Reduction In Ash Content Research Articles

Acid demineralization effect on the sonication-assisted solvent extraction of vitrinite coal of the Powder River Basin

Solvent-extraction of economic low-grade coals has gained recent interest as a way to produce new feedstocks for the synthesis of advanced carbon materials including polymers. Herein, we report the effect of coal demineralization by hydrochloric acid treatment on the sonication-assisted extraction of subbituminous coal from the Powder River Basin in Wyoming, USA at room temperature and the analysis of the initial and residual coals by FT-IR and solid-state 13C NMR. The applied demineralization reduced ash content from 9.9% to 7% without any notable change in the coal composition or structure. Despite leaving the mineral matter in the coal, the demineralization significantly increased the extraction yield for all applied solvents, for ethylenediamine from 8.1% to 15.2%, for pyridine from 4.9% to 12.4%, and acetone from 1.1% to 4.5%.

Agro-residues for clean electricity: A thermo-property characterization of cocoa and kolanut waste blends

Huge quantities of harvest wastes that are generated from agricultural practices at every farming season in Nigeria are not put into significant use. As an attempt towards adopting these abundant by-products as bioenergy resources for electricity generation, yearly quantities of both cocoa and kolanut harvest residues were estimated in this study. Hygroscopic natures and moisture contents of the two, and their blends, were also analyzed and compared. It was estimated that approximately 681,000 tons and 90,000 tons of cocoa and kolanut husks respectively, are produced in the country annually. While the proximate analyses showed that the sample made of 100% cocoa waste had the least volatile matter and moisture contents in addition to having highest fixed ash and fixed carbon contents, the reverse was the case with the sample made of 100% kolanut waste composition. From the ultimate analyses, however, the latter appears to possess the best characteristic (highest hydrogen and least oxygen contents), but its highest nitrogen content is a pointer to its exhibition of poor thermal property. The gross calorific contents of the samples were, therefore employed for definitive determination of their thermoelectric potentials and these gave higher heating values of 15.19 MJ/kg and 13.87 MJ/kg respectively, with the blends having their values within this range in proportionality to the mass percentage of kolanut husk in the blends. In addition to the two wastes exhibiting good energy characteristics, the study concludes that their blending offers benefit of reduction in ash content. At the optimal blend of equal composition of the two materials (50%CPH/50%KPH), it was estimated that 29,000 MW of electricity is accruable from the wastes.

Application of response surface methodology for optimization of wheat flour milling process

AbstractBackground and objectivesFlour millers are faced with constraints of having to meet proximate specifications, usually defined by supply contracts, while trying to maximize yield. The study investigated the application of response surface methodology (RSM), in a commercial scale flour mill, as a means of maximizing yield while meeting quality constraints.FindingsThis study utilized a Box–Behnken design to develop mathematical models using RSM to describe the effect of three independent variables, wheat conditioning level (12%–18%), first break roll gap (350–600 µm), and second break roll gap (200–600 µm) on the responses. The model R2 for the responses was .98, .96, .98, and .98 for ash, protein and moisture contents, and flour yield, respectively. All models were statistically significant (p < .05) and validated with four independent experiments. RSM models were used to optimize the process to produce flour with a protein content greater than 12.0%, ash content less than 0.54%, moisture content less than 14.5%, and yield greater than 84.2% on a clean wheat, unconditioned basis. This was achieved with conditioning wheat to 18.4%, first break roll gap of 450 µm, and second break roll gap of 250 µm.ConclusionThe optimum mill settings resulted in a flour yield increase of 1.45% and reduction in ash content from 0.58% to 0.53%.Significance and noveltyUsing RSM, significant financial gains could be achieved by producing more flour from a given quantity of wheat with lower levels of bran contamination.

Effect of germination on nutritional and bioactive properties of red rice grains and its application in cupcake production

Rice flour is a promising ingredient for the development of gluten-free products due to its natural characteristics such as hypoallergenic nature, mild flavor, gel stability while freezing or thawing, and resistance to acidic ingredients. The aim of this study was to evaluate the effect of germination time on nutritional and bioactive properties of red rice and its application in the production of cupcakes. Red rice grains that were germinated for 8, 16, 24, 32, and 40 h, were evaluated along with a sample of non-germinated grains. The increase in germination time promoted a reduction in ash content, moisture, and pH, without changes in the other constituents of the basic composition. Regarding the content of phenolic acids and individual flavonoids in the free fraction, there was an increase in caffeic, coumaric, and ferulic acids, and myricetin after 16 h of germination. The content of GABA (gamma-aminobutyric acid) in the flour also increased over time, reaching 1.86 mg 100/g in 40 h, which further increased to 3.66 mg 100/g after baking the cupcakes. Concurrently, the cupcake acceptability index of 89.65% indicated that the product was accepted sensorially by the consumer. The germination of red rice results in the release of/increase in the content of some compounds, which makes it a suitable alternative for application in food products.

