Recovered Fiber

Wastepaper Recycled Paper

Secondary Fiber

Paper Stock Recycled Fiber

PAPR 3531

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 Fiber for Papermaking

General fiber classifications

• Virgin (wood) fiber
• Secondary fiber (from recovered paper)
• Specialty fibers (non-wood plant, synthetic)

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 Why Use Recovered Fiber?

• Economics (cheaper fiber)

• Government policies and regulations
• Customer demand (“Green”)
• Public relations (“Green”)

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 Recovered Fiber for Papermaking
Factoids
• Worldwide, 50-55% of the fiber used to make paper and
paperboard in 2009 came from recovered paper
• American Forest & Paper Association (AF&PA) reported
that a record-high 63.4% of the paper consumed in the U.S.
was recovered for recycling in 2009
• Purchased recovered paper and/or market deinked pulp is
used at over 80% of all U.S. mills to provide at least a
portion of the mill’s fiber needs
• About 20 million tons of the paper recovered in the U.S.
each year is exported to other countries (significant
compared to U.S. paper production of ≈90 million tons/year)

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Exporting of U.S. Recovered Paper

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 Paper Grades
• Paper Grade: Term for the type of paper(s) or level of
quality of paper(s) based on use, manufacturing history,
appearance, and raw materials
• The Institute of Scrap Recycling Industries (ISRI) recognizes
51 primary grades and 35 specialty grades of paper for
possible recycling into new paper
• Two major classifications for recovered paper are
· Post-consumer – Paper collected from homes and offices
· Pre-consumer (post-industrial) – Paper collected as
converting and printing scrap; newsstand returns and
printers’ overruns; obsolete inventory from mills,
printers, and others; damaged or off-specification stock

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 USEPA Procurement Guidelines
for Paper and Paper Products*
Examples Post-
Paper Consumer Total Recovered
Product Content Fiber Content

Printing & Writing Grades 30% 30%

Bathroom Tissue & Towel 20 - 60% 20 - 100%

Newsprint 20 - 85% 20 - 100%

Brown Bag & Wrapping 5 - 20% 5 - 60%

Corrugated Containers 25 - 50% 25 - 50%

Folding Carton 40 - 80% 100%

* EPA’s recommended content levels for paper products bought by Federal

agencies
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Some Paper Products Made from Recovered Paper

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 Contaminants in Recovered Paper

• Level of contamination in recovered paper can be severe,

particularly with post-consumer grades

• Contaminants result from

· Original manufacture of the paper
· Finishing, converting, and printing operations
· Subsequent use and collection

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 Contaminants in Recovered Paper
• Potential contaminants include
· Clays, starches and other filler and coating additives
· Dyes, colored pigments and inks
· Waxes and adhesives
· Metal pieces such as wire, staples, nails and foil
· Polystyrene foam, polyethylene film, and other plastics
· Glass, sand, and dirt
· Unusable fiber (e.g., wet strength or too short)
• Materials purged during processing are termed “rejects”

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 Processing of Recovered Paper
• Purpose: To produce fiber with characteristics, including
cleanliness, suitable for manufacturing the intended end
product
• As a general rule, the processing system should
· Minimize contaminant fragmentation
· Remove contaminants as early as possible
• A generic processing system might have the following major
steps
· Hydropulping (aka “repulping” or just “pulping”)
· Coarse cleaning and screening
· Deinking (if any)
· Fine cleaning and screening
· Bleaching (if any)

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 Hydropulping
• Hydropulping is the wetting and fragmenting of
recovered paper into individual fibers
• Hydropulpers are most often cylindrical vats with an
impeller at the bottom
• Associated with the pulper are devices for removal of
some coarse contaminants

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 Cleaning and Screening
• Cleaning and screening steps separate contaminants
from fiber
• With screens, particles are separated on the basis of
size, shape and deformability
• With cleaners, particles are separated based primarily
on density but also on size and shape, by applying
centrifugal force

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 Deinking (Ink Removal) Processes
• There are two basic deinking processes, washing and flotation,
and some mills use both because they are complementary
• Wash deinking is
· A dewatering step that retains fiber on a screen or perforated plate
· Better at removing filler, coating, and small ink particles, ~1 to 10
µm in size
• Flotation deinking
· Removes ink particles by having them attach to rising air bubbles
· Is better at removing relatively large ink particles, ~10 to 100 µm
in size

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 Deinking Chemistry
• Chemicals are added, mostly at the hydropulper, to improve
deinking
• Chemicals may include
· Sodium hydroxide to help with ink-fiber separation via fiber
swelling
· Hydrogen peroxide for preliminary bleaching
· Sodium silicate for dispersing and stabilizing ink particles
(reducing re-deposition onto fibers)
· A chelating agent to inhibit decomposition of the peroxide
· Synthetic surfactants or soaps to help separate and stabilize
ink particles

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 Bleaching
• Most deinked pulp is bleached to whiten it before it is shipped
offsite as market pulp or used onsite in paper production
• Common bleaching chemicals for recycled pulp are
· Hydrogen peroxide (an oxidant)
· Sodium hydrosulfite (a reductant)
• Other possible bleaching agents include
·Formamidine sulfinic acid (FAS)
·Chlorine dioxide
·Oxygen
·Ozone
• Chorine gas and hypochlorite are rarely if ever used anymore

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 Rejects

• Processing of recovered paper often generates a significant

amount of rejects

• On the high end, rejects from cleaning and deinking mixed

office waste (MOW) to produce market pulp can represent as
much as 40%, and possibly more, of the incoming paper

• Deinking mills characteristically produce more WWTP

residuals than other production categories

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Rejects

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