PROCESS FOR CONVERTING PAPER RESIDUES TO FERTILIZER

PROCESSUS DE CONVERSION DES RESIDUS DE PAPIER EN ENGRAIS

English Abstract

A process is disclosed for converting shredded money
and food stamps withdrawn from circulation into a
fertilizer compound, namely a pumpable fiber mulch
including nitrogenous plant nutrients which can be
applied to the soil as fertilizer. Finely chopped
currency or food stamp residues are digested with mineral
acid and the resulting slurry is neutralized with
ammonium hydroxide to produce pumpable slurries useful in
hydraulic seeding.

French Abstract

Divulgation d'un processus pour convertir l'argent et les timbres alimentaires déchiquetés retirés de la circulation en un engrais, à savoir en paillis de fibres pompable comprenant des éléments nutritifs azotés qui peut être appliqué sur le sol comme engrais. Des résidus de devises ou de timbres alimentaires finement hachés sont digérés en présence d'acide minéral, et la boue résultante est neutralisée avec de l'hydroxyde d'ammonium pour produire des boues pompables que l'on peut utiliser avec un hydro-semoir.

Claims

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CLAIMS:
1. A process for preparing a fiber mulch from paper
residues, for use in hydraulic seeding, comprising the
steps of:
(i) cutting or chopping a desired quantity of said
residues to a fine state of division;
(ii) adding an aqueous solution of mineral acid to
the cut or chopped residues in a reaction vessel;
(iii) heating the acid/paper residues mixture to
produce a slurry containing substantially no solid bits
of paper; and
(iv) allowing the slurry to cool to room temperature
and reacting excess acid with a strong aqueous solution
of ammonium hydroxide to produce a pumpable slurry of
fiber mulch including ammonium salt of said mineral acid.
2. A process according to claim 1, wherein said paper
residues are selected from the group consisting of
currency residues and food stamp residues.
3. A process according to claim 2, wherein said mineral
acid is selected from the group consisting of sulfuric
acid, nitric acid, phosphoric acid and mixtures thereof.

Description

CA 02241394 1998-06-22
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FIELD OF THE lNv~!;NlloN
This invention relates to a process for the
environmentally acceptable disposal of paper residues,
particularly shredded paper currency and food stamps, by
converting such residues to mulch having agricultural
applications.
BACKGROUND OF THE INVENTION
(i) Use of Cellulosic Mulches in Hydraulic Seeding
The establishment of turf by spraying a mixture of
water, grass seed, fertilizer and cellulose fiber mulch,
commonly referred to "hydroseeding", has rapidly gained
acceptance by landscapers. The fiber mulch is made from
recycled materials such as wood by-products or recycled
newsprint and, to that extent, is an ecologically
responsible technique. Using simple and powerful pumping
apparatus now available commercially, a single person can
operate a hydroseeding system to apply seed, mulch and
fertilizer simultaneously to large areas on golf courses,
ski slopes, in parks, etc., so that labour costs are low
compared to other methods for establishing turf.
(ii) Disposal of Waste Food Stamps and Paper
Currency Withdrawn from Circulation
The efficient disposal of food stamps and shredded
paper money which has been withdrawn from circulation
(hereinafter referred to as "currency residues") presents
a serious environmental problem. At one time, currency
residues were routinely incinerated, but the U.S.
environmental protection agency has banned this procedure
as a source of pollution. Burial of shredded currency in
landfill sites is not an acceptable alternative, given
the enormous volumes of currency residues produced

CA 02241394 1998-06-22
annually and the ~llm;nl shing suitable landfill space
available.
The problem of disposal of currency residues is far
more difficult than for ordinary paper residues such as
used newsprint since the former are, for obvious reasons,
formulated to be highly water-resistant. In particular,
currency and food stamp paper stock do not pulp well when
agitated with water using the conventional pulping
methods applied to waste paper or wood by-products.
We undertook a research project aimed at developing
an environmentally friendly method for disposing of
currency residues and shredded food stamps. It was an
object of this project to recycle such waste products to
save landfill space and, if possible, to convert these
residues into a useful end product.
Consideration was given to converting currency
residues into mulch for hydroseeding as a possible
disposal technique to satisfy our objectives, but it soon
became evident that conventional mulching would not work
to produce a useable slurry. The "pulped" material
contained many non-reduced solid inclusions and, when
mixed with grass seed and pumped into the ground, would
"mat" into a compact layer which failed to produce
adequate growth.
We have since discovered that currency residues,
shredded food stamps and, indeed, all kinds of waste
paper products can be chemically reduced to a fertilizer
component that may be~applied alone, or with added
nutrients, to the soil.