Variability of Normative Properties of Wood Chips and Implications to Quality Control

The research was conducted with the goal to determine the variability of the quality parameters of the wood chips produced from the most favorable raw material (energy roundwood), and in the most controllable operational conditions (pellet factory), as the first step in identifying opportunities to optimize the wood chips’ quality monitoring. Four raw material types were tested: fir/spruce and beech debarked energy roundwood, as well as energy wood with bark of the same species. Sampling was conducted during six consecutive months along with laboratory testing, all according to the HRN EN ISO standards for solid biofuels. Interpretation of the results was done in relation to deviation from the first sampling results (as an indicator of the possibility to retain the quality of wood chips), and repeatability and reproducibility set in the standards (as an indicator of acceptable variability). The influence of the species and debarking process on the wood chips’ quality was analyzed as well. Relative deviation from the first sampling as well as the quality class change pointed moisture content as a normative property with the lowest possibility to retain initial values over the six-month period. Ash content results indicated a strong possibility to maintain the initial ash content class in the majority of the samples. In just three cases, the results of ash content were outside the reproducibility limits with first sampling as a reference. Gross calorific value results pointed only four samples outside the reproducibility limits with the first sampling results are set as a reference. Wood species influenced gross calorific value and the median value of the particle size distribution and debarking showed a significant positive effect on the moisture content reduction as well as on the ash content reduction. Presented findings are indicative for the investigated raw materials, however for the general conclusion on the subject of wood chips normative properties variation, various raw material types will have to be examined in further research.

Investigation of the cleanability of asphaltite by flotation

Southeastern Anatolia Region of Turkey/Sirnak asphaltites centers are located in and around large reserves in coal mines. Due to the high ash and sulfur content of asphaltite coal, it is important to use it by cleaning with enrichment methods, in terms of solving environmental problems and increasing energy quality. In this study; the main characteristics (chemical analysis, ICP-OES, XRD, SEM analysis) of the asphaltite samples taken from the Avgamasya quarry operating in the center of Sirnak province were determined after the crushing and grinding processes. Later, the asphaltite coal sample was subjected to the flotation enrichment method, which is widely used in fine particle size coal enrichment methods. In the flotation method, the effects of kerosene, fuel oil, and aerophine3418A reagents in different amounts were investigated. Accordingly, the best ash results in the A1(50 g/t kerosene + 0.1 g/t MIBC) experiment; were obtained by adding 50 g/t kerosene reagent and the ash content was determined as 30.80% with an ash content reduction from 46.08% to 33.16%. Best result for reducing the sulfur ratio; in the B2(100 g/t fuel oil + 0.1 g/t MIBC) experiment, it was determined by the addition of 100 g/t fuel oil reagent. Here, the total sulfur content was reduced from 6.46% to 5.71% with a sulfur content reduction of 11.61%.

Preparation of raw materials, creation of compositions and granulation from obsolete sludge, peat and biomass

The article presents research on the preparation of raw materials, creation and granulation of compositions from obsolete sludge deposits of peat and biomass. Studies of raw material preparation processes have shown that obsolete sludge deposits have excessive ash content. To reduce ash content, it is advisable to add peat and biomass to sludge. During the study of peat, it was determined that peat extracted from the floodplain of Irpen has a high ash content, so for further research used peat from Chernihiv.
 The created compositions were subjected to granulation in different compositions and ratios. Preliminary dehydration of peat in the drying cabinet and moistening of the sludge were performed to create different sludge-peat mixtures with different moisture content of sludge and peat. When creating two-component compositions to sludge-peat add biomass. Studies have allowed us to choose the optimal ratio for granulation.

