Characterization of char derived from various types of solid wastes from the standpoint of fuel recovery and pretreatment before landfilling

Carbonization is a kind of pyrolysis process to produce char from organic materials under an inert atmosphere. In this work, chars derived from various solid wastes were characterized from the standpoint of fuel recovery and pretreatment of waste before landfilling. Sixteen kinds of municipal and industrial solid wastes such as residential combustible wastes, non-combustible wastes, bulky wastes, construction and demolition wastes, auto shredder residue, and sludges were carbonized at 500 degrees C for 1h under nitrogen atmosphere. In order to evaluate the quality of char as fuel, proximate analysis and heating value were examined. The composition of raw waste had a significant influence on the quality of produced char. The higher the ratio of woody biomass in waste, the higher heating value of char produced. Moreover, an equation to estimate heating value of char was developed by using the weight fraction of fixed carbon and volatile matter in char. De-ashing and chlorine removal were performed to improve the quality of char. The pulverization and sieving method seems to be effective for separation of incombustibles such as metal rather than ash. Most char met a 0.5 wt% chlorine criterion for utilization as fuel in a shaft blast furnace after it was subjected to repeated water-washing. Carbonization could remove a considerable amount of organic matter from raw waste. In addition, the leaching of heavy metals such as chrome, cadmium, and lead appears to be significantly suppressed by carbonization regardless of the type of raw waste. From these results, carbonization could be considered as a pretreatment method for waste before landfilling, as well as for fuel recovery.     

Evolution of organic matter during composting of different organic wastes assessed by CPMAS 13C NMR spectroscopy

In this paper, the evolution of organic matter (OM) during composting of different mixtures of various organic wastes was assessed by means of chemical analyses and CPMAS ¹³C NMR spectroscopy measured during composting. The trends of temperatures and C/N ratios supported the correct evolution of the processes. The CPMAS ¹³C NMR spectra of all composting substrates indicated a reduction in carbohydrates and an increase in aromatic, phenolic, carboxylic and carbonylic C which suggested a preference by microorganisms for easily degradable C molecules. The presence of hardly degradable pine needles in one of the substrates accounted for the lowest increase in alkyl C and the lowest reduction in carbohydrates and carboxyl C as opposite to another substrate characterized by the presence of a highly degradable material such as spent yeast from beer production, which showed the highest increase of the alkyl C/O-alkyl C ratio. The highest increase of COOH deriving by the oxidative degradation of cellulose was shown by a substrate composed by about 50% of plant residues. The smallest increases in alkyl C/O-alkyl C ratio and in polysaccharides were associated to the degradation of proteins and lipids which are major components of sewage sludge. Results obtained were related to the different composition of fresh organic substrates and provided evidence of different OM evolution patterns as a function of the initial substrate composition.     

Revisiting the elemental composition and the calorific value of the organic fraction of municipal solid wastes

In this work, the elemental content (C, N, H, S, O), the organic matter content and the calorific value of various organic components that are commonly found in the municipal solid waste stream were measured. The objective of this work was to develop an empirical equation to describe the calorific value of the organic fraction of municipal solid waste as a function of its elemental composition. The MSW components were grouped into paper wastes, food wastes, yard wastes and plastics. Sample sizes ranged from 0.2 to 0.5 kg. In addition to the above individual components, commingled municipal solid wastes were sampled from a bio-drying facility located in Crete (sample sizes ranged from 8 to 15 kg) and were analyzed for the same parameters. Based on the results of this work, an improved empirical model was developed that revealed that carbon, hydrogen and oxygen were the only statistically significant predictors of calorific value. Total organic carbon was statistically similar to total carbon for most materials in this work. The carbon to organic matter ratio of 26 municipal solid waste substrates and of 18 organic composts varied from 0.40 to 0.99. An approximate chemical empirical formula calculated for the organic fraction of commingled municipal solid wastes was C₃₂NH₅₅O₁₆.     

