Resource recovery from sugarcane vinasse by anaerobic digestion - A review

The increase in biofuel production by 2030, driven by the targets set at the 21st United Nations Framework Convention on Climate Change (COP21), will promote an increase in ethanol production, and consequently more vinasse generation. Sugarcane vinasse, despite having a high polluting potential due to its high concentration of organic matter and nutrients, has the potential to produce value-added resources such as volatile fatty acids (VFA), biohydrogen (bioH₂) and biomethane (bioCH₄) from anaerobic digestion. The objective of this paper is to present a critical review on the vinasse treatment by anaerobic digestion focusing on the final products. Effects of operational parameters on production and recovery of these resources, such as pH, temperature, retention time and type of inoculum were addressed. Given the importance of treating sugarcane vinasse due to its complex composition and high volume generated in the ethanol production process, this is the first review that evaluates the production of VFAs, bioH₂ and bioCH₄ in the treatment of this organic residue. Also, the challenges of the simultaneous production of VFA, bioH₂ and bioCH₄ and resources recovery in the wastewater streams generated in flex-fuel plants, using sugarcane and corn as raw material in ethanol production, are presented. The installation of flex-fuel plants was briefly discussed, with the main impacts on the treatment process of these effluents either jointly or simultaneously, depending on the harvest season.

Multidimensional approaches of biogas production and up-gradation: Opportunities and challenges

The expanding interest towards biogas generation from biowaste via complex anaerobic digestion (AD) opened new avenues in the improvement of biogas production processes and their up-gradation. The adsorption/removal of impurities particularly hydrogen sulfide (H₂S) and carbon dioxide (CO₂) from the biogas stream will significantly improve the efficiency of biogas for its further use as a renewable energy fuel. The production and up-gradation of biogas rely upon the types of feedstocks, AD condition, microbial diversity, purification methods along with the application of various additives. In that context, this review aims to emphasize the current state of the art in the field of biogas production via AD using diverse bio-waste. Further, this review will critically explore the biogas up-gradation technologies adopted so far and their pros and cons. Finally, techno-economic and environmental impact assessment of the biogas production process will be underlined to make the process cost-effective and environmentally sustainable.

Insights into the Enhancement of MOF/Polymer Adhesion in Mixed-Matrix Membranes via Polymer Functionalization

MOF-based mixed-matrix membranes (MMMs) prepared using standard routes often exhibit poor adhesion between polymers and MOFs. Herein, we report an unprecedented systematic exploration on polymer functionalization as the key to achieving defect-free MMMs. As a case study, we explored computationally MMMs based on the combination of the prototypical UiO-66(Zr) MOF with polymer of intrinsic porosity-1 (PIM-1) functionalized with various groups including amidoxime, tetrazole, and N-((2-ethanolamino)ethyl)carboxamide. Distinctly, the amidoxime-derivative PIM-1/UiO-66(Zr) MMM was predicted to express the desired enhanced MOF/polymer interfacial interactions and thus subsequently prepared and evaluated experimentally. Prominently, high-resolution transmission electron microscopy confirmed optimal adhesion between the two components in contrast to the nanometer-sized voids/defects shown by the pristine PIM-1/UiO-66(Zr) MMM. Notably, single-gas permeation measurements further corroborated the need of optimal MOF/polymer adhesion in order to effectively enable the MOF to play a role in the gas transport of the resulting MMM.

Biogas from Anaerobic Digestion as an Energy Vector: Current Upgrading Development

The present work reviews the role of biogas as advanced biofuel in the renewable energy system, summarizing the main raw materials used for biogas production and the most common technologies for biogas upgrading and delving into emerging biological methanation processes. In addition, it provides a description of current European legislative framework and the potential biomethane business models as well as the main biogas production issues to be addressed to fully deploy these upgrading technologies. Biomethane could be competitive due to negative or zero waste feedstock prices, and competitive to fossil fuels in the transport sector and power generation if upgrading technologies become cheaper and environmentally sustainable.

