A perspective on three sustainable hydrogen production technologies with a focus on technology readiness level, cost of production and life cycle environmental impacts.

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 summarises and contrasts different sustainable hydrogen production technologies including for their development, potential for improvement, barriers to large-scale industrial application, capital and operating cost, and life-cycle environmental impact. Polymer electrolyte membrane water electrolysis technology shows significant potential for large-scale application in the near-term, with a higher technology readiness level (expected to be 9 by 2030) and a levelized cost of hydrogen expected to be 4.15-6 €/kg H2 in 2030; this equates to a 50% decrease as compared to 2020. The four-step copper-chlorine (Cu-Cl) water thermochemical cycle can perform better in terms of life cycle environmental impact than the three- and five-step Cu-Cl cycle, however, due to system complexity and high capital expenditure, the thermochemical cycle is more suitable for long-term application should the technology develop. Biological conversion technologies (such as photo/dark fermentation) are at a lower technology readiness level, and the system efficiency of some of these pathways such as biophotolysis is low (less than 10%). Biomass gasification may be a more mature technology than some biological conversion pathways owing to its higher system efficiency (40%-50%). Biological conversion systems also have higher costs and as such require significant development to be comparable to hydrogen produced via electrolysis.

Spores of arbuscular mycorrhizal fungi host surprisingly diverse communities of endobacteria.

Arbuscular mycorrhizal fungi (AMF) are ubiquitous plant root symbionts, which can house two endobacteria: Ca. Moeniiplasma glomeromycotorum (CaMg) and Ca. Glomeribacter gigasporarum (CaGg). However, little is known about their distribution and population structure in natural AMF populations and whether AMF can harbour other endobacteria. We isolated AMF from two environments and conducted detailed analyses of endobacterial communities associated with surface-sterilised AMF spores. Consistent with the previous reports, we found that CaMg were extremely abundant (80%) and CaGg were extremely rare (2%) in both environments. Unexpectedly, we discovered an additional and previously unknown level of bacterial diversity within AMF spores, which extended beyond the known endosymbionts, with bacteria belonging to 10 other phyla detected across our spore data set. Detailed analysis revealed that: CaGg were not limited in distribution to the Gigasporaceae family of AMF, as previously thought; CaMg population structure was driven by AMF host genotype; and a significant inverse correlation existed between the diversity of CaMg and diversity of all other endobacteria. Based on these data, we generate novel testable hypotheses regarding the function of CaMg in AMF biology by proposing that they might act as conditional mutualists of AMF.

A perspective on methodologies and system boundaries to develop abatement cost for on-farm anaerobic digestion.

Marginal Abatement Cost Curves compare and assess greenhouse gas mitigation options available to various sectors of the economy. In the Irish agricultural sector, large anaerobic digestion facilities are currently considered a high-cost abatement solution. In prior studies of anaerobic digestion abatement costs, two options were assessed: the generation of heat and electricity from biogas (115 €/tCO2eq) and the production of renewable heat from biomethane (280 €/tCO2eq). Both scenarios encompass single cost values that may not capture the potentially variable nature of such systems. In contrast, prior techno-economic analyses and lifecycle analyses can provide a comparison of the abatement costs of anaerobic digestion systems at a range of scales. This work compares two case studies (based on prior literature) for small and medium-scale on farm anaerobic digestion systems. The small-scale system is set in Ireland with cattle slurry collected in open tanks during the winter, while the medium-scale system is set in the USA with cattle slurry collected periodically indoors all year-round. It was found that the abatement cost can vary between -117 to +79 € per t CO2eq. The key variables that affected the abatement cost were additional revenue streams such as biofertilizer sales, displaced energy savings, and additional incentives and emissions savings within the system boundary. Including only some of these options in the analysis resulted in higher abatement costs being reported. Based on the variation between system topologies and therefore system boundaries, assigning a single mitigation cost to anaerobic digestion systems may not be representative.

The veracity of an abatement cost analysis depends on a clear methodological process.The abatement cost varies based on the processes considered within the system boundary.On-farm digestion abatement costs assessed ranged from -117 to +79 €/tCO_2eq.On-farm emissions savings ranged from 609 to 10,358 tCO_2eq/yr.Abatement costs reduce when considering the income and emissions savings from co-benefits.

