Resources, Conservation and Recycling
Received 12 June 2018, Available online 15 January 2019
Giorgia Faraca
Technical University of Denmark, Department of Environmental Engineering, Miljøvej, 2800, Kgs. Lyngby, Denmark

Table of Contents

1. Introduction

  • An environmental and financial assessment was conducted on one tonne of hard plastic waste collected at Danish recycling centres.
  • The European demand for plastic in 2016 was 57 million tonnes (EC, 2018), of which 70% was made of six main polymers: polyethylene terephthalate (PET), high- and low-density polyethylene (HDPE and LDPE), polyvinyl chloride (PVC), polypropylene (PP) and polystyrene (PS).
  • In Denmark, around 20% of post-consumer plastic waste is recycled, while the rest is incinerated (less than 5% is landfilled; Plastic Europe, 2016).
  • Only hard plastic waste (rigid products such as bottles and containers, pots, pipes, crates, toys, etc.; see definition in Appendix B) is generally recycled in Denmark.
  • Recycling processes for plastic waste have been classified by the scientific literature and legislation standards as a) primary (re-extrusion), b) secondary (mechanical recycling), c) tertiary (feedstock or chemical recycling) and d) quaternary (energy recovery) routes, according to the technology used and the output produced by the process (e.g. ASTM Standard D5033, 2000; Brems et al., 2012; Ignatyev et al., 2014).1
  • The presence of impurities in plastic waste makes recycling difficult differentiating with glass and metals.
  • The purity of plastic waste is the primary factor determining the quality and economic value of recyclables.
  • Impurities in plastic waste may be grouped into three classes: non-plastic components (foreign materials), non-targeted plastic (different polymers than the one targeted for reprocessing, including multi-plastic products and polymer blends) and chemical impurities (bound to the plastic matrix, such as pigments, additives, stabilizers, etc).
  • The selection of the plastic waste recycling route usually depends upon factors such as location, polymer type, product type, method of collection, presence of impurities, desired quality of the product and raw material prices offered by companies sorting or recycling the waste (Ragaert et al., 2017; Valentino et al., 2016; Yu et al., 2016).

The export of recyclables is common in Europe, as the plastic recycling industry is characterised by a large number of entities, each performing a certain role in the recycling chain, linked by market agreements which are very volatile and depend on “who-offers-more” as well as the price of virgin materials (Villanueva and Eder, 2014). The main European importers of plastic waste are Germany, the Netherlands, and Italy (EC, 2018). Although an international market for recyclables may promote more recycling, international exchange of recyclable materials may also reduce transparency and traceability of waste materials, thereby making more difficult the accounting of environmental impacts and total management costs.

  • However, as the net environmental benefits provided by recycling processes cannot stand alone as a basis for decision-making, an evaluation of financial considerations is also required.

2. Materials and methods

  • In an eLCC a financial analysis is complemented by an LCA for the same system. Therefore goal, scope, functional unit (FU) and system boundaries of the LCA and LCC must be identical (Hunkeler et al., 2008).

Appendices

The link

C. Review of recycling configurations in literature

Table C.1. Configuration of recycling processes investigated in literature. ECS: eddy-current separation2; ELV: end-of-life vehicles; FR: feedstock recycling; HH: household; MR: mechanical recycling; MRF: material recovery facility; NIR: near infra-red scanner; PMD: plastic, metals and drink packages; WEEE: waste electrical and electronic equipment.
Mechanical recycling:

  • NIR (near infra-red scanner)
  • Ballistic sieve 3
  • Wind sifter 4
  • Magnets
  • Eddy-current separation2
  • Grinding, granulation
  • Shredding, cleaning
  • Extruding
    Tertiary recycling (also termed chemical or feedstock recycling5):
  • Hydrolysis, pyrolysis, hydrocracking and gasification

D. Probability distributions of parameters used in the modelling

D.1 Operational data

  • NIR sorting efficiency for various polymers
  • Manual sorting efficiency for various polymers
  • Technical substitution factor (yield)

Table D.2 Detailed inventory of simple mechanical recycling (sMR) scenario

Transfer to material recovery facility (MRF)
Input: plastic waste (1000kg), diesel (2.57kg)
Output: Plastic waste (1000kg)
Material recovery facility (MRF) phase
Input: plastic waste (1000kg), electricity (32kWh), Waste preparation facility
construction (Process from ecoinvent v3.5, RoW)
Output: PP plastic waste to recycling (340kg), PE plastic waste to recycling(150kg),
Mixed plastic to incineration (510kg)
Transfer to recycling facility
Input: Plastic waste (490kg), diesel(0.63kg)
Output: Plastic waste (490kg)
Recycling of PP plastic waste
Input: PP plastic waste (340 Kg), Electricity (284kWh), Water (3706 Kg), Sodium hydroxide (0.079kg), Heat (80MJ), plastic processing factory construction (process from ecoinvent v3.5, RER)
Output: Recycled PP granules Kg 235, Residues to incineration kg 105
Recycling of PE plastic waste
Input: PE plastic waste Kg 150, Electricity kWh 109, Water kg 1635, Sodium hydroxide kg 0.035, Heat MJ 35, Plastic processing factory construction (process from ecoinvent v3.5, RER)
Output: Recycled PE granules Kg 114, Residues to incineration kg 36

Whether labour cost and land cost (possibly included in construction cost) is missing here? 19/03/2022 16:52

  1. Primary recycling, often referred to as “closed loop recycling”, is when recyclable materials are mechanically processed to create a product that serves a similar function. Secondary recycling is still a mechanical recycling process, but it uses recycled materials to make a new product. This new product typically does not have the same physical demands as the original product and is often less recyclable. The tertiary recycling is using recyclabeles as a feedstock in a process to create chemicals and fuels. These chemicals can then be used to create new materials. ↩︎

  2. Eddy current separation takes the principles of electromagnetic induction in conducting materials, to separate non-ferrous metals by their different electric conductivities. ↩︎ ↩︎

  3. The ballistic separator separates the material based on the climbing ability and the irregular ballistic behaviour of the components. ↩︎

  4. A method of separating waste based on the density of material using the principles of controlled air. The input material is separated into two fractions varying from light to heavy. ↩︎

  5. It indicates processes based on breaking down the polymer chains to smaller molecules. Some technologies (like hydrolysis, pyrolysis, hydrocracking and gasification) produce liquids and gasses that can be used in the production of new plastics, synthetic fibres, lubricants and fuels or other products used by the chemical industries. Other processes (e.g. glycolysis, methanolysis etc.) depolymerise plastic waste into its smallest components (the monomers) that are then repolymerised into new products. This last class of processes is less often performed because some polymers (like PP and PE) cannot be easily depolymerized. ↩︎