Swine Manure Biochar Research Articles

Techno-economic assessment of swine manure biochar production in large-scale piggeries in China

Biochar production using swine manure (SM) from large-scale piggeries is increasingly needed. However, little is known about the economic feasibility for SM biochar production. Herein, SM biochar production was simulated via Aspen Plus, and techno-economic model was applied to calculate the net present value (NPV), internal rate of return (IRR), and discounted payback period (DPP) for SM biochar production with a processing capacity of 8000 tons SM per year. Results suggest that this project is susceptible to biochar selling price and operation cost. When the biochar price is > 116 USD/ton, the NPV is positive. When the biochar selling price is increased from 154 to 193 USD/ton, the IRR is increased from 11 % to 41 %. The DPP analyses show that the investment payback period for this project is 4.6 years. Moreover, compared to conventional SM treatment routes, valorization of SM into biochar in large-scale piggery in China has a shorter investment period. Finally, this study suggests that swine manure biochar production in large-scale piggeries in China is profitable, deserving investment.

Effects of swine manure and straw biochars on fluorine adsorption-desorption in soils.

With increasing global awareness of soil health, attention must be paid to fluorine exposure in soils, which poses a threat to human health. Therefore, this study aimed to study the fluorine adsorption characteristics of swine manure and straw biochars and their impact on fluorine adsorption-desorption in soil with batch experiments. The biochar samples originated from high-temperature anaerobic cracking of swine manure (350°C, 500°C, and 650°C) and straw (500°C). Results indicated that the adsorption of soil fluorine reached adsorption equilibrium at around 4 h after the mixing of swine manure and straw biochar. Fluorine adsorption kinetics using these biochars conformed to the quasi-two-stage kinetic model. The fluorine adsorption kinetics for biochar-treated soils conformed to the double-constant equation and the Elovich equation, and the soil treated with straw biochar showed the fastest fluorine adsorption rate. The adsorption isotherms of fluorine for biochars and biochar-treated soils could be fitted by the isothermal adsorption model of Langmuir and Freundlich. The maximal equilibrium quantity of fluorine was 73.66 mg/g for swine manure biochar. The soil, adding with 2% of swine manure biochar achieved with showed at 650°C had the smallest adsorption. This study also shows that the adsorption of fluorine by biochar gradually decreased with the increase of pH. Comparing with other factors, the mixture pH with biochars added had a significant effect on fluorine adsorption. The decreased fluorine adsorption capacities for soils treated with swine manure and straw biochars were closely related to the increased pH in soils after adding biochars. Considering the fluorine threat in soil, this study provides a theoretical basis for the application of biochars on soil fluorine adsorption.

Persistent effects of swine manure biochar and biogas slurry application on soil nitrogen content and quality of lotus root.

Using swine manure biochar and biogas slurry in agriculture proves to be an effective strategy for soil improvement and fertilization. In this study, a pot trial on the growth of lotus root was conducted to investigate the persistent effects of applying 350°C swine manure biochar (1% and 2%) and biogas slurry (50% and 100%) on soil nitrogen nutrient and lotus root quality. The results showed that compared to chemical fertilizer alone (A0B0), swine manure biochar significantly increased soil nitrogen content after one year of application. The contents of total nitrogen (TN), alkali-hydrolyzed nitrogen (AHN), ammonium nitrogen (NH4 +-N), and nitrate nitrogen () increased by 17.96% to 20.73%, 14.05% to 64.71%, 17.76% to 48.68% and 2.22% to 8.47%, respectively, during the rooting period. When swine manure biochar was present, the application of biogas slurry further elevated soil nitrogen content. The co-application of swine manure biochar and biogas slurry significantly increased soil nitrogen content, and the 100% nitrogen replacement with biogas slurry combined with 2% swine manure biochar (A2B2) treatment exhibited the most significant enhancement effect during whole plant growth periods. Soil enzyme activities, including soil protease (NPT), leucine aminopeptidase (LAP), b-glucosidase (β-GC) and dehydrogenase (DHA), showed a tendency to increase and then decrease with the prolongation of lotus root fertility period, reaching the maximum value during the rooting period. Compared to A0B0, the treatment with 2% swine manure biochar had the most significant effect on enzyme activities and increased the lotus root's protein, soluble sugar, and starch contents. Nitrate content decreased with the application of 2% swine manure biochar as the amount of biogas slurry increased. In conclusion, swine manure biochar effectively improved soil nitrogen content, enzyme activity, and lotus root quality. Even after one year of application, 2% swine manure biochar had the best enhancement effect.

