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The construction industry had approached a critical limit which led to the increase of cement production. The production of cement would cause a broader environmental implication. Cement production is a major source of carbon dioxide emission. Carbon dioxide gas contributes about 63.33% of global warming since the production of one ton of cement would emit about one ton of carbon dioxide to the environment. To mitigate this issue, the research community has investigated the use of waste materials that possess similar chemical properties with cement content as a material for partial cement replacement. The use of rice husk ash has shown to be a contending candidate in the literature. Therefore, this paper attempts at reviewing the performance of rice husk ash as partial cement replacement. It could be observed from the literature that concrete with 5% up to 15% of rice husk ash showed an equivalent performance to ordinary concrete in compressive, flexural, and tensile strength. Thus, rice husk ash can be used as a material replacement in concrete and reduces pollution that originates from cement production and open burning of rice husk.

Construction sludge frequently has high alkalinity after its generation or during the intermediate treatment process. The aim of this study is to experimentally investigate the potential of combining accelerated carbonation and a paper sludge ash-based stabilizer (PSAS) to neutralize the alkalinity of construction sludge in a short period and to improve its strength for use as a recycled material. The experimental results indicate that the addition of a PSAS significantly granulated the alkaline sludge, and once granulated, the PSAS successfully accelerated the pH neutralization of the alkaline sludge. It was also found that the decrease in dry density ρd and the degree of saturation Sr of the PSAS-treated sludge was able to reduce the period required for the pH neutralization, tN. The decrease in ρd is thought to allow fresh CO2 gas to penetrate the specimen more easily. However, if Sr is below a certain limit, it does not strongly facilitate the reduction of tN. This implies that pH neutralization cannot be accelerated when the amount of water in the sludge is below a certain level. Moreover, it was found that mean particle diameter D50 also affected tN. The strength development of the PSAS-treated sludge was evaluated using a series of cone index tests. It was found that the strength of the alkaline sludge without the PSAS was significantly decreased by accelerated carbonation, but was significantly increased even after accelerated carbonation when the PSAS was present. Due to the porosities of the remaining PS ash particles, most of the contribution of the water absorption and retention performance of the PSAS to the strength development of the PSAS-treated sludge was secured after accelerated carbonation. In addition, the granulated particles of the PSAS-treated sludge retained their granular shape to some extent. Therefore, it is presumed that the friction and interlocking of the particles did not decrease significantly. It was also found that, after carbonation, the qc of the PSAS-treated sludge increased more rapidly than that of the alkaline sludge without the PSAS. A further detailed examination of the test results showed that under air-curing conditions, the qc of the treated sludge with accelerated carbonation increased relatively gradually compared to that of the treated sludge without accelerated carbonation.

In papermaking, pre-flocculation of fillers such as ground calcium carbonate (GCC) improves the tensile strength of paper sheets. However, the pre-flocculated fillers mostly suffer from the instability of the floc shape such as the decrease in floc diameter with time elapse after preparation and no improvement of bulk and stiffness. The addition of calcium compounds such as calcium oxide or calcium hydroxide to the pre-flocculated GCC, and injection with carbon dioxide caused pre-flocculated GCC flocs to be covered with newly formed calcium carbonate. This product, called post hybrid calcium carbonate (pHCC), was found to be more stable in size and gave better sheet strength than the pre-flocculated ones. Furthermore, pHCC gave remarkably higher bulk and stiffness than the pre-flocculated flocs did without impairing smoothness that was essential in printing paper. The proper use of pHCC in papermaking could allow the production of high loaded paper with more than 10% higher filler contents, which could reduce paper production cost and save drying energy. The proportion of the newly formed calcium carbonate in pHCC, turbulence intensity at preparation stage, and the effect of storage time were investigated.

The present paper aims to develop sustainable concrete to reduce the impact of concrete on environment using groundnut husk ash. In the present study, Life Cycle Assessment (LCA) of concrete is evaluated in terms of Global Warming Potential (GWP), Acidification Potential (AP), and Eutrophication Potential (EP) which indicates the impact of Carbon Dioxide (CO2) and other gases emission on environment during manufacturing of concrete. Six types of concrete cubes i.e CM, G-2.5, G-5, G-7.5, G-10, G-12.5, and G-15 designed concrete are manufactured by replacing cement with GHA by mass at different replacement levels (0%,2.5%, 5%, 7.5%, 10%, 12.5% and 15%).Cubes were tested for compressive strength after 7 and 28 days. Results indicated that upto 12.5% replacement of cement with groundnut husk ash (GHA) by mass, the compressive strength of GHA was more than the characteristic strength of M20 grade concrete. LCA of control mix and GHA concrete was done from cradle – to – gate boundaries. In control mix concrete, cement has the highest environmental impact about 80%, 73% and 54% of total impact for GWP, AP and EP respectively Results indicated that by utilizing GHA, reduction of 10%, 9.1%, and 7.2% in GWP, AP, and EP impact values occurs respectively. Therefore, it is concluded that the use of groundnut husk ash in concrete will lessen the impact of carbon dioxide and other green house gases (GHG) on environment and adds to the sustainability aspect by utilizing waste.

Desiccant materials are recently discovered as a viable alternative in dehumidification technology due to their naturally hygroscopic qualities and minimal energy requirement. This paper discusses the performance of four brand samples of selected desiccants used for dehumidification. In this study, dehumidification ability and indoor air quality (IAQ) tests were carried out. The dehumidification ability test was conducted in a controlled environmental chamber at a temperature of 25°C, relative humidity of 70%, and air velocity of 2 m/s for 45-minute session. Meanwhile, the IAQ test was carried out in a naturally ventilated test room, and six IAQ parameters (relative humidity, air velocity, air temperature, particulate matter (PM10), airborne bacteria and carbon dioxide (CO2) were studied. The IAQ test was performed for five different conditions: control, application of brand samples A, B, C and D in the test room. From this study, it was found, brand A (0.6823 g/kg) and brand B (0.6849 g/kg) had a relatively good dehumidification ability during the 45-minute dehumidification ability test compared to brand C (0.3108 g/kg) and brand D (0.3982 g/kg). The IAQ test revealed that brand A had the biggest variation in indoor-outdoor relative humidity of 13.12%, while brand D had the smallest difference of 11.83%. Brand B had the highest average PM10 concentration of 0.037 μg/m3. The airborne bacterial count for all conditions had no statistical significance, indicating the application of desiccants were not effective in reducing airborne bacteria. From this study, it can be concluded that calcium chloride (brand A and B) samples performed better than silica gel (brand C and D) samples in terms of dehumidification ability and IAQ profile.

