1. Introduction
Recently, the world’s demand for energy has been increasing
because of economic growth and population growth in developing
countries. In addition, concerns about fossil fuel depletion
and global warming have arisen worldwide. At present, 81% of
the world’s total primary energy demand is supplied by fossil
fuels (International Energy Agency Therefore, natural
energy sources are receiving attention as alternative energy
sources, although they are required to be used more efficiently.
Biomass is one of the best potential energy sources of alternative
fuels, because it can be converted into various physical states (e.g.,
gaseous, liquid and solid). Additionally, biomass is considered to
be a “carbon neutral” fuel
However, it has not been commonly used as a source of alternative
fuels. Because the amount of heat generation from biomass is less
than that from fossil fuels, and a stable supply of biomass is difficult
to maintain throughout the year To expand biomass usage, it