Cold vs. Hot PET Washing Systems: Overview

PET (polyethylene terephthalate) washing systems are systems for cleaning and recycling PET bottles into flakes that can be reused for new bottles or fibers. The main difference between cold and hot washing systems is the water temperature, which affects cleaning efficiency, energy consumption and the quality of the final product.

cold car washes

Cold washers use water at room temperature or slightly chilled water, typically between 20-30°C. They are energy efficient, lower operating costs and reduce environmental impact. They also cause less material damage to PET. They are good at removing light to moderate contaminants, but have difficulty removing stubborn soiling or residue.

Hot car washes

Hot washers use heated water, usually between 60-80 °C, to dissolve and remove heavy contaminants such as adhesives, oils and bacteria. This makes them ideal for producing high-purity, food-grade PET flakes, but they use more energy and carry the risk of damaging the material at too high temperatures.

When should which method be chosen?

• cold wash: Best suited for general cleaning processes where cost and energy savings are paramount and the recycled PET is not intended for food applications. Ideal for relatively clean bottles with low contamination.

• Hot laundry: Preferred for food grade or high purity applications where thorough cleaning and disinfection are critical. Ideal for heavily soiled bottles or when strict quality standards must be met.

A noteworthy detail is that hot washing may involve additional steps such as the use of detergents and lye solutions, which improve cleaning performance but also make the process more complex.

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Detailed comparison of cold and hot PET washing systems

This analysis compares cold and hot PET washing systems in terms of operating characteristics, advantages and disadvantages, and suitability for different applications. PET washing systems are critical for recycling PET bottles and producing clean flakes for products such as new bottles, fibers, or packaging materials. The choice between cold and hot washing systems depends on factors such as contamination levels, intended use, cost, and environmental impact.

Background to PET washing systems

PET washing plants are systems for cleaning and processing used PET bottles that come from households, companies or recycling centers. The process includes several steps: sorting, shredding, washing, rinsing, drying and final sorting to obtain clean PET flakes. The washing process is crucial, with the water temperature - cold or hot - having a significant impact on the result.

According to a study published in 2024, hot washing usually occurs at 70-75 °C, while cold washing is typically in the range of 20-30 °C, which is due to common industrial practices [1].

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Detailed comparison

To enable a comprehensive comparison, the advantages and disadvantages of the two methods are examined in detail.

Cold PET washing systems

Process description:

Cold washing systems use water at ambient temperature (approx. 20-30 °C) without additional heating. Cleaning is mainly carried out by mechanical measures such as friction washing and water flow.

Advantages:

• energy efficiency: Since there is no need to heat water, energy consumption is significantly reduced, which lowers operating costs and minimizes environmental impact. Particularly beneficial for companies with a focus on sustainability.

• Lower risk of heat damage: PET is temperature sensitive – cold washing prevents deformation or material degradation and preserves the flake quality for further processing.

• Effective for certain contaminants: Cold water is sufficient to remove light to medium soiling such as dust, label residue and some residues.

Disadvantages:

• Less effective against stubborn dirt: Cold water cannot effectively dissolve heavy dirt, adhesives or oily residues, which leads to a lower purity of the flakes.

• Not suitable for food use: For applications that require high purity standards, such as food-grade PET, cold washing may not be sufficient to meet regulatory requirements such as FDA approvals.

Typical applications:

Suitable for non-food applications such as PET flakes for textile fibers, strapping or general packaging. Particularly recommended for companies with budget constraints or high energy price levels.

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Hot PET washing systems

Process description:

Hot washing systems use heated water (approx. 60-80 °C) and often additional cleaning agents or alkaline solutions such as sodium hydroxide to improve the cleaning effect. The treatment often takes place in a heated washing tank in which the flakes are freed of impurities.

Advantages:

• Better removal of heavy contaminants: Hot washing effectively removes stubborn dirt, adhesives and residues and ensures thorough cleaning.

• Meets high purity requirements: Indispensable for the production of food-grade PET flakes for bottle-to-bottle recycling.

• disinfection: High temperatures kill bacteria and pathogens, making recycled PET particularly safe for food packaging.

Disadvantages:

• High energy consumption: Water heating increases operating costs and the CO₂ balance.

• Material damage possible: Long-term exposure to heat can damage PET bottles and flakes, which may affect product quality.

• More complex system: Requires additional heating systems and temperature control, increasing investment and maintenance costs.

Typical applications:

Ideal for food-grade applications where the recycled PET must meet high safety and purity standards (e.g. new beverage bottles). Particularly suitable for heavily soiled bottles from food and beverage containers.

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comparison table

aspect	cold car washes	Hot car washes
water temperature	20-30 °C (room temperature)	60-80 °C (heated)
energy consumption	Small amount	High
cleaning effect	Effective for light to medium soiling	Effective against heavy contamination
material damage	Small amount	Increased risk if temperature is too high
Cost	Lower operating costs	Higher investment and operating costs
degree of purity	Suitable for general applications	Meets food-grade standards
environmental balance	Low carbon footprint	Higher energy consumption and CO₂ emissions
areas of application	Non-food grade products	food contact, high-purity applications

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Conclusion

Cold washers are ideal for energy efficient, cost-effective cleaning processes, while hot washers are essential for high-purity applications with high cleaning requirements. The decision should be based on factors such as contamination level, intended use, cost and environmental impact.