Biogas Research Articles

Clear and Present Dangers: The Multiple Health Hazards of Volcanic Eruptions.

Clear and Present Dangers: The Multiple Health Hazards of Volcanic Eruptions.

Regulatory Support for Biosequestration Projects in Australia: A Useful Model for Transition to Net-Zero Emissions?

This paper considers the effectiveness of Australian regulatory measures to support storing atmospheric carbon in plants and organic matter in soils (biosequestration), a central element of the Australian greenhouse gas (GHG) emission policy through the Emissions Reduction Fund (ERF). Eligible methodologies under the ERF are broader than those in other jurisdictions. Hence Australian experience may have international application. The functionality of Australian regulation to achieve GHG emissions reduction is considered, focusing on provisions relating to additionality, permanence, monitoring, reporting and verification of emissions bio-sequestration. This analysis is conducted by reviewing key publications by research organisations, academics, government departments, industry organisations, environmental organisations and private sector consultancies. While the integrity of Australian biosequestration offsets is generally well regarded, persistent issues have been identified with regard to the additionality of avoided deforestation methane capture in intensive agriculture and landfill gas projects. The proportion of Australian emissions represented by existing biosequestration offset projects is deficient. These issues must be addressed in order to scale up biosequestration projects as an effective element of Australia's net-zero emissions strategy. It can best be achieved by tightening Safeguard Mechanism baselines to drive demand for carbon credits and funding the Clean Energy Regulator to implement effective, independent MRV. Ongoing regulatory reform will be necessary to address such issues as they arise in the course of the implementation of specific methodologies. Nonetheless, ongoing emissions risks relating to biosequestration and other offset projects can only be adequately addressed by complementary policy to reduce emissions at the source.

Co-pyrolysis of municipal sewage sludge and microalgae Chlorella Vulgaris: Products’ optimization; thermo-kinetic study, and ANN modeling

Co-pyrolysis of microalgaeChlorella vulgaris(MCV) and municipal sewage sludge (MSS) was performed in a fixed-bed reactor to explore the influence of temperature (400–600 °C), mixing ratio (MCV/MSS = 0–1), and Argon flow rate of 0.20 to 0.80 L/min on pyrolysis products. The process was optimized using RSM to maximize bio-oil (BIO), minimize biochar (BIC), and biogas (BIG) yields. According to the ANOVA results, the mixing ratio has the most remarkable impact on BIO yield, and temperature has the highest influence on both BIC and BIG efficiency. By using numerical optimization, the optimum values of reaction parameters were T = 520 °C, mixing ratio (MCV/MSS) = 0.82, and Argon flow rate of 0.55 L/min. The third, second, and third-order of chemical reaction models can fit the pure MSS, MCV, and mix pyrolysis utilizing the Coats-Redfern technique, respectively. Also, master plots approaches were used to identify dominant reaction mechanisms. The values of the Eα calculated from non-model fitting methods for MSS, MCV, and co-pyrolysis are obtained in the domain of 79.19–125.59, 182.41–194.73, and 149.55–216.61 kJ/mol, in that order. The presence of the synergetic and inhibitive influences generated by the co-pyrolysis of MSS and MCV has been demonstrated by the improved and reduced weight loss rate, respectively. Furthermore, artificial neural network (ANN) models with the architectures (3*8*3) and (2*8*1) were built to simulate and predict pyrolysis yields and the thermal decomposition of individual and co-pyrolysis process, demonstrated a strong agreement between the actual data and predicted data (R2 ⩾ 0.999) are considerably closer to 1.

Enhanced biological phosphorus removal from wastewater by current stimulation coupled with anaerobic digestion

