Magnesium activation affects the properties and phosphate sorption capacity of poultry litter biochar

Biochars with a high affinity for phosphorus(P)are promising soil amendments for reducing P in agricultural runoff.Poultry litter(PL)is an abundant biochar feedstock.However,PL-derived biochars are typically high in soluble P and therefore require chemical modification to become effective P sorbents.This study investigated the effect of magnesium(Mg)activation on extractable P(EP)and P sorption capacities of PL-derived biochars.Biochar was produced at 500-900℃ from PL activated with 0-1 M Mg.Three differentially aged PL feedstocks were evaluated(1-,3-5-,and 7-9-year-old).Increased Mg activation level and pyrolysis temperature both resulted in EP reductions from the biochars.Specifically,biochars produced at temperatures≥700℃ from PL activated with≥0.25 M Mg had negligible EP.X-ray diffractograms indicated that increased Mg loading favored the formation of stable Mg_(3)(PO_(4))_(2) phases while increasing temperature favored the formation of both Mg_(3)(PO_(4))_(2) and Ca_(5)(PO_(4))_(3)OH.Maximum P sorption capacities(Pmax)of the biochars were estimated by fitting Langmuir isotherms to batch sorption data and ranged from 0.66-10.35 mg g^(−1).Average Pmax values were not affected by PL age or pyrolysis temperature;however,biochars produced from 1 M Mg-activated PL did have significantly higher average Pmax values(p<0.05),likely due to a greater abundance of MgO.Overall,the results demonstrated that Mg activation is an effective strategy for producing PLderived biochars with the potential ability to reduce P loading into environmentally sensitive ecosystems.

Feedstock choice,pyrolysis temperature and type influence biochar characteristics:a comprehensive meta-data analysis review

Various studies have established that feedstock choice,pyrolysis temperature,and pyrolysis type influence final biochar physicochemical characteristics.However,overarching analyses of pre-biochar creation choices and correlations to biochar characteristics are severely lacking.Thus,the objective of this work was to help researchers,biochar-stakeholders,and practitioners make more well-informed choices in terms of how these three major parameters influence the final biochar product.Utilizing approximately 5400 peer-reviewed journal articles and over 50,800 individual data points,herein we elucidate the selections that influence final biochar physical and chemical properties,total nutrient content,and perhaps more importantly tools one can use to predict biochar’s nutrient availability.Based on the large dataset collected,it appears that pyrolysis type(fast or slow)plays a minor role in biochar physico-(inorganic)chemical characteristics;few differences were evident between production styles.Pyrolysis temperature,however,affects biochar’s longevity,with pyrolysis temperatures>500℃ generally leading to longer-term(i.e.,>1000 years)half-lives.Greater pyrolysis temperatures also led to biochars containing greater overall C and specific surface area(SSA),which could promote soil physico-chemical improvements.However,based on the collected data,it appears that feedstock selection has the largest influence on biochar properties.Specific surface area is greatest in wood-based biochars,which in combination with pyrolysis temperature could likely promote greater changes in soil physical characteristics over other feedstock-based biochars.Crop-and other grass-based biochars appear to have cation exchange capacities greater than other biochars,which in combination with pyrolysis temperature could potentially lead to longer-term changes in soil nutrient retention.The collected data also suggest that one can reasonably predict the availability of various biochar nutrients(e.g.,N,P,K,Ca,Mg,Fe,and Cu)based on feedstock choice and total nutrient content.Results can be used to create designer biochars to help solve environmental issues and supply a variety of plant-available nutrients for crop growth.

