Pyrolysis Of Sewage Sludge Research Articles

Independent parallel pyrolysis kinetics of model components in sewage sludge analyzed by BPM neural network.

Analyzing the kinetic behavior of sewage sludge pyrolysis is essential for the design of efficient reactors to produce biofuel and syngas. To understand the complex pyrolysis process of sewage sludge, we pyrolyzed six model components (i.e., cellulose, hemicellulose, lignin, protein, soluble sugars, and lipid) using a thermogravimetric analyzer. The effects of the heating rate on the pyrolysis process were examined at four different heating rates (5, 15, 25, and 50 °C/min). As temperature increased, the derivative thermogravimetric peaks shifted to higher temperature zones. The temperature ranges of the maximum mass loss rate for cellulose, hemicellulose, lignin, protein, soluble sugars, and lipid were within 326.1-368.0 °C, 288.7-315.5 °C, 375.1-429.4 °C, 291.9-308.0 °C, 251.0-314.1 °C, and 410.8-454.1 °C, respectively. The apparent activation energies of the model components were obtained using non-isothermal kinetic analysis methods (Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose). In addition, a back-propagation artificial neural network with a momentum algorithm (BPM) was developed to predict the relationship between the pyrolysis experiment and the activation value. The best BPM model (BPM5) for predicting the cellulose pyrolysis was identified.

Pyrolytic mechanisms of typical organic components of sewage sludge in the presence of CaO: Polysaccharides, proteins, and lipids

The addition of CaO could facilitate the conversion of sewage sludge (SS) from waste to high-purity syngas. The pyrolytic characteristics of SS are a comprehensive manifestation of polysaccharides, proteins, and lipids, while the influence of CaO on their pyrolytic characteristics is rarely reported. This study conducted a thorough investigation into the pyrolytic mechanism of starch, protein, and lipid in the presence of CaO by analysing their thermal behavior, gaseous products, liquid tar, and residual char. The findings from TGA, GC, GC–MS, and FT-IR analysis indicate that the addition of CaO catalytically lowers the pyrolysis temperature of starch, protein, and lipid components and promotes their conversion into small molecules, resulting in increased syngas production. Moreover, the combination of char with the carbonation and calcination cycle of CaO leads to a significant boost in syngas (H2 and CO) yield, with up to 3 and 10 times increase from starch and protein, respectively, and a higher syngas selectivity of up to 65 %. The study also identifies those polysaccharides and proteins are the primary sources of syngas. This study can provide further insight into SS pyrolysis for syngas production in the presence of CaO and the necessary parameters to predict the pyrolysis behavior of SS in industrial applications.

Nitrogen fixation of municipal sewage sludge by co-pyrolysis with biomass and KH2PO4-modified biochar addition

In order to reduce nitrogen emissions during municipal sewage sludge (MSS) pyrolysis, the effects of co-pyrolysis of MSS with biomass and the second adsorption of KH2PO4-modified biochar were investigated. It was found that co-pyrolysis with cellulose inhibited the conversion of nitrogen into pyrolytic gas, and increased the N content in pyrolytic biochar. And the nitrogen fixation rate increased with cellulose addition increasing. Besides, compared with different biomass, MSS co-pyrolysis with 30% sugarcane bagasse had the optimal effect on nitrogen fixation (39%). Moreover, KH2PO4-modified biochar addition increased the second adsorption of nitrogenous volatiles and fixed nitrogen into oxides-N. The total nitrogen fixation rate reached maximum (47.65%) at 5% KH2PO4 impregnation. Thus, it is an effective nitrogen fixation method that MSS co-pyrolysis of 30% sugarcane bagasse with the second absorption of 5% KH2PO4-modified biochar. This study provided an effective solution to improve the treatment of municipal sewage sludge by pyrolysis technology.

