Jerry D Murphy

University College Cork | UCC · Environmental Research Institute

Integrating microbial electrolysis cells and anaerobic digestion (MEC-AD) improves upon conventional anaerobic digestion for biomethane production due to the in-situ provision of electrochemically produced reducing power (such as hydrogen). However, the electron transfer behaviour at the microbe-electrode interface remains unclear. This study asses...

Biorefinery approaches can be utilised at distilleries using dark fermentation to treat whiskey production byproducts and provide decarbonisation opportunities. A biorefinery can convert residues to hydrogen, carbon dioxide and volatile fatty acids (VFAs). This study investigated the effect of organic loading rate (OLR) on the production of VFAs an...

Decarbonisation of industry will necessitate innovative technological solutions that allow for both reduced carbon footprint and security of supply. Biogas systems can allow electricity production on-demand. This study evaluated and compared different two-phase anaerobic digestion systems for continuous volatile fatty acid (VFAs) production and dem...

Hydrogen will play an indispensable role as both an energy vector and as a molecule in essential products in the transition to climate neutrality. However, the optimal sustainable hydrogen production system is not definitive due to challenges in energy conversion efficiency, economic cost, and associated marginal abatement cost. This review summari...

Aviation is the most energy and carbon intensive mode of transport and the most difficult to decarbonise. Greenhouse gas emissions from aviation comprise around 2 % of global totals. The low energy density of current battery technologies presents significant technical challenges for use in the aviation sector. This study compares two use cases of d...

This book provides comprehensive insights on existing technologies and up-to-date advances in the field of waste management and treatment using algal-based technologies via different approaches and systems. Coverage includes: Process fundamentals of algae-based wastewater treatment, including metabolic modelling, algal species for resource recovery...

On-farm feedstocks such as grass silage and cattle slurry present recalcitrant characteristics that can limit microbial conversion in biofuel production. Introducing a biochar supplement in two-stage anaerobic digestion may facilitate feedstock hydrolysis and improve energy yields in biohydrogen and biomethane production. The biomethane potentials...

Grass silage and cattle slurry are the most abundant feedstocks for biogas in an Irish context. This work describes how to optimize their biomethane yield. Hydrolysis and biomethane yields from co-digestion of grass silage and slurry were enhanced in a biochar-supplemented two-stage digestion process. Biochar addition at the optimal dosage of 10 g/...

Future energy systems necessitate dispatchable renewable energy to balance electrical grids with high shares of intermittent renewables. Biogas from anaerobic digestion (AD) can generate electricity on-demand. High-rate methanogenic reactors, such as the Upflow Anaerobic Sludge Blanket (UASB), can react quicker to variations in feeding as compared...

The by-products generated from the whiskey distillation process consist of organic liquids with a high chemical oxygen demand (COD) and residues with a high solid content. Low-carbon strategies that repurpose and valorize such by-products are now imperative to reduce the carbon footprint of the food and beverage industries. The operation of a two-p...

Agriculture is considered a hard to abate sector in which 2050 net-zero greenhouse gas (GHG) emissions targets will be challenging. Anaerobic digestion is a technology that can reduce agricultural emissions whilst producing renewable energy and a biofertiliser. In Ireland this technology was previously evaluated to be a high cost of abatement solut...

The valorisation of whiskey by-products was assessed and compared in three anaerobic digestion systems. The systems produced similar methane yields, which could satisfy up to 44% of the thermal energy demand at a distillery. Using methane generated from by-products would displace natural gas and reduce the distillery's carbon footprint. Two-phase s...

On-farm anaerobic digestion plants served by virtual biomethane pipelines may be used in areas with no gas grid infrastructure access to improve manure (slurry) management and to produce and deliver renewable gas. A modelling analysis of a simulated virtual biomethane pipeline is presented whereby gas is collected from 100 on-farm biogas plants fed...

This work aims to assess the potential biogas resource of by-products from the production of distilled spirits at 9 operational distilleries in 7 countries. An additional objective was the calculation of the energy resource and Scope 1 greenhouse gas (GHG) emission savings from the use of 21 by-products from the distilleries as a feedstock for anae...