The rapidly rising level of carbon dioxide in the atmosphere resulting from human activity is one of the greatest environmental problems facing our civilization today. Most technologies are not yet sufficiently developed to move existing infrastructure to cleaner alternatives. Therefore, techniques for capturing carbon dioxide from emission sources may play a key role at the moment. The structure of the UiO‐66 material not only meets the requirement of high stability in contact with water vapor but through the water pre‐adsorbed in the pores, the selectivity of carbon dioxide adsorption is increased. We successfully applied the recently developed methodology for water adsorption modelling. It allowed to elucidate the influence of water on CO2 adsorption and study the mechanism of this effect. We showed that water is adsorbed in octahedral cage and stands for promotor for CO2 adsorption in less favorable space than tetrahedral cages. Water plays a role of a mediator of adsorption, what is a general idea of improving affinity of adsorbate. On the basis of pre‐adsorption of methanol as another polar solvent, we have shown that the adsorption sites play a key role here, and not, as previously thought, only the interaction between the solvent and quadrupole carbon dioxide. Overall, we explained the mechanism of increased CO2 adsorption in the presence of water and methanol, as polar solvents, in the UiO‐66 pores for a potential post‐combustion carbon dioxide capture application., MOF trap: We successfully applied a recently developed methodology for water adsorption modelling that allows to elucidate the influence of water on CO2 adsorption and study the mechanism of this effect. We show that water is adsorbed in octahedral cage and stands for promotor for CO2 adsorption in less favorable space than tetrahedral cages. We explain the mechanism of increased CO2 adsorption in the presence of water and methanol, as polar solvents, in the UiO‐66 pores for a potential post‐combustion carbon dioxide capture application.

Low quality and yield of methane severely hindered the industrial application of straw biogas fermentation and there has been no effective solution found so far. In this study, a novel method has been developed to improve the quality and yield of methane during biogas fermentation. We coupled microbial electrolysis cell (MEC) with normal anaerobic fermentation to enhance the yield and purity of methane. This novel fermentation process achieved the methane purity of more than 85%, which was critically higher than those of previously published reports. With the stimulation from microorganisms and electric current, the degradation of fiber has been greatly enhanced. The MEC system significantly improves the yield and purity of biogas, bringing a new path to synthesize the methane by the carbon dioxide and hydrogen ions in solution under the electron. Electrochemical index analysis showed the extra methane synthesis which was mainly led by the external circuit electron transfer. The result of the gas chromatograph and solid degradation rate showed that the carbon source of extra methane was CO2 produced in normal fermentation and extra volatile solid degradation. These results show that MEC significantly enhanced the quality and yield of methane in a straw fermentation process, giving insights for normal anaerobic fermentation.

Mutations in the mitochondrial genome (mtDNA) are ubiquitous in humans and can lead to a broad spectrum of disorders. However, due to the presence of multiple mtDNA molecules in the cell, co-existence of mutant and wild-type mtDNAs (termed heteroplasmy) can mask disease phenotype unless a threshold of mutant molecules is reached. Importantly, the mutant mtDNA level can change across lifespan as mtDNA segregates in an allele- and cell-specific fashion, potentially leading to disease. Segregation of mtDNA is mainly evident in hepatic cells, resulting in an age-dependent increase of mtDNA variants, including non-synonymous potentially deleterious mutations. Here we modeled mtDNA segregation using a well-established heteroplasmic mouse line with mtDNA of NZB/BINJ and C57BL/6N origin on a C57BL/6N nuclear background. This mouse line showed a pronounced age-dependent NZB mtDNA accumulation in the liver, thus leading to enhanced respiration capacity per mtDNA molecule. Remarkably, liver-specific atg7 (autophagy related 7) knockout abolished NZB mtDNA accumulat ion, resulting in close-to-neutral mtDNA segregation through development into adulthood. prkn (parkin RBR E3 ubiquitin protein ligase) knockout also partially prevented NZB mtDNA accumulation in the liver, but to a lesser extent. Hence, we propose that age-related liver mtDNA segregation is a consequence of macroautophagic clearance of the less-fit mtDNA. Considering that NZB/BINJ and C57BL/6N mtDNAs have a level of divergence comparable to that between human Eurasian and African mtDNAs, these findings have potential implications for humans, including the safe use of mitochondrial replacement therapy.Abbreviations: Apob: apolipoprotein B; Atg1: autophagy-related 1; Atg7: autophagy related 7; Atp5a1: ATP synthase, H+ transporting, mitochondrial F1 complex, alpha subunit 1; BL6: C57BL/6N mouse strain; BNIP3: BCL2/adenovirus E1B interacting protein 3; FCCP: carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; MAP1LC3A: microtubule-associated protein 1 light chain 3 alpha; MAP1LC3B: microtubule-associated protein 1 light chain 3 beta; mt-Atp8: mitochondrially encoded ATP synthase 8; MT-CO1: mitochondrially encoded cytochrome c oxidase I; MT-CO2: mitochondrially encoded cytochrome c oxidase II; mt-Co3: mitochondrially encoded cytochrome c oxidase III; mt-Cytb: mitochondrially encoded cytochrome b; mtDNA: mitochondrial DNA; MUL1: mitochondrial ubiquitin ligase activator of NFKB 1; nDNA: nuclear DNA; Ndufa9: NADH:ubiquinone oxireductase subunit A9; NDUFB8: NADH:ubiquinone oxireductase subunit B8; Nnt: nicotinamide nucleotide transhydrogenase; NZB: NZB/BINJ mouse strain; OXPHOS: oxidative phosphorylation; PINK1: PTEN induced putative kinase 1; Polg2: polymerase (DNA directed), gamma 2, accessory subunit; Ppara: peroxisome proliferator activated receptor alpha; Ppia: peptidylprolyl isomerase A; Prkn: parkin RBR E3 ubiquitin protein ligase; P10: post-natal day 10; P21: post-natal day 21; P100: post-natal day 100; qPCR: quantitative polymerase chain reaction; Rpl19: ribosomal protein L19; Rps18: ribosomal protein S18; SD: standard deviation; SEM: standard error of the mean; SDHB: succinate dehydrogenase complex, subunit B, iron sulfur (Ip); SQSTM1: sequestosome 1; Ssbp1: single-stranded DNA binding protein 1; TFAM: transcription factor A, mitochondrial; Tfb1m: transcription factor B1, mitochondrial; Tfb2m: transcription factor B2, mitochondrial; TOMM20: translocase of outer mitochondrial membrane 20; UQCRC2: ubiquinol cytochrome c reductase core protein 2; WT: wild-type.

