• Energy Research

The large market penetration of non-dispatchable renewable power sources (vRES), i.e., wind and photovoltaic, may be hampered by an increasing need for large scale energy storage capacity and the challenges of balancing the power grid. Novel technologies integrating waste gasification with reversible Solid-Oxide Cell systems have been proposed to provide flexible grid balancing services. The rSOC system operated in electrolysis mode uses excess power from vRES to generate hydrogen (H2), which is combined with syngas derived from waste gasification to produce methane (CH4). The rSOC system can also be operated in fuel cell mode by oxidising syngas to produce electricity. This paper presents a well-defined case study which aimed to estimate the potential deployment of a novel rSOC technology in a future power system dominated by intermittent renewables. The hourly power grid residual loads (i.e., the difference between load and vRES power generation) and the availability of low-grade organic waste and residues are quantified and matched for the southern Italian peninsula in 2030. The results show that the theoretical grid flexibility needs approximately 10 TW h of overproduction and 5 TW h of underproduction in 2030 to ensure the complete disposal of the municipal organic waste generated in 2030 (6.7 Mt) and that production of renewable CH4 will need to be 1.4–2.4 Mt, pointing to an intriguing perspective for the deployment of rSOC systems at a large scale. The multifunctionality of the system proposed is an added value that can make it a convenient and efficient piece of the puzzle of technologies required in a climate-neutral and circular economy. The results and methods here presented are intended to form the basis for estimations of future potential deployment and economic and environmental assessments of competing technologies.

This study aimed at evaluating the economic performances of and carbon footprint associated with innovative systems for the energetic valorization of second cheese whey (SCW), a by-product of whey cheese manufacture, through anaerobic digestion processes. Three systems were modeled: a conventional single-stage anaerobic digester (FAD), located at about 50 km from the dairy factory; an on-site conventional single-stage anaerobic digester (CAD), located at the dairy industry; and an on-site two-stage anaerobic digester (TAD). The TAD technology enables the simultaneous production of hydrogen and methane on site. The biogases produced were combusted in combined heat and power plants (CHP), but only the onsite systems provided process heat to the dairy factory. In the specific conditions assumed, TAD configuration exhibited a higher energy output, which led to a GHG emission reduction of about 60% compared to FAD, mostly thanks to the additional hydrogen (H2) production and the improved engine performances. A detailed cost analysis confirmed the results of the environmental analysis, pointing to the TAD solution as the most economically viable, with a payback period of 9 years, while the CAD had a payback time of 12 years. The results here presented aim at providing the dairy industry with a robust economic analysis on the opportunity of building an innovative system for SCW valorization, as well as providing policymakers with environmental reliable data to support the promotion of this technology.

Abstract 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.

The development of innovative solutions to decarbonize hard-to-abate sectors is a priority challenge in the quest to mitigate climate change. The GHG emission mitigation potential of the carbon capture Calcium Looping process (CaL) is investigated in this work. Two steelmaking routes are modeled: a blast furnace and a basic oxygen furnace (BF-BOF), and a direct reduction process and an electric arc furnace (DR-EAF), both of which are coupled with CaL technology. The carbon footprints of the two systems were evaluated, through an eco-design approach, with the aim of quantifying the GHG emissions and identifying the hotspots of the emissions. DR-EAF was found to be characterized by lower GHG emissions than BF-BOF (0.9 t vs 2.1 t CO2eq per tonne of liquid steel produced), as it is intrinsically more efficient and less carbon intensive. For this reason, the adoption of the CaL technology resulted to be more effective when applied to the BF-BOF, as it led to a reduction in GHG emissions of up to 66%, with respect to baseline plant configuration without the CaL system. The primary energy demand increased considerably by the integration of CaL in BF-BOF and this would be amplified in a future scenario dominated by renewable energy resources. We also remarked the importance of the CaL technology being cir- cular to reduce and reuse the spent material deployed for CO2 sequestration. This work ends with a parametric analysis that points out the importance of the timescale of climate change metrics on the evaluation of the carbon footprint