CA 02241394 1998-06-22
SUMMARY OF THE INVENTION
With a view to achieving the objectives discussed
above, the invention provides a process for preparing a
fiber mulch from paper residues, for use in hydraulic
seeding, comprising the digesting of a quantity of finely
cut or chopped paper residues in a aqueous solution of
mineral acid such as sulfuric acid, nitric acid or
phosphoric acid, heating the acid/residues mixture until
a slurry is formed which has substantially no rPm~;n;ng
solid bits of paper in it and, after allowing the slurry
to cool to room temperature, reacting excess acid with a
strong aqueous solution of ammonium hydroxide to produce
a pumpable slurry of fiber mulch.
The slurry of fiber mulch is useful in convention
hydraulic seeding (hydroseeding) applications,
particularly as the ammonium sulphate by-product of the
mulch preparation is itself a plant fertilizer. The
technique of heating the finely divided paper residues
with sulfuric acid is effective in reducing otherwise
intractable paper stocks, particularly currency residues
and food stamp residues, so a root is provided to
disposal of these waste materials.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
The pretreatment of currency residue is of
importance in effective digestion and pulping of the
material with acid according to the present invention.
Currency residue is typically 1/16" x 6" shredded paper
("shred") which is visually recognizable as cut-up paper
money in various denominations. This material must be
cut or chopped to a fine powder. Grinding (as with a
mortar and pestle) or milling (metal ball grinding
machines) were found to produce a matted material which
is much more difficult to digest than the original shred.

CA 02241394 1998-06-22
The particles of shred are digested with acid under
conditions which produce a slurry containing few or no
bits of shred. Sulfuric acid has proved to be the
reagent of choice because of its price, low volatility
and apparent efficiency in tearing apart cellulosic
fibers.
Example 1
In prel;~;n~ry laboratory-scale tests, currency
shred was heated with sulfuric acid (reagent grade conc.
H2S04) diluted with water in a glass vessel equipped with
a reflux co~Aen~er. Conditions which produced a
substantially homogenous slurry are given in Table I
below.
TABLE I
SHRED [H2S04] H2o Time Temp. ' Results
() (mL) (mL) (h) (~C)
0.5 5 25 3 60-65 Slurry, few bits
0.5 0.5 10 3 Reflux Much finer
slurry, no bits
2.5 1.5 20 1 Reflux As above
Where the slurry is to be used as a hydroseeding
mulch, the lower limit of acid is determined by the need
for excess acid for subsequent reaction with added NH40H
to produce (NH4)2S04 at a concentration of 5~ or more.
The shred slurry can be pumped from the reaction
vessel and subsequently air-dried on plates or on a
rotating drum.

CA 02241394 1998-06-22
Example 2
The resistance of certain paper stocks to pulping
was ~em~nstrated by soaking currency residue and food
stamps at room temperature in "weak" sulfuric acid,
namely, commercial automotive battery acid.
Very little dissolution of the currency residue was
observed even after 26 days of soaking in the weak
sulfuric acid. The food stamp residue was found to be
only slightly more susceptible than currency residue to
dissolving in weak sulfuric acid.
Example 3
To 2.5 Kg of shredded currency was added 1.5 litres
of concentrated H2SO4 (-95~). To this mixture, twenty
litres of water was slowly added with stirring. The
mixture was heated to the boiling point, then allowed to
cool to room temperature. The pH was reduced to 5.5 by
the addition of a concentrated aqueous solution (~28%)
ammonium hydroxide, which required about 4.0 litres.
This was found to produce a pulpable slurry having a high
nitrogen content of about 22%.
Example 4
The hydromulch of Example 3 was field tested at a
number of sites and was found to produce comparable
results, in bringing up grass to conventional wood by-
product and waste newspaper mulches.
Example 5
The procedure of Example 3 was repeated using 1.0 Lof concentrated nitric acid instead of sulfuric acid.
This produced a pulpable slurry with a significantly
higher nitrogen content than that of Example 4.

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Example 6
The procedure of Example 3 was repeated using 1.0 L
of concentrated phosphoric acid instead of sulfuric acid.
A pulpable slurry was obtained after neutralization with
~mmo~;um hydroxide which contained both nitrogen and
phosphorous, which are essential minerals for plant
growth. This slurry was easily blended with slurries
produced in Examples 4 or 6 to produce a balanced
fertilizer mulch containing the optimum ratio of-nitrogen
and phosphorus for the desired application.
From these examples it will be seen that shredded
currency and food stamps, which are highly resistant to
break-up into a tractable mulch by conventional
techniques can be transformed into a fiber mulch which
contains plant nutrients for use in hydraulic seeding,
thereby addressing the serious disposal problem for such
waste paper materials, while converting them into useful
agricultural end product.