Biogas Recovery Research Articles

Nutrient recovery abates methane emissions from digestate storage

Farm-based anaerobic digestion is a promising source of renewable natural gas (RNG), but the carbon intensity of RNG is influenced by methane (CH4) emissions from digestate storage. This study evaluated whether a nutrient recovery system could minimize digestate CH4 emissions from uncovered storage. Nutrients were concentrated in the solid fraction, which contained 82% of the Phosphorus (P) and 39% of the Nitrogen (N) with only 7% of the water. Laboratory results showed that the CH4 emission potential from digestate was 113 ± 6 mL g−1 volatile solids (VS), which was reduced to zero in the liquid fraction after nutrient separation. Measurements from the 0.4-ha uncovered outdoor liquid storage showed CH4 emissions were low, with annual emissions being 1.5% of the CH4 collected by the biodigester. Storage emissions could be further reduced by ensuring that all manure passed through the nutrient recovery system. Overall, the combination of biogas and nutrient recovery reduces the carbon intensity of RNG and improves nutrient distribution.

The effects of ammonia acclimation on biogas recovery and the microbial population in continuous anaerobic digestion of swine manure

This study investigated the ammonia toxicity and the acclimation of anaerobic microbiome in continuous anaerobic digestion of swine manure using unacclimated inoculum. When the total ammonia nitrogen concentration (TAN) reached 2.5 g N/L, the methane yield decreased from 254.1 ± 9.6 to 154.6 ± 9.9 mL/g COD. The free ammonia nitrogen concentration of the inhibited condition was 190 mg N/L. The methane yield was eventually recovered as 269.6 ± 3.6 mL/g COD with a further operation. Anaerobic toxicity assay (ATA) showed that mixed liquor from the recovered phase possessed enhanced tolerance to ammonia, not only within the exposed level in continuous operation (<2.5 g NH3/L) but also over the range (>2.5 g NH3/L). Microbial analysis revealed that continuous operation under ammonia stress resulted in the change of both bacterial and archaeal populations. The ammonia adaptation was concurrent with the archaeal population shift from Methanosaeta to Methanosarcina and Methanobacterium. The dominancy of Clostridia in bacterial population was found in the recovered phase. It is highly recommended to use an inoculum acclimated to a target ammonia level which can be pre-checked by ATA and to secure a start-up period for ammonia adaptation in the field application of anaerobic digestion for swine manure.

Enhanced dissolved methane recovery and energy-efficient fouling mitigation via membrane vibration in anaerobic membrane bioreactor

This work successfully developed a novel vibrating AnMBR (VAnMBR) and investigated its long-term performance, fouling control and energy recovery compared to the conventional biogas-sparging AnMBR (BSAnMBR). The VAnMBR achieved better organics removal compared to the BSAnMBR due to the lower content of biopolymers in its effluents. Moreover, the VAnMBR retarded the early TMP rise to alleviate membrane fouling efficaciously with 49.7%–80.2% lower fouling rates than the BSAnMBR. Reduced amounts of nano-particles were consistently observed in the supernatants of the VAnMBR, revealing its benefits to restrict fouling sources for better fouling control. Importantly, the VAnMBR could save 81.9%–94.1% energy of the BSAnMBR and enhance 11.1%–35.0% biogas recovery resulting from minimised dissolved methane, inducing more net energy production during wastewater treatment. The favourable performance of the VAnMBR makes it a promising technology to replace the conventional wastewater treatment plant as a next-generation resource recovery facility.

Estimation of greenhouse gases emission from domestic wastewater in Nepal: A scenario-based analysis applicable for developing countries

