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
by 10% per year [4], most of the PPS is currently disposed of primarily
in landfills or discarded carelessly in China. However, it is also
attractive biomass feedstock for production of fermentation products
such as ethanol [5–7], due to the high carbohydrate (such as
cellulose, hemicellulose) content. Additionally, PPS has some distinctive
advantages except for carbohydrate compounds, including
negative cost at many locations, no requirement for pretreatment
for making it amendable to enzymatic hydrolysis due to an extensive
mechanical and chemical processing previously imposed on
the paper raw material through pulping during refining, bleaching
and drying [8–10], and the potential availability of preexisting
infrastructure.