A Circular Approach for Making Fischer–Tropsch E-fuels and E-chemicals From Biogas Plants in Europe

In a mature circular economy model of carbon material, no fossil compound is extracted from the underground. Hence, the C1 molecule from non-fossil sources such as biogas, biomass, or carbon dioxide captured from the air represents the raw material to produce various value-added products through carbon capture and utilization routes. Accordingly, the present work investigates the utilization of the full potential of biogas and digestate waste streams derived from anaerobic digestion processes available at the European level to generate synthetic Fischer–Tropsch products focusing on the wax fraction. This study estimates a total amount of available carbon dioxide of 33.9 MtCO2/y from the two above-mentioned sources. Of this potential, 10.95 MtCO2/y is ready-to-use as separated CO2 from operating biogas-upgrading plants. Similarly, the total amount of ready-to-use wet digestate corresponds to 29.1 Mtdig/y. Moreover, the potential out-take of Fischer–Tropsch feedstock was evaluated based on process model results. Utilizing the full biogas plants’ carbon potential available in Europe, a total of 10.1 Mt/h of Fischer–Tropsch fuels and 3.86 Mt/h of Fischer–Tropsch waxes can be produced, covering up to 79% of the global wax demand. Utilizing only the streams derived from biomethane plants (installed in Europe), 136 ton/h of FT liquids and 48 ton/h of FT wax can be generated, corresponding to about 8% of the global wax demand. Finally, optimal locations for cost-effective Fischer–Tropsch wax production were also identified

Optimal design of PV-based grid-connected hydrogen production systems

A cost-optimal design of power-to-hydrogen (PtH) systems is crucial to produce hydrogen at the lowest specific cost. New challenges arise when it comes to ensuring a reliable and cost-effective hydrogen supply in the presence of variable renewable energy sources. In this context, the aim of this analysis is to investigate the optimal design of PV-based grid-connected hydrogen production systems under different scenarios. To this end, an optimisation framework based on the mixed integer linear programming (MILP) technique is developed. Results are presented by employing a set of techno-economic and environmental indicators to provide general guidance on how to optimally size PtH systems, going beyond the analysis of a specific case study. The analysis is applied to Italy and particular attention is paid to exploring the impact of the price of grid electricity. The results indicate that the price of grid electricity strongly affects the optimal design of PtH systems. Specifically, in scenarios with high electricity prices, it is economically convenient to significantly oversize the PV plant and the electrolyser. The optimal PV ratio, representing the ratio between the PV size and the electrolyser size, increases from 1.6 to 2.7 as the electricity price rises from 50 to 300 euro/MWh. Additionally, when electricity prices exceed approximately 120 euro/MWh, the optimal electrolyser size (in terms of hydrogen production under rated conditions) becomes almost three times larger than the average hydrogen demand. By comparing gridconnected and off-grid scenarios, the importance of the electrical grid is also highlighted: even when poorly used, it plays a crucial role in limiting the size of the hydrogen storage. The levelised cost of hydrogen for the optimal PtH configuration falls within the range of 3.5-7 euro/kg (depending on the price of grid electricity) and increases to 8.2 euro/kg when the system operates off-grid. Finally, the hydrogen carbon footprint, quantified as kgCO2,e/kgH2, is also explored. Considering the current price and carbon intensity of grid electricity, t

Results from an industrial size biogas-fed SOFC plant (the DEMOSOFC project)

Abstract The EU-funded DEMOSOFC project aims to demonstrate the technical and economic feasibility of operating a 174 kWe Solid Oxide Fuel Cell (SOFC) in a wastewater treatment plant. The fuel for the three SOFC modules (3 × 58 kWe) is biogas, which is available on-site from the anaerobic digestion of sludge collected from treated wastewater. The integrated biogas-SOFC plant includes three main units: 1) the biogas cleaning and compression section, 2) the three SOFC power modules, and 3) the heat recovery loop. Main advantages of the proposed layout are the net electric efficiency of the SOFC, which is in the range 50–55%, and the near-zero emissions. A specific focus of the demonstration project is the deep and reliable removal of harmful biogas contaminants. The presented work is related to the design of the SOFC system integrated into the wastewater treatment plant, followed by the analysis of the first results from the plant operation. We analyzed the biogas yearly profile to determine the optimal SOFC capacity to install that is 3 SOFC modules. The rational is to maintain high the capacity factor while minimizing the number of shutdown per year (due to biogas unavailability). First results from plant operation are also presented. The first SOFC module was activated in October 2017 and the second in October 2018. The measured SOFC efficiency from compressed biogas to AC power has always been higher than 50–52%, with peaks of 56%. Dedicated emissions measurements have been performed onsite during December 2017. Results on real biogas operation show NO

