Biochar produced from anaerobically digested fiber reduces phosphorus in dairy lagoons

Potentially migrating and residual components of biochar: Effects on phosphorus adsorption performance and storage capacity of black soil

Biochar has great potential to increase the soil nutrient storage capacity. However, with aging, biochar gradually disintegrates and releases fractions with migration potential, resulting in unknown effects on soil nutrient regulation. Based on this problem, we used ultrasound to separate original biochar (TB) into potentially migrating biochar (DB) and residual biochar (RB). The elemental composition and pore characteristics of TB, DB and RB were analyzed. Different fractions of biochar were applied to black soil, and the kinetic model and isothermal adsorption models were used to explore the adsorption characteristics of different treatments. Then, the effects of initial pH and coexisting ions on adsorption were compared. The adsorption mechanism and potential leaching process of phosphorus in soil were investigated. The results showed that RB had higher O and H contents and was less stable than TB, while RB was more aromatic. The phosphorus adsorption capacity of different treatments was SRB (1.3318 mg g^-1) > STB (1.2873 mg g^-1) > SDB (1.3025 mg g^-1) > SCK (1.1905 mg g^-1). SRB had optimal phosphorus adsorption performance and storage capacity, with a maximum adsorption capacity of 1.6741 mg g^-1 for the Langmuir isotherm, and it also showed excellent applicability in a pH gradient and with coexisting ions. The main adsorption mode of phosphorus by different treatments was monolayer chemisorption, related to electrostatic repulsion and oxygen-containing functional groups. DB was less effective in inhibiting soil phosphorus migration, with the cumulative leaching of SDB reaching 8.99 mg and the percentage of phosphorus in the 0-6 cm soil layer reaching only 15.42%. Overall, the results can help elucidate potential trends in the adsorption performance and migration process of soil phosphorus by biochar, and improve the comprehensive utilization efficiency of biochar.

Biochar affects the fate of phosphorus in soil and water: A critical review

Biochar is a promising novel material for managing phosphorus (P), a nutrient often limiting for primary production but can also be a pollutant, in the environment. Reducing P input to the environment and finding cost-effective approaches to remediate P contamination are major challenges in P management. There is currently no review that systematically summarizes biochar effects on soil P availability and its P removal potential from water systems. In this paper, we comprehensively reviewed biochar effects on soil P availability and P removal from water systems and discussed the mechanisms involved. Biochar affects soil P cycling by altering P chemical forms, changing soil P sorption and desorption capacities, and influencing microbial population size, enzyme activities, mycorrhizal associations and microbial production of metal-chelating organic acids. The porous structure, high specific surface area, and metal oxide and surface functional groups make biochars effective materials for removing P from eutrophic water via ligand exchange, cation bridge, and P precipitation. Because soil and biochar properties are widely variable, the effect of biochar on the fate of P in soil and water systems is inconsistent among different studies. Knowledge gaps in the economic practicability of large-scale biochar application, the longevity of biochar benefits, and the potential ecological risks of biochar application should be addressed in future research.

Impact of Oil Palm Empty Fruit Bunch Biochar Enriched with Chicken Manure Extract on Phosphorus Retention in Sandy Soil

A 45-day incubation and leaching experiments was conducted to determine the effect of different rates (0, 1, 2, 3, and 5 t ha−1) of enriched empty fruit bunches biochar (EEFB) and inorganic fertilizer (91 kg ha−1 triple superphosphate—TSP) on the availability and leaching losses of phosphorus from sandy soil (tin tailing soil). The treatments rates for the study were designated as T1—without fertilizer (control), T2—inorganic fertilizer treatment using TSP and T3, T4, T5, and T6, which refers to EEFB rate of 1, 2, 3, and 5 t ha−1, respectively. The enriched biochar was prepared by shaking biochar with chicken manure extract for 24 h. The addition of EEFB to the soils was found to increase pH of the soil compared to control and inorganic fertilizer treatment. After 45 days of incubation, the percentage increase in available P recorded in EEFB treatments were 1.6, 2.9, 2.8, and 4.1%, whereas for control treatment and inorganic fertilizer treatment, the available phosphorus was found to reduce by 10% and 83%, respectively. Loss of phosphorus via leaching in the soil was higher in EEFB treatments compared to control. However, the highest phosphorus leaching among all treatments in this study was recorded in inorganic fertilizer treatments. From the study, it was observed that biochar can be used to recapture phosphorus from chicken manure extract for transport to the soil, thereby reducing problems associated with chicken manure application.

