The First Year with Wet/Dry Composting: A Report from …infohouse.p2ric.org/ref/06/05481.pdftwo wet/dry composting demonstration ... The province and the city have recently agreed

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by Paul Taylor Paul Taylor is president of Compost Man- agement, which operates 12 windrow composting facilities in Ontario, including two wet/dry composting demonstration facilities. Elora, Ontario-based Compost Management also conducts composting research. This at-ticle is based on a speech presented to the second annual conference of the Composting Council of Canada in November in Ottawa. ,

After one year of a wet/dry composting demonstration project, some preliminary findings are discussed.

34

The first year with wet/dry composting: a report from the field In October 1991, the City of Mississauga, Ontario, together with The Mississauga Clean City Campaign and the Region of Peel, embarked on research into wetl dry residential waste collection systems. “WetIdry” refers to any type of program where the “wet” components of the residential waste stream are source- separated in the home and collected separately from the “dry” components. The chief variations include two-stream (wet and dry) and three-stream (clean wet, clean dry and residue waste).

Four demonstration-scale programs are now underway in Ontario to research the practicality of these collection systems. As originally defined, the Missis- sauga project was to last for one year, and was funded almost 100 percent by the Ontario Ministry of the Environment. The province and the city have recently agreed to extend research on collection for a further nine months, until June 1993.

The role of Compost Management in the project was to design and supervise the construction of a wet/dry composting facility, and then operate it on a turnkey basis. We also operate the Region of Hal- ton’s wet/dry composting demonstration site. This article reports on what has been learned about source-separated wet waste collection programs, after the first year of work in the field.

Background The existing program collects source- separated organic wastes from a high- rise building, the kitchens of the Missis- sauga General Hospital and four garbage collection routes. These materials are collected using a variety of different systems to contain or package them and are hauled to a demonstration composting facility constructed by the city for the duration of this project. The various streams of waste are composted on-site, each in a separate windrow. In this way, the effects that each of the different collection systems might have on sub-

sequent composting operations and compost quality can be gauged.

The primary objective of the project is to test a variety of collection systems for source-separated organic wastes, and to try to identify which collection system might strike the best balance of cost- effectiveness, conveniente and potential for waste diversion and high compost quality.

A secondary objective of the project is to demonstrate the composting of this material using a very low-cost technology that has generally been used only to compost yard wastes, and to monitor the effectiveness and environmental effects of the use of this technology.

There can be little doubt that all par- ticipants in the project have learned a lot about the potential for these types of collection systems. Despite this, no single collection approach has been identified that seems ideal or suitable for recom- mendation for a citywide roll-out. As well, parallel research underway in Guelph, Halton and the Toronto Metro regions in- dicates that no clearly successful collection approach emerges out of that work yet either, though new ideas continue to be tried.

However, all of the work that has been undertaken to date points the way toward a clear narrowing of the options. While a workable system for collection of organics has not yet been found, some clear ideas have developed about what appears to be unworkable, and thus not be suitable for further pursuit.

The discussion below summarizes some of our general findings that have come out of the work to date, and offers some implications for seeking a better approach.

Two versus three streams The city’s demonstration project includes three three-stream routes (one each in paper bags, plastic bags and rigid containers) and a single two-stream route.

Resource Recycling January 1993

The City of Guelph, in some of its earli- est work (l), was able to establish that its variation on the two-stream approach ap- peared able to capture a greater per- centage of the organic waste stream than the three-stream program; however, the practicality of “cleaning up” the organic material that is produced by the two- stream approach sufficient to develop a good, marketable compost remains un- proven. While there are some obvious savings in collection on the two-stream side, the quality of the organic stream produced may be too poor.

Samples of some of the compost from our two-stream windrow were submitted for laboratory analysis. They were able to meet the Ministry of the Environment’s stringent guidelines for compost quality (2). Nonetheless, this compost is very highly contaminated with inorganic contaminants, despite very intensive hand- sorting of the incoming feed materials, and thus does not represent a sustain- able approach to the production of a first- quality grade of compost.

In particular, significant quantities of household hazardous wastes (HHW) were recovered from the organic .$ream

on this route, including sharps such as razor blades and hypodermic needles. One of the principal flaws in the two- stream approach is that it means that HHW must either be deposited in the wet stream or the dry stream - there is no “waste” stream left. Although many of the sharps were recovered from the compost derived from our two-stream route, screening the material will not recover all of them.

