Inert Carbon Research Articles

Effects of Short-term Nitrogen Addition on Soil Organic Carbon Components in Robinia pseudoacacia L. Plantation

Nitrogen (N) deposition in the context of human activities continuously affects the carbon cycle of ecosystems. The effect of N deposition on soil organic carbon is related to the differential responses of different carbon fractions. To investigate the changes in soil organic carbon fraction and its influencing factors in the context of short-term N deposition, four N addition gradients:0 (CK), 1.5 (N1), 3 (N2), and 6 (N3) g·(m2·a)-1 were set up in acacia plantations based on field N addition experiments, and the soil physicochemical properties, microbial biomass, and enzyme activities were measured in June and September. The results showed that:① exogenous N input reduced soil pH, promoted the increase in soluble organic carbon content, and increased soil nitrogen effectiveness. ② Short-term N addition significantly reduced soil organic carbon content, and the response of each component of organic carbon to N addition was different. Among them, the content of easily oxidized organic carbon was significantly reduced and reached the lowest value under the N2 treatment, with 54.4% and 48.2% reduction compared with that of the control, respectively, and the content of inert organic carbon increased, although the increase was not significant. Nitrogen addition reduced the soil carbon pool activity and improved the stability of the soil carbon pool. Soil carbon pool activity reached its lowest under the N3 and N2 treatments, with a decrease of 53.3% and 52.80%, respectively, compared to that of the control. ③Random forest modeling indicated that the soil microbial biomass stoichiometry ratio, microbial biomass carbon, and AP were the key factors driving the changes in soil organic carbon activity under short-term N addition, explaining 65.96% and 66.68% of the changes in oxidizable organic carbon and inert organic carbon, respectively. Structural equation modeling validated the results of the random forest modeling, and soil microbial biomass stoichiometric ratios significantly influenced carbon pool activity. Short-term nitrogen addition changed soil microbial biomass and its stoichiometric ratio in the acacia plantation forest mainly through two pathways, i.e., increasing soil nitrogen effectiveness and promoting soil acidification and inhibiting extracellular carbon hydrolase activity, thus changing the soil carbon fraction ratio and participating in the soil organic carbon cycling process.

Unveiling the complementary mechanism in the one-pot synthesis of glycerol carbonate from CO2 and glycerol

The chemical conversion of inert carbon dioxide (CO2) into high value-added chemicals is a continuing challenge. In this work, an experimental and theoretical mechanism study is presented for one-pot synthesis of glycerol carbonate (GC) from CO2, glycerol (Gly), and propylene epoxide (PO) catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-enenium iodide (HDBUI) ionic liquid. 92% GC yield was obtained in the one-pot reaction through cycloaddition of CO2 with PO to produce propylene carbonate (PC), followed by transesterification of Gly with PC to yield targeted products. Density functional theory (DFT) calculations were used to unveil the HDBUI-mediated catalytic mechanism and key catalytic species. It was revealed that the HDBUI-catalyzed cycloaddition was assisted by the hydrogen bond donor Gly, the transesterification reactant, by promoting the ring-opening of PO and the insertion of CO2. By activating Gly hydroxyl group, alkaline HDBUI-bonded propan-1-ylium-2-yl carbonate, an intermediate in cycloaddition, catalyzed transesterification. The complementary mechanism of cycloaddition and transesterification in the one-pot provides a feasible method for utilizing inert CO2.

The implication from six years of field experiment: the aging process induced lower rice production even with a high amount of biochar application

The single high-dose application of biochar to increase rice yield has been well reported. However, limited information is available about the long-term effects of increasing rice yield and soil fertility. This study was designed to perform a 6-year field experiment to unveil the rice yield with time due to various biochar application strategies. Moreover, an alternative strategy of the Annual Low dose biochar application (AL, 8 × 35% = 2.8 t ha−1) was also conducted to make a comparison with the High Single dose (HS, 22.5 t ha−1), and annual Rice Straw (RS, 8 t ha−1) amendment to investigate the effects on annual rice yield attributes and soil nutrient concentrations. Results showed that the rice yield in AL with a lower biochar application exceeded that of HS significantly (p < 0.05) in the 6th experimental year. The rice yield increased by 14.3% in RS, 10.9% in AL, and 4.2% in HS. The unexpectedly higher rice yield in AL than HS resulted from enhanced soil total carbon (TC), pH, and available Ca. However, compared to AL, liable carbon fraction increased by 33.7% in HS, while refractory carbon fraction dropped by 22.3%. Likewise, biochar characterization showed that more oxygen functional groups existed in HS than in AL. Decreasing inert organic carbon pools due to the constant degradation of the aromatic part of biochar in HS led to a lower soil TC than AL, even with a higher amount of biochar application. Likewise, the annual depletion lowered the soil pH and available Ca declination in HS. Based on the obtained results, this study suggested AL as a promising strategy to enhance rice productivity, soil nutrient enrichment, and carbon sequestration in the paddy ecosystem.Graphic abstract

