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Syngas production from biomass gasification is a potentially sustainable and alternative means of conventional fuels. The current challenges for biomass gasification process are biomass storage and tar contamination in syngas. Co-gasification of two biomass and use of mineral catalysts as tar reformer in downdraft gasifier is addressed the issues. The optimized and parametric study of key parameters such as temperature, biomass blending ratio, and catalyst loading were made using Response Surface Methodology (RSM) and Artificial Neural Network (ANN) on tar reduction and syngas. The maximum H2 was produced when Portland cement used as catalyst at optimum conditions, temperature of 900 °C, catalyst-loading of 30%, and biomass blending-ratio of W52:OPF48. Higher CO was yielded from dolomite catalyst and lowest tar content obtained from limestone catalyst. Both RSM and ANN are satisfactory to validate and predict the response for each type of catalytic co-gasification of two biomass for clean syngas production.

In this study, Palm Empty Fruit Bunch (PEFB) was utilized to produce bio-oil through non-catalytic and catalytic pyrolysis process. A fixed-bed reactor was applied to conduct pyrolysis experiments at atmospheric pressure. Comparison of bio-oils obtained from non-catalytic and catalytic pyrolysis wih different pyrolysis temperature was studied in terms product yield. The maximum bio-oil yield of 52.4% was obtained at pyrolysis temperature of 600 °C. Furthermore, based on Gas Chromatography-Mass Spectrophotoscopy (GC-MS) analysis, the percentage of phenolic compounds in bio-oil products from catalyzed pyrolysis showed more higher compared with the non-catalyzed pyrolysis.

In the paper “Formation mechanism of deep Cambrian dolomite reservoirs in the Tarim basin, northwestern China” ( Zhu et al., 2015 ), we concluded that hydrothermal alteration further enhanced porosity in the deep Cambrian dolomite reservoirs in the Tarim Basin, NW China. Professor Ehrenberg and Bjorlykke made comments that the hydrothermal dolomitization and increase in porosity were not well supported and casted doubt on the exploration potential. We insist the influence of hydrothermal alteration on and large exploration potential in the deep Cambrian dolomite reservoirs due to the unique geological conditions and the recent exploration results.

Air-gasification has emerged as preferred means of converting biomass to valuable synthesis gas (syngas). In present work, the gasification characteristics of pine sawdust were studied in a small-scale fluidized bed using calcined dolomite as in-bed material. Dolomite is characterized by higher tar conversion and H2 production during biomass gasification. Different operation conditions, equivalence ratios, reaction temperatures and dolomite contents, are studied for their influence on the gas compositions, gas yields, tar yields and higher heating values of producer gas. The results show that increasing either temperature or dolomite content enhances the tar conversion, where the latter accounts for the syngas with the lowest tar content. At 850 °C, the addition of 50 wt% dolomite can increase the gas yield from 1.48 to 1.85 Nm3/kg, and lowering the tar yield from 11.5 to 4.6 g/Nm3. Furthermore, the addition of more dolomite enhances the quality of the product gas, as indicated by increased values of the higher heating values of producer gas. Increasing the dolomite content within the 0–50% range resulted in higher H2 and CO contents, whereas the CH4 content declined. A slight change in CO2 content was observed with increasing dolomite content, which might cause by the limited carbonation. In contrast, the H2 content enhances non-linearly with the increase of dolomite content, which indicates that the catalytic activity of dolomite improves with the increase of dolomite share in the feedstock, due to the reforming of tar over dolomite. Increasing the ER from 0.14 to 0.3 elevates the gas yield, but decreases the tar yield and increases the H2 content in the product gas.

This research studies on the effect of additive (Dolomite) on Biomass powder (Cassava rhizome) which passes Torrefied process and fixed bed at 250 degrees Celsius for one hour and a half. The gasifier with up-draft type was used in this experiment. Air pressure was fixed at 0.1 Bar. The useful heat (Quseful) and Low heating valves (LHV) was investigated by using an Automatic Bomb Calorimeter. Moreover, the dolomite was varied 0, 10 and 15% by weight mixed with Cassava rhizome achieved with Torrefied process. When Low heating valves (LHV) slightly decreases from 21.96±0.22 MJ/kg to 18.15±0.50 MJ/kg, Quseful heat from the burning from gasifier sharply increase when it is mixed with dolomite from 753.34±39.18 to 1,003.97±33.49KJ respectively. The loading of dolomite has significance affecting the useful heat. The present study reveals that low heating valves (LHV) decreases and Quseful heat increase result from dolomite which gives a clean gas product and the Tar molecule can be easily broken. The CO2 gas from the combustion process was absorbed by CaO, which is the main component in dolomite. The cost of mixing 8.9% of Dolomite with Cassava rhizome is the optimum ratio for the biomass combustion process.

The Pila Spi Formation is one of the prominent formations forming continuous ridges in Kurdistan Region. The thickness of the formation ranges from 15 to 110 m, consisting of well-bedded limestone, dolomite, dolomitic limestone, and very rare marl beds. The study area is located about 15 km east of Koya town, next to the abandoned tunnel through a deeply cut valley which has exposed 50 m of the formation. However, the uppermost part of the exposed section may belong to one of the Oligocene formations of Kirkuk Group. The study area was selected within the Pila Spi Formation because the rocks of the same formation and along the same ridge, about 45 km west of the study area showed encouraging results for cement industry. The average CaO is about 51%, whereas the average MgO is 1.8%. Therefore, eight samples were collected at constant thickness from the exposed section. The samples were subjected to X-ray fluorescence (XRF) test to indicate the main oxides in the sampled section. The acquired results from the XRF tests showed that the chemical composition of the exposed rocks within the Pila Spi Formation is suitable for cement industry, also for paper and paint but needs some treatment. Accordingly, another eight samples were collected from the same section to increase the density of sampling, totaling to 16 samples.

Producing biochar from various agricultural and industrial biowastes through pyrolysis is recognized as an eco-friendly approach for solid waste management and remediation of contaminated soils. However, it remains debatable which type of feedstock and pyrolysis temperature could create biochar with better surface functionality and more suitable specific end use. Biochars prepared from rapeseed residue and rice straw at different pyrolysis temperatures (300 and 550 °C) were characterized using various chemical, physical, and spectroscopic techniques. Rapeseed residue and rice straw biochars produced at 550 °C had high pH (9.98 and 10.85, respectively), due to the decrease in total surface acidity with increasing temperature as demonstrated by Boehm titration data, and their high ash contents (18.70% and 24.21%, respectively). The negative charge on high-temperature biochar particles increased with pH, which was confirmed by the reduced zeta potential values (− 42.33 mV for rice straw biochar and − 31.86 mV for rapeseed residue biochar). The mineral phase of both biochars was dominated by sylvite and a small amount of dolomite and calcite, whereas quartz was only found in rice straw biochars. A pyrolysis temperature of 550 °C is suggested for producing biochars that can potentially immobilize toxic elements in the soil.

