Biochar for future and futuristic biochar

Biochar,a close-to-natural product derived from renewable biomass resources,has proven to be a promising carbon-negative material for achieving sustainable development goals and improving the future well-being of ecosystems and human life.Over the past thousands of years,advances in biochar research could generally be divided into three stages:the historical application stage,the recognition and investigation stage,and the rapid engineered development and advancement stage.In this perspective,we describe the development history of biochar,discuss the features of futuristic biochar,and propose new research directions for biochar in the future.

Response of microbial communities to biochar-amended soils:a critical review

Application of biochar to soils changes soil physicochemical properties and stimulates the activities of soil microorganisms that influence soil quality and plant performance.Studying the response of soil microbial communities to biochar amendments is important for better understanding interactions of biochar with soil,as well as plants.However,the effect of biochar on soil microorganisms has received less attention than its influences on soil physicochemical properties.In this review,the following key questions are discussed:(i)how does biochar affect soil microbial activities,in particular soil carbon(C)mineralization,nutrient cycling,and enzyme activities?(ii)how do microorganisms respond to biochar amendment in contaminated soils?and(iii)what is the role of biochar as a growth promoter for soil microorganisms?Many studies have demonstrated that biochar-soil application enhances the soil microbial biomass with substantial changes in microbial community composition.Biochar amendment changes microbial habitats,directly or indirectly affects microbial metabolic activities,and modifies the soil microbial community in terms of their diversity and abundance.However,chemical properties of biochar,(especially pH and nutrient content),and physical properties such as pore size,pore volume,and specific surface area play significant roles in determining the efficacy of biochar on microbial performance as biochar provides suitable habitats for microorgan-isms.The mode of action of biochar leading to stimulation of microbial activities is complex and is influenced by the nature of biochar as well as soil conditions.

Biochar and its importance on nutrient dynamics in soil and plant

Biochar,an environmentally friendly soil conditioner,is produced using several thermochemical processes.It has unique characteristics like high surface area,porosity,and surface charges.This paper reviews the fertilizer value of biochar,and its effects on soil properties,and nutrient use efficiency of crops.Biochar serves as an important source of plant nutrients,especially nitrogen in biochar produced from manures and wastes at low temperature(≤400℃).The phosphorus,potassium,and other nutrient contents are higher in manure/waste biochars than those in crop residues and woody biochars.The nutrient contents and pH of biochar are positively correlated with pyrolysis temperature,except for nitrogen content.Biochar improves the nutrient retention capacity of soil,which depends on porosity and surface charge of biochar.Biochar increases nitrogen retention in soil by reducing leaching and gaseous loss,and also increases phosphorus availability by decreasing the leaching process in soil.However,for potassium and other nutrients,biochar shows inconsistent(positive and negative)impacts on soil.After addition of biochar,porosity,aggregate stability,and amount of water held in soil increase and bulk density decreases.Mostly,biochar increases soil pH and,thus,influences nutrient availability for plants.Biochar also alters soil biological properties by increasing microbial populations,enzyme activity,soil respiration,and microbial biomass.Finally,nutrient use efficiency and nutrient uptake improve with the application of biochar to soil.Thus,biochar can be a potential nutrient reservoir for plants and a good amendment to improve soil properties.

A critical review of biochar-based nitrogen fertilizers and their effects on crop production and the environment

Globally,nitrogen(N)fertilizer demand is expected to reach 112 million tonnes to support food production for about 8 billion people.However,more than half of the N fertilizer is lost to the environment with impacts on air,water and soil quality,and biodiversity.Importantly,N loss to the environment contributes to greenhouse gas emissions and climate change.Nevertheless,where N fertilizer application is limited,severe depletion of soil fertility has become a major constraint to sustainable agriculture.To address the issues of low fertilizer N use efficiency(NUE),biochar-based N fertilizers(BBNFs)have been developed to reduce off-site loss and maximize crop N uptake.These products are generally made through physical mixing of biochar and N fertilizer or via coating chemical N fertilizers such as prilled urea with biochar.This review aims to describe the manufacturing processes of BBNFs,and to critically assess the effects of the products on soil properties,crop yield and N loss pathways.

What have we known so far for fluorescence staining and quantification of microplastics:A tutorial review

Understanding the fate and toxicity of microplastics(MPs,<5 mm plastic particles)is limited by quantification methods.This paper summarizes the methods in use and presents new ones.First,sampling and pretreatment processes ofMPs,including sample collection,digestion,density separation,and quality control are reviewed.Then the promising and convenient staining procedures and quantification methods for MPs using fluorescence dyes are reviewed.The factors that influence the staining of MPs,including their physicochemical properties,are summarized to provide an optimal operation procedure.In general,the digestion step is crucial to eliminate natural organic matter(NOM)to avoid interference in quantification.Chloroform was reported to be the most appropriate solvent,and 10–20μg/mL are recommended as optimal dye concentrations.In addition,a heating and cooling procedure is recommended to maintain the fluorescence intensity of MPs for two months.After staining,a fluorescence microscope is usually used to characterize the morphology,mass,or number of MPs,but compositional analysis cannot be determined with it.These fluorescence staining methods have been implemented to study MP abundance,transport,and toxicity and have been combined with other chemical characterization techniques,such as Fourier transform infrared spectroscopy and Raman spectroscopy.More studies are needed to focus on the synthesis of novel dyes to avoid NOM’s interference.They need to be combined with other spectroscopic techniques to characterize plastic composition and to develop image-analysis methods.The stability of stained MPs needs to be improved.

Insights into simultaneous adsorption and oxidation of antimonite[Sb(III)]by crawfish shell-derived biochar:spectroscopic investigation and theoretical calculations

Removal of antimonite[Sb(Ⅲ)]from the aquatic environment and reducing its biotoxicity is urgently needed to safeguard environmental and human health.Herein,crawfish shell-derived biochars(CSB),pyrolyzed at 350,500,and 650℃,were used to remediate Sb(Ⅲ)in aqueous solutions.The adsorption data best fitted to the pseudo-second-order kinetic and Langmuir isotherm models.Biochar produced at 350℃(CSB350)showed the highest adsorption capacity(27.7 mg g^(−1)),and the maximum 78%oxidative conversion of Sb(Ⅲ)to Sb(V).The adsorption results complemented with infrared(FTIR),X-ray photoelectron(XPS),and near-edge X-ray absorption fine structure(NEXAFS)spectroscopy analyses indicated that the adsorption of Sb(Ⅲ)on CSB involved electrostatic interaction,surface complexation with oxygen-containing functional groups(C=O,O=C-O),π-πcoordination with aromatic C=C and C-H groups,and H-bonding with-OH group.Density functional theory calculations verified that surface complexation was the most dominant adsorption mechanism,whilstπ-πcoordination and H-bonding played a secondary role.Furthermore,electron spin resonance(ESR)and mediated electrochemical reduction/oxidation(MER/MEO)analyses confirmed that Sb(Ⅲ)oxidation at the biochar surface was governed by persistent free radicals(PFRs)(•O_(2)^(−)and•OH)and the electron donating/accepting capacity(EDC/EAC)of biochar.The abundance of preferable surface functional groups,high concentration of PFRs,and high EDC conferred CSB350 the property of an optimal adsorbent/oxidant for Sb(Ⅲ)removal from water.The encouraging results of this study call for future trials to apply suitable biochar for removing Sb(Ⅲ)from wastewater at pilot scale and optimize the process.