WITHDRAWN: Impact of temperature and residence time on sewage sludge pyrolysis for combined carbon sequestration and energy production

WITHDRAWN: Impact of temperature and residence time on sewage sludge pyrolysis for combined carbon sequestration and energy production

Pyrolysis of sewage sludge to biochar: Transformation mechanism of phosphorus

Biochar produced by pyrolysis of sewage sludge (SS) is considered as a great resource for P recycling. However, the unclear transformation mechanism of phosphorus species during pyrolysis limits the further application of biochar. The study systematically investigated the effects of pyrolysis temperature (300 − 500 ℃) and additives (CaO and MgO) on P speciation in SS and its derived biochar, proposed the transformation pathways of P and clarified its transformation mechanism. The results indicated that the ester bonds in orthophosphate diesters were broken before 400 ℃ to form orthophosphate monoesters and pyrophosphate. Various P forms in SS were gradually converted to Ca10(PO4)6(OH)2, Ca9Al(PO4)7, and Ca3(PO4)2. The addition of CaO further promoted the formation of Ca−P, and the maximum of Ca−P was 2.5 times than that of pyrolysis alone. Phosphorus mainly existed in the forms of Ca3(PO4)2. The promoting effect of MgO on the formation of apatite phosphorus (AP) was not as obvious as CaO. The study provides more theoretical support for the feasibility of SS-pyrolysis biochar for agricultural applications.

Targeting phosphorus transformation to hydroxyapatite through sewage sludge pyrolysis boosted by quicklime toward phosphorus fertilizer alternative with toxic metals compromised

Advancing pyrolysis practice for phosphorus (P) recovery and recycling from sewage sludge arouses intensive research interests due to the forthcoming threat of global P sustainability. However, how to both in situ manipulate P targeted transformation to a designed form and accommodate downstream use while compromise adverse impacts of concomitant toxic metals (TMs) challenges the worldwide initiative of P reclamation from sewage sludge. Here, a P targeted transformation to hydroxyapatite (P2tHAP) technique to bridge the discrepancy of P recovery and subsequent use was developed. Through manipulating calcium-to-P molar ratio (Ca/P) of sludge feedstock by calcium oxide, the sludge P can be targetedly transformed to HAP during pyrolysis, a bioavailable form delivered as sewage sludge char-derived phosphorus fertilizer (SCPF). The P supply competency of the SCPF for Ca/P below or above 1.67 with a risk abatement of TMs was comparable to conventional P fertilizer, while the Ca/P = 1.67 was prone to the occurrence of sludge ash sintering, detrimental to the HAP formation. The lowered bioavailability of TMs was orchestrated by the root-secreted oxalic acid, due to the triggered phosphate starvation response. The random forest analysis indicated the driving force in the evolution of rhizobacterial communities, dominantly arising from those TMs after the SCPF soil application. Thermodynamic and kinetic calculations validated that HAP with the stable molar Gibbs energy gHAP (∼−7.23×103kJ/mol) underpinned the progress of P2tHAP during sludge pyrolysis. The outcome prospects to propel the integrative design of an innovative reclamation of P-rich wastes and simultaneous compromise of concomitant contaminants.

Municipal sewage sludge product recirculation catalytic pyrolysis mechanism from a kinetic perspective

Using biochar derived from municipal sewage sludge (MSS) pyrolysis as a catalytic pyrolysis catalyst can not only achieve product recycling but also enhance conversion rate. In this study, the kinetics of MSS product recirculation catalytic pyrolysis were investigated based on non-isothermal thermogravimetric experiments. The results demonstrate that MSS noncatalytic/catalytic pyrolysis reaction involves five stages, with the main decomposition occurring between 180 and 680 °C and accounting for 53.14%–69.75% of the total mass loss. 20%-cata and 30%-cata reduced the average activation energy by 24.14% and 44.73% for the noncatalytic pyrolysis of MSS, respectively, and the catalytic effect of sludge-based biochar (S–C) allowed the appearance of the lowest activation energy earlier. MSS noncatalytic pyrolysis follows a kinetic mechanism of random nucleation and nucleation growth, whereas exponential nucleation predominate in catalytic pyrolysis. The catalysis mainly operates on macromolecular fracture breakdown and tar secondary cracking. Moreover, a plausible catalytic mechanism for MSS product recirculation catalytic pyrolysis was proposed. The results are expected to be useful in the design of efficient pyrolysis systems.