The integrated wastewater discharge standard for phosphorus has become increasingly strict. In this study, a synergetic current stimulation system coupled with anaerobic digestion was used to enhance phosphorus removal from wastewater. The effects of current intensity, pH, and methane (CH4) synthesis on phosphorus removal were investigated. As direct current was supplied to an anaerobic bioreactor, the removal of sewage total phosphorus was significantly enhanced. The conditions of weak acid and low negative oxidation-reduction potential facilitated the phosphorus removal from wastewater. The optimal parameters for the dephosphorisation process were a current intensity of 100 mA and a pH of 6.0. When the anaerobic digestion process was inhibited by the reagent 2-bromoethanesulphonic acid sodium (BES), abundant metabolic intermediates accumulated and methanogenesis clearly decreased. Affected by the current stimulation and the inhibition of CH4 synthesis, the formation of gaseous phosphine (PH3) was greatly improved, and then PH3 escaped from the digestion mixture after it was absorbed by microbial cells. The maximum PH3 content of the digestion gas was 41.8 mg m−3 in the reactor supplied with a current of 100 mA and BES addition of 10 mmol L−1, and the phosphorus removal in this digestion system reached 55.2% at 6 d; however, the removal in the conventional anaerobic digestion system was only 17.7% after the same amount of time. Finally, a pathway of enhanced anaerobic biological phosphorus removal was proposed to better understand the inherent synergistic mechanism.

Experimental assessment of the influences of liquid-solid-gas fuel blends on DI-CI engine behaviors

This study aims to deeply investigate the effects of the boron nanoparticles reinforced diesel fuel along with various biogas (BG) flow rates (0.5, 1, and 2 L/min) on the engine performance and emission characteristics of a diesel engine. The tests were carried out using a single-cylinder, four-stroke, direct injection, compression-ignition engine at a constant engine speed of 1500 rpm and under the varying engine loads from 2.5 to 10 Nm with gaps of 2.5 Nm. In the results, it is seen that EGT started to decrease in both the addition of boron nanoparticles and the addition of biogas compared to that of conventional diesel fuel (DF). EGT reduced by 8.6% for DF+Boron test fuel, 14.4% for DF+Boron+ 0.5 BG, 21% for DF+Boron+ 1 BG, and 23.4% for DF+Boron+ 2 BG. Compared to diesel fuel, CO, NOx, and HC emissions decreased with the addition of nanoparticles at all loads. However, as the amount of biogas increased, CO and HC emissions increased, but NOx emissions decreased. CO emission dropped by 22.2% for DF+Boron test fuel, however, increased to be 5.6%, 16.7%, and 36.1% for DF+Boron+ 0.5 BG, DF+Boron+ 1 BG, and DF+Boron+ 2 BG respectively. NOx emission reduced by 4.9%, 8.6%, 10.7%, and 14.8% for DF+Boron, DF+Boron+ 0.5 BG, DF+Boron+ 1 BG, and DF+Boron+ 2 BG respectively. In comparison to that of conventional DF, the brake specific fuel consumption (BSFC) value decreased by 8.42% for DF+Boron test fuel due to high energy content of nanoparticles, but it increased by 10.94% for DF+Boron+ 0.5 BG, 28.01% for DF+Boron+ 1 BG, and 60.2% for DF+Boron+ 2 BG. In addition, brake thermal efficiency BTE value increased by 8.04% for boron-added test fuel, but it declined by 9.41% for DF+Boron+ 0.5 BG, 19.38% for DF+Boron+ 1 BG, and 32.2% for DF+Boron+ 2 BG as compared to that of DF. In the conclusion, it is noticed that the engine characteristics have worsened by the introduction of biogas into the cylinder, but these worsened characteristics can be improved with the presence of boron nitride nanoparticles.

Robust Nickel-Based Metal-Organic Framework for Highly Efficient Methane Purification and Capture.

Developing energy-efficient alternatives for methane (CH4) purification from natural gas and methane capture of coal-mine gas is of great significance and challenge in the chemical industry. Herein, we report a robust nickel-based metal-organic framework (MOF), Ni-BPZ, featuring one-dimensional (1D) rhombic channels decorated with abundant pyrazole rings. Ni-BPZ exhibits excellent separation performance toward both C2H6/CH4 and CH4/N2 binary mixtures. The C2H6/CH4 selectivity of Ni-BPZ is high, up to 50.2, exceeding those of most MOF adsorbents reported, and it simultaneously possesses a remarkable C2H6 uptake of 2.46 mmol/g at 298 K and 0.1 bar. The CH4/N2 selectivity of Ni-BPZ reaches 6.6, and its high CH4 uptake is 1.56 mmol/g, which is also superior to most high-performance CH4 adsorbents. The molecular simulation reveals that the uniform 1D rhombic channels with abundant pyrazole rings provide a high density of potential adsorption sites for efficient C2H6/CH4 and CH4/N2 separations.