Biomethane is a viable alternative to natural gas and diesel for decarbonising hard-to-abate sectors such as agriculture, industry and heavy transport. Unlike conventional biogas upgrading, photosynthetic biogas upgrading cogenerates biomethane, biofertiliser and microalgal bioproducts with the potential to improve resource utilisation and process...

Biomethane from anaerobic digestion of agricultural feedstock is a versatile energy vector for decarbonising agriculture, heavy transport and heat. To lower costs and increase the emission-savings potential, photosynthetic biogas upgrading, cogenerating microalgae with biomethane is investigated here. In a first-of-its-kind work, this paper reports...

Uncertainty surrounding the total cost of ownership, system costs, and life cycle environmental impacts means that stakeholders may lack the required information to evaluate the risks of transitioning to low-carbon fuels and powertrains. This paper assesses the life cycle costs and well-to-wheel environmental impacts of using electricity and electr...

Decarbonising economies and improving environment can be enhanced through circular economy, energy, and environmental systems integrating electricity, water, and gas utilities. Hydrogen production can facilitate intermittent renewable electricity through reduced curtailment of electricity in periods of over production. Positioning an electrolyser a...

Increased biogas production from increasing numbers of anaerobic digestion (AD) facilities has increased the mass of digestate applied to agricultural land close to AD plants and has led to an oversupply in some regions. This necessitates long distance digestate transportation accompanied by economic, environmental, and social drawbacks. This work...

Decarbonisation pathways for the food and beverage sector are focused at a national, regional, or sectoral level. There is a lack of literature which assesses decarbonisation pathways at a facility level and which compares pathways using Multi-criteria Decision Analysis (MCDA). This work assesses the economic and environmental performance of 21 dec...

Globally, 10% of milk production occurs in countries whereby dairy livestock have pasture access for the majority of the year, leading to the seasonal collection and availability of dairy slurry. This can pose challenges if dairy slurry is used as a feedstock in on-farm biogas plants. On-farm biogas plants may also have no grid access and have to f...

To achieve the Net-Zero Emissions goal by 2050, a major upscale in green hydrogen needs to be achieved; this will also facilitate use of renewable electricity as a source of decarbonised fuel in hard-to-abate sectors such as industry and transport. Nearly 80% of the world's offshore wind resource is in waters deeper than 60 m, where bottom-fixed wi...

Microbial chain elongation fermentation is an alternative technology for medium-chain fatty acid (MCFA) production. This paper proposed the addition of pyrochar and graphene in chain elongation to improve MCFA production using ethanol and acetate as substrates. Results showed that the yield of, and selectivity towards, n-caproate were significantly...

Using renewable biogas from the anaerobic digestion of distillery by-products as a low-carbon heat source can decarbonize the distillery process and support the distillery industry to transition to a more sustainable production process. This study investigated the anaerobic digestion performance of different types of whiskey by-products and the eff...

Anaerobic digestion (AD) is a bioprocess technology that integrates into circular economy systems, which produce renewable energy and biofertilizer whilst reducing greenhouse gas emissions. However, improvements in biogas production efficiency are needed in dealing with lignocellulosic biomass. The state-of-the-art of AD technology is discussed, wi...

Seaweed is considered a third-generation biomass feedstock for transport biofuel with great potential for bioenergy and biorefinery applications. Microwave-assisted hydrothermal carbonization (HTC) offers a conversion route for seaweed valorization to multiple value-added products. However, the HTC products (such as hydrochar and process liquor) ar...

Optimising biogas upgrading with microalgae in a combined bubble column-photobioreactor setup is at a low technology readiness. Most of the prior studies investigated the optimisation of the overall system and generated variable results. The approach employed here is to optimise the individual components of the system to achieve definitive conclusi...

The utilization of low-cost and abundant lignocellulosic residues for sustainable production of bioenergy and biofuels (such as biogas) will play a pivotal role in the future decarbonized circular economy energy supply. Among all of the bioconversion technologies for the production of bioenergy and biofuels, anaerobic digestion (AD) has many advant...

