual Growth Rate) for the estimation of future academic output. Mapping of the evolution of academic output revealed the worldwide diffusion of academic production toward many countries and continents. According to the analysis of collaboration networks of most productive countries, the development of academic output may be linked to high levels of international collaboration, as well as the diversity of these networks. Furthermore, the rise of academic output in the African continent may preclude an evolution toward a multipolar academic world. The average number of citations per paper at both author level (number of citations/number of papers) and journal level (total citations/total papers) was found to be a useful indicator of scientific productivity. In particular, academic journals with impact factors as low as 2.5–3 still ranked high on this criterion, revealing their high impact on academic research in the biochar sector. Finally, the analysis of targeted keywords co-occurrences emphasized the diversification of research on biochar applications, from its initial use as soil improver toward engineered biochar for versatile applications. Graphic abstract