Evaluation methods and research progresses in bio-oil storage stability

Bio-oil is the liquid product of the fast pyrolysis of biomass. Recently, bio-oil has gained increasing attention for its direct use in combustion within boilers and furnaces as well as its use in automobiles and chemical materials after refining. Unfortunately, the composition of bio-oil is very complex. Aging occurs during storage, which leads to obvious changes in the physical and chemical properties of the oil. The poor storage stability of bio-oil restricts its extensive applications as a key renewable energy alternative. Viscosity and average molecular weight, as well as water and solid content can measured to determine changes in bio-oil. In this article, the testing parameters and technologies used for examining bio-oil stability and research progress in the field of bio-oil stability are reviewed. Emphasis is placed on thermal and oxidation stability. Scientific and technical developments towards improving bio-oil stability are also discussed. Furthermore, important aspects for consideration when developing experimental plans for bio-oil upgrades are examined. It also points out challenges to success with bio-oil upgrading in the future.