The Impact of Swine Manure Biochar on the Physical Properties and Microbial Activity of Loamy Soils.

Biochar has been proven to influence soil hydro-physical properties, as well as the abundance and diversity of microbial communities. However, the relationship between the hydro-physical properties of soils and the diversity of microbial communities is not well studied in the context of biochar application. The soil analyzed in this study was collected from an ongoing field experiment (2019–2024) with six treatments and three replications each of biochar (B1 = 25 t·ha−1 and B0 = no biochar) and nitrogen fertilizer (N1 = 160, N2 = 120 kg·ha−1, and N0 = no fertilizer). The results show that biochar treatments (B1N0, B1N1, and B1N2) significantly improved the soil bulk density and total soil porosity at different depths. The B1N1 treatment substantially enhanced the volumetric water content (VMC) by 5–7% at −4 to −100 hPa suction at 5–10 cm depth. All three biochar treatments strengthened macropores by 33%, 37%, and 41%, respectively, at 5–10 cm depth and by 40%, 45%, and 54%, respectively, at 15–20 cm depth. However, biochar application significantly lowered hydraulic conductivity (HC) and enhanced carbon source utilization and soil indices at different hours. Additionally, a positive correlation was recorded among carbon sources, indices, and soil hydro-physical properties under biochar applications. We can summarize that biochar has the potential to improve soil hydro-physical properties and soil carbon source utilization; these changes tend to elevate fertility and the sustainability of Cambisol.

Treatment of Pb(II) pollution in livestock wastewater by MgFe2O4 modified manure-biochar derived from livestock itself: Special role of endogenous dissolved organic matter and P species

In this work, swine manure biochar (SC) and its MgFe2O4 modified product (MFSC) were fabricated by hydrothermal method to remove Pb(II) pollution from livestock wastewater. The physicochemical properties of materials were analyzed by BET, XRD, SEM and VSM. The MFSC showed abundant pore structure, high MgFe2O4 dispersion and superior magnetization, which improved its application prospect and the capacity of pollutant removal. The results of adsorption experiments showed that MFSC has much higher Pb(II) adsorption efficiency (242.723 mg/g) than SC (42.158 mg/g), and chemical adsorption was the main removal pathway of Pb(II). The modification of MgFe2O4 changed the character of endogenous dissolved organic matter (EDOM) of MFSCs, producing more polysaccharides that could be complexed with Pb(II), further influencing the adsorption process. In addition, the addition of MgFe2O4 stimulated the activity of P for Pb(II) removal via converting organic P into inorganic P, as well increasing the percentage of Fe/Al mineral adsorbed P. The chemical precipitation of hydroxylpyromorphite (Pb5(PO4)3OH) was identified as the major pathway for Pb(II) adsorption. In conclusion, MFSC has the potential to be a novel composite for the treatment of heavy metals in livestock wastewater, and this study could be of great significance to achieve the sustainable development of the livestock industry.

Comparative study on characteristics and mechanism of levofloxacin adsorption on swine manure biochar

This study evaluated the relationship between pyrolysis temperature (300–900 ℃), characteristics of swine manure (SM)-derived biochar (BC), and its adsorption of levofloxacin (LEV). The surface structure and chemistry of SM-derived BCs were characterized using Brunauer-Emmett-Teller analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. According to the characteristic analysis, the surface area and graphitization degree of SM-derived BC increased as temperature rose. The highest adsorption capacity was achieved by BC-900 (158 mg/g); this level was higher than that achieved in previous studies and comparable to that of commercial activated carbons. Characterization and adsorption experiments indicated that pore-filling, π–π stacking interaction, π–π electron donor–acceptor, H-bonding, and hydrophobic interactions each played a critical role in the adsorption of LEV on SM-derived BC. Collectively, this study confirms the potential utility of SM-derived BC for the removal of antibiotics.