One might propose that this problem will disappear once effective HHW collection programs are in place. The fact remains, however, that even the best, most expensive programs seem to be able to capture less than 10 percent of the available HHW - they just aren? working. So HHW is going to stay in one or the other of the two streams for some time yet to come.

The compostability of diapers Two of the collection routes included diapers (and sanitary napkins) in the definition of “organic.” Though there were some sanitary napkins routinely found in the loads from these routes, there were always substantial number of diapers in-

cluded (3). Most of our comments therefore relate to our experience with the diapers.

Most parents, after removing the diaper from the Child, roll it up into a ball and then use the self-adhesive tapes provided with the diaper to tape it closed, so that no leaks or odors may escape.

The composting system that has been employed to serve our research project, by design, contains no up-front shredding of waste (other than shredding of separated brush). Up-front shredding should not be included in a system of any scale, since it would also shred and disperse the film plastic, hypodermics and dry cell batteries that we have encountered often in the feedstock.

Although our project employs a windrow turner that uses teeth to lightly abrade and mix the material in the windrows, it does not pulverize in the conven- tional sense of solid waste shredding equipment. Consequently, the diapers in the windrow are almost entirely unaf- fected by the turning process. Despite re- peated passes of the turner, sufficient to compost the readily accessible organics, the diapers remain largely unopened and

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36 Resource Recychg January 1993

inaccessible to degradation. The vast majority of them appear to be still unopened when the rest of the material is fully composted and stabilized.

In May 1992, the city discontinued diaper collections in one of the two routes in which they had originally been included, and will remove them from the second route in January 1993. We would not recommend sanitary napkins for in- clusion either, since they are often rolled and packaged after use in small, sealed plastic bags.

If the diaper and napkin producers ultimately develop truly compostable back- ings on their products, allowing the whole product to be compostable, it may make sense to re-examine this question. This research work is taking place.

Using plastic collection bags Plastic bags were supplied to residents as the primary intended packaging system for their source-separated organics in the two-stream route and one of the three-stream routes. Both a small “kitchen catcher” bag and a larger, clear yard waste bag were made available. Similar tests are being undertaken in Hal-

ton, Guelph and the Toronto Metro regions.

The primary advantages in the use of plastic bags are cost and availability. One disadvantage in’the use of plastic bags is that the use of plastic - as opposed to clearly degradable paper - may subtly encourage residents to include other noncompostable inorganics.

But the largest disadvantage to using plastic bags is the problem of debagging the yard debris. This is already a significant issue in the collection of yard waste because debagging yard waste by hand is extremely time-consuming and de- manding work. The most common solution to this problem for yard waste in Ontario has been to debag the yard waste right at the curb.

In Ontario, only the Durham and York Region yard waste sites are still composting yard waste commingled with the shredded plastic bags, and are trying to screen the plastic out later.

Although many systems have been created to debag mechanically, none of them appear to do so perfectly. Sustain- able composting programs cannot be built on the assumption that compost that

contains even small but obvious shreds of residue plastic is marketable. Mechan- ical debagging is not a proven approach at this time.

The work done in Mississauga illus- trates just how much more complex the debagging discussion can become. Some residents are placing bags of food waste within larger bags of yard waste, though they are supposed to be set out separately. There may be many such bags within bags within bags. In addition, all of this material is frozen in the winter; in many cases, part of the plastic bag is actually folded and frozen into the organics. Under these circumstances, no type of debagging will likely ever be pos- ible.

It has been suggested that the plastic shreds can merely be removed at the end of the process, by intensive screening. Such screening is relatively expensive, but perhaps more importantly, leaving the plastic shreds in the compost until the end means that all operations up to that point (including curing and product stock- piling) would ideally need to be enclosed to prevent the distribution of wind-blown plastic litter. b

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37 Resource Recycling January 1993

For these reasons, the use of small plastic bags for the collection of food wastes in future programs is not recommended, but the use of plastic bags for pure yard wastes could be considered, provided the debagging of such material can be made reasonable. It should also be noted that considerable time has been spent trying to involve the manufacturer of the bags in helping find a solution to the debagging issue. The company has been quite pro-active in developing debagging technology for the dry side; un- fortunately, there was no meaningful help from them on debagging wet materials.

