Plastic pipe production of the future: Using recyclates for greater sustainability

Return system for sewer pipes

On 18 June, the Federal Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection (BMUV) published its draft „Nationalen Kreislaufwirtschaftsstrategie“ (NKWS), setting out guidelines and criteria for a sustainable circular economy. In the run-up to this, representatives from industry, trade unions, associations, science and administration had the opportunity to help shape this as stakeholders with their own ideas and suggestions in a joint dialogue process with the federal government. Representatives of the plastic pipe industry, which has long been committed to making the value chain more sustainable, were also involved.

In a multi-stage recycling process, the recyclable materials are processed into regrind, which is used in the production of new plastic pipes

1. „National Circular Economy Strategy“: Principles and objectives

General principles and objectives
The German government's „Nationale Kreislaufwirtschaftsstrategie“ is based on the guidelines of the „Deutschen Nachhaltigkeitsstrategie“ and internationally on the „UN 2030 Agenda for Sustainable Development“ from 2015, which pursue a transformation to a more sustainable economy. At EU level, the NKWS thus follows the „Action Plan for the Circular Economy“ and its guiding principle. The aim is to achieve a circular economy whose central objective is to reduce the consumption of primary raw materials through the economical use of resources and thus close material cycles as far as possible.

Taking into account the above-mentioned political framework conditions, a „Roadmap: Targets - Indicators – Measures“ was developed together with stakeholders. This includes the development of „target-orientated measures“ for „central material flows“ (such as plastics, metals, etc.) or the „sustainable design“ of products made from secondary raw materials.

The NKWS identifies industry and SMEs as the main players in the circular economy and sees them as „drivers of innovation“ with regard to a green German lead market for the circular economy.

With the publication of the draft on 18 June, stakeholders will subsequently be given the opportunity to submit written comments by 9 July, with feedback on the quantitative targets of individual material flows as well as specific measures and instruments (especially recyclate quotas or economic incentive instruments) being of particular interest to the BMUV.

Material cycle in the plastic pipe industry from the raw material manufacturer to the end user

Facts and figures: recyclate quotas for plastic pipe production in Germany
For the CONVERSIO study „Stoffstrombild Kunststoffrohre in Deutschland 2021“ commissioned by the Kunststoffrohrverband e.V. (KRV), recycling quotas were determined for the following areas, among others, for the year analysed:

Total plastic pipe processing volume and raw materials used
A total of 973,000 tonnes of plastic pipes were produced. During processing, 853,000 tonnes (around 87.8 %) of plastics from virgin material, around 57,000 tonnes of post-consumer recyclates (i.e. materials recycled from products already in use) and around 15,000 tonnes of pre-consumer recyclates (materials that are disposed of during the production process) as well as around 48,000 tonnes of recycled by-products were used. The interim conclusion of the study at this point is: „Compared to the post-consumer recyclate use rate of plastics in the construction sector as a whole (~15 %), the rate for plastic pipes is at a lower level at ~5.9 %.“

Quantity of recyclates from post-consumer pipes used in neuro-pipes
A total of around 27,000 tonnes of post-consumer recyclates were used in various plastic applications in Germany in 2021. Of this, 89 % flowed back into the production of various construction applications (plastic pipes, cable covers, etc.). 20,000 tonnes - and therefore the largest proportion of recyclates from raw waste - were again used in the production of plastic pipes.

Here, too, the study draws an interim balance:
„It can therefore be stated that around 74 % of plastic pipe recyclates were already used in new plastic pipes in 2021. A 'closed loop' of plastic pipes is therefore perfectly feasible. The challenge lies in scaling it up.“

„The Circular Economy for Plastics“ Report 2024 provides further comparative information on material flows and recyclate quotas in Germany and Europe.

The use of recyclates made from polypropylene (PP) can reduce CO2 emissions

2. Plastic pipe industry as a „driver of innovation“

Sustainability as a core topic in the industry
Making the value chain more sustainable - in both an ecological and economic sense - has been a key issue in the energy-intensive plastic pipe industry for some time now. The industry, which has a high consumption of primary raw materials, is increasingly endeavouring to drive forward the development of new technologies and the creation of functioning material cycles.

Numerous suggestions and recommendations for action from industry associations and stakeholders have been incorporated into the current draft of the NKWS.

For example, in its „KRV Recommendation to Politicians“ (publication „Impulse“, p. 16), the Kunststoffrohrverband e.V. (KRV) advocated, among other things, ensuring the „promotion of closed material cycles and the establishment of green lead markets in the area of public procurement“ in the amendment to the NKWS as early as 2023.

Best practice
Rehau Building Solutions, headquartered in Erlangen, Germany, has developed a plastic wastewater system with which it aims to make civil engineering more sustainable, according to CEO Dr. Roger Schönborn.

In Rehau's „nevoPP“ plastic wastewater system, up to 80 % of the PP comes from industrial recyclates

The „nevoPP“ is 100 % climate-neutral: Up to 80 % of the polypropylene (PP) comes from industrial recyclates – such as production waste for construction and packaging applications. Only electricity from renewable energy sources is used in the manufacturing process for the sewer pipes and manholes. According to Rehau, „the consumption and CO2 targets of the production plant are 100 % transparent in accordance with the ISO 50001 energy management system and the ISO 14001 environmental management system“.

The extrusion system provided by GF can be used to join different materials into three- to four-layer pipes, the inner layer of which consists of recycled material or regrind, for example

Compared to a sewage system made of new material, the laying of a 50 km stretch of nevoPP is said to save around 320 tonnes of CO2, which is a significant reduction in emissions when laying 12,000 kilometres of sewer per year. According to the manufacturer, the service life should also be at least 100 years. „These and other measures, such as the use of 100 % green electricity in our European plants, demonstrate our commitment to environmental protection and the promotion of a circular economy“, says CEO Schönborn about the company's sustainability strategy. „We endeavour to combine quality and sustainability in order to improve the quality of life and protect future generations. Independent assessments and the results of