In this work, a biomethane fuel was obtained from biogas, using a solid matrix of ashes obtained from a central heating plant fed by wood. Biomethane composition was studied in an experimental pilot plant that treats organic waste through dry anaerobic digestion. European limits were considered and respected for the biomethane injection into the gas grid. The process was able to completely remove carbon dioxide (CO2) during its initial phase. After 50 h of test CO2 concentration started to appear in the outlet gas. This behaviour is related to the ash content, reactive phases (e.g., Ca hydroxides) and fine particle size (

In current trends the wood pellets are very significance role in the replacing of boiler fuel; it is a surrogate and renewable fuel. For this study comparative analysis of the fuel performance in the boiler is carried out effectively. Two categorize of fuel like as raw wood pellets and wood pellets are immersed in the bio- ethanol are taken to this experimental work. The thermal characteristics and thermal efficiency of the boiler with influence of two types of fuels are conducted efficiently. Normally the wood pellets having small pores it is used to absorb the bio ethanol while in immersion. Amid in the two fuels, wood pellets immersed in the bio ethanol are provided and increase the thermal properties as well as thermal efficiency compared to raw pellets. The flue gas constituent’s percentage such as carbon monoxide, oxygen, carbon monoxide and nitrogen oxides are analyzed, additionally the high temperature of flue gas also measured in the outlet of the chimney. No alteration is made in the boiler setup which is comfortable to both fuels.

Carbon dioxide and hydrogen sulfide are the main contaminants in biogas, which reduce its calorific value and cause wear on metallic appliances through corrosion. There are no comparative studies on the potential of dry adsorption and wet wood ash (carbonation) process on biogas upgrade. The current study for the first time investigates the effects of different process parameters on the use of wood ash for purification of biogas and compares the performance of the two processes. The chemical composition of wood ash was characterized using X-ray fluorescence (XRF) while biogas was analysed using gas chromatography and a digital biogas analyser. The effects of process parameters on biogas carbonation method were investigated. The highest CO2 uptake and methane increment achieved by use of wood ash slurry was 2.30 mmol/g-wood ash and 88%, respectively. This high CO2 uptake was possibly due to the high content of oxides (46% TS) in natural wood ash. The optimum conditions of adsorbent/water ratio and biogas flow rate for methane enhancement were 1:4, and 100 ml/min, respectively. In dry adsorption processes, an increase in mass of activated wood ash from 2.5 to 35 g increased CO2 removal from 8.9 to 67.9%. Furthermore, the evaluation of carbonation adsorption indicated that the process followed pseudo-first order kinetics. Activation of wood ash did not significantly improve its CO2 uptake by carbonation while the uptake by activated wood through dry adsorption was comparable to that of raw wood ash through carbonation process. Conclusively, raw wood ash by carbonation process is a good candidate recommendable for purifying biogas in household digesters.

Developing new energy sources is of critical significance to satisfy the growing energy demand and also reduce the emissions of carbon dioxide (CO2) gas. The conversion of CO2 into value-added prod...

Coffee is one of Indonesia's leading plantation commodities, which is ranked third in the world. Currently, coffee-based drinks have become a lifestyle in the millennial era. The high interest in coffee affects the economy of the community. Various efforts were made to further encourage the level of coffee consumption, especially in the form of beverages. On the other hand, it is necessary to diversify the product by highlighting the technology side, such as making effervescent which is easier, more practical, and can be enjoyed directly with cold water. Effervescent is known as a product that can cause gas bubbles as a result of the reaction of acids and bases when dissolved in water. The resulting gas bubbles are carbon dioxide which gives a sparkling effect (a taste sensation like sparkling water). The use of coffee as an effervescent raw material is related to its taste, bioactive compounds, and antioxidants. Coffee extract powder can be made from robusta and arabica coffee roasted at medium level with low-temperature crystallization, spray drying, freeze drying, and vacuum drying. Other materials that need to be added such as acid sources, bases, fillers, and binders can affect the effervescent characteristics such as tablet hardness, moisture content, hygroscopicity, and dissolution time. The recommended composition is citric acid, sodium bicarbonate, dextrin, and PVP (Polyvinilpyrrolydone).

Cement brick is an essential construction component, which uses cement as the primary binder. The cement industry was identified as the major contributor to carbon dioxide emission, which is a greenhouse gas. The application of agro-industrial waste as partial cement replacement can reduce the negative impacts on the environment. In this study, the palm oil wastes, namely Palm Oil Clinker Powder (POCP) and Palm Oil Boiler Ash (POBA), were used as partial cement replacement. A total of 60 specimens were prepared with 0%, 10%, 20%, and 30% cement replacement by POCP and POBA. The physical and mechanical properties of bricks, such as density, water absorption, voids, and compressive strength, were investigated. The results show that the brick with 20% CP and BA could be used as a severe weathering brick.

Underground Coal Gasification (UCG) is the process of converting the materials used to make synthetic gas in a feasible and economically attractive manner as a method for harnessing energy from underground coal sources. Coal gasification will produce a gas producer in the form of synthetic gas (syngas) with the main components consisting of carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2) and nitrogen (N2) and low pollutants. The highest temperature produced with MT 47 lignite coal using an oxygen velocity of 5 liters/minute was 2400 C at the 35th minute, while the lowest temperature was 950 C at the 95th minute. For Subbituminous AL 51 coal using an oxygen velocity of 5 liters/minute, the highest temperature is 3540 C at 75 minutes, while the lowest temperature is 1060 C at 130 minutes. At an oxygen velocity of 5 liters/minute the flash point / burn test is on the MT 47 lignite coal type in the 10th minute and at a temperature of 1700 C. Meanwhile, the AL 51 subbituminous coal type is in the 30th minute and at a temperature of 3130 C. Based on the discussion and analysis of data from the gasification test of lignite and subbituminous coal with variations in oxygen velocity of 5 liters/minute, the results obtained are that lignite coal burns faster (burn test) in the 10th minute at a temperature of 1700 C, in the subbituminous type it has higher temperature 3130 C and longer burn test at 30 minutes.

This paper demonstrates how the combustion of fossil fuels for transport purpose might cause health implications. Based on an original case study [i.e. the Hubei province in China, the epicentre of the coronavirus disease-2019 (COVID-19) pandemic], we collected data on atmospheric pollutants (PM2.5, PM10and CO2) and economic growth (GDP), along with daily series on COVID-19 indicators (cases, resuscitations and deaths). Then, we adopted an innovative Machine Learning approach, applying a new image Neural Networks model to investigate the causal relationships among economic, atmospheric and COVID-19 indicators. Empirical findings emphasise that any change in economic activity is found to substantially affect the dynamic levels of PM2.5, PM10and CO2which, in turn, generates significant variations in the spread of the COVID-19 epidemic and its associated lethality. As a robustness check, the conduction of an optimisation algorithm further corroborates previous results.