In the present study, the CaO/Natural Dolomite as a heterogeneous catalyst was applied to synthesize biodiesel from coconut oil. The physico-characteristics of CaO/Natural Dolomite catalyst were determined using X-ray diffraction (XRD), X-Ray Fluorescence, and porosity analysis (specific surface area, average pore size diameter and total pore volume). The performance of CaO/Natural Dolomite catalyst was examined in a batch reactor for transesterification reaction of coconut oil with methanol. From the experiments, the optimum process conditions were achieved at a 60°C of reaction temperature, a 5 wt.% of catalyst amount, and 6 : 1 of methanol to coconut oil mass ratio. The CaO/Natural Dolomite catalyst exhibits high catalytic activity and reliable to be applied in biodiesel synthesis as a heterogeneous base catalyst.

The thermochemical conversion may be an alternative for the final destination of poultry litter wastes. In this study, the effect of calcined eggshell (CE) and calcined dolomite (CD) on slow pyrolysis and air gasification performance of poultry litter waste was evaluated. The catalysts (CE and CD) presented potential for use in the in situ capture of the carbon dioxide produced in the pyrolysis process. In relation to the gasification tests, it can be concluded that both catalysts were effective in cracking the produced tar. Reductions in gas tar concentration of 25.47 and 54.32% were observed for CE and CD, respectively. The catalysts are effective at cracking light hydrocarbons (

We studied the properties of the bio-oil and char from fast pyrolysis of cassava rhizomes in a free-fall reactor, catalyzed by adding various soil conditioners (or improvers) as catalysts to the reactor at 500 °C and 200 g/h feed rate. Four conditioners were evaluated - granular TPI pH11 soil conditioner, volcanic rock, TPI pelletized organic fertilizer and super dolomite - and added at 50% (w/w) of the rhizomes. Bio-oil and gas yields decreased, whereas char yields increased, yielding bio-oil 57–59%, gas 14–20% and char 23–28%. With the catalysts, the bio-oil higher heating value increased, while that of char decreased: for cassava rhizomes with volcanic rock the bio-oil high heating value increased from 19.4 to 23.6 MJ/kg, whereas rhizomes with dolomite led to an increased viscosity from 27 to 34 × 10−3 mm2/s., Fast pyrolysis; Free-fall reactor; Bio-oil; Cassava rhizome; Soil conditioners.

This paper presents the results of research on the granulation process of leather industry waste, i.e., tanning shavings. It is economically justified to granulate this waste together with mineral additives that are useful in the processes of their further processing. Unfortunately, the granulation of raw, unsorted shavings does not obtain desired results due to their unusual properties. In this study, the possibilities of agglomeration of this waste were examined by a new method consisting of the production and then the granulation of wet pulp. During granulation, no additional binding liquid is added to the granulated bed. As part of this work, the specific surface of granulated shavings, the granulometric composition of the obtained agglomerates, and their strength parameters were determined. The use of a vibrating disc granulator, the addition of a water glass solution (in the pulp), dolomite, and gypsum made it possible to obtain durable, mechanically stable granules.

Biomass has a great potential for production of syngas and chemicals; however, it has stood in the shadow of natural gas (NG) and coal due to technical problems and issues such as tar formation. In this paper, syngas production from catalytic air–steam gasification of biomass in a fluidized bed was investigated. To enhance the yield of produced syngas and reduce its tar content by cracking, limestone, calcined dolomite, and olivine were used as catalyst. The maximum mole fraction of H2 was found to be 49.1 vol% at 1000 °C and a steam/biomass ratio (S/B) of 1.0 with dolomite present. Compared to olivine and dolomite, calcined dolomite was proved to be more effective for gas production and tar destruction. The results also showed that the particle size has a weak influence on gasifier performance, with only a slight decrease in tar content with decreasing biomass particle size.

The performances of the primary catalysts olivine, dolomite, γ-alumina and FCC spent catalyst were evaluated in the continuous steam gasification of sawdust in a bench-scale plant equipped with a fountain confined conical spouted bed reactor. The experiments were carried out at 850 °C, and the efficiency of the gasification process was defined by gas yield, H2 production, tar concentration and composition, and carbon conversion efficiency. The benefits of the fountain confiner not only helped to improve the gas-solid contact, and therefore favoured the primary catalysts’ reforming and cracking activity, but also enhanced H2 production and reduce tar formation. Thus, dolomite and γ-alumina recorded the lowest values of tar, 5.0 and 6.7 g Nm−3, respectively, which corresponded to 79% and 72% tar reduction compared to the inert sand, whereas olivine and the FCC spent catalyst recorded higher tar contents, 20.6 and 16.2 g Nm−3, respectively. It is noteworthy that light PAHs were the most abundant species in the tar (60 wt% of the whole tar content).

To investigate the possibilities of utilization of dolomite large size fractions (dropouts) and their effect on plants a five-year experiment was set in 2015. A fertilization value of large fractions (5–7 and 7–10 mm) of dolomite in two doses was studied. The biomass yield of crops in dolomite dropout treatment was around 90% from the treatment using dolomite flour (control). Losses of bases from the soil treated with high doses of dropouts did not exceed the migration losses of the treatment with dolomite flour. Dynamics of dolomite flour dissolution in the soil was empirically modeled. The data prove that high doses of the large-sized dolomite fractions act similarly to standard dolomite flour and have more persistent effects on soil and plants.