A New Perspective for Climate Change Mitigation—Introducing Carbon-Negative Hydrogen Production from Biomass with Carbon Capture and Storage (HyBECCS)

The greatest lever for advancing climate adaptation and mitigation is the defossilization of energy systems. A key opportunity to replace fossil fuels across sectors is the use of renewable hydrogen. In this context, the main political and social push is currently on climate neutral hydrogen (H2) production through electrolysis using renewable electricity. Another climate neutral possibility that has recently gained importance is biohydrogen production from biogenic residual and waste materials. This paper introduces for the first time a novel concept for the production of hydrogen with net negative emissions. The derived concept combines biohydrogen production using biotechnological or thermochemical processes with carbon dioxide (CO2) capture and storage. Various process combinations referred to this basic approach are defined as HyBECCS (Hydrogen Bioenergy with Carbon Capture and Storage) and described in this paper. The technical principles and resulting advantages of the novel concept are systematically derived and compared with other Negative Emission Technologies (NET). These include the high concentration and purity of the CO2 to be captured compared to Direct Air Carbon Capture (DAC) and Post-combustion Carbon Capture (PCC) as well as the emission-free use of hydrogen resulting in a higher possible CO2 capture rate compared to hydrocarbon-based biofuels generated with Bioenergy with Carbon Capture and Storage (BECCS) technologies. Further, the role of carbon-negative hydrogen in future energy systems is analyzed, taking into account key societal and technological drivers against the background of climate adaptation and mitigation. For this purpose, taking the example of the Federal Republic of Germany, the ecological impacts are estimated, and an economic assessment is made. For the production and use of carbon-negative hydrogen, a saving potential of 8.49–17.06 MtCO2,eq/a is estimated for the year 2030 in Germany. The production costs for carbon-negative hydrogen would have to be below 4.30 € per kg in a worst-case scenario and below 10.44 € in a best-case scenario in order to be competitive in Germany, taking into account hydrogen market forecasts.

Effect of pH on the performance of an acidic biotrickling filter for simultaneous removal of H2S and siloxane from biogas

Acidic biotrickling filters (BTF) can be used for simultaneous removal of hydrogen sulfide (H₂S) and siloxane from biogas. In this study, the performance of a BTF under different acidic pH conditions was investigated. The removal profile of H₂S showed that 90% of H₂S removal was achieved during the first 0.4 m of BTF height with down-flow biogas. Decamethylcyclopentasiloxane (D5) removal decreased from 34.5% to 15.6% when the pH increased from 0.88 to 3.98. Furthermore, the high partition coefficient of D5 obtained in under higher pH condition was attributed to the higher total ionic strength resulting from the addition of sodium hydroxide solution and mineral medium. The linear increase in D5 removal with the mass transfer coefficient (k_L) indicated that the acidic recycling liquid accelerated the mass transfer of D5 in the BTF. Therefore, the lower partition coefficient and higher k_L under acidic pH conditions lead to the efficient removal of D5. However, the highly acidic pH 0.9 blocked mass transfer of H₂S and O₂ gases to the recycling liquid. Low sulfur oxidation activity and low Acidithiobacillus sp. content also deteriorated the biodegradation of H₂S. Operating the BTF at pH 1.2 was optimal for simultaneously removing H₂S and siloxane.

Scalable crystalline porous membranes: current state and perspectives

Crystalline porous materials (CPMs) with uniform and regular pore systems show great potential for separation applications using membrane technology. Along with the research on the synthesis of precisely engineered porous structures, significant attention has been paid to the practical application of these materials for preparation of crystalline porous membranes (CPMBs). In this review, the progress made in the preparation of thin, large area and defect-free CPMBs using classical and novel porous materials and processing is presented. The current state-of-the-art of scalable CPMBs with different nodes (inorganic, organic and hybrid) and various linking bonds (covalent, coordination, and hydrogen bonds) is revealed. The advances made in the scalable production of high-performance crystalline porous membranes are categorized according to the strategies adapted from polymer membranes (interfacial assembly, solution-casting, melt extrusion and polymerization of CPMs) and tailored based on CPM properties (seeding-secondary growth, conversion of precursors, electrodeposition and chemical vapor deposition). The strategies are compared and ranked based on their scalability and cost. The potential applications of CPMBs have been concisely summarized. Finally, the performance and challenges in the preparation of scalable CPMBs with emphasis on their sustainability are presented.