Biogas is an alternative energy source that could solve two problems at once, the problem of environmentally friendly energy needs and the problem of waste treatment. One of the sources of biogas is obtained from anaerobic bacterial fermentation of cow dung waste. The biogas fermentation process produces impurities such as carbon dioxide (CO2) as a combustion inhibitor. Carbon dioxide will inhibit the combustion reaction, resulting in incomplete combustion. The biogas purification process is needed to reduce the amount of carbon dioxide in the biogas. The purification process is carried out using an absorbent compound of calcium oxide (CaO) to bind carbon dioxide contained in the biogas. Thus, the purpose of this study was to analyze the effect of the biogas purification process using calcium oxide on the characteristics of the diffusion flame produced by combustion. The research was conducted experimentally using the physicochemical-absorption method of purification by flowing biogas through a purificator device that contained a purification solution. After passing through the purification solution, the biogas was regulated at a fuel flow rate of 3 liters/min and then proceed to the bunsen burner. The results showed that purification affected increasing the characteristics of the diffusion flame combustion due to the reduced amount of carbon dioxide in the biogas. This is indicated by increasing the purification molarity, it also increases the flame speed of combustion and the flame angle, as well as a decrease in the flame height.

The algae-based technology has a positive effect on the treatment of biogas slurry and the purification of biogas, while vitamin B12 (VB12) is one of the important regulatory substances in the algae-based cultivation system. In this study, different concentrations of VB12 were used in three microalgal treatment technologies to assess their effect on simultaneous removal of nutrients from biogas slurry and removal of CO2 from raw biogas. Results showed that Chlorella vulgaris exhibited higher growth rate, mean daily productivity, chlorophyll a content, carbonic anhydrase activity and better photosynthetic properties when co-cultivated with Ganoderma lucidum, rather than when co-cultivated with activated sludge or under mono-cultivation. Maximum mean chemical oxygen demand, total nitrogen, total phosphorus and CO2 removal efficiencies were found to be 84.29 ± 8.28%, 83.27 ± 8.14%, 85.27 ± 8.46% and 65.71 ± 6.35%, respectively when microalgae were co-cultivated with Ganoderma lucidum under 100 ng L-1 of VB12. This study shows the potential of microalgae and fungi co-cultivation supplemented with VB12 for the simultaneous upgradation of biogas production as well as for the purification of biogas slurry.

Biogas produced from anaerobic digestion of organic waste is composed of methane (CH4) and carbon dioxide (CO2) as the major constituents with trace amounts of other components like water vapor, hydrogen sulfide, ammonia, and nitrogen. Scrubbing of CO2 is essential for upgradation of biogas, which increases the calorific value of the treated gas and enhances its efficiency for power production and cooking. This study was conducted to investigate and compare the effects of different concentrations of KOH (0.1, 0.3, 0.5, 0.7, and 1.0 M) and natural base ash solutions prepared from different parts of banana plant, viz. banana pseudostem (BPS), Musa balbisiana Peel (MBP), and Musa acuminata Peel (MAP) for scrubbing of CO2 from biogas. The methane content of the untreated biogas analyzed in a gas chromatograph was found to be 56.9%. The scrubber with natural base solution from MBP could enrich the methane content in biogas from 56.9% to 86.3% followed by MAP (78.4%) and BPS (76.8%). The experiments revealed that banana peel ash base solutions have nearly equivalent potential as KOH for CO2 absorption from biogas. The highest CO2 absorption of ~ 68% was achieved with MBP with saturation time of 19 min approximately at a flow rate of 200 ml/min. The study also indicated that CO2 absorption by different natural as well as chemical base solvents is transient and has to be replenished after saturation. Natural bases have the added advantage of being easily available, cheap production method, environment friendly and require no treatment for disposal.

Microalgae are unicellular photosynthetic organisms capable of producing high-value metabolites like carbohydrates, lipids, proteins, polyunsaturated fatty acids, vitamins, pigments, and other high-value metabolites. Microalgal biomass gained more interest for the production of nutraceuticals, pharmaceuticals, therapeutics, food supplements, feed, biofuel, bio-fertilizers, etc. due to its high lipid and other high-value metabolite content. Microalgal biomass has the potential to convert trapped solar energy to organic materials and potential metabolites of nutraceutical and industrial interest. They have higher efficiency to fix carbon dioxide (CO2) and subsequently convert it into biomass and compounds of potential interest. However, to make microalgae a potential industrial candidate, cost-effective cultivation systems and harvesting methods for increasing biomass yield and reducing the cost of downstream processing have become extremely urgent and important. In this review, the current development in different microalgal cultivation systems and harvesting methods has been discussed.

The aim of the current research was the isolation, characterization and identification of native microbial strains from waste generated in the processing of sheep wool and alpaca fiber, for the production of biogas inside a dry anaerobic digestion (DAD) reactor in order to degrade solid waste coming from the textile industry.In total 52 bacterial strains and 15 fungal strains were isolated in anaerobic conditions from samples taken from solid waste produced in the processing of alpaca fiber and sheep wool by the Inca Tops textile company.Both the biogas composition and production were evaluated in 3 DAD reactors with different inocula: bacteria, fungi and microbial consortia; with the consortium inoculated reactor having the best production rate and best biogas attributes obtaining 33.38 %, 6 %, 1.44 % and 0.89 ppm methane, carbon dioxide, oxygen, and hydrogen sulfide respectively

The research aims to design and fabricate prototype of a bio-filter which used to process the emissions of CO and Co2.That are mainly generated from the combustion of coal, oil and natural gas. These are main energy resources in our daily life which used in different food activities as food factories and charcoal grills. The prototype consists of cylinder steel with two covers, two tubes welded on the outer face of each cover and candle of filter. Candl was consisting of two circle walls and the space between two walls was 2cm In the experiments were conducted on four cases from bio materials as follows:- 1- grinded ficus green leaves 2- grinded green leaves after drying 3- dry sawdust, 4-Wet sawdust. Measurements were done at five times after 2, 4, 6, 8, and 10 min. from starting experiments. The moisture contents was measured to the agricultural residues (bio-materials) before and after experiments. Chemical analysis was done on the bio-material to measure the Co , Co2 befor and after experiments. Also, Co , Co2 were measured in the air befor input prototype and after output. The results with bio.filter were: - with green leaves: Co2 ratio decreased to 18% ,Co decreased to 2 %. And absorb of C ratio by green leaves was 4.5%. - with dry leaves: Co2 decreased to 15 %, Co ratio didn’t change and absorb of C ratio by dry leaves was 0.07%. - with wet sawdust: Co2 decreased 0.03% and Co ratio didn’t change. - with dry sawdust: Co2 and Co didn’t change. the finel conclution was the ficus green leaves is the best bio.materials to use with bio-filter.