The flotation beneficiation of phosphate ore is increasingly facing challenges, especially for finely disseminated sedimentary ores rich in carbonates. This study aims to optimize and assess the impact of key hydrodynamic parameters including pulp density, air flowrate and impeller speed on flotation and metallurgical responses (i.e. grade, recovery, flotation rate constant and selectivity index (SI)). We carried out locked cycle flotation tests using the best conditions from the rougher flotation test to generate an experimental simulation of a continuous circuit. The mineralogical and chemical properties were characterized by mineral liberation analysis (MLA) and inductively coupled plasma optical emission spectroscopy (ICP-OES) techniques, respectively. A modified-McGill bubble size viewer was used for measuring bubble sizes and evaluating the interaction between hydrodynamic factors and bubble diameters. Finally, the design of experiment (DOE) method was applied to determine the relative intensity of the studied factors. It was found that under optimal conditions with the targets of high recovery and maximum SI, the final apatite concentrate achieved a recovery of 86.3% at a grade of 35.5%, while the MgO content was 1.2% and 84.3% of dolomite was removed from a feed ore containing about 25% P2O5, 4.6% MgO, and 41% CaO. Furthermore, another locked cycle flotation test showed that a 0.82% MgO content in the final apatite concentrate can be achieved with an apatite recovery of 75.6% at a P2O5 grade of 36.76% , and a ratio CaO/P2O5 = 1.33. The obtained concentrate in this investigation under the optimum conditions is the highest in both apatite recovery and grade with low MgO content reported in the literature.

In this article, a fluidized bed apparatus was used to study the effect of operating conditions on the yield of diesel oil. The calcined dolomite was also used as an additive to produce more diesel...

The depletion of fossil fuels has been a greater concern to the world due to the demand for energy that tremendously increasing with urbanization and population growth. For sustainable development, power industries are trying to find suitable substitute of petroleum fuel which is environment friendly and economically feasible. The biomass such as the production of bio-oil from chicken litter could be a possible alternative source of energy. The conversion of the feedstock was conducted through a catalytic pyrolysis process in an ex-situ fixed bed reactor heated at 500 °C with a heating rate of 50 °C/min. Proximate, ultimate, and calorific analysis of the feedstock was studied using TGA/DTG analysis, CHNS, and bomb calorimeter, respectively. GCMS and py-GCMS experiments on the bio-oil showed that the HHV of the feedstock was 16.01 MJ/kg. The addition of catalyst improved the quality of the bio-oil yield. The presence of dolomite and ZMS-5 catalyst enhances the phenols and aromatic content, respectively. Biomass to catalyst (B/C) ratio increased the oil production from 43.6g to 51.9g for dolomite and 43.6g–47.1g for ZMS-5 with the B/C ration of 20g:3g. Elevating the B/C ratio increases the pyrolytic liquid yield with greater influence on the furanic compound.

Fluidised bed (FB) technology can be advantageously used for the gasification of solid fuels. Calcined carbonate materials, such as limestone or dolomite, can be used directly in the fluidised bed of the gasification reactor to reform tars in situ and to enhance carbon conversion and cold gas efficiency of the gasification process. However, they exhibit poorer mechanical stability, they tend to be attrited and carried over from the reactor, and their catalytic activity decreases over time. Therefore, a portion of the material has to be replenished continuously or periodically. To decrease the amount of carbonate material that has to be replenished, a lower amount of lime (calcined limestone or dolomite) can be used in the FB, diluted by a mechanically robust material, such as silica sand or olivine. According to the literature, even concentrations in the order of 10–35% wt. of carbonate material in the FB of silica sand have a substantial effect on the decomposition of tars during steam or air gasification. However, the effect of the concentration of lime in the FB has not yet been described for CO2 gasification. In this paper, we focus on the effect of the ratio of calcined dolomitic limestone and silica sand in the FB (0%, 25%, 50% and 100% vol. of dolomitic limestone) for CO2+O2 gasification of biomass and compare it with H2O+O2 gasification at the temperature of 850 °C. The experiments were performed in a semi-autothermal spouting FB reactor, gasifying 1.4 kg h−1 of woody biomass. The effects of the concentration of dolomitic lime in the fluidised bed differed for H2O+O2 and CO2+O2 gasification. When gasifying with H2O+O2, optimal results were found with 50% vol. (35% wt.) lime in the FB, when the yield of tar was similar to the use of pure lime in the FB. When gasifying with CO2+O2, a substantial decrease in tar yield was observed when using 50% vol. (35% wt.) lime in the FB (compared to the use of pure silica sand); nevertheless, the use of undiluted lime in the FB remains the best option to attain minimal tar yield when gasifying with a CO2+O2 gasifying agent. In this case, the tar yield was decreased 8.7-fold, and the tar dew point was decreased by 124 °C (to 71 °C) compared to the non-catalysed case with silica sand being the fluidised bed of the gasifier.

This research is to study the pyrolysis process of cassava rhizome (CR) in a free-fall reactor. The objective was to study the effect of mixed soil improvement on the properties of bio-oil and char products. The rhizome cassava mixed soil improvement was 200 g / hr. Mixing ratio of cassava rhizome and soil improvement is 50 to 50 by weight. The mixed soil improvement were granular pH11 plus soil conditioner (L11), volcanic rock (VR), TPI pelletized organic fertilizer (OF) and super dolomite (SD). Temperature pyrolysis was at 500 degrees Celsius. The results showed that bio-oil yield and gas yield decreased while char yields increased. For mixed soil improvement, made higher heating value in bio-oil increased, while the char properties of higher heating value decreases.

Chromate and phosphate are contaminant frequently present in industrial effluents such as tanneries. The objective of this work is to evaluate the efficiency of different operational combinations with dolomite and banana peel for the adsorption of phosphate and chromate in binary solutions. Both adsorbents are residuals from construction and food industries, respectively. Therefore, its use propitiates the reduction of treatment costs and it is an approach to the premises of the circular economy. In this work, the dolomite and banana peel adsorption efficiencies in simple and binary systems were studied. Equilibrium and kinetics tests were carried out in batch and in a fixed bed reactor. Dolomite was found to be selective for the adsorption of phosphate and banana peel for that of chromate. The mixture of adsorbents produced similar phosphate and chromate removal than each adsorbent individually. Therefore, the removals of both contaminants from binary solutions were tested using a fixed bed reactor filled with the mix of adsorbents and the breakthrough curves were analyzed. The obtained removals were 99% of phosphate and 70% of chromate. Finally, a brief discussion was held on the reuse and disposal of saturated adsorbents.

