A Fundamental Review of the Relationships between Nanotechnology and Lignocellulosic Biomass - The Nanoscience and Technology of Renewable Biomaterials - page 36

locations. Nanotechnology needs in this area are to develop cost-effective methods to
reduce or eliminate odorous kraft emissions beyond the mill property.
The US pulp and paper industry discharges about 45 m 3 /ton (12,000 gallons/ton) of
wastewater. Although this is a significant improvement over decades past, the indus-
try is still among the largest industrial water consumers. Developing ways to reduce
water use in the mill and/or to recycle the process water within the mill for reuse
would significantly lower wastewater treatment costs. Low-quality thermal energy in
the wastewater could potentially be captured in the water recycling process and the
industry's water use and effluent discharges would be greatly reduced. Almost all of the
wastewater generated from the pulp and paper industry is treated in wastewater treat-
ment plants made up of settling ponds (primary treatment) and biological purification
(secondary treatment). The treatment process involves multiple steps and generally
requires significant amounts of electrical power, adding to manufacturing costs and
resulting in emissions from power production. In addition, many of these systems
are reaching the ends of their useful lifetime and will need to be renovated or replaced
at significant capital expense to the industry. Nanotechnology needs in wastewater
treatment are to (1) develop alternative methods for wastewater treatment that are less
energy- and capital-intensive than current biological effluent treatment systems and (2)
develop low corrosion nanocoatings and nanomaterials to prolong the life of capital
equipment.
Current recycling mills are complex, require numerous separate unit operations, and
are energy inefficient and costly to operate. These operations need to be streamlined to
improve operating efficiency, lower capital costs, and reduce energy and water consump-
tion. Technologies to improve yield, recover all on-grade fibers, and tolerate or remove
contaminants are also needed. Because of the variability in recovered paper collection
and sorting systems across the US, gross contaminants and out-of-spec fiber contin-
ues to reach the recycle mill. Moreover, lower quality and rejected fibers - including
shorter, inferior fibers from recycled paperboard imported from Asia - are also gener-
ating an increased volume of solid waste in US recycled fiber mills. Overall recycling
goals focus on sorting and recycling mill wet-end equipment and processes such as
pulpers, screens, cleaners, and flotation devices to significantly improve paper fiber
recovery, fiber utilization, and energy efficiency in order to reduce fiber yield loss by
50%; improve contaminant removal by two-thirds; reduce overall costs by as much as
US$40 per ton; reduce energy use by 50%; and reduce water use by 50%. Nanotech-
nology needs are to: (1) develop functional nanomaterials to enable paper and fiber
tagging; (2) use nanomaterials to facilitate ink removal (i.e. de-inking) and contaminant
removal; (3) develop low corrosion nanocoatings and nanomaterials to prolong the life
of capital equipment; and (4) develop nanomaterials to improve recyclability of paper
and paperboard products.
Processing wood products requires large amounts of energy, and represents the single
highest wood processing cost. Drying processes account for the largest share of energy
consumption. Energy used to cure wood composites and to dry lumber and other wood
products in kilns accounts for 50-80% of the manufacturing energy consumed in these
operations. More efficient wood drying and curing processes, better technologies for
utilizing sawmill residues for energy, and methods for utilizing low-grade energy from
available engines and motors could significantly reduce the purchased energy-intensity of