Comprehensive Notes: German Yellow Bag/Yellow Bin Recycling and Material Cycles

Overview

• Not every piece of packaging makes a spectacular exit. In Germany, millions of packages end up feeling empty and useless over time, leading to packaging waste.

• Total packaging waste: $2.5\times 10^{6} \text{ tons}$ per year in Germany.

• Waste collected in the yellow bag or yellow bin is sent to sorting plants for separation and potential recycling.

• The core problem: different kinds of plastic are difficult to separate from each other and from other materials, which complicates recycling into new products.

• Most waste ends up being used for energy recovery because of the sorting challenges and material separation issues.

• Energy recovery examples: empty packaging burned for energy in conventional power plants, or used in steel or cement industries.

The Milo sorting initiative and the Southern Hessen plant

• At a sorting plant in Southern Hessen, a company named Milo plans to greatly increase the proportion of reusable waste that can be recycled into new products.

• Source of material: waste collected from yellow bags and yellow bins in the surrounding region.

• Geographic scope: waste gathered from up to a $R = 300\text{ km}$ radius, including the states $\text{Bayern, Baden-Württemberg, Rheinland-Pfalz, Hessen}$.

• Throughput: around $120\ \text{tons}$ of waste gathered each year at this site, equating to about $5\%$ of the waste collected in yellow bags and bins across Germany.

• Sorting setup: sorting is nearly automatic in a large machine hall with a conveyor belt of length $L = 2.5\ \text{km}$.

Sorting process: from size to material identification

• First stage: material falls into a large rotary sieve that sorts by size; smaller pieces fall through the sieve holes.

• Material that doesn’t fall through is transported to two additional drums, resulting in five separate streams of material by size. Rationale: sorting by size simplifies subsequent procedures.

• Special air separator: a blast of wind removes lighter materials (e.g., foil) from the material stream.

• The air separator and other machines remove most of the foil, making the remaining hard plastics easier to sort later.

• Infrared scanning: an infrared scanner quickly identifies types of plastic in the stream.

• Ejection by air: after scanning, air jets eject target items (e.g., PP bottle caps).

• Sorting sequence (by plastic type): PET is separated first, followed by HDPE.

• Post-automated sorting: despite automation, the already-well-sorted streams are hand-picked through to ensure quality; the most useful plastics stay on the belt.

• Residual stream: about one third of the total initial material consists of mixed plastics and residual waste with no use in recycling (e.g., old shoes, wood, etc.). These are directed to energy recovery.

• Overall note: the combination of automatic and manual steps aims to maximize quality and yield of high-value plastics.

Materials, streams, and purity targets

• The targeted plastics in the process include:

  • HDPE (high-density polyethylene)

  • PET (polyethylene terephthalate)

  • PP (polypropylene)

• At the Ganzheim plant, the sorted plastics are pressed into bales. Purity levels achieved for the main streams are high:

  • HDPE bales: $94\%!-98\%$ purity

  • PP bales: $94\%!-98\%$ purity

  • PET bales: $94\%!-98\%$ purity

• These high-purity secondary raw materials are valuable to the plastics processing industry and are used in various applications.

• Examples of downstream uses:

  • HDPE bottles used to make pipes or specialized pallets

  • PP plugs often turned into flower pots or buckets

  • PET packaging used to create fibers for fleece sweaters or lawn furniture

• Plant scale: the Ganzheim plant handles a substantial share of the sorted plastics and produces bales that are sold to manufacturers in Germany and neighboring countries.

Energy recovery and residuals

• Despite strong sorting, a substantial portion of the initial material remains unsuitable for recycling and is directed to energy recovery.

• This reflects the current reality that not all collected yellow bag/bin packaging can be turned back into new products without additional processing or material separation steps.

Cystech Plastics at Eisfeld (HDPE reprocessing and color sorting)

• Location: Eisfeld, Thuringia.

• Process flow for HDPE bottles:

  • HDPE bottles are shredded and then cleaned of residues (e.g., shampoo, yogurt).