Reprocessing and valorization of secondary resources is a possible solution to alleviate the supply-demand disparity for critical materials. The current study investigated the recovery of P and enrichment of REEs from Florida waste clay (WC). Clays, dolomite, and quartz are the main associated gangue minerals, while apatite is the predominant P-bearing mineral, and monazite and xenotime are the rare earth minerals in this WC. A 1.5-in. diam. hydro-cyclone unit was initially employed for the removal of clays. Froth flotation was then examined for the separation of values from the cyclone underflow. Various depressants and surface modifying agents were assessed for both direct and reverse flotation separations. Results showed that the direct flotation does not offer a solution for the selective recovery of P from WC. Despite their documented affinity for apatite and rare earths, hydroxamic acid collectors do not produce a selective separation. A single-stage reverse cationic process provides a more economically viable route due to its capability to avoid the loss of REEs. Test results of the single-stage reverse cationic process indicated that the P2O5 grade was increased to 21 wt.% from an initial grade of ∼8 wt.% with a corresponding recovery of approximately 80%. The REE content was elevated from an initial value of 307.1 ppm to 800 ppm, with an 80% recovery resulting from the same process. The removal of clays, silicates, and carbonates up to a point to meet the medium-grade phosphate ore specifications also facilitates the subsequent recovery of REEs using chemical separation.

Biogas is a valuable source of renewable energy produced from biodegradable organic materials via anaerobic digestion. The production of H2 by sorption enhanced steam reforming (SESR) of biogas has been studied thermodynamic and experimentally. A Pd/Ni–Co catalyst and dolomite as CO2 sorbent were used. The effect of biogas composition (CH4/CO2 vol.%) on the process was evaluated at 600 and 650 °C in a fluidized bed reactor using biogas CO2 concentrations of 5–50 vol.%. During conventional biogas steam reforming (SR), high CH4 partial pressures in the feed favor the process, producing high H2 concentrations. During biogas SESR, CO2 was effectively removed from the gas phase by the sorbent for all the biogas compositions, and it did not alter the process compared to pure methane. Steam methane reforming (SMR) and water-gas shift (WGS), together with carbonation, were the main reactions occurring during biogas SESR. Dry (or CO2) methane reforming did not occur under the conditions studied due to the relatively low temperature and the presence of steam. High H2 purity (98.4 vol.%) and H2 yield (91%) were experimentally obtained, pointing out the biogas SESR as a promising technology for the efficient production of high-purity, high-yield hydrogen from a renewable source., The authors thank Franefoss Miljøkalk A/S (Norway) for supplying Arctic dolomite. This work was carried out with financial support from the Spanish MICINN (Project ENE2017-83530-R) and from the Gobierno del Principado de Asturias (PCTI, Ref. IDI/2018/000115), both co-financed by the European Regional Development Fund (ERDF). M.V. Gil acknowledges support from a Ramón y Cajal grant (RYC-2017-21937) of the Spanish government, co-financed by the European Social Fund (ESF). A. Capa acknowledges a fellowship awarded by the Spanish MICINN (FPI program, PRE2018-083634), co-financed by the European Social Fund (ESF).

Solid recovered fuel (SRF) residue, which is leftovers from the SRF manufacturing process, usually is discarded in landfill because of its low heating value and high ash and moisture content. However, it could be used as a fuel after mechanical and biological treatment. Gasification experiments were conducted on treated SRF residue (TSRFR) to assess the viability of syngas production. Efforts were also made to improve the gasification performance by adding low-cost natural minerals such as dolomite and lime as bed material, and by blending with biomass waste. In the case of additive mineral tests, dolomite showed better performance compared to lime, and in the case of biomass blends, a 25 wt% pine sawdust blend with TSRFR showed the best performance. Finally, as an appropriate condition, a combined experiment was conducted at an equivalence ratio (ER) of 0.2 using a 25 wt% pine sawdust blend with TSRFR as a feedstock and dolomite as the bed material. The highest dry gas yield (1.81 Nm3/kg), with the highest amount of syngas (56.72 vol%) and highest lower heating value (9.55 MJ/Nm3) was obtained in this condition. Furthermore, the highest cold gas efficiency (48.64%) and carbon conversion rate (98.87%), and the lowest residue yield (11.56%), tar (0.95 g/Nm3), and gas pollutants content was observed.

Spent coffee waste (SCW) is extremely attractive to be exploited and utilized as a material source for energy generation and chemical production. This study concerned bio-oil production via non-catalytic and catalytic fast pyrolysis using SCW in a bubbling fluidized-bed reactor (BFR). In particular, a comparative analysis of the quality of the bio-oil produced was conducted for non-catalytic (using silica sand as the bed material) and catalytic (using dolomite, HZSM-5, hematite, and magnetite as the catalyst) fast pyrolysis. Scale-up modeling confirmed using the experimental data was performed at a feed rate of 100 kg h−1 (1,000-fold capacity), which showed different orders in the quality of energy (hematite > magnetite > dolomite > HZSM-5 > silica, in order of energy from highest to lowest) owing to the realistic integration of the BFR with other components in plants, such as the combustor, compressor, and separator. Further, techno-economic analysis of scale-up system revealed that the unit production costs of bio-oil were 0.0151, 0.0034, 0.0143, 0.0095, and 0.0102 $ MJ−1 for silica, dolomite, HZSM-5, hematite, and magnetite, respectively (dolomite > hematite > magnetite > HZSM-5 > silica, in order of unit cost from lowest to highest). Among them, dolomite and hematite showed competitive unit production costs compared to the price of conventional crude oil (0.0098 $ MJ−1). The importance of coupling laboratory-scale experimental results with scale-up modeling and economic analysis has thus been demonstrated for practical feasibility studies of the SCW pyrolysis for bio-oil production.

China has rich phosphate rock resources, but with their continuous depletion, the rich ore resources have become increasingly scarce, which makes the exploration of collophane more important. Medium- and low-grade phosphate rock cannot be utilized until their impurities have been removed through mineral processing. However, due to the similar physical and chemical properties of dolomite and phosphorus minerals, the separation of dolomite from phosphate rock is a challenge for the beneficiation of phosphate rock. In this study, a collector that can separate dolomite from apatite by selective flotation was combined. The agent, named D12, is a new anionic surfactant that was obtained by the phosphorylation of ether-based nonionic surfactants. In order to determine the performance of the D12 collector, it was used in a flotation test. In this process, the raw ore had phosphorus oxide (P2O5) grade of 22.06 percent and magnesium oxide (MgO) content of 5.94 percent. The grinding fineness of 0.074 mm was approximately 87.33 percent. For roughing, the dosages of sulfuric acid (H2SO4), citric acid and collector were 7 kg/t, 1.5 kg/t and 0.5 kg/t, respectively. In the cleaning stage, the dosages of H2SO4 and collector were 5 kg/t and 0.3 kg/t, respectively. Concentrate grade of 31.02 percent and recovery rate of 68.64 percent with an open circuit were obtained under these conditions. Moreover, concentrate grade of 30.31 percent and recovery rate of 84.47 percent with MgO content of 0.92 percent were obtained with closed-circuit beneficiation indexes. The agent, D12, is promising to be applied to the industrial practice of mineral processing of phosphate rock.

