Biochar as a sorbent for contaminant management in soil and water: a review.

Organic and inorganic contaminants removal from water with biochar, a renewable, low cost and sustainable adsorbent--a critical review.

Application of biochar for the removal of pollutants from aqueous solutions.

Biochar is a carbon-rich coproduct resulting from pyrolyzing biomass. When applied to the soil it resists decomposition, effectively sequestering the applied carbon and mitigating anthropogenic CO2 emissions. Other promoted benefits of biochar application to soil include increased plant productivity and reduced nutrient leaching. However, the effects of biochar are variable and it remains unclear if recent enthusiasm can be justified. We evaluate ecosystem responses to biochar application with a meta-analysis of 371 independent studies culled from 114 published manuscripts. We find that despite variability introduced by soil and climate, the addition of biochar to soils resulted, on average, in increased aboveground productivity, crop yield, soil microbial biomass, rhizobia nodulation, plant K tissue concentration, soil phosphorus (P), soil potassium (K), total soil nitrogen (N), and total soil carbon (C) compared with control conditions. Soil pH also tended to increase, becoming less acidic, following the addition of biochar. Variables that showed no significant mean response to biochar included belowground productivity, the ratio of aboveground : belowground biomass, mycorrhizal colonization of roots, plant tissue N, and soil P concentration, and soil inorganic N. Additional analyses found no detectable relationship between the amount of biochar added and aboveground productivity. Our results provide the first quantitative review of the effects of biochar on multiple ecosystem functions and the central tendencies suggest that biochar holds promise in being a win-win-win solution to energy, carbon storage, and ecosystem function. However, biochar's impacts on a fourth component, the downstream nontarget environments, remain unknown and present a critical research gap.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/gcbb.12037

Biochar and its effects on plant productivity and nutrient cycling: a meta‐analysis

Mechanisms of metal sorption by biochars: Biochar characteristics and modifications

The forms of alkalis in the biochar produced from crop residues at different temperatures

Adsorption of Cu(II) by biochars generated from three crop straws

Adsorption of methyl violet from aqueous solutions by the biochars derived from crop residues.

Purpose
The key factors influencing pH buffering capacity of acid soils from tropical and subtropical regions, and effects of soil evolution and incorporation of biochars on pH buffering capacity were investigated to develop suitable methods to increase pH buffering capacity of acid soils.

pH buffering capacity of acid soils from tropical and subtropical regions of China as influenced by incorporation of crop straw biochars

The amelioration effects of crop straws and their biochars on an acidic ultisol were compared in incubation experiments to determine suitable organic amendments for acid soils. Four crop straws, including non-legumes (canola straw and rice straw) and legumes (soybean straw and pea straw) were used to prepare biochars using a low temperature (350°C) oxygen-limited pyrolysis method. Two application rates of 1% and 2% were used for both crop straws and their biochars in incubation experiments lasting 90 days. Soil pH (1:2.5 soil to water), soil exchangeable acidity, soil exchangeable base cations, and soil cation exchange capacity (CEC) were determined to evaluate the amelioration effects of these crop straws and their biochars on an acidic ultisol. The incorporation of crop straws increased or decreased the soil pH depending on the relative contribution of alkalinity of the straws, mineralization of organic N and nitrification of NH4
 +. The incorporation of biochars produced from crop straws increased the soil pH, and their ameliorating effects increased with the application rates of biochars. The biochars from legume straws induced more increase in soil pH than non-legume biochars. The addition of both crop straws and their biochars decreased soil exchangeable acidity and exchangeable Al3+, and increased soil exchangeable base cations and base saturation degree. The biochars (especially legumes) induced a greater decrease in soil exchangeable acidity and a greater increase in soil exchangeable base cations compared to their feedstock due to their much higher contents of base cations. The CEC of biochars were 10–20 times that of soil CEC and thus biochar incorporation increased the soil CEC significantly, as well as the retention of Ca2+, Mg2+, K+, and NH4
 + by acid soils. The biochars produced from legume crop straws were better choices as amendments for acid soils than their feedstock. Organic anions and carbonates were the main forms of alkali in the biochar; both contributed to neutralizing soil acidity and increasing soil pH. The incorporation of biochar cannot only neutralize soil acidity, but can also improve soil fertility.

Jin-hua Yuan

Papers

The forms of alkalis in the biochar produced from crop residues at different temperatures

Adsorption of Cu(II) by biochars generated from three crop straws

Adsorption of methyl violet from aqueous solutions by the biochars derived from crop residues.

pH buffering capacity of acid soils from tropical and subtropical regions of China as influenced by incorporation of crop straw biochars

Comparison of the ameliorating effects on an acidic ultisol between four crop straws and their biochars