Pyrolytic Conversion of Plastic Waste to Value-Added Products and Fuels: A Review
Bibliographic record
Abstract
Plastic production has been rapidly growing across the world and, at the end of their use, many of the plastic products become waste disposed of in landfills or dispersed, causing serious environmental and health issues. From a sustainability point of view, the conversion of plastic waste to fuels or, better yet, to individual monomers, leads to a much greener waste management compared to landfill disposal. In this paper, we systematically review the potential of pyrolysis as an effective thermochemical conversion method for the valorization of plastic waste. Different pyrolysis types, along with the influence of operating conditions, e.g., catalyst types, temperature, vapor residence time, and plastic waste types, on yields, quality, and applications of the cracking plastic products are discussed. The quality of pyrolysis plastic oil, before and after upgrading, is compared to conventional diesel fuel. Plastic oil yields as high as 95 wt.% can be achieved through slow pyrolysis. Plastic oil has a heating value approximately equivalent to that of diesel fuel, i.e., 45 MJ/kg, no sulfur, a very low water and ash content, and an almost neutral pH, making it a promising alternative to conventional petroleum-based fuels. This oil, as-is or after minor modifications, can be readily used in conventional diesel engines. Fast pyrolysis mainly produces wax rather than oil. However, in the presence of a suitable catalyst, waxy products further crack into oil. Wax is an intermediate feedstock and can be used in fluid catalytic cracking (FCC) units to produce fuel or other valuable petrochemical products. Flash pyrolysis of plastic waste, performed at high temperatures, i.e., near 1000 °C, and with very short vapor residence times, i.e., less than 250 ms, can recover up to 50 wt.% ethylene monomers from polyethylene waste. Alternatively, pyrolytic conversion of plastic waste to olefins can be performed in two stages, with the conversion of plastic waste to plastic oil, followed by thermal cracking of oil to monomers in a second stage. The conversion of plastic waste to carbon nanotubes, representing a higher-value product than fuel, is also discussed in detail. The results indicate that up to 25 wt.% of waste plastic can be converted into carbon nanotubes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.004 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".