Comparative study on the characteristics and environmental risk of potentially toxic elements in biochar obtained via pyrolysis of swine manure at lab and pilot scales

Pyrolysis is considered as a promising method to immobilize potentially toxic elements (PTEs) in animal manures. However, comparative study on characteristics and environmental risk of PTEs in biochar obtained by pyrolysis of animal manure at different reactors are lacking. In this study, swine manure was pyrolyzed at 300–600 °C in a lab-scale or pilot-scale reactor with the aim to investigate their effects on characteristics and environmental risk of As, Cd, Cu, Ni, Pb, and Zn in swine manure biochar. Results showed that biochars produced from pilot scale had lower pH and carbon (C) content but higher oxygen (O) content than those from lab scale. Biochars from pilot scale had higher total PTEs (except Cd) concentrations and releasable PTEs (except Pb) but lower CaCl2-extractable PTEs and phytotoxicity germination index (GI) to radish seedings than those from lab scale. Chemical speciation analysis indicated that PTEs in biochar produced from pilot-scale fast pyrolysis at 400 °C had higher percentage of more stable fraction (F5 fraction) and lower potential ecological risk index (RI) than those from lab-scale slow pyrolysis. These findings demonstrated that bioavailability and potential ecological risk of PTE in swine manure biochar were greatly decrease in the pilot-scale pyrolysis reactor and the optimum temperature was 400 °C considering the lowest potential ecological risk index.

Effect of Pyrolysis Temperature on the Characteristics and Levofloxacin Adsorption Capacity of Swine Manure Biochar

Effect of Pyrolysis Temperature on the Characteristics and Levofloxacin Adsorption Capacity of Swine Manure Biochar

Effects of Biochar Application on Enzyme Activities in Tea Garden Soil.

Animal-manure biochar used as a sustainable amendment to garden soil has been widely applied, and the animal-manure pyrolysis temperatures would also have a regulatory effect on soil functions because of their affections on biochar physio-chemical properties. Here we studied the effects of different dosages of swine-manure biochar on tea garden soil functions, with the swine-manure pyrolysis temperature differed at 350 and 500°C. The results showed that the improvement of soil microbial biomass carbon and nitrogen and enzyme activities was closely related to the addition of 0.5–2% (biochar wt/soil wt) swine-manure biochar. Under different conditions of different carbon application rates and carbon type, the addition of 2% swine-manure biochar pyrolyzed at 350°C showed the best effects on soil enzyme activities and microbial biomass carbon and nitrogen contents. Compared to the control, after the addition of 2% swine-manure biochar, sucrase, phosphatase, catalase, and urease activities increased by 63.3, 23.2, 50.3, and 27.9%, respectively. Microbial biomass carbon and nitrogen contents also increased by 36.4 and 34.3%, respectively. Our study indicated that the effectiveness of using animal-manure swine-manure biochar as a sustainable amendment to soil would provide evidence of tea garden soil improvement and the environmental response to the usage of biochars.

Speciation and environmental risk of heavy metals in biochars produced by pyrolysis of chicken manure and water-washed swine manure

This study was conducted to investigate the speciation, bioavailability and environmental risk of heavy metals (HMs) in chicken manure (CM) and water-washed swine manure (WSM) and their biochars produced at different pyrolysis temperatures (200 to 800 °C). As the pyrolysis temperature increased, the remaining proportion, toxicity characteristic leaching procedure (TCLP), HCl and diethylenetriamine pentaacetic acid (DTPA) of HMs gradually declined. This result proved that the speciation of HMs in chicken manure biochars (CMB) and water-washed swine manure biochars (WSMB) was influenced by pyrolysis temperature. The proportions of stable fractions were enhanced with increased pyrolysis temperature and weakened the HM validity for vegetation at 800 °C. Finally, the results of the risk assessment showed that the environmental risk of HMs in CMB and WSMB decreased with increasing pyrolysis temperature. Therefore, pyrolysis at 800 °C can provide a practical approach to lessen the initial and underlying heavy metal toxicity of CMB and WSMB to the environment.

Effect of a low-cost and highly efficient passivator synthesized by alkali-fused fly ash and swine manure on the leachability of heavy metals in a multi-metal contaminated soil

