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  • 1.
    Bajracharya, Suman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sarkar, Omprakash
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Krige, Adolf
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Chapter 12 - Advances in gas fermentation processes2022In: Current Developments in Biotechnology and Bioengineering: Advances in Bioprocess Engineering / [ed] Sirohi, Ranjna; Pandey, Ashok; Taherzadeh, Mohammad J.; Larroche, Christian, Elsevier, 2022, p. 321-351Chapter in book (Other academic)
    Abstract [en]

    Microbial metabolism enables the sustainable synthesis of fuels and chemicals from gaseous substrates (H2, CO, and CO2), thus drastically diminishing the carbon load in the atmosphere. Various value-added biochemicals and biofuels, such as acetate, methane, ethanol, butanol, butyrate, caproate, and bioplastics, have been produced during the conversion of syngas or H2/CO2, using a variety of microorganisms as biocatalysts. Gas fermentation processes using acetogenic and methanogenic organisms are being extensively investigated. This chapter provides an overview of microbial CO and CO2 conversion technology, with an emphasis on recent developments and integration with renewable electricity for the generation of H2 or other forms of electron donors. A discussion on technological challenges in gas fermentation addresses issues, such as poor mass transfer, low microbial biomass, and low productivity. It also presents possible solutions based on the latest advances in bioelectrochemical processes including microbial gas electrofermentation. Finally, the chapter includes a sustainability analysis of the process and includes a brief update on commercially established companies operating gas fermentation systems. Overall, an integrated approach combining gas fermentation and renewable electricity offers an opportunity for the development of CO and CO2- based biochemical and biofuel production at commercial scale.

  • 2.
    Chang, Young-Cheol
    et al.
    Course of Chemical and Biological Engineering, Division of Sustainable and Environmental Engineering, Muroran Institute of Technology, Hokkaido 050–8585, Japan; Department of Sciences and Informatics, Course of Chemical and Biological Systems, Muroran Institute of Technology, 27–1 Mizumoto, Muroran, 050–8585, Japan.
    Venkateswar Reddy, M.
    Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, Colorado 80523, USA.
    Suzuki, Hinako
    Department of Sciences and Informatics, Course of Chemical and Biological Systems, Muroran Institute of Technology, 27–1 Mizumoto, Muroran, 050–8585, Japan.
    Terayama, Takumi
    Course of Chemical and Biological Engineering, Division of Sustainable and Environmental Engineering, Muroran Institute of Technology, Hokkaido 050–8585, Japan.
    Mawatari, Yasuteru
    Course of Chemical and Biological Engineering, Division of Sustainable and Environmental Engineering, Muroran Institute of Technology, Hokkaido 050–8585, Japan; Department of Sciences and Informatics, Course of Chemical and Biological Systems, Muroran Institute of Technology, 27–1 Mizumoto, Muroran, 050–8585, Japan.
    Seki, Chigusa
    Course of Chemical and Biological Engineering, Division of Sustainable and Environmental Engineering, Muroran Institute of Technology, Hokkaido 050–8585, Japan; Department of Sciences and Informatics, Course of Chemical and Biological Systems, Muroran Institute of Technology, 27–1 Mizumoto, Muroran, 050–8585, Japan.
    Sarkar, Omprakash
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Characterization of Ralstonia insidiosa C1 isolated from Alpine regions: Capability in polyhydroxyalkanoates degradation and production2024In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 471, article id 134348Article in journal (Refereed)
  • 3.
    Iragavarapu, Gayathri Priya
    et al.
    Centre for Computational Natural Sciences and Bioinformatics (CCNSB), International Institute of Information Technology Hyderabad (IIIT-H), Hyderabad 500032, India.
    Imam, Syed Shahed
    Sreenidhi Institute of Science and Technology, Hyderabad 500029, India.
    Sarkar, Omprakash
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mohan, Srinivasula Venkata
    Bioengineering and Environmental Science Lab, Department of Energy and Environmental Engineering, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad 500007, India.
    Chang, Young-Cheol
    Course of Chemical and Biological Engineering, Muroran Institute of Technology, Muroran 0508585, Japan.
    Reddy, Motakatla Venkateswar
    Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO 80523, USA.
    Kim, Sang-Hyoun
    School of Civil and Environmental Engineering, Yonsei University, Seoul 03722, Republic of Korea.
    Amradi, Naresh Kumar
    Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742, USA.
    Bioprocessing of Waste for Renewable Chemicals and Fuels to Promote Bioeconomy2023In: Energies, ISSN 1996-1073, Vol. 16, no 9, article id 3873Article in journal (Refereed)
    Abstract [en]

