Use of surplus wind electricity in Ireland to produce compressed renewable gaseous transport fuel through biological power to gas systems

Power to gas (P2G) may be used to store curtailed electricity whilst converting the energy vector to gas. To be economically viable these systems require cheap electricity and a cheap concentrated source of CO2. Biogas produced from anaerobic digestion typically comprises of 60% methane and 40% CO2. The P2G system substitutes for the conventional upgrading system by using hydrogen (derived from surplus wind electricity) to react with CO2 and increases the methane output. The potential CO2 production from biogas in Ireland associated with typical wet substrates is assessed as more than 4 times greater than that required by the potential level of H2 from curtailed electricity. Wind energy curtailment in 2020 in Ireland is assessed conservatively at 2175GWeh/a. Thus P2G is limited by levels of curtailment of electricity rather than biogas systems. It is shown that 1 GWeh of electricity used to produce H2 for upgrading biogas in a P2G system can affect a savings of 97 tonnes CO2. The cost of hydrogen is assessed at €0.96/m3 renewable methane when the price of electricity is €c5/kWeh. This leads to a cost of compressed renewable gas from grass of €1.8/m3. This drops to €1.1/m3 when electricity is purchased at €c0.2/kWeh

Techno-economic analysis of biogas upgrading via amine scrubber, carbon capture and ex-situ methanation

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 applied due to its low methane slippage and its capability to provide a high purity renewable methane product. However, new technologies such as power to gas (P2G) can also upgrade biogas through biological methanation by combining the CO2 in biogas with H2 to produce renewable methane. The H2 for P2G can be produced through electrolysis of renewable electricity. Through simulation software – SuperPro Designer, the economics of different pathways for upgrading biogas from a grass silage and slurry fed digester are analysed and compared in this paper. Three scenarios were investigated: biogas upgrading through amine scrubbing (scenario 1); biogas upgrading through amine scrubbing with CO2 directed to ex-situ biological methanation (scenario 2) and biogas upgrading through ex-situ biological methanation only (scenario 3). The results show that at a net present value of zero, the minimum selling price (MSP) per m3 of renewable methane for scenario 1, 2 and 3 is €0.76; €1.50 and €1.43, respectively (with an electricity price to produce H2 of €0.10/kWh and a grass silage production cost of €27/t). The electricity price has a significant effect on the cost of renewable methane in both scenarios 2 and 3. The MSP reduces to €1.09 and €1.00 per m3 of renewable methane, respectively for scenarios 2 and 3, if the electricity price is reduced to €0.05/kWh. Since the renewable methane MSP from scenario 2 is higher than scenario 3, it is suggested that direct biogas injection to the methanation reactor is financially more attractive than capturing CO2 from biogas and feeding it to the methanation step. The MSP of renewable methane from both scenarios 2 and 3 are significantly higher than that of scenario 1. However, when considering climate change mitigation, balancing of the electricity network and storage of surplus electricity, utilising P2G can offset some of these costs. The cost of H2 is a significant factor in determining the cost of renewable methane

Establishing and validating noninvasive prenatal testing procedure for fetal aneuploidies in Vietnam

Noninvasive prenatal testing (NIPT) for fetal aneuploidies has been widely adopted in developed countries. Despite the sharp decrease in the cost of massively parallel sequencing, the technical know-how and skilled personnel are still one of the major limiting factors for applying this technology to NIPT in low-income settings. Here, we present the establishment and validation of our NIPT procedure called triSure for detection of fetal aneuploidies.We established the triSure algorithm based on the difference in proportion of fetal and maternal fragments from the target chromosome to all chromosomes. Our algorithm was validated using a published data set and an in-house data set obtained from high-risk pregnant women in Vietnam who have undergone amniotic testing. Several other aneuploidy calling methods were also applied to the same data set to benchmark triSure performance.The triSure algorithm showed similar accuracy to size-based method when comparing them using published data set. Using our in-house data set from 130 consecutive samples, we showed that triSure correctly identified the most samples (overall sensitivity and specificity of 0.983 and 0.986, respectively) compared to other methods tested including count-based, sized-based, RAPIDR and NIPTeR.We have demonstrated that our triSure NIPT procedure can be applied to pregnant women in low-income settings such as Vietnam, providing low-risk screening option to reduce the need for invasive diagnostic tests

A technical, economic and environmental analysis of renewable gas produced from power to gas systems

