I Can’t Believe We Are Continuing to Waste Tons of Plastics When We Could be Recycling and Recovering the Energy Stored in Used Plastics
Posted: October 3, 2012
I guess when you have been around the track as many times as I have, you might have earned the right to express an opinion once in a while. You can see from the title of this article that it stills disturbed me how we as a society are continuing to waste a valuable resource (plastics) while we talk and talk about energy independence.
For over 17 years James W. Garthe (Retired), P.E., Agricultural Engineer and Instructor the Department of Agricultural and Biological Engineering, Dr. Mike Orzolek (Retired) from the Department of Horticulture and myself still on active duty here at Penn State University had a great team dedicated to solving one of the world’s major environmental problems –what to do with the increasing plastics waste generated by the world population. Although our efforts were focused on agricultural plastics we also viewed the large consumer plastic waste stream as a potential fuel source. Our team started working on this project in 1995 and by the end we had positively demonstrated a way to start solving this problem. The concept just couldn’t get traction or maybe we were just ahead of our time. A little background on recycling is in order to better understand the problem.
In the March 18, 2005 issue of the Centre Daily Times was an article “You Ought to Know about Recycling.” In the article the author states “recycling is now an international commodities industry driven by market demand and labor costs.” The author states-“Often programs don’t take materials that aren’t available in large enough numbers to make reusing them profitable.” The plastic code-That little triangle of arrows surrounding a number says what kind of plastic an item is made of, such as code 1, polyethylene terephthalate or PET, used for making soda and water bottles. The best market for recyclables is the 1s and 2s. The demand for these products is insatiable at this point. The bottle caps used on these products are not recycled but removed and enter the trash stream. Think how many bottle caps are used in a day in the United States. Why should we be wasting them- they are a valuable source of fuel.
Although there is strong demand for recycling PET, a soda bottle can only be recycled once, into, for instance, carpet-but the carpet cannot be recycled. In the article they mention garden garbage-when you buy plants for the garden, what does it come in? In a plastic pot or plastic six-pack and if you buy enough, there is also a plastic tray or flat to hold the six- packs. You can reuse the pots yourself, of course, and sometimes garden clubs or conservatories need them for plant sales, but most recycling programs do not accept them.
So what did our team at Penn State to help solve this problem?
I firmly believe that recovering valuable energy from waste plastic items used in agriculture and the consumer marketplace will become a reality at some point down the road. When-I cannot tell you. Dirty, used or non-recycled plastics can be burned and converted to heat or to generate electricity for commercial buildings, light industrial facilities, or other buildings requiring an environmentally clean, yet safe, fuel. Two fuel-saving technologies are currently being brought to commercial reality.
A simple process was invented at Penn State University in 1995 to press waste plastics into a fuel nugget, called Plastofuel. The process, developed by James Garthe in the Department of Agricultural and Biological Engineering, aims to reduce waste plastic buildup on farms around the world. It works by forcing film plastic items, rigid plastic items, or both, through a heated die, thus melting a thin jacket that encapsulates the pieces of plastic and dirt within the extruded material exiting the die. A hot knife cuts the extrudate into dense fuel nuggets that can be easily conveyed, stored and shipped.
The nuggets were originally designed to be co-fired 5-10 percent with coal in existing boilers, allowing the high temperature of coal (around 2000oF or 1100oC) to sustain clean combustion, free of noxious smoke. The end-use is for agricultural boilers or small community boilers designed to burn coal. Plastofuel can be made either on the farm or in small industrial settings or at collection sites in neighborhoods before the plastics get co-mingled thereby consuming the energy close to the source. The benefit of the system is that it converts an annoying waste into a valuable fuel, with a minimum of energy expended in the process. Non-recycled consumer plastic food and beverage containers can also be used in the process. Many of the plastics not currently recycled can be used as a raw material for the Plastofuel. Having worked on this project for many years and seen how valuable the plastics are as a fuel, it kills me to have to throw away any plastic. I continue to stockpile plastics in hope that one day these plastics will be used as a fuel. I want each of you to think about how much non-recyclable plastics you throw away each day. It certainly adds up.
We scaled up the prototype Plastofuel process to a machine that will produce 500 lbs/hr (227 kg/hr) through a grant from the Pennsylvania Department of Agriculture. It was powered by electricity and a hydraulic power unit, all mounted in a trailer to provide mobility. An important point is from an energy perspective, calculations reveal that less than one percent of the heat energy contained in the nugget (when combusted) will be used in the process to form the nugget. We certainly did not want to use more energy in making Plastofuel than it was worth.
Combustion or Burning the Plastics
Everyone always asked about burning plastics and the air emissions. The old saying “Look at the Black Smoke” is certainly true if the plastics are not burned correctly. We spent a considerable amount of money to have stack testing (air emission data) completed that conformed to U.S. Environmental Protection Agency (EPA) standards. This was conducted by an independent U.S. testing company in May 2005 that was funded by a grant from the American Plastics Council. The tests compared LDPE (#4) Korean pellets with granulated HDPE (#2) barrels, which had been discarded by a local firm. Three main groups of pollutants were analyzed:
• Gases (sulfur dioxide, oxides of nitrogen, carbon monoxide, carbon dioxide)
• Particulate matter
Test results proved that plastics could certainly be extremely clean burning in all three groups if the temperature of the burn is high enough.
With the retirement of two of the team members it was decided to ship the Plastofuel machine up to Dr. Matthew Lawrence at Alfred State SUNY College of Technology, Alfred, New York. Matt did his PhD on the Plastofuel machine here at Penn State and seemed the logical choice to continue the work on Plastofuel. Matt can be reached by e-mail at LawrenMJ@alfredstate.edu or by phone at 607-587-4652 if anyone is interested in continuing to support this work and support creating energy and cleaning up the environment as the same time.
Bill Lamont, Penn State Plant Science, firstname.lastname@example.org