Organic matter degradation causes enrichment of organic pollutants in hadal sediments

Burial of persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) in deep-sea sediments contributes to 60% of their historical emissions. Yet, empirical data on their occurrence in the deep-ocean is scarce. Estimates of the deep-ocean POP sink are therefore uncertain. Hadal trenches, representing the deepest part of the ocean, are hotspots for organic carbon burial and decomposition. POPs favorably partition to organic carbon, making trenches likely significant sinks for contaminants. Here we show that PCBs occur in both hadal (7720–8085 m) and non-hadal (2560–4050 m) sediment in the Atacama Trench. PCB concentrations normalized to sediment dry weight were similar across sites while those normalized to sediment organic carbon increased exponentially as the inert organic carbon fraction of the sediment increased in degraded hadal sediments. We suggest that the unique deposition dynamics and elevated turnover of organic carbon in hadal trenches increase POP concentrations in the deepest places on Earth.

Selective degradation of organic micropollutants by activation of peroxymonosulfate by Se@NC: Role of Se doping and nonradical pathway mechanism

In this study, Se@NC-x decorated with Se was successfully prepared via two-step calcination with zeolitic imidazole framework (ZIF) as a precursor. Mechanistic studies show that PMS would be adsorbed onto the surface of Se@NC-900 to form an active complex (Se@NC-900/PMS*), and the active Se@NC-900/PMS* could oxidize phenol by the rapid decomposition of PMS. Specifically, electrons are extracted by Se@NC-900/PMS* and then transferred to the surface of Se@NC-900, which can trigger the degradation of phenol. Notably, it is found that the local charge redistribution caused by the doping of Se can activate the catalytic potential of the intrinsically inert carbon skeleton through density flooding theory (DFT) calculations. The XLogP, ΔE, VIP, and ELUMO (Se@NC/PMS)-HOMO (pollutants) and degradation rate constants of different micropollutants were correlated well linearly. This indicates that the Se@NC-900/PMS system has a great selectivity for the degradation of pollutants. Overall, these findings not only illustrate the role of Se in tuning the electronic structure of Se@NC-x to enhance the activation of PMS, but also bridge the gap in our knowledge about the physicochemical properties and degradation performance of Se@NC catalysts.

Rücktitelbild: Bor‐Zentrierte Lewis‐Supersäuren durch Redoxaktive Liganden: Anwendung in der C‐F‐ und S‐F‐Bindungsaktivierung (Angew. Chem. 13/2023)

One-electron oxidation converts the ferrocene-substituted borane into a Lewis superacid, as reported by Frank Breher, Jan Paradies, and co-workers in their Communication (e202216959). The Lewis superacid activates almost inert carbon–fluorine and sulfur–fluorine bonds for reductions, alkylations, and arylations to form new chemical bonds.

Back Cover: Boron‐Centered Lewis Superacid through Redox‐Active Ligands: Application in C−F and S−F Bond Activation (Angew. Chem. Int. Ed. 13/2023)

One-electron oxidation converts the ferrocene-substituted borane into a Lewis superacid, as reported by Frank Breher, Jan Paradies, and co-workers in their Communication (e202216959). The Lewis superacid activates almost inert carbon–fluorine and sulfur–fluorine bonds for reductions, alkylations, and arylations to form new chemical bonds.

In Situ Reconstruction of Metal Oxide Cathodes for Ammonium Generation from High-Strength Nitrate Wastewater: Elucidating the Role of the Substrate in the Performance of Co3O4-x.