Oxygen-enriched surface modification for improving the dispersion of iron oxide on a porous carbon surface and its application as carbon molecular sieves (CMS) for CO2/CH4 separation

The separation of CO₂/CH₄ can be enhanced by impregnating porous carbon with iron oxide. Dispersion of iron oxide is one of the critical factors which supports the separation process performance. Iron oxide dispersion can be enhanced by enriching the oxygen functional groups on the carbon surface. This study investigates three distinct oxidation processes: oxidation with a 10% H₂O₂ solution, ozonation with distilled water, and ozonation with a 10% H₂O₂ solution. The research steps included the following: (i) oxidation, (ii) impregnation of iron oxide followed by calcination, (iii) material characterization, and (iv) material performance analysis. Materials were characterized using N₂ sorption analysis, X-ray diffraction analysis (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy analysis (SEM-EDX), and Fourier transform infrared analysis (FT-IR). Iron oxide was well dispersed on the carbon surface, as evidenced by the elemental mapping of materials. In addition, the oxygen functional groups increased significantly in the range of 28.6–79.7% following the oxidation process, as indicated by the elemental component using SEM-EDX analysis. The impregnation of iron oxide on oxidized carbon ozonated with distilled water (COA–Fe) obtained a maximum CO₂ uptake capacity of 3.0 mmol g⁻¹ and CO₂/CH₄ selectivity increased by up to 190% at a temperature of 30 °C and pressure of 1 atm. Furthermore, the enhancement of CO₂/CH₄ separation up to 1.45 times was the best performance achieved by COA–Fe. Thus, improving iron oxide dispersion on oxidized carbon surfaces has a potential application in CO₂/CH₄ separation.

The separation of CO₂/CH₄ can be enhanced by impregnating porous carbon with iron oxide.

WITHDRAWN: Sustainable liquid membrane separation using interfacial engineering of deep eutectic solvent and cellulose acetate

This article has been withdrawn at the request of the editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

Cost and Life-Cycle Greenhouse Gas Implications of Integrating Biogas Upgrading and Carbon Capture Technologies in Cellulosic Biorefineries

Gaseous streams in biorefineries have been undervalued and underutilized. In cellulosic biorefineries, coproduced biogas is assumed to be combusted alongside lignin to generate process heat and electricity. Biogas can instead be upgraded to compressed biomethane and used as a transportation fuel. Capturing CO₂-rich streams generated in biorefineries can also contribute to greenhouse gas (GHG) mitigation goals. We explore the economic and life-cycle GHG impacts of biogas upgrading and CO₂ capture and storage (CCS) at ionic liquid-based cellulosic ethanol biorefineries using biomass sorghum. Without policy incentives, biorefineries with biogas upgrading systems can achieve a comparable minimum ethanol selling price (MESP) and reduced GHG footprint ($1.38/liter gasoline equivalent (LGE) and 12.9 gCO_2e/MJ) relative to facilities that combust biogas onsite ($1.34/LGE and 24.3 gCO_2e/MJ). Incorporating renewable identification number (RIN) values advantages facilities that upgrade biogas relative to other options (MESP of $0.72/LGE). Incorporating CCS increases the MESP but dramatically decreases the GHG footprint (-21.3 gCO_2e/MJ for partial, -110.7 gCO_2e/MJ for full CCS). The addition of CCS also decreases the cost of carbon mitigation to as low as $52-$78/t CO₂, depending on the assumed fuel selling price, and is the lowest-cost option if both RIN and California's Low Carbon Fuel Standard credits are incorporated.

Bioeconomy - present status and future needs of industrial value chains

The necessary reduction of greenhouse gas emissions requires a comprehensive shift from fossil to renewable raw materials. This is accompanied by a fundamental reorganization of the value chains of the energy sectors and large parts of the manufacturing industry. In the long term, bio-based industrial raw materials will be processed preferentially by the chemical industry. In order to use the raw materials as fully as possible, sectors that support cascade use and the recycling of by-products and products after use will gain in importance. These are in particular the waste management and energy sectors, which will be integrated into the circular value chains of the bioeconomy. The industrial realization of these value chains depends essentially on the legal framework conditions, which must be developed further accordingly.