    The world’s rising energy needs, and the depletion of fossil resources demand a shift from fossil-based feedstocks to organic waste to develop a competitive, resource-efficient, and low-carbon sustainable economy in the long run. It is well known that the production of fuels and chemicals via chemical routes is advantageous because it is a well-established technology with low production costs. However, the use of toxic/environmentally harmful and expensive catalysts generates toxic intermediates, making the process unsustainable. Alternatively, utilization of renewable resources for bioprocessing with a multi-product approach that aligns novel integration improves resource utilization and contributes to the “green economy”. The present review discusses organic waste bioprocessing through the anaerobic fermentation (AF) process to produce biohydrogen (H2), biomethane (CH4), volatile fatty acids (VFAs) and medium chain fatty acids (MCFA). Furthermore, the roles of photosynthetic bacteria and microalgae for biofuel production are discussed. In addition, a roadmap to create a fermentative biorefinery approach in the framework of an AF-integrated bioprocessing format is deliberated, along with limitations and future scope. This novel bioprocessing approach significantly contributes to promoting the circular bioeconomy by launching complete carbon turnover practices in accordance with sustainable development goals.

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  • 4.
    Kumar, A. Naresh
    et al.
    School of Civil and Environmental Engineering, Yonsei University, Seoul 03722, Republic of Korea; Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742, USA.
    Sarkar, Omprakash
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Chandrasekhar, K.
    School of Civil and Environmental Engineering, Yonsei University, Seoul 03722, Republic of Korea.
    Raj, Tirath
    School of Civil and Environmental Engineering, Yonsei University, Seoul 03722, Republic of Korea.
    Narishetty, Vivek
    School of Water, Energy, and Environment, Cranfield University, Cranfield MK43 0AL, UK.
    Mohan, S. Venkata
    Bioengineering and Environmental Sciences Lab, Department of Energy and Environmental Engineering, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India.
    Pandey, Ashok
    Centre for Innovation and Translational Research, CSIR-Indian Institute of Toxicology Research, Lucknow, India.
    Varjani, Sunita
    Gujarat Pollution Control Board, Gandhinagar, Gujarat 382010, India.
    Kumar, Sunil
    CSIR-National Environmental Engineering Research Institute (CSIR-NEERI), Nagpur 440 020, India.
    Sharma, Pooja
    CSIR-National Environmental Engineering Research Institute (CSIR-NEERI), Nagpur 440 020, India.
    Jeon, Byong-Hun
    Department of Earth Resources and Environmental Engineering, Hanyang University, Seoul 04763, Republic of Korea.
    Jang, Min
    Department of Environmental Engineering, Kwangwoon University, Seoul 01897, Republic of Korea.
    Kim, Sang-Hyoun
    School of Civil and Environmental Engineering, Yonsei University, Seoul 03722, Republic of Korea.
    Upgrading the value of anaerobic fermentation via renewable chemicals production: A sustainable integration for circular bioeconomy2022In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 806, part 1, article id 150312Article, review/survey (Refereed)
    Abstract [en]

    The single bioprocess approach has certain limitations in terms of process efficiency, product synthesis, and effective resource utilization. Integrated or combined bioprocessing maximizes resource recovery and creates a novel platform to establish sustainable biorefineries. Anaerobic fermentation (AF) is a well-established process for the transformation of organic waste into biogas; conversely, biogas CO2 separation is a challenging and cost-effective process. Biological fixation of CO2 for succinic acid (SA) mitigates CO2 separation issues and produces commercially important renewable chemicals. Additionally, utilizing digestate rich in volatile fatty acid (VFA) to produce medium-chain fatty acids (MCFAs) creates a novel integrated platform by utilizing residual organic metabolites. The present review encapsulates the advantages and limitations of AF along with biogas CO2 fixation for SA and digestate rich in VFA utilization for MCFA in a closed-loop approach. Biomethane and biohydrogen process CO2 utilization for SA production is cohesively deliberated along with the role of biohydrogen as an alternative reducing agent to augment SA yields. Similarly, MCFA production using VFA as a substrate and function of electron donors namely ethanol, lactate, and hydrogen are comprehensively discussed. A road map to establish the fermentative biorefinery approach in the framework of AF integrated sustainable bioprocess development is deliberated along with limitations and factors influencing for techno-economic analysis. The discussed integrated approach significantly contributes to promote the circular bioeconomy by establishing carbon-neutral processes in accord with sustainable development goals.