We present a feasibility study of different adsorbent materials, namely residual fish scales biosorbent (FS), mineral dolomite (DL) and commercial resin (CR) in the heavy metals removal in multicomponent solution based on the properties of a real effluent from automotive battery recycling industry. Considering the effluent complex characteristics, the materials were assessed aiming to provide not only the heavy metals removal, but also the effluent neutralization and lower sludge generation. For this, all the studied materials were physicochemically and morphologically characterized with the aim of understanding the mechanisms involved in the process. Further, the elemental compositions of the solid and liquid phases generated from each treatment process were assessed by X-ray fluorescence spectrometry. The effluent presented highly acidic characteristics and heavy metals above the legislated limits for discharge (Fe, Zn and Pb). Each adsorbent material followed different mechanisms which led to dissimilar removal and neutralization capacities. The CR showed remarkable heavy metals removal capacity governed by an ion exchange mechanism; conversely, it did not show a neutralization effect. In contrast, FS and DL presented lower removal capacities by complex simultaneous phenomena (ion exchange, precipitation and/or complexation), but a great neutralization potential related to leaching of alkaline constituents. When sludge generation is considered as a key factor, mitigation and enhancement of treated effluent quality could alternatively be addressed by employing the materials in hybrid processes. Hence, the associated use of such materials could be viable yet very challenging for both neutralization and removal of heavy metals from the battery effluent.

Anaerobic digestion (AD) of rapid acidification wastewaters (RAW) in high-rate reactors is highly dependent on properly controlling the buffer capacity of systems, which is usually done by dosing alkalizing/alkali compounds. Although reliable, this strategy does not ensure complete effectiveness, depending on the chemical used, also affecting negatively the economic performance of the treatment plants. The aim of this study was to assess an alternative approach to conventional alkalizination in the AD of RAW by using dolomitic limestone as the alkalizing agent in single-phase continuous systems fed with cassava processing wastewater (CPWW). Two different amounts of limestone were used in horizontal-flow reactors subjected to increasing organic loading rates (OLRs). The effects of dolomite on the specific methanogenic activity (SMA) of the methanogenic sludge, as well as the fertilizer potential of the treated CPWW were also assessed. Limestone supplementation positively affected the SMA of the sludge by increasing methane production and decreasing the lag phase. Limestone also proved to be an adequate alkalizing agent for the horizontal-flow systems, continuously providing the systems with bicarbonate alkalinity at relatively high OLRs (up to 8.5 kg COD m−3 d−1), even during organic overloading periods. The availability of specific inorganic constituents, primarily K+, Ca2+ and Mg2+, also confirmed the biofertilizer potential of the treated CPWW, although higher organic matter removal levels would still be required for safer nutrient cycling.

In the Conceição - MG mine, there are significant reserves of dolomitic itabirite, which is considered overburden material. This study aimed to develop a flotation route for the concentration of this dolomitic BIF according to the requirements of the steel industry. The characterization of samples, comminution, liberation size, microflotation of the pure dolomite and hematite minerals were performed to establish the conditions for selective separation in bench flotation tests. The microflotation tests showed that the soybean oil at pH 6 preferably floats the dolomite in relation to the hematite. The corn starch depressant at a pH higher than10 preferably depresses the hematite relative to the dolomite. The bench flotation tests revealed interactions between the factors pH, percentage of solids in the pulp, soybean oil and starch dosage. The optimal results for bench flotation tests were achieved under the following conditions: pH at 10.5, percentage of solids of 27wt%, dosages of soybean oil and corn starch of 400g/ton and 351g/ton, respectively.

Sub-bituminous coal [SC] activation with dolomite is the future technology in utilizing coal as an alternative organic material [Humic Substance]. This study aims to study the effect of SC activated with dolomite in improving the chemical properties of Ultisols and palm oil growth at the main-nursery stage [Elaeis guineensis Jacq.] In Dharmasraya. The experimental design was in Randomized Completely Block Design with three replications consisting of 6 treatments : A = 150g SC planting hole−1; B = 300g SC planting hole−1; C = 450g SC planting hole−1; D = 150g SC + 10% [15g] dolomite planting hole−1; E = 300g + 10% [30g] dolomite planting hole−1 and F = 450g SC + 10% [45g] dolomite planting hole−1. The results showed that the effect of activation on SC differs from those treatments without activation with dolomite. Effect of 450g SC activated with dolomite planting hole−1 is significant on the chemical properties of Ultisols, such as increasing in pH, available P, organic C, total N, CEC [Cation exchange capacity], and K, Ca, Exch-Mg, by 0.44 units, 1.33 ppm P, 0.44% C, 0.04% N, 0.25, 0.27, and 0.29 cmolckg−1, compared to 450g SC without activator and an increase in palm oil growth on height [12.33cm], stem diameter [0.84cm] and N, P, and K nutrient concentration from leaf of plant [0.014% N, 0.004% P, 0.002% K], compared to 450g SC without activator.

In this study, the volatile from sewage sludge (SS) pyrolysis is passed through the hot char from the same source in a fixed bed reactor. The reforming effect of the sewage sludge char (SSC) on the quality and energy distribution of liquid and gas products is studied. In comparison to dolomite, SSC presents a better tar-eliminating effect from 450 to 650 °C. The production of combustible products, including CH4, H2, and CO, is significantly increased by both the catalytic cracking on the SSC surface and the volatile–char reaction. After the reforming effect at the pyrolysis temperature of 650 °C, the gas yield is increased from 17.19 to 34.27 wt % and the fraction of combustible components is increased by 54.28 vol %. The quality of the oil is also upgraded by reforming of SSC, with the escalation of the light components, and nitrogen-containing and oxygenated fractions are greatly reduced. When the pyrolysis temperature is fixed at 650 °C and the reforming temperature is increased from 450 to 650 °C, the...