Progressing Climate Changes and Deteriorating Air Quality as One of the Biggest Challenges of Sustainable Development of the Present Decade in Poland

Among the biggest challenges facing our civilization is slowing down the rate of climate change and improving air quality in cities. This cannot be achieved in isolation from the sustainability and intensification of relevant research. The aim of this Special Issue: Current Trends in Emission Control and Forecasting of Air Quality and Climate Changes is to publish selected high-quality papers from the 15th Scientific Conference POL-EMIS 2020: Current Trends in Air and Climate Protection—Control Monitoring, Forecasting, and Reduction of Emissions (19–21 October 2020, Wroclaw) and other papers related to the development of: low-emission fuels, industrial technologies, and energy generation, including renewable energy sources (RES); technology for reducing/eliminating emissions from low municipal sources and transport; innovative methods of waste gas purification; emission and immission control methods (including odors); prospective ways of counteracting climate change; indoor air protecting methods; development of mathematical modeling of air quality; new directions in forecasting the effects of air pollution and climate change and air quality management.

Surface Modifications of Nanofillers for Carbon Dioxide Separation Nanocomposite Membrane

CO2 separation is an important process for a wide spectrum of industries including petrochemical, refinery and coal-fired power plant industries. The membrane-based process is a promising operation for CO2 separation owing to its fundamental engineering and economic benefits over the conventionally used separation processes. Asymmetric polymer–inorganic nanocomposite membranes are endowed with interesting properties for gas separation processes. The presence of nanosized inorganic nanofiller has offered unprecedented opportunities to address the issues of conventionally used polymeric membranes. Surface modification of nanofillers has become an important strategy to address the shortcomings of nanocomposite membranes in terms of nanofiller agglomeration and poor dispersion and polymer–nanofiller incompatibility. In the context of CO2 gas separation, surface modification of nanofiller is also accomplished to render additional CO2 sorption capacity and facilitated transport properties. This article focuses on the current strategies employed for the surface modification of nanofillers used in the development of CO2 separation nanocomposite membranes. A review based on the recent progresses made in physical and chemical modifications of nanofiller using various techniques and modifying agents is presented. The effectiveness of each strategy and the correlation between the surface modified nanofiller and the CO2 separation performance of the resultant nanocomposite membranes are thoroughly discussed.

Application of Ion Mobility Spectrometry for Permeability Studies of Organic Substances through Polymeric Materials

Drift tube ion mobility spectrometers (DT IMS) allow the concentration of different organic compounds to be measured. This gives the opportunity to use these detectors in measuring the penetration of various substances through polymer membranes. Permeation measurements of two substances (2-heptanone and dimethyl methylphosphonate (DMMP)) through a cylindrical silicone rubber membrane were carried out. The membrane separated the aqueous solution from the air. The analyte was introduced into water, and then its concentration in air on the opposite side of the membrane was recorded. Based on the dynamics of detector signal changes, the diffusion coefficients for both tested substances were determined. Determination of permeability coefficients was based on precise quantitative measurements, which took into account the non-linearity of the detector characteristics and the effect of water on detection sensitivity. The analysis of measurement results was based on a mathematical description of diffusion process.

Gas transport properties of cellular hollow fiber membranes based on LLDPE/LDPE blends

The production of foamed hollow fiber membranes (HFMs) is presented based on polymer blends using various concentrations of linear low-density polyethylene (LLDPE) and low-density polyethylene (LPDE) combined with azodicarbonamide (chemical blowing agent) to prepare samples via twin-screw extrusion. In particular, the blowing agent concentration as well as the stretching speed were found to be the most important parameters to achieve a good cellular structure for membrane application. From the samples obtained, a complete set of morphological, thermal, and gas transport characterization was performed. The results show that LLDPE/LDPE blends compared to neat LLDPE lead to higher cell density at high stretching speed, which is appropriate for membranes having higher gas permeability and selectivity due to lower cell wall thickness. The results also show that the developed cellular structure has high potential for the continuous production of HFMs for different gas separation, especially for hydrogen recovery.