A study of co-pyrolysis of sewage sludge and rice husk for syngas production based on a cyclic catalytic integrated process system

To address the challenges of low yield and low heating value of syngas, high yield of tar via pyrolysis, and to promote the resource utilization of syngas, this study prepared high-quality syngas through the secondary cracking of tar in cyclic catalytic pyrolysis steam based on a novel cyclic catalytic integrated pyrolysis system. In this study, the cyclic catalytic integrated pyrolysis system process parameters were synergistically optimized based on the pyrolysis syngas yield and lower heating value as indicators. The results showed that the optimal mixing ratio of sewage sludge and rice husk was 25:75 w/w. The optimal cycle speed and catalyst dosage was 1050r/min and 2.5g respectively. Compared to the normal pyrolysis system based on sewage sludge pyrolysis, the liquid phase product yield reduced 6 wt%, and the gas product yield increased 27 wt%. Regarding energy recovery, the syngas lower heating value increased 41.55%. The sewage sludge and rice husk have a synergistic effect and the long residence time promotes secondary cracking of the tar via pyrolysis, thus improving the yield and quality of the syngas. This study provides a new idea for the co-pyrolysis of different biomass to produce high quality syngas, and is very important for the preparation of renewable energy from biomass for application in power generation systems.

Effect of co-pyrolysis of sewage sludge with different plastics on the nitrogen, sulfur, and chlorine releasing characteristics and the heavy metals ecological risk of biochar

The high calorific value, low ash content and high volatility of the plastic can compensate for the deficiencies of the single pyrolysis of sewage sludge (SS), and these properties can improve the quality of the pyrolysis product. However, secondary contaminants may be generated during the co-pyrolysis of sludge and plastics. Plastics contain polluting elements that may also enter sludge, so different plastics may affect the release of N, S, and Cl as well as the ecological risk of heavy metals. In this study, polypropylene (PP), polyamide 6 (PA6) and polyvinyl chloride (PVC) were added to sludge to analyze the release of N, S and Cl from sludge pyrolysis products by different plastics. An environmental risk assessment was also conducted to evaluate the various forms of heavy metals. The results showed that PP, PA6, and PVC increased the total mass losses of sludge by 16.88%, 6.82% and 9.46%, respectively, inhibiting the release of NH3, CH3Cl, H2S and SO2 harmful gases from sludge. PP and PA6 increased the calorific value of pyrolysis oil and released more aliphatic hydrocarbons and alcohols. However, PA6 and PVC will increase the release of HCN and HCl, respectively. The presence of plastics enhanced the carbon structure of biochar, with PP and PA6 particularly enriching the pore structure and surface properties of biochar. PA6 and PVC reduced the potential ecological risk of biochar. These results will provide new insights into the co-pyrolysis of sludge and plastics.

Synergistic interactions between sewage sludge, polypropylene, and high-density polyethylene during co-pyrolysis: An investigation based on iso-conversional model-free methods and master plot analysis

Sewage sludge (SS) is a hazardous by-product of wastewater treatment processes that requires careful management for minimal environmental impacts and effective resource recovery. Through thermochemical processes such as pyrolysis, clean energy is recovered from SS in the form of bio-oil, biogas, and biochar. To improve the yield and quality of products, the co-pyrolysis of more than two materials is increasingly gaining interest. Here, the thermal behaviour, kinetics, and synergistic interactions during the co-pyrolysis of SS with polypropylene (PP) and high-density polyethylene (HDPE) were comparatively evaluated with thermogravimetric analysis at different mixing ratios and heat rates. Activation energies and reaction mechanisms were determined through iso-conversional model-free methods and master plot analysis. Evolved gases were monitored with thermogravimetric-mass spectrometry. Increased volatile conversion and degradation rates, and reduced activation energies during co-pyrolysis were mediated by synergistic interactions between H-radicals of PP/HDPE and oxygenated intermediates of SS. Contrary to the pyrolysis of SS, PP and HDPE, the co-pyrolysis processes are predominantly diffusion-controlled. Insights into the co-pyrolysis processes of SS/PP and SS/HDPE gained from this work provide the theoretical support for subsequent investigation, facilitate design of waste-to-energy reactor, and aid the adoption of the technology to harness the bioenergy potential of the feedstocks.

