Panagiotis G. Kougias

Panagiotis G. Kougias
Hellenic Agricultural Organization - Demeter | ELGO · Soil and Water Resources Insitute - Thermi

PhD

About

111
Publications
63,034
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
4,028
Citations
Introduction
My research interests focus on agro-industrial waste treatment, anaerobic reactor configuration and design, optimization of the anaerobic processes, and development of sustainable solutions for organic waste and wastewater management. Currently, I am involved mainly in projects related to foaming in biogas plants, biogas upgrading, exploitation of grasses and fibers for biofuel production and deciphering the biogas microbiome using -omic technologies. Personal webpage: pkougias.com

Publications

Publications (111)
Article
Recently, a first comprehensive catalogue of microbial genomes populating biogas reactors treating manure and agro-industrial residues was determined by sequencing samples collected from 22 biogas reactors including laboratory and full scale. Among the archaeal community, one of the most abundant methanogens belongs to Methanoculleus genus and for...
Article
Biogas upgrading is envisioned as a key process for clean energy production. The current study evaluates the efficiency of different reactor configurations for ex-situ biogas upgrading and enhancement, in which externally provided hydrogen and carbon dioxide were biologically converted to methane by the action of hydrogenotrophic methanogens. The m...
Article
Full-text available
The process stability of biogas plants is often deteriorated by the accumulation of Long Chain Fatty Acids (LCFA). The microbial community shifts due to LCFA disturbances have been poorly understood as the molecular techniques used were not able to identify the genome characteristics of uncultured microorganisms, and additionally, the presence of l...
Article
Full-text available
Background Biogas production is an economically attractive technology that has gained momentum worldwide over the past years. Biogas is produced by a biologically mediated process, widely known as “anaerobic digestion.” This process is performed by a specialized and complex microbial community, in which different members have distinct roles in the...
Article
This research aimed to better characterize the biogas microbiome by means of high throughput metagenomic sequencing and to elucidate the core microbial consortium existing in biogas reactors independently from the operational conditions. Assembly of shotgun reads followed by an established binning strategy resulted in the highest, up to now, extrac...
Article
The concerns over food security and protein scarcity, driven by population increase and higher standards of living, have pushed scientists toward finding new protein sources. A considerable proportion of resources and agricultural lands are currently dedicated to proteinaceous feed production to raise livestock and poultry for human consumption. Th...
Article
Lactic acid is a valuable compound used in several industrial processes such as polymers, emulsifiers manufacturing, pharmaceutical, and cosmetic formulations. The present study aims to evaluate the potential use of food waste to produce lactic acid through fermentation, both by indigenous microbiota and by the bio-augmentation with two lactic acid...
Article
In this study, the effects of bioaugmentation of typically dominant hydrogenotrophic methanogens to CSTR co-digesting cheese whey and manure, under in-situ biomethanation operations were investigated. Reactors working at mesophilic (37°C) and thermophilic (55°C) conditions were independently treated and examined in terms of microbial composition an...
Article
Olive mill wastewater, a by-product of olive oil production after the operation of three-phase decanters, was used in a thermophilic anaerobic digester targeting efficient bioconversion of its organic load into biogas. An active anaerobic inoculum originating from a mesophilic reactor, was acclimatized under thermophilic conditions and was filled i...
Article
Full-text available
Biogas plants treating agricultural residues are associated with limited bioenergy output due to the high content of hardly degradable lignocellulosic fibers in the feedstock. Hence, effective treatment techniques are needed to enhance holocellulose deconstruction, and thus, increase the energy budget of anaerobic digestion (AD) process. In the pre...
Article
Four different types of ceramic gas distributors (Al2O3 of 1.2 μm and SiC of 0.5, 7 and 14 μm) were evaluated to increase biomethane formation during ex-situ biogas upgrading process. Each type of gas diffuser was tested independently at three different gas retention times of 10, 5 and 2.5 h, at thermophilic conditions. CH4 production rate increase...
Article
Biogas upgrading is an emerging technology offering unique opportunities for further exploitation of biomethane as fuel for vehicles or direct injection into the gas grid, expanding the conventional use of biogas for combined heat and electricity generation. Up to date, most of the studies exploring the potential of biological carbon dioxide hydrog...