Different effects of N2-flow and air-limited pyrolysis on bamboo-derived biochars' nitrogen and phosphorus release and sorption characteristics

Advantages for biochars used in soil improvement have been proposed to their nutrients release and sorption characteristics which strongly depend on their production conditions. N₂-flow and air-limited pyrolysis are two different widely-applied oxygen-limited pyrolysis methods for producing biochars, however, their different effects on nutrients release and sorption characteristics of biochars remains unknown. In this study, bamboo derived biochars pyrolyzed in N₂-flow (BC-N₂) and air-limited environments (BC-Air) at the temperature of 150~750 °C were used to compare the release and sorption of nitrogen and phosphorous nutrients. The results showed that release of nitrogen and phosphorous in BC-Air were always greater than those in BC-N₂, the maximum nitrogen and phosphorous release of BC-Air (0.65 mg/g at 750 °C) is about 7.7 times of that of BC-N₂ (0.084 mg/g at 450 °C). Both BC-N₂ and BC-Air had no/little sorption of phosphate. Meanwhile, the sorption capacity of ammonium nitrogen on BC-Air (1.83 ~ 4.67 mg/g) was always greater than that on BC-N₂ (0.23 ~ 1.34 mg/g) at the pyrolysis temperature of 300 ~ 750 °C. Phosphorous-containing minerals in ash was an enhancing factor for the release of phosphorous and sorption of ammonium nitrogen on BC-Air. Furthermore, with increasing pyrolysis temperature, the release amount of phosphorous from BC-Air and the sorption capacity of ammonium nitrogen on BC-Air increased. The results show that high pyrolysis temperature combined with air-limited environment produced biochars are optimal for nutrients enhancement and retention.

Nitrogen doped char from anaerobically digested fiber for phosphate removal in aqueous solutions

This study explores the use of an engineered char produced from the pyrolysis of anaerobically digested fiber (ADF) to adsorb phosphate from aqueous solutions. Two series of engineered chars were produced. The first series was a CO₂ activated (CA) char produced via slow pyrolysis between 350 and 750 °C. The second series was a nitrogen doped (ND) char activated in the presence of ammonia at comparable temperatures. Proximate analysis, elemental composition, gas physisorption, Inductively coupled plasma mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray powder diffraction (XRD) techniques were used to characterize properties of resulting products. The surface area of the carbon product increased after nitrogen doping through ammonization (166.6-463.1 m²/g) compared to CO₂ activated chars (156.5-413.1 m²/g). Phosphate adsorption isotherms for both CO₂ activated and nitrogen doped chars can be described by the Langmuir- Freundlich and Redlich Peterson adsorption models. Nitrogen doped carbon phosphate sorption capacity in aqueous solutions was twice compared to CO₂ activated carbons. As carbonization/activation temperature increased the sorption capacity increased from 3.4 to 33.3 mg g^-1 for CA char and 6.3-63.1 mg g^-1 for nitrogen doped char.

Managing Beef Backgrounding Residual Soil Contaminants by Alum and Biochar Amendments

