Dealing with plastic waste
Given the continuing problem of waste in our country and in Cebu, today’s discussion about recycling plastic wastes may help.
BBC presented a documentary about plastic wastes being recycled and used for roads. If you search the website for more information, you will realize that many have known that roads can be made from plastic wastes.
This website (http://tce.edu/chemistry/process.html), for example, with illustrations, provides clear details about how plastic wastes can be used for roads.
According to the website, these are the following plastic wastes that can be used: “1) Films (Carry Bags, Cups), thickness up to 60 micron (PE, PP and PS); 2) Hard foams (PS) any thickness; 3) Soft Foams (PE and PP), any thickness; and 4) Laminated Plastics, thickness up to 60 micron (Aluminum coated also) packing materials used for biscuits, chocolates, etc. Polyvinyl chloride (PVC) sheets or flux sheets should not be used in any case.”
The website presents four steps as follows: “For Process Step 1, the plastics wastes (bags, cups, thermocole) made out of PE, PP and PS are cut into a size between 2.36mm and 4.75mm using shredding machine (PVC waste should be eliminated).
“In Process Step 2a, the aggregate mix is heated to 165°c (as per the HRS specification) and transferred to a mixing chamber. Process Step 2b states that the bitumen is to be heated up to a maximum of 160°c (HRS Specification) to have good binding and to prevent weak bonding. (Monitoring the temperature is very important).
“For Process Step 3, at the mixing chamber, the shredded plastics waste is to be added. It gets coated uniformly over the aggregate within 30 to 60 seconds, giving an oily look. Finally, for Process Step 4, the plastics waste coated aggregate is mixed with got bitumen and the resulted mix is used for road construction. The road laying temperature is between 110°c to 120°c. The roller used is 8-ton capacity.”
According to this website, the process of converting plastic wastes for road construction is an “easy process without any new machinery. It is a simple process without any industry involvement. It is also an in situ process. There is lesser use of bitumen and thus savings on bitumen resource, and the use of plastics waste is a safe and eco-friendly process.”
Additional information from this website includes: “Both Mini Hot Mix Pland and Central Mixing Plant can be used. Only aggregate is polymer coated and bitumen is not modified. Use of 60/70 and 80/90 bitumen is possible. There is no evolution of any toxic gases like dioxin and fly ash can also be used to give a better performance.”
As discussed by a 2014 write-up found in the following website (see
(http://earthuntouched.com/plastic-roads-revolutionary-idea/), “disposal of waste plastic is a major problem. Plastics are also non-biodegradable and burning of these waste plastic bags causes environmental pollution. Discarded thin-plastic carry-bags are a menace, clog drains, cause flooding, choke animals that eat them, and are unsightly. Strewn across fields, they block germination and prevent rainwater absorption by soil. Recycling plastic by melting releases fumes, and is only possible 3-4 times. Toxic contents might leach into recycled water pots or water-pipes.”
Some advantages of using plastic in making roads presented in this website include: “stronger road with increased marshall stability value, better resistance towards rainwater and water stagnation, no stripping and no potholes, increased binding and better bonding of the mix, reduction in pores in aggregate and hence less rutting and raveling, no effect of radiation likes UV, the strength of the road is increased by 100%, the load is withstanding property increases, and it helps to satisfy today’s need for increased road transport. For 1km X 3.75m road, 1 ton of plastic (10 lakh carry bags) is used, and 1 ton of bitumen is saved. Value addition to the waste plastics (cost per kilogram increased from Rs4 to Rs12).
The cost of road construction is also decreased. The maintenance cost of the road is almost nil. Disposal of waste plastic will no longer be a problem. The use of waste plastics on the road has helped to provide the better place for burying the plastic waste without causing disposal problem. Employment for unskilled laborers will be generated.”
The following disadvantages, however, have also been cited and urgently need to be addressed: “During the cleaning process: Toxics present in the co-mingled plastic waste would start leaching. During the road laying process: The presence of chlorine will release noxious HCL gas. After the road laying: It is opined that the first rain will trigger leaching. As the plastics will merely form a sticky layer, (mechanical abrasion), and, the components of the road, once it has been laid, are not inert.”
With the garbage piling up in our midst, especially plastics, more research and practice are needed to recycle and manage trash and convert it to treasure, with ecologically useful and productive results.
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