CO2 capture is necessary to decarbonize natural gas combined cycles (NGCC) that will be used to provide power when renewable power is unavailable. The PZAS™ (Piperazine (PZ) with the Advanced Stripper) second generation capture technology has been successfully tested with coal-fired flue gas. This paper reports reliable testing of PZAS at NGCC conditions for 2000 hours in a 0.66 m ID absorber at the National Carbon Capture Center (NCCC). Coal-fired flue gas diluted with air entered the absorber at 77 oC. 5 m PZ was regenerated by the Advanced Stripper with 2.45 gJ steam/tonne CO2 at 6.2 bara. With 40 feet of packing and pump-around intercooling the absorber provided 90–95% CO¬2¬ removal with a rich loading of 0.40–0.41 mol CO2/mol N. The apparent rate of PZ oxidation was 0.3 kg/tonne CO2. The water wash reduced PZ emission to less than 1 ppm. In the last 400 hours of testing, carbon treating clarified the solvent color, reduced ammonia production by as much as 40%, and improved both absorber and stripper performance. Testing with coupons showed that 304 SS had an acceptable corrosion rate even at the severe conditions of the stripper at 150 oC.

Since the 20th century, plastics that are widely being used in general life and industries are causing enormous plastic waste problems since improperly discarded plastics barely degrade and decompose. Thus, the demand for polyhydroxyalkanoates (PHAs), biodegradable polymers with material properties similar to conventional petroleum-based plastics, has been increased so far. The microbial production of PHAs is an environment-friendly solution for the current plastic crisis, however, the carbon sources for the microbial PHA production is a crucial factor to be considered in terms of carbon-neutrality. One‑carbon (C1) resources, such as methane, carbon monoxide, and carbon dioxide, are greenhouse gases and are abundantly found in nature and industry. C1 resources as the carbon sources for PHA production have a completely closed carbon loop with much advances; i) fast carbon circulation with direct bioconversion process and ii) simple fermentation procedure without sterilization as non-preferable nutrients. This review discusses the biosynthesis of PHAs based on C1 resource utilization by wild-type and metabolically engineered microbial host strains via biorefinery processes.

The concept of syngas biomethanation is attractive, however, it still needs improvement in optimizing the operational conditions. In the present study, syngas fermentations under different carbon monoxide (CO), carbon dioxide (CO2) and hydrogen (H2) compositions were conducted under two different biomass-gas ratio (BGR) systems. The results showed that high BGR enhanced the CO consumption rate, achieving a 60% enhancement with CO as the sole substrate. Stoichiometric H2 addition could successfully convert all the CO and CO2 to pure methane, however, higher H2 partial pressure might decline the CO consumption due to pH inhibition from consumption of bicarbonate. Microbial analysis showed different syngas composition could affect the bacteria community, while, archaea community was only slightly affected with Methanothermobacter as the dominant methanogen. This study provided strategy for efficient syngas biomethanation and deeper insight into effect of H2 addition on CO conversion under different BGR systems.

Tank bio-oxidation is a biohydrometallurgical technology widely used for metal recovery from sulfide concentrates. Since carbon availability is one of the key factors affecting microbial communities, it may also determine the rate of sulfide concentrate bio-oxidation. The goal of the present work was to evaluate the effect of carbon sources on the bio-oxidation of the concentrate containing 56% pyrite and 14% arsenopyrite at different temperatures (40 and 50 °C) in stirred tank reactors. CO2 was supplied into the pulp of the first reactor (about 0.01 L/min) and 0.02% (w/v) molasses was added to the pulp of the second one, and no additional carbon sources were used in the control tests. At 40 °C, 77% of pyrite and 98% of arsenopyrite were oxidized in the first reactor, in the second one, 73% of pyrite and 98% of arsenopyrite were oxidized, while in the control reactor, 27% pyrite and 93% arsenopyrite were oxidized. At 50 °C, in the first reactor, 94% of pyrite and 99% of arsenopyrite were oxidized, in the second one, 21% of pyrite and 94% of arsenopyrite were oxidized, while in the control reactor, 10% pyrite and 92% arsenopyrite were oxidized. The analysis of the microbial populations in the reactors revealed differences in the total number of microorganisms and their species composition. Thus, it was shown that the use of various carbon sources made it possible to increase the intensity of the concentrate bio-oxidation, since it affected microbial populations performing the process.

This paper presents an analysis of selected parameters of biogas, formed as a result of methane fermentation, during the start-up of a biogas installation, using water, liquid manure, corn silage and inoculated sludge as substrates. Moreover, the dependencies between the type and amount of the supplied substrate and the obtained parameters of biogas and fermentation mass are presented and explained. During 59 days after the start of the biogas plant operation, the methane content increased to a maximum of about 62%. Finally, after about 80 days, the methane content stabilized at a constant level of about 55%. CO2 content increased from about 6% (day 32) to about 46% (day 84), with a clear linear correlation between carbon dioxide and methane content. Oxygen content decreased from about 18% (day 32) to about 0.3% (day 84) as the resulting gases displaced air from the reactor, and there was also a linear correlation between oxygen and methane content. The hydrogen sulfide content decreased from about 76 ppm (day 32) to about 0 ppm (day 47), after which, in a clear power correlation to the methane content, it maximally increased to 890 ppm (day 61). However, for the sake of safe engine operation, the desulfurization plant was started on day 63, which resulted in a H2S concentration below 50 ppm on day 74 of the experiment. The final hydrogen sulfide content was 9 ppm on day 84 of the biogas plant start-up.

The problem posed by the silicon interference in bamboo pulp black liquor has been troubling bamboo pulp mills as well as hindering the development of non-wood pulp mills. Silica is separated from bamboo pulp black liquor by acid precipitation, accompanied by the sediment of lignin, which is disadvantageous to alkali recovery system. The amount of carboxylate increases through the oxidation of lignin, and the solubility of lignin increases. So the lignin precipitation and the removal of silica can be quantified by the combination of acidification and light oxidation. For solving the problem, we separate the silicon in the black liquor through oxygen oxidation and carbon dioxide acidification without affecting the stability of the alkali recovery system. TG, combustion calorific value and visible light absorption are tested after oxidation and acidification. Finally, by comparing with the mature pulp black liquid alkali recovery system, it is concluded that when taking economic capital into consideration, oxidizing to pH 12.45(at 80 °C) and acidifying to pH 10 (at 50 °C) are suitable for our goal. In this case, the silicon removal rate reaches 76.41 wt%; the amount of separated lignin is 17.58 wt% and the calorific value loss of black liquor reaches 26.47%.