Simultaneous removal of siloxanes and H2S from biogas using an aerobic biotrickling filter

The feasibility of simultaneous removal of siloxane and H₂S from biogas was investigated using an aerobic biotrickling filter (BTF). The biodegradation of H₂S in the BTF followed a first-order kinetic model and more than 95 % H₂S was eliminated within a residence time of 0.3 min. The removal of decamethylcyclopentasiloxane (D5) increased with longer empty bed residence time (EBRT). The partition test and microbial community analysis further reveals that up to 52 % removal of D5 was reached mainly by the chemical-absorption in acid recycling liquid. Finally, D5 was converted into mixtures of dimethylsilanediol (DMSD) and hexamethyldisiloxane (L2) via ring-opening hydrolysis in acid liquid and ring-shrinking polyreaction using CH₄ derived from biogas. These operational characteristics demonstrate that the abiotic removal of D5, in addition to biological removal of H₂S in an aerobic BTF can significantly decrease the siloxane loading to the downstream siloxane removing units.

Superior performance of surface-treated NaX@Pebax-1657 membranes for O2/N2 separation

In this study, the performances of mixed matrix composite membranes (MMCMs) containing surface-treated NaX nanocrystals (ST-NaX-NCs) were experimentally and theoretically investigated for O₂/N₂ separation. For this purpose, the MMCMs were fabricated by the casting solution method and characterized by various analyses. The results reveal that there is a robust interaction between the polymer chains and the ST-NaX-NCs, and that the ST-NaX fillers are uniformly dispersed in the polymer matrix. The incorporation of ST-NaX-NCs alters the PEBAX polymer chain packing arrangement resulting in decreased membrane transport behavior for both O₂ and N₂ gases. The MMCM containing 16.7% wt ST-NaX-NCs has drastically enhanced air separation properties, with a selectivity that is increased to 204% of that of the neat membrane. Moreover, the Lewis-Nielsen model was modified by considering non-ideal effects in mixed matrix membranes, like the clogging of filler pores and polymer chain hardening around the nanocrystals, to predict the gas permeation behavior through the MMCMs. The comparison of the experimental and model results reveals that the modified model can accurately predict the gas permeability and selectivity through the MMCMs.

Glassy PEEK-WC vs. Rubbery Pebax®1657 Polymers: Effect on the Gas Transport in CuNi-MOF Based Mixed Matrix Membranes

Mixed matrix membranes (MMMs) are seen as promising candidates to overcome the fundamental limit of polymeric membranes, known as the so-called Robeson upper bound, which defines the best compromise between permeability and selectivity of neat polymeric membranes. To overcome this limit, the permeability of the filler particles in the MMM must be carefully matched with that of the polymer matrix. The present work shows that it is not sufficient to match only the permeability of the polymer and the dispersed phase, but that one should consider also the individual contributions of the diffusivity and the solubility of the gas in both components. Here we compare the gas transport performance of two different MMMs, containing the metal–organic framework CuNi-MOF in the rubbery Pebax®1657 and in the glassy poly(ether-ether-ketone) with cardo moiety, PEEK-WC. The chemical and structural properties of MMMs were investigated by means of FT-IR spectroscopy, scanning electron microscopy and EDX analysis. The influence of MOF on the mechanical and thermal properties of both polymers was investigated by tensile tests and differential scanning calorimetry, respectively. The MOF loading in Pebax®1657 increased the ideal H2/N2 selectivity from 6 to 8 thanks to an increased H2 permeability. In general, the MOF had little effect on the Pebax®165 membranes because an increase in gas solubility was neutralized by an equivalent decrease in effective diffusivity. Instead, the addition of MOF to PEEK-WC increases the ideal CO2/CH4 selectivity from 30 to ~48 thanks to an increased CO2 permeability (from 6 to 48 Barrer). The increase in CO2 permeability and CO2/CH4 selectivity is maintained under mixed gas conditions.

Mixed Matrix Membranes

In recent decades, mixed matrix membranes (MMMs) have attracted considerable interest in research laboratories worldwide, motivated by the gap between the growing interest in developing novel mixed matrix membranes by various research groups and the lack of large-scale implementation. This Special Issue contains six publications dealing with the current opportunities and challenges of mixed matrix membranes development and applications as solutions for the environmental and health challenges of 21st century society.