A comprehensive study on upgradation of pyrolysis products through co-feeding of waste tire into rice straw under broad range of co-feed ratios in a bench-scale fixed bed reactor

A comprehensive study investigating all co-pyrolysis products (bio-oil, char, and gas) utilizing bench-scale reactor is essential for potential use in upscaling and techno-economic analysis for commercialization and integration of pyrolysis with conventional systems. This study explores the co-pyrolysis of rice straw (RS) and waste tire (WT) to assess the impact on products under a broad range of feedstock ratio (20, 40, 60, and 80 wt% of WT into RS) in fixed bed reactor at 550 °C. Results revealed that feedstock mass ratio played a crucial role to transform the oxygenates into hydrocarbons (HCs). Liquid yield, organic phase, pH, aromatics, and olefins increased with increase of WT proportion in blend. Bio-oil yield, aromatics and olefins reached to 45 wt%, 42%, and 30% at WT/RS (80:20) compared to 36 wt%, 2%, and 4% in the case of RS alone, respectively. Likewise, at the same blend ratio, 85% reduction in oxygenates was observed while higher heating value (HHV) of bio-oil (41.40 MJ/kg) was comparable to that of WT (41.50 MJ/kg). Significant positive synergy was achieved for non-condensable gas after incorporation of WT into RS. Hydrogen (H2) and methane (CH4) along with higher HCs were increased while oxides of carbon reduced with the addition of WT compared to RS alone. Char characteristics also improved with addition of WT into RS in terms of increased carbon content, HHV, and reduced ash content.

Making blends of agarwood waste with empty palm bunches or rubber wood sawdust for pelletized biofuels

This study created biomass-pellet fuel with reduced ash content from agarwood waste mixed with empty palm bunches (ACW+EPB), and from agarwood waste with rubber wood sawdust (ACW+RWS), utilizing the low ash value of the agarwood waste. The tested blends had a 1:1 ratio of agarwood waste and empty palm bunches, and a 1:3 ratio of agarwood waste and rubber wood sawdust. Comparisons were also conducted relative to Korean (Grade 4) (2014) and ENplus B (2014) commercial pellet standards. Before pressure molding, the mixture components were dried and ground in a pelletizing device with a motor power of 7.5 kW (380 V, 50 Hz), yielding 100 to 150 kg/h without added adhesive. The test results showed that ACW ash content decreased in the RWS hybrid, yet increased in the EPB mixture. The attributes of ash content, moisture content, and heating value of ACW+RWS satisfied ENplus B (2014) and Korean (Grade 4) (2014) standards at 1.70%, 4.50%, and 4,536 kcal/kg. The ACW+EPB also satisfied the Korean (Grade 4) standard at 4.20%, 6.50%, and 4,220 kcal/kg. Thus, the biomass pellets from the mixture of agarwood waste and rubber wood sawdust and that of agarwood waste and empty palm bunches were of suitable quality for commercial purposes.

Effects of acid treatment on physicochemical properties and gasification reactivity of fine slag from Texaco gasifier

Fine slag (FS), which is a by-product from coal gasification, is composed of inorganic minerals and residual carbon. Acid treatment has high efficiency to separate the residual carbon in FS but the changes of properties of FS treated by acid remain unclear. To have a deep understanding of effects of acid treatment on physicochemical properties and gasification activity of FS, FS was subjected to different acid treatment, and then were characterized using Nitrogen adsorption technique, Raman spectroscopy and thermo-gravimetric analyzer. The results showed that the combined treatment with hydrochloric acid and hydrofluoric acid can remove the almost all mineral matters. Acid treatments did not modify the continuous and complete pores structure of FS. While, hydrochloric acid has a major influence on carbon structure, which produces the highest carbon actives and amorphous carbon. Nitric acid has positive influence on carbon structure transformation to crystalline structure. Notably, the gasification time can be shortened by the reduction of ash content. The carbon active sites in samples governed the initial reactivity while at the late stage of gasification the amount of inorganic elements controlled the gasification rate.

