LIFE CYCLE THINKING TO HYDROGEN STORAGE SYSTEMS
Fuel cells and hydrogen are among the most promising solution for decarbonizing trucks, buses, ships, trains and large vehicles, providing the mobile market with a substitute for today’s combustion engines. However, the technology for hydrogen storage is still in its early stages of development. In this context, Mast3rboost is implementing a new generation of ultraporous materials for hydrogen adsorption, including activated carbons (Acs) and high-density metal-organic frameworks (MOFs).
Life cycle thinking to hydrogen storage systems involves balancing feedstock selection (utilizing renewable feedstocks such as waste biomass instead of coal-based activated carbon), production processes (improving activation techniques) and waste management (biochar as by-product) to minimize the overall environmental impact.
Due to the novelty of these materials, there is currently no standard Functional Unit (FU) for activated carbon across Life Cycle Assessment (LCA) studies. Then, choosing an appropriate FU to perform an LCA study is challenging. This must be consistent and comparable, and ultraporous materials may require a different performance metric, such as focusing on the amount of gas adsorbed per volume of material, to capture their value fully. Besides, adsorption capacity varies depending on the type of carbon, the feedstock used and the activation process, making it challenging to compare materials and its environmental impacts. Consequently, the FU should be equivalent in scope (e.g., “adsorption of X grams of hydrogen”), allowing a direct comparison.
The LCA performed on the first batch of Acs and MOFs in the Mast3rboost project showed that the performance of these materials is directly related to the environmental impact. Likewise, achieving higher surface area requires more intensive activation processes, which involve heating to high temperatures, thus consuming more energy. In addition, chemical activation may require significant water use to achieve high surface areas. Therefore, an optimal balance between surface area, pore size distribution, feedstock selection, and application-specific needs is of paramount importance to minimize the environmental impacts, while maximizing performance.
Lastly, after selecting an appropriate material for adsorption, the demonstrator of the entire storage system is assessed by performing a hotspot analysis to identify the materials, production steps, or processes that contribute most to the environmental impacts, identify areas for improvement, and provide recommendations for future scale-up initiatives.