Design, Construction, and Concept Validation of a Laboratory-Scale Two-phase Reactor to Valorize Whiskey Distillery By-products.

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-phase anaerobic digester to produce volatile fatty acids (VFAs) and biogas may enable distilleries to transition toward a low-carbon bioeconomy. An example of such a system is a leach bed reactor connected to an expanded granular sludge bed (LBR-EGSB) which was designed, commissioned, and conceptually validated in this paper. Several design improvements progress the LBR-EGSB beyond previous reactor designs. An external gas-liquid-solid separator in the EGSB was used to capture any residual gases produced by the effluent and may reduce the amount of methane slippage and biomass washout. The implementation of a siphon-actuated leachate cup is a low-cost alternative that is less prone to actuation malfunction as compared to electrically actuated solenoid valves in previous reactor designs. Furthermore, replacing fresh water with distillery's liquid by-products as leachate promotes a circular repurpose and reuse philosophy. The system proved to be effective in generating VFAs (10.3 g VFAs L-1Leachate), in EGSB COD removal (96%), and in producing methane-rich biogas (75%vol), which is higher than the values achieved by traditional anaerobic digestion systems. The LBR-EGSB could ultimately provide more by-product valorization and decarbonization opportunities than traditional anaerobic digestion systems for a whiskey distillery.

Demand-driven biogas production from Upflow Anaerobic Sludge Blanket (UASB) reactors to balance the power grid.

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 to traditional AD systems. In this study, experimental trials validated the feasibility of operating the UASB in a demand-driven manner. The UASB was operated with leachate produced from a hydrolysis reactor treating grass silage. The UASB demonstrated a high degree of flexibility in responding to variable feeding regimes. The intra-day biogas production rate could be increased by up to 123% under 4 hours in demand-driven operation, without significant deterioration in performance. A model based on kinetic analysis was developed to help align demand-driven operation with the grid. The findings suggest significant opportunities for UASBs to provide positive and negative balance to the power grid.

Two-phase anaerobic digestion for enhanced valorisation of whiskey distillery by-products.

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 systems had higher methane content (ca. 75 %vol) than the traditional system (54 %vol) and furthermore, unlocked opportunities for volatile fatty acid production. The potential value that could be generated from the extraction of butyric acid and caproic acid was approximately €6.76 million for a 50 million litre alcohol facility (0.14 € per litre of whiskey). All three anaerobic digestion systems showed the potential to valorise whiskey by-products and convert current linear distillery production processes into circular repurpose and reuse production processes.

Evidence of a selective and bi-directional relationship between arbuscular mycorrhizal fungal and bacterial communities co-inhabiting plant roots.

Arbuscular mycorrhizal fungi (AMF) provide plants with vital mineral nutrients and co-exist inside the roots alongside a complex community of bacterial endophytes. These co-existing AMF and bacterial root communities have been studied individually and are known to be influenced in structure by different environmental parameters. However, the extent to which they are affected by environmental parameters and by each other is completely unknown. The current study addressed this knowledge gap by characterising AMF and bacterial communities inside plant roots from a natural and an agricultural ecosystem. Using multivariate modelling, the relative contribution of environmental parameters in structuring the two communities was quantified at different spatial scales. Using this model, it was possible to then remove the contribution of environmental parameters and show that the co-existing AMF and bacterial communities were significantly correlated with each other, explaining up to 36% of each other's variance. Notably, this was not due to the presence of know AMF endobacteria, as removal of endobacterial reads maintained the significance of correlation. These findings provide the first empirical evidence of a selective and bi-directional relationship between AMF and bacteria co-inhibiting plant roots and indicate that a significant fraction of this covariation is due to biological and ecological interactions between them.

A comparison of digestate management options at a large anaerobic digestion plant.