  • 5.
    Matsakas, Leonidas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sarkar, Omprakash
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Jansson, Stina
    Department of Chemistry, Umeå University, 901 87 Umeå, Sweden.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    A novel hybrid organosolv-steam explosion pretreatment and fractionation method delivers solids with superior thermophilic digestibility to methane2020In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 316, article id 123973Article in journal (Refereed)
    Abstract [en]

    Rising environmental concerns and the imminent depletion of fossil resources have sparked a strong interest towards the production of renewable energy such as biomethane. Inclusion of alternative feedstock’s such as lignocellulosic biomass could further expand the production of biomethane. The present study evaluated the potential of a novel hybrid organosolv-steam explosion fractionation for delivering highly digestible pretreated solids from birch and spruce woodchips. The highest methane production yield was 176.5 mLCH4 gVS−1 for spruce and 327.2 mL CH4 gVS−1 for birch. High methane production rates of 1.0–6.3 mL min−1 (spruce) and 6.0–35.5 mL min−1 (birch) were obtained, leading to a rapid digestion, with 92% of total methane from spruce being generated in 80 h and 95% of that from birch in 120 h. These results demonstrate the elevated potential of the novel method to fractionate spruce and birch biomass and deliver cellulose-rich pretreated solids with superior digestibility.

  • 6.
    Mohanakrishna, Gunda
    et al.
    Center for Energy and Environment, School of Advanced Sciences, KLE Technological University, Hubballi 580031, India.
    Sneha, Naik P.
    Center for Energy and Environment, School of Advanced Sciences, KLE Technological University, Hubballi 580031, India.
    Rafi, Shaik Mohammad
    Center for Energy and Environment, School of Advanced Sciences, KLE Technological University, Hubballi 580031, India.
    Sarkar, Omprakash
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Dark fermentative hydrogen production: Potential of food waste as future energy needs2023In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 888, article id 163801Article in journal (Refereed)
    Abstract [en]

    Globally, food waste (FW) is found to be one of the major constituents creating several hurdles in waste management. On the other hand, the energy crisis is increasing and the limited fossil fuel resources available are not sufficient for energy needed for emerging population. In this context, biohydrogen production approach through valorization of FW is emerging as one of the sustainable and eco-friendly options. The present review explores FW sources, characteristics, and dark fermentative production of hydrogen along with its efficiency. FW are highly biodegradable and rich in carbohydrates which can be efficiently utilized by anaerobic bacteria. Based on the composition of FW, several pretreatment methods can be adapted to improve the bioavailability of the organics. By-products of dark fermentation are organic acids that can be integrated with several secondary bioprocesses. The versatility of secondary products is ranging from energy generation to biochemicals production. Integrated approaches facilitate in enhanced energy harvesting along with extended wastewater treatment. The review also discusses various parameters like pH, temperature, hydraulic retention time and nutrient supplementation to enhance the process efficiency of biohydrogen production. The application of solid-state fermentation (SSF) in dark fermentation improves the process efficiency. Dark fermentation as the key process for valorization and additional energy generating process can make FW the most suitable substrate for circular economy and waste based biorefinery.

  • 7.
    Patel, Alok
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sarkar, Omprakash
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Valorization of volatile fatty acids derived from low-cost organic waste for lipogenesis in oleaginous microorganisms-A review2021In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 321, article id 124457Article, review/survey (Refereed)
    Abstract [en]

    To meet environmental sustainability goals, microbial oils have been suggested as an alternative to petroleum-based products. At present, microbial fermentation for oil production relies on sugar-based feedstocks. However, these substrates are costly, in limited supply, and present an elevated risk of contamination. Volatile fatty acids, which are generated as intermediates during anaerobic digestion of organic waste, could replace conventional sugar sources for microbial oil production. They comprise short-chain (C2 to C6) organic acids and are employed as building blocks in the chemical industry. The present review discusses the use of oleaginous microorganisms for the production of biofuels and added-value products starting from volatile fatty acids as feedstocks. The review describes the metabolic pathways enabling lipogenesis from volatile fatty acids, and focuses on strategies to enhance lipid accumulation in oleaginous microorganisms by tuning the ratios of volatile fatty acids generated via anaerobic fermentation.