Abstract In the framework of the European project SSH2S, a solid-state hydrogen storage tank - fuel cell system was demonstrated as Auxiliary Power Unit (APU) for a light duty vehicle. In this work, we have assessed the environmental impacts and the costs of the system developed. Following an eco-design approach, we have identified the processes mostly contributing to them and we have suggested possible improvements. By performing a Life Cycle Assessment (LCA), we found that, when the electricity consumption for hydrogen gas compression is included into the analysis, a solid-state hydrogen storage tank has similar greenhouse gas emissions and primary energy demand than those of type III and IV tanks. However, the resources depletion is higher for the solid-state system, even though the inclusions of the end of life of the APU and the recycling of the materials may result in different conclusions. The costs of an APU equipped with a solid-state hydrogen storage tank are significantly higher, about 1.5–2 times the systems based on type III and IV tanks. However, mature technologies are compared with a prototype, which has much room for optimization. To improve both the environmental and economic performances of the APU, a reduction of structural materials for both the solid-state hydrogen tank and Balance of Plant is recommended.

The debate on forest bioenergy sustainability has been so far dominated by assessments made through the carbon emissions lens. The biodiversity perspective has been largely missing. The European Green Deal's ambitious targets have brought biodiversity and ecosystem condition restoration and conservation to the core of the EU's legislative portfolios. An opportunity to revisit some important governing texts with a biodiversity lens has therefore presented itself. In this study, we review the impacts on biodiversity and carbon emissions of specific bioenergy pathways that may be used to supply additional forest-based energy. We then synthesize our findings in a nexus matrix, plotting the pathways along a gradient of benefits through to detriments on the two dimensions to highlight win-win and lose-lose options. We found that some pathways do mitigate carbon emissions in the short-term while not deteriorating ecosystem condition. These include collecting fine woody debris within limits of locally established thresholds. We highlight the pathways that do little to mitigate carbon emissions and that are detrimental to ecosystems as well. These include removal of coarse woody debris and low stumps or the conversion of semi-natural, primary and old-growth forests to plantation forests with the purpose to produce bioenergy. We conclude that in the currently polarised debate an approach which unambiguously eliminates negative options is more fruitful than trying to find agreement on best options. Consequently, we present several governance measures that could limit the uptake of clearly undesirable pathways within Europe and we show that some lose-lose pathways are still considered “sustainable” within the European Green Deal.

Hydrogen and electric buses are considered effective options for decarbonizing the public transportation sector, positioning them as a leader in this transition. This study models the environmental and economic performances of a set of bus powertrain technologies, considering a real case-study of suburban public transport in Italy, and including fuel cell electric vehicles (FCEV), battery electric vehicles (BEV), biomethane-powered vehicles (CBM), natural gas (CNG), and diesel buses. The environmental performances of FCEV and BEV are significantly influenced by the energy source used for hydrogen production or battery charging. Specifically, using the electricity mix for FCEV leads to the highest greenhouse gas emissions and fossil fuel demand. In contrast, BEV show better environmental performance than conventional powertrains, especially when powered by photovoltaics. When powered by photovoltaics, BEV reveal similar results to FCEV in terms of environmental impacts, except for resource depletion, where both perform poorly. Transitioning from diesel to BEV or FCEV can enhance local air quality, regardless of the energy source. The economic analysis indicates that FCEV are the most expensive option, followed by BEV, both of which are currently costlier than diesel and CNG systems. CBM from waste streams emerges as a cost-effective and environmentally friendly solution. This study suggests prioritizing biomethane derived from biowaste, manure, and residual biomass (excluding energy crops) as a part of the fuels for public transport decarbonization in the EU to advance EU decarbonization goals, despite limitations due to resource availability. Furthermore, BEV powered by renewables should be prioritized whenever their range is adequate.∗