Catalytic production of low-carbon footprint sustainable natural gas

Natural gas is one of the foremost basic energy sources on earth. Although biological process appears as promising valorization routes to transfer biomass to sustainable methane, the recalcitrance of lignocellulosic biomass is the major limitation for the production of mixing gas to meet the natural gas composition of pipeline transportation. Here we develop a catalytic-drive approach to directly transfer solid biomass to bio-natural gas which can be suitable for the current infrastructure. A catalyst with Ni2Al3 alloy phase enables nearly complete conversion of various agricultural and forestry residues, the total carbon yield of gas products reaches up to 93% after several hours at relative low-temperature (300 degrees Celsius). And the catalyst shows powerful processing capability for the production of natural gas during thirty cycles. A low-carbon footprint is estimated by a preliminary life cycle assessment, especially for the low hydrogen pressure and non-fossil hydrogen, and technical economic analysis predicts that this process is an economically competitive production process.

A waste to energy technology for Enrichment of biomethane generation: A review on operating parameters, types of biodigesters, solar assisted heating systems, socio economic benefits and challenges

Anaerobic Digestion (AD) is one of the promising wastestoenergy (WtE) technologies that convert organic wastes to useful gaseous fuel (biogas). In this process methane is produced in the presence of methanogens (bacteria). The survival and activities of methanogens are based on several parameters such as pH, temperature, organic loading rate, types of biodigester. Moreover, these parameters influence the production of biogas in terms of yield and composition. Maintaining an appropriate temperaturefor AD is highly critical and energy intensive. This study reviews the various hybrid technologies assistedbio gas production schemes particularly from renewable energy sources. Also discuss the direct and indirect solar assisted bio-digester impacts and recommendation to improve its performance. In addition, the performance analysis Solar Photovoltaic (PV) and thermal collector assisted bio gas plants; besides their impact on the performance of anaerobic digesters. Since opportunities of solar energy are attractive, the effective utilization of the same is selected for the discussion. Besides, the various constraints that affect the yield and composition of biogas are also evaluated along with the current biogas technologies and the biodigesters. The environmental benefits, challenges and socio-economic factors are also discussed for the successful implementation of various technologies.

Implementation of the Romanian Mining Strategy 2017-2035, with special regard to pit coal: failure or abandonment?

Jiu Valley is currently the only national mining basin capable of producing pit coal. Romania has undergone an extensive industrial restructuring in the last 30 years, including mining, which has led to job losses, generated economic-social and environmental effects that have severely affected the quality of life of the inhabitants of mining communities. As a consequence, the Mining Strategy of Romania 2017 - 2035 was elaborated. The paper analyses the objectives, measures and actions provided in the strategy related to the exploitation of pit coal, putting, face to face, the true state of the mines and the inhabitants of Jiu Valley. 4 years after the elaboration of the Strategy, it is clear that it has not yet come to life: mines are still being closed, there is no clear vision for the sustainable development of mining communities, the mine closure process, the greening of post-closure areas is difficult or not at all, research (e.g. capture of methane from coal), development and innovation are not stimulated, the operation of coal-fired power plants is endangered, with major implications on the supply of inhabitants with heating and of domestic hot water -resulting in major discomfort for locals.

Do device that simulate methane capture equipment, as a mask located in the head of dairy cows affect their welfare?

The objective of this study was to determine if device that simulate methane capture equipment (DSMC) located in the frontal part of the head of dairy cows affect animal welfare using productive, behavioral, biochemical and physiological indicators. Twenty Holstein dairy cows were assigned to one of the two following treatments: cows with DSMC (CDSMC, n=10) and cows without methane capture devices (CC, n=10). Treatment did not affect neither milk production nor biochemical blood. The group CDSMC tended to ruminate less (P=0.06) and tended to eat more (P=0.08) frequently than the group CC. In conclusion, considering the data set, the welfare of the cows was not significantly affected by the use of DSMC located in their heads.