  • 8.
    Saito, Kyo
    et al.
    Course of Chemical and Biological Engineering, Division of Sustainable and Environmental Engineering, Muroran Institute of Technology, 27-1 Mizumoto, Muroran 050-8585, Japan.
    Reddy, M. Venkateswar
    Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, CO 80523, USA.
    Sarkar, Omprakash
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Kumar, A. Naresh
    Department of Environmental Science and Technology, University of Maryland, College Park, MD 20742, USA.
    Choi, DuBok
    Faculty of Advanced Industry Convergence, Chosun University, Kwangju 61452, Republic of Korea.
    Chang, Young-Cheol
    Course of Chemical and Biological Engineering, Division of Sustainable and Environmental Engineering, Muroran Institute of Technology, 27-1 Mizumoto, Muroran 050-8585, Japan.
    Quantification of the Monomer Compositions of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Poly(3-hydroxyvalerate) by Alkaline Hydrolysis and Using High-Performance Liquid Chromatography2023In: Bioengineering, E-ISSN 2306-5354, Vol. 10, no 5, article id 618Article in journal (Refereed)
    Abstract [en]

    With the growing interest in bioplastics, there is an urgent need to develop rapid analysis methods linked to production technology development. This study focused on the production of a commercially non-available homopolymer, poly(3-hydroxyvalerate) (P(3HV)), and a commercially available copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)), through fermentation using two different bacterial strains. The bacteria Chromobacterium violaceum and Bacillus sp. CYR1 were used to produce P(3HV) and P(3HB-co-3HV), respectively. The bacterium Bacillus sp. CYR1 produced 415 mg/L of P(3HB-co-3HV) when incubated with acetic acid and valeric acid as the carbon sources, whereas the bacterium C. violaceum produced 0.198 g of P(3HV)/g dry biomass when incubated with sodium valerate as the carbon source. Additionally, we developed a fast, simple, and inexpensive method to quantify P(3HV) and P(3HB-co-3HV) using high-performance liquid chromatography (HPLC). As the alkaline decomposition of P(3HB-co-3HV) releases 2-butenoic acid (2BE) and 2-pentenoic acid (2PE), we were able to determine the concentration using HPLC. Moreover, calibration curves were prepared using standard 2BE and 2PE, along with sample 2BE and 2PE produced by the alkaline decomposition of poly(3-hydroxybutyrate) and P(3HV), respectively. Finally, the HPLC results obtained by our new method were compared using gas chromatography (GC) analysis.

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  • 9.
    Sarkar, Omprakash
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Antonopoulou, Io
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Xiros, Charilaos
    RISE Processum AB, SE-891 22, Örnsköldsvik, Sweden.
    Bruce, Ylva
    RISE Processum AB, SE-891 22, Örnsköldsvik, Sweden.
    Souadkia, Sarra
    RISE Processum AB, SE-891 22, Örnsköldsvik, Sweden.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Carbonic anhydrase assisted acidogenic fermentation of forest residues for low carbon hydrogen and volatile fatty acid production: enhanced in situ CO2 reduction and microbiological analysis2024In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270Article in journal (Refereed)
    Abstract [en]

    Carbonic anhydrase (CA) is considered an efficient enzyme for fermentation systems exhibiting a wide range of applications, enhancing both the efficacy and output of the fermentation process. The present study aimed to evaluate the production of acidogenic biohydrogen (bioH2) and volatile fatty acids (VFA) using forest residues as a renewable feedstock. Specifically, the study examined the integration of CA derived from Desulfovibrio vulgaris into the acidogenic fermentation (AF) process. The experimental procedure involved a cascade design conducted in two distinct phases. In phase I, the concentration of CA in the AF was systematically optimized, with glucose serving as the substrate. In phase II, three influential parameters (pH, pressurization with in situ generated gas and organic load) were evaluated on AF in association with optimized CA concentration from phase I. In phase II, glucose was replaced with renewable sugars obtained from forest residues after steam explosion pretreatment followed by enzymatic saccharification. The incorporation of CA in AF was found to be beneficial in steering acidogenic metabolites. Alkaline conditions (pH 8) promoted bioH2, yielding 210.9 mLH2 gCOD−1, while introducing CA further increased output to 266.6 mLH2 gCOD−1. This enzymatic intervention improved the production of bioH2 conversion efficiency (HCE) from 45.3% to 57.2%. Pressurizing the system accelerated VFA production with complete utilization of in situ produced H2 + CO2 compared to non-pressurized systems. Particularly, caproic acid production was improved under pressurized conditions which was accomplished by the targeted enrichment of chain-elongating bacteria in the mixed culture. The microbial diversity analysis showed the dominance of Firmicutes suggesting a significant degree of adaptation to the experimental contexts, leading to an enhanced production of acidogenic metabolites.