Heavy manure-derived contamination of soils can make animal congregating areas nonpoint sources for environmental pollution. In situ soil stabilization is a cost-effective management strategy with a focus on lowering contaminant availability and limiting release to the environment. Soil stabilizing amendments can help mitigate the negative environmental impacts of contaminated soils. In this 2-yr study, we examined the effects of adding no amendment (control) or treating with alum [Al (SO)⋅18HO] or biochar as soil amendments on Mehlich-3 extractable soil P, Cu, and Zn contents, antimicrobial monensin concentrations, total bacteria (16S ribosomal RNA [rRNA] gene), antibiotic resistance genes (1 and B), and Class 1 integrons (1) in an abandoned beef backgrounding setting. The alum reduced soil P (1374 to 1060 mg kg), Cu (7.7 to 3.2 mg kg), and Zn (52.4 to 19.6 mg kg) contents. Both alum and biochar reduced monesin concentrations (1.8 to 0.7 and 2.1 to 1.1 ng g, respectively). All the treatments harbored consistent 16 rRNA concentrations (10 copies g) throughout. The B gene concentration (10 copies g) was lower than either the 1 or the 1 genes (10 copies g), regardless of treatments. However, concentrations of all genes in the soils of animal congregation areas were higher than those in background soils with the least animal impact. In contrast with the effect on other contaminants, the effect of soil amendments on bacteria with antibiotic resistance genes was not biologically significant. Future research should be directed toward evaluating effective alternative methods to mitigate these bacterial populations.

Engineered/designer biochar for the removal of phosphate in water and wastewater

During the past decade, biochar has attracted immense scientific interest for agricultural and environmental applications. A broad range of biochars with advantageous properties (e.g., high surface area, flexible architecture, and high porosity) has been developed for pollution abatement. Nevertheless, biochar suffers from certain drawbacks (e.g., limited sorption capacity for anions and poor mechanical properties) that limit their practical applicability. This review focuses on recent advancements in biochar technology, especially with respect to its technical aspects, the variables associated with removing phosphates from water, and the challenges for such abatement. The attention paid to the specific remediation of phosphate from water using biochar is limited (n=1114 - Scopus) compared to the application of biochar to other common water pollutants (n=3998 - Scopus). The subject warrants immediate rigorous research because of the undesirable effects of excess phosphate in water bodies. This review will thus facilitate the construction of a roadmap for further developments and the expansion of this challenging area of research.

Agronomic benefits of biochar as a soil amendment after its use as waste water filtration medium

In many water-scarce countries, waste water is used for irrigation which poses a health risk to farmers and consumers. At the same time, it delivers nutrients to the farming systems. In this study, we tested the hypotheses that biochar can be used as a filter medium for waste water treatment to reduce pathogen loads. At the same time, the biochar is becoming enriched with nutrients and therefore can act as a fertilizer for soil amendment. We used biochar as a filter medium for the filtration of raw waste water and compared the agronomic effects of this "filterchar" (FC) and the untreated biochar (BC) in a greenhouse pot trial on spring wheat biomass production on an acidic sandy soil from Niger. The biochar filter showed the same removal of pathogens as a common sand filter (1.4 log units on average). We did not observe a nutrient accumulation in FC compared to untreated BC. Instead, P, Mg and K were reduced during filtration while N content remained unchanged. Nevertheless, higher biomass (Triticum L. Spp.) production in BC (+72%) and FC (+37%) treatments (20 t ha^-1), compared with the unamended control, were found. There were no significant differences in aboveground biomass production between BC and FC. Soil available P content was increased by BC (+106%) and FC (+52%) application. Besides, mineral nitrogen content was reduced in BC treated soil and to a lesser extent when FC was used. This may be explained by reduced sorption affinity for mineral nitrogen compounds on FC surfaces. Although the nutrients provided by FC decreased, due to leaching in the filter, it still yielded higher biomass than the unamended control.

Biochar and enhanced phosphate capture: Mapping mechanisms to functional properties