A robust two–dimensional layered metal–organic framework for efficient separation of methane from nitrogen

Selective capture and separation of methane (CH4) from nitrogen (N2) is a feasible approach to mitigate the effects of global warming and to improve the heating value of low-quality natural gas. However, the efficient separation of CH4/N2 is a challenge issue since their very close kinetic diameters and thermodynamic properties. In this work, a new type of two-dimensional (2D) layered metal–organic framework (MOF) with permanent rhomboid pore channels, denoted as Ni(4-DPDS)2CrO4, (4-DPDS = 4,4′-dipyridyldisulfide) was synthesized for the first time and used for CH4/N2 separation. This novel 2D MOF not only performs high stability as outstanding as or even better than previously reported 3D MOFs but also exhibits a relatively high CH4 adsorption capacity of 0.95 mmol/g. Ni(4-DPDS)2CrO4 has a high affinity towards CH4 with the highest reported Qst value of 28.4 kJ/mol as well as a high CH4/N2 selectivity of 7.3, which is comparable to the state-of-the-art MOF materials reported so far. DFT calculations revealed the energy favorable binding sites for methane molecules are located in the middle of the cavity decorated with CrO42- anion. Such an angular inorganic anion provides polar sites and makes guest–host interactions in close proximity, affording tight binding affinity. Breakthrough experiments and regenerability tests suggest it is a promising material in natural gas purification.

Methane separation and capture from nitrogen rich gases by selective adsorption in microporous Materials: A review

The rapid increase of natural gas consumption has induced imbalance between supply and demand of natural gas, and the continuous growth of methane emissions has severely exacerbated greenhouse effects and destroyed the atmospheric methane cycle. High-efficiency CH4 capture and separation from N2 rich gases has become a significant challenge for the recovery and utilization of low-grade natural gas and also industrial tail gas, which was important for sustainable energy and environment and attracted much attention from both researchers and engineers in recent years. This review provides an overview of selective separation techniques for N2 removal from natural gas including the benefits and drawbacks of these typical methods. Most notably, the review primarily outlines the progress of metal–organic frameworks, zeolites and activated carbons as superior adsorbents for separating CH4-N2 mixtures in worldwide laboratories, respectively, with an emphasis on the relationship of the pore size, surface chemistry and composition of adsorbents with the CH4/N2 selectivity and methane capacity. We also highlight the potential for the development of the new adsorbents with the best possible matching between aperture control and atomic-scale tuning of the composition for CH4 capture and separation from N2 rich gases, and indicate that the MOFs possess both the advantages of activated carbons and zeolites and will become one of the most promising candidates for high-efficiency CH4 separation from N2 rich gases in the future.

Green pathways for urea synthesis: A review from Australia's perspective

• Historical trend of the unsustainable fertilizer manufacturing should pursue greener pathways. • Green ammonia feedstock is critical but should be complemented with non-fossil CO 2 sources. • Three potential non-fossil-fuel CO 2 resources are discussed and evaluated in Australia. • Carbon-neutral CO 2 from biomass, renewable methane, or direct air capture may fit the criteria. • Proper energy management systems are essential for process synchronization and optimization. This paper discusses the status of the global fertilizer industry with a primary focus on Australian market. The conventional energy- and carbon-intensive ammonia production industry is taking serious steps in transforming to more environmentally benign pathways via utilising ‘green’ hydrogen (hydrogen production via water electrolysis powered by renewable energy) feedstock into their production process and utilizing more of the CO 2 by-product into downstream processes such as urea production. However, it is very challenging for ammonia and other fertilizer production routes to use ‘green’ pathway to completely decarbonize agriculture and food industry. Here, we argue that urea synthesis can only be considered as a ‘green’ technology if ammonia feedstock is produced via ‘green’ pathway and the CO 2 feedstock comes from non-fossil-fuel and carbon-neutral sources. Three possible resources for carbon-neutral CO 2 are identified and discussed within Australia's context: from biomass, renewable methane, and from direct air carbon capture (DAC). Each of these carbon-neutral CO 2 routes has many opportunities and challenges that may affect the cost of production, but the trajectory urea prices and growing market demand if supported by an adequate government regulatory framework would be able to make the ‘green’ urea production cost affordable. Achieving this goal however would require proper energy management systems to synchronize and optimize such a multi-player orientation for a common objective of maximizing the penetration of renewable sources at competitive costs. In this review, it is emphasized that this challenge could be addressed more effectively via a rigours intelligent energy network (IEN) by managing the dynamics of the supply and demand, integrating reliable storage systems, reclaiming the waste heat, and improving process efficiencies. Local ‘green’ urea production at competitive costs would help Australia realizing ambitions to become a leading green fertilizer and renewable energy exporter in the region.

