In this study, we focused on the purification of biohydrogen by indirect pyrolysis. Syngas typically contains small amounts of impurities (e.g., NH₃), which negatively affect the fuel cell operation. Earlier, our group has developed removal technologies using solid adsorbents. Additionally, we estimated the adsorption performance considering environmental aspects based on life cycle assessment. In this study, we focused on the NH₃ removal capacities of two different adsorbents: hydroxyl aluminum silicate clay (HAS-Clay) and natural clay (KanumaClay). We fabricated an experimental apparatus to evaluate the adsorption performance. The results show that the maximum adsorption of HAS-Clay is 2.90 g NH₃/100 g sorbent, whereas a maximum adsorption of 2.02 g NH₃/100 g sorbent was obtained by using Kanuma-Clay. Both adsorbents have the same allophane composition, which contributes to the adsorption performance. However, the environmental impacts of HAS-Clay and Kanuma-Clay differ. Thus, we evaluated their eco-burdens on the NH₃ removal.