Phosphate, when present in water, forms one of the basic nutrients that lead to eutrophication and its associated negative impacts. The use of raw dolomite powder as an adsorbent was found to be very effective in the removal of phosphates from various waters and wastewater matrices. Ayoub and Kalinian (Water Environ Fed 78:353–361, 2006) reported phosphate removals, amounting to 100%, over more than 300 bed volumes at inflow concentrations between 0.30 and 0.40 mg/L. This marked achievement led to the present study with the objective of defining the effects of the various parameters involved in the process and determining the optimal operating condition to achieve effective and sustainable removal efficiencies. Experimental work was conducted by passing three types of influent water and two types of wastewater jacked with a phosphate salt (KH2PO4) through a fluidized column bed of dolomite powder, where the effect of various parameters, including system operation mode, adsorbent particle size, rate of flow through the bed (contact time), initial phosphate concentration, influent pH, and the presence of competing anionic solutes on the adsorption of phosphate was evaluated. The results asserted that the most effective mode of operation for the system was the fluidized bed configuration. Results further showed that the smaller-sized dolomite powder (

Limestone and dolomite were used to treat acidic mine effluent in a lab scale study of a passive treatment. This study focused on improving pH level and reducing heavy metals concentrations of the mine effluent. Both limestone and dolomite with aggregate sizes of 10-20 mm and 30-50 mm were packed in a 40 L tank filled with acidic mine effluent. The mine effluent was sampled from an active iron ore mine in Bukit Besi, Terengganu. The experiments lasted for 10 days and the mine effluent samples were collected to measure pH, alkalinity and heavy metal concentrations at various retention time. Experimental results revealed that the limestone had shown a better performance compared to the dolomite in increasing pH and reducing metals concentrations of the mine effluent. Most heavy metals were able to be reduced successfully with only manganese (Mn) had shown a poor reduction.

This paper studied the gasification of two solid recovered fuels (SRFs) in a laboratory scale fluidized bed reactor. The gasification performance and syngas quality were assessed under the influence of: gasification temperature (750 °C and 850 °C), SRF feedstock (RT or FL), bed material (sand or dolomite) and gasification agent (air or O2/H2O). One of the parameters to evaluate the gasification performance was the concentration of minor contaminants (tar, N, S and Cl compounds) in the syngas. High temperature (850 °C) and the use of calcined dolomite as bed material improved gas quality (increasing H2/CO ratio, carbon conversion and reducing tar content) during SRF gasification. The use of O2/H2O also enhanced gas composition (i.e. higher calorific value), although further research is needed to fully understand the release of minor contaminants under these conditions. The results indicated that the presence of minor contaminants in the syngas was strongly affected by the composition of the SRF itself, the composition of the ash fraction and the bed material, and provided valuable information to assess the most adequate conditions for SRF gasification.

Food waste can be meat, fish, cooked food scraps, moldy bread, bone scraps, cakes, expired foods, dairy products, fruits and vegetables. Food waste which is put into the trash will decay and produce a foul odor which in turn will invite flies and cause potentially diseases. Most of the food waste that is processed using the composting process needs to spend a relatively long time, which is about 1-3 months or even 6-12 months. This study aims to accelerate composting time through the addition of additive microorganisms in various quantities. Four aerobic composter reactors were utilized in this study. Variations of additive microorganisms added to the research object were 0 in reactor (control), 8 g in B2 reactor, 16 g in B3 reactor, and 32 g in B4 reactor. All reactors were added with dolomite lime. During the composting process temperature, pH, water content and macroelement were tested. The results showed that the mature and stable compost was reached on the seventh day and produced from B2 reactor. In That reactor treated food waste and additive microorganisms with a ratio of 7:3, and 1 g dolomite lime. The level of C/N ratio produced from B2 reactor was 16.71. The value of C/N ratio was better than B3 reactor which produced C/N of 18.37. The control reactor produced a C/N ratio of 21.84 and mature and stable compost was reached on the 14th day. All in all, this study was regarded to be successful in accelerating the degradation of food waste into mature and stable compost in just seven days.

H2 production from biogas (60%CH4 + 40%CO2) by sorption enhanced steam reforming (SESR) was thermodynamically and experimentally studied in a fluidized bed reactor. Biogas is an interesting renewable biomass resource for hydrogen production due to its sustainable nature. SESR combines the catalytic reforming reaction of biogas with simultaneous CO2 removal in a single step. A Pd/Ni–Co hydrotalcite-like material (HT) was used as catalyst and dolomite as CO2 sorbent. The effects of temperature (550–800 °C), steam/CH4 molar ratio (2–6) and gas hourly space velocity (GHSV) (492–3937 mL CH4 gcat−1 h−1) on the process performance were evaluated. CO2 in biogas was effectively removed by the sorbent from the gas phase at 550–700 °C, without influencing the reforming process. H2 yield increased with temperature from 550 to 650 °C, but H2 concentration decreased at temperatures higher than 600 °C, requiring a tradeoff between both parameters to select an optimum operating temperature. H2 purity of 98.4 vol% was obtained at 550–600 °C and H2 yield of 92.7% was reached at 650 °C. Higher steam/CH4 ratios enhance the process, whereas higher space velocities decrease H2 yield. Results demonstrate that high-purity high-yield biohydrogen can be produced by the SESR of a renewable biomass resource as biogas., The authors thank Franefoss Miljøkalk A/S (Norway) for supplying Arctic dolomite. This work was carried out with financial support from the Spanish MICINN (Project ENE2017-83530-R) and from the Gobierno del Principado de Asturias (PCTI, Ref. IDI/2018/000115), both co-financed by the European Regional Development Fund (ERDF). M.V. Gil acknowledges support from a Ramón y Cajal grant (RYC-2017-21937) of the Spanish Government, co-financed by the European Social Fund (ESF).

The paper presents the results of a study on the use of soda production sludge (SPS) as a lime soil conditioner. SPS with a less than 0.1 mm fraction is the most suitable in terms of physical, chemical, and toxicological properties and meets the requirements of GOST-14050-93 «Limestone (dolomite) dust. Specifications» on the content of the active substance, the mass fraction of calcium and magnesium carbonates. Reclamative properties of SPS were studied on soil samples taken in the territory removed from the sanitary protection zone of the oil refinery. It was found that all soil samples have a phytotoxic effect on pea seedlings. The introduction of SPS in amount of 1-3 g per kg of soil stimulates the development of the ground part and roots of oats and peas, and also increases the germination energy of oat and pea seeds in the initial soil samples by 2÷10 times. The introduction of SPS into the samples of the studied soils at a dose of 1-3 g/kg stimulates the development of colonies of Azotobacter bacteria and leads to an increase in the total number of soil microorganisms. The introduction of SPS in an amount of 3 g per kilo of soil leads to a slight increase in the environment reaction and an increase in the content of water-soluble salts in the soil up to 2 times. In view of this, it is necessary to control that the content of water-soluble salts does not exceed the established standards. Based on the results obtained, we consider it expedient to use soda production sludge as a lime soil conditioner and for the reclamation of industry-disturbed soils.

