Many factors enforce the intensification of grassland utilization which is associated with significant environmental impacts subjected to various legislative constraints. Nevertheless, the need for diversification in agricultural... more
Many factors enforce the intensification of grassland utilization which is
associated with significant environmental impacts subjected to various legislative
constraints. Nevertheless, the need for diversification in agricultural production and
the sustainability in energy within the European Union have advanced the role of
grassland as a renewable source of energy in grass biomethane production with
various environmental and socio-economic benefits. Here it is underlined that the
essential question whether the gaseous biofuel meets the EU sustainability criteria
of 60% greenhouse gas emission savings by 2020 can be met since savings up to
89.4% under various scenarios can be achieved. Grass biomethane production is
very promising compared to other liquid biofuels either when these are produced
by indigenous or imported feedstocks. Grass biomethane, given the mature and well
known technology in agronomy and anaerobic digestion sectors and the need for
rural development and sustainable energy production, is an attractive solution that
fulfils many legislative, agronomic and environmental requirements.
associated with significant environmental impacts subjected to various legislative
constraints. Nevertheless, the need for diversification in agricultural production and
the sustainability in energy within the European Union have advanced the role of
grassland as a renewable source of energy in grass biomethane production with
various environmental and socio-economic benefits. Here it is underlined that the
essential question whether the gaseous biofuel meets the EU sustainability criteria
of 60% greenhouse gas emission savings by 2020 can be met since savings up to
89.4% under various scenarios can be achieved. Grass biomethane production is
very promising compared to other liquid biofuels either when these are produced
by indigenous or imported feedstocks. Grass biomethane, given the mature and well
known technology in agronomy and anaerobic digestion sectors and the need for
rural development and sustainable energy production, is an attractive solution that
fulfils many legislative, agronomic and environmental requirements.
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The predominant crop feedstock for anaerobic digestion in Germany and Austria is maize. Ireland, with a temperate climate, is more suited to the production of grass and can achieve high yields (upto 16 t DM ha1). Grassland accounts for... more
The predominant crop feedstock for anaerobic digestion in Germany and Austria is maize. Ireland, with a temperate climate, is more suited to the production of grass and can achieve high yields (upto 16 t DM ha1). Grassland accounts for over 90% of agricultural land in Ireland. Irish agriculture is dominated by beef and milk production. Thus there is significant potential to produce biomethane from the codigestion of grass silage and slurry. Monodigestion of grass silage has been reported to give difficulties due to a deficiency in essential trace elements during long term operation. A comprehensive analysis of the digestion of grass silage and its codigestion with dairy slurry has been undertaken in laboratory studies at both batch and continuous scale. The results illustrate that larger proportions of grass in the substrate mix correspond to higher specific methane yields. It was also shown that effluent liquor return improved the performance of the continuous digestion of grass silage in monoand codigestion, facilitating operation at higher organic loading rates. It is suggested that hydraulic retention time can be the limiting factor in the loading rate of grass based digesters.
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ABSTRACT This paper investigates the environmental and economic feasibility of producing manufactured topsoil at the Port of Waterford, Ireland from two waste streams; dredge material and household waste. Four dredging and dredge material... more
ABSTRACT This paper investigates the environmental and economic feasibility of producing manufactured topsoil at the Port of Waterford, Ireland from two waste streams; dredge material and household waste. Four dredging and dredge material transport scenarios to a topsoil production facility are proposed; a trailing suction hopper dredger (TSHD) with pipeline transport, a grab hopper dredger (GHD) with barge transport, a small purchased port owned dredger (TSHD) with hopper transport and a leased dredger (GHD) with hopper transport. The stringent legislative framework governing the proposal is outlined. A detailed environmental and economic analysis is presented for each scenario. The environmental analysis presents results for CO2 transport emissions and also presents sensitivity analyses for different projects parameters. The economic analysis presents the annual profits or losses for each scenario for a range of topsoil production quantities and integrated into the current dredging regime at the Port of Waterford. Economic sensitivity analyses are presented for different project parameters. This paper recommends, based on the analysis undertaken, the use of a leased dredger with hopper transport to transport the dredge material to the topsoil production site as the most feasible option currently available at the Port of Waterford. The proposal provides an environmentally sustainable end use for dredge material as an alternative to disposal at sea.