In situ electrochemical reconstruction is important for transition metal oxides explored as electrocatalysts for electrochemical nitrate reduction reactions (ENRRs). Herein, we report substantial performance enhancement of ammonium generation on Co, Fe, Ni, Cu, Ti, and W oxide-based cathodes upon reconstruction. Among them, the performance of a freestanding ER-Co3O4-x/CF (Co3O4 grown on Co foil subjected to electrochemical reduction) cathode was superior to its unreconstructed counterpart and other cathodes; e.g., an ammonium yield of 0.46 mmol h-1 cm-2, an ammonium selectivity of 100%, and a Faradaic efficiency of 99.9% were attained at -1.3 V in a 1400 mg L-1 NO3--N solution. The reconstruction behaviors were found to vary with the underlying substrate. The inert carbon cloth only acted as a supporting matrix for immobilizing Co3O4, without appreciable electronic interactions between them. A combination of physicochemical characterizations and theoretical modeling provided compelling evidence that the CF-promoted self-reconstruction of Co3O4 induced the evolution of metallic Co and the creation of oxygen vacancies, which promoted and optimized interfacial nitrate adsorption and water dissociation, thus boosting the ENRR performance. The ER-Co3O4-x/CF cathode performed well over wide ranges of pH and applied current and at high nitrate loadings, ensuring its high efficacy in treating high-strength real wastewater.

Promoted coke resistance of Ni by surface carbon for the dry reforming of methane

Dry reforming of methane (DRM) is an efficient process to transform methane and carbon dioxide to syngas. Nickel could show good catalytic activity for DRM, whereas the deactivation of nickel surfaces by the formation of inert carbon structures is inevitable. In this study, we carry out a detailed investigation of the evolution and catalytic performance of the carbon-covered surface structure on Ni(100) with a combined density functional theory and microkinetic modeling approach. The results suggest that the pristine Ni(100) surface is prone to carbon deposition and accumulation under reaction conditions. Further studies show that over this carbon-covered reconstructed Ni(100) surface, a carbon-based Mars-van-Krevelen mechanism would be favored, and the activity and coke resistance is promoted. This surface state and reaction mechanism were rarely reported before and would provide more insights into the DRM process under real reaction conditions and would help design more stable Ni catalysts.

Carbon-Hybridized Hydroxides for Energy Conversion and Storage: Interface Chemistry and Manufacturing.

Carbon-hybridized hydroxides (CHHs) have been intensively investigated for uses in the energy conversion/storage fields. Nevertheless, the intrinsic structure-activity relationships between carbon and hydroxides within CHHs are still blurry, which hinders the fine modulation of CHHs in terms of practical applications to some degree. This review aims to figure out the intrinsic role of carbon materials in CHHs with a focus on the interface chemistry and the engineering strategy in-between two components. The fundamental effects of the carbon materials in enhancing the charge/mass transfer kinetics are first analyzed, particularly the extra electron pathways for fast charge transfer and the anchoring sites for boosting the mass transfer. Subsequently, the surface-guided/confined effects of carbon materials in CHHs to modify the morphology and tailor the hydroxides, and functional heterojunction for regulating the inner electronic structure are decoupled. The methods to efficiently construct a stable yet robust solid-solid heterointerface are summarized, including oxygen functional groups engrafting, topological defective sites construction and heteroatom incorporation to activate the inert carbon surface. The smart CHHs in some typical energy applications are demonstrated. Additionally, the methodologies that can reveal the hybridization electron configuration between two components are summed up. At last, the perspective and challenges faced by the CHHs for energy-related applications are outlined.

Multiscale interfacial enhancement of surface grown carbon nanotubes carbon fiber composites

