Effects of biochar and activated carbon on biogas generation: A thermogravimetric and chemical analysis approach (original) (raw)
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Biomass and Bioenergy, 2020
Granular activated carbon (GAC) as an economic and robust amorphous material could facilitate the syntrophic metabolism of acetogenesis and methanogenesis during anaerobic digestion of post-consumer substrates. In this study, influences of supplementing GAC on anaerobic co-digestion of brewery waste activated sludge and food waste for the production of methane were investigated by analysing the VFA production, ammonia concentration, pH, oxidation reduction potential, and electrical conductivity. Our data showed that a 45% increase in methane production with adding 1.5% (g/g) GAC was achieved. The maximum amount of 478 mL CH 4 /g volatile solids (VS) added was recorded along with 64% VS removal efficiency under a high ammonia concentration of 1420 mg L À 1. Moreover, the analysis of scanning electron microscopy exhibited the formation of biofilms with the supplement of GAC. Our results elucidate that GAC evidently enriched activities of hydrolysis and acetogenesis and enhanced the electron transfer efficiency for methanogenesis, which improved the production of methane significantly. Our results also demonstrate that the supplementation of GAC is an efficient method for the enhancement of biogas production from post-consumer wastes.
Anaerobic treatment utilizing the function of activated carbon
Water Science and Technology, 1997
Granular activated carbon (GAC) was used as supporting medium for bacteria in anaerobic process. The effectiveness of usina GAC was examined with laboratory•scale experiments. Synthetic wastewater containing phenol was converted to methane more successfully in fluidized bed using GAC. Fluctuation in influent concentration of phenol was intenlionally made to examine the dynamic response of the process. Temporary increase of influent phenol from 400 mg/l to 1000 mg/l. 2000 mg/l. and even to 4000 mg/l for 4 days did not affect the effluent phenol as much as methane production because adso'lltion and desorption capacity by GAC functioned as slllbilizer of the fluctuation. The adsorbed phenol was then gradually degraded into methane. Higher biomass concentration and lower adsorbed phenol were observed in the top part of the fluidized bed than in the bottom part.~1997 IAWQ.
2018
This study evaluates methane enrichment on biogas generated from Anaerobic Digester (AD) through CO 2 adsorption process so that biogas can be used as fuel for vehicle engines, power plants, and natural gas substitutes. The experiment was observed by passing biogas synthesis (45% CH4 + 55% CO 2 ) and biogas from cattle manure ±59.7% CH 4 , ± 37.1% CO 2 and ±3.2% other gases) in spontaneously pressurized adsorption column. In addition, observation of CO 2 adsorption capacity at various pressure and fixed temperature (27°C) was performed using pure CO 2 (±98%). Methane in biogas has been successfully purified to 92% at 0.5 L/min flowrate and 79.6 seconds retention time. The adsorbent will be saturated after gas flowing for 60 and 80 minutes for synthesis biogas and biogas from AD on the amount of adsorbent of 266 grams. A change of surface area of activated carbon (AC) after thermal regeneration at 160°C for 2 hours was 7.51% and regeneration efficiency was 67%. The adsorption process...
Preparation of biomass-based activated carbons and their evaluation for biogas upgrading purposes
Industrial Crops and Products, 2017
The use of waste biomass to produce adsorbent materials for the process of biogas upgrading might be a sustainable way to improve the energy matrix and help developing waste disposal technologies. The objective of this study was to prepare and evaluate activated carbons from coconut shell and babassu coconut, a waste biomass highly available at low cost. Both carbon samples were prepared by physical activation with CO 2 and characterized by N 2 adsorption isotherms at 77 K. The biosorbents produced from babassu and coconut shells presented BET surface areas of 1452 m 2 /g and 809 m 2 /g, respectively. Their applicability to upgrade biogas was assessed by experimental evaluation of pure (CO 2 and CH 4) and mixture (CO 2 /CH 4) adsorption equilibrium data at 293 K and pressures up to 10 bar. The results were used to compare the performance of the samples prepared in this work with a commercial sample. Adsorption capacity for carbon dioxide was similar for both synthesized samples, but the activated carbon from coconut shell presented better properties for CO 2 /CH 4 separation, as its selectivity (4.2 at 1 bar) and working capacity (1.0 mmol/g at 3 bar) are comparable to those of the commercial adsorbent over the low pressure range studied. This indicates that biomass waste is an interesting precursor for the production of activated carbons for biogas upgrading.
Recognizing the challenges of anaerobic digestion: Critical steps toward improving biogas generation
Fuel, 2020
Anaerobic digestion (AD) is one of the most promising technologies that can break the complex organic substrate into biogas. However, biogas production from biomass waste and its utilization for energy applications are still challenging due to the complex physical and chemical properties of organic waste, which affect the metabolic pathways and methane content. Consequently, attentions have focused on opportunities for further improvement in biogas yield and quality. This review identified the technical challenges associated with AD and potential solutions for improving biogas production. The critical steps toward improving biogas generation were identified as balancing the waste composition; adjusting nutrient content using trace elements; and using direct interspecies electron transfer (DIET) promoting additives. Direct interspecies electron transfer (DIET) promoting additives such as activated carbon, biochar and phenazine have shown a considerable effect on biogas production. These additives facilitate the electron transfer via direct interspecies electron transfer and improve digestibility via adsorption potential. The last section of the review describes a case study of the potential of using biochar and neutral red (phenazine) additives in one of the commercial landfills in the North Island of New Zealand. The results of this case study indicate that application of "neutral red" in the landfill site can significantly improve biogas generation for a period of 70 years.