Biochar compost blends facilitate switchgrass growth in mine soils by reducing Cd and Zn bioavailability

Biochars have the potential to reclaim mine-impacted soils;however,their variable physico-chemical properties incite specu-lation about their successful remediation performance.This investigation examined the capability of biochars produced from three different feedstocks along with a compost blend to improve switchgrass growth conditions in a mine-impacted soil by examining influences on soil pH,grass metal contents,and soil-extractable metal concentrations.Cadmium(Cd)-and zinc(Zn)-contaminated mine soil was collected from a site near Webb City,Missouri,USA-a location within the Tri-State Min-ing District.In a full factorial design,soil was treated with a 0%,2.5%,and 5%(w/w)compost mixture(wood chips+beef cattle manure),and 0%,2.5%and 5%of each biochar pyrolyzed from beef cattle manure,poultry litter,and lodgepole pine feedstocks.Switchgrass(Panicum virgatum,‘Cave-In-Rock’variety)was grown in a greenhouse for 50 days and the mass of shoots(above-ground biomass)and roots was assessed,while soil pH,deionized H_(2)O-and 0.01 M CaCl_(2)-extractable Cd and Zn concentrations were measured.Poultry litter biochar and compost had the greatest ability to raise soil pH(from 4.40 to 6.61),beef cattle manure biochar and compost moderately raised pH(from 4.4 to 5.92),and lodgepole pine biochar and compost weakly raised pH(from 4.40 to 5.05).Soils treated with beef cattle manure biochar,poultry litter biochar signifi-cantly reduced deionized H_(2)O-and 0.01 M CaCl_(2)-extractable Cd and Zn concentrations,while lodgepole pine biochar-treated soils showed mixed results.Switchgrass shoot and root masses were greatest in soil treated with compost in combination with either beef cattle manure biochar or poultry litter biochar.Soils treated with 5%beef cattle manure biochar+5%compost had greater reductions in total Cd and Zn concentrations measured in switchgrass shoots and roots compared to the other two treatments.The three biochars and compost mixtures applied to heavy metal,mine-impacted soil had considerable performance dissimilarities for improving switchgrass productivity.Switchgrass growth was noticeably improved after treatment with the compost in combination with biochar from beef cattle manure or poultry litter.This may be explained by the increased soil pH that promoted Zn and Cd precipitation and organic functional groups that reduced soil-available heavy metal concentrations.Our results imply that creating designer biochars is an important management component in developing successful mine-site phytostabilization programs.

Microbial response to designer biochar and compost treatments for mining impacted soils

The Oronogo-Duenweg mining belt is a designated United States Environmental Protection Agency Superfund site due to lead-contaminated soil and groundwater by former mining and smelting operations.Sites that have undergone remediation-in which the O,A,and B horizons have been removed alongside the lead contamination-have an exposed C horizon and are incalcitrant to revegetation efforts.Soils also continue to contain quantifiable Cd and Zn concentrations.To improve soil conditions and encourage successful site revegetation,our study employed three biochars,sourced from different feedstocks(poultry litter,beef cattle manure,and lodgepole pine),at two rates of application(2.5%,and 5%),coupled with compost(0%,2.5%and 5%application rates).Two plant species-switchgrass(Panicum virgatum)and buffalograss(Bouteloua dactyloides)-were grown in the amended soils.Amendment of soils with poultry litter biochar applied at 5%resulted in the greatest reduction of soil bioavailable Cd and Zn.Above-ground biomass yields were greatest with beef cattle manure biochar applied at 2.5%with 5%compost,or with 5%biochar at 2.5%and 5%compost rates.Maximal microbial biomass was achieved with 5%poultry litter biochar and 5%compost,and microbial communities in soils amended with poultry litter biochar distinctly clustered away from all other soil treatments.Additionally,poultry litter biochar amended soils had the highest enzyme activity rates forβ-glucosidase,N-acetyl-β-D-glucosaminidase,and esterase.These results suggest that soil reclamation using biochar and compost can improve mine-impacted soil biogeophysical characteristics,and potentially improve future remediation efforts.

Nutrient alterations following biochar application to a Cd-contaminated solution and soil