Article
Anaerobic fermentation of various organic wastes to produce valuable intermediate products and generate a mixture of combustible gases has been researched actively in the past decades. For one, marine biomass as an abundant organic residue of water-locked countries has recently gained increasing popularity. However, such biomass is known to contain...
Article
This work presents an integrated biorefinery concept combining two biological platforms for the valorization of palm oil mill effluents and for simultaneous production of high market value products, such as microbial oils and bioenergy. Palm oil mill effluents were aerobically fermented to produce lipids and subsequently the effluent from the ferme...
Article
Co-digestion with lipid-rich substrates is a likely strategy in biogas plants, due to their high energy content. However, the process stability is vulnerable to inhibition due to the sudden increase of fatty-acid concentration. Therefore, techniques that promote the adaptation of the microorganisms to the presence of lipids have been proposed. In t...
Article
The aim of this work was to provide solid proofs regarding the achievement of “steady-state conditions”, which means that the performance of the anaerobic digester is representative of the applied environmental conditions. For this reason, we investigated how, starting from different inoculum sources (i.e., municipal wastewater treatment, bio-waste...
Article
Gas fermentation for the production of building block molecules and biofuels is lately gaining attention as a means to eliminate the greenhouse gases emissions. Especially CO2 capture and recycling are in focus. Thus, the biological coupling of CO2 and H2 is of high interest. Therefore, the focus of the present work was to evaluate the performances...
Preprint
Full-text available
Methane production by microbes is a hot topic - Literally. Because of the potential to cause global warming, increased methane production is of great concern, but if properly controlled, it can also boost energy generation. Unfortunately, the basic mechanisms through which microbes generate methane remain unclear. To provide some clarity, researche...
Article
Full-text available
Background: Microorganisms in biogas reactors are essential for degradation of organic matter and methane production. However, a comprehensive genome-centric comparison, including relevant metadata for each sample, is still needed to identify the globally distributed biogas community members and serve as a reliable repository. Results: Here, 134...
Article
Full-text available
Methanogenesis, a biological process mediated by complex microbial communities, has attracted great attention due to its contribution to global warming and potential in biotechnological applications. The current study unveiled the core microbial methanogenic metabolisms in anaerobic vessel ecosystems by applying combined genome-centric metagenomics...
Article
Human waste (HW) poses environmental and public health risk, thereby its sustainable management is becoming a serious growing challenge. Anaerobic digestion (AD) has long been introduced as an environmental-friendly and sustainable waste management technology with bio-methane as final product. Energy production via AD of HW would significantly cont...
Preprint
Full-text available
Background Microorganisms in biogas reactors are essential for degradation of organic matter and methane production. However, a comprehensive genome-centric comparison, including relevant metadata for each sample, is still needed to identify the globally distributed biogas community members and serve as a reliable repository. Results Here, 134 publ...
Preprint
Full-text available
Background Microorganisms in biogas reactors are essential for degradation of organic matter and methane production. However, a comprehensive genome-centric comparison, including relevant metadata for each sample, is still needed to identify the globally distributed biogas community members and serve as a reliable repository. Results Here, 134 publ...
Article
Full-text available
The lipolytic oleaginous yeast Yarrowia lipolytica was used in the bioaugmentation and biovalorization of oily industrial wastes during successive‐batch fermentation. Five cycles of non‐sterile successive‐batch fermentation with 70 % medium replacement achieved the highest oil removal of 68.1±5.60 % and produced biomass and lipid yields of 0.213±0....
Preprint
Full-text available
Background: Microorganisms in biogas reactors are essential for degradation of organic matter and methane production.. However, a comprehensive genome-centric comparison, including relevant metadata for each sample, is still needed to identify the globally distributed biogas community members and serve as a reliable repository. Results: Here, 134 p...
Article
Full-text available
Biogas production from anaerobic digestion of grass was evaluated in this study taking into account two harvesting machines, i.e., a Disc-mower and an Excoriator, under diverse operating conditions. In addition, the application of generated biogas either in a Combined Heat and Power (CHP) plant for thermal and electrical energy production or as tra...
