High moisture content of the NR sheets encourages fungi growth. This is a serious problem in NR production, since it may affect the production conditions as well as the quality of the final products. Therefore, antifungal agents need to be added during the NR production. Most commercial antifungal agents are highly toxic and not environmental friendly. An environmentally friendly antifungal agent with low toxicity is desired. Acetic acid and phenolic compounds contained in wood vinegar have been reported as anti-germination agent [2] and termiticides [4]. Due to their acetic acid and phenolic compound contents, Guayle wood vinegar and biomass slurry exhibit fungicidal and termiticidal properties and can be used as wood preservatives [5] and [6].