Soil pollution, caused by heavy metals, is an environmental problem that requires an urgent solution in China. Chemical passivation is a technology that uses various passivators to reduce the availability of heavy metals in soil and realize the remediation of contaminated soil. In this study, we examined the effects of fly ash (FA), alkali-fused fly ash (AFFA), swine manure biochar (SB), and modifying biochar (MB) on the leachability of Cu, Zn, Pb, and Cd via soil culture experiments. The results showed that the addition of AFFA, SB, and MB significantly reduced the extractable contents of Cu, Pb, and Cd in the soil. AFFA and MB had the best passivation effect, followed by SB and FA. The passivation effect on Pb was the best, followed by that on Cu and Cd. AFFA modification significantly improved the passivation effect of MB on Cu, Pb, and Cd in composite contaminated soil. With the addition of 3% MB, the Pb, Cu, and Cd extracted by TCLP decreased by 95.7, 74.1, and 59.1%, respectively. Correlation analysis, Fourier transform infrared spectrometry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy showed that the passivation mechanism is mainly due to an increase in the soil pH, silicate content, and cohesiveness. The soil culture experiments in this study proved that MB is a low-cost and highly efficient organic-inorganic composite passivator for multi-metal contaminated soils.

Effects of aging on surface properties and endogenous copper and zinc leachability of swine manure biochar and its composite with alkali-fused fly ash

Biochar aging is a key factor leading to the decline of biochar stability and the release of endogenous pollutants. This study investigated the effects of five artificial and simulated aging processes on the surface properties and endogenous copper (Cu) and zinc (Zn) leachability of swine manure biochar and its composite with alkali-fused fly ash. Aging obviously reduced carbon (C) content on the surface of swine manure biochar and increased oxygen (O) content. Among all the aging treatments, high-temperature aging had the greatest effect on C content. Following the aging treatments, the C–C bond contents on the surfaces of swine manure biochar decreased significantly, whereas the C–O bonds increased significantly; however, there were less changes in the amounts of C–C and C–O bonds on the surfaces of modified biochar than on swine manure biochar. Aging significantly enhanced the leaching toxicity of Cu and Zn, and Zn availability and bioaccessibility in swine manure biochar and modified biochar. However, it minimized Cu availability and bioaccessibility, especially under high-temperature aging. Greater amounts of Zn than Cu were extracted from swine manure biochar and modified biochar. However, under all the aging treatments, the leaching toxicity, availability, and bioaccessibility of Cu and Zn in modified biochar were significantly lower than in swine manure biochar. This implies that modified biochar application poses lower environmental risks than swine manure biochar.

Effects of swine manure biochar on sorption equilibrium of cadmium and zinc in sandy soils

Swine manure is an agricultural waste that can increase soil fertility. However, this residue has a high content of heavy metals, particularly zinc (Zn) and cadmium (Cd), that are not only toxic to plants and soil organisms but they also pose a great threat to human health due to the potential accumulation of these metals through the food chain. Transforming swine manure into biochar and adding it to soils can improve the soil’s capacity to retain heavy metals. The main objective of this research was to study the capacity of sandy soils mixed with different doses of swine manure biochar (SMB) to retain Cd and Zn as well as to evaluate the sorption equilibrium of these metals. Sorption essays were performed by adding solutions of Zn (ZnCl2) or Cd (CdCl2) at different concentrations (0, 2.5, 5, 10, 50 and 100 mg L-1) to soil samples mixed with different doses of SMB (0, 0.25, 0.75, 1.5, and 3.0 % (w/w)). The data were modelled using both Langmuir and Freundlich adsorption isotherm models to describe the adsorption processes. The data were best represented by the Langmuir model (R2>0.97), indicating a mono-layer sorption to the surface. Results showed that sorption capacity of Zn and Cd increased with the dose of SMB, improving metal retention. The Langmuir constant (KL) for soil without SMB for Cd and Zn were 0.01 L mg-1 and 0.05 L mg-1, respectively. With the highest dose of SMB, KL increased to 9.86 L mg-1 and 1.26 L mg-1 for Cd and Zn, respectively. Results suggest that SMB has the potential to mitigate Zn and Cd contamination of sandy soils.

Immobilization of heavy metals (Cd, Zn, and Pb) in different contaminated soils with swine manure biochar

ABSTRACT To explore the feasibility of biochar for reducing mobility and bioavailability of heavy metals in different contaminated soils, batch incubation experiments including column leaching and pot experiments were conducted to investigate the effects of biochar input on soil pH, the bioavailability of heavy metals (Cd, Zn, and Pb) and their species in three different contaminated soils treated with different swine biochar application rates. The results show that biochar has more potential for pH improvement in acidic soils than neutral and alkaline soil. After 42 d incubation, the pH values of the acidic soils increased from 5.90 to 7.23, while the pH values of neutral/alkaline soils did not change significantly. The available heavy metals showed a decreasing trend as the biochar application rate increases. The order of the immobilization effect is Pb>Zn>Cd. Possible immobilization mechanisms are mainly ion exchange, complexation, π bond action and precipitation on the surface of biochar.