Application of attached algae flow-ways for coupling biomass production with the utilization of dilute non-point source nutrients in the Upper Laguna Madre, TX

The purpose of this study is to determine the potential for an attached algae flow-way system to efficiently produce algal biomass in estuarine surface waters by utilizing dilute non-point source nutrients from local urban, industrial, and agricultural discharges into the Upper Laguna Madre, Corpus Christi, Texas. The study was conducted over the course of two years to establish seasonal base-line biomass productivity and composition for bioproducts applications, and to identify key environmental factors and flow-way cohorts impacting biomass production. For the entire cultivation period, continuous ash-free biomass production at 4 to 10 g/m2/day (corresponding to nutrient recovery at 300 to 500 mg of nitrogen/m2/day and 15 to 30 mg of phosphorus/m2/day) was successfully achieved without system restart. Upon start-up, a latency period was observed which indicates roles for species succession from relatively low productivity, high ash content pioneer periphytic culture composed primarily of benthic diatoms from the source waters to higher productivity, reduced ash content, and more resilient culture mainly composed of filamentous chlorophyta, Ulva lactuca. Principal Component Analysis (PCA) was used to identify environmental factors driving biomass production, and machine learning (ML) models were constructed to assess the predictive capability of the data set for system performance using the local multi-season environmental variations. Environmental datasets were segregated for ML training, validation, and testing using three methods: regression tree, ensemble regression, and Gaussian process regression (GPR). The predicted ash-free biomass productivity using ML models resulted in root-squared-mean-errors (RSME) from 1.78 to 1.86 g/m2/day, and R2 values from 0.67 to 0.75 using different methods. The greatest contributor to net productivity was total solar irradiation, followed by air temperature, salinity, and pH. The results of the study should be useful as a decision-making tool to application of attached algae flow-ways for biomass production while preventing algal blooms in the environment.

Automation of the control process by the shearer drum in terms of coal seam hypsometry

Purpose. To develop a method for synthesizing a fuzzy automatic control system for a shearer drum in terms of coal seam hypsometry basing on the information criterion of the beginning of rock cutting-off by the drum to reduce ash content of the extracted coal. Methodology. Taking into consideration peculiarities of determining a distinct information criterion of the beginning of rock cutting-off by the drum and regularities of its variations during the shearer operation, a fuzzy inference algorithm is developed for a system of fuzzy automatic drum control in terms of seam hypsometry. In this context, rules of fuzzy productions, parameters of the membership functions of terms of the output linguistic variable system, and fuzzy operations are substantiated according to the recommendations of a classic Mamdani fuzzy inference algorithm. Studies are carried out to analyze the efficiency of the proposed fuzzy inference algorithm basing on the introduced relative parameter of the number of effective control actions formed by the fuzzy control system. Simulation modeling makes it possible to perform comparative analysis of the efficiency of the drum control. Findings. In the course of research, an algorithm of fuzzy control of the shearers upper drum in terms of coal seam hypsometry has been developed basing on the determination of direct and inverse transfer from coal breaking near the seam roof by the shearer drum to rock breaking with the help of statistical analysis of the stator power of a cutting drive motor. Originality. For the first time, a method of synthesis of fuzzy automatic control of the drum in terms of seam hypsometry has been proposed. Practical value. The proposed method is the theoretical basis to solve important scientific and applied problem of the automation of the coal shearer drum in terms of seam hypsometry to reduce ash content of the produced coal.

Fuel properties and compositional analysis of Areca catechu sawdust over MgO and ZSM-5 catalysts

This work addresses the effect of operating parameters and catalysts on pyrolytic products yield and nature of pyrolytic liquid generated from Areca catechu sawdust (AN). Physicochemical characteristics of AN showcased its bio-energy potential as a substitute for fossil fuels. Further, catalytic pyrolysis yielded 36.75 wt% and 35.70 wt% pyrolytic liquid for ZSM-5 and MgO respectively at 8:1 B/C, which is greater than thermal pyrolytic yield 33.75 wt%. The characterization of pyrolytic oil demonstrated that the adoption of catalysts upgrades the properties of pyrolytic oil. FTIR examination of pyrolytic oil summarized the attendance of aromatics, acid, moisture, protein impurities etc., while GC-MS results recognized that the utilization of catalysts brings down the yield of oxygen-rich products and acids while showing an escalation in the aromatic yield. Further, ash content study of pyrolytic oil confirmed the greater reduction in ash content in catalytic pyrolytic oil than thermal pyrolytic oil due to utilization of catalysts. Results of biochar characterization marked out a higher carbon content (73.14%), heating value (29.11 MJ kg−1), zeta potential (−31.04 mV), fixed carbon (62.12%) and lower BET surface area (5.49 m2 g−1). Furthermore, the XRF study of ash content established the attendance of various inorganic content in ash which worked as catalysts at the time of pyrolysis.

