yard waste:
COMPOSTING IN
PAPERBAGS
.......................................
A New Jersey leaf compostingexperiment turns up one strategyf o r
successful diversion and reuse of vegetative wastes.
n some towns, vegetative wastes account for as much
as 20% of the total wastes. In the fall, vegetative
wastes create a peak in overall annual waste generation. Many municipalities must commit to special collection arrangements and crew overtime to collect
leaves from October to December.
At least one state has tried to do something about this. As
of Sept. 15, 1988, all of New Jersey’s 565 municipalities
are banned by the state’s mandatory recycling law from
sending leaves to landfills . . . even to transfer stations.
As a result, cities and counties in New Jersey are looking
into leaf collection and composting practices. Leaves and
other vegetative wastes can be turned into compost, and
that is the approach taken in Essex County, N.J. But the required composting of leaves has an impact on how theycan
be collected.
For some cities and towns, separate collection of loqse
leaves fits normal collection procedures and composting
operations. But in the past, the practice of letting residents
rake leaves out to the curb has caused serious problems
ranging from fires (lit by automobile catalytic converters)
to clogged sewers and the accidental death of a child playing within a pile of leaves in the street.
Some cities across the nation give free plastic bags to
their residents to wean them away from raking to the curb.
Unfortunately, plastic bags are inappropriate in composting
operations. They must be dumped out to allow the leaves to
decompose, requiring additional manpower and creating a
By PAUL A. PETTO
fetto is the recycling coordinator for Essex County, N.J. The article above is adapted and updated from a May, 1986, joint report
on the composting experiment by the county and the township of
West Caldwell.
further disposal need for the used bags. And, if the bags are
left in the compost, they become a contaminant in the final
product, which should be free of inorganics.
Can leaves be successfully and inexpensively composted
in biodegradable paper bags?In 1985, an experiment was
conducted to answer this question in the town of West
Caldwell, N.J., by the town and Essex County.
Project goals and design
The experiment had two goals: to test the usefulness of
bags similar to Union Camp Corp.’s maintenance bag (SF716) as a receptacle for leaves and yard waste for residential users; and to observe the results of incorporating this
bag into a composting system.
Particular activities undertaken were:
surveying public acceptance of this bag compared to
other bags for leaf collection;
gauging the effectiveness of this bag in holding leaves
and other typical yard wastes (twigs, weeds, garden debris)
under normal use and weather conditions;
composting the bags and leaves (according to guidelines provided by Rutgers University’s Department of Environmental Science); and
drawing conclusions on how to utilize a compostable
bag in collection and composting of leaves.
Two collections, two compost piles
In November, 1985, West Caldwell accepted a proposal by
the Essex County Division of Solid Waste Management to
cooperatively explore the goals stated above. Union Camp
supplied 500 “Trim Town” bags for the feasibility test.
West Caldwell’s public works employees distributed the
bags to approximately 40 homes; homeowners had been
notified in advance of the test. On Nov. 19, the bags, which
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Cornposting Bags Contd.
I
were set out at the curb, were picked up, brought to the site,
dumped (leaves intact), and spread about to allow exposure
of each bag to the 1,000 gallons of water that were added.
Two problems developed. First, because of inclement
weather, not all residents were able to collect and bag their
leaves. Second, it became evident that the bags collected
would not makea sufficiently large pile. While the height
and width of the window - 6 feet and 14 feet - were appropriate, the pile was not long enough (14 feet)to insulate
the core -where high temperatures must be maintained
for biological activity.
Union Camp supplied 500 additional bags and, after an
interruption of West Caldwell’s collection program, a second collection of bagged leaves, including the remainder of
the first distribution plus the 500 “new” bags, was completed on Jan. 10, 1986.
This second set of bagged leaves was also spread about
and soaked (with 1,500 gallons of water), but was not
mixed with the earlier pile so the decomposition rates could
be measured independently. Windrow size was approximately 14 feet wide x 25 feet long x six feet high. This
length would besufficient to insulate the interior.
Public acceptance
A total of 26 responses was received from the 36 residents
surveyed. Generally, the public was pleased with the performance of the bag, but preferred a system of closure.
The survey revealed the majority was pleased or very
pleased with the ease of packing and resistance to tearing,
but nearly halfwere disappointed with the bag’s capacity.
A slight majority found the paper bags better than plastic.
While few were willing to pay more for these bags than for
plastic, the majority were swayed by the environmental.
benefits.
Finally, a few solidly-positive comments were volunteered and Collection crews reported similarly positive
comments from residents, particularly regarding the ease of
packing and resistance to tearing.
Effectiveness of the bags in use
Effectiveness of the bag was gauged by residential response, by observations in use, and by monitoring the full
bags left outside exposed to the winter elements.