Domestic wastewater and wastewater treatment plants (WWTPs) are key emitters of greenhouse gases (GHGs). Quantifying these emissions in the present and future is crucial to tackle global climate change issues. As a developing country with few rural and urban wastewater treatment facilities, Nepal may have a unique opportunity to reduce future GHGs emissions by a proper selection of wastewater treatment technology. In this paper, the authors used Python programming to estimate the GHGs emissions from the domestic wastewater sector in Nepal under various technological development scenarios for 2020 to 2040 using the refined 2019 estimation methodology developed by Inter-governmental Panel on Climate Change (IPCC). Results show total equivalent CO2 emission of 3829.43 and 4523.65 Gigagrams in 2020 and 2040, respectively. The 2020 value is seven times greater than Nepal's 2017 national estimates because this study considered rural population and updated methodology. Comparing the technology development scenarios with the Business as Usual scenario, the highest GHGs reduction could be achieved by hybrid constructed wetlands (69.20%) followed by a combined anaerobic and aerobic system with biogas recovery for energy generation (61.72%). Further accuracy may be attained only through the actual measurement of WWTPs emissions and country-specific emission factors. Thus, this paper proposes GHGs estimation of future scenarios portraying urban and rural populations may be invaluable to policymakers of GHGs mitigation for selection of feasible WWTPs, especially in developing countries with limited wastewater treatment facilities and wastewater activity data.

Membrane distillation bioreactor (MDBR) for wastewater treatment, water reuse, and resource recovery: A review

Membrane bioreactors (MBRs) have been well established as an advanced wastewater treatment technology that combines activated sludge with a pressure-driven membrane separation process. They have been widely applied in municipal and industrial wastewater treatment systems due to their advantages over conventional activated sludge systems. However, MBRs still face major issues hindering their widespread implementation such as poor effluent quality due to low retention of trace organic contaminants, instability due to changing operating conditions, and organic membrane fouling. Membrane distillation (MD) bioreactor (MDBR) is a novel wastewater treatment technology that combines MBRs with an MD unit either separated at a side stream or submerged in the bioreactor. The concept of hybrid MDBR configuration was firstly introduced in 2007 which was followed by numerous journal articles. These studies demonstrated the MDBR potential for water, nutrients, bioenergy, and other value-added product recovery from domestic and industrial wastewater; however, there is still a lack of a comprehensive study that shows the full MDBR potential. Hence there is a need for a dedicated review that summarize and critically analyse these research findings and highlight the research gaps to provide clear path for future research. This review presents system availability and applications of hybrid MDBR. In particular, the review presents brief introduction of MBR and MD technologies followed by covering the evolution of MDBR as a novel technology for municipal and industrial wastewater treatment. Several applications of MDBR systems are reviewed with a focus on system performance and removal efficiencies. The potential of MDBR to widen wastewater reuse and achieve nutrient and biogas recovery is also presented. Finally, the main challenges that hinder the development of MDBR are discussed while recommendations on future perspectives towards MDBR commercialization are suggested.

Analysis of solid waste management scenarios using the WARM model: Case study

The production of municipal solid waste (MSW) is a critical global issue, due to the large amount of waste produced and the environmental impacts it can generate if they are managed improperly. The implementation of modern and efficient solutions, such as waste-to-energy technologies, are important for sustainable development, minimizing environmental impacts and producing renewable energy. MSW managers should use tools, such as scenario analysis, to assess management options more broadly and accurately. Thus, this study aims to analyze alternative scenarios using the Waste Reduction Model (WARM) to find the best solutions for sustainable management of MSW in the city of Xangri-lá (southern Brazil). One hundred and fourteenth (114) scenarios were evaluated that included recycling, landfill (no gas recovery and with flare gas recovery) and Waste-to-Energy (WTE) technologies (landfill with biogas recovery for energy, anaerobic digestion, and incineration). Then, after obtaining the outputs of different scenarios simulated in WARM model, the statistical methods (Principal Component Analysis, Hierarchical Clustering Analysis and Correlation Analysis) were used for data analysis. In addition, an easy-of-use regression model was calibrated to predict intermediate scenarios not covered in the Design of Experiment. The results of this work suggest that the priority, most sustainable, and low-cost strategy for the city of Xangri-lá is to encourage and promote initiatives to gradually increase recycling rates. Afterwards, the biogas collection from the landfill for energy generation presents itself as a viable alternative, mainly in a short period of time. Finally, as long-term solutions, anaerobic digestion and incineration techniques must be implemented, mainly through the establishment of inter-municipal waste management consortia.