A multi-technique analysis was performed on a range of biochar materials derived from secondary organic resources and aimed at sustainable recovery and re-use of wastewater phosphorus (P). Our purpose was to identify mechanisms of P capture in biochar and thereby inform its future optimisation as a sustainable P fertiliser. The biochar feedstock comprised pellets of anaerobically digested sewage sludge (PAD) or pellets of the same blended in the ratio 9:1 with ochre sourced from minewater treatment (POCAD), components which have limited alternative economic value. In the present study the feedstocks were pyrolysed at two highest treatment temperatures of 450 and 550 °C. Each of the resulting biochars were repeatedly exposed to a 20 mg l^-1 PO₄-P solution, to produce a parallel set of P-exposed biochars. Biochar exterior and/or interior surfaces were quantitatively characterised using laser-ablation (LA)-ICP-MS, X-ray diffraction, X-ray photo-electron spectroscopy (XPS) and scanning electron microscopy coupled with energy dispersive X-ray. The results highlighted the general importance of Fe minerals in P capture. XPS analysis of POCAD550 indicated lower oxidation state Fe2p3 bonding compared to POCAD450, and LA-ICP-MS indicated stronger covariation of Fe and S, even after P exposure. This suggests that low-solubility Fe/S compounds are formed during pyrolysis, are affected by process parameters and impact on P capture. Other data suggested capture roles for aluminium, calcium and silicon. Overall, our analyses suggest that a range of mechanisms for P capture are concurrently active in biochar. We highlighted the potential to manipulate these through choice of form and composition of feedstock as well as pyrolysis processing, so that biochar may be increasingly tailored towards specific functionality.

Can Biochar Covers Reduce Emissions from Manure Lagoons While Capturing Nutrients?

The unique physical and chemical properties of biochars make them promising materials for odor, gas, and nutrient sorption. Floating covers made from organic materials (biocovers) are one option for reducing odor and gas emissions from livestock manure lagoons. This study evaluated the potential of floating biochar covers to reduce odor and gas emissions while simultaneously sorbing nutrients from liquid dairy manure. This new approach has the potential to mitigate multiple environmental problems. Two biochars were tested: one made via gasification of Douglas fir chips at 650°C (FC650), and the other made from a mixture of Douglas fir [ (Mirb.) Franco] bark and center wood pyrolyzed at 600°C (HF600). The HF600 biocover reduced mean headspace ammonia concentration by 72 to 80%. No significant reduction was found with the FC650 biocover. Nutrient uptake ranged from 0.21 to 4.88 mg N g biochar and 0.64 to 2.70 mg P g biochar for the HF600 and FC650 biochars, respectively. Potassium ranged from a loss of 4.52 to a gain of 2.65 mg g biochar for the FC650 and HF600 biochars, respectively. The biochars also sorbed Ca, Mg, Na, Fe, Al, and Si. In a separate sensory evaluation, judges assessed odor offensiveness and odor threshold of five biocover treatments including four biochars applied over dairy manure. Reductions in mean odor offensiveness and mean odor threshold were observed in three treatments compared with the control. These results show that biochar covers hold promise as an effective practice for reducing odor and gas emissions while sorbing nutrients from liquid dairy manure.

Using FTIR-photoacoustic spectroscopy for phosphorus speciation analysis of biochars

In the last decade, numerous studies have evaluated the benefits of biochar for improving soil quality. The purposes of the current study were to use Fourier transform infrared-photoacoustic spectroscopy (FTIR-PAS) to analyse P species in biochar and to determine the effect of pyrolysis temperature on P speciation. The photoacoustic detector has a range of advantages for the very dark biochar samples in comparison to more traditional reflectance or transmission FTIR detectors. The spectra turned out to be more informative in the regions with P vibrations for biochar produced at temperatures above 400°C, where most of the remaining organic compounds were aromatic and therefore not overlapping with the P vibrations. For biochars produced from the solid fraction of digestate from biogas production, an increase in the pyrolysis temperature led to the formation of a large variety of P species. Hydroxylapatite and tricalcium phosphate were the most dominant P species in the mid to high temperature range (600-900°C), while at 1050°C apatite, iron phosphates, variscite and calcium phosphates were identified. However, the changes in P speciation in biochars produced from bone meal at different temperatures were smaller than in the biochars from digestate. Hydroxylapatite and calcium phosphates were identified in biochar produced at all temperatures, while there was some indication of struvite formation.