  • A color-sorting step follows to remove last unwanted residues and to produce a clean HDPE flake stream.

  • Color sorting details:

  • The system uses LEDs to illuminate the stream and sensors to recognize color.

  • A computer controls a panel with more than $60\ \text{compressed air nozzles}$ to blow away unwanted colors.

  • The material passes over slides; the process is repeated multiple times (two slides, next two slides, final repetition on the last one).

  • Output of color sorting: roughly $800\ \text{kg/h}$ of sorted HDPE flakes with purity well above $99\%$.

  • The HDPE is melted at $T = 220^{\circ}\text{C}$ in an extruder, then filtered and purified; the melt is cooled and processed into granules.

  • Result: a high-quality HDPE raw material usable in numerous plastic products.

• Production statistics:

  • Each year, around $2.0\times 10^{4}\ \text{t}$ (i.e., $2.0\times 10^{4}\ \text{t/year}$) of material from the yellow bag is processed at Eisfeld.

  • Only a portion of this material currently receives the full treatment pipeline; capacity is planned to increase in the future.

• Outlook and ambitions:

  • Eisfeld aims to enter areas related to the food industry (hygienic requirements) starting with cosmetics, then food, albeit over several years.

  • Recycled material from Eisfeld is already sought after by makers of washing and cleaning products.

Mainz location: Wana and Matz production of detergents and bottles

• Location: Mainz (Rhine region).

• Business scope: Wana and Matz produce more than $1.3\times 10^{5}\ \text{t/year}$ of detergents; packaging is processed to complete the material cycle.

• Process using recycled material from yellow bag:

  • The HDPE granulate from Eisfeld is fed into a machine to form bottles under extrusion; excess material is trimmed; bottles are filled and delivered to shops.

  • Output: more than $5.5\times 10^{6}\ \text{bottles/year}$ produced using recycled plastic from the yellow bag.

  • PP caps are produced using 100% recycled material from the yellow bag.

• Integration with recycled materials:

  • Mainz uses HDPE from Eisfeld and PET from yellow bag mixed with PET from the deposit system in preforms to blow bottles.

  • The current program produces bottles with composition: $20\%\text{ PET from yellow bag} + 80\%\text{ PET from deposit system}$ (i.e., a blend in preforms).

  • In total, Mainz produces more than $8.0\times 10^{7}\ \text{bottles/year}$ using this mixed recycled content.

  • The aim is to gradually increase the share of PET from the yellow bag in all packaging and to use more of this high-quality recycled plastic.

• Rationale and statements:

  • The approach preserves raw materials and energy invested in plastic production by reusing recycled content in packaging.

  • Historically, only a small fraction of yellow bag/bin packaging was recycled, but experience shows there is potential for material cycles using yellow bag plastics.

• Market and collaboration notes:

  • The project is actively seeking market partners to reduce the cost of recycled materials.

  • The more packaging producers use yellow bag recycled material, the greater the production capacity and the economic viability of using recycled content will be.

PET granulate and regional differences

• PET bottles are a major packaging type at facilities in Vienna and Metz, where PET makes up a large share of packaging.

• Despite sorting using advanced high-tech machinery, there is a shortage of PET granulate from the yellow bag, so PET granulate from the yellow bag is mixed with PET granulate from the deposit system (empty beverage bottles).

• In Mainz preforms, the production mix is 20% PET from the yellow bag and 80% PET from the deposit system, before blowing into bottles and filling.

• Annual output at Mainz for this mixed approach: >$8.0\times 10^{7}\ \text{bottles/year}$.

• The goal is to gradually increase the share of yellow bag material in PET bottles and expand the use of high-quality recycled plastic across packaging.

Philosophical, ethical, and practical implications

• Ethical/practical goal: closing the loop on plastic packaging by increasing the proportion of recycled plastic in new products, thereby reducing raw material use and energy intensity in plastic production.

• Environmental impact: while sorting and recycling are energy-intensive, recycling plastics can reduce oil consumption and emissions compared to producing new plastics, but the energy and resource costs of multiple sorting and purification steps must be weighed.