The long-term effectiveness concern of municipal solid waste incineration (MSWI) fly ash (FA) disposal has been placed more emphatic recently, however, few studies worked on the control of leaching risk of heavy metals under the long-term stability. In this study, the leaching properties and risk assessment of two representative solidified/stabilized (S/S) FA wastes, i.e., sodium dithiocarbamate (DTC) chelator treated and Portland cement + chelator combining treated, were evaluated by a long-term cycles assessment method which coupled multifaceted environmental stresses (e.g., freezing-thawing, drying-wetting, accelerated carbonation). The results showed that the cement/chelator had a better long-term stability and exhibited ~55% lower cumulative overall pollution toxicity index (OPTI) than chelator treatment after the test, which was always rated as “low risk” during the cycles. In addition, the cement/chelator exhibited ~23.3% smaller cumulative mass release rate than the chelator treatment after 6 cycles and restrained the transformation of Pb and Cd from stable states to removable fractions, which attributes to its great erosion resistance and compact pore structure. Under the cumulative external factors and carbon dioxide attacks, the decalcification of hydrate products (e.g., C-S-H, hydrocalumite), as well as deterioration of pore structure are the critical factors increasing the local erosion, cracking and heavy metals release. Thus, the optimization of S/S waste microstructure (e.g., enhancing binder system) and landfill site conditions (e.g., reducing rainfall impact) could be propitious to the S/S waste risk control and management.

The rise of atmospheric carbon dioxide (CO2) concentration due to extensive anthropogenic activity besides rapid exhaustion of non-renewable energy sources demands evolution of clean and ecofriendly alternative fuel source. Recently, lipid rich microalgal biomass is being considerably researched for generation of biodiesel conversely, the expenses incurred on production of microalgal biomass is a substantial obstacle. Almost 80 % of the production cost is generated from the cultivation medium which majorly consists of carbon, nitrogen and phosphate. CO2 absorption by means of aqueous amine solvents is known to be a mature technology and could be integrated with microalgal cultivation unit for efficient utilization of the captured CO2. In this current investigation, piperazine (PZ) promoted aqueous blend of methyldiethanolamine (MDEA) having mass percentage ratio of (8/22 wt%) was used a CO2 capturing agent and then the captured CO2 was utilized as an inorganic carbon source for growing Chlorella sorokiniana BTA 9031 for biodiesel production. The CO2 absorption rate was governed by series of process variables namely, absorption temperature, initial CO2 concentration, solvent flow rate, gas flow rate and the optimal conditions were 315 K, 15 kPa, 3.6 × 10−4 m3 min−1 and 4 × 10−3 m3 min−1 respectively. The highest biomass strength of Chlorella sorokiniana BTA 9031 was observed to be 1.20 ± 0.028 g L−1. The fatty acid methyl esters (FAME) profile was determined after acid transesterification of the extracted microalgal lipids. It was observed to contain fatty acids suitable for biodiesel production.

This work aimed to investigate the inactivation of Legionella in aqueous media using high-pressure carbon dioxide (HPCD). Both discontinuous and continuous operations were tested. During batch treatments, the increased pressure improved the inactivation of Legionella, probably due to better dispersion and dissolution of the HPCD in the aqueous medium. Inactivation also increased with temperature. After 10 min and 26 °C it was not necessary to exceed 20 MPa, where reductions higher than 4.2 log were reached. At 10 MPa, reductions higher than 3.1 log were reached, good enough for real aqueous environments, which rarely exceed 102 CFU mL−1. Total inactivation was reached at 38 °C at all pressures. For a given temperature, treatment with HPCD was always much more effective than thermal treatment. During continuous treatments, a contact time of 1 min at 28 °C and 10 MPa were enough for the total inactivation of Legionella in co-current flow with a CO2/suspension mass ratio of 1. Simulation with Aspen Plus® revealed that depressurization of the sterile water to remove gaseous CO2 cooled it sufficiently to be used as a cooling service.

Reducing anthropogenic CO2 emissions has become a primary environmental concern for the present society, making the development of energy-efficient, net-negative CO2 emitting technology paramount. Here, the Chemical looping deoxygenated gasification (CLDG) process is experimentally conducted to demonstrate the crucial role of deoxygenation on syngas refinement and CO2 utilization via Fe0 ↔ Fe3+ looping. A reduction of 0.324 g CO2 per gram pine wood biomass gasified is achieved, a 288% reduction in CO2 emissions compared with that of biomass conversion without deoxygenation. The superiority of CLDG can be also reflected in syngas yields increased by 16.37% and a CO2 concentration decreased by 44.16%. Results from the heat balance calculation indicate that both the gasifier and the regenerator are endothermic, which cannot achieve the auto-thermal operation of CLDG, thus requires an extra energy supply source. Density functional theory calculations elucidate that the active site of CO2 adsorption is located at the three-phase interface of CaO(1 1 1), Fe(1 1 0), and amorphous carbon (AC). It is anticipated that CLDG has the potential to serve as an effective measure for reducing CO2 emissions while promoting syngas yield and quality.

As a promising wastewater treatment technology, little is known about whether the greenhouse gas CO2 can be applied for microalgal-bacterial granular sludge (MBGS) process. This article applied CO2 for improving MBGS process. It was found that the physical structure of MBGS with no CO2 addition appeared to have a trend to be loose and disintegrated, with a sludge volume index at 5 min (SVI5) of over 150 mL/g and an average pore size of 35 nm in 60 d operation. However, CO2 could maintain the compact and integrated structure of MBGS with a SVI5 lower than 50 mL/g and an average pore size ranging from 10 to 13 nm. CO2 could enhance the production of extracellular polysaccharides and aromatic protein, thus favoring the granular stability of MBGS. CO2 could change the aqueous environment, e.g. lowering the pH values, which resulted in different microbial communities as well as metabolic potentials of MBGS. As for the reactor performance, CO2 could significantly improve the removals of organics and phosphorus, evidenced by the enhancement of genes encoding acetate-CoA ligase and ATPase, respectively. Although the mass ratio of algae to bacteria was elevated by CO2 addition, the ammonia removal related enzymes of glutamate dehydrogenase and glutamine synthetase could be negatively and positively impacted by CO2, respectively. Mass balance analysis of carbon indicated that CO2 could provide additional carbon source as well as enhance the buffering capacity for the MBGS system. Further estimations suggested that the MBGS process could achieve a carbon-negative objective for municipal wastewater treatment by supplying CO2 as additional carbon source. Hence, CO2 supply for MBGS process in municipal wastewater treatment can be deemed as a two-birds-one-stone strategy, i.e. maintaining the granular stability and eliminating the carbon emission. This article can advance our basic knowledge on MBGS process towards environment-sustainable wastewater treatment.

