Life-Cycle Assessment of Adsorbents for Biohydrogen Production

Adsorbents are used to remove impurities such as carbon monoxide, carbon dioxide, methane, and hydrogen sulfide in the pressure swing adsorption process of biohydrogen production. These impurities are present in the produced gas along with hydrogen and often cause voltage reduction in fuel cells and shorten the lifespan of catalysts. Zeolite A is a typical adsorbent, and more recently, hydroxyl aluminum silicate clay (Has-Clay) and Kanuma clay have been suggested as alternatives. We conducted a life-cycle assessment (LCA) of zeolite A, Has-Clay, and Kanuma clay, and evaluated their environmental impact based on the ReCiPe midpoint method. Kanuma clay had the least impact in all of the environmental categories. The largest contributions for zeolite A and Has-Clay were in the categories of climate change and fossil depletion. In the climate change category, production of 1 kg of Has-Clay and zeolite A was estimated to emit 17.142 kg CO2 eq and 2.352 kg CO2 eq, respectively. In the fossil depletion category, the values were estimated to be 3.999 kg oil eq and 1.039 kg oil eq, respectively. These LCA results will be useful in designing and using adsorbents in pressure swing adsorption processes to meet environmental challenges associated with sustainable biohydrogen production.