An Investigation into Delineation and Contriving of Bio Gas with Special Reference to Household Use

The tremendous increase in global energy use during the 1980s has been mostly fuelled by fossil energy resources. In 2018, fossil fuels provided around 85 % of the world’s largest total primary energy supply. Caused by climate change, affordable energy costs, more dispersed production, and environmental factors, biomass to energy transfer takes increased as of 65 GW in 2010 to 120 GW in 2019. Anaerobic digestion, digestion, and landfill processes are more suitable for wastes with high moisture. Just at end of 2019, the worldwide output of biogas plants was estimated to be at 19.5 GW. Due to their high moisture content and degradation rate, organic pollutants are among the most popular feedstocks for producing biogas from trash, including home wastes. The organic portion of municipal waste is represented by these input materials, which are classed as Organic wastes. This study describes the various application of biogas with special reference to household use and how it is important in today’s scenario.

Site Trials of Methane Capture from Low-Concentration Coalbed Methane Drainage Wells Using a Mobile Skid-Mounted Vacuum Pressure Swing Adsorption System

Site Trials of Methane Capture from Low-Concentration Coalbed Methane Drainage Wells Using a Mobile Skid-Mounted Vacuum Pressure Swing Adsorption System

Co-Al and Mn-Fe Catalytic Steam Reforming of CH3OH to H2

Catalytic production of hydrogen by steam methanol reforming (SMR) is an attractive option for specific applications in fuel cells, decentralized generation of H2 or localized boosting of the energy content of digestion gas. Supported metal catalysts integrate the endothermic methanol steam reforming with the exothermic Boudouard reaction. The paper reviews the fundamentals of SMR, develops 2 self-made, cheap and efficient catalysts, and demonstrates that high H2 yields with low CO and CO2 by-product formation. Present methanol reformers are mostly of the packed bed type which suffer from problems of temperature gradients within the catalyst bed and a slow response during start up and transients. In using a vibrated fluidized bed of the micron-size catalysts, a uniform bed temperature is achieved. More than 600 L/hr of hydrogen can be generated at methanol conversions in excess of 95%. A too high space velocity in the catalytic bed significantly reduces the methanol conversion, however without affecting the H2 yields. The assessed systems clearly merit pilot plant research.

Deep Learning on Synthesized Sensor Characteristics and Transmission Spectra Enabling MEMS-Based Spectroscopic Gas Analysis beyond the Fourier Transform Limit

Miniaturized Fourier transform infrared spectrometers serve emerging market needs in many applications such as gas analysis. The miniaturization comes at the cost of lower performance than bench-top instrumentation, especially for the spectral resolution. However, higher spectral resolution is needed for better identification of the composition of materials. This article presents a convolutional neural network (CNN) for 3X resolution enhancement of the measured infrared gas spectra using a Fourier transform infrared (FTIR) spectrometer beyond the transform limit. The proposed network extracts a set of high-dimensional features from the input spectra and constructs high-resolution outputs by nonlinear mapping. The network is trained using synthetic transmission spectra of complex gas mixtures and simulated sensor non-idealities such as baseline drifts and non-uniform signal-to-noise ratio. Ten gases that are relevant to the natural and bio gas industry are considered whose mixtures suffer from overlapped features in the mid-infrared spectral range of 2000–4000 cm−1. The network results are presented for both synthetic and experimentally measured spectra using both bench-top and miniaturized MEMS spectrometers, improving the resolution from 60 cm−1 to 20 cm−1 with a mean square error down to 2.4×10−3 in the transmission spectra. The technique supports selective spectral analysis based on miniaturized MEMS spectrometers.