Spectroscopic characterization of organic matter of a soil and vinasse mixture during aerobic or anaerobic incubation

Mineralization potentials are often used to classify organic wastes. These methods involve measuring CO₂ production during batch experiments, so variations in chemical compounds are not addressed. Moreover, the physicochemical conditions are not monitored during the reactions. The present study was designed to address these deficiencies. Incubations of a mixture of soil and waste (vinasse at 20% dry matter from a fermentation industry) were conducted in aerobic and anaerobic conditions, and liquid samples obtained by centrifugation were collected at 2 h, 1 d and 28 d. Dissolved organic carbon (DOC) patterns highlighted that: there was a “soil effect” which increased organic matter (OM) degradation in all conditions compared to vinasse incubated alone; and OM degradation was faster under aerobic conditions since 500 mg kg^?1 of C remained after aerobic incubation, as compared to 4000 mg kg^?1 at the end of the anaerobic incubation period. No changes were detected by Fourier transform infrared spectroscopy (FTIR) between 2 h and 1 d incubation. At 28 days incubation, the FTIR signal of the aerobic samples was deeply modified, thus confirming the high OM degradation. Under anaerobic conditions, the main polysaccharide contributions (ν(C–O)) disappeared at 1000 and 1200 cm^?1, as also confirmed by the ¹³C NMR findings. Under aerobic incubation, a 50% decrease in the polysaccharide proportion was observed. Under anaerobic conditions, significant chemical modifications of the organic fraction were detected, namely formation of low molecular weight organic acids.     

Use of thermal analysis techniques (TG-DSC) for the characterization of diverse organic municipal waste streams to predict biological stability prior to land application

The use of organic municipal wastes as soil amendments is an increasing practice that can divert significant amounts of waste from landfill, and provides a potential source of nutrients and organic matter to ameliorate degraded soils. Due to the high heterogeneity of organic municipal waste streams, it is difficult to rapidly and cost-effectively establish their suitability as soil amendments using a single method. Thermal analysis has been proposed as an evolving technique to assess the stability and composition of the organic matter present in these wastes. In this study, three different organic municipal waste streams (i.e., a municipal waste compost (MC), a composted sewage sludge (CS) and a thermally dried sewage sludge (TS)) were characterized using conventional and thermal methods. The conventional methods used to test organic matter stability included laboratory incubation with measurement of respired C, and spectroscopic methods to characterize chemical composition. Carbon mineralization was measured during a 90-day incubation, and samples before and after incubation were analyzed by chemical (elemental analysis) and spectroscopic (infrared and nuclear magnetic resonance) methods. Results were compared with those obtained by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. Total amounts of CO₂ respired indicated that the organic matter in the TS was the least stable, while that in the CS was the most stable. This was confirmed by changes detected with the spectroscopic methods in the composition of the organic wastes due to C mineralization. Differences were especially pronounced for TS, which showed a remarkable loss of aliphatic and proteinaceous compounds during the incubation process. TG, and especially DSC analysis, clearly reflected these differences between the three organic wastes before and after the incubation. Furthermore, the calculated energy density, which represents the energy available per unit of organic matter, showed a strong correlation with cumulative respiration. Results obtained support the hypothesis of a potential link between the thermal and biological stability of the studied organic materials, and consequently the ability of thermal analysis to characterize the maturity of municipal organic wastes and composts.     

Waste plastics recycling by an entrained-flow gasifier

We studied an entrained-flow gasification process which efficiently converts waste plastics to energy at a high energy recovery rate. Waste plastics, after being shredded to <8 mm or <14 mm, were fed into an entrained-flow gasifier with air and oxygen. In the gasifier, organic substances were pyrolyzed, partially combusted, and then converted into synthetic gas (CO, H₂) at a high temperature (over 1600 K). The clarified gasification characteristics were that the lower heat value (LHV) of the product gas was over 4.2 MJ/Nm³ and the cold gas efficiency was approximately 60%. Other inert substances in the wastes such as ashes and metals were melted into slag and condensed on bag filters. The bag filters and a water scrubber removed impurities such as dusts, heavy metals, and hydrogen halides from the product gases. Solid hydrocarbons, which include char and soot, were removed at a hot cyclone and on the bag filters. Received: July 19, 2000 / Accepted: October 3, 2000     

Characterisation of Organic Matter and Carbon Cycling in Rehabilitated Lignite-rich Mine Soils

