Degradables Tested in Compost Programs

THE BYEBYE PLASTICS DEGRADABLES TESTED IN COMPOST PROGRAMS AST YEAR, the people running manager’s point of view, it has solved the the yard waste composting project pesky debagging problem. However, if the for the Region of Durham (located bags take appreciably longer than it takes to How long does it near Toronto, Ontario) thought compost the yard waste, the manager has they had found the solution to the problems similar to those posed by use of take for degradable messy problem associated with de- regular plastic bags. bags to break bagging leaves. Rather than use The type of problems encountered depend standardL plastic bags for a pilot leaf collec- upon the composting system used. For in- tion and cornposting project, the Region stance, if whole bags are piled in windrows down? How safe made corn starch-based degradable plastic and turned with only a front end loader, the bags available for the collection. composting rate will be retarded if the bags are the residues? “Our supplier told us the bags would de- don’t readily degrade. The yard waste will sit grade in three months,” explained Elaine in the bags without the essential ingredients This report Collis, who heads the composting program. for composting. In fact, many involved in Unfortunately, while the bags had lost some yard waste composting suggest that even describes ongoing of their strength, even in May they were still when degradable bags are used, some means holding up and holding leaves. “We finally of breaking the bags open is appropriate. research projects had to go into the piles and remove the bags Even in programs where the degradable by hand,” remarked Collis. bags are run through a preprocessing shred- to answer these If yard waste is collected in regular plastic der, or a windrow turning machine that rips bags, at some point in the process those bags the bags open, if the residues of the plastic and other key have to be removed. Most of the options for don’t degrade along with the yard waste and removing the bags are expensive and time remains visible, a final screening will be questions, consuming. The promise of degradable plas- needed to produce a marketable product just tic bags, not worrying about removing the like with regular plastic bags. In short, why bags, is almost too good to be true in those spend the extra money for a degradable plas- Jim Glenn situations. But as the problems in the Re- tic if its performance during the composting gion of Durham illustrate, a few questions process does not enhance the operation and need to be answered. the product? Another major question about degradable WHAT QUESTIONS? plastics is what they become when they de While in applications like yard waste com- grade. One manufacturer’s promotional ma- posting there appears to be great potential terial states that, “full degradation leaves for the use of degradable plastic bags, a num- only a fine powder which is absorbed by the ber of questions have also begun to appear. environment.” Little research has been con- First, and most basic, is the issue encoun- ducted into the effect of this fine powder in tered by the Region of Durham. How long the environment. According to Dr. Susan does it take for degradable bags to break Mooney of the U.S. Environmental Protec- down in the compost pile? tion Agency, who heads the EPA’s look at de If a bag degrades at a rate that corre- gradable plastics, “In aquatic environments, sponds with the rate of decomposition of the there may be problems with animals ingest- yard waste, then from a yard waste compost ing the fine plastic particles. On land, the 28 BIOCYCLE OCTOBER 1989 question is what happens when fine plastic applications,” explains Tim Shiveley, ADM’s particles are incorporated into the soil or pos- National Sales Manager. In the spring of sibly inhaled. Are there any environmental 1989, ADM put together a new formulation or health effects?” designed to degrade at a much faster rate in Toxic materials “The size of the plastics fragments result- a composting pile. ing from degradation” is also identified in a According to Dr. George Poppe, who heads should be avoided report of the U.S. General Accounting Of- ADM’s degradable plastic research work, fice, Degradable Plastics: Standards, Re- bags using the new degradable additive when manufacturing search and Development as a safety-related should break down to one millimeter, or less, issue along with the “potential toxicity of size pieces within six months and should be degradable plastic chemicals leaching from degradable plas- unnoticeable in the compost at the end of one tics.” Some in the plastics industry also year. “We souped up the catalysts used to en- bags. There are voice those concerns. Speaking at a 1987. courage the degradation process considera- conference on Degradable