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Abstract 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... more
Abstract 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 significantly depending on biochar properties. The correlations between them are not fully understood. Herein, biochars with different physicochemical properties were produced from a whiskey by-product “draff” and subsequently applied in the digestion of draff. The biochar produced at 700 °C statistically (p less than 0.05) enhanced biomethane yield by 5%. In contrast, biochars produced at 500 and 900 °C did not increase biomethane yield. The addition of 700 °C-derived biochar in AD increased the relative abundance of the methanogen Methanosarcina, which may be the electron-accepting partner in direct interspecies electron transfer (DIET). The enrichment of Methanosarcina suggested the potential shift of the interspecies electron transfer pathway towards the DIET mode. The characterization of biochar properties suggested that moderate graphitization degree and abundant active surface functional groups (such as –C O, pyridinic-N, and graphitic-N) were correlated with a more stimulating interspecies electron transfer through both the carbon matrices and the charging – discharging cycles of surface functional groups.
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Research Interests: Engineering, Chemistry, Technology, Agronomy, Biogas, and 6 moreAnaerobic Digestion, Methanogenesis, Methane, Manure, Slurry, and Silage
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Research Interests: Engineering, Mechanical Engineering, Environmental Science, Renewable Energy, Waste Management, and 10 moreMulti-criteria Decision Analysis infrastructure, Electricity, Natural Gas, Wastewater, Energy Storage, Sewage Treatment, Electricity Generation, Electrical And Electronic Engineering, Fossil Fuel, and Power to Gas
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This study was conducted to advance the understanding of thermophilic grass digestion. Late harvested grass silage was fermented at thermophilic conditions at increasing organic loading rates (OLR). Stable digestion took place at an OLR... more
This study was conducted to advance the understanding of thermophilic grass digestion. Late harvested grass silage was fermented at thermophilic conditions at increasing organic loading rates (OLR). Stable digestion took place at an OLR between 3 and 4gVSL(-1)d(-1). This enabled specific methane yields (SMY) as high as 405LCH4kgVS(-1). An accumulation of volatile fatty acids (VFA), accompanied by a gradual deterioration of pH, FOS/TAC (ratio of VFA to alkalinity) arose at an OLR between 5 and 7gVSL(-1)d(-1), yet inhibition did not occur. SMY decreased with reduced retention time ranging between 336 and 358LCH4kgVS(-1) at OLR 7 and 5gVSL(-1)d(-1) respectively. The biomethane efficiencies remained high (92-103%) at corresponding retention times. Comparative results indicated a superior performance with respect to higher loading and SMY as compared with mesophilic conditions.
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Abstract This study compared single- and two-stage mesophilic fermentation of Laminaria digitata . The two-stage system comprised a hydrolysis reactor (H 1 ) with a hydraulic retention time (HRT) of 4 days followed by two methanogenesis... more
Abstract This study compared single- and two-stage mesophilic fermentation of Laminaria digitata . The two-stage system comprised a hydrolysis reactor (H 1 ) with a hydraulic retention time (HRT) of 4 days followed by two methanogenesis reactors M 1 and M 2 with HRT of 20 and 14 days respectively. The single-stage reactor (M 3 ) had an HRT of 24 days. Specific methane yields of 176, 234 and 221 L/kg VS were obtained for M 1 , M 2 and M 3 . The methane concentration of the biogas was 22% higher for the two-stage system (58–61%) than the single-stage system (50%). Hydrolysis yielded a hydrogen yield of 26 L/kg VS. The two-stage system (H 1 , M 2 ) provided an overall energy yield of 8.66 MJ/kg at an HRT of 18 days compared to 7.89 MJ/kg in the single-stage system with an HRT of 24 days. Thus, the two-stage system reduced the HRT by 33% whilst improving the energy conversion by 9.8%.
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Research Interests: Engineering, Environmental Engineering, Chemical Engineering, Chemistry, BIOCHAR, and 14 moreWaste Management, Multidisciplinary, Anaerobic Digestion, Sewage sludge, Carbonization, Carbon Materials, Biogas Plants, Digestate, Engineering Chemical, Organic Matter, Pretreatment, Physicochemical Properties, Energy recovery, and Hydrochar
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Abstract 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... more
Abstract 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 understand the impact of furfural on hydrogen-producing Enterobacter aerogenes in dark fermentation of glucose. When adding 5 mM furfural in fermentation, hydrogen yield unexpectedly increased to 193.7 mL/g compared to 163.5 mL/g (in the absence of furfural); and the associated peak hydrogen production rate increased by 126%. This phenomenon from a thermodynamic perspective was due to the fact that furfural at a low concentration contributes to hydrogen production. A higher concentration of furfural (30 mM) significantly decreased hydrogen yield to 109.1 mL/g owing to severe cell membrane damage. The indicator of half-maximal inhibitory concentration was calculated as 32.5 mM. A postulated metabolic response of E. aerogenes to furfural is that the degradation of low concentrations of furfural (5 mM) involved a reduction reaction of furfural to hydrogen and furfuryl alcohol. However, a high concentration of furfural (30 mM) caused significant cell disfunction in normal metabolism, causing increased deformation degree in bacterial surface.