AbstractThe interface properties between surface grown carbon nanotubes carbon fiber (CNTs‐CF) and epoxy resin were investigated by different modification methods. The X‐ray photoelectron spectrometer probations show that the pristine CNTs‐CF has very low contents of both oxygen element and active carbon element. Taking the naked carbon fiber (CF) without CNTs grown as a reference, the interfacial shear strength (IFSS) of CNTs‐CF/epoxy is only 5.6% higher. After heat treatment, chemical modification and sizing treatments, the surface chemical activity of CNTs‐CF is improved considerably. In contrast with the IFSS of standard CF/epoxy, the interfacial strength of chemical‐treated CNTs‐CF‐E1/epoxy is increased to 122.8 MPa by 29.7%. The increasing content of the epoxy active groups at the modified CNTs‐CF‐E1 surface is conducive to forming covalent bonds between the epoxy resin and the CNTs‐CF‐E1 surface particularly the activated nanotube surface. The enhancement of CNT/epoxy interface is beneficial to the over whole interface property of the composites. Hence, the compressive and torsion strength of sizing CNTs‐CF‐E1 bundle combined with epoxy resin are increased by 32.4% and 14.1%, respectively. The SEM images show the failure morphologies of different modification methods, and the enhancement mechanism of multiscale interface is further clarified. Compared with chemical treatment, heat treatment can remove the inert amorphous carbon on the CNTs‐CF fiber surface and improve the interface adhesion of CNT/epoxy and CF/epoxy, and surface sizing treatment improves the CF/epoxy interface. The enhancement mechanisms of these modified CNTs‐CFs/epoxy should be ascribed to the competition and synergetic effects of the multiscale interfaces, including CNT/CF, CNT/epoxy, and CF/epoxy.

Comprehensive Review on Synthesis, Applications, and Challenges of Graphene Quantum Dots (GQDs)

Carbon-based nanomaterials are contemporary and are outpacing the technology platform. Graphene quantum dots (GQDs) had a significant impact on the subject of bioengineering, pharmaceuticals, biomedicine, biosensors, fuel, energy, etc. Depending on how quickly this field is developing, it is important to recognize the new difficulties that GQDs have to overcome. This is incredibly significant because many novel applications and innovations that have made GQD synthesis easier recently have not been systematically evaluated in prior studies. Their ability to combine the benefits of quantum dots, sp2 carbon materials (large specific surface area), and have rich functional groups at the edge makes them special. The naturally occurring inert carbon helps to stabilize chemical and physical characteristics and makes significant advancements in the creation of benchmark photocatalysts. Moreover, current challenges and potential of these rapidly developing GQDs are emphasized. The future of GQD research is limitless, according to the assessment in this review, notably if future research focuses on simplicity of purification and ecofriendly synthesis. This feature article offers a realistic summary on recent developments in the synthesis, characteristics, and uses of GQDs. Frequent review articles focusing on the progress of GQDs for specific applications are published but a thorough review article on GQDs for their numerous uses has not yet been published. The recent trends of scientific research based on new optical biosensing applications, including the comprehensive applications of different zero-dimensional nanomaterials, specially GQDs are discussed in this study.

CH4 and CO2 conversion over boron nitride-supported Ni catalysts with B[sbnd]O defects in DBD plasma

Non-thermal plasma (NTP) combined with catalysts supplies a potential alternative to enable the CH4 and CO2 conversion to work at low temperatures. In this study, different Ni/BN catalysts were synthesized using modified wetness impregnation for CH4 and CO2 conversion in dielectric barrier discharge (DBD) plasma. Among, BN_IPA_Ni exhibited the highest catalytic performance with a CH4 conversion of 40.5%, a CO2 conversion of 26.6%, a H2 yield of 9.3% and a CO yield of 10.5%. The development of BO defects, which played a significant role in the size control of Ni particles to facilitate the dissociation of CH4 to form H*, is the key for the high catalysis activity and selectivity in this reaction. In addition, the BO defects of BN_IPA_Ni provide an efficient route to eliminate excess CHx species, which further inhibit the nucleation growth of carbon species to inert carbon.

In situ observation of the on-surface thermal dehydrogenation of n-octane on Pt(111).

The catalytic dehydrogenation of alkanes constitutes a key step for the industrial conversion of these inert sp3-bonded carbon chains into other valuable unsaturated chemicals. To this end, platinum-based materials are among the most widely used catalysts. In this work, we characterize the thermal dehydrogenation of n-octane (n-C8H18) on Pt(111) under ultra-high vacuum using synchrotron-radiation X-ray photoelectron spectroscopy, temperature-programmed desorption and scanning tunneling microscopy, combined with ab initio calculations. At low activation temperatures, two different dehydrogenation stages are observed. At 330 K, n-C8H18 effectively undergoes a 100% regioselective single C-H bond cleavage at one methyl end. At 600 K, the chemisorbed molecules undergo a double dehydrogenation, yielding double bonds in their carbon skeletons. Diffusion of the dehydrogenated species leads to the formation of carbon molecular clusters, which represents the first step towards poisoning of the catalyst. Our results reveal the chemical mechanisms behind the first stages of alkane dehydrogenation on a platinum model surface at the atomic scale, paving the way for designing more efficient dehydrogenation catalysts.