Fluidized bed gasifiers are becoming quite popular because of their higher conversion efficiencies, ability to handle wide variety of fuels and recent development in the field of catalytic gasification. Air gasification of rice husk was carried out in a pilot scale bubbling fluidized bed gasifier (ID: 197 mm and H: 1.6 m) at a constant air flow rate of 43 m 3 /h. Burning charcoal was initially used for the heating of bed material instead of electric heater in order to make it more suitable for the rural areas. For the bed of sand experiments were carried at four different equivalence ratios (ER) 0.28, 0.3, 0.33 and 0.35 to determine the suitable ERs for the catalytic gasification. Two naturally occurring catalyst: raw dolomite and untreated olivine were added separately in different proportions (10–60 wt.%) in the sand bed in order to determine their effectiveness at its higher and lower content in the sand bed and to decide the optimum combination of inert bed material and catalyst. Compact on-line method for the measurement of tar + suspended particulate matter (SPM) was developed and used. ER of 0.3 and 0.33 were found the most suitable ERs for the catalytic gasification. Dolomite provided 45 and 50% while olivine provided comparatively less 41 and 44% tar + SPM reduction at the ER of 0.3 and 0.33, respectively. However, olivine generated less fine particles and consumed 66% less energy for bed heating than dolomite. Improvement in the carbon conversion and thermal efficiency by 5–7% were obtained with the addition of catalysts. 60% silica was extracted from the rice husk ash which was taken from the discharge of the cyclone separators.

The gasification of dried sewage sludge was performed using various additives (activated carbon, Ni-impregnated activated carbon, dolomite, and CaO) in a two-stage gasifier to produce a tar-free gas with a low NH3 content. This research also examined the effect of feed rate on the tar removal efficiency and the stability of the two-stage gasification system conducting a ∼3.7 h gasification. In all experiments, natural olivine was used as a fluidized bed material, and air as a gasifying agent. The equivalence ratio was kept almost constant at ∼0.36. When Ni (8.9 wt%)/activated carbon was applied, a tar-free gas with 31.3 vol% H2 and 114 ppm NH3 was obtained, with a tar removal efficiency of 97%. A higher feed rate turned out to have a negative effect on the tar removal. The gasification performed using multiple additives for ∼3.7 h produced a tar-free gas with 146 ppm NH3.

Production of hydrogen rich gas from gasification of biomass was studied at bench-scale using oxygen as the gasifying agent. A series of experiments were performed to investigate the effects of different operating parameters on the performance of the gasification process. These included the oxygen to fuel equivalence ratio (0.12–0.4), reaction temperature (700–850 °C), reaction residence time (45–120 min), and catalyst type. The catalysts selected are marly clay, calcium hydroxide, dolomite, and cement kiln dust. Within the range of the experimental conditions tested, the results suggest that the best operating conditions for the gasification process are; temperature, 800 °C, an oxygen to fuel ratio of 0.25, a reaction time of 90 min, and calcined cement kiln dust as a catalyst. The results have also demonstrated that the product gas from gasification of cotton stalks with calcium hydroxide has higher H2 and CO concentration (45 and 33%). In addition gasification of cotton stalks with calcined cement kiln dust resulted in higher hydrogen and CO enrichment as well as higher overall gas yield (39vol%, 33vol%, and 1.5 m3/kg) compared to other agriculture residues of corn stalks and rice straw.

Water pollution from acid mine drainage (AMD) has received extensive attention in recent years. However, previously used active treatment methods have many problems, such as high cost, difficult maintenance, and a large amount of sludge production. This study presented a novel process that combined dolomite aeration and an oxidation filter bed. The acidic water generated from coal mine drainage water was the object of research. First, the effects of important operating factors (such as particle size, initial pH, aeration rate, and flow rate) to neutralize acidity and remove contaminants from real mine effluents were studied. Based on these results, the treatment efficiency and sludge performance under repeated treatment were compared between the dolomite and limestone processes. Then the treatment effect under recycling condition was also compared between dolomite and limestone processes. Finally, the application and economic benefits of this combined process in the practical treatment project were evaluated. It was revealed that the Fe(II), total Fe removal efficiency all could reach nearly 100%, and the sulfate removal efficiency and pH could reach 96.2% and 6.53, respectively, after 3 h reaction under optimal conditions (dolomite particle size 0.5–1 cm, initial pH 4, aeration rate 10 L/min, flow rate 100 mL/min). The comparison results show that the dolomite process could achieve good effects while the neutralization agent consumption rate was at least 3 times slower than limestone. Meanwhile, the effluent quality was stable, and the sludge quantity was only one-third that of the sludge quantity produced from the limestone process. The setting capacities of sludge in the dolomite process were better than the limestone process. Additionally, the consumption of dolomite was better than that of limestone. The findings indicated that important cost reduction could be realized by substituting the limestone process with the dolomite aeration oxidation filter bed process, and has good performance in the engineering application.

Recovering phosphorus from livestock wastewater could partly mitigate the global phosphorus resource crisis. Crystallization is a promising method for removing phosphorus from wastewater, but the costs of calcium- and magnesium-containing reagents are increasing. Cheap, available, efficient materials are required to replace conventional calcium and magnesium reagents. Here, we describe a new approach to removing and recovering phosphorus from livestock wastewater of a large pig farm, containing a high phosphorus concentration. The effects of the pH, stirring speed, stirring time, and extract dose (containing calcium and magnesium) on phosphorus removal from livestock wastewater were investigated. The product was characterized by X-ray diffractometry, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Under optimized conditions (pH 9.0, stirring speed 200 r/m, stirring time 600 s, Ca 207.62 mg/L, Mg 122.86 mg/L), 92% of the phosphorus was removed from livestock wastewater. The product was mainly the hydroxyapatite (Ca5(PO4)3OH) precursor amorphous calcium phosphate but also contained 1.65% (by mass) magnesium ammonium phosphate (MgNH4PO4·6H2O) crystals. The cost of dolomite to treat 1 m3 of high-phosphorus wastewater was 0.20 yuan (45.9%, 25.9%, and 75.9% lower than for pure MgCl2, MgSO4, and CaCl2, respectively) in 2019. Using dolomite to provide calcium and magnesium effectively decreases the crystallization process cost and should encourage the use of crystallization to remove phosphorus from wastewater.