Synergetic process between wind power and sewage sludge pyrolysis in a novel renewable-energy microgrid system

AbstractTo relieve the stress of sewage sludge (SS) disposal and effectively increase the use of renewable energy, a novel renewable-energy microgrid system (REMS) was developed, specifically designed to integrate a wind power plant (WPP) with energy storage and the SS pyrolysis process for heat and power generation. Based on a lab-scale pyrolysis experiment and 7-day numerical analysis, we studied the energy-recycling potential of SS and simulated the operational behaviours of REMS. According to the results, the calorific values of the pyrolytic gaseous and liquid products were better than those of the raw material, at 16.19 and 33.53 MJ/kg, respectively. The proposed REMS performed well in power supply and energy utilization with a design performance index of 99.23 when the WPP capacity was 200 MWe and the initial wind-energy curtailment rate was 30%. It indicates that by converting SS into flammable gas, condensable liquid and carbon-rich solid residue, curtailed wind energy could be saved and the synergy between wind power and the SS pyrolysis process enabled the proposed microgrid system to effectively utilize renewable energy and provide reliable on-demand power service. The REMS installed with a 155-MWe WPP achieved the optimal design in system performance, environmental benefit and construction cost under the initial wind-curtailment rate of 34.12%. The design scheme makes REMS capable of satisfying the 15.10-GWh power demand of end users and the 1700-t/day SS disposal need, and the curtailed wind energy could be reduced to zero.

Thermo-kinetic analysis of pyrolysis of thermally pre-treated sewage sludge from the food industry

Due to the specific characteristics of sewage sludge from the food industry, including its high fat content, its treatment is quite complex. Therefore, in this study, the effect of the pre-treatment processes torrefaction (T) and hydrothermal carbonization (HTC) on the pyrolysis of industrial sewage sludge (SS) from the vegetable oil industry was investigated by thermogravimetric analysis. Kinetic and thermodynamic analysis was performed using the Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Friedman (FRI) iso-conversional kinetic models. In addition, the influence of water replacement by whey in the hydrothermal carbonization process was investigated on the subsequent pyrolysis kinetics.The activation energy (Eα) values for pyrolysis of industrial sewage sludge ranged from 49 to 372 kJ/mol. Pre-treatment (torrefaction, hydrothermal carbonization) of sewage sludge increases the activation energy significantly: the Eα values for torrefied (T-SS) and hydrothermally treated (HTC-SS) samples ranged from 177 to 689 kJ/mol and from 161 to 486 kJ/mol, respectively. The variations in activation energy and the generally lower activation energies for the HTC-SSW sample (158–445 kJ/mol) indicate that the use of whey in the HTC process affects the hydrochar properties and subsequent pyrolysis kinetics significantly. According to the results, the pre-treatment of the samples is reflected in better thermochemical properties and stability of the treated samples, as well as in the thermodynamic parameters of pyrolysis, since the pre-treated samples (especially the torrefied sample, T-SS) exhibited higher entropies and enthalpies and lower Gibbs free energies.

Biochar Prepared by Microwave-Assisted Co-Pyrolysis of Sewage Sludge and Cotton Stalk: A Potential Soil Conditioner

The reduction and safe disposal of sewage sludge remains an urgent problem worldwide. In this work, biochar prepared from co−pyrolysis of sewage sludge and cotton stalk at different mix ratios and different pyrolysis temperatures was prepared using a novel microwave-assisted auger reactor. The obtained biochar samples were mixed with selected soil samples at different mix ratios for a short−term plant−growing test to examine their abilities as a soil conditioner on nitrogen fixation and retention. The addition of biochar could increase the total nitrogen in the soil to 0.3951% compared to 0.0403% in the untreated soil, while the concentration of available nitrogen could be increased to 114.45 mg·kg−1 compared to 47.95 mg·kg−1 in the untreated soil. Moreover, the introduction of biochar to the soil also contributed to the growth of corn seedlings, which grew at a rate of 3.41 cm·d−1 compared to 3.03 cm·d−1 in untreated soil. The results show that the addition of biochar can enrich total soil nitrogen before and after incubation and promote the growth of corn seedlings, providing a potential route for the safe disposal and resource recovery of sewage sludge.