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  • 10.
    Sarkar, Omprakash
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ultrasound-controlled acidogenic valorization of wastewater for biohydrogen and volatile fatty acids production: Microbial community profiling2023In: iScience, E-ISSN 2589-0042, Vol. 26, no 4, article id 106519Article in journal (Refereed)
    Abstract [en]

    The present study explored the influence of ultrasound on acidogenic fermentation of wastewater for the production of biohydrogen and volatile fatty acids/carboxylic acids. Eight sono-bioreactors underwent ultrasound (20 kHz: 2W and 4W), with an ultrasound duration ranging from 15 min to 30 days, and the formation of acidogenic metabolites. Long-term continuous ultrasonication enhanced biohydrogen and volatile fatty acid production. Specifically, ultrasonication at 4W for 30 days increased biohydrogen production by 3.05-fold compared to the control, corresponding to hydrogen conversion efficiency of 58.4%; enhanced volatile fatty acid production by 2.49-fold; and increased acidification to 76.43%. The observed effect of ultrasound was linked to enrichment with hydrogen-producing acidogens such as Firmicutes, whose proportion increased from 61.9% (control) to 86.22% (4W, 30 days) and 97.53% (2W, 30 days), as well as inhibition of methanogens. This result demonstrates the positive effect of ultrasound on the acidogenic conversion of wastewater to biohydrogen and volatile fatty acid production.

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  • 11.
    Sarkar, Omprakash
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Modestra, Jampala Annie
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Waste-Derived Renewable Hydrogen and Methane: Towards a Potential Energy Transition Solution2023In: Fermentation, E-ISSN 2311-5637, Vol. 9, no 4, article id 368Article, review/survey (Refereed)
    Abstract [en]

    Anaerobic digestion (AD) is an environmentally friendly process for recovering low-carbon energy from the breakdown of organic substrates. In recent years, AD has undergone a major paradigm shift, and now the technology is not only considered as a “waste treatment” method and is instead viewed as a key enabler of the future “circular economy” with its potential for resource recovery (low-carbon energy, safe water, and nutrients). Currently, waste-derived biogas from AD is the most affordable and scalable source of renewable energy. Biomethane (upgraded biogas) can serve as a significant renewable and dispatchable energy source for combating the problem of global warming. Acidogenesis, an intermediate step of AD, can produce molecular hydrogen (H2) along with green chemicals/platform chemicals. The use of low-carbon hydrogen as a clean energy source is on the rise throughout the world, and is currently considered a potential alternative energy source that can contribute to the transition to a carbon-neutral future. In order to determine the future trade routes for hydrogen, nations are developing hydrogen policies, and various agreements. Hydrogen produced by biological routes has been found to be suitable due to its potential as a green energy source that is carbon neutral for the developing “Hydrogen Economy”. Recently, hydrogen blended with methane to a specific proportion and known as biohythane/hydrogen-enriched compressed natural gas (HCNG) has emerged as a promising clean fuel that can substantially contribute to an integrated net-zero energy system. This review provides an overview of the current state of fermentative hydrogen and methane production from biogenic waste/wastewater in a biorefinery approach and its utilization in the context of energy transition. The limitations and economic viability of the process, which are crucial challenges associated with biohydrogen/biomethane production, are discussed, along with its utilization.

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  • 12.
    Sarkar, Omprakash
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Continuous biohydrogen and volatile fatty acids production from cheese whey in a tubular biofilm reactor: Substrate flow rate variations and microbial dynamics2024In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 59, p. 1305-1316Article in journal (Refereed)
    Abstract [en]

    Three tubular bioreactors with a varied substrate flow rate of (2 mL/min, 5 mL/min, and 8 mL/min) were examined for 75 days. At 8 mL/min flow rate, the biohydrogen evolution was higher (3.88 mL H2/h), while its conversion efficiency was lower compared to 5 and 2 mL/min flow rate. The formation of volatile fatty acids and ammonium was also influenced by substrate flow rates. The volatile fatty acids production was slightly higher at 2 mL/min (12.74 ± 2.42 gCOD/L) and 5 mL/min (18.09 ± 2.01 gCOD/L) while, decreasing at 8 mL/min (11.85 ± 0.78 gCOD/L). Substrate flow rate significantly affected the pattern and composition of volatile fatty acids showing higher acetic acid, butyric and propionic acid production of 4.72 ± 1.46 gCOD/L (2 mL/min) 10.41 ± 0.91 gCOD/L (5 mL/min) and 1.78 ± 0.13 gCOD/L (5 mL/min). Continuous substrate input maintained the pH in the reactor due to replacement with fresh substrate, thereby controlling feedback inhibition and boosting metabolite production. Hydrogen-producing Firmicutes on the biofilm confirmed the pivotal role of the microbial community's significant contribution to converting waste to bioenergy. Overall, the present results support the use of a continuous operation mode for large-scale biohydrogen production. However, to ensure the efficacy of the system using waste or wastewater, low substrate flow rates are recommended.