Optimising the recovery and re-use of phosphorus from wastewater effluent for sustainable fertiliser development

Recovery and re-use of phosphorus (P) from wastewater treatment systems as agricultural fertiliser presents an important and viable target for P waste reduction and recycling. In this study novel biochar materials for P filtration of wastewater were designed and produced using waste feedstocks, with consideration of the plant accessibility of the P captured by the biochars. The biochars were produced using batch slow pyrolysis at 450 °C and 550 °C from a) AD: anaerobically digested sewage sludge and b) OCAD: a 1:1 mixture of anaerobically digested sewage sludge and ochre, a mineral product from mine drainage treatment. A set of experiments was designed using pH buffering to provide a robust framework for assessing the P recovery capacity and affinity of the biochars compared to other potential P recovery materials (unprocessed ochre, activated carbon and zeolite). After 5 days of repeated exposure to a P solution at a wastewater-relevant concentration (0.02 g P l(-1)) replenished each 24 h, relatively high masses of P were recovered by ochre (1.73 ± 8.93×10(-3) mg P g(-1)) and the biochars OCAD550 (1.26 ± 4.66×10(-3) mg P g(-1)), OCAD450 (1.24 ± 2.10×10(-3) mg P g(-1)), AD450 (1.06 ± 3.84×10(-3) mg P g(-1)), and AD550 (0.986 ± 9.31×10(-3) mg P g(-1)). The biochar materials had higher removal rates than both activated carbon (0.884 ± 1.69×10(-2) mg P g(-1)) and zeolite (0.130 ± 1.05×10(-2) mg P g(-1)). To assess the extractability of recovered P, P exposure was followed by repeated extraction for 4 days with pH 7-buffered deionised water. The AD biochars retained 55% of the P recovered, OCAD biochars 78% and ochre 100%. Assessment of potentially toxic element concentrations in the biochars against guideline values indicated low risk associated with their use in the environment. Our successful demonstration of biochar materials highlights the potential for further development of P filters for wastewater treatment systems from anaerobic digestate produced and pyrolysed on-site with energy recovery.

Effect of Wood Biochar in Manure-Applied Sand Columns on Leachate Quality

Agricultural operations can pose a threat to the quality of nearby water sources particularly from nitrogen (N) and phosphorus (P) losses following land application of manure. Biochar application to soils has the potential to ameliorate degraded soils and reduce nutrient leaching to groundwater. The effects of amending sand soil columns with hybrid poplar biochar ( spp.) made by a slow-pyrolysis process at 450°C at varying rates (0, 1, 2, and 5% by weight) with repeated dairy manure applications over a 56-wk period was examined to evaluate the impact to leachate water quality. Increasing levels of biochar decreased cumulative levels of total N (TN) by 21 to 59%, nitrate (NO-N) by 17 to 46%, and ammonia (NH-N + NH-N) by 46 to 90% in leachate but increased cumulative leaching of total P (TP). Overall leachate pH was increased and peak levels of 5-d biological oxygen demand (BOD) in leachate after manure application were decreased with increasing levels of biochar amendment. The results from this study indicate that biochar amendments could be effective in reducing nitrogen leaching from soils, though further study is needed to determine practical application in a field setting.

Enhanced nitrate and phosphate removal in a denitrifying bioreactor with biochar

Denitrifying bioreactors (DNBRs) are an emerging technology used to remove nitrate-nitrogen (NO) from enriched waters by supporting denitrifying microorganisms with organic carbon in an anaerobic environment. Field-scale investigations have established successful removal of NO from agricultural drainage, but the potential for DNBRs to remediate excess phosphorus (P) exported from agricultural systems has not been addressed. We hypothesized that biochar addition to traditional woodchip DNBRs would enhance NO and P removal and reduce nitrous oxide (NO) emissions based on previous research demonstrating reduced leaching of NO and P and lower greenhouse gas production associated with biochar amendment of agricultural soils. Nine laboratory-scale DNBRs, a woodchip control, and eight different woodchip-biochar treatments were used to test the effect of biochar on nutrient removal. The biochar treatments constituted a full factorial design of three factors (biochar source material [feedstock], particle size, and application rate), each with two levels. Statistical analysis by repeated measures ANOVA showed a significant effect of biochar, time, and their interaction on NO and dissolved P removal. Average P removal of 65% was observed in the biochar treatments by 18 h, after which the concentrations remained stable, compared with an 8% increase in the control after 72 h. Biochar addition resulted in average NO removal of 86% after 18 h and 97% after 72 h, compared with only 13% at 18 h and 75% at 72 h in the control. Biochar addition also resulted in significantly lower NO production. These results suggest that biochar can reduce the design residence time by enhancing nutrient removal rates.