Open-cast lignite mining in the Lusatian mining district resulted in rehabilitated mine soils containing up to four organic matter types: (1) recent plant litter, (2) lignite deposited by mining activity, (3) carbonaceous ash particles deposited during amelioration of the lignite-containing parent substrate and (4) airborne carbonaceous particles deposited during contamination. The influence of lignite-derived carbon types on the organic matter development and their role in the soil carbon cycle was unknown. This paper presents the findings obtained during a six year project concerning the impact of lignite on soil organic matter composition and the biogeochemical functioning of the ecosystem. The organic matter development after rehabilitation was followed in a chronosequence of rehabilitated mine soils afforested in 1966, 1981 and 1987. A differentiation of the organic matter types and an evaluation of their role within the ecosystem was achieved by the use of ¹⁴C activity measurements, ¹³C CPMAS NMR spectroscopy and wet chemical analysis of plant litter compounds. The results showed that the amount and degree of decomposition of the recent organic matter derived from plant material of the 30 year old mine soil was similar to natural uncontaminated forest soil which suggests complete rehabilitation of the ecosystem. The decomposition and humification processes were not influenced by the presence of lignite. On the other hand it was shown that lignite, which was thought to be recalcitrant because of its chemical structure, was part of the carbon cycle in these soils. This demonstrates the need to elucidate further the stabilisation mechanisms of organic matter in soils.     

CHARACTERIZATION OF URBAN WASTES ACCORDING TO FERTILITY AND PHYTOTOXICITY PARAMETERS

Several urban wastes of different nature and level of organic matter stability (municipal solid wastes, sewage sludges and composts) have been characterized analysing fertility and phytotoxicity parameters. Sewage sludges showed the highest N and P values of all the wastes. The total K content of the wastes was low but almost all was available to plants. Mature composts had the lowest organic carbon and humic substances values as a consequence of organic matter mineralization during the composting process. The soluble C at pH 2/precipitated C ratio decreased as the stability of the organic matter increased. In spite of the heterogeneity of the wastes analysed, the organic matter/total organic C ratio was largely constant with a mean value of 2.05. In no case did the heavy metal levels exceed the maximum allowed by the EU disposition for sewage sludges use in agriculture. The highest levels of phytotoxic substances occurred in the fresh wastes. The germination rates and root length were highest with mature composts. Germination index and root length were negatively correlated with water soluble carbon (WSC) and WSC/N ratio. The principal component analysis showed that extractable C, soluble C at pH 2 and water soluble C were the C fractions which most contributed to the total variability.     

Pyrolysis of municipal plastic wastes: Influence of raw material composition

The objective of this work is the study of pyrolysis as a feedstock recycling process, for valorizing the rejected streams that come from industrial plants, where packing and packaging wastes are classified and separated for their subsequent mechanical recycling. Four real samples collected from an industrial plant at four different times of the year, have been pyrolysed under nitrogen in a 3.5 dm³ autoclave at 500 °C for 30 min. Pyrolysis liquids are a complex mixture of organic compounds containing valuable chemicals as styrene, ethyl-benzene, toluene, etc. Pyrolysis solids are composed of the inorganic material contained in the raw materials, as well as of some char formed in the pyrolysis process, and pyrolysis gases are mainly composed of hydrocarbons together with some CO and CO₂, and have very high gross calorific values (GCV).It has been proved by the authors that the composition of the raw material (paper, film, and metals contents) plays a significant role in the characteristics of pyrolysis products. High paper content yields water in the pyrolysis liquids, and CO and CO₂ in the gases, high PE film content gives rise to high viscosity liquids, and high metals content yields more aromatics in the liquid products, which may be attributed to the metals catalytic effect.     

Size fractionation of organic matter and heavy metals in raw and treated leachate

This study characterized the organic matter and heavy metals in the leachate from two typical municipal solid waste (MSW) sanitary landfills in China, the recently established (3-year-old) Liulitun landfill and the mature (11-year-old) Beishenshu landfill, using a size fractionation procedure. The organic matter of all raw and treated leachate samples primarily existed in a truly-dissolved fraction with an apparent molecular weight (AMW) of <1 kDa, and its percentage decreased with an increase in overall AMW. The leachate from the newer landfill had a higher percentage of truly-dissolved organic matter. After anaerobic treatment, this leachate had a similar size fraction of organic matter to that seen for the raw leachate of the mature landfill. Biochemical processes had different removal efficiencies for various types of AMW organic matter, and the concentration of moderate AMW organic matter appeared to increase throughout these processes. Most of the heavy metals existed in a colloidal fraction (AMW >1 kDa and particle size <0.45 μm). The behaviors of different species of heavy metals had large variations. The size fractions of heavy metal species were significantly affected by treatment processes and landfill age, except for Zn. The concentration ratio of heavy metals to organic matter was maximal in the colloidal fraction and showed an inverse change to that seen for organic matter concentration changes caused by biochemical processes. Consequently, the pollution levels of heavy metals were substantially increased by treatment processes, although their concentrations decreased.     