As noted earlier, there was a mixed residential response
to the usefulness of collecting leaves and yard wastes in
this paper bag. Most were pleased the bag stood open and
upright for packing (unlike plastic bags) and that the bags
had a high resistance to tearing (more than plastic). At the
same time, the paper bags’ capacity was considered undesirably low by many, and half the residents called for some
system of closure as the major improvement needed. Inter-
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WASTE AGE I MAY 1988
estingly, only one-fifth of the respondents found the bag
difficult to carry when full.
It should also be noted that while the paper bag is small
compared to the commonly used large plastic bag, many
residents commented that more leaves could be packed into
the sturdy paper bag. Therefore, fewer paper bags would be
needed for the same collection job.
As for the performance of the bags in transport from the
curb to the composting site, the collection crews found the
bags adequately strong and easy to handle. There were no
burst bags to clean up on the route.
Finally, the performance of those bags left exposed all
winter was outstanding. The bags showed discoloration but
were still strong enough to hold their contents without ripping when lifted. This is important when considering that
bags may be left at the curb for days in the rain.
Extent of decomposition in windrows
As might be expected, the bags in the two piles decomposed at differing rates. Because the first pile (from November) was of insufficient size, temperatures were unable
to rise adequately and decomposition was stifled.
So it was no surprise that, when turned in March, 1986,
only the center of the first pile had any significant biological activity. It should be noted that the predominant leaf
type in thatpile (oak) is among the most resilient types.
While there was concern that the voids between the bags
were a possible reason for improper heat retention, ample
activity in the second, larger pile disproved that.
As of March, 1986, decomposition in the second, larger
pile (from January) was significantly better. Interior heat
and moisture conditions appeared optimal. In samples from
most points in the pile except the exterior, the bags were
nearly indistinguishable from decomposing leaves in color
and texture. Note that this second pileawas a mixture of leaf
types.
Conclusions
The following conclusions are based on an analysis of participants’ observations, residential surveys, and the collective experiences of those involved in the test.
Usefulness for collection: The Union Camp maintenance
bag, actually designed for other purposes, has been demonstrated to benot only an acceptable substitute for plastic
bags in leafcollection, but also a desired substitute at the
same price. In the opinion of the residential users, the advantages of this bag (ease of packing, resistance to tearing,
remaining upright when full) were great, while the cited
disadvantages (low capacity, no closure) were only considered serious by a minority.
Acceptability: The bag’s acceptability would be even
higher (to residents surveyed) if the following modifications (likely to increase cocts) were made:
Table One
Cost Comparison - Using Paper or Plastic Bags
Volume: While volume of each bag is the same, 25% fewer paper
bags are needed due to their demonstrated additional holding
strength.
Purchase Price:
60,000
paper
bags
75,000 plastic bags
(30-gallon)
$0.24075 each
$0.0895 each
Cost Difference:
=
=
$14,445.00
$ 6,712.50
$ 7,732.50
Disposal Costs for Plastic Bags With leaves:
1. Plastic bags filled with leaves occupy 0.134 cubic yards
each (10% of volume allowed for closure).
2. 75,000 bags x 0.134 cubic yards = 10,050 cubic yards.
3. At 500 pounds per yard, total weight of leaves and bags =
2,500 tons.
4. Essex County Disposal Rate = $101.65 per ton.
Cost for disposal of 2,500 tons = approximately $250,000.
Disposal cost:
$250,000
MinusCost Difference: -7,732.50
Paper Bag Net Savings: $243,267.50
Increase capacitylsize of bag: while bag makers have
the ability to produce bags up to 18 inches x 12 inches x 50
inches, the current size is 16 x 12 x35.
Provide a closure mechanism: Half the respondents
recommended this improvement. Alternatively, residents
could be given closure recommendations with the bags.
Price of paper bags vs. plastic
While the paper bag is a viable substitute for plastic bags in
leaf collection, the current wholesale cost for the paper is
three times as much as comparatively-sized plastic bags.
This price difference will discourage municipalities from
making the substitution when they buy bagsfor residents.
Similarly, residents (as consumers) are more likely to opt
for the lesser price of plastic. Although it might be feasible
to mandate that residents use paper bags, it would not be
politically or publicly popular if residents had to paythe
higher price.
On the other hand, given that the paper bag may allow a
municipality to begin composting while problems with
plastic bags prohibit it, the savings in disposal costs would
be more than enough to offset the higher cost of the bags.
See Table One.
In addition to the bottom line in the table, there would
also be significant savings on transportation costs and vehicle wear. Over 200 round-trips to disposal areas would be
saved in this example. Finally, benefits could accrue to
municipalities that would no longer expend time and labor
to open (and dispose of) plastic bags at composting sites.
These net savings could be applied to the costs of operating
a separate collection system and a composting site. I
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