Study on characteristics, hydrogen-rich gas, bio-oil production, and process optimization of co-pyrolysis of sewage sludge and wheat straw

Sewage sludge (SS) and wheat straw (WS) are wastes that need to be treated urgently. In this research, the co-pyrolysis of SS and WS was investigated utilizing a thermogravimetric analyzer (TG) and a fixed bed. Using the Coats-Redfern approach, the effects of the mix ratio and the interactions of the SS and WS were investigated, and the effects of mix ratio, N2 flow rate, and pyrolysis temperature were examined for fixed bed pyrolysis. The response surface method (RSM) was applied in fixed bed pyrolysis to optimize the process. Increasing WS ratio can reduce pyrolysis residual rate to 23.8% for TG analysis. The reaction activation energy (E) increased with WS ratio. For the co-pyrolysis, there were substantial interactions between 200 and 400°. For fixed bed pyrolysis, syngas and bio-oil yields were mainly affected by N2 flow rate and pyrolysis temperature. The components with the highest amount in bio-oil gradually changed from aliphatic to aromatic hydrocarbons as the WS proportion grew, demonstrating that WS pyrolysis produced mostly aromatic compounds whereas SS pyrolysis produced more aliphatic compounds. Temperature 600 °C, sludge mixing ratio 32%, flow rate 2.5L/min, anticipated maximum H2 0.0421 m3/kg, and maximum bio-oil of 50.7114 g/kg are the best circumstances according to RSM.

The decomposition and emission factors of a wide range of PFAS in diverse, contaminated organic waste fractions undergoing dry pyrolysis

Current treatment options for organic waste contaminated with per- and polyfluoroalkyl substances (PFAS) are generally limited to incineration, composting or landfilling, all resulting in emissions. Dry pyrolysis is a promising emerging alternative to these practices, but there is uncertainty related to the fate of PFAS during this process. The present work first developed a robust method for the determination of PFAS in complex matrices, such as sewage sludge and biochar. Then, a mass balance was established for 56 different PFAS during full-scale pyrolysis (2–10 kg biochar hr-1, 500–800 °C) of sewage sludges, food waste reject, garden waste and waste timber. PFAS were found in all wastes (56–3651 ng g-1), but pyrolysis resulted in a ≥ 96.9% removal. Residual PFAS (0.1–3.4 ng g-1) were detected in biochars obtained at temperatures up to 750 °C and were dominated by long chain PFAS. Emitted PFAS loads ranged from 0.01 to 3.1 mg tonne-1 of biochar produced and were dominated by short chain PFAS. Emissions made up < 3% of total PFAS-mass in the wastes. Remaining uncertainties are mainly related to the presence of thermal degradation products in flue gas and condensation oils.

Investigation of Sewage Sludge for Obtaining Organomineral Fertilizer

A technology for obtaining organomineral fertilizer based on sewage sludge from chemical enterprises is proposed, which allows increasing soil fertility due to the fine structure of bio-coal obtained during pyrolysis of sewage sludge, which retains nutrients in soils for a long time. Studies of sewage sludge before and after pyrolysis for compliance with agrochemical indicators of organic fertilizers according to GOST R 54651-2011 "Organic fertilizers based on sewage sludge" are presented. A method for obtaining organomineral fertilizer by mixing activated sludge with phosphorous flour and sawdust is proposed to ensure the stability of indicators according to the required values according to GOST criteria.

Municipal Sewage Sludge as a Source for Obtaining Efficient Biosorbents: Analysis of Pyrolysis Products and Adsorption Tests.

In the 21st century, the development of industry and population growth have significantly increased the amount of sewage sludge produced. It is a by-product of wastewater treatment, which requires appropriate management due to biological and chemical hazards, as well as several legal regulations. The pyrolysis of sewage sludge to biochar can become an effective way to neutralise and use waste. Tests were carried out to determine the effect of pyrolysis conditions, such as time and temperature, on the properties and composition of the products obtained and the sorption capacity of the generated biochar. Fourier transform infrared analysis (FTIR) showed that the main components of the produced gas phase were CO2, CO, CH4 and to a lesser extent volatile organic compounds. In tar, compounds of mainly anthropogenic origin were identified using gas chromatography mass spectrometry (GC-MS). The efficiency of obtaining biochars ranged from 44% to 50%. An increase in the pyrolysis temperature resulted in a decreased amount of biochar produced while improving its physicochemical properties. The biochar obtained at high temperatures showed the good adsorption capacity of Cu2+ (26 mg·g-1) and Zn2+ (21 mg·g-1) cations, which indicates that it can compete with similar sorbents. Adsorption of Cu2+ and Zn2+ proceeded according to the pseudo-second-order kinetic model and the Langmuir isotherm model. The biosorbent obtained from sewage sludge can be successfully used for the separation of metal cations from water and technological wastewater or be the basis for producing modified and mixed carbon sorbents.