In-situ activator-induced evolution of morphology on carbon materials for supercapacitors.

Carbonaceous materials with diverse morphologies have shown unique and excellent performance in many fields, such as catalysis, adsorption, separation and energy storage. However, regulating the structural changes of these morphologies accurately using simple approaches is a difficult process. In this study, porous carbon materials with a morphology that changed from carbon spindles to fold-carbon spheres and then to regular carbon spheres were prepared assisted by in-situ activator of KNO3 in co-assembly of resorcinol/phenol resin and 1-alkyl-3-methylimidazolium bromide. The activation of KNO3 greatly improves the hydrophily, pore volume and surface area of the inert carbon skeleton, and increases heteroatom defects for the carbon framework. As electrode materials of supercapacitors, the influence of different structures on energy storage performance was studied. The obtained fold-carbon spheres showed a higher capacitance (405 F g-1) than flake, spindle and spherical porous carbon, which is due to convenient electrolyte transmission and completely available active sites.

High power zinc iodine redox flow battery with iron-functionalized carbon electrodes.

The zinc iodine (ZI) redox flow battery (RFB) has emerged as a promising candidate for grid-scale electrical energy storage owing to its high energy density, low cost and environmental friendliness. In this work, ZI RFBs were made with electrodes comprising carbon nanotubes (CNT) with redox-active iron particles, yielding higher discharge voltages, power densities, and 90% lower charge transfer resistances compared to cells with inert carbon electrodes. Analysis of the polarization curves reveals that cells with iron-containing electrodes have lower mass transfer resistances and 100% increase in power density (44 mW cm-2 to 90 mW cm-2) at 110 mA cm-2 relative to cells with inert carbon electrodes.

Sustainable Preparation of Graphene Quantum Dots for Metal Ion Sensing Application

Over the past several years, graphene quantum dots (GQDs) have been extensively studied in water treatment and sensing applications because of their exceptional structure-related properties, intrinsic inert carbon property, eco-friendly nature, etc. This work reported on the preparation of GQDs from the ethanolic extracts of eucalyptus tree leaves by a hydrothermal treatment technique. Different heat treatment times and temperatures were used during the hydrothermal treatment technique. The optical, morphological, and compositional analyses of the green-synthesized GQDs were carried out. It can be noted that the product yield of GQDs showed the maximum yield at a reaction temperature of 300 °C. Further, it was noted that at a treatment period of 480 min, the greatest product yield of about 44.34% was attained. The quantum yields of prepared GQDs obtained after 480 min of treatment at 300 °C (named as GQD/300) were noted to be 0.069. Moreover, the D/G ratio of GQD/300 was noted to be 0.532 and this suggested that the GQD/300 developed has a nano-crystalline graphite structure. The TEM images demonstrated the development of GQD/300 with sizes between 2.0 to 5.0 nm. Furthermore, it was noted that the GQD/300 can detect Fe3+ in a very selective manner, and hence the developed GQD/300 was successfully used for the metal ion sensing application.

Centennial records of Polycyclic aromatic hydrocarbons and black carbon in Altay Mountains peatlands, Xinjiang, China

Black carbon (BC) is an important inert carbon component in the cycling process of surface carbon. Polycyclic aromatic hydrocarbons (PAHs) are a kind of thick cyclic organic compounds with carcinogenic, teratogenic, and mutagenic effects. The incomplete burning process of biomass and carbolic fuel is the important source of their co-occurrence. This study collected a 60-cm peat core from the Jiadengyu (JDY), Altay Mountain. The core was dated using the 210Pb and 137Cs methods. The results showed BC, total organic carbon, and PAHs of the JDY peat core to be 1.14–72.6 mg g−1, 17.09–47.2%, and 260.58–1,610.77 ng·g−1, respectively. δ13CBC was between −31.5 and − 29.4‰ (mean of −30.56‰). The results of scanning electron microscopy (SEM) indicated irregular or lumpy peat BC particles, retaining a plant fiber structure. δ13CBC, ratios of PAHs, and the SEM revealed that the BC to be the dominant source of biomass combustion in the peatland. BC showed an increasing trend between 1950 and 1980, after which it decreased. The discrepancy between the change in BC and δ13CBC from the national pattern of BC emission likely reflects the effect of local agricultural exploration, and thus an increase in crop burning.

