Abstract
Biochar is a porous material obtained by biomass thermal degradation in oxygen-starved conditions. It is nowadays applied in many fields. For instance, it is used to synthesize new materials for environmental remediation, catalysis, animal feeding, adsorbent for smells, etc. In the last decades, biochar has been applied also to soils due to its beneficial effects on soil structure, pH, soil organic carbon content, and stability, and, therefore, soil fertility. In addition, this carbonaceous material shows high chemical stability. Once applied to soil it maintains its nature for centuries. Consequently, it can be considered a sink to store atmospheric carbon dioxide in soils, thereby mitigating the effects of global climatic changes. The literature contains plenty of papers dealing with biochar’s environmental effects. However, a discrepancy exists between studies dealing with biochar applications and those dealing with the physical-chemistry behind biochar behavior. On the one hand, the impression is that most of the papers where biochar is tested in soils are based on trial-and-error procedures. Sometimes these give positive results, sometimes not. Consequently, it appears that the scientific world is divided into two factions: either supporters or detractors. On the other hand, studies dealing with biochar’s physical-chemistry do not appear helpful in settling the factions’ problem. This review paper aims at collecting all the information on physical-chemistry of biochar and to use it to explain biochar’s role in different fields of application.
Highlights
Global climate change (GCC) is the most important challenge mankind is facing in the modern era
The whole scientific community agrees that the main cause of GCC are greenhouse gases which have atmospheric concentrations that depends on natural Earth emissions and, and mainly, on anthropic activities such as agriculture, deforestation, and burning of fossil fuels [1]
Exampleofofbiochar biocharstructure structureintended intended a stacked crystalline graphene sheets randomly ordered amorphous aromatic structures (thishas figure has been reproduced from Reference aromatic structures (this figure been reproduced from Reference aforementioned structure, structure, hetero-atoms, hetero-atoms, such such as as O, O, N, N, P, P, and S, are predomipredomiIn the aforementioned contributing to to thethe complex surface nantly incorporated incorporatedwithin withinthe thearomatic aromaticrings, rings,thereby thereby contributing complex surchemistry and reactivity of biochar face chemistry and reactivity of biochar induces to think that environmental environmental release release of of polypolyThe chemical nature of biochar induces cyclic aromatic hydrocarbons (PAHs, persistent pollutants formed during pyrolysis) cyclic aromatic hydrocarbons (PAHs, persistent pollutants formed during pyrolysis) may may occur [3,52,53]
Summary
Global climate change (GCC) is the most important challenge mankind is facing in the modern era. This definition implies that many plant biomass species can for be biochar used for production regardless of the time needed for their replacement. “Biochar is a porous, carbonaceous material that is produced by pyrolysis of plant biomasses and is applied in such a way that the contained carbon remains stored as a longterm C sink or replaces fossil carbon in industrial manufacturing. It is not made to be burnt for energy generation” According to this more general definition, the only biomasses that can be used for biochar production are those obtained by fast growing plants, plant residues from certified forestry management, agricultural residues, and organic wastes from urban areas [28].
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