Mechanism of gas production under microwave/conventional pyrolysis of sewage sludge: Mechanism of microwave energy action on oxygen-containing functional groups

Microwave pyrolysis (MWP) of sewage sludge (SS) has obvious advantages in the quality improvement of syngas. However, it is unclear the mechanism of syngas production and microwave energy on oxygen-containing functional groups during MWP of SS. In this paper, the effect of pyrolysis methods on syngas generation is investigated through macroscopic experimental quantitative analysis combined with microscopic DFT simulations. Compared with conventional pyrolysis (CP), MWP showed higher gas yields. Further quantitative analysis of the gas composition revealed that microwaves excited the gasification reaction of CO2 and promoted the production of H2 and CO, and increased by 39.89%. Kinetic calculations revealed that microwaves decreased the activation energy of H2 and CO by 50.84% and 29.59%, respectively. Tar analysis revealed that microwaves promoted a large number of oxygen-containing functional groups transferred to tar at low temperatures. As temperature increases, the oxygen-containing functional groups in the tar undergo a secondary reaction in response to microwave, resulting in numerous H radicals and O radicals being transferred to the gas phase, promoting the yield of H2 and CO. Combined with DFT to explore the decomposition path of all typical oxygen-containing functional groups in tar, it found that the decomposition of these functional groups into H2 and CO requires high energy to complete, and microwave was expected to achieve the process. Finally, the mechanism of microwave energy in the process of SS pyrolysis was proposed, which provides a feasible idea for the subsequent directional regulation of microwave pyrolysis of SS.

Effect of Potassium Ferrate as a Dewatering Conditioner on Sludge Pyrolysis Characteristics and the Releasing Characteristics of Nitrogen, Sulfur, and Chlorine during Sewage Sludge Pyrolysis

Sludge pyrolysis is a promising method for treating excess sludge as a by-product of municipal sewage plants, allowing for energy self-sufficiency and resource recovery. Before sludge pyrolysis begins, a few conditioning agents are added to the sludge that promote sludge dewatering. Potassium ferrate (K2FeO4) is applied as a conditioning agent with both cracking and flocculation effects, but the effects of K2FeO4 on the release characteristics of nitrogen, sulfur, and chlorine during sludge pyrolysis have not been elucidated. In this study, we analyzed the sludge pyrolysis characteristics and chemical state changes of N, S, and Cl contaminants in the dewatered sludge after K2FeO4 conditioning before and after pyrolysis. Further, the release characteristics of condensable/noncondensable gases during pyrolysis were assessed using thermogravimetric mass spectrometry (TG-MS) and pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) analyses before and after conditioning. We found that potassium pertechnetate reduced the activation energy required for the sludge in the pyrolysis process. Noticeably this process made the sludge more susceptible to thermal decomposition leading to volatile production and also influenced the release of different contaminants generated by the pyrolysis process. Moreover, K2FeO4 promoted the release of C/H/O gases and reduced the release of N/S/Cl pollutant gases from the sludge. Overall, this study provides a theoretical basis for the selection of conditioning agents for the sludge conditioning and dewatering steps during the sludge pyrolysis process.

Opportunities of Integrating Slow Pyrolysis and Chemical Leaching for Extraction of Critical Raw Materials from Sewage Sludge

Slow pyrolysis is a promising technology to convert sewage sludge into char: a stable solid product with high carbon and phosphorus content. However, due to its heavy metals content, char use in agriculture is avoided in many European Union (EU) countries. This study aimed to test a solution, based on integrating slow pyrolysis and chemical leaching, to separate phosphorus and other inorganics from char, obtaining an inorganic P-rich fertiliser and a C-rich solid usable for industrial purposes. The sludge was first characterized and then processed in a 3 kg/h slow pyrolysis reactor at 450 °C for 30 min. The resulting char was processed by chemical leaching with acid (HCl, HNO3) and alkali (KOH) reagents to extract inorganic compounds. To optimize the inorganic extraction, three case studies have been considered. The char obtained from sewage sludge pyrolysis contained around 78% d.b. (dry basis) of inorganics, 14% d.b. of C, 14% d.b. of Al, and almost 5% d.b. of P. The leaching tests enabled to extract 100% of P, Mg, and Ca from the char. The remaining char contained mainly carbon (27%) and silica (42%), with a surface area of up to 70 m2/g, usable as adsorbent or precursor of sustainable materials.