Impairment of Endothelial Function by Cigarette Smoke Is Not Caused by a Specific Smoke Constituent, but by Vagal Input From the Airway.

Exposure to tobacco or marijuana smoke, or e-cigarette aerosols, causes vascular endothelial dysfunction in humans and rats. We aimed to determine what constituent, or class of constituents, of smoke is responsible for endothelial functional impairment. We investigated several smoke constituents that we hypothesized to mediate this effect by exposing rats and measuring arterial flow-mediated dilation (FMD) pre- and post-exposure. We measured FMD before and after inhalation of sidestream smoke from research cigarettes containing normal and reduced nicotine level with and without menthol, as well as 2 of the main aldehyde gases found in both smoke and e-cigarette aerosol (acrolein and acetaldehyde), and inert carbon nanoparticles. FMD was reduced by all 4 kinds of research cigarettes, with extent of reduction ranging from 20% to 46% depending on the cigarette type. While nicotine was not required for the impairment, higher nicotine levels in smoke were associated with a greater percent reduction of FMD (41.1±4.5% reduction versus 19.2±9.5%; P=0.047). Lower menthol levels were also associated with a greater percent reduction of FMD (18.5±9.8% versus 40.5±4.8%; P=0.048). Inhalation of acrolein or acetaldehyde gases at smoke-relevant concentrations impaired FMD by roughly 50% (P=0.001). However, inhalation of inert carbon nanoparticles at smoke-relevant concentrations with no gas phase also impaired FMD by a comparable amount (P<0.001). Bilateral cervical vagotomy blocked the impairment of FMD by tobacco smoke. There is no single constituent or class of constituents responsible for acute impairment of endothelial function by smoke; rather, we propose that acute endothelial dysfunction by disparate inhaled products is caused by vagus nerve signaling initiated by airway irritation.

Valorization of agrowaste digestate via addition of wood ash, acidification, and nitrification

The valorization of low pollutant bioenergy waste streams as fertilizers is key for a more circular economy. In addition to supplementing nutrients, the wood fly ash could be used as stabilizing agent of an agrowaste digestate, to minimize the pollution of the environment. A two-stage experimental design with series of mild and severe acidifications was used to assess the impact on the availability of nitrogen, carbon, and phosphorus in the 25.26 ± 2.78 g of treated digestate. The 144-hour incubations at 20 °C and 100 rpm were done in closed chambers (i.e. 250-mL Schott Duran® bottles) with a 0.11 M sulfuric acid trap of 4.43 ± 0.12 mL. The proposed model for the interpretation of the results of the closed chamber indicated that the greatest rate of formation of ammoniacal nitrogen in the sulfuric fraction occurred during the first 48 h of incubation of the untreated PVWD (zero order kinetics: 2.31 ⋅ 10 −11 mol [H 2 SO 4 ] NH 4 + N/s). During this period, the mass transfer coefficient was 1.81 ⋅ 10 − 7 m/s , after which the equilibrium was established at 58.47 ± 20.50 mg [H 2 SO 4 ] NH 4 + N/kg digestate. Up to 14.08 ± 3.52 % of the water-soluble nitrogen was converted to nitric nitrogen in the remaining 96 h of incubation of the control. The acidification kept all the nitrogen in the form of ammonium but increased 5.97 ± 0.19 times the leachability of phosphorus. The combined treatment with wood ash and hydrochloric acid prevented both the nitrification and the increase of the share of water-soluble orthophosphate in the digestate. The high share of inert carbon in the wood fly ash was found promising to restore the soil as a natural carbon sink, upon application of the treated anaerobic digestate. Routes for the activation of ash as sorbent that would require lower doses of acid need to be investigated. • The greatest volatilization of ammonia was found in the untreated control digestate. • Closed chamber model was based on kinetic constant and mass transfer coefficient. • Regarding C and P, wood ash offered the greatest impact on the anaerobic digestate. • Wood ash acidification maintained ammoniacal nitrogen and low nutrient availability. • The addition of wood ash increased the N, C and P contents of the anaerobic digestate.