The Electrochemical Properties of Biochars and How They Affect Soil Redox Properties and Processes

Abstract

Biochars are complex heterogeneous materials that consist of mineral phases, amorphous C, graphitic C, and labile organic molecules, many of which can be either electron donors or acceptors when placed in soil. Biochar is a reductant, but its electrical OPEN ACCESSAgronomy 2015, 5 323 and electrochemical properties are a function of both the temperature of production and the concentration and composition of the various redox active mineral and organic phases present. When biochars are added to soils, they interact with plant roots and root hairs, micro-organisms, soil organic matter, proteins and the nutrient-rich water to form complex organo-mineral-biochar complexes Redox reactions can play an important role in the development of these complexes, and can also result in significant changes in the original C matrix. This paper reviews the redox processes that take place in soil and how they may be affected by the addition of biochar. It reviews the available literature on the redox properties of different biochars. It also reviews how biochar redox properties have been measured and presents new methods and data for determining redox properties of fresh biochars and for biochar/soil systems.

Impact of six lignocellulosic biochars on C and N dynamics of two contrasting soils

“…In the case of Soil B, biochars likely facilitated the formation of anaerobic microsites with low pH and abundant bioavailable C (see section Influence of biochar on the soil environment and substrate availability ), resulting in reduced oxidation of NH 4 + to NO 3 − , inhibited reduction of NO 3 − to N 2 O, and/or enhanced reduction of N 2 O to N 2 (Baggs, ; Harter et al ., ). Indeed, it has been posited that biochars can influence the soil redox potential by (i) acting as semiconductors, (ii) introducing redox‐active species such as iron oxides and quinoid moieties, and (iii) creating unique micro‐ and nanopore environments combining semiconductive boundaries, redox‐active species, and laminar flow (Joseph et al ., , ; Klüpfel et al ., ; Weng et al ., ). Thus, the N 2 O emission results indicate that biochar and soil properties interact to affect soil N 2 O emissions in a complex manner, potentially through multiple context‐specific mechanisms tied to C or N substrate availability and/or the soil redox environment (Sánchez‐García et al ., ).…”

Effects of Biochar Amendment on Chloropicrin Adsorption and Degradation in Soil

“…Additionally, biochars react with microbes, soil organic matter, and minerals within days of addition to soil [1]. There is a formation of organomineral phases that contain nanoparticles especially of redox active Fe and compounds with high contents of quinones/phenols that can catalyse redox reactions [30][31][32][33]. Microbes that can be involved in these redox reactions and the mineral oxide nanoparticles can break down CP through biotic and abiotic oxidation.…”

Effect of Straw Biochar on Soil Properties and Wheat Production under Saline Water Irrigation

“…Biochar is a carbon-rich organic material produced from the pyrolysis of biological matter under a low oxygen condition and possesses several advantages like porous structure, large surface area, and high ion exchange capability [17,18]. The application of biochar to agricultural soils can improve soil physical properties, e.g., bulk density, total porosity, aggregate stability, water holding capacity, permeability, and aeration [19,20].…”