Using paper collection bags One of the three-stream routes used con- ventional, wet-strength, kraft paper yard waste bags for yard waste, and a special, smaller experimental paper bag for food wastes. Only one other program, in Brooklyn, New York, uses the smaller bag on a trial basis. The smaller bag is also made of wet-strength kraft paper, but is lined with cellophane to make it leak-resistant. The cellophane is intended to be compostable, since it is not a true plastic, but is derived from cel-

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lulose. In fact, the bags have composted The chief barrier to the broader use of in the windrow and have performed paper bags lies in dealing with their bulk, largely as expected. when empty, in storage; the high cost of

the bags; and effective methods to dis- tribute them to residents.

The chief solution to all of these problems lies in moving to user-pay garbage collection. If residents have to pay some- thing on the order of $1 per bag to set out garbage, there is suddenly a strong incentive to purchase a special bag for organics collection. This has worked for yard waste programs in the U.S. Unfortu- nately, none of the current wet/dry pilots is being undertaken in a user-pay environment, so the effect is unknown.

Using rigid collection containers The third three-stream route uses rigid containers to package the organic wastes. This approach has also been used in Guelph. As in Guelph, it has been Mississauga’s experience that residents commonly line the rigid plastic carts with plastic bags, to prevent the interior of the carts from becoming soiled. This, of course, largely defeats the pur- pose of the carts, which is to replace the bags with a reusable system that elimi- nates the need for debagging.

Carts are expensive, although they may not ultimately be as expensive when compared to continua1 municipal provi- sion of bags. The apparent success of using carts in Germany for composting collection suggests that to dismiss them from further study in Ontario may be pre- mature.



2 Perhaps more effective promotional Scotia. That program, which relies en-

and educational programs would help tirely on European-style carts and pro- keep plastic out of the organic containers. hibits the use of bags, seems to be avoid- There is currently another wet/dry dem- ing many of the contamination problems onstration project operating in Lunen- that have been experienced in Ontario. burg, Bridgeport and Mahone Bay, Nova

Winter in Mississauga, Ontario and the Re- gion of Peel, where wetldry composting is taking place, poses the problem of how fo separate frozen organics from the plastic bags that contain them (1). Separating plastics and contaminants from compost is a problem, as evidenced by this worker hand picking plastic debris from the compost (2).

Commingling brush with other organics All four of the collection routes include brush in the definition of organic waste. This material is collected alongside the other organics and is commingled in the packer truck with them.

As described above, by design the composting system does not include a shredding stage of pre-processing. Be- cause the brush obviously has to be shredded or otherwise size-reduced to facilitate composting, it must then be separated from the other organics on-site for processing. Separating the brush from the commingled load is quite difficult, and



must be performed manually. Separating it in this way would not be recommended in a citywide program.

The Metro Toronto wet/dry program has encountered the same problem, and has had to manually separate all the brush that has come in since the project started. This material has been landfilled, pending the shakedown of a recently installed shredder. Even so, brush will still have to be pulled out of the commingled load manually.

Thus the brush either needs to be collected separately from other organics, or the system has to be based on up-front shredding of the entire feedstock, contaminants and all - which again is not recommended.

Promotion and education The city used a high-profile promotional program, delivered to residents’ homes, to outline how residents should separate their wastes and participate in the program. Although subsequent promotional efforts have helped, the outreach efforts made by the city to date have been un- able to produce good, consistent and widespread participation in the prggram. It should be noted that this is a problem

shared by all of the wet/dry demonstration programs operating in Ontario.

Participation rates in Ontario’s famous curbside recycling collection programs tend to be a consistent 75-t percent, across a variety of demographic vari- ables. These participation rates tend to be achieved in the first year of new programs, and are then sustained. By com- parison, participation rates in the wet/dry projects tend to be at best about 50 percent, with the numbers falling off in the winter, when only food waste is set out. Some of the stated participation rates may also be inflated by households that are coincidentally setting out separately bagged leaves or bundled brush, without realizing that they are therefore participating in the program.

Subsequent work in this area will con- sist of more focused and intensive promotional and educational efforts, which will include a heavier emphasis on graphic, rather than textual communica- tion.