Continuous-feeding vermicomposting as a recycling management method to revalue tomato-fruit wastes from greenhouse crops

Huge quantities of discarded fruits generated from greenhouse crops represent a worldwide environmental problem. The aim of this work was to assess the efficiency of vermicomposting as a recycling management option for biotransforming tomato-fruit wastes from greenhouses into an organic nutrient-rich product available for agricultural purposes. A pilot vermireactor was constructed. It was provided with a manure layer, where an initial population of Eisenia fetida was introduced and fed continuously at a high organic loading rate (13.6 kg TOC m^?3 wk^?1) for 150 days. Vermicompost chemical and enzymatic parameters as well as the bacterial and fungal community structure were determined for 210 days (vermicomposting plus a maturation period). Earthworm biomass increased after 90 days, and then declined due to increasing pH, electrical conductivity and ammonium concentration. The temporal patterns of dehydrogenase, β-glucosidase, protease and urease were related to earthworm growth and the stabilization of organic matter. Bacterial DGGE profiles differed between the period of degradation of labile substrates and the maturation step. Fungal communities at the stage of maximum earthworm biomass differed most, suggesting a gut passage effect. The end product was chemically stable and enriched in nutrients, demonstrating that tomato-fruit wastes can be successfully vermicomposted into a valuable soil amendment. We suggest continuous-feeding vermicomposting as an environmentally sound management option for greenhouse wastes.     

An assessment of municipal solid waste compost quality produced in different cities of India in the perspective of developing quality control indices

A study was conducted to investigate physico-chemical properties, fertilizing potential and heavy metal polluting potentials of municipal solid waste composts produced in 29 cities of the country. Results indicated that except a very few samples, all other samples have normal pH and EC. Organic matter as well as major nutrients N and P contents in MSW composts are generally low as compared to the composts prepared from rural wastes. Heavy metal contents in composts from bigger cities (>1 million population) were higher by about 86% for Zn, 155% for Cu, 194% for Cd, 105% for Pb, 43% for Ni and 132% for Cr as compared to those from smaller cities (<1 million population). Composts prepared from source separated biogenos wastes contained, on average, higher organic matter (by 57%), total N (by 77%) and total P (by 78%), but lower concentrations of heavy metals Zn (by 63%), Cu (by 78%), Cd (by 64%), Pb (by 84%), Ni (by 50%), and Cr (by 63%) as compared to those prepared from mixed wastes. Partial segregation at the site of composting did not improve quality of compost significantly in terms of fertilizing parameters and heavy metal contents. Majority of MSW composts did not conform to the quality control guideline of ‘The Fertilizer (Control) Order 1985’ in respect of total organic C, total P, total K as well as heavy metals Cu, Pb and Cr. In order to enable the relevant stakeholders to judge overall quality, a scheme has been proposed for the categorization of composts into different marketable classes (A, B, C, and D) and restricted use classes (RU-1, RU-2, and RU-3) on the basis their fertilizing potential and as well as potential for contaminating soil and food chain. Under the scheme, ‘Fertilizing index’ was calculated from the values of total organic C, N, P, K, C/N ratio and stability parameter, and ‘Clean index’ was calculated from the contents of heavy metals, taking the relative importance of each of the parameters into consideration. As per the scheme, majority of the compost samples did not belong to any classes and hence, have been found unsuitable for any kind of use. As per the regulatory limits of different countries, very few compost samples (prepared from source separated biogenos wastes) were found in marketable classes (A, B, C and D) and some samples (11–14) were found suitable only for some restricted use.     