Research Interests: Mechanical Engineering, Chemistry, Food Science, Renewable Energy, Metabolism, and 13 moreBiohydrogen, Cytology, Ic, Hydrogen Production, Fermentation, Enterobacter aerogenes, Pulp and Paper Industry, Cell Proliferation, Bacteria (Microorganisms), Electrical And Electronic Engineering, Furfural, Dark Fermentation, and Aldehydes
The technical feasibility of long term anaerobic mono-digestion of two brown seaweeds, and co-digestion of both seaweeds with dairy slurry was investigated whilst increasing the organic loading rate (OLR). One seaweed was natural (L.... more
The technical feasibility of long term anaerobic mono-digestion of two brown seaweeds, and co-digestion of both seaweeds with dairy slurry was investigated whilst increasing the organic loading rate (OLR). One seaweed was natural (L. digitata); the second seaweed (S. Latissima) was cultivated. Higher proportions of L. digitata in co-digestion (66.6%) allowed the digester to operate more efficiently (OLR of 5kgVSm(-3)d(-1) achieving a specific methane yield (SMY) of 232LCH4kg(-1)VS) as compared to lower proportions (33.3%). Co-digestion of 66.6% cultivated S. latissima, with dairy slurry allowed a higher SMY of 252LCH4kg(-1)VS but at a lower OLR of 4kgVSm(-3)d(-1). Optimum conditions for mono-digestion of both seaweeds were effected at 4kgVSm(-3)d(-1). Chloride concentrations increased to high levels in the digestion of both seaweeds but were not detrimental to operation.
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Abstract Ex-situ biomethanation (CO2 + 4H2 → CH4 + 2H2O) can simultaneously achieve renewable electricity storage and CO2 valorisation. However, fluctuations in variable renewable electricity may lead to intermittent hydrogen supply,... more
Abstract Ex-situ biomethanation (CO2 + 4H2 → CH4 + 2H2O) can simultaneously achieve renewable electricity storage and CO2 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 materials may act as an abiotic additive to enhance microbial robustness and improve system performance. Nanomaterial graphene and pyrochar were compared to assess their effects on biomethanation systems with an intermittent supply of hydrogen. Results revealed that intermittent gas supply caused deterioration in the restart performance with only 66% of theoretical methane production obtained in the control compared with 84% under steady state conditions. The addition of graphene in biomethanation led to 78% of the theoretical methane production after repetitive intermittent supply; this improvement is postulated to be due to its high electrical conductivity and large specific surface (500 m2/g). In comparison, pyrochar amendment did not lead to a significant improvement in upgrading performance. Microbial analysis showed that the OTUs affiliated to bacteria withinin the order SHA-98 (42.9% in abundance) and archaea from the genus Methanothermobacter (99%) may result in the establishment of a new syntrophic relationship to improve the robustness of biomethanation process.
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Abstract 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... more
Abstract 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. Anaerobic digestion (AD) is a technology which with other bio-based technologies can effect improved energy conversion and reduction in greenhouse gas (GHG) emissions across sectors beyond energy. Here, an AD-centred cascading circular system with carbon capture and utilisation was proposed by incorporating power to gas (P2G), microbial electrolysis cell (MEC), and digestate valorisation for biochar production. The system as modelled converted CO2 to biomethane and digestate to biochar for CO2 sequestration. This was exemplified through cattle slurry with an annual production of 3.03 billion tons in three studied regions (the EU, China and the US), which was shown to produce a maximum of 2.29 EJ (equivalent to 1.64% of natural gas demand in 2018) of total energy in the form of advanced biofuels (biomethane, bio-oil and syngas) via the AD-MEC system, which was preferable to a conventional AD or an AD-P2G system. The treatment of cattle slurry with AD-MEC led to a combined 397.4 MtCO2e of GHG emission savings in the three regions. This could contribute to avoiding 2.0% of GHG emissions (total 20.1 GtCO2e) in the three regions. The sustainability of such a system was shown to be dependent on access to low-carbon and low-cost electricity systems.