Defining organic All four of the routes included quite broad definitions of what constituted acceptable

“organic” wastes, largely in an attemgt to maximize diversion. The spectrum of what was acceptable in one route or another included paper towels, facial tis- sues, animal droppings, kitty litter, diapers, ashes, vacuum cleaner bags, sanitary napkins and nonrecyclable paper products.

Starting the program with such a broad definition of what’s compostable did not lend itself to sending a clear message to participating residents; it may have been better to start with a more modest definition (e.g., yard and food wastes only).

While the demographics in the study area were perhaps different than in Mis- sissauga, the Halton program initiated collections with the full spectrum of yard wastes, and then added vegetative food wastes after the first three months. It is our sense that Halton has had much less difficulty with inorganic contaminants than any of the other wet/dry programs. In that case, its organic contaminants have been well less than 1 percent of the incoming feedstock.

As an aside, to include facial tissue within the definition of organic in this program has had the effect of inviting contamination by all of the other things

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rourinely found in bathroom waste bas- kets, including razor blades, makeup packaging and pharmaceuticals.

Collection staff and collection costs Collection of the wastes in this project are performed by Laidlaw Waste Systems,

*) the city’s garbage collection contractor. Laidlaw has been very cooperative in allowing its collection staff to take the time to examine each bag of source- separated organic materials on the Street, and to reject bags that are grossly contaminated.

The importance of the role played by Laidlaw staff has been underscored whenever the usual swamper on the truck is on sick leave, holidays or tem- porarily transferred to other duties. Re- placement staff have not always been able to maintain acceptable quality control. This is not a reflection on the contractor, but rather a reflection of the relatively straightforward nature of the work that is normally performed by waste collection staff. The Laidlaw employee as- signed to this duty for the duration of the program has been key to the success that has been achieved so far,- we are

painfully aware when he is not on the truck.

Laidlaw’s contract with the city is also structured such that it is paid by the weight of the material brought in to the compost site. In hindsight, this removes the incentive for Laidlaw to want to take the time and collect only the cleanest material off the Street.

In general, collection systems should be structured so that contractors and em- ployees are rewarded for hauling the maximum amount of clean organics to the composting site, while at the same time penalized or discouraged from hauling contaminated organics. Perhaps the same contractor should have to haul the residue away from the compost site, and have to pay the city a weight-based pen- alty for residue.

Information feedback Most curbside recycling collection programs achieve much of their quality control by undertaking some degree of curbside sorting, leaving behind incorrect materials in the box. This provides a very direct message to residents, specific to their own separation practices, and con-

tinually reinforces what constitutes correct separation behavior.

None of the organic collection programs in Ontario offer any such type of direct feedback to curbside recycling par- ticipants; consequently, the programs collect whatever the residents set out - contaminated or not. This has under- standably been done because of the nature of the material, yet this may be in some ways a fatal design flaw that will always hinder any attempt to remove contaminants.

To date, the approach has been to collect contaminated material and attempt to devise systems at the compost facility to cope with and remove that contamination. The chief flaw with this approach is that there is no inherent mechanism to correct the behavior of the specific waste generators that are the sources of contamination.

It can be readily imagined that if curbside organics collection staff could somehow complete at least a cursory sor-t of the material on the spot, and leave re- jected inorganics behind for the resident to deal with, significant improvements in feedstock quality could take place. Laid-

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law has looked at the possibility of undertaking such a trial.

In this type of program, there are three opportunities to remove contamination - in the home, at the curb and at the compost facility. To the extent that sorting at the curb is possible, sorting at the home will also be improved, leading to more ef- ficient programs.

Nuisance control at the site As noted above, the secondary objective of this project has been to test a particular, low-cost method of composting the collected material. One of the potential risks in selecting this approach is the con- cern that it offers insufficient control or protection against creating environmental nuisances, including problems with vec- tors, odors and groundwater contamination.

Generally, the results of the work to date have been positive. There have been only two formal odor complaints. The first was later dismissed because the smell was emanating not from the compost site, but from an adjacent farm. The second group of complaints occurred when operations at the site were re- \

stricted because of work to improve the pad surface. This led to insufficient turning of the material, and some anaerobic conditions developed.

A study of the surface water runoff and groundwater under the site has been underway since operations began. An interim reporl has been submitted to the local Ministry District Office. In general, this study has so far identified nothing out of the ordinary.