Biochars,when applied to contaminated solutions or soils,may sequester potentially toxic elements while releasing neces-sary plant nutrients.This purpose of this study focused on quantifying both phenomenon following wheat straw(Triticum aestivum L.)biochar application(0,5,and 15%by wt)to a Cd containing solution and a Cd-contaminated paddy soil using 240-day laboratory batch experiments.Following both experiments,solid phases were analyzed for elemental associations using a combination of wet chemical sequential extractions and synchrotron-based X-ray absorption spectroscopy(XAS).When wheat straw biochar was applied at 15%to Cd containing solutions,Cd and Zn concentrations decreased to below detection in some instances,Ca and Mg concentrations increased by up to 290%,and solution pH increased as compared to the 5%biochar application rate.Similar responses were observed when biochar was added to the Cd-contaminated paddy soil,suggesting that this particular biochar has the ability to sequester potentially toxic elements while releasing necessary plant nutrients to the soil solution.When significant,positive correlations existed between nutrient release over time,while negative correlations were present between biochar application rate,potentially toxic element sorption and pH.The latter suggests that potentially toxic elements were sorbed by a combination of organic functional groups or mineral precipitation based on whether pH was above or below~7.In support of this contention,the wet chemical sequential extraction procedure in conjunction with previously observed Cd or current Zn XAS showed that biochar application promoted the formation of layered double hydroxides,sorption to(oxy)hydroxides,and organically bound to biochar as Zn species.As a multi-functional material,biochar appears to play an important role in sequestering Cd while releasing essential plant nutrients.These findings suggest that biochar may be a‘win-win’for improving environmental quality in potentially toxic element contaminated agroecosystems.

Biochars reduce irrigation water sodium adsorption ratio

Irrigation water quality plays a vital role in sustaining crop productivity and feeding a growing world population.In many countries,continued agricultural water reuse can lead to greater water-soluble salt concentrations,and in particular Na;finding means by which irrigation water Na,and thus sodium adsorption ratios(SAR),can be reduced would reduce the rate at which soil sodification occurs.Four biochars,containing a variety of organic functional groups and electrochemistries,were examined for their potential to sorb and remove Na from simulated irrigation water,and subsequently reduce water SAR.Two batch experiments examined the role that wheat straw biochar,lodgepole pine biochar,Kentucky bluegrass biochar,and hemp biochar played in terms of sorbing sodium over time or application rate.Of the four biochars examined,hemp biochar had the lowest oxidation-reduction potential(ORP;~0-100 mV),sorbed the greatest Na amount(up to 923 mg kg^(−1)),and released Ca and Mg(up to 115 and 63 mg kg^(−1),respectively)into solution,all of which led to a significant reduction in water SAR(from 8.8 to 7.3;17% decrease).Sodium sorption onto hemp biochar better fit a Langmuir versus a Freundlich isotherm,yet followed a pseudo-second-order model better than a pseudo-first-order kinetic model.The data suggest that Na ions formed a monolayer on the hemp biochar surface,influenced by associations withπelectrons,but given time the Na ions may diffuse into biochar pores or more slowly interact with biochar-borneπelectrons.Hemp biochar shows promise in reducing the SAR of Na-impacted waters.Future investigations should focus on additional laboratory,greenhouse,and field trials with hemp biochar and other biochars designed to have similar or superior properties for sorbing excess irrigation water Na and improving crop growth.

Physicochemical disintegration of biochar:a potentially important process for long-term cadmium and lead sorption

Cadmium(Cd)and lead(Pb)contaminated soils that are used for food production can lead to metal bioaccumulation in the food chain and eventually affect human health.In these agroecosystems,means by which Cd and Pb bioavailability can be reduced are desperately required,with biochar as a proxy for bioavailability reductions.Molecular Cd and Pb sorption mecha-nisms within short-(0-2 years)or long-term(8-10 years)time periods following biochar application to a contaminated rice paddy soil were investigated.A combination of Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy,and soft X-ray imaging was utilized to discern potential metal sorption mechanisms.Following both short-and long-term biochar applications,soil Cd and Pb bioavailable fractions shifted partially towards metal(hydr)oxide and carbonate pre-cipitates,and partially towards biochar-organic function group associations;oxygen-containing groups,such as C=O and O-H,appeared to bind Cd and Pb.Soft X-ray imaging results suggested that heavy metals were primarily sorbed on biochar exterior surfaces,yet given time and particle disintegration,metals sorbed onto biochar interior pore walls.Findings sug-gest that biochar may play a pivotal role in reducing long-term bioavailable Cd and Pb in contaminated soils.Observations also support previous findings that suggest biochar use can lead to reduced heavy metal transfer to plants and potentially to reduced heavy metal consumption by humans.