Pyrolysis of waste materials aiming to produce biochar has been considered as an effective strategy to add value and to recycle such materials. The properties of the produced biochars depends on pyrolysis temperature and feedstock type, for example. Some waste materials have been still poorly studied. The objective of this study was to evaluate the changes in physicochemical characteristics, mineral composition, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) of biochars derived from agricultural and industrial wastes produced by different pyrolysis temperatures and feedstocks. Two agricultural solid wastes (poultry litter - PL and swine manure - SM) and three industrial wastes (construction wood - CW, tire - TR and PVC plastic - PVC) were pyrolyzed at five temperatures (300, 400, 500, 600 and 700 °C) in an oxygen-limited environment at a heating rate of 10 °C min−1 for one hour. Increased pyrolysis temperature reduced the yield of solids and volatile compounds and increased pH in water and Ksoluble in all studied biochars. Nevertheless, the temperature caused no significant changes in electrical conductivity, water-soluble nutrients and total elements, and CEC, in the industrial wastes (CW, TR and PVC). The XRD patterns revealed similarities in mineral formation among the studied biochars, including quartz, sylvite, calcite and dolomite. Data of FTIR spectra evidenced the presence of aromatic and aliphatic functional groups. The results obtained enable the design of biochars for a desired purpose, which might be solutions for agronomic and environmental issues, taking into account the effects of pyrolysis temperature and the type of waste to be processed.

Seven cosmetic-pharmaceutical talcum powders from different commercial brands, currently for sale in Spanish pharmacies, have been studied in order to determine their mineral and pharmacopoeia quality. Four samples met the required conditions to be classified both of “cosmetic quality” and “pharmacopoeia quality”. These conditions are: absence of potentially carcinogenic minerals, talc purity of more than 90%, low levels of toxic elements and suitable compositional levels of Al, Mg and Ca. The remaining three samples were classified as of “industrial quality”. Although these are free from fibrous minerals, the high carbonate content, specifically dolomite (close to 40%) and calcite (about 10%), impacts on the purity in talc by significantly reducing its quantity to the point that the material no longer satisfies many of the compositional tests of the European Pharmacopoeia. The detailed microanalysis with SEM-EDX and size measurements of elongated particles present in the samples showed them to be harmless as their mineral composition is talc and they appear in very low proportions. The SEM-EDX study highlighted the properties for which talcum powder has classically been employed for topical cutaneous use. The comparison of the current results with those of the Spanish market of talcum powder sold in pharmacies in the decade of the 1980s resulted in three principal findings. First, the fibrous minerals have disappeared. In the past, a significant number of samples showed evidence of amphiboles. Second, the purity in talc in samples of cosmetic quality has improved from 94% to 96%. Finally, in the 1980s there were no samples in the Spanish market with talc purity as low as today (60%). Dolomite is currently present in excessive quantities in some talcum powders.

The present study investigated the applicability of waste vermiculite and dolomite as fine aggregate, known as appropriate mineral adsorbents to enhance the quality of urban runoff, for improving the mechanical properties of porous concrete. 180 samples were mixed by adding 5-30% vermiculite and dolomite, as fine aggregate, and combining them with ordinary sand; lime sand (combining of 5-15% of each). Results showed that although adding dolomite culminated in a minor reduction of permeability– average of about 30%-, the average of compressive strength was augmented by 120%. Results of compressive strength of dolomite samples were repeated in mixtures containing vermiculite (an increase of 57%). While exploiting vermiculite in high percentages (20, 25, and 30) resulted in an extensive decrease in the permeability (94%), it was improved to an acceptable level (about 40%) after using vermiculite in combination with ordinary sand (lime sand). All dolomite and improved vermiculite mixtures, after combining vermiculite with ordinary sand, had appropriate performance in draining storm-urban runoff; such that in the weakest case, stimulated storm runoffs with heights of 10, 20, 30 and 40 cm were completely drained only after 17, 36, 59 and 87 seconds, respectively. Also, using vermiculite resulted in reducing the concrete weight (about 100 kg). Generally, although a little reduction in the permeability was seen, but using waste vermiculite and dolomite improved the mechanical properties of porous concrete significantly.

The degradation of resource quality, coupled with an increase in resource consumption, impose significant challenges on the capability of phosphate mineral processing operations to supply acceptable products at a rapid rate to fertilizer plants. A serious ongoing concern for phosphate mining operations is to produce a product containing sufficiently low dolomite content ( Attrition scrubbing of pebble phosphate samples (top size of 1 mm and 2.97% MgO grade) has been performed under different conditions of scrubbing time, pH, temperature and rpm. The samples subjected to scrubbing were wet screened at 53 µm and the chemical analyses (ICP analyses) of the coarse and fine products indicate that scrubbing can help in the rejection of fines, which contain a significant amount of MgO. The best scrubbing results were obtained for a scrubbing time of 20 min, and an MgO content in the coarse product (concentrate) of approximately 1.72%, with a phosphate P2O5 recovery of 63.47%. It is evident from these results that the phosphate concentrate (+53 µm) from scrubbing does not meet the required MgO level as desired for further processing by acidulation. Further, for a particular scrubbing test, the minus 53 µm was subjected to further size separation at 20 µm and 7 μm. Particle size and chemical analyses are reported for the scrubbed fractions, including 53 × 20 µm, 20 × 7 µm, and −7 µm size classes. Results suggest that considerable liberation of dolomite from the pebble phosphate may be expected at a particle size of 20 µm.

This work focused in the evaluation of Oreochromis niloticus fish scales (FS) as biosorbent material in the removal of Zn from a synthetic effluent based on automotive battery industry effl...

In this study, two thermochemical processes, namely steam gasification and supercritical water gasification (SCWG), were comparatively studied to produce hydrogen from food wastes containing about 90% water. The SCWG experiments were performed at 400 and 450 degrees C in presence of catalyst (Trona, K2CO3 and seaweed ash). The maximum hydrogen yield was obtained at 450 degrees C in presence of K2CO3 catalyst. In second process, hydrothermal carbonization was used to convert food wastes into a high-quality solid fuel (hydrochar) that was further gasified in a dual-bed reactor in presence of steam. The steam gasification of hydrochar was carried out with and without catalysts (iron-ceria catalyst and dolomite). The maximum hydrogen yield obtained from steam gasification process was 28.08 mmol/g dry waste, about 7.7 times of that from SCWG. This study proposed a new concept for hydrogen production from wet biomass, combination of hydrothermal carbonization following steam gasification. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.