What to do with the Remnants of a Plastic Culture
Plastics permeate every facet of modern industrial life, so what can be done with that material after it has served its useful purpose? Alternative energy sources are increasing in popularity but one such potential alternative-plastic-is contentious.
The invention of these useful polymers derived largely from crude oil has been of great use to society but concerns over environmental damages exacted by the proliferation of industrial plastics' production and disposal are not without their merits. Plastics such as PVC have a high chlorine content that, when burned, produce dangerous dioxins. The U.S. EPA states, "Dioxins and ‘dioxin like' compounds are a group of 30 highly toxic chlorinated organic chemicals. They are produced naturally in small quantities but are primarily the result of human activity. They can be produced through industrial processes such as chlorinated chemical manufacturing and metal smelting. Currently, however, the largest quantified source of dioxin emissions is the uncontrolled burning of household trash (backyard burning). Studies have shown that only small amounts of chlorinated materials in waste are required to support dioxin formation when burning waste."
Penn State University researcher James Garthe says, "We are our own worst enemy." For the past 15 years, Garthe's professional emphasis at PSU has been on solid waste management and recycling, mostly in the agricultural sector. The term "plasticulture" refers to the use of plastics in agriculture. "It started after World War II, when plastics were coming into mainstream life," he says. "Someone in their wisdom said this stuff (plastic mulch film, etc.) is good in holding back water or retaining water if it's laid on the ground and crops are grown on it-there's no water evaporation and it's good for weed suppression. So after World War II, it saved the farmers, growers and greenhouse operators all sorts of money in their operations."
Barriers to Recycling Plastics
A resin identification code, one through six, is given to all plastics. Varieties that can be recycled must be mixed only with like material. "So many different resin types cannot-will not-mix," Garthe says. "That's a problem because you can have a nursery pot made from No. 2 (high density poly ethylene) right next to a No. 5, and they look the same but they are different resins. That causes confusion and the recyclers are saying, ‘Hey, I'm not going to turn over every container to look at what number's on the bottom.' And then the other problem is you've got similar items coming in from Asia or elsewhere, and they may not have the chasing arrows on it so you just don't know."
Not only must like resins be recycled together, but the dye used to color the plastic throws another variable into the mix. Everything goes into black, but if white plastic is desired then black plastics cannot be mixed in-even if they are the right resin number. "So there needs to be a separation system not only for resin type but for color," Garthe tells Biomass Magazine. "People say, ‘I'm holding a penny's worth of plastic and now they're telling me I have to color sort as well?' It gets complicated." Other barriers to recycling plastic exist.
One big barrier to recycling is its need to be clean. "The word ‘extrusion' is a very critical word to the plastic guys," Garthe says, adding that one spec of dirt can plug injectors used in injection molding. Dirt is a huge problem in recycling materials used in plasticulture. When mulch film has served its useful purpose, it is laden with chunks of clay, soil and more. "Sometimes when you pull it up what you have is 100 percent dirt," Garthe says. The material is only one-thousandth of an inch thick. Cleaning the material to make it suitable for recycling is cost prohibitive. "It's easier and cheaper to go with virgin plastic, and that makes the petroleum and natural gas companies happy because we're buying new product."
Then there is inadequate infrastructure for collection of plastics in many places. Given all of these obstacles to recycling plastics, people simply throw perfectly recyclable material away where it occupies valuable landfill space and may release toxins once it begins to break down long after disposal. While no one seems to know precisely how much plastic is produced and consumed every year, some experts suggest that, whatever that number is, only a small fraction of it actually is recycled. For plasticulture material, Garthe says only about 1 percent of mulch, greenhouse and forage film; nursery pots, trays, flats, etc., is actually recycled.
Burning Plastic for Energy
Madison Gas & Electric owns a 200 megawatt power plant in downtown Madison, Wis., called the Blount generating facility. The plant has been burning what the utility dubs "PDF" (poly-derived fuel) for more than 10 years. It describes PDF as a mix of "shredded preconsumer waste [that] cannot otherwise be recycled." Blount was one of the first electric generating stations in the country to burn "alternate fuels such as wastepaper and plastic … [and] in 1997, MGE added 7,200 square feet of storage for paper and PDF (paper-derived fuel) to increase use of the fuel," MGE states. The utility says it has undergone all of the approval processes necessary to burn PDF, but Jim Powell, a board member with Madison Environmental Justice Organization-whose mission it is to protect minorities and the poor from inordinate exposure to environmental hazards of industrial modern life-says when the utility was first going through permit process for these alternative fuel sources, the potential for dioxin emissions was discussed only briefly. "The regulators requested MGE to come back with more information about dioxin emissions," Powell says, adding the state never required any further investigations before allowing the burning of plastics. Now, 11 percent of the Blount generating facility's power comes from PDF the remainder is coal, according to Powell. "There are a whole slew of chemicals to be concerned about-the biggest is dioxin, which is a byproduct from burning chlorine based plastics," he tells Biomass Magazine. Powell says some of the material comes from a nearby Oscar Meyer plant and other industrial facilities, and is virtually free. It also has a high British thermal unit content.
At PSU, Garthe has been working to develop positive, creative uses for the abundance of waste plastics produced by our convenience-oriented society. "I kept hearing from folks that we've got all this plastic out there and that it saves money, but what do we do after it's completed its useful purpose?" Garthe says. "In 1994, I came up with the Plastofuel concept." Simply put, his concept was to push waste plastics through a heated die, melting the outer layer and producing plastic nuggets for cofiring. Garthe says on a pound-for-pound basis plastics contain more energy than gasoline. In times past, this waste agricultural plastic was burned openly in the field producing huge plumes of billowing black smoke. "That's why I got involved," he says. "I kept hearing how it's a problem for us to manage, especially if it's thrown in a pile or down a sinkhole and later on down the pike it's affecting someone's well water supply."
Garthe distinguishes between the toxicity of burning plastic in a burning barrel versus high-temperature and oxygen-enriched combustion at a power plant, reaching 2,000 degrees Fahrenheit. "The higher the temperature of combustion, the less the products of incomplete combustion," he says. The opposite is also true: The lower the temperature, the higher the products of incomplete combustion. While Garthe doesn't have all of the answers with respect to the dangers of heavy metals and dioxins from combusting plastic, he says, "I'd be less concerned about [industrial incineration of plastic] because of the watchful eyes of the regulators out there looking after public health. Much more concerning is Joe Schmo who's out there burning this stuff in a burning barrel."
After weighing a variety of environmental impacts like global warming, acidification, eutrophication, human toxicity and ecological toxicity, Jeffrey Morris, author of "Comparative LCAs for Curbside Recycling Versus Either Landfilling or Incineration with Energy Recovery," concludes that the recycling of plastic bottles-one of many types of plastics but a prolific example nonetheless-from household and municipal solid waste streams "consumes less energy and imposes lower environmental burdens than disposal … via landfilling or incineration," even after accounting for energy production from incineration. "I must stress that John Q. Public has to change his attitude about solid waste management," Garthe says. "No longer can we say, ‘Out of sight, out of mind, and I'm going to take this bag of junk and set it out on the curb and say I don't have to deal with it anymore. He is going to have to have some accountability for that because it's a resource. It has a raw material value and should not be hauled off to the landfill to deal with for the next 10,000 years."
While U.S. consumers often bear the onus of recycling all the plastic we consume, where is industry's accountability for selling it in the first place?
Ron Kotrba is a Biomass Magazine senior writer. Reach him at email@example.com or (701) 738-4962.