Gulls are the only vector that has been found on the site in significant numbers. Measures have been taken to reduce the number that are attracted to the site, and again, Compost Management has made recommendations to the Ministry for changes designed to end this problem in large part. Chief among these is to con- struct a small, simple building to allow in- itial receipt and debagging of the material to take place indoors. It is expected that incoming material would spend no more than 24 hours inside this building.

Seasonable tonnage fluctuation During the winter, the average daily receipt of waste at the site has been as low as 2.2 tons. During the spring peak this

year, the daily receipt of waste rose tú as high as 16.5 tons. This is an extremely dramatic degree of fluctuation, and im- plies a collection and composting system that is either operating vastly under- capacity in the winter and/or vastly over- capacity in the spring and fall.

Recommendations All of the work that has been done on wetl dry research in Ontario to date shares the common assumption that the entire organic stream (be it within the context of two streams or three) needs to be somehow collected and dealt with as one mass of material. This assumption has been made at least in par-l because of the de- sire to minimize the number of separate streams and therefore the number of collection passes that would be made at a given location.

This assumption, however, has brought with it significant costs. It has meant that the normal degree of waste stream seasonality found in mixed garbage is dramatically magnified in separated organics, since that is where almost all of the seasonality originates. It has also presented significant problems

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aro:!nd the handling of brush and woody wastes, which must be subjected to size reduction, even if the rest of the organics need not.

Does it really make sense to com- mingle all of these materials?: n leaves w brush, Christmas trees w clippings n sod, miscellaneous yard wastes n food wastes n low-grade papers.

If these streams are examined individually, programs can be more effec- tively tailored to best handle each, without incurring excessive costs. From that assumption, we would recommend in the Ontario context: w Further testing of 120-liter roll-out

carts, 60-liter bins and paper yard waste bags - ideally in a user-pay environment. These trials should be com- plemented with the use of the small, cellophane-lined paper food waste bags.

n No further work be undertaken with plastic food waste bags until the indus- try that produces them creates some type of realistic debagging system.

w All forms of brush be removed from the core wet/dry program and instead be picked up by a separate collection once every other month, during a des- ignated week. This is already a reasonably common practice in some municipalities. This change would be made because brush dramatically complicates the handling of mixed organics; brush is stable and can be stored on residents’ properties for weeks at a time, and bringing it in to the compost site on isolated, specific occasions will improve the efficiency of that operation.

w The promotional program include specific advice to residents to time their hedge and brush trimming activities to the period just before the regular bi- monthly collection, and include a calendar as a reminder. All brush would still be hauled to the city demonstration composting facility, for size reduction and incorporation into the windrows. Likewise, a separate collection would take place for Christmas trees.

n Residents be strongly discouraged from collecting their grass clippings at all. Promotional materials should clearly indicate that grass may be left on the lawn, composted in the back- yard or set out for separate collection up to the limit imposed by the collection container provided for all organics.

The city would not collect grass clippings set out with the garbage on these routes.

w Leaves be removed from the wet/dry

At best, participation in the wet/dry composting projects averages about 50 percent.

program and instead be collected separately during the fall season as part of the existing citywide leaf program. The city would employ vacuum and other collection equipment. All

leaves would still be hauled to the city composting facility.

w Low-grade papers not be included in the program until contamination levels with only food and yard wastes can be brought down to acceptable levels.

n Collection staff make an attempt to examine the contents of each roll-out container after dumping it into the hop- per of the truck, as a trial. Any major and obvious contaminants would be removed on the spot and put back into the container. Collection staff would at- tach a specific but friendly violation notice to the cart, to provide feedback to residents. RR

Footnotes

(1) City of Guelph WetiDry Pilot Project: Prelimi- nary Findings, City of Guelph, Ontario, June 1990.

(2) Interim Guidelines for the Production and Use of Aerobic Compost in Ontario, Ontario Ministry of the Environment, November 1991.

(3) Compost Management once dug a single three-cubic-yard bucket full of compost out of a windrow of otherwise finished material that had included diapers, and was able to count approximately 400 diapers in that single sam- ple.

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The First Year with Wet/Dry Composting: A Report from …infohouse.p2ric.org/ref/06/05481.pdftwo wet/dry composting demonstration ... The province and the city have recently agreed