Many factors enforce the intensification of grassland utilization which is
associated with signif... 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.
Biomethane produced from seaweed is a third generation renewable gaseous fuel. The advantage of s... more 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 eutrophication from fish farming. So far, full comprehensive life cycle assessment (LCA) studies of seaweed biofuel are scarce in the literature; current studies focus mainly on microalgal biofuels. The focus of this study is an assessment of the sustainability of seaweed biomethane, with seaweed sourced from an integrated seaweed and salmon farm in a north Atlantic island, namely Ireland. With this goal in mind, an attributional LCA principle was applied to analyse a seaweed biofuel system. The environmental impact categories assessed are: climate change, acidification, and marine, terrestrial and freshwater eutrophication. The seaweed Laminaria digitata is digested to produce biogas upgraded to natural gas standard, before being used as a transport biofuel. The baseline scenario shows high emissions in all impact categories. An optimal seaweed biomethane system can achieve 70% savings in GHG emissions as compared to gasoline with high yields per hectare, optimum seaweed composition and proper digestate management. Seaweed harvested in August proved to have higher methane yield. August seaweed biomethane delivers 22% lower impacts than biomethane from seaweed harvested in October. Seaweed characteristics are more significant for improvement of biomethane sustainability than an increase in seaweed yield per unit area.
Boosting biogas production from recalcitrant lignin-based feedstock by adding lignin-derived carbonaceous materials within the anaerobic digestion process
Digestion of Grass Silage and Dairy Slurry at Batch and Continuous Scale
European Biomass Conference and Exhibition Proceedings, 2014
The predominant crop feedstock for anaerobic digestion in Germany and Austria is maize. Ireland, ... 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.
An environmental and economic assessment of topsoil production from dredge material
Resources Conservation and Recycling, Dec 1, 2010
ABSTRACT This paper investigates the environmental and economic feasibility of producing manufact... 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.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Improving biohydrogen and biomethane co-production via two-stage dark fermentation and anaerobic ... more Improving biohydrogen and biomethane co-production via two-stage dark fermentation and anaerobic digestion of the pretreated seaweed ,
Improved efficiency of anaerobic digestion through direct interspecies electron transfer at mesop... more Improved efficiency of anaerobic digestion through direct interspecies electron transfer at mesophilic and thermophilic temperature ranges, Chemical Engineering
The implementation of the Landfill Directive (96/31/EC) will lead to a massive reduction in quant... more The implementation of the Landfill Directive (96/31/EC) will lead to a massive reduction in quantities of Biodegradable Municipal Waste (BMW), which may be landfilled. In 2016, an estimated 2.6 million tonnes of BMW will require diversion from landfill in Ireland. Recycling of dry paper, reuse of textiles and home composting will divert significant quantities of BMW. However, to divert the quantities required to comply with the Directive a significant proportion of the Organic Fraction of Municipal Solid Waste (OFMSW) will require treatment in centralised biological facilities. A survey was undertaken of composting facilities in Ireland to ascertain present capacity, present technology employed and types of feedstock composted. A generic model (consisting of in-vessel composting followed by aerated static pile composting) was generated from technical, economic and environmental data obtained from the survey. The generic model is utilized to ascertain the effect of economies of scale, the effect of gate fees on potential profit per tonne feedstock and the greenhouse gas contribution of the composting process. The model was investigated for four scenarios ranging from small (11ktpa) to very large (220ktpa). The economic analysis indicated that a potential for profit of €52.5/t-€65.4/t was achievable without sale of compost. The direct greenhouse gas production equated to 566kgCO 2 /t. However considering the "do-nothing" scenario of landfill, 1,175kgCO 2 equiv /t is avoided. Thus 1 tonne of BMW saves 609kgCO 2 equiv .
The rise in intermittent renewable electricity production presents a global requirement for energ... more 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 involves the reaction of hydrogenproduced during electrolysiswith carbon dioxide in biogas to produce methane (4H 2 + CO 2 = CH 4 + 2H 2), typically increasing the methane output of the biogas system by 70%. In this paper, several BHM systems were researched and a compilation of such systems was synthesized, facilitating comparison of key parameters such as methane evolution rate (MER) and retention time. Increased retention times were suggested to be related to less efficient systems with long travel paths for gases through reactors. A significant lack of information on gas-liquid transfer coefficient was identified.
What physicochemical properties of biochar facilitate interspecies electron transfer in anaerobic digestion: A case study of digestion of whiskey by-products
Fuel, Dec 1, 2021
Abstract The efficiency of microbial interspecies electron transfer between syntrophic bacteria a... 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.
Anaerobic co-digestion of contrasting substrates can result in synergistic or antagonistic effect... more Anaerobic co-digestion of contrasting substrates can result in synergistic or antagonistic effects on methanogenesis. Biogas and methane yields of the mixtures of cattle slurry (CS1 and CS2) or pig slurry with grass silages (GS1 and GS2) were measured using in vitro anaerobic batch digesters, and synergistic and antagonistic effects were investigated. Slurries and silages were incubated as individual substrates or as part of binary mixtures (slurry:silage mass ratios of volatile solids (VS)
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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.
Papers by Jerry Murphy