Techno-economic assessment of biogas-fed CHP hybrid systems in a real wastewater treatment plant

The integration of solid oxide fuel cell (SOFC) systems and micro gas turbines in a reference wastewater treatment plant is proposed. The main scope is to utilize the available biogas in a real wastewater treat- ment plant (WWTP) to feed both the SOFCs and micro gas turbines (MGTs) to produce electrical power while covering the digester thermal demand of the plant. To do so, two cases namely SOFC-WWTP (in which the SOFC system is the only CHP unit), and SOFC-MGT-WWTP (integration of both SOFCs and microturbine systems) are proposed. Results show that use of microturbines along with the SOFC systems can increase the share of electricity covered by self-generation within the WWTP by up to 15% while keeping stable the coverage of the thermal load. Also, the energy efficiency of the novel system (SOFC- MGT-WWTP) is calculated to be 7% more than that of the SOFC-WWTP. Economic analysis results reveal that using microturbines, the payback time for whole the system could be reduced about 4 years. Also, for the short term scenario, the levelized cost of electricity for the SOFC-MGT-WWTP system is found to be 0.118 $/kWh which is about 12% less than that for the SOFC-WWTP system. However, for the long term scenario, the difference becomes remarkably les

Life cycle assessment of a renewable energy system with hydrogen-battery storage for a remote off-grid community

Remote areas usually do not have access to electricity from the national grid. The energy demand is often covered by diesel generators, resulting in high operating costs and significant environmental impacts. With reference to the case study of Ginostra (a village on a small island in the south of Italy), this paper analyses the environmental sustainability of an innovative solution based on Renewable Energy Sources (RES) integrated with a hybrid hydrogen-battery energy storage system. A comparative Life Cycle Assessment (LCA) has been carried out to evaluate if and to what extent the RES-based system could bring environmental improvements compared to the current diesel-based configuration. The results show that the impact of the RES-based system is less than 10% of that of the current diesel-based solution for almost all impact categories (climate change, ozone depletion, photochemical ozone formation, acidification, marine and terrestrial eutrophication and fossil resource use). The renewable solution has slightly higher values only for the following indicators: use of mineral and metal resources, water use and freshwater eutrophication. The climate change category accounts for 0.197 kg CO2 eq./kWh in the renewable scenario and 1.73 kg CO2 eq./kWh in the diesel-based scenario, which corresponds to a reduction in GHG emissions of 89%. By shifting to the RES-based solution, about 6570 t of CO2 equivalent can be saved in 25 years (lifetime of the plant). In conclusion, the hydrogen-battery system could provide a sustainable and reliable alternative for power supply in remote areas

A bottom-up appraisal of the technically installable capacity of biogas-based solid oxide fuel cells for self power generation in wastewater treatment plants

This paper proposes a bottom-up method to estimate the technical capacity of solid oxide fuel cells to be installed in wastewater treatment plants and valorise the biogas obtained from the sludge through an efficient conversion into electricity and heat. The methodology uses stochastic optimisation on 200 biogas profile scenarios generated from industrial data and envisages a Pareto approach for an a posteriori assessment of the optimal number of generation unit for the most representative plant configuration sizes. The method ensures that the dominant role of biogas fluctuation is included in the market potential and guarantees that the utilization factor of the modules remains higher than 70% to justify the investment costs. Results show that the market potential for solid oxide fuel cells across Europe would lead up to 1,300 MW of installed electric capacity in the niche market of wastewater treatment and could initiate a capital and fixed costs reduction which could make the technology comparable with alternative combined heat and power solutions

Installation of fuel cell-based cogeneration systems in the commercial and retail sector: Assessment in the framework of the {COMSOS} project

This work studies the technical and economic feasibility of the introduction of a SOFC-based cogeneration system to supply non-residential buildings with electricity and heat. The techno-economic evaluation is performed for the hotel and hospital sectors, by introducing real hourly load profiles (electrical and thermal) for the buildings. The analysis considers different countries in terms of energy intensity (and load profiles), cost of energy and regulations/incentives. Results are achieved by comparing the SOFC scenario with a benchmark one where electricity is supplied by the grid and heat by a natural gas fed boiler and evaluating the relative payback time between the two solutions. The analysis showed that, despite the current high investment cost of the SOFC system, in countries such as Germany, Italy and UK (where electricity prices are among the highest in Europe), the option is yet advisable if supported by effective subsidies (already existing for cogeneration systems), and it could offer a competitive alternative to traditional systems, especially in the hospital sector, where the relative payback time is achieved in the 10th year for UK, and in the 14th year for Germany and Italy. A cost reduction scenario has also been analyzed: results show that the SOFC is the best option in most of the locations, both economically and in terms of environmental impact (pollutants emissions reduction)