To reduce or eliminate the amount of binder used in making fuel logs or pellets, bonding mechanisms between particles need to be fully explored, zeta potential plays an important role in the chemical properties of the interface between solid and liquid. This study examined the zeta potential characteristics of some biomass materials and the effect of zeta potential on compaction of biomass materials. The tests showed that the zeta potential of the biomass changes with water-contact time, concentration, temperature, additives, etc. It was found that adding polyethylene oxide (Polyox) decreases the zeta potential of biomass and improves the strength of compacted biomass logs. Therefore, monitoring and controlling the zeta potential of biomass mixture may be helpful to compact stronger biomass logs without using binder.