Article
This work investigated the thermophilic (55 °C) co-digestion performance both in batch and continuous mode operation. The biochemical methane potentials of L. digitata and cattle manure were 308 ± 24 and 203 ± 33 mL CH4/g VS, respectively. The optimum co-digestion feedstock ratio was found to be 80% macroalgae: 20% manure on a volatile solids basis...
Chapter
Biogas production is a well-established process for energy generation, nutrient recovery, and valorization of organic residues. Typically, the biogas is composed of methane, carbon dioxide, and other impurities. The removal or transformation of carbon dioxide (biogas upgrading) and the purification from other contaminants (biogas cleaning) are esse...
Article
This study investigates the efficiency in methane production of lab-scale mesophilic (37 °C) and thermophilic (54 °C) continuous stirred tank reactors fed with cheese whey at different operational conditions. Results showed that whey mono-digestion was feasible at mesophilic conditions, while at thermophilic conditions frequent acidification incide...
Article
In typical anaerobic digestion (AD) systems, the microbial functional assertion is hampered by synchronised versatile metabolism required for heterogeneous substrates degradation. Thus, the intricate methanogenic process from organic compounds remains an enigma after decades of empirical operation. In this study, simplified AD microbial communities...
Article
This work investigated the thermophilic (55 °C) co-digestion performance both in batch and continuous mode operation. The biochemical methane potentials of L. digitata and cattle manure were 308 ± 24 and 203 ± 33 mL CH4/g VS, respectively. The optimum co-digestion feedstock ratio was found to be 80% macroalgae: 20% manure on a volatile solids basis...
Article
The anaerobic digestion (AD) of municipal biopulp with two macroalgal biomasses (i.e. Saccharina latissima and Fucus serratus) was investigated at batch and continuously fed digesters at thermophilic conditions (54 ± 1 °C). At batch mono-digestion tests, municipal biopulp was associated with significantly higher methane production (549 ± 9 mLCH 4 /...
Article
This study evaluated the process performance and determined the microbial community structure of two lab-scale thermophilic trickling biofilter reactors used for biological methanation of hydrogen and carbon-dioxide for a total period of 94 days. Stable and robust operation was achieved by means of a single-pass gas flow. The quality of the output...
Article
Full-text available
Background: The expansion of renewable energy produced by windmills and photovoltaic panels has generated a considerable electricity surplus, which can be utilized in water electrolysis systems for hydrogen production. The resulting hydrogen can then be funneled to anaerobic digesters for biogas upgrading (biomethanation) purposes (power-to-methan...
Article
Lignocellulosic substrates are associated with limited biodegradability due to the structural complexity. For that reason, a pretreatment step is mandatory for efficient biomass transformation which will lead to increased bioenergy output. The aim of the present study was to assess the efficiency of two pretreatment machines to enhance the methane...
Article
A mixture of piggery slurry and algal species (mainly composed of Nannochloropsis limnetica), grown in municipal wastewater, were used as substrates for biogas production. Mono- and co-digestion experiments were performed at batch and continuous reactor operation. The mono-digestion of wastewater microalgae led to the highest methane yield (408 ± 3...
Article
The paper can be downloaded for free until June 22, 2018 from this link: https://authors.elsevier.com/c/1W~dvin8VSLJc---------------------------------------------------------------------------------------------------------------- The aim of this study is to propose a hybrid biogas upgrading configuration composed of two-stage thermophilic reactors...
Article
The mechanisms by which specific anaerobic microorganisms remain firmly attached to lignocellulosic material, allowing them to efficiently decompose organic matter, have yet to be elucidated. To circumvent this issue, microbiomes collected from anaerobic digesters treating pig manure and meadow grass were fractionated to separate the planktonic mic...
Article
Full-text available
Dilution is considered to be a fast and easily applicable pretreatment for anaerobic digestion (AD) of chicken manure (CM), however, dilution with fresh water is uneconomical because of the water consumption. The present investigation was targeted at evaluating the feasibility and process performance of AD of CM diluted with algal digestate water (...
