Abstract
Fuel production from hydrogen and carbon dioxide is considered an attractive solution as long-term storage of electric energy and as temporary storage of carbon dioxide. A large variety of CO2 sources are suitable for Carbon Capture Utilization (CCU), and the process energy intensity depends on the separation technology and, ultimately, on the CO2 concentration in the flue gas. Since the carbon capture process emits more CO2 than the expected demand for CO2 utilization, the most sustainable CO2 sources must be selected. This work aimed at modeling a Power-to-Gas (PtG) plant and assessing the most suitable carbon sources from a Life Cycle Assessment (LCA) perspective. The PtG plant was supplied by electricity from a 2030 scenario for Italian electricity generation. The plant impacts were assessed using data from the ecoinvent database version 3.5, for different CO2 sources (e.g., air, cement, iron, and steel plants). A detailed discussion on how to handle multi-functionality was also carried out. The results showed that capturing CO2 from hydrogen production plants and integrated pulp and paper mills led to the lowest impacts concerning all investigated indicators. The choice of how to handle multi-functional activities had a crucial impact on the assessment.
Highlights
The increasing penetration of renewable energy in the energy mix demands new technologies for energy storage
As far as the comparison among the CO2 source is concerned, capturing CO2 from cement plants had the highest impacts on climate change, human toxicity, particulate matter, photochemical ozone formation, acidification, terrestrial eutrophication, freshwater eutrophication, marine eutrophication, and freshwater ecotoxicity
Capturing CO2 from the air had the highest impact on ozone depletion due to the processing and transport of natural gas over long distances
Summary
The increasing penetration of renewable energy in the energy mix demands new technologies for energy storage. For long-term storage (weekly to seasonal), Power-to-Gas (PtG) is regarded as one of the most promising technologies for its potential of storing large amounts of energy into an transportable chemical vector [1]. Besides its potential as energy storage, PtG is inserted in the framework of Carbon Capture and Utilization (CCU), which is “a family of technologies that convert otherwise industrially emitted or airborne CO2 into fuels, chemicals, and materials” [2]. In order to verify the sustainability of the proposed solution, it is crucial to assess PtG impacts on broad boundaries, under several impact categories and different inputs and system architectures (e.g., electricity generation mix, carbon separation technology). Despite the abundant availability of CO2 , what remains untapped is the actual benefits of a large scale development of CCU, due to the variety of CO2 emitters and CCU conversion plants.
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