Biofuel, Bioenergy and Feed Valorization of By-Products and Residues from Hevea brasiliensis Cultivation to Enhance Sustainability

In the latex production chain, rubber tree seeds (Hevea brasiliensis) represent an underutilized fraction with high potentialities, which can increase the sustainability of the whole process if rightly valorized. In the present study, the quality of all the fractions obtained from the rubber fruit were evaluated, with the aim to identify possible applications for their valorization with a circular economy perspective. Seeds from five different varieties of rubber tree were analyzed. Furthermore, a whole mass and energy balance was defined, which has allowed us to define hypothetical production scenarios. The obtained results show negligible differences among varieties. Shells and capsules have shown a composition similar to woody biomass, with high heating values (more than 16.5 MJ kg−1), low nitrogen content (below 0.5% on weight basis (w/w)) and reduced ash content (0.51% w/w and 1.90% w/w, respectively). Kernels were chemically extracted comparing two different solvents: n-hexane and ethanol. Both solvents showed similar extraction yields, i.e., 49% w/w and 46% w/w for n-hexane and ethanol, respectively. The resulting extraction flour was characterized by a high protein content (around 40% w/w) making it suitable for animal feeding. The rubber seed oil could be used in blends of different vegetable oils for biodiesel production. All this information is useful for improving the sustainability of the latex production chain and to assess the sustainability of possible bioenergy value chains.

STUDY OF GELATIN FROM DUCK BONE AS AN ALTERNATIVE SOURCES OF HALAL GELATIN

Gelatin is an intermediate ingredient which is oftenly used in many field such as food, pharmacy, and cosmetics. It is usually extracted from pig and cow. Halal issue of gelatin sources and the outbreaks of mad cow diseases encouraged people to find an alternative sources of gelatin. One of the alternative sources of gelatin was duck bone. The aim of this research was to describe physicochemical properties of duck bone gelatin which is extracted by using acid extraction method as an alternative sources of halal gelatin. The extraction of duck bone gelatin used 5% concentration of HCl (hydrochloric acid). The extraction process consisted of four steps, they were degreassing, defating, demineralization, and acid extraction. The result showed that gelatin which was extracted from duck bone had these several characteristic: yield of 6.24%, pH 4.0, water content of 13.43%, ash content of 13.42%, protein content of 65.43%, and whiteness degree of 30.35%. Generally, gelatin which was extracted from duck bone had similar characteristic with commercial gelatin and SNI standard. Further researcher had been suggested to reoptimized extraction method in order to reduce ash content.

Ascophyllum nodosum Application and Pre-Sowing Stimulation with Low-Frequency Magnetic Field as Factors Influencing Oat Grains (Avena sativa L.) Composition

In this study, we tested the influence of two experimental factors on the composition of oat grain Avena sativa under the conditions of a three-year field study. The first factor (factor A) consisted of an Ascophyllum nodosum application, an organism classified in the Chromista kingdom, class Phaeophyceae, order Fucales; the second factor was the pre-sowing stimulation of seeds with a low-frequency magnetic field with known parameters. The basic organic components and mineral composition of the grain were tested. It was determined, among other things, that fertilization with algae leads to reduced ash content in oat grain, increased content of sodium, reduced calcium and iron content, and increased content of starch components (amyloses and amylopectins). The application of pre-sowing seed stimulation resulted in increased copper content in the progeny. No significant interactions could be observed between the factors in forming the chemical composition of oat grain.

Recent developments in reduction of sulphur emissions from selected Waterberg coal samples used in South African power plants

Sulphur content in the coal is the most notorious environmental contaminant, which produces sulphur dioxide (SO2) during combustion. In this study, the sulphur content of the parent coal samples reduced through biodesulphurization treatment and its influence on the SO2 emissions concentration in a power plant was monitored. Coal samples were screened to a particle size fraction of – 0.85 mm, – 2.30 + 1.00 mm, – 4.60 + 2.30 mm and +4.60 mm prior to biodesulphurization treatment. Data used in this study comprised of average 2 daily interval sulphur content and SO2 emissions concentrations for the period 0 to 20 Days. The finer fraction of – 0.85 mm showed a significant reduction of sulphur content from 1.45 wt% to 0.50 wt% which translate to SO2 emissions concentration reduction from 3716 mg/Nm3 to 1280 mg/Nm3. However, when the temperature was increased from 23 ± 3 °C to 30 ± 2 °C, further reduction of SO2 emissions to 1023 mg/Nm3 was realized. Biodesulphurization treatment demonstrated to lower SO2 emissions by 72.4% and reduce ash content by some 33%. Moreover, pyrite was observed in vitrinite and inertinite, both syngenetically and epigenetically. The current study offers the possibility of reducing SO2 emissions in South African power plants through biodesulphurization treatment.