Composting and vermicomposting generate a valuable product rich in plant nutrients and at the same time, reduce environmental pollution. However, along with these processes and in relation to the metabolism of the microorganism and the worms present in the vermicomposting, CO2 is emitted to the atmosphere, contributing to the greenhouse effect. Taking these issues into account, different masses of fly ash were used to study the control of the CO2 of the gas coming from a vermicomposting process and to evaluate the possibility of using the adsorbent as fertilizer in the culture of lettuce Lactuca sativa. Along the vermicomposting process, an increase in the concentration of CO2 emissions was observed, with a maximum level of emission at the day 20 of the process and an average of 770 mg/L in air. After the adsorption process, the CO2 concentration was lower due to the effect of the fly ash that was able to trap the emitted gas. The percentage of CO2 adsorption shows maximum values of 55.5, 58.1 and 63.8% with 0.5, 1 and 1.5 kg of fly ash, respectively. The CO2 uptake capacities of the different loads of fly ash used were 3.39, 7.03 and 6.84 mmol CO2/g sorbent with 0.5, 1 and 1.5 kg of fly ash, respectively. After five weeks of sowing L. sativa, it was observed that when no fly ash was used in the soil, the length of the stem was 10.2 cm. Then, the length of the stem was 22 cm, and 16 cm when 10% of fly ash was applied and not applied in the adsorption process, getting a significant correlation between the load of fly ash and the length of the stem. The r when fly ash was used in the adsorption process was 0.9817 and 0.9811 when no ash fly was used in the process.

In this study, experimental and mathematical studies were carried out to investigate heavy oil production performance using the carbon dioxide (CO2) huff-n-puff process, as well as the potential of CO2 storage in abundant reservoirs. Five experiments were conducted under different injection pressures and different pressure depletion rates. The components in the produced heavy oil were measured using a gas chromatography-mass spectrometry system to investigate the influence of CO2 extraction under different injection pressures in different cycles. The experimental results indicate that (a) heavy oil recovery factor increases with increasing injection pressure. (b) CO2 extraction of the light/medium components in heavy oil affect heavy oil production. (c) With different pressure depletion rates, an optimized pressure depletion rate can be identified as 4 kPa/min. And (d) the relationship between heavy oil and gas production can be predicted using the developed equation with high agreements. Mathematically, the potential of CO2 storage and CO2 capacity were calculated, and the investigations show that the most significant influences on CO2 capacity are CO2 stored in the available space and dissolving into the remaining heavy oil. An objective function was developed to optimize the heavy oil recovery factor and the CO2 storage factor in the CO2 huff-n-puff process. The influences of weights between heavy oil production and CO2 storage were investigated, and the optimized case with the same weight (0.5) was studied.

Summary: Haematococcus pluvialis, the richest bioresource for natural astaxanthin, encounters a challenge of achieving high growth rate when it comes to mass biomass production. Based on the substrate consumption model and Redfield ratio, rapid algae growth benefits from a proper carbon supply. However, the conventional cultivation schemes with limited carbon dioxide (CO2) supply and inefficient carbon mass transfer could have constrained the carbon capture and growing ability of H. pluvialis. We hypothesize that optimal H. pluvialis growth improvement may be achieved by efficient CO2 supply. Here, in this study, we first identified the carbon consumption of H. pluvialis during exponential growth. Then, a novel microbubble-driven photobioreactor (MDPBR) was designed to satisfy the carbon demand. The novel microbubble photobioreactor improves the CO2 supply by reducing bubble size, significantly elevating the CO2 mass transfer. With only 0.05 L min−1 of gas flow rate, higher cell growth rate (0.49 d−1) has been achieved in MDPBR.

In this work, it is evaluated the fixation of carbon dioxide using the alkali generated in the chloralkaline process, as a new way to face the treatment of highly saline wastewater, in which it is aimed not to separate the wastewater into concentrated and diluted streams but to recover value-added products (VAPs) while contributing to minimize the carbon fingerprint of other processes. The electrolytic process is combined with a reactive absorption and with a crystallization, demonstrating the formation of pure nahcolite, hypochlorite (or chlorine) and hydrogen from the waste. Carbon dioxide is captured with a current efficiency over 90% and the energy required is around 0.65 kWh kg−1, which is very promising from the view point of sustainability, considering that the system can be easily powered with green energies.

Conventional leather dyeing consumes high amounts of dyes and increases pollution of tannery wastewater. We have focused on the reduction of dyestuff and the avoidance of water and additional chemicals for the colorization of leather. Waterless leather dyeing with supercritical CO2 as solvent for the dye 1-(methylamino)anthraquinone was performed in a technical scale autoclave. The intensity and uniformity of the dyed leathers was assessed using spectroscopic color measurements. The rub fastness was assessed according to DIN EN ISO 11640. In the result, waterless dyeing at 100 bar and 40 °C leads to uniform, intensive colorizations of the leather surface at a usage of 0.1 g of dye per square foot of leather. The dyed leathers achieve the highest rub fastness grades. The exhaustion of dyestuff is almost 100%. The waterless dyeing process offers potential to save significant amounts of dyestuff and reduce wastewater emissions by 100%.

The present research work shows the effect on the carbonation of Portland cement-based mortars (PC) with the addition of green materials, specifically residues from two groups: agricultural and industrial wastes, and minerals and fibres. These materials have the purpose of helping with the waste disposal, recycling, and improving the durability of concrete structures. The specimens used for the research were elaborated with CPC 30R RS, according to the Mexican standard NMX-C-414, which is equivalent to the international ASTM C150. The aggregates were taken from the rivers Lerma and Huajumbaro, in the State of Michoacan, Mexico, and the water/cement relation was 1:1 in weight. The carbonation analyses were performed with cylinder specimens in an accelerated carbonation test chamber with conditions of 65 +/− 5% of humidity and 25 +/− 2 °C temperature. The results showed that depending on the PC substitutions, the carbonation front advance of the specimens can increase or decrease. It is highlighted that the charcoal ashes, blast-furnace slags, and natural perlite helped to reduce the carbonation advance compared to the control samples, consequently, they contributed to the durability of concrete structures. Conversely, the sugarcane bagasse ash, brick manufacturing ash, bottom ash, coal, expanded perlite, metakaolin, and opuntia ficus-indica dehydrated fibres additions increased the velocity of carbonation front, helping with the sequestration of greenhouse gases, such as CO2, and reducing environmental pollution.