Study of the organic matter evolution during municipal solid waste composting aimed at identifying suitable parameters for the evaluation of compost maturity

In this work the composting process of municipal solid wastes was studied in order to characterize the transformations of organic matter, particularly humic acid (HA). A composting process, lasting three months, was monitored by chemical methods; the following parameters were measured: water-soluble carbon concentration (WSC) and humic substances content (humic and fulvic acid (FA)). The effects of humification on the molecular structure of humic acid (HA) were also evaluated by Fourier transform infrared (FT-IR) and (13)C NMR spectroscopy. WSC concentration rapidly increased reaching a maximum at day-14 of the composting process and then declined. The humic and fulvic acid content (HA and FA, respectively) slightly increased during the process. The FT-IR and (13)C NMR spectra of HA indicate a high rate of change in structure during composting. The groups containing aromatic and carboxylic C increased, while polysaccharides and other aliphatic structures degraded during composting, resulting in HA structures of higher aromaticity. Therefore, spectrometric measurements could provide information significantly correlated to conventional chemical parameters of compost maturity.     

Solubilization and methanogenesis of a particulate industrial waste: Impact of solids loading and temperature

Effective anaerobic treatment of particulate wastes requires solubilization and acid formation prior to methanogenesis. In this case study of a particulate waste from a corn-processing industry, the influence of solids loading in solubilization, acid formation and methanogenesis was studied under mesophilic (35°C) and thermophilic (60°C) conditions. The waste was concentrated by centrifugation to initial suspended solids concentrations (TSS_i) of 150 to 350 g/L (15% to 35%). Anaerobic batch tests were conducted for 20 days, and significant solubilization of the particulate organic matter occurred in all cases. The thermophilic systems were more effective than the mesophilic systems with respect to solubilization of particulates, volatile solids destruction, acetic acid uptake, and methane generation. Methanogenesis appreared to be a rate-limiting step at higher TSS_i values, indicated by accumulation of volatile organic acids in the batch systems. Slower rates of methane production led to identification of the limiting solids loading for both temperature regimes. The results of this study can be used to evaluate the limitations of a single stage system for anaerobic treatment of organic particulate industrial wastes.     

An Overview of Sediment Organic Matter Records of Human Eutrophication in the Laurentian Great Lakes Region

The isotopic and molecular compositions of organic matter buried in lake sediments provide information that helps to reconstruct past environmental conditions and to assess impacts of humans on local ecosystems. This overview of sedimentary records from the North American Great Lakes region describes examples of applications of organic geochemistry to paleolimnological reconstructions. These lakes experienced a succession of human-induced environmental changes that started after completion of the Erie Canal in 1825. Agricultural deforestation in the mid-nineteenth century released soil nutrients that increased algal productivity and caused an associated increase in algal biomarkers in sediment records. Eutrophication that accompanied magnified delivery of municipal nutrients to the lakes in the 1960s and 1970s created excursions to less negative δ¹³C values in sediment organic matter. Increased organic carbon mass accumulation rates mirror the isotopic evidence of eutrophication in the Great Lakes.     

Usefulness of TAO model to predict and manage the transformation in soil of carbon and nitrogen forms from West-Africa urban solid wastes

The TAO model of Transformation of Added Organic materials (AOM) calibrated on AOMs and substrates of temperate areas was used to assess the transformations in soil of carbon and nitrogen forms of AOMs: raw materials, selected mixtures and composts from Ouagadougou urban wastes. AOMs were studied in terms of chemical and biochemical contents and for their C and N mineralization during incubations in a typical Ferric Lixisol of the sub-urban agriculture of Ouagadougou. The TAO model was used to predict the transformations of C (very labile, resistant and stable organic C) and N (very labile, resistant and stable organic N, produced and immobilized inorganic N) forms driven by AOM biochemical data. Without any change in calibration formulae, TAO predicted accurately the C transformations and inorganic N production of most of the tested AOMs, with a tendency to slightly overestimate C mineralization of previously well-composted materials and re-mineralization of immobilized N. Complementary adjustments using more complete data from laboratory experiments are suggested, but the model agrees with other data collected in the field and appears as a promising tool to optimise the management of urban wastes in the tropical area as well as for agro industrial organic fertilizers of the temperate zone. This application suggests ways to improve the management of urban wastes aiming to optimize agricultural yields, system sustainability and C sequestration in soil.     

A kinetic analysis of solid waste composting at optimal conditions

This discussion explores the possibility of having a measure of the biodegradable organic carbon content in solid wastes. Currently, indirect measures for determining the concentration of biodegradable organic matter are being used and most of them are based on respiration indices (oxygen consumption or carbon dioxide production) or chemical parameters (volatile solids or total organic carbon). The results obtained for the cumulative carbon dioxide production in composting experiments can be expressed as "aerobic biodegradable carbon" for the wastes that were studied. The calculation of a useful biodegradable C/N can also be obtained from the aerobic biodegradable carbon content. A comparison with some results obtained in measuring the concentration of "anaerobic biodegradable carbon" also is presented.     