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 assesses the performance of three different digestate management options (MOs); land application of whole digestate (MO1), digestate separation (MO2), and digestate separation and evaporation (MO3), combined with centralised or decentralised digestate storage. All MOs required the same landbank area, whilst MO2 and MO3 reduced digestate management costs by 9% and 37% (if recovered heat is used) respectively. GHG emissions from MO2 were 41% lower than MO1 if renewable electricity was used. MO3 reduced GHG emissions by 63% compared to MO1, if renewable electricity and recovered heat were used. MO2 required the same centralised digestate storage volume as MO1 while MO3 required 44% of the centralised storage volume. Centralised digestate storage required a maximum of 79 days for digestate transportation (33 trucks/day, 20 m3 capacity) to land for MO1 and MO2, and 35 days for MO3. Decentralised digestate storage required 63 storage tanks and 15 trucks/day for MO1, 69 tanks and 15 trucks/day for MO2, and 68 tanks and 7 trucks/day for MO3. Tank size ranged from 500 m3 to 20,000 m3. MO3 combined with decentralised storage could reduce the cost and GHG emissions (if recovered energy is used), vehicle movements, and the number of storage tanks required for digestate management.

Trust Versus Content in Multi-functional Land Management: Assessing Soil Function Messaging in Agricultural Networks.

Growing sustainability demands on land have a high knowledge requirement across multiple scientific domains. Exploring networks can expose opportunities for targeting. Using mixed-methods combining social network analysis (SNA) and surveys, networks for key soil functions in case studies in Germany, Ireland and the Netherlands are explored. We find a diversity of contrasting networks that reflect local conditions, sustainability challenges and governance structure. Farmers were found to occupy a central role in the agri-environmental governance network. A comparison of the SNA and survey results indicate low acceptance of messages from many central actors indicating scope to better harness the network for sustainable land management. The source of the messages was important when it came to the implementation of farm management actions. Two pathways for enhanced farmer uptake of multi-functionality are proposed that have wider application are; to increase trust between farmers and actors that are agents of multi-functional messages and/or to increase the bundling or multi-functionality of messages (mandate) of actors trusted by farmers.

Effect of contrasting phosphorus levels on nitrous oxide and carbon dioxide emissions from temperate grassland soils.

Agricultural practices such as repeated fertilization impact carbon (C), nitrogen (N) and phosphorus (P) cycling and their relationships in the plant-soil continuum, which could have important implications for the magnitude of greenhouse gas emissions. However, little is known about the effect of C and N additions under contrasting soil P availability status on nitrous oxide (N2O) and carbon dioxide (CO2) emissions. In this study, we conducted a field-based experiment that investigated the impact of long-term (23 years) P management (no (P0, 0 kg P ha-1), low (P15, 15 kg P ha-1) and high (P45, 45 kg P ha-1) P inputs) on N2O and CO2 emissions following two C + N application events in two managed grassland ecosystems with loam and sandy loam soils. The magnitude of fluxes varied between the soil P availability levels. Cumulative N2O emission was significantly higher in P0 soils (1.08 ± 0.09 g N2O-N m-2) than P45 soils (0.63 ± 0.03 g N2O-N m-2), with the loam soil (1.04 ± 0.04 g N2O-N m-2) producing significantly higher emissions than the sandy loam soil (0.88 ± 0.05 g N2O-N m-2). We conclude that P-limitation stimulates N2O emissions, whereas P-enrichment promotes soil respiration in these temperate grassland sites. Our findings inform effective nutrient management strategies underpinning optimized use of N and P inputs to agricultural soils as mitigation measures for both food security and reducing greenhouse gas emissions.

Emerging bioelectrochemical technologies for biogas production and upgrading in cascading circular bioenergy systems.

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 bioelectrochemical technologies in a circular cascading bioeconomy, including for power-to-gas AD (P2G-AD), microbial electrolysis cell AD (MEC-AD), and AD microbial electrosynthesis (AD-MES). The mass and energy flow of the three bioelectrochemical systems are compared with the conventional AD amine scrubber system depending on the availability of renewable electricity. An energy balance assessment indicates that P2G-AD, MEC-AD, and AD-MES circular cascading bioelectrochemical systems gain positive energy outputs by using electricity that would have been curtailed or constrained (equivalent to a primary energy factor of zero). This analysis of technological innovation, aids in the design of future cascading circular biosystems to produce sustainable advanced biofuels.

Biological hydrogen methanation systems - an overview of design and efficiency.