Turpentine oil: a novel and natural bridging liquid for agglomeration of coal fines of high ash coals

ABSTRACT Oil agglomeration is an effective way to demineralize high ash coals as compared to froth flotation and density gradient separation. In this process, the choice of bridging liquid is critical with respect to economics and efficiency. Herein, we report turpentine oil as a potential bridging liquid which is demonstrably efficient in coal demineralization at lower concentration (10 vol.%) compared to literature (20–25 vol.%) without inclusion of surfactants, which enhances economic viability. We chose two high ash coals of Indian origin, with 26% and 34% ash. A varied range of particle sizes were examined along with pH, type of electrolytes, agitation conditions and oil dosages. Both coals (200 mesh) demonstrated approximately 50% reduction in ash content at pH 7, which is an improvement over previously known reports on Indian coals. Chemical structural resemblance between primary components of turpentine oil and predominant π-delocalized aromatic structure of high rank coals could be the reason behind improved adsorption of oil. Our work thus demonstrated the utilization of a natural oil which can be dried easily, readily available and cheap in a significantly demanding commercial process like coal beneficiation. This is expected to deliver a substantial performance and cost improvement over incumbent known bridging liquids.

Briquetting characteristics of woody and herbaceous biomass blends: Impact on physical properties, chemical composition, and calorific value

AbstractIntercropping (or polyculture) is gaining a lot of interest as it increases yields, allows better utilization of resources (water and nutrients), and provides better land management. The objective of this study is to understand the briquetting characteristics of woody and herbaceous biomass blends, which might result from intercropping. Tests were conducted on blends of lodgepole pine, switchgrass, and corn stover biomass using three hammer mill screen sizes (i.e., 4.8, 12.7, and 19.05 mm), three blend moistures (12%, 15%, and 18%, w.b.), and two‐ and three‐blend ratios (i.e., 1:1 and 1:1:1) using a pilot‐scale hydraulic briquette press. The briquette properties, such as unit and bulk density, durability rating after 5 days of storage (as they tend to attain stable density), and the energy consumption of the process were measured. The results indicate that moisture content of 12% and 15% (w.b.) and smaller hammer mill screen size of 4.8 mm increased the unit and bulk densities to >750 and >430 kg/m3 and moisture content (15% and 18% (w.b.)) and hammer mill screen size of 12.7 and 19.05 mm produced briquettes with durability rating values of >95%. The higher moisture content of 18% (w.b.) and the hammer mill screen size of 12.7 and 19.05 mm had the highest energy consumption. The proximate and ultimate analysis showed that energy content improved by blending lodgepole pine with both corn stover and switchgrass and also showed increased calorific value and reduced ash content. Scanning electron microscopy micrographs showed interlocking of particles and cracks in the briquettes. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd

Hydrothermal Carbonization as a Strategy for Sewage Sludge Management: Influence of Process Withdrawal Point on Hydrochar Properties

Conventional activated sludge systems, still widely used to treat wastewater, produce large amounts of solid waste that is commonly landfilled or incinerated. This study addresses the potential use of Hydrothermal Carbonization (HTC) to valorize sewage sludge residues examining the properties of hydrochars depending on HTC process conditions and sewage sludge withdrawal point. With increasing HTC severity (process residence time and temperature), solid yield, total Chemical Oxygen Demand (COD) and solid pH decrease while ash content increases. Hydrochars produced from primary (thickened) and secondary (digested and dewatered) sludge show peculiar distinct properties. Hydrochars produced from thickened sludge show good fuel properties in terms of Higher Heating Value (HHV) and reduced ash content. However, relatively high volatile matter and O:C and H:C ratios result in thermal reactivity significantly higher than typical coals. Both series of carbonized secondary sludges show neutral pH, low COD, enhanced phosphorous content and low heavy metals concentration: as a whole, they show properties compatible with their use as soil amendments.