Sustainable microalgal biomass valorization to bioenergy: Key challenges and future perspectives

The global trend is shifting toward circular economy systems. It is a sustainable environmental approach that sustains economic growth from the use of resources while minimizing environmental impacts. The multiple industrial use of microalgal biomass has received great attention due to its high content of essential nutrients and elements. Nevertheless, low biomass productivity, unbalanced carbon to nitrogen (C/N) ratio, resistant cellular constituents, and the high cost of microalgal harvesting represent the major obstacles for valorization of algal biomass. In recent years, microalgae biomass has been a candidate as a potential feedstock for different bioenergy generation processes with simultaneous treating wastewater and CO2 capture. An overview of the appealing features and needed advancements is urgently essential for microalgae-derived bioenergy generation. The present review provides a timely outlook and evaluation of biomethane production from microalgal biomass and related challenges. Moreover, the biogas recovery potential from microalgal biomass through different pretreatments and synergistic anaerobic co-digestion (AcoD) with other biowastes are evaluated. In addition, the removal of micropollutants and heavy metals by microalgal cells via adsorption and bioaccumulation in their biomass is discussed. Herein, a comprehensive review is presented about a successive high-throughput for anaerobic digestion (AD) of the microalgal biomass in order to achieve for sustainable energy source. Lastly, the valorization of the digestate from AD of microalgae for agricultural reuse is highlighted.

Organic Waste Management and Circular Bioeconomy: A Literature Review Comparison between Latin America and the European Union

Worldwide, organic waste represents one of the most significant shares in the waste management system. Within the framework of circular bioeconomy, new and cutting-edge infrastructure has been developed at the European level to turn organic waste into valuable resources. The present paper aims to provide an exhaustive comparison between the European Union and Latin America regarding organic waste valorization. To this end, an introductive analysis about the state of the art circular bioeconomy in Latin America and Caribbean countries was developed. Subsequently, a systematic literature review in the context of South and Central America was conducted to detect differences and similarities in technologies and best practices for treating biowaste. The results show that the Latin American region is home to numerous bio-based infrastructures: biogas recovery, composting facilities and bioremediation strategies. Nevertheless, a conclusive remark underlines that some social, economic and political barriers are still encountered in the region, and therefore, new and locally-based studies are of paramount importance.

Hollow-Fiber Membrane Contactor for Biogas Recovery from Real Anaerobic Membrane Bioreactor Permeate.

This study demonstrates the application of hollow-fiber membrane contactors (HFMCs) for the recovery of biogas from the ultrafiltration permeate of an anaerobic membrane bioreactor (AnMBR) and synthetic effluents of pure and mixed CH4 and CO2. The developed membrane degassing setup was coupled with a pilot-scale AnMBR fed with synthetic domestic effluent working at 25 °C. The membrane degassing unit was able to recover 93% of the total dissolved CH4 and 83% of the dissolved CO2 in the first two hours of permeate recirculation. The initial recovery rates were very high (0.21 mg CH4 L−1 min−1 and 8.43 mg CO2 L−1 min−1) and the membrane was able to achieve a degassing efficiency of 95.7% for CH4 and 76.2% for CO2, at a gas to liquid ratio of 1. A higher mass transfer coefficient of CH4 was found in all experimental and theoretical evaluations compared to CO2. This could also be confirmed from the higher transmembrane mass transport resistance to CO2 rather than CH4 found in this work. A strong dependency of the selective gas transport on the gas and liquid side hydrodynamics was observed. An increase in the liquid flow rate and gas flow rate favored CH4 transport and CO2 transport, respectively, over each component. The results confirmed the effectiveness of the collective AnMBR and membrane degassing setup for biogas recovery. Still, additional work is required to improve the membrane contactor’s performance for biogas recovery during long-term operation.