Article
A novel biological process to upgrade biogas was developed and optimised during the current study. In this process, CO2 in the biogas and externally provided H2 were fermented under mesophilic conditions to volatile fatty acids (VFAs), which are building blocks of higher-value biofuels. Meanwhile, the biogas was upgraded to biomethane (CH4 >95%), w...
Preprint
Full-text available
The mechanisms by which specific anaerobic microorganisms remain firmly attached to lignocellulosic material allowing them to efficiently decompose the organic matter are far to be elucidated. To circumvent this issue, the microbiomes collected from anaerobic digesters treating pig manure and meadow grass were fractionated to separate the planktoni...
Article
Microbial dynamics in an upgrading biogas reactor system undergoing a more than two years-period at stable operating conditions were explored. The carbon dioxide generated during biomass degradation in the first reactor of the system was converted to methane into the secondary reactor by addition of external hydrogen. Considering the overall effici...
Article
Biogas upgrading via carbon dioxide hydrogenation is an emerging technology for electrofuel production. The biomethanation efficiency is strongly dependent on a balanced microbial consortium, whose high-resolution characterization along with their functional potential and interactions are pivotal for process optimization. The present work is the fi...
Article
Full-text available
Biogas production is a well-established technology primarily for the generation of renewable energy and also for the valorization of organic residues. Biogas is the end product of a biological mediated process, the so called anaerobic digestion, in which different microorganisms, follow diverse metabolic pathways to decompose the organic matter. Th...
Article
The aim of this work was to elucidate the microbial ecology in twelve mesophilic and thermophilic full-scale biogas plants using a genome-centric metagenomic approach. In this study both biogas plants treating manure and those treating sludge from waste water treatment plants were considered. The identification of 132 Metagenome-Assembled Genomes (...
Article
Full-text available
The present research is the first comprehensive study regarding the thermophilic anaerobic degradation of cheese wastewater, which combines the evaluation of different reactor configurations (i.e. single and two-stage continuous stirred tank reactors) on the process efficiency and the in-depth characterization of the microbial community structure u...
Article
Full-text available
In the past few years, many studies investigated the anaerobic digestion microbiome by means of 16S rRNA amplicon sequencing. Results obtained from these studies were compared to each other without taking into consideration the followed procedure for amplicons preparation and data analysis. This negligence was mainly due to the lack of knowledge re...
Article
Biogas production is an established sustainable process for simultaneous generation of renewable energy and treatment of organic wastes. The increasing interest of utilizing biogas as substitute to natural gas or its exploitation as transport fuel opened new avenues in the development of biogas upgrading techniques. The present work is a critical r...
Article
Biogas upgrading processes by in-situ hydrogen (H2) injection are still challenging and could benefit from a mathematical model to predict system performance. Therefore, a previous model on anaerobic digestion was updated and expanded to include the effect of H2 injection into the liquid phase of a fermenter with the aim of modeling and simulating...
Article
CO is a main component of syngas, which can be produced from the gasification of organic wastes and biomass. CO can be converted to methane by anaerobic digestion (AD), however, it is still challenging due to its toxicity to microorganisms and limited knowledge about CO converting microorganisms. In the present study, anaerobic granular sludge (AGS...
Article
The application of thermophilic conditions in anaerobic digesters leads to higher methane production rates and better sanitation of the effluents compared to mesophilic operation. However, an increase in operational temperature is challenging due to the tremendous selective pressure imposed on the microbial consortium. The adaptation of microbial c...
Article
Meadow grass has recently gained increased attention as a substrate for full-scale biogas reactors. However, to increase its biodegradability, pretreatment is needed. In the present work, different harvesting machines were compared in order to assess their effect on biogas production. Specifically, a Disc-mower, an Excoriator and a Chopper were use...
Article
This study evaluates the efficiency of four novel up-flow reactors for ex-situ biogas upgrading converting externally provided CO2 and H2 to CH4, via hydrogenotrophic methanogenesis. The gases were injected through stainless steel diffusers combined with alumina ceramic sponge or through alumina ceramic membranes. Pore size, input gas loading and g...