Pyrolysis temperature-dependent changes in dissolved phosphorus speciation of plant and manure biochars

Pyrolysis of plant and animal wastes produces a complex mixture of phosphorus species in amorphous, semicrystalline, and crystalline inorganic phases, organic (char) components, and within organo-mineral complexes. To understand the solubility of different phosphorus species, plant (cottonseed hull) and manure (broiler litter) wastes were pyrolyzed at 350, 500, 650, and 800 °C and exposed to increasingly more rigorous extraction procedures: water (16 h), Mehlich 3 (1 mM EDTA at pH 2.5 for 5 min), oxalate (200 mM oxalate at pH 3.5 for 4 h), NaOH-EDTA (250 mM NaOH + 5 mM EDTA for 16 h), and total by microwave digestion (concentrated HNO3/HCl + 30% H2O2). Relative to the total (microwave digestible) P, the percentage of extractable P increased in the following order: M3 < oxalate ≈ water < NaOH-EDTA for plant biochars and water < M3 < NaOH-EDTA < oxalate for manure biochars. Solution phase (31)P NMR analysis of NaOH-EDTA extracts showed the conversion of phytate to inorganic P by pyrolysis of manure and plant wastes at 350 °C. Inorganic orthophosphate (PO4(3-)) became the sole species of ≥ 500 °C manure biochars, whereas pyrophosphate (P2O7(4-)) persisted in plant biochars up to 650 °C. These observations suggested the predominance of (i) amorphous (rather than crystalline) calcium phosphate in manure biochars, especially at ≥ 650 °C, and (ii) strongly complexed pyrophosphate in plant biochars (especially at 350-500 °C). Correlation (Pearson's) was observed (i) between electric conductivity and ash content of biochars with the amount of inorganic P species and (ii) between total organic carbon and volatile matter contents with the organic P species.

Effectiveness of biochar for sorption of ammonium and phosphate from dairy effluent

The use of biochar for recovery of excess nutrients in dairy manure effluent and the use of nutrient-enriched biochar as soil amendment can offer a robust solution for multiple environmental issues. In this study we determined the capacity of biochar, produced by pyrolyzing mixed hardwood feedstock at 300°C, to adsorb and retain or release two major nutrient ions: ammonium (NH) and phosphate (PO). We conducted the experiment using a range of nutrient concentrations that represent those commonly observed in dairy manure effluent (0-50 mg L for PO and 0-1000 mg L for NH). Up to 5.3 mg g NH and 0.24 mg g PO was adsorbed from manure by biochar (18 and 50% of total amount in the manure slurry, respectively). During the desorption phase of the experiment, biochar retained 78 to 91% of the sorbed NH and 60% of the sorbed PO at reaction times <24 h. Our findings confirm that biochar can be used for recovering excess nitrogen and phosphorus from agricultural water, such as dairy manure effluent.

Environmental benefits of biochar

Understanding and improving environmental quality by reducing soil nutrient leaching losses, reducing bioavailability of environmental contaminants, sequestering C, reducing greenhouse gas emissions, and enhancing crop productivity in highly weathered or degraded soils, has been the goal of agroecosystem researchers and producers for years. Biochar, produced by pyrolysis of biomass, may help attain these goals. The desire to advance understanding of the environmental and agronomic implication of biochar utilization led to the organization of the 2010 American Society of Agronomy-Soil Science Society of America Environmental Quality Division session titled "Biochar Effects on the Environment and Agricultural Productivity." This specialized session and sessions from other biochar conferences, such as the 2010 U.S. Biochar Initiative and the Biochar Symposium 2010 are the sources for this special manuscript collection. Individual contributions address improvement of the biochar knowledge base, current information gaps, and future biochar research needs. The prospect of biochar utilization is promising, as biochars may be customized for specific environmental applications.