Abstract
Biocarbon is considered a promising alternative to fossil carbon for metal production, primarily for its potential
to reduce greenhouse gas emissions. However, native biocarbon is often brittle and lacks mechanical strength,
which causes it to fragment or break into pieces, leading to the formation of fines and dust. This material loss,
coupled with the risk of dust explosions and negative impacts on worker health, presents a significant challenge.
Densification is an effective way to upgrade biocarbon into products (e.g., pellets and briquettes) with enhanced
mechanical properties and increased mass/energy density. Nevertheless, short-term exposure to rain or high
humidity during transportation and storage can negatively affect the quality of these densified products. In this
work, we investigated the hydro-stability of biocarbon pellets through water immersion tests. The immersion
time ranged from 10 minutes to 2 weeks. Following the immersion tests, the pellets were air-dried, with weight
measurements taken regularly. The water uptake capacity (indicated by weight gain) of the biocarbon pellets
increased gradually over the first half hour and then stabilized until the 1-hour immersion mark, after which it
considerably increased with longer soaking times. During the air-drying process, the weight of the water
immersed pellets continuously decreased. The final weights after one week of air-drying were slightly lower than
the initial weights, indicating material loss occurred during water immersion. The impact of water immersion on
the mechanical properties was assessed using tumbler and hardness tests. The results clearly showed that
water immersion had a significant negative impact on the durability of the biocarbon pellets. The mechanical
durability of the studied pellets decreased from 97.64% to 96.13% after one week of immersion, and further to
91.76% after two weeks. Consequently, a greater amount of fines was generated after the tumbler tests as the
immersion time increased. Furthermore, water immersion also caused a decrease in the hardness of the
biocarbon pellets to varying extents. Results from this work indicate that densified biocarbon, such as pellets,
requires proper storage and transportation protocols to avoid intensive contact with moisture and water. Even a
short exposure time can have detrimental effects on mechanical properties and increase risks and vulnerabilities
related to dust formation.