Effects of pyrolysis temperature on properties of swine manure biochar and its environmental risks of heavy metals

Converting swine manure into biochar has increasingly been considered a useful method to reduce heavy metal (HM) availability; however, the associated environmental risks need further exploration. In this study, swine manure was pyrolyzed at diff ;erent temperatures ranging from 200 to 700 °C; this was aimed at studying the effect of temperature on the swine manure biochar properties, while elucidating the environmental risks of HMs. The aromaticity and oxidation-resistance stability of biochar improved with an increase in the pyrolysis temperature. Cu and Zn concentration in biochar (except 200 °C) were significantly higher than manure (maximum increase of 91.9 % for Cu and 85.1 % for Zn). The residual ratios (R) of Cu and Zn gradually decreased as the temperature increased from 200 to 500 °C and increased over 500 ℃. The R of Cd decreased dramatically as the temperature increased from 200 to 700 °C (79.1 % at 200 °C versus 1.34 % at 700 °C). The HM speciation in biochar was affected by the temperature. High temperatures caused HMs to transition from unstable to stable fractions, thereby reducing the leaching toxicity and environmental risks. There was also a significant correlation between the potential ecological risk index and the O/C ratio (Regression coefficients (R2) = 0.98, P-value of a hypothesis test (p) <0.01), indicating that the O/C index is a good tool to assess the environmental risks of HMs in biochar. Based on the environmental risk assessment value, this study highlights that pyrolysis at 600 °C is probably the most optimal temperature condition for treating livestock manure with high concentrations of Cu, Cd, and Zn.

Valorization of swine manure biochar as a catalyst for transesterifying waste cooking oil into biodiesel

As demand of proteins from meats has significantly increased with economy growth, the population of livestock proliferates. Thus, heavy amount of livestock byproducts released from livestock industries will become more problematic if they are handled in an unsatisfactory manner. In this study, swine manure (SM) waste was directly valorized to be used as a reaction catalyst for biodiesel production. Pyrolysis was adapted to produce swine manure biochars at 500 (SMB@500) and 650 °C (SMB@650), and the materials were used for conversion of waste cooking oil into biodiesels (i.e., fatty acid methyl esters: FAMEs). The properties of SMBs and resulting pyrolytic gases (i.e., H2, CO, and C1-2 hydrocarbons (HCs)) and liquids during pyrolysis were also characterized. SMBs used in this study included a large quantity of metallic contents that significantly contributed to the rapid reaction for biodiesel production. In detail, SMB@500 and SMB@650 showed higher than 96% of FAME yield at 305 and 210 °C of reaction temperature, while non-catalytic reaction using SiO2 showed similar FAME yield at 330 °C. Thus, this work offers a sustainable way to recycle organic and inorganic materials in livestock manures for energy (biodiesel, pyrolytic oil, H2, and C1-2 HCs) production.

Effect of rice straw and swine manure biochar on N2O emission from paddy soil

We analyzed the effects of rice straw biochar (RSBC) and swine manure biochar (SMBC) on N2O emission from paddy soil. The biochars were added to soil at the rates of 1% and 5% (w/w), and N2O emission, soil properties and soil enzyme activities were determined at the elongation, heading and maturation stages of rice growth. The N2O flux started within 2 h of adding the biochar, and decreased significantly thereafter during the three growth stages. The cumulative N2O emission was suppressed by 45.14–73.96% following biochar application, and 5% SMBC resulted in the lowest cumulative emission. In addition, biochar application significantly increased soil pH, soil organic carbon (SOC), NO3− levels and urease activity, and decreased soil NH4+ and nitrate reductase activity. Regression analysis indicated that cumulative N2O emission was correlated positively to NH4+, and negatively to soil pH, SOC and NO3−. SEM further revealed that biochar application weakened the denitrification process, and the NH4+ level had the most significant impact on N2O emission. Taken together, RSBC and SMBC regulated the nitrogen cycle in paddy soil and mitigated N2O emission by increasing soil pH, decreasing nitrate reductase activity and NH4+ content.