Molecular dynamics simulation to explore the impact of wax crystal on the formation of methane hydrate

The combined problem caused by wax and hydrate deposition is the key issue to be considered for the subsea multiphase (crude oil, gas, and water) flow assurance. In our study, molecular dynamics technique was performed to generate the solid state wax crystal and further study the impact of wax crystal on the formation of methane hydrate on the microscopic level. Our simulation results showed that wax crystal played a dual role in methane hydrate formation (i.e. promotion and inhibition effects), depending on its size. Small wax crystal would shorten the hydrate nucleation time from 19 ns to about 12 ns, facilitate the 51262 cage formation and increase the conversion ratio of methane and water molecules to methane hydrate by more than 1.5 times. In this process, the competitive capture of methane in gas–liquid, gas-hydrate and liquid-hydrate phases could be detected. When the size of wax crystal exceeded the critical value, the formation of hydrate would be inhibited and the nucleation time was prolonged beyond 500 ns. In this case, the competition of methane capture between wax crystal and aqueous solution would dominated the whole process. The presence of small wax crystal accelerated the hydrate nucleation and growth by facilitating the molecular migration of H2O and CH4 to a certain extent and promoting the assembly of water and methane molecules into hydrate precursors. However, a further increase in the diffusion velocity of methane and water molecules induced by the stronger gas adsorption performance of more wax would lead to the aggregation of methane molecules into large nano-bubbles, reducing the CH4 concentration in the solution far below the hydrate formation threshold value. Eventually, hydrate cages would not be formed and survival. The results in this work would contribute to a better understanding of the wax-hydrate interaction.

Enhancement effect of γ-irradiation pre-treatment on anaerobic digestion performance of kitchen wastewater

In China, the annual output of kitchen wastewater with high oil content has exceeded 90 million tons, which poses a threat to the environment. Anaerobic digestion is considered a suitable treatment approach to realize the harmless and resource utilization of kitchen wastewater of the available bioresource. This study explored a pretreatment method based on gamma radiation to reduce the oil content in kitchen wastewater and improve its anaerobic digestion performance. In addition, response surface analysis was used to optimize the pretreatment conditions and build the production of kitchen wastewater gas prediction model. The results show that the deviation between the predicted value of the model and the actual value is less than 1.5%. The results show that the oil content decreases by 61% and the amount of anaerobic digestion gas production increases by 59% under the absorbed dose of 11.76 kGy, pH of 8.6, and the hydrogen peroxide concentration of 3.5 mmol/L, compared with those of the unirradiated wastewater. The gas chromatography and Fourier transform infrared spectroscopy analysis results show that there are more biodegradable organic substances in the wastewater after irradiation.

Exergy-environment assessment for energy system: Distinguish the internal and total exergy loss, and modify the contribution of utility

Improving the efficiency of energy system is a way to reduce its environmental impact. However, high efficiency always means high system complexity and high expense, and will again increase the environmental impact. This work proposed an exergy-environment assessment method for energy system. With the exergy balance calculation, the method converted the internal and total exergy loss flows, as well as the life-cycle consumed material (including utility), to the values of environmental impact points. This work also proposed indexes to assess whether the energy transformation (exergy loss) or the life-cycle consumption dominates the environmental impact. Then, this work adopted a sludge digestion system to show the application of the proposed method. The exergy analysis and environmental impact points of the system were calculated. The entire system has a positive exergy output of digestion gas (4.18 GJ h−1). The objective exergy efficiency of system is 27.11%, and the general exergy efficiency of digester unit (80.10%) is over two times that of heating unit (35.00%). Heating unit also has a much higher environmental impact than digester unit (about 1.00: 0.15). Results show that the exergy-environment assessment does not breach the classical thermodynamic analysis and provides the understanding of environmental impact. Compared to previous studies, this work resolves the issue of unreasonable data for the exergy-environment impact factor in methodology by amending its value from <0 or ≈0 to 0.40, clarifying the significance and rationality of exergy-environment assessment. The case study result shows the feasibility and advantage of the proposed method, which can be flexibly selected by decision maker. Impact factor based on the internal exergy loss is relatively preferred from the perspective of sustainability.