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  • 13.
    Sarkar, Omprakash
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Effect of metals on the regulation of acidogenic metabolism enhancing biohydrogen and carboxylic acids production from brewery spent grains: Microbial dynamics and biochemical analysis2022In: Engineering in Life Sciences, ISSN 1618-0240, E-ISSN 1618-2863, Vol. 22, no 10, p. 650-661Article in journal (Refereed)
    Abstract [en]

    The present study reports the mixed culture acidogenic production of biohydrogen and carboxylic acids (CA) from brewery spent grains (BSG) in the presence of high concentrations of cobalt, iron, nickel, and zinc. The metals enhanced biohydrogen output by 2.39 times along with CA biosynthesis by 1.73 times. Cobalt and iron promoted the acetate and butyrate pathways, leading to the accumulation of 5.14 gCOD/L of acetic and 11.36 gCOD/L of butyric acid. The production of solvents (ethanol + butanol) was higher with zinc (4.68 gCOD/L) and cobalt (4.45 gCOD/L). A combination of all four metals further enhanced CA accumulation to 42.98 gCOD/L, thus surpassing the benefits accrued from supplementation with individual metals. Additionally, 0.36 and 0.31 mol green ammonium were obtained from protein-rich brewery spent grain upon supplementation with iron and cobalt, respectively. Metagenomic analysis revealed the high relative abundance of Firmicutes (>90%), of which 85.02% were Clostridium, in mixed metal-containing reactors. Finally, a significant correlation of dehydrogenase activity with CA and biohydrogen evolution was observed upon metal addition.

  • 14.
    Sarkar, Omprakash
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ethanol addition promotes elongation of short-chain fatty acids to medium-chain fatty acids using brewery spent grains as substrate2021In: Journal of Environmental Chemical Engineering, E-ISSN 2213-3437, Vol. 9, no 5, article id 105990Article in journal (Refereed)
    Abstract [en]

    The increasing environmental impact of fuels and chemicals from non-renewable fossil-based resources, as well as possible depletion of the latter, has spurred interest in sustainable alternatives. Fuels and chemicals can be produced in a carbon-neutral manner from renewable feedstock via biological processes. Short-and medium-chain fatty acids (SCCA and MCCA, respectively) have potential applications in the food, pharmaceutical, chemical, and biofuel industries. Microbial production of valuable elongated MCCA from SCCA requires an electron donor. The present study investigated the influence of ethanol as an electron donor for the mixed microbial fermentation of SCCA (C2-C5) and MCCA (C6) from brewery spent grains as feedstock. Chain elongation of SCCA to MCCA was evaluated under different ethanol concentrations (3, 6, 9, 12, 15, and 18 g/L) and compared with a non-ethanol control. Acidogenic fermentation successfully converted brewery spent grains to SCCA, reaching 19.66 gCOD/L (15 g/L ethanol supplementation) along with bio-hydrogen production of 41%. Accumulated SCCA were elongated to MCCA in a reverse β oxidation pathway to 9.1 gCOD/L of caproic acid (9 g/L ethanol). Ethanol consumption displayed a good correlation with MCCA formation, confirming the chain elongation capability of mixed cultures. Volatile solids were reduced by more than 70%. Continuous hydrolysis of the substrate with the release of sugars points to the beneficial role of mixed culture fermentation for the production of renewable fuels and chemicals.

  • 15.
    Sarkar, Omprakash
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Green hydrogen and platform chemicals production from acidogenic conversion of brewery spent grains co-fermented with cheese whey wastewater: adding value to acidogenic CO22022In: Sustainable Energy & Fuels, E-ISSN 2398-4902, Vol. 6, no 3, p. 778-790Article in journal (Refereed)
    Abstract [en]

    The biotechnological production of fuel and chemicals from renewable, organic carbon-rich substrates offers a sustainable way to meet the increasing demand for energy. This study aimed to generate platform chemicals, which serve as precursors for the synthesis of fuels and various materials, along with green hydrogen (bio-H2) by co-fermenting two different waste streams: brewery spent grains and cheese whey (CW). Reactors fermenting a fixed quantity of brewery-spent grains were loaded with CW at 20, 30, and 40 g COD per L, and microbial production of short-chain (SCCA) and medium-chain carboxylic acids (MCCA) along with bioH2 was assessed. The reactor with the highest organic load (40 g COD per L) produced the highest amount of SCCA (21.67 g L−1) whereas bio-H2 was with 30 g COD per L (181.35 mL per day). In the next phase, the generated gas (H2 + CO2) was continuously recirculated within the reactor to enhance SCCA production by a further 19.9%. In the later stages of fermentation, MCCA production indicated the occurrence of chain elongation from the accumulated lactic acid. Consumption of H2 and CO2 during gas recirculation highlighted the role of bio-H2 as an electron donor and acidogenic CO2 as a precursor molecule in the chain elongation process. As a result, no external reducing agent was required and only limited CO2 was released in the atmosphere, making the overall process more sustainable and cost-effective.

