At the beginning of the 1970s, OPEC (Organization of Petroleum
Exporting Counties) decreased the output of oil, which resulted in
a dramatic increase in oil price and the world’s interest in alternative
fuels. The aim was to become less dependent on oil and
to reduce the cost of expensive oil imports. Up to now, an interest
in production of gasoline substituting fuels is maintained in
many countries all over the world. For the development of gasoline
substituting fuels, ethanol production is widely focused on in
the world. Ethanol was generally produced from carbohydrates and
grains, which are also the main food for the human beings with
limited yield [1,2]. Developing non-food alternatives for ethanol
production is therefore important.
Biomass, or biomass-derived products, is considered to be one of
the most promising options for the use of conventional fossil fuels,
due to the foreseeable low cost and abundant resource [3]. Moreover,
production of renewable fuels from biomass offers benefits
in terms of sustainable resource supply, energy security and rural
economic development.
Pulp & paper sludge (PPS) is a solid by-product of pulping and
paper-making operations. The yield of PPS was 2628
×
104 t with
80% moisture content (MC) in 2007 in China, which would increase