Experimental Analysis and Model Validation on the Performance of Impregnated Activated Carbons for the Removal of Hydrogen Sulfide (H2S) from Sewage Biogas

Organic waste exploitation is crucial for waste emissions restraint in air, soil and water. This type of waste can be exploited to produce biogas, a valuable fuel exploitable for energy purposes. A circular approach for energy production is much cleaner and more sustainable than the traditional linear approach. In this work, organic waste was used for biogas production to feed a highly efficient solid oxide fuel cell power generator, which requires an ultra-purified fuel. Commercial sorbents were experimentally studied in conjunction with a dynamic adsorption model to predict the breakthrough time and organize the material change-over. In the presence of 0.1% oxygen in the gas mixture, AirDep® CKC showed a marked increase in the adsorption capacity (from 3.91 to 84.87 mg/g), overcoming SulfaTrap® R8G (49.91 mg/g). The effect of several operating parameters on adsorption capacity was evaluated: inlet H2S concentration, filter geometry and gas mixture velocity. Experimental data revealed that adsorption capacity increases with initial H2S concentration, following the typical trend of the Langmuir isotherm. Model simulations were in good agreement compared to experimental results, with an average relative error lower than 7%. A sensitivity analysis on the adsorption capacity was accomplished considering parameters from operational and empirical correlations.

Graphene-Based Membranes for CO2/CH4 Separation: Key Challenges and Perspectives

Increasing demand to strengthen energy security has increased the importance of natural gas sweetening and biogas upgrading processes. Membrane-based separation of carbon dioxide (CO2) and methane (CH4) is a relatively newer technology, which offers several competitive advantages, such as higher energy-efficiency and cost-effectiveness, over conventional technologies. Recently, the use of graphene-based materials to elevate the performance of polymeric membranes have attracted immense attention. Herein, we do not seek to provide the reader with a comprehensive review of this topic but rather highlight the key challenges and our perspectives going ahead. We approach the topic by evaluating three mainstream membrane designs using graphene-based materials: (1) nanoporous single-layer graphene, (2) few- to multi-layered graphene-based stacked laminates, and (3) mixed-matrix membranes. At present, each design faces different challenges, including low scalability, high production cost, limited performance enhancement, and the lack of robust techno-economic review and systematic membrane design optimization. To help address these challenges, we have mapped out a technology landscape of the current graphene-based membrane research based on the separation performance enhancement, commercial viability, and production cost. Accordingly, we contend that future efforts devoted to advancing graphene-based membranes must be matched by progress in these strategic areas so as to realize practical and commercially relevant graphene-based membranes for CO2/CH4 separation and beyond.

A Case Study on the Electricity Generation Using a Micro Gas Turbine Fuelled by Biogas from a Sewage Treatment Plant

Combined heat and power production from biogas is now playing an important role in energy and resource utilization as well as pollution control in waste water treatment. This research used biogas from the Bali Sewage Treatment Plant in New Taipei City, Taiwan, as a major source of fuel for the electricity generation. A micro gas turbine electricity generator, Capstone CR-30, which possesses a maximum rated power load (PWL) of 30 kW, was equipped to convert biogas into electricity. The biogas is mainly composed of CH4 (56.1 ± 8.0 vol.%), CO2 (25.5 ± 9.8 vol.%), H2 (0.5 vol.%), and H2S (0.99 ± 0.07 ppmv). During the test operation period of the generator, it was found that the thermal efficiency increases from 19.8% to 23.4% kWhe/kWhth, while the electricity generation efficiency (ηEB) also rises from 0.93 to 1.09 kWhe/m3 biogas as the PWL increases from 10 kW to 30 kW. The results indicated that the generator has a better performance with higher PWL. At PWL = 30 kW, the average adjusted concentrations of CO and NOx (adjusted to 15 vol.% O2) emitted from the generator are 86 ppmv and 17 ppmv, respectively. Both are much lower than the emission standards of stationary sources in Taiwan of 2000 ppmv and 150 ppmv, respectively. Thus, PWL of 30 kW was selected in cooperation with biogas inflow = 0.412 m3/min and air/fuel ratio (i.e., air/biogas ratio) = 76.0 vol./vol. for the long-term regular operation. At the above setting conditions for long-term operation, the generator continuously consumed the biogas and provided stable electricity generation at a rate of 19.64 kWhe/h for a 2-year running period. Moreover, the greenhouse gas can be cut off with a rate of 10.78 kg CO2e/h when using biogas as fuel for electricity generation. Overall, this research proves that the application of a micro gas turbine electricity generator not only has promising performance for using biogas but also gives a significant reduction of greenhouse gas emission, which fits the concepts of the circular economy and environmental protection.