Agrochemical characterisation of the solid by-products and residues from the winery and distillery industry

The winery and distillery industry produces a great quantity of residues, whose management and disposal are environmental problems due to their seasonal character and some polluting characteristics. The main solid by-products and residues generated are grape stalk, grape pomace or marc, wine lee, exhausted grape marc and winery sludge. In this study, 87 samples of winery and distillery residues were collected from different Spanish wineries and distilleries. Electrical conductivity, pH, total organic matter, organic carbon, polyphenols and contents of plant nutrients and heavy metals were determined. The purpose of this research was to study the composition of these wastes and to find relationships in order to use easily analysable parameters to estimate their composition. In general, the winery and distillery residues showed low pH (mean values ranged from 3.8 to 6.8) and electrical conductivity values (1.62-6.15 dS m(-1)) and high organic matter (669-920 g kg(-1)) and macronutrient contents, especially in K (11.9-72.8 g kg(-1)). However, a notable polyphenol concentration (1.2-19.0 g kg(-1)) and low micronutrient and heavy metal contents were also observed, some of these properties being incompatible with agricultural requirements. Therefore, conditioning treatments are necessary prior to possible use of these wastes. In all wastes, significant correlations were found between easily determined parameters, such as pH, electrical conductivity and total organic matter, and most of the parameters studied. The regression models obtained are also discussed.     

Long-term thermophilic mono-digestion of rendering wastes and co-digestion with potato pulp

In this study, mono-digestion of rendering wastes and co-digestion of rendering wastes with potato pulp were studied for the first time in continuous stirred tank reactor (CSTR) experiments at 55 °C. Rendering wastes have high protein and lipid contents and are considered good substrates for methane production. However, accumulation of digestion intermediate products viz., volatile fatty acids (VFAs), long chain fatty acids (LCFAs) and ammonia nitrogen (NH₄-N and/or free NH₃) can cause process imbalance during the digestion. Mono-digestion of rendering wastes at an organic loading rate (OLR) of 1.5 kg volatile solids (VS)/m³ d and hydraulic retention time (HRT) of 50 d was unstable and resulted in methane yields of 450 dm³/kg VS_fed. On the other hand, co-digestion of rendering wastes with potato pulp (60% wet weight, WW) at the same OLR and HRT improved the process stability and increased methane yields (500–680 dm³/kg VS_fed). Thus, it can be concluded that co-digestion of rendering wastes with potato pulp could improve the process stability and methane yields from these difficult to treat industrial waste materials.     

Toxicity of char residues produced in the co-pyrolysis of different wastes

Char residues produced in the co-pyrolysis of different wastes (plastics, pine biomass and used tyres) were characterized using chemical and toxicity assays. One part of the solid chars was submitted to extraction with dichloromethane (DCM) in order to reduce the toxicity of the char residues by removing organic contaminants. The different volatility fractions present in the extracted char (Char A) and in the raw char (Char B) were determined by progressive weight loss combustion. A selected group of heavy metals (Cd, Pb, Zn, Cu, Hg and As) was determined in both chars.The chars were subjected to the leaching test ISO/TS 21268 – 2, 2007 and the resulting eluates were further characterized by determining a group of inorganic parameters (pH, conductivity, Cd, Pb, Zn, Cu, Hg and As contents) and the concentrations of several organic contaminants (volatile aromatic hydrocarbons and alkyl phenols). An ecotoxicological characterization was also performed by using the bio-indicator Vibrio fischeri.The chemical and ecotoxicological results were analyzed according to the Council Decision 2003/33/CE and the criteria on the evaluation methods of waste ecotoxicity (CEMWE).The results obtained in this work indicated that the extraction with DCM is an effective method for the removal of organic contaminants of high to medium volatility from pyrolysis solid residues, thus decreasing their toxicity potential. Zn can be leached from the chars even after the DCM extraction treatment and can contribute to the ecotoxicity of the eluates obtained from chars.Both chars (treated and non treated with DCM) were classified as hazardous and ecotoxic wastes.