Anaerobic MBR for High Organic Wastewater Treatment and Biogas Recovery

排水中の有機物を酸素のない嫌気環境においてメタンと二酸化炭素にまで分解する嫌気処理技術は，活性汚泥法に代表される好気処理と比べて，省エネ，省廃棄物，バイオガス利用によるエネルギー回収が可能といったメリットがある。嫌気処理は，嫌気性菌が自己造粒したグラニュール汚泥により高負荷処理を可能とするUASB法，EGSB法が食品，飲料工場等を中心に普及している。しかし，SSや油分を含む排水，CODCr濃度が数万mg/Lを超える排水に対しては安定処理が困難であり，前処理でのSS除去や希釈が必要であった。嫌気MBRプロセスは，完全混合型の発酵槽においてスラリー状の汚泥により処理を行うとともに，膜により汚泥を固液分離して発酵槽内に保持することで，こうした排水に対して前処理や希釈なしに処理を行い，バイオガス回収が可能な処理プロセスである。CODCr濃度15,000 mg/L，SS濃度6,000 mg/L，油分濃度1,000 mg/Lのアイスクリーム製造排水の処理において，前処理を伴うUASB法を適用したケースに対し，シンプルなフローとなることで設備全体の必要スペースは40％程度縮小される見込みとなった。また，ランニングコストについても前処理由来の汚泥発生がなくなることで40％程度削減され，バイオガス発電による売電メリットを考慮した場合にはランニングコストを実質的にゼロにできる試算結果が得られた。

Anaerobic MBR for High Organic Wastewater Treatment and Biogas Recovery

Anaerobic MBR for High Organic Wastewater Treatment and Biogas Recovery

Effect of Biogas and Nutrient Recovery Technology on Methane Emissions and Nutrient Budgets

Effect of Biogas and Nutrient Recovery Technology on Methane Emissions and Nutrient Budgets

Part A: Sanitization and use of sewage sludge in soil Technical Note 5 - Thermal sludge drying and sanitization

Thermal drying of the sludge produced in sewage treatment plants (STPs) is a physical process that allows for a significant reduction of the moisture intrinsic to the material, reducing its mass and volume for handling and final disposal. The process also allows for thermal sanitization of the sludge, dispensing the use of chemical products for that purpose. A fundamental requirement for the operationalization of the process is the availability of heat, which can be obtained, for example, through the energy recovery of biogas and the dry sludge found in STPs, corroborating with the concepts of sustainability, renewable energy and circular economy. Although thermal sludge drying is already consolidated in several countries, it is still not a common practice in Brazil. Therefore, this technical note presents the main topics of interest associated with drying and thermal sanitation of sludge for STPs of different sizes, as well as a review of the fundamentals inherent to the process and the methods for selection of dryers. This document also reports examples of thermal sludge drying and sanitization systems, in addition to important aspects to be considered when implementing the process in STPs.

Assessing the Economic Feasibility of Integrated Waste to Use Systems for Uganda

Waste and sanitation Management is a major challenge in urban areas in Uganda where waste is composed of atleast 70% organic content and is basically collected and disposed of in landfills. While 90% of the sanitation facilities used are onsite systems often requiring additional treatment of sewage and faecal matter sewage yet faecal and sewage sludge treatment plants are few. The projected population increase is expected to further influence urbanization, increasing the need for basic waste and sanitation services. Integrated Waste to Use systems that consider combined management of organic waste streams i.e. biowaste, animal waste, sewage and faecal sludge, could be a viable solution for the urban areas. The systems which consist of a combination of anaerobic digestion, composting, incineration and solar drying technologies promote resource recovery in the form of biogas, briquettes and organic fertilizer. The economic feasibility of the Waste to Use systems was carried out and the results indicated that the feasibility of the systems was positively influenced by the inclusion of the anaerobic digestion process, which allowed for recovery of biogas and digestate as organic fertilizer. Furthermore, a combination of low system investment costs, increased revenues from resource recovery, consideration of equity capital of at least 30%, interest rate of at most 10% and fugitive emissions less than 7 % would positively influence the economic feasibility of the system alternatives.