  • 16.
    Sarkar, Omprakash
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Influence of initial uncontrolled pH on acidogenic fermentation of brewery spent grains to biohydrogen and volatile fatty acids production: Optimization and scale-up2021In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 319, article id 124233Article in journal (Refereed)
    Abstract [en]

    This two-phase, two-stage study analyzed production of biohydrogen and volatile fatty acids by acidogenic fermentation of brewery spent grains. Phase-1 served to optimize the effect of pH (4–10) on acidogenic fermentation; whereas phase-2 validated the optimized conditions by scaling up the process to 2 L, 5 L, and 10 L. Alkaline conditions (pH 9) yielded excellent cumulative H2 production (834 mL) and volatile fatty acid recovery (8936 mg/L) in phase-1. Extended fermentation time (from 5 to 10 days) upgraded the accumulated short-chain fatty acids (C2–C4) to medium-chain fatty acids (C5–C6). Enrichment for acidogens in modified mixed culture improved fatty acid production; while their consumption by methanogens in unmodified culture led to methane formation. Increased CH4 but decreased H2 content enabled biohythane generation. Scaling up confirmed the role of pH and culture type in production of renewable fuels and platform molecules from brewery spent grains.

  • 17.
    Sarkar, Omprakash
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Organosolv Pretreated Birch Sawdust for the Production of Green Hydrogen and Renewable Chemicals in an Integrated Biorefinery Approach2022In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 344, no A, article id 126164Article in journal (Refereed)
    Abstract [en]

    Sustainable production of fuels and chemicals is the most important way to reduce the carbon footprint in the environment. Forest based abundant lignocellulosic biomass as a renewable feedstock can an attractive source of biofuels and biochemicals. This study evaluated the production of hydrogen (H2) along with platform chemicals from an organosol pretreated birch sawdust (SD). Acidogenic fermentation (AF) of pretreated SD resulted in production of green H2 (121.4 mL/gVS) along with short (17.8 g/L) and medium (2.64 g/L) chain carboxylic acids. Further integration of AF with anaerobic digestion (AD) in a biorefinery framework offered production of biomethane (bioCH4: 246 mL/gVS) from the leftover SD from AF. Integration of bioH2 with bioCH4 at different time interval of digestion showed 8-14 L biohythane formation ran with a H2 fraction of 1.6-0.3 H2/(H2+CH4) documenting energy content of 8-9.08 kJ/gVS.

  • 18.
    Sarkar, Omprakash
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Santosh, J.
    Department of Energy and Environmental Engineering CSIR—Indian Institute of Chemical Technology (CSIR—IICT), Hyderabad, India.
    Mohan, S. Venkata
    Department of Energy and Environmental Engineering CSIR—Indian Institute of Chemical Technology (CSIR—IICT), Hyderabad, India.
    Chang, Young-Cheol
    Chemical and Biological Engineering, Muroran Institute of Technology, Hokkaido, Japan.
    Waste-Derived Biohydrogen Enriched CNG/Biohythane: Research Trend and Utilities2023In: Biofuels: Technologies, Policies, and Opportunities / [ed] Rena, Sunil Kumar, Taylor & Francis, 2023, 1, p. 333-354Chapter in book (Other academic)
    Abstract [en]

    Global transportation demand has grown significantly because of rising urbanization and industrialization, together with a concentration of automobiles. The transportation industry's reliance on fossil fuels has increased concerns about sustainability and the environment. On the other side, climate change, global warming, and rising fuel prices have compelled us to seek alternative fuel production technologies in a sustainable manner. The development of renewable and low-carbon energy sources has gained momentum in response to growing petroleum shortages and the effects of greenhouse gas emissions on the planet. Hydrogen (H2)-blended methane (CH4)/compressed natural gas (CNG), which mimics hythane is emerging as an energy carrier for combustion engines due to its cost efficiency and energy reductions. Compared to methane, hythane can lower the emissions of carbon monoxide (CO) and oxides of nitrogen (NOx) up to 30% and 50% respectively. With economic and environmental benefits, hythane is expected to take a long journey, since the blend is in direct use with the existing vehicle engines and has been commercialized as vehicle fuel. Currently CNG is being enriched with H2 (H-CNG) to enhance combustion efficiency. Biogenic waste transformation to H-CNG as fuel has proven to be an emerging solution to enable this goal. Acidogenic fermentation coupled with anaerobic digestion can be a potential technology for the production of hydrogen and methane towards bioH2-CNG/biohythane production from biogenic waste/wastewater as feedstock. This chapter aims to provide an updated overview of the recent advances in biohythane/bioH2-CNG production and usage as fuel.