The full utilization of carbohydrates in lignocellulosic biomass is essential for an efficient biorefining process. In this study, co-fermentation was performed for processing ethanol and succinic from sugarcane bagasse. By optimizing the co-fermentation conditions, nutrition and feeding strategies, a novel process was developed to make full utilization of the glucose and xylose in the hydrolysate of sugarcane bagasse. The achieved concentrations of succinic acid and ethanol reached to 22.1 and 22.0 g/L, respectively, and could realize the conversion of 100 g SCB raw material into 8.6 g ethanol and 8.7 g succinic acid. It is worth mentioning that the CO2 released from S. cerevisiae in co-fermentation system was recycled by A. succinogenes to synthesize succinic acid, realized CO2 emission reduction in the process of lignocellulosic biomass biorefinery. This study provided a clue for efficient biorefinery of lignocellulosic biomass and reduction greenhouse gas emissions.

The most common method to concentrate apatite from carbonate phosphate ore is reverse configuration using fatty acids as collectors and inorganic acids as apatite depressants, such as H2SO4 and H3PO4. This work evaluates the process based on the separation between apatite and calcite by flotation, in bench and pilot scale, using carbon dioxide injected through the bubble generation system with the use of saponified coconut fatty acid as a collector, as an alternative to the inorganic acids as apatite depressants in the process circuit developed to treat a uranium-carbonate phosphate ore (Santa Quiteria, Brazil). Moreover, the discharge of natural slimes only was evaluated, without the removal of the grinding slimes, which is not observed in apatite flotation plants for weathered material, where the removal of both kinds of slimes is necessary. The circuit proposed in this study provided significant gains in P2O5 recovery. In calcite flotation studies using carbon dioxide, in RG/CL/RCL mechanical cell circuit configuration, considering the overall performance obtained (grinding product + natural fines), the overall P2O5 recovery was approximately 91% and the P2O5, SiO2 and Al2O3 grades were 29%, 11% and 13%, respectively. The results obtained in this study indicated that the process circuit proposed by discharging only natural slimes increases the global P2O5 recovery, and the flotation process based on the injection of carbon dioxide is a potential alternative to concentrate apatite from the Santa Quiteria ore. Furthermore, previous studies have indicated that the use of carbon dioxide instead of inorganic acids as apatite depressants causes less ion accumulation in the process water, which is a major issue mainly in areas with scarce water supply such as the Santa Quiteria region.

For composting of garden waste, particle size is an important factor for efficient degradation of lignocellulose compounds. The present study is aimed at investigating how particle size effects selected physicochemical and biological parameters such as temperature, moisture, total volatile solids lignin degradation, coliform reduction, germination index, and carbon dioxide evolution during the composting of garden waste. The garden waste was shredded using a shredder into different particle size namely R1 (0.5-1.5cm), R2 (1.5-3.0cm), R3 (3.0-4.5cm) and R4 (4.5-7.5 cm). The feedstock was fed into rotary drums for 45 days composting period. The temperature rose to the thermophilic phase within 48 hours in all the drums and continued for R1 (7 days), R2 (8 days), R3 (4 days), and R4 (3 days). Moisture content reduction observed was R1 (23.4%), R2 (22.7%), R3 (21.7%) and R4 (20.8%). Total volatile solids reduction was 29.10, 31.20, 24.23, and 17.12 %, CO2 evolution rate was 4.92, 4.14, 6.18 and 8.16 mg/gVS/d, C/N ratio was 16.91, 15.05, 18.13 and 20.99, germination index was 92.00, 94.12, 85.21, and 81.20 in R1, R2, R3, and R4 reactor respectively after end of the composting period. The reduction of hemicellulose, cellulose, and lignin was highest in the R2 drum and lowest in R4. The percentage reduction of coliforms was also found to be highest in R2. As per the analytical hierarchy process, the performance of reactors was observed in the following trend, R2>R1>R3>R4. Particle size range 1.5-3.0 cm diameter showed optimum size for efficient composting of garden waste.

Catalytic combustion method was proposed in this study for the continuous treatment of the biodiesel wastewater over the Pt/Al2O3@cordierite catalyst. The components of biodiesel wastewater and the Pt-based catalyst were analyzed. Excellent catalyst activity and stability were observed during the wastewater treatment. The chemical oxygen demand (COD) of biodiesel wastewater was significantly reduced through the catalytic combustion, with the COD value still lower than 500 mg/L after 200 h continuous run. No organic gas was found in the gas product and all organic compounds removed were converted to carbon dioxide and water.

In-situ hydrogen biomethanation is a promising technology to upgrade biogas. The efficiency of biomethanation relies on various parameters, e.g. gas supplement, temperature and hydrogenotrophic methanogens. Therefore, it is important to investigate the characteristics of in-situ hydrogen biomethanation under different conditions. In this study, two experiments (lasted for 91 days and 105 days) were carried out to investigate the impacts of feeding gas and operating conditions on performances of reactors and microorganisms. During the whole experiment, no obvious fluctuation of pH and limitation of gas–liquid mass transfer were found. Results showed that the hydrogenotrophic methanogenesis performed better at thermophilic condition, while the dominant archaea genera at mesophilic and thermophilic temperature was determined to be Methanobacterium and Methanothermobacter, respectively. The highest CH4 content (greater than 90%) was obtained when H2 and CO2 was feeding at ratio of 4:1 and Methanothermobacter was dominant. These findings can provide useful information for promoting hydrogen biomethanation.

Even though lab-scale experimental studies have shown the technological potential of the electrochemical conversion of carbon dioxide (CO2) to formic acid (FA), there are few studies that have evaluated the environmental feasibility of such a conversion. This study develops an integrated process consisting of a three-compartment cell reaction system and a pressure-swing distillation separation system to produce commercial-grade FA from CO2. A total of 18 environment impact categories, including climate change and fossil depletion, are estimated for the process configurations on a system level. The electrochemical process has a 12.4–99.7% reduced environmental impact except for terrestrial ecotoxicity, compared to the conventional FA production process using carbon monoxide obtained from fossil fuels. In 17 categories, except that of ionizing radiation, electricity was identified as a major factor (17–97%) affecting the environment. A reduction in the electricity requirements or supply of renewable electricity, such as hydropower, will enable more environment friendly FA production from CO2.