This is an IEA Bioenergy, Task 37 report, addressing biogas, or biomethane, used in the transport sector. The report summarizes essential information on technology, economics, sustainability transitions, policy, and sustainability performance. The concluding chapter is a summary for policy makers

A methodology was developed to determine the location and biomethane potential of on-farm biomass feedstocks and furthermore, the quantity of this biomass situated away from an existing gas grid network. The development of decentralised systems which can be integrated with large industry in such locations offers a potential alternative deployment o...

The efficiency of microbial interspecies electron transfer between syntrophic bacteria and methanogens is considered a rate-limiting factor for the overall efficiency of anaerobic digestion (AD). Stimulating interspecies electron transfer by biochars has been demonstrated to be efficient to enhance AD. However, the enhancing effects vary significan...

Ex-situ biomethanation (CO 2 + 4H 2 → CH 4 + 2H 2 O) can simultaneously achieve renewable electricity storage and CO 2 valorisation. However, fluctuations in variable renewable electricity may lead to intermittent hydrogen supply, which is shown to adversely affect microbial activity and performance of the biomethanation process. Carbonaceous mater...

Renewable gas has been proposed as a solution to decarbonise industrial processes, specifically heat demand. As part of this effort, the breast-milk substitutes industry is proposing to use renewable gas as a substitute for fossil natural gas. However, decarbonising the industrial processing of breast-milk substitutes can increase social license fo...

The need to reduce the climate impact of the transport sector has led to an increasing interest in the utilisation of alternative fuels. Producing advanced fuels through the integration of anaerobic digestion and power-to-fuel technologies may offer a solution to reduce greenhouse gas emissions from difficult to decarbonise modes of transport, such...

Presently more energy is sourced from the natural gas grid than the electricity grid in the EU and the US. Furthermore hard-to-abate sectors such as heavy-duty transport are not readily served by electricity. Decarbonised energy systems will require renewable fuels (such as biomethane) to reduce the reliance on fossil-based diesel and natural gas....

The effects of steam and sulfuric acid pretreatment on anaerobic digestion (AD) of whiskey byproducts (including draff, thin and thick stillage) were investigated in order to improve the digestion performance under both mesophilic and thermophilic temperatures. The results of biomethane potential assays suggested that thermophilic AD facilitated th...

The anaerobic digestion (AD) of distillery by-products presents benefits such as greenhouse gas (GHG) emission savings and electricity savings, as well as drawbacks such as reduced animal feed and protein production and the potential import of animal feeds. This work balances these benefits and drawbacks using compromise programming (CP). The best...

Fermentative production of biohydrogen and volatile fatty acids (VFAs) from advanced feedstocks such as seaweed provides opportunities in the carbon-neutral bioeconomy. The gap in the state of the art exists in overcoming both the low fermentation efficiency associated with the rigid structure of seaweed and the inefficient metabolic electron trans...

Anaerobic digestion (AD) of organic waste to produce biogas is a mature biotechnology commercialised for decades. However, the relatively recent discovery of direct interspecies electron transfer (DIET) brings a new opportunity to improve the efficiency of biogas technology. DIET may replace mediated interspecies electron transfer (MIET) by efficie...

Biomethane is suggested as an advanced biofuel for the hard-to-abate sectors such as heavy transport. However, future systems that optimize the resource and production of biomethane have yet to be definitively defined. This paper assesses the opportunity of integrating anaerobic digestion (AD) with three emerging bio-electrochemical technologies in...

Studies attempting to optimise photosynthetic biogas upgrading by simultaneous investigation of the bubble column-photobioreactor setup have experienced considerable variability in results and conclusions. To identify the sources of such variation, this work quantitatively compared seven design factors (superficial gas velocity; liquid to gas flow...

The two-step bubble column-photobioreactor photosynthetic biogas upgrading system can enable simultaneous production of biomethane and value-added products from microalgae. However, due to the influence of a large number of variables, including downstream processes and the presence of microalgae, no unanimity has been reached regarding the performa...

(max. 200 words) This study investigated the application of a conductive material, granular activated carbon (GAC), as an approach to improve anaerobic lipid degradation and methane production. Anaerobic biomethane potential (BMP) assays were performed in 120 ml batch anaerobic digestion (AD) vials using 5 gVS/L anaerobic sludge as inoculum. Differ...

