Tech 454 Environmental Engineering Department

Tech 454 Environmental Engineeringdepartment Of Engineering And Desi

Write your answers to the following questions in Short Essay Format . Be sure to explain the information as required to support your answers. Cite examples. Number your answers for each question. 1. (15 Points) From the information discussed in class on plastics, select one type of plastic from the seven recycling codes. Do some research and find the process steps that this particular plastic goes through; from the time it is discarded to when it has been completely recycled into a new product. Describe this process in your own words; a minimum of 5 steps will be required to receive full points. (The process of burning the plastic, as a fuel is not an acceptable process answer for this question.) 2. (15 Points) Even though all of the code 1 through code 7 plastics is recyclable, not all plastics are actively being recycled. Do some research and find 3 of the major issues that are currently blocking a more complete recycling process. Describe the issues. 3. (15 Points) Plastics can be burned for fuel at a waste to energy plant, just like paper products. However, the energy return from plastics is not the same as paper products. Do some research and find out which has the higher energy return rate ; the plastics or the paper products? Discuss the pros and cons of burning plastics versus paper products for their energy.

Paper For Above instruction

Environmental engineering focuses heavily on waste management and resource recycling, with plastics being a significant component due to their widespread use and environmental impact. This paper addresses three key questions related to plastics: their recycling process, obstacles to recycling, and energy recovery potential comparing plastics to paper products.

1. Recycling Process of a Selected Plastic: Polyethylene Terephthalate (PET)

Polyethylene Terephthalate (PET), commonly used in beverage bottles and food containers, undergoes a detailed recycling process after disposal. The first step involves collection, where used PET bottles are gathered through curbside programs or recycling centers. During collection, the bottles are sorted from other recyclable materials to prevent contamination. Next, the sorted PET bottles are cleaned thoroughly to remove residues of the contents, labels, adhesives, and other contaminants. This cleaning often involves washing with detergents and sanitizing agents.

The third step is mechanical recycling, where the cleaned PET bottles are shredded into small flakes. These flakes are then washed again to remove residual impurities and dried. In the subsequent melting stage, the flakes are heated and melted. This molten PET is then extruded into pellets or beads, which serve as raw material for manufacturing new products such as fibers for clothing or new bottles. The fifth step encompasses quality control, ensuring that the recycled PET meets the required standards before being used for manufacturing. This process effectively transforms discarded bottles into high-quality raw material, emphasizing sustainability and recycling efficiency.

2. Major Issues Blocking Complete Recycling of Plastics

Despite the recyclability of plastics coded from 1 to 7, several challenges hinder full-scale recycling. The first issue is contamination; plastics often have residues of food, adhesives, or other substances that complicate recycling efforts. Contaminated plastics can degrade the quality of the recycled material or render it unusable. The second issue is the diversity of plastic types within the same recycling code. For instance, plastics labeled with the same code may have different additives or manufacturing processes, leading to incompatibility when recycling together. This diversity complicates the recycling process and limits the number of plastics that can be effectively recycled together.

The third major issue is economic viability. Recycling plastics requires significant energy, labor, and processing costs. Market demand for certain recycled plastics may be low, making recycling economically unfeasible in some cases. As a result, many plastics are not recycled because the costs outweigh potential profits, leading to disposal in landfills or incineration instead of recycling.

3. Energy Return Rate of Plastics Versus Paper Products and Pros & Cons

Research indicates that plastics generally provide a higher energy return rate compared to paper products when used as fuel in waste-to-energy plants. This higher energy content stems from the chemical composition of plastics, which contain long chains of hydrocarbons, making them more energy-dense. In contrast, paper products are primarily composed of cellulose, which has a lower calorific value.

Burning plastics releases more energy per unit volume, offering a more substantial contribution to electricity or heat generation. However, burning plastics also releases toxic substances such as dioxins, furans, and other hazardous compounds, raising environmental and health concerns. Conversely, burning paper primarily produces ash and some pollutants but generally results in fewer toxic emissions, especially when proper pollution control measures are in place.

Advantages of burning plastics include higher energy efficiency and reduction of landfill volume. However, these benefits are offset by environmental risks and the loss of potentially recyclable raw materials. Burning paper, on the other hand, facilitates energy recovery with fewer harmful emissions but contributes less to energy output. In environmental terms, prioritizing recycling plastics over burning them is preferable, aligning with sustainable waste management policies.

Conclusion

In conclusion, plastics such as PET follow complex recycling processes that involve collection, cleaning, shredding, melting, and quality assurance. Despite their recyclability, obstacles like contamination, plastic heterogeneity, and economic factors hinder full recycling. Plastics offer a higher energy return when incinerated compared to paper, but environmental considerations strongly favor recycling over combustion, emphasizing the importance of developing advanced recycling technologies and supportive policies to mitigate environmental impacts while maximizing resource utility.

References

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