Visualizing the emerging trends of biochar research and applications in 2019: a scientometric analysis and review

Abstract

Biochar, derived from thermal pyrolysis of biomass, has been regarded as a low-cost, sustainable and beneficial material and widely applied in agriculture, environment and energy during the last two decades. To elucidate the research status timely and future trends in biochar field, CiteSpace is used to systematically analyze the related literature retrieved from the Web of Science core collection in 2019. Based on the keywords clustering analysis, it was found that "biochar production", "organic pollutants removal", "heavy metals immobilization", "bioremediation" were the main hotspots in research covering biochar. "Bioremediation" is an emerging topic and deserves extensive attention due to its highly effective and environmentally friendly treatment of pollutants. Improving the phytoremediation effect, immobilizing functional microorganisms on biochar, and using microorganisms as raw materials to produce biochar were the common methods of biochar-assisted bioremediation. While studies focused on "soil quality and plant growth" and "biochar and global climate change" decreased, investigations concentrated in the toxicity of biochar to soil biota and ruminants are sustainably growing. Research on direct and catalytic thermal pyrolysis of green waste (mainly microalgae) for biofuels (bio-oil, biodiesel, syngas, etc.) and biochar production is increasing. Converting municipal wastes (e.g., sewage sludge, fallen leaves) into biochar through pyrolysis was a suitable treatment for municipal waste and became a popular topic in recent time. Moreover, the biochar produced from these municipal wastes exhibited excellent performance in the removal of pollutants from wastewater and soil. This review may help to identify future directions in biochar research and applications.

Special issue on sustainable waste treatment and management

“…The manuscript entitled "Characterization and adsorption capacity of modified 3D porous aerogel from grapefruit peels for removal of oils and organic solvents" (Imran et al 2020) synthesized a hydrophobic aerogel with three-dimensional (3D) structure from grapefruit peel by hydrothermal approach and used the porous aerogel as an adsorbent for removal of oils and organic solvents from polluted water. The findings of these studies benefit the agricultural waste recycling utilization and the contaminated water and soil remediation, as reported in many other studies (e.g., Bandara et al 2020;Lehmann 2019;Lu et al 2020;Wu et al 2020).…”

Moderate sewage sludge biochar application on alkaline soil for corn growth: a field study

“…Additionally, the chemical properties and enzymatic activities of the soil are significantly improved after biochar amendment (Pokharel et al 2020;Rafael et al 2019). Biochar can also reduce the bioavailability and toxicity of soil by adsorbing and degrading organic contaminants (Wu et al 2020a).…”

Adsorption of ammonium, nitrite, and nitrate onto rice husk biochar for nitrogen removal

“…(Badiola, Mendiola, & Bostock, 2012). On the other hand, biochar recently emerged as a green adsorbent as well as a disposal filter in biological wastewater treatment mainly for bioretention and bioremediation (Ahmed & Hussain, 2018;Crini & Lichtfouse, 2018;Ferreira, Calisto, Otero, Nadais, & Esteves, 2016;Poor & Mohamed, 2020;Wu et al, 2020). Because biochar is a stable carbon-rich material derived from thermal pyrolysis of biomass, it has been regarded as an economical and sustainable carrier which has extensive application prospects in the field of soil improvement or wastewater treatment.…”

“…Because biochar is a stable carbon-rich material derived from thermal pyrolysis of biomass, it has been regarded as an economical and sustainable carrier which has extensive application prospects in the field of soil improvement or wastewater treatment. Also, there have been many studies on the efficacy of biochar as a support medium during anaerobic/aerobic digestion or a support-based catalyst for biodegradation of recalcitrant contaminants (Enaime, Baçaoui, Yaacoubi, & Lübken, 2020;Lehmann & Joseph, 2015;Wu et al, 2020). Depending on pyrolysis temperatures and postpreparation methods, biochar could be engineered to obtain new valued properties such as higher surface area, micropore volume and specific functional groups that become more suitable for different inorganic/organic substances sorption even for metal immobilization (Enaime et al, 2020;Huang et al, 2016;Mohan, Sarswat, Ok, & Pittman, 2014;Wang et al, 2015).…”