Storing surplus or curtailed renewable electricity as a gaseous transport fuel is a suggested method of reducing greenhouse gas emissions, increasing the supply of indigenous energy, providing long-term energy storage, facilitating intermittent renewable electricity sources and providing an advanced source of renewable transport fuel. The technology involved is Power to Gas (P2G) which uses electricity to split water into hydrogen (H2) and oxygen (O2) through electrolysis (power to hydrogen). Subsequently power to methane involves combining the H2 with carbon dioxide (CO2) to produce methane (CH4) via the Sabatier reaction (4H2 + CO2 = CH4 + 2H2O). Storage of renewable electricity as CH4 allows for long term storage by utilising the existing natural gas grid infrastructure. The aim of this thesis is to evaluate the viability of renewable gas produced from P2G utilised as an upgrading system for a biogas plant by assessing the technical, economic, and environmental aspects of such a system. Various methods were applied in this thesis: a linear additive model was used for sustainability assessment; an Excel model and Superpro designer software were applied for technology and costs analysis; and GaBi software was used to assess environmental impact. The result of the sustainability assessments of large scale energy storage technologies (P2G, pumped hydroelectric storage (PHES), and compressed air energy storage (CAES)) indicated the benefits of P2G as a dynamic decentralised mechanism which facilitated long term storage in the natural gas grid and facilitated change in energy vector from electricity to gas and subsequent availability for renewable heat and transport. The potential resource of CO2 from biogas in Ireland was assessed at 430 Mm3 per annum if all potential feedstocks for anaerobic digestion are utilised; this required a resource of 7,654 GWhe to be consumed to produce H2 to react with the CO2 in the biogas. The production costs of renewable gas from several feedstocks were calculated. These varied (depending on system inputs such as cost of electricity and feedstocks) between €1 and €2.5/m3 of renewable methane. The recast Renewable Energy Directive (RED) requires transport biofuels to effect a 70% GHG saving on a whole life cycle analysis when compared to the fossil fuel displaced. Our work shows that for power to gas to be sustainable as an upgrading method the maximum GHG emission of electricity used to produce the hydrogen should be less than 25.7 CO2eq/MJ

Can power to methane systems be sustainable and can they improve the carbon intensity of renewable methane when used to upgrade biogas produced from grass and slurry?

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. The crucial question in this work is whether P2G systems can be sustainable and if they can improve the sustainability of biomethane systems using traditional upgrading systems. This work evaluates a comparative lifecycle assessment of grass and slurry (50:50 wet weight equivalent to 80:20 volatile solid weight) biomethane using P2G and/or amine scrubbing as an upgrading method. The sustainability of P2G upgrading systems is heavily dependent on the carbon intensity of the source of electricity. Using a 41% decarbonised electricity mix the sustainability was reduced using P2G and would not be deemed sustainable under criterion set by the RED recast. Maintaining a maximum of 2% fugitive CH4 emissions, using 74% slurry (wet weight) in a grass slurry feedstock, allowing for 0.6 t carbon sequestration per hectare per annum in grasslands and using an electricity mix with 85% renewable electricity the whole system including P2G upgrading could satisfy the GHG savings of 70%. However, the traditional system employing amine scrubbing had higher levels of sustainability

Use of surplus wind electricity in Ireland to produce compressed renewable gaseous transport fuel through biological power to gas systems

Power to gas (P2G) may be used to store curtailed electricity whilst converting the energy vector to gas. To be economically viable these systems require cheap electricity and a cheap concentrated source of CO2. Biogas produced from anaerobic digestion typically comprises of 60% methane and 40% CO2. The P2G system substitutes for the conventional upgrading system by using hydrogen (derived from surplus wind electricity) to react with CO2 and increases the methane output. The potential CO2 production from biogas in Ireland associated with typical wet substrates is assessed as more than 4 times greater than that required by the potential level of H2 from curtailed electricity. Wind energy curtailment in 2020 in Ireland is assessed conservatively at 2175GWeh/a. Thus P2G is limited by levels of curtailment of electricity rather than biogas systems. It is shown that 1 GWeh of electricity used to produce H2 for upgrading biogas in a P2G system can affect a savings of 97 tonnes CO2. The cost of hydrogen is assessed at €0.96/m3 renewable methane when the price of electricity is €c5/kWeh. This leads to a cost of compressed renewable gas from grass of €1.8/m3. This drops to €1.1/m3 when electricity is purchased at €c0.2/kWeh

Screening for pancreatic lipase inhibitors: evaluating assay conditions using p-nitrophenyl palmitate as substrate

Current in vitro pancreatic lipase inhibitor screenings are based on previous spectrophotometric lipase assays. Nevertheless, they are with little evaluation of assay conditions. This study focuses on the impacts of experimental factors on enzyme activity in the assay with p-nitrophenyl palmitate as substrate by monitoring their effects on the hydrolysis rates. On the results, experimental conditions for lipase inhibitory assay were proposed. Notably, 5 mM sodium deoxycholate as emulsifier not only maintains the assay homogeneity but also enhances lipase activity. Organic co-solvents to dissolve organic inhibitors including DMSO, EtOH, MeOH, IPA, AcCN [0–30% (v/v)] was found well tolerated by the enzyme. With 10% (v/v) glycerol, lipase solutions can be stored at –20°C for up to one month without significant loss of activity. The results reported here provide researchers the assay condition sets in which most inhibitors can be dissolved, and lipase activity is not severely affected. This could accelerate the rational development of novel lipase inhibitors