Economic and environmental sustainability for anaerobic biological treatment of wastewater from paper and cardboard manufacturing industry

The sustainable application of an up-flow anaerobic baffled reactor (UABR) to treat real paper and cardboard industrial effluent (PCIE) containing bronopol (2-bromo-2-nitropropan-1, 3-diol) was investigated. At a hydraulic retention time (HRT) of 11.7 h and a bronopol concentration of 7.0 mg L−1, the removal efficiencies of total chemical oxygen demand (CODtotal), CODsoluble, CODparticulate, total suspended solids (TSS), volatile suspended solids (VSS), carbohydrates, and proteins were 55.3 ± 5.2%, 26.8 ± 2.3%, 94.4 ± 4.6%, 89.4 ± 2.6%, 84.5 ± 3.2%, 72.1 ± 1.8%, and 22.4 ± 1.8%, respectively. The conversion of complex organics (e.g., carbohydrates and proteins) into bio-methane (CH4) was assisted via enzyme activities of, in U (100 mL)−1, α-amylase (224–270), α-xylanase (171–188), carboxymethyl cellulase (CM-cellulase) (146–187), polygalacturonase (56–126), and protease (67,000–75300). The acidogenic condition was dominant at a short HRT of 2.9 h, where methane yield dropped by 32.5%. Under this condition, the growth of methanogenic bacteria could be inhibited by volatile fatty acids (VFA) accumulation. The analysis of Fourier-transform infrared (FTIR) spectra detected peaks relevant to methylene and nitro groups in the sludge samples, suggesting that entrapment/adsorption by the sludge bed could be a major mechanism for removing bronopol. The economic feasibility of UABR, as proposed to receive 100 m3 d−1 of PCIE, showed a payback period (profits from environmental benefits, biogas recovery, and carbon credit) of 7.6 yr. The study outcomes showed a high connection to the environmental-, economic-, and social-related sustainable development goals (SDGs).

The impact of landfill operation factors on improving biogas generation in Brazil

The systems for recovering energy from biogas in landfills represent a solution for solid waste treatment and the growing demand for renewable energy. However, landfill biogas recovery in Brazil is not efficient considering that the impact of the operational factors is unknown. To cope with this problem, this study presents a model to measure the impact of the various factors of landfills in the production of biogas. The study focused on improving the generation of methane. The modelling of the impact factors was supported by the Analytic Hierarchy Process (AHP), which was employed to build the strategic map of the cause-and-effect relationship between the factors and the biodegradation. To complement the diagnostic, the performance of biogas companies was evaluated using the Key Performance Indicators (KPI). The results showed that the operational factor that most impacted the methane generation system was the coating process (23.8%), followed by the gas drainage (23.3%) and liquid management (19.6%). On the other hand, site characteristics such as landfill extension and depth had the lowest impact, about five times smaller than that of the coating system. Meanwhile, the factors that most impacted the biodegradation were the moisture content and the fraction of organic carbon. Combined, these two factors had an impact of nearly 40% on the biodegradation process. One of the companies evaluated presented a fully satisfactory performance (80.6%), while the others achieved potentially satisfactory performance concerning the level of achievement of the operational factors. The difference among the companies’ performance was found up to 12.5%.

Modeling landfill CH4 emissions

The current IPCC landfill methane (CH4) methodology excludes critical process drivers now known to control emissions. These include site-specific (1) operational factors (i.e., thickness and composition of various cover soils; physical extent of engineered biogas recovery) and (2) temporal climate effects on soil moisture/temperature profiles in each cover which, in turn, drive gaseous transport, microbial methanotrophic oxidation, and temporally variable “net” CH4 emissions over an annual cycle. Herein, we address the international field validation and application of a process-based model CAlifornia Landfill Methane Inventory Model (CALMIM) which encompasses site-specific climate, cover soils, engineered biogas recovery, and other site-specific strategies. Using embedded soil microclimate models with (a) default 30-year climate data, (b) site-specific annual weather data, or (c) future climate predictions (i.e., CMIP5), the transient soil moisture and temperature effects on bidirectional diffusive CH4/oxygen transport and microbial oxidation can be estimated for any cover soil at any global location. We focus on site-specific field data comparisons to CALMIM-predicted annual and monthly CH4 emissions both without and without methanotrophic oxidation. Overall, 74% of 168 individual surface CH4 emission measurements across 34 international sites were consistent with CALMIM-modeled annual predictions with oxidation (+ or – SD). Notably, the model overpredicted 30 comparisons and underpredicted 13 comparisons. In addition to improving site-specific landfill CH4 inventories, we address how this freely available tool can be used to (a) recommend site-specific cover soil modifications to minimize emissions; (b) systematically compare the spatial and temporal variability of emissions for diverse global locations, latitudinal gradients, extreme climates, and future climate scenarios; (c) assist scheduling of field campaigns to capture seasonal variability; and (d) provide a 12-month annual framework with average monthly CH4 emission statistics for comparison to periodic temporal results from diverse bottom-up and top-down field techniques with variable uncertainties. Importantly, CALMIM does not require intensive site-specific model calibrations.