Methane enrichment of biogas by carbon dioxide fixation with calcium hydroxide and activated carbon
Although, Biogas generated from anaerobic digestion process is a clean, carbon neutral and environmental friendly energy alternative, raw biogas needs to be purified necessarily before using. The removal of CO 2 from raw biogas ensures its better applications in engines, heating purposes and electricity generation. Reduction of CO 2 content also enhances the calorific value. Biogas generated from vegetable, fruit and cafeteria wastes for duration of 30 days with the average concentration for CH 4 and CO 2 as 62 and 34%, respectively have been observed. The CO 2 content was possible to reduce significantly by treating the raw biogas with purifying agents as: solid CaO, CaO solution and activated carbon. Purifying agent's mass and concentration and treatment time dependent biogas upgradation profile reveals that these novel purification processes are effective and affordable.
Journal of Renewable and Sustainable Energy
Anaerobic digestion (AD), one of the most promising routes for producing clean energy from biodegradable wastes, encounters difficulties at operational and mechanistic levels impacting its overall efficiency. Along with other solutions to overcome this problem, biochar has arrived as a worthwhile additive to enhance the performance of the process. This review aims to discuss various perspectives of biochar addition to an anaerobic digester. It summarizes the mechanism of biochar action during AD. A direct inter-species electron transfer offers a synergistic mechanism specifying different aspects of biogas production. The importance of characteristics of biochar (ion-exchange capacity, surface properties, electrical conductivity, and hydrophobicity) has been explained in enhancing AD performance. Studies indicate that a surface area >150 m2/g and a particle size <1 cm can be referred to as benchmark along with its supporting properties apt for AD. Researchers have recommended v...
Biomass Conversion and Biorefinery
Anaerobic digestion (AD) is a well-known biological conversion process to obtain a gaseous biofuel from organic matter: in fact, upgrading biogas to biomethane is a mean to substitute conventional natural gas. It is also known that biochar can improve the biogas production in AD processes. In this work, different biochars have been produced from various feedstocks at different process conditions. Biochars obtained from the carbonization of wheat straw (WS) and poplar (P) were produced in a Thermo Gravimetric Analyser at lab scale, at a temperature of 400 °C and 2 h of retention time at the maximum temperature, with a heating rate of 20 °C min−1. Another biochar from poplar (Pc) was also produced in a pilot plant (CarbOn, RE-CORD) working in oxidative pyrolysis conditions, at a temperature range between 500 and 600 °C. Biochars were oxidized with Oxone® using two different methods (ball-milling and simple aqueous solution mixing) to increase the amount of functional groups on their s...
Comparative study of the CH4/CO2 adsorption selectivity of activated carbons for biogas upgrading
Journal of Environmental Chemical Engineering, 2019
This works provides a new insight on the adsorption of CH 4 /CO 2 and its components on carbonaceous materials. The equimolar mixture adsorption isothemrs were obtained for 5 well characterized activated carbons at a temperature of 303 K on the pressure range of 0-3 MPa. A higher BET surface area in addition to a narrow pore size distribution centered at a pore size of 0.8 nm resulted in higher CH 4 /CO 2 total adsorption capacity. Furthermore, whilst the presence of basic functionalities on the surface of the adsorbents enhanced the adsorption of carbon dioxide, the adsorption selectivity was influenced by both textural and chemical properties of the samples. The selectivity was determined to be higher for carbon ROx 0.8 (selectivity factor of up to 4.7), a microporous steam activated carbon with a mild surface area (1323 m 2 g −1), narrow pore size distribution with an average pore size of 0.84 nm. Higher BET surface areas and average pore sizes resulted in a detriment of the selectivity. In addition, the presence of sulfur surface groups increased resulted in a rise of the selectivity factor.
Chemosphere, 2001
Disposal of sewage sludge is an increasingly expensive and environmentally sensitive problem throughout the world. Preparation of activated carbon from sewage sludge oers an attractive re-use alternative to the traditional disposal routes. The objective of this research work was to compare anaerobically digested sewage sludge (DS) and undigested sewage sludge (US) as source materials in the preparation of activated carbons. Prior to the preparation the properties of the two types of sewage sludges were determined and compared. Subsequently the sludge samples were activated with 5 M ZnCl 2 solution and thereafter pyrolysed at heating temperature of 650°C for 2 h with the heating rate of 15°C= min under a nitrogen atmosphere. The produced activated carbons were characterised by surface area and porosity analysis, CHN elemental composition and ash contents determination, and aqueous phase phenol adsorption tests. The results indicate that in comparison with the DS, the US had a higher carbon content and lower ash content, and accordingly yielded a better activated carbon with a higher BET surface area, pore volume, carbon content and phenol adsorption capacity. Ó