  • 19.
    Sravan, J. Shanthi
    et al.
    Research Center for Innovative Energy and Carbon Optimized Synthesis for Chemicals (Inn-ECOSysChem), Gwangju Institute of Science and Technology, Gwangju, 61005, Republic of Korea.
    Matsakas, Leonidas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Sarkar, Omprakash
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Advances in Biological Wastewater Treatment Processes: Focus on Low-Carbon Energy and Resource Recovery in Biorefinery Context2024In: Bioengineering, E-ISSN 2306-5354, Vol. 11, no 3, article id 281Article, review/survey (Refereed)
    Abstract [en]

    Advancements in biological wastewater treatment with sustainable and circularity approaches have a wide scope of application. Biological wastewater treatment is widely used to remove/recover organic pollutants and nutrients from a diverse wastewater spectrum. However, conventional biological processes face challenges, such as low efficiency, high energy consumption, and the generation of excess sludge. To overcome these limitations, integrated strategies that combine biological treatment with other physical, chemical, or biological methods have been developed and applied in recent years. This review emphasizes the recent advances in integrated strategies for biological wastewater treatment, focusing on their mechanisms, benefits, challenges, and prospects. The review also discusses the potential applications of integrated strategies for diverse wastewater treatment towards green energy and resource recovery, along with low-carbon fuel production. Biological treatment methods, viz., bioremediation, electro-coagulation, electro-flocculation, electro-Fenton, advanced oxidation, electro-oxidation, bioelectrochemical systems, and photo-remediation, are summarized with respect to non-genetically modified metabolic reactions. Different conducting materials (CMs) play a significant role in mass/charge transfer metabolic processes and aid in enhancing fermentation rates. Carbon, metal, and nano-based CMs hybridization in different processes provide favorable conditions to the fermentative biocatalyst and trigger their activity towards overcoming the limitations of the conventional process. The emerging field of nanotechnology provides novel additional opportunities to surmount the constraints of conventional process for enhanced waste remediation and resource valorization. Holistically, integrated strategies are promising alternatives for improving the efficiency and effectiveness of biological wastewater treatment while also contributing to the circular economy and environmental protection.

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  • 20.
    Velvizhi, G.
    et al.
    CO2 Research and Green Technology Centre, Vellore Institute of Technology, Vellore, 632014, India.
    Sarkar, Omprakash
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Bioengineering and Environmental Sciences Lab, Department of Energy and Environmental Engineering (DEEE), CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad, 500007, India.
    Rovira-Alsina, Laura
    LEQUiA. Institute of the Environment, University of Girona, Campus Montilivi, C/Maria Aurelia Capmany, 69, E-17003, Girona, Spain.
    Puig, Sebastià
    LEQUiA. Institute of the Environment, University of Girona, Campus Montilivi, C/Maria Aurelia Capmany, 69, E-17003, Girona, Spain.
    Mohan, S. Venkata
    Bioengineering and Environmental Sciences Lab, Department of Energy and Environmental Engineering (DEEE), CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad, 500007, India.
    Conversion of carbon dioxide to value added products through anaerobic fermentation and electro fermentation: A comparative approach2022In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 47, no 34, p. 15442-15455Article in journal (Refereed)
    Abstract [en]

    Increasing carbon footprint alters the carbon balance in nature, thereby worsening global climate change. The conversion of carbon dioxide (CO2) into value-added products through biological routes is the pathway of the future because of its ecological and sustainable character. The present study evaluated the conversion of CO2 into short-chain fatty acids (SCFA)/volatile fatty acids (VFA) and methane using four experimental conditions (R1-R4). The experimental conditions are R1 was an anaerobic fermenter (AF) operated as control, R2 consisted of an AF with electrodes operated in open circuit, R3 was an AF with electrodes operated in a closed circuit with 100 Ω as load and R4 was an electro-fermentation reactor with an applied cathodic potential of −0.8 V vs. Ag/AgCl. The results were assessed in terms of production of SCFA, methane, current density and inorganic carbon reduction. Electro-fermentation (R4) setup achieved the highest production of SCFA (2050 mg/L) and methane (41.2 mL/day) compared to other reactors. R3 reported 1800 mg/L and 24 mL/day, R2 reported 1560 mg/L and 15 mL/day and R1 reported 1430 mg/L and 10 mL/day of methane and SCFA production. The study-inferred that electro-fermentation could effectively catalyse the biochemical reactions and enhance the conversion of CO2 to organic compounds in a sustainable manner.

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