Application of the anaerobic co-digestion method to sewage sludge treatment toward recover green energy and utilize nutrients for agriculture

Sewage sludge after urban wastewater treatment needs to be treated intelligently to get maximum benefits. This study proposes a method of anaerobic co-degradation of agricultural sludge and residues to both solve environmental problems and recover a large amount of biogas and organic fertilizers. The results show the potential for energy recovery from biogas and impact assessment of the application directly on the rice fields. It is estimated that biogas recovery from sludge treatment from wastewater treatment plants gives a calorific value of about 76 × 106 MJ/year. Results from the trial crop showed that fertilizer shows good supportability to the plant. The results show that the fertilizer from sewage sludge can be reduced and replaced by 50% to 100% of the number of chemical fertilizers but still give the same yield. The data show that the anaerobic co-digestion method is a suitable method for sludge treatment. The dual objective is to provide valuable benefits from recovered biogas and anaerobic digestion products.

Mainstream Nitrogen and Dissolved Methane Removal through Coupling n-DAMO with Anammox in Granular Sludge at Low Temperature.

Mainstream anaerobic wastewater treatment has received increasing attention for the recovery of methane-rich biogas from biodegradable organics, but subsequent mainstream nitrogen and dissolved methane removal at low temperatures remains a critical challenge in practical applications. In this study, granular sludge coupling n-DAMO with Anammox was employed for mainstream nitrogen removal, and the dissolved methane removal potential of granular sludge at low temperatures was investigated. A stable nitrogen removal rate (0.94 kg N m-3 d-1 at 20 °C) was achieved with a high-level effluent quality (<3.0 mg TN L-1) in a lab-scale membrane granular sludge reactor (MGSR). With decreasing temperature, the nitrogen removal rate dropped to 0.55 kg N m-3 d-1 at 10 °C, while the effluent concentration remained <1.0 mg TN L-1. The granular sludge with an average diameter of 1.8 mm proved to retain sufficient biomass (27 g VSS L-1), which enabled n-DAMO and Anammox activity at a hydraulic retention time as low as 2.16 h even at 10 °C. 16S rRNA gene sequencing and scanning electron microscopy revealed a stable community composition and compact structure of granular sludge during long-term operation. Energy recovery could be maximized by recovering most of the dissolved methane in mainstream anaerobic effluent, as only a small amount of dissolved methane was capable of supporting denitrifying methanotrophs in granular sludge, which enabled high-level nitrogen removal.

Bio-Methane Potential (BMP) of Cassava Pulp Waste and Effect of Alkaline Pre-Treatment

Cassava starch processing industry produces cassava pulp as a by-product or waste. In the well-known Duong Lieu village, this waste is released in surrounding environment without treatment causing serious environmental problems. The study aimed to (1) determine the Biomethane Potential (BMP) of the waste and to (2) find out if alkaline pre-treatment would improve it. Different cassava pulp samples were going through BMP test: untreated sample; pre-treated samples at different NaOH doses of 2, 6, 8 wt.% (dry weight-based) and pre-treated samples at different NaHCO3 doses of 2, 4, 6, 8 wt.% (dry weight based). BMP assays were conducted in 590mL bottles at 37oC for 40 days. As the result, BMP of the untreated waste was 281 NmLCH4/gVS and alkaline pretreatment increased BMP of the waste up to 479 mLCH4/gVS by treatment with NaOH 6 wt.% and 450 mLCH4/gVS by treatment with NaHCO3 6 wt.%. In addition, there was a significant reduction of lignin content of the substrate after alkaline pre-treatment. The results show that cassava pulp waste has moderate potential for biogas recovery. In addition, alkaline pre-treatment by either NaOH or NaHCO3 would significantly improve its BMP, possibly thanks to the reduction of lignin content.