Review of technologies for biomethane production and assessment of Eu transport share in 2030

The upgrade to biomethane allows extending biogas applications to transport sectors, supporting EU goals toward carbon neutrality. Biomethane produced from biogas upgrading can today rely on a large number of plants, estimated by the European Biogas Association in over 17000 in 2016, for a total installed capacity of 9985 GW (EBA, 2017). After 2020, biogas and biomethane will count towards the 32% target of renewable energy share of the EU energy consumption, and towards a sub-target of minimum 14% of the energy consumed in the transport sector by 2030 (REDII). In this framework, the paper aims to define the current market penetration of biogas upgrading technologies. A database has been created for EU-28, to highlight the relative importance of each technology. Based on the database, a EU production potential is defined, along with the EU demand potential for transport, in order to verify the match between supply and demand. The analysis of the current state of play of the sector suggests that a large potential can be foreseen for near future; the expected increase in biomethane production is based also on the possibility to convert residual feedstocks, such as Municipal Solid Wastes. In this work a moderate technology penetration scenario has been set for EU-28, reaching a potential for biomethane of 18 billion m³/year in 2030. A large share of this potential can be devoted to transport, with a relevant impact on the sector. LNG appears suitable for pushing the market uptake of biomethane in the transport sector. Among the potential uses of biomethane for transport, it is worth considering that the natural gas use in the maritime and internal waterways sectors is getting momentum. The current analysis aimed to highlight the potential of renewable energy-based alternatives to natural gas. Eventually, it is worth noticing that the real market deployment of this potential will be determined by the energy market conditions, and by the member states capability to stimulate the industry through a coherent set of supporting initiatives.

Basic and procedural requirements for energy potential from biogas of sewage treatment plants

The objective of this study is to evaluate the potential for electricity generation in the State of São Paulo (SP) from the sewage treatment. A sewage treatment plant (STP) with domain in the production of biogas from wastewater treatment plant (WWTP) is the basis for this case study. The basic premise is that the very generation of electricity in STPs is advantageous for companies in the sanitation sector in Brazil, resulting in cost reductions of the treatment process. Gains at the end of the process are found in two levels, namely: (i) economic, by generating 165% of electricity from biogas burning in relation to the expend; (ii) energy, by adding a new sustainable and storable energy source equivalent to 4% of natural gas offered in the State of SP and 0,5% of electricity produced from biogas burning in relation to electricity consumption. In conclusion, the potential of electricity production linked to the biogas at STPs is capable of supply its domestic demand and export the surplus to other segments of the state and national economy.

Evaluation of biogas upgrading technologies and future perspectives: a review

Biogas is acknowledged as one of the foremost bioenergy to address the current environmental and energy challenges being faced by the world. Commonly, biogas is used for applications like cooking, lighting, heat and power production. To widen the scope of biogas application, like transportation, natural gas grid injection and substrate for the production of chemicals and fuel cells, mainly CO₂, H₂S and other impurities need to be removed by various upgrading technologies. It is an important process to produce biomethane with above 90% methane. There are various physico-chemical (adsorption, absorption, cryogenic and membrane separations) and biological (in situ and ex situ) processes for biogas upgradation, and each process is site and case specific. The aim of the present paper is to thoroughly evaluate the existing and emerging biogas upgrading technologies. Analysis of each technology with respect to basis of operations, energy requirement, methane purity and recovery and cost economics has been carried out. A thorough analysis has been done on the major hurdles and the research gaps in this sector. For a wider and successful implementation of the biogas upgradation technology, the trends in research and development (R&D) such as development of efficient biogas upgrading technologies, adsorbents, reduction in cost and methane loss have been thoroughly evaluated.