• Material science challenge: achieving food-grade or cosmetic-grade recycled plastics remains difficult; Eisfeld’s ambitions to enter cosmetics and food sectors hinge on achieving hygienic standards and high purity.

• Economic considerations: the volume of yellow bag material needs to be sufficient and consistently available; building demand from manufacturers (like Wana & Matz) is essential to drive scale, reduce costs, and improve overall recycling economics.

• Dependency on deposit systems and feedstock mix: PET from yellow bag exists but is not yet sufficient in quantity for large-scale food-grade applications; blending with deposit-system material is a transitional approach.

• Social and consumer behavior: the success of such programs depends on proper segregation by households (yellow bag/bin) and participation in recycling schemes.

Key figures and formulas (recap in LaTeX)

• Total packaging waste in Germany: $2.5\times 10^{6} \text{ tons}$ per year.

• Radius of collection: $R = 300\ \text{km}$.

• Annual waste gathered at Milo plant: $120\ \text{t}$, representing $5\%$ of yellow bag/bin waste nationwide.

• Sorting belt length: $L = 2.5\ \text{km}$.

• Five streams produced by sorting by size.

• Light-material removal: PP caps ejected by air after IR scanning.

• IR-based separation producing sequential PET → HDPE streams.

• Post-sort manual refinement: fraction of initial material that is mixed plastics and residual waste: $\approx \frac{1}{3}$ of total.

• Purity of bale streams: $94\% \text{ to } 98\%$ for HDPE, PP, PET.

• Throughput at Eisfeld color sorter: $800\ \text{kg/h}$ of HDPE flakes with purity > $99\%$.

• HDPE melt temperature: $T = 220^{\circ}\text{C}$.

• Annual throughput at Eisfeld: $2.0\times 10^{4}\ \text{t/year}$ (HDPE from yellow bag).

• Bottles produced at Mainz with recycled content: $5.5\times 10^{6}\ \text{bottles/year}$.

• Bottles from Mainz using mixed PET content: $20\%$ from yellow bag, $80\%$ from deposit system.

• Mainz PET bottle production: >$8.0\times 10^{7}\ \text{bottles/year}$.

• Bottle-to-bottle potential: the overarching aim is to enable transforms from one bottle to another via enhanced material processing and sorting to close the loop.

Connections to foundational principles and real-world relevance

• Circular economy concept: the material cycle for plastics is pursued by turning yellow bag plastics back into new bottles, pipes, fibers, etc.

• Recycling technology progress: advanced sorting (rotary sieves, air separators, infrared scanners, color sorters with LEDs and compressed-air jets) demonstrates how technological improvements enable higher purity recyclates.

• Residual waste challenge: a substantial fraction of collected packaging remains unrecyclable with current processes, underlining the need for design for recycling and better material separation at source.

• Food-grade and cosmetics-grade plastics: reaching these sectors requires stringent hygienic standards and purity, illustrating the gap between current recycling capabilities and market requirements.

• Partnerships and economics: market collaboration between packaging producers, recycled-material suppliers, and brand owners is essential to scale recycling and reduce material costs.

Summary takeaways

• Germany generates large packaging waste; sorting and recycling are technically feasible but complex due to material diversity.

• Modern sorting facilities can achieve high-purity bales of HDPE, PET, and PP, enabling secondary material markets and applications beyond basic uses.

• Residual waste and energy recovery remain part of the system, highlighting the imperfect nature of current loops.

• Eisfeld’s color sorting and downstream processing demonstrate how high-purity recyclates can be produced, with potential for food-grade use in the future.

• Mainz demonstrates the practical integration of recycled content into real packaging products (bottles and caps), with clear aims to expand the yellow bag’s share and create more sustainable material cycles.

• The overarching message: turning a bottle back into a bottle is the ultimate goal of a true material cycle, and while progress is underway, it requires continued investment, innovation, and collaboration.

Notable closing thought

• "That means an HDPE bottle is made from another HDPE bottle. And no matter how unspectacular the shot, at least it's one bottle more."