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 hydrogen - produced during electrolysis - with carbon dioxide in biogas to produce methane (4H2 + CO2 = CH4 + 2H2), 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 co-efficient was identified.

Using machine learning to estimate herbage production and nutrient uptake on Irish dairy farms.

Nutrient management on grazed grasslands is of critical importance to maintain productivity levels, as grass is the cheapest feed for ruminants and underpins these meat and milk production systems. Many attempts have been made to model the relationships between controllable (crop and soil fertility management) and noncontrollable influencing factors (weather, soil drainage) and nutrient/productivity levels. However, to the best of our knowledge not much research has been performed on modeling the interconnections between the influencing factors on one hand and nutrient uptake/herbage production on the other hand, by using data-driven modeling techniques. Our paper proposes to use predictive clustering trees (PCT) learned for building models on data from dairy farms in the Republic of Ireland. The PCT models show good accuracy in estimating herbage production and nutrient uptake. They are also interpretable and are found to embody knowledge that is in accordance with existing theoretical understanding of the task at hand. Moreover, if we combine more PCT into an ensemble of PCT (random forest of PCT), we can achieve improved accuracy of the estimates. In practical terms, the number of grazings, which is related proportionally with soil drainage class, is one of the most important factors that moderates the herbage production potential and nutrient uptake. Furthermore, we found the nutrient (N, P, and K) uptake and herbage nutrient concentration to be conservative in fields that had medium yield potential (11 t of dry matter per hectare on average), whereas nutrient uptake was more variable and potentially limiting in fields that had higher and lower herbage production. Our models also show that phosphorus is the most limiting nutrient for herbage production across the fields on these Irish dairy farms, followed by nitrogen and potassium.

Functional Land Management: Bridging the Think-Do-Gap using a multi-stakeholder science policy interface.

Functional Land Management (FLM) is proposed as an integrator for sustainability policies and assesses the functional capacity of the soil and land to deliver primary productivity, water purification and regulation, carbon cycling and storage, habitat for biodiversity and recycling of nutrients. This paper presents the catchment challenge as a method to bridge the gap between science, stakeholders and policy for the effective management of soils to deliver these functions. Two challenges were completed by a wide range of stakeholders focused around a physical catchment model-(1) to design an optimised catchment based on soil function targets, (2) identify gaps to implementation of the proposed design. In challenge 1, a high level of consensus between different stakeholders emerged on soil and management measures to be implemented to achieve soil function targets. Key gaps including knowledge, a mix of market and voluntary incentives and mandatory measures were identified in challenge 2.

Cascading biomethane energy systems for sustainable green gas production in a circular economy.

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 power to gas, along with advanced feedstocks such as algae will be at the forefront in meeting future sustainability criteria and achieving a green gas supply for the gas grid. This paper explores the relevant pathways in which an integrated biomethane industry could potentially materialise and identifies and discusses the latest biotechnological advances in the production of renewable gas. Three scenarios of cascading biomethane systems are developed.

The effects of introducing high-fidelity simulation to preclinical student respiratory therapists.

INTRODUCTION: This action research study examines the use of high-fidelity simulation (HFS) in a 3-year Respiratory Therapy advanced diploma program offered at a community college located in southwestern Ontario. It seeks to identify if the use of preclinical experiential learning offered through various HFS scenarios had an impact on learners' ability to transition into clinical practicum. The experiential learning theory provided the framework that guided this study as it sought to determine the effect, if any, of HFS on confidence and student anxiety. METHODS: A mixed-method research approach to data collection was used to assess both qualitative and quantitative data. A presimulation, Likert-type questionnaire was completed by 20 participants and utilized to identify learning styles and anxiety with experiential learning activities. The qualitative component of the study involved a focus group exploring four participant's impressions of how HFS affected their ability, anxiety, and competence in preparation for their clinical rotation. Finally, following the focus of action research, the researcher's observations and journaling were used as a method to improve the future delivery and practice of simulation at the researcher's institution. RESULTS: The results of this research project suggest that learners have an increased level of confidence following simulation participation, but that their anxiety levels have not changed when thinking about transitioning into clinical practicum. CONCLUSION: Ongoing research focusing on how this model affects student respiratory therapists' abilities and performance in clinical practicum is needed.