Biochar-mediated Fenton-like reaction for the degradation of sulfamethazine: Role of environmentally persistent free radicals

Swine manure biochar (SBC) pyrolyzed at 300 °C, 600 °C and 900 °C were utilized to degrade sulfamethazine (SMT) in heterogeneous Fenton-like systems which achieved excellent degradation efficiency (over 85% in 30 min). Experiments results demonstrated that SBC possessed the poor SMT adsorption capacity but high catalytic performance. Electron Paramagnetic Resonance (EPR) and X-ray photoelectron spectroscopy (XPS) analysis revealed that there were oxygen-centered environmentally persistent free radicals (EPFRs) and carbon-centered EPFRs with an adjacent oxygen atom in SBC. The oxygen-centered EPFRs played a major role in the catalytic process which tended to convert to carbon-centered EPFRs after the reaction. Besides, the electron transfer pathways were the most likely catalytic mechanism of SBC and the contribution of OH was dominant through Electron capture experiments and Linear sweep voltammetry (LSV) measurements. The acidic or alkaline condition can promote the catalytic ability of SBC. The presence of dissolved salts (NaCl) inhibited the catalytic process but the inhibition was slightly weakened at high concentration of NaCl, which showed the high tolerance of Cl− in Fenton/Fenton-like systems. Moreover, real wastewater application suggested that SBC600/H2O2 system possessed excellent catalytic efficiency and good adaptability. This research provides a novel swine manure reuse process with high practicability and presents a more explicit perspective about the reaction mechanisms of EPFRs in biochar.

Characterization and carbon mineralization of biochars produced from different animal manures and plant residues

Renewing carbon and re-establishing it again in the soil is one of the valuable means to cope with climate change. There are many technologies for carbon apprehension and storage, but the most important one gaining attention is biochar technology. So, to carbonize and return different biological materials back to the farmland, a comprehensive study was proposed to characterize and evaluate the carbon (C) mineralization of biochars produced from different animal manures and crop straws. Six types of biochars were prepared from animal manures (poultry litter, swine and cattle manures) and crop straws (rice, soybean, and corn straws). The biochars were analyzed for chemical characteristics (elemental variables, thermal decomposition, cation exchange capacity, pH, electrical conductivity, specific surface area, and surface functional groups) and an incubation experiment was conducted to evaluate C mineralization from soil biochar mixture. Biochars produced from crop straws resulted to have more C as compared to the biochars produced from animal manures. Concentration of nitrogen was low, while P, K, Ca, and Mg were found reasonably higher in all biochars except swine manure biochar. The plant-derived biochars presented lower CO2 emissions when incorporated to soil at 1 and 2% of C. Varying but all the biochars prepared represented an alkaline pH. Biochars prepared from the crop straws resulted to have more C, alkaline in nature, high CEC, low CO2 emissions, can sequester C and more suitable to enhance the soil fertility in comparison to biochars produced from other sources.

Mechanisms underlying the mitigation of both N2O and NO emissions with field-aged biochar in an Anthrosol

The mechanisms associated with N2O and NO processes following biochar application remain unclear in an Anthrosol under intensively vegetable production. An incubation experiment with 15N tracing technique and quantitative polymerase chain reaction (qPCR) was performed to investigate the responses of pathways and the microbial mechanisms of N2O and NO production to the application of wheat biochar (Bw) and swine manure biochar (Bm) field aged for one year in an Anthrosol under 60% water holding capacity. The application of both types of biochar decreased the cumulative N2O emissions by 12.9–20.0%, with an obvious mitigation effect observed after Bw application. The reduction in N2O emissions derived from autotrophic nitrification and denitrification induced by biochar were coupled with a decrease in ammonia-oxidizing bacteria (AOB) amoA abundance and the ratio of (nirK + nirS)/nosZ, respectively. Biochar increased the relative contribution of heterotrophic nitrification by 54.2–58.3%, with stronger stimulating effects from the Bm amendment than from the Bw amendment. Moreover, cumulative NO emissions were strongly reduced by an average of 35.5% by biochar, with no differences between Bw and Bm. Furthermore, covariation in NO flux and NO2−–N content, together with the alternations in the abundance of AOB amoA, indicated that nitrifier denitrification might play a vital role in NO emissions. The present study highlights biochar’s promising effects on mitigating N2O and NO emissions by weakening autotrophic nitrification and denitrification processes. Meantime, heterotrophic nitrification should be taken into consideration when comprehensively assessing the mitigation potential of biochar.