Japan, where forests cover 70% of the country's land, has a system to provide a large and stable supply of high-quality pulp from thinned lumber and offcuts. However, with the recent digitization of society, the demand for paper has been drastically decreasing, and there is an urgent need to develop new applications for pulp to replace paper. Since pulp production is enormous, amounting to several hundred thousand tons per year at a single mill, new uses must be found. On the other hand, ensuring resilience to natural disasters, such as the frequent occurrence of heavy rainfall disasters due to global warming, is a social issue facing Japan. Muddy soil generated in large quantities by large-scale construction projects and disasters needs to be treated and reused in an environmentally friendly manner. Pulp has a high-water absorption characteristic and is used as a water absorbent in diapers and other products in combination with polymer absorbent. Therefore, the suitability of pulp as a new material for treating muddy soil have been examined. As a result of evaluating the water absorbency of a total of six types of pulp, it was found that the pulp had superior water absorbency to that of absorbent derived from used paper, which has an established reputation as a muddy soil treatment material. It was also confirmed that regardless of the pulp manufacturing method, pulp derived from softwoods with longer fiber lengths had higher water absorbency.