Biogas production generated through continuous digestion of natural and cultivated seaweeds with dairy slurry.

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.

Optimised biogas production from microalgae through co-digestion with carbon-rich co-substrates.

Microalgae can be used to upgrade biogas to biomethane and subsequently be digested for biogas production. However, the low C:N ratio of species such as Arthrospira platensis may cause ammonia inhibition and low process stability during anaerobic digestion. This study investigates co-fermentation of A. platensis with carbon-rich co-substrates (barley straw, beet silage and brown seaweed) at a C:N ratio of 25 to enhance biomass conversion. No synergistic effects on biomethane potential could be proven in batch fermentation tests. However continuous digestion trials showed significantly improved process stability. Mono-digestion of A. platensis was stable only at an organic loading of 1.0gVSL(-1)d(-1). The optimum process co-digested A. platensis with seaweed and achieved stable operation at an organic loading of 4.0gVSL(-1)d(-1). Co-digestion of microalgae and seaweed can be effectively applied to integrated coastal biomethane systems.

Methanosarcina Play an Important Role in Anaerobic Co-Digestion of the Seaweed Ulva lactuca: Taxonomy and Predicted Metabolism of Functional Microbial Communities.

Macro-algae represent an ideal resource of third generation biofuels, but their use necessitates a refinement of commonly used anaerobic digestion processes. In a previous study, contrasting mixes of dairy slurry and the macro-alga Ulva lactuca were anaerobically digested in mesophilic continuously stirred tank reactors for 40 weeks. Higher proportions of U. lactuca in the feedstock led to inhibited digestion and rapid accumulation of volatile fatty acids, requiring a reduced organic loading rate. In this study, 16S pyrosequencing was employed to characterise the microbial communities of both the weakest (R1) and strongest (R6) performing reactors from the previous work as they developed over a 39 and 27-week period respectively. Comparing the reactor communities revealed clear differences in taxonomy, predicted metabolic orientation and mechanisms of inhibition, while constrained canonical analysis (CCA) showed ammonia and biogas yield to be the strongest factors differentiating the two reactor communities. Significant biomarker taxa and predicted metabolic activities were identified for viable and failing anaerobic digestion of U. lactuca. Acetoclastic methanogens were inhibited early in R1 operation, followed by a gradual decline of hydrogenotrophic methanogens. Near-total loss of methanogens led to an accumulation of acetic acid that reduced performance of R1, while a slow decline in biogas yield in R6 could be attributed to inhibition of acetogenic rather than methanogenic activity. The improved performance of R6 is likely to have been as a result of the large Methanosarcina population, which enabled rapid removal of acetic acid, providing favourable conditions for substrate degradation.

A multisource feedback tool to assess ward round leadership skills of senior paediatric trainees: (2) Testing reliability and practicability.

BACKGROUND: A five-domain multisource feedback (MSF) tool was previously developed in 2009-2010 by the authors to assess senior paediatric trainees' ward round leadership skills. OBJECTIVES: To determine whether this MSF tool is practicable and reliable, whether individuals' feedback varies over time and trainees' views of the tool. METHODS: The MSF tool was piloted (April-July 2011) and field tested (September 2011-February 2013) with senior paediatric trainees. A focus group held at the end of field testing obtained trainees' views of the tool. RESULTS: In field testing, 96/115 (84%) trainees returned 633 individual assessments from three different ward rounds over 18 months. The MSF tool had high reliability (Cronbach's α 0.84, G coefficient 0.8 for three raters). In all five domains, data were shifted to the right with scores of 3 (good) and 4 (excellent). Consultants gave significantly lower scores (p<0.001), as did trainees for self-assessment (p<0.001). There was no significant change in MSF scores over 18 months but comments showed that trainees' performance improved. Trainees valued these comments and the MSF tool but had concerns about time taken for feedback and confusion about tool use and the paediatric assessment strategy. CONCLUSIONS: A five-domain MSF tool was found to be reliable on pilot and field testing, practicable to use and liked by trainees. Comments on performance were more helpful than scores in giving trainees feedback.