Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Efficient plastic nuggets key to agricultural plastic waste disposal

01.07.2002


A process that would be a plastics recycler’s nightmare may help farmers deal with the disposal of agricultural and domestic plastics by creating burnable, energy-efficient plastic nuggets, according to a Penn State agricultural engineer.



"In plastics recycling there are two unbreakable rules," says James W. Garthe, instructor in agricultural engineering and cooperative extension specialist. "You cannot mix types of plastic, and the plastics must be clean. This process does both since mixed plastics burn just fine and the dirt and debris come out with the coal ash anyway."

Agricultural plastics, such as mulch films, greenhouse films and pots, flats and silage wraps are universally dirty, and the cost of cleaning them before recycling would be expensive. Also, while mulch and greenhouse films are generally low-density polyethylene, nursery pots are polypropylene and soda bottles and milk jugs are polyethylene terephthalate and high-density polyethylene respectively. The plastics found on farms, nurseries and landscape yards are a variety of plastics that would never be mixed in conventional recycling.


Garthe’s unconventional approach is to convert the various film and solid plastics into a plastic nugget that can be burned with coal in coal fired boilers, refuse-derived fuel burners and even cement kilns. The process can mix plastic types, because it does not melt the plastic. Only the outer portion of the nugget is fused forming a melted jacket that contains the compressed plastic waste.

"Because the plastic is not completely melted, calculations show that only about one eighty-fifth of the energy released when the plastic nuggets burn is used to create the nugget," says Garthe. "Even if these plastics could be remelted and remolded, which they cannot, conventional recycling requires much higher energy input."

Including the energy required to preprocess the plastic and to cut the pieces in the calculations; the nuggets still supply 20 times the energy used to make them, according to Garthe.

Preprocessing for the prototype plant is currently done by cutting up the plastics and hand feeding them into the hopper where a feed rod pushes them into the die. The die is heated to melt the outer layer and a snake of compacted, but mostly unmelted plastic emerges. For the prototype, Garthe cuts the snakes into nuggets with a hot knife. Conveyers, a way to produce the proper-size plastic pieces, and automatic cutting of the nuggets will eventually be incorporated into the system.

"The system can be made small enough to be bench scale, but could also be enlarged to industrial scale," says the Penn State researcher.

While dirty and mixed plastics can be used, wet plastics might pose a problem for the system so some type of quality control would be necessary. Also, sandy plastics might cause a problem because the silicate sands might fuse onto the grates.

"We probably will not use polyvinyl chlorides, like PVC pipe or collapsible irrigation tube in the process because of the potential for emissions problems," says Garthe.

Burning the nuggets along with coal probably produces few emissions as the temperatures of 1,500 to 2,000 degrees Fahrenheit allow for more complete combustion. Plastics simply burned in a burn barrel reach only 400 to 700 degrees Fahrenheit and this incomplete combustion can produce unwanted emissions. Although Garthe believes that emissions are not a problem for the nuggets, Penn State’s Energy Institute is currently running tests on the nuggets to characterize the emissions. A grant from the National Watermelon Promotion Board, U.S. Department of Agriculture, supports these tests.

Currently, besides the small amount of plastic bottles and jugs that are recycled, most other plastic wastes end up being land-filled, where the energy potential of the plastic as a fuel is wasted. Nurserymen, landscapers, truck farmers, mushroom growers, hothouse owners and even dairy farmers produce varying amounts of plastic waste.

"Depending on the type of agricultural operation, the generation of plastic waste probably ranges from 10 pounds to 10,000 pounds a year," says Garthe.

The Penn State agricultural engineer has applied for a provisional patent on this process.

Andrea Elyse Messer | EurekAlert!

More articles from Agricultural and Forestry Science:

nachricht Plasma-zapping process could yield trans fat-free soybean oil product
02.12.2016 | Purdue University

nachricht New findings about the deformed wing virus, a major factor in honey bee colony mortality
11.11.2016 | Veterinärmedizinische Universität Wien

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>