The high environmental impacts of transport mean that there is an increasing interest in utilising low-carbon alternative energy carriers and powertrains within the sector. While electricity has been mooted as the energy carrier of choice for passenger vehicles, as the mass and range of the vehicle increases, electrification becomes more difficult....

Bioelectrochemical technologies such as electro-fermentation and microbial CO2 electrosynthesis are emerging interdisciplinary technologies that can produce renewable fuels and chemicals (such as carboxylic acids). The benefits of electrically driven bioprocesses include improved production rate, selectivity, and carbon conversion efficiency. Howev...

In the transition to a climate neutral future, the transportation sector needs to be sustainably decarbonized. Producing advanced fuels (such as biomethane) and bio-based valorised products (such as pyrochar) may offer a solution to significantly reduce greenhouse gas (GHG) emissions associated with energy and agricultural circular economy systems....

The need to reduce global greenhouse gas (GHG) emissions may require the use of renewable gaseous fuels in the food and beverage industry to decarbonise processes that are difficult to electrify such as whiskey distillation. Large companies report their GHG emissions according to the Greenhouse Gas Protocol in terms of direct and indirect GHG emiss...

Grass represents a major renewable feedstock in temperate climate zones, but its efficient utilization is challenging in biorefineries and advanced biofuels due to its structural recalcitrance. Here hydrothermal hydrolysis (100–180°C, for up to 40 min duration) was investigated to improve sugar yields from grass silage. The optimal conditions (140°...

By-product and residue management are significant economic and environmental considerations in whiskey production. Incorporation of sustainable production methods in the industry can reduce costs in the areas of energy consumption and waste disposal and lessen environmental impacts via reduced greenhouse gas emissions. Circular economy opportunitie...

Production of biomethane from distillery by-products (such as stillage) in a circular economy system may facilitate a climate neutral alcohol industry. Anaerobic digestion (AD) of easily degradable substrates can lead to rapid acidification and accumulation of intermediate volatile fatty acids, reducing microbial activity and biomethane production....

Advanced biofuels include biomass sources free from land use such as seaweed. Seaweed biomethane may contribute significantly to a climate-neutral transport future; however, seaweed has limited biodegradability via anaerobic digestion (AD). To address this issue, the authors proposed a cascading circular bioenergy system incorporating pyrolysis (Py...

Low-carbon circular economy strategies within the whiskey industry necessitate minimal use of fossil-based energy including heat and electricity. Renewable energy generated from process by-products such as draff and pot ale offers opportunities for circular bioeconomy systems. However, such a system is yet to be defined and assessed in detail. In t...

Accommodating renewables on the electricity grid may hinder development opportunities for offshore wind farms (OWFs) as they begin to experience significant curtailment or constraint. However, there is potential to combine investment in OWFs with Power-to-Gas (PtG), converting electricity to hydrogen via electrolysis for an alternative/complementar...

Stimulating direct interspecies electron transfer with conductive materials is a promising strategy to overcome the limitation of electron transfer efficiency in syntrophic methanogenesis of industrial wastewater. This paper assessed the impact of conductive foam nickel (FN) supplementation on the syntrophic methanogenesis and found that addition o...

With the growth of anaerobic digestion (AD) for biogas production, associated increasing digestate production may cause environmental problems if the increasing agricultural land required for digestate application is limited. An alternative is to valorise the digestate. Microwave assisted low-temperature hydrothermal treatment (MLHT; temperature 10...

The operation of power-to-X systems requires measures to control the cost and sustainability of electricity purchased from spot markets. This study investigated different bidding strategies for the day-ahead market with a special focus on Sweden. A price independent order (PIO) strategy was developed assisted by forecasting electricity prices with...

This article assesses the impact of the energy recovery from the digestate on the economics of biomethane produced from the organic fraction of municipal solid waste. Six waste-to-energy routes are investigated and assumed to be deployed in the regional context of the Republic of Ireland. Anaerobic digestion without energy recovery, and landspreadi...

Synergistic opportunities to combine biomethane production via anaerobic digestion whilst cultivating microalgae have been previously suggested in literature. While biomethane is a promising and flexible renewable energy vector, microalgae are increasingly gaining importance as an alternate source of food and/or feed, chemicals and energy for advan...