Plastics sponsored bly” says Dr. Poppe. alternative coloring by the Society of the Plastics Industry, Re- St. Lawrence started selling a formulation. gina Johnson of Dow Chemical Company Ecostar Plus, for composting last year and agents and inks that noted that “Degradation products of degrad- reports from users are that the bags using it able materials are not well characterized, so perform well in yard waste compost projects can overcome any their toxicity and environmental effects are One user of Ecostar Plus, Petoskey Plastics, unknown." has sampled a number of projects and ac- potential problems. Most people who have examined the toxic- cording to Jim Craig is “seeing the plastic ity issue believe that it’s not the polyethyl- break down to dimesize pieces in six months ene molecules that could cause potential or less.” Ecostar Plus is an adaptation of the problems, but rather additives such as pig- original Ecostar formulation. According to ments used to color the bags, inks used for Peter Campbell, St. Lawrence’s Project En- the printing on the bags and stabilizers that gineer, Ecostar Plus was the culmination of keep the plastic in one piece while the bags research done in Europe that looked at vari- are in use. ous combinations of starch and photosensi- The toxins of concern to most are heavy tive additives. “The final formulation in- metals that include lead, cadmium, nickel cludes 10% starch and an iron salt additive,” and cobalt used in the additives. In 1988, the remarks Campbell. “We believe the plastic city of Lincoln, Nebraska started using bags will be unidentifiable as a plastic within yellow-colored degradable plastic bags in 12 months of being placed in a yard waste their yard waste collection pilot program. composting windrow.” When the city ran tests on the compost this While some programs, like the Region of year, samples showed trace amounts of cad- Durham’s, are experiencing trouble with mium. According to Gene Hanlon, who bags not living up to manufacturer’s claims, heads the project, the source of the cadmium at least one manufacturer believes that the was the yellow bags. “Cadmium was part of fault lies more with the operators of the com- the pigment used to color the bags.” post facilities than the bags. “Many munici- If additives using heavy metals are used, palities simply don’t know the proper way to the concern is that those metals could pose make compost,” maintains Charlie Armis- long term effects on the environment and tead of Manchester Packaging. “They pile health if they either leach into the ground- the yard waste up and only turn it every six water or are taken up by plants and then con- or eight months. Then they wonder why the sumed by humans and/or animals. bags and the yard waste haven’t broken down.” INDUSTRY’S ANSWERS While questions about using degradable PRODUCTS AFTER BREAKDOWN plastic bags in yard waste composting proj- While it appears that in a short period of ects exist, the degradable plastic industry time, the producers of degrading additives Hole after starch granule believes that it has the answers to most, if have been able to cut the time required to biodegraded out of not all, of the questions. Take, for instance, make the plastic in a composting project polyethylene film, after 11 the concern about the rate of degradation. “unidentifiable,” there remains the question weeks in a leaf compost. When degradable plastic bags were first introduced, most companies claimed that the bags would degrade to a size that was indis- tinguishable within three to five years. That length of time certainly isn’t appropriate for composting. However, now the two principal suppliers of the degradable additive - Archer Daniels Midland (ADM) and St. Law- rence Starch Co. - have introduced formulations that offer a much quicker action than the standard formulations. These two companies supply the additive, the active ingre dients of which include starch and oxidizing agents, that is used by the bag manufacturers in producing the degradable bags. “Last year, the standard formulation we used just didn’t perform well in composting BIOCYCLE OCTOBER 1989 29 of into what the plastic degrades. Most of to these low levels at least one researcher, Dr. the manufacturers of the degradable bags Michael Cole, of the University of Illinois and the degrading additives maintain that isn’t sure if all systems can reach molecular the plastic will break down into CO, and wa- weights as low as 500, “The literature on this ter, or those two products and a humic mate subject isn’t conclusive,” notes Dr. Cole. rial. “In an active microbial setting, the plas- Even if the plastic does not completely de tics should break completely down within grade, or if it takes three to five years, or as three to four years,” contends Dr.

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