The marine macro-alga Laminaria digitata is an abundant brown seaweed, which may be used as a feedstock for gaseous biofuel production via sequential dark fermentation and anaerobic digestion. Various methods, including hydrothermal pretreatment (HTP), hydrothermal dilute acid pretreatment (HTDAP), enzymolysis, and combinations thereof, were employ...

Biomass pretreatments represent a necessary route to overcome the natural physico-chemical barriers of recalcitrant feedstocks. However, current biomass pretreatments generally result in generation of various inhibitors (such as furfural derived from pentose), which could inhibit cell growth and decrease biofuel productivity. This study aims to und...

Marine macroalgae (seaweed) is a promising feedstock for producing biohydrogen and biomethane via dark fermentation and anaerobic digestion, respectively. However, one of the limiting steps in the biological process is the conversion of polymeric carbohydrates into monomeric sugars. Here hydrothermal pretreatments were assessed for hydrolysis and s...

Photosynthetic biogas upgrading using microalgae provides a promising alternative to commercial upgrading processes as it allows for carbon capture and re-use, improving the sustainability of the process in a circular economy system. A two-step absorption column-photobioreactor system employing alkaline carbonate solution and flat plate photobiorea...

As biogas from anaerobic digestion becomes an increasingly attractive biofuel, the need to improve the quality of biogas has come to the fore. Biological upgrading focuses on adding enough hydrogen to an anaerobic biogas reactor to allow methanation of the remaining carbon dioxide by methanogenic Archaea ( in situ upgrading). Alternatively, biogas...

This study investigated in-situ and ex-situ biological methanation strategies for biogas upgrading potential. The addition and circulation of hydrogen with a ceramic gas diffuser unit revealed positive effects on the methanogenic process. A short-term maximum methane productivity of 2.5 L CH4 per L reactor volume per day (LVR⁻¹ d⁻¹) was obtained in...

The levelized cost of energy of biomethane from food waste was assessed at 87 €/MWh, (87 c/L diesel equiv ). Allowing for gate fees the incentive required for financial viability was 0.13 €/m ³ (13 €/MWh). For context, various successful renewable energy policies were analysed across the EU including photovoltaics and biogas in Germany and electric...

Sustainable waste management practices have become challenging due to our consumption behavior and changing socioeconomic conditions. Waste management is a multidimensional problem that requires technology, economics, and sociocultural and political activities to go hand in hand. This chapter attempts to summarize the key influential aspects in was...

The rise in intermittent renewable electricity production presents a global requirement for energy storage. Biological hydrogen methanation (BHM) facilitates wind and solar energy through the storage of otherwise curtailed or constrained electricity in the form of the gaseous energy vector biomethane. Biological methanation in the circular economy...

Feedstocks characteristics and their provision cost can have a significant impact on the cost of methane production in an anaerobic digestion (AD) facility. This study investigated the impacts of changing grass silage characteristics, grass silage and cattle slurry provision costs and their binary mixing ratios on the cost of methane production fro...

Dark fermentation may be hindered by insufficient bioavailable carbon and nitrogen sources as well as recalcitrant cell wall structures of substrates. Protein-rich microalgae and carbohydrate-rich rice residue with various mix ratios can optimise biohydrogen and volatile fatty acids production. Optimal pretreatment of the microalgae with 1% H2SO4 a...

Interspecies electron transfer is a fundamental factor determining the efficiency of anaerobic digestion (AD), which involves syntrophy between fermentative bacteria and methanogens. Direct interspecies electron transfer (DIET) induced by conductive materials can optimize this process offering a significant improvement over indirect electron transf...

Brown seaweed may be an option as a feedstock for gaseous biofuel production. This paper proposed a detailed study on the impacts of various segments of seaweed thalli on the biomethane production. Ascophyllum nodosum, Laminaria digitata, Laminaria hyperborea, Saccharina latissima and Saccorhiza polyschides have shown significant variation in proxi...

This paper documents a techno-economic assessment of biomethane feedstocks from urban, rural, and coastal settings. Additionally, the effect of three upgrading technologies was investigated, ranging from commercialised systems (water scrubbing) to more advanced systems: power to gas systems employing hydrogen to capture CO2; and microalgae cultivat...

The recast of the renewable energy directive (RED recast) considers power to gas (P2G) an advanced transport biofuel if a 70% greenhouse gas savings as opposed to the fossil fuel displaced is achieved. Power to methane systems can store electricity as gas and the system can be optimised in sourcing CO2 from biogas to upgrade biogas to biomethane. T...

Power-to-Gas (P2G) is a technology that converts electricity to gas and is termed gaseous fuel from non-biological origin. It has been mooted as a means of utilising low-cost or otherwise curtailed electricity to produce an advanced transport fuel, whilst facilitating intermittent renewable electricity through grid balancing measures and decentrali...

Direct interspecies electron transfer (DIET) in microbial communities plays a significant role in improving efficiency of biomethane production from anaerobic digestion. In this study, the impacts of conductive graphene on mesophilic and thermophilic anaerobic digestion (MAD and TAD) were comparatively assessed using the model substrate ethanol. Th...

This chapter presents an overview of bioreactor configurations for the production of biogas with an investigation of different enhancement strategies for the conversion of organic biomass to methane. Initially anaerobic digestion (AD) microbial processes are introduced. Subsequently, optimal bioreactor design is examined. The AD process is capable...

Increasing energy demand has led to excessive depletion of fossil fuels, significant emission of pollutants and climate change. It is an urgent task to secure clean alternative energy sources to ensure sustainable development. Bioenergy derived from biomass can play a major role in the future energy system due to its renewability, and sustainabilit...

Power to gas (P2G) has been mooted as a means of producing advanced renewable gaseous transport fuel, whilst providing ancillary services to the electricity grid through decentralised small scale (10 MW) energy storage. This study uses a discounted cash flow model to determine the levelised cost of energy (LCOE) of the gaseous fuel from non-biologi...

Biogas upgraded to biomethane can provide a renewable gaseous transport fuel and is one of the proposed solutions in meeting the renewable energy supply in transport targets set under the EU Renewable Energy Directive. The upgrading process for biogas involves the removal of CO2. Amine scrubbing is one traditional method of upgrading that is applie...

For bioenergy installations producing heat, the minimum required GHG savings will be 85% from 2026. This is significant and a considerable challenge for biogas systems. This paper investigates use of biogas from pig farms at a nearby milk processing facility, a large energy user. The paper examines minimisation of greenhouse gas (GHG) associated wi...

Pre-treatment can enhance anaerobic digestion of seaweed; however, seasonal variation in the biochemical composition of seaweed has a significant impact on the pre-treatment effect. In this study, various pre-treatments were employed for the brown seaweed Laminaria digitata harvested in March (with high ash content and low carbon to nitrogen (C:N)...

This IEA Bioenergy Task 37 report addresses methane emissions from biogas applications. Methane is a potent greenhouse gas and therefore any fugitive methane emissions from a renewable energy production system are not conducive to the ambition of reducing Greenhouse Gas (GHG) emissions. Within the biogas sector methane emission quantification is be...

This study compared single- and two-stage mesophilic fermentation of Laminaria digitata. The two-stage system comprised a hydrolysis reactor (H1) with a hydraulic retention time (HRT) of 4 days followed by two methanogenesis reactors M1 and M2 with HRT of 20 and 14 days respectively. The single-stage reactor (M3) had an HRT of 24 days. Specific met...

Biomethane is a flexible energy vector that can be used as a renewable fuel for both the heat and transport sectors. Recent EU legislation encourages the production and use of advanced, third generation biofuels with improved sustainability for future energy systems. The integration of technologies such as anaerobic digestion, gasification, and pow...

The suitability of existing sources of CO2 in a region (Ireland) for use in power to gas systems was determined using multi criteria decision analysis. The main sources of CO2 were from the combustion of fossil fuels, cement production, alcohol production, and wastewater treatment plants. The criteria used to assess the suitability of CO2 sources w...

Biomethane produced from seaweed is a third generation renewable gaseous fuel. The advantage of seaweed for biofuel is that it does not compete directly or indirectly for land with food, feed or fibre production. Furthermore, the integration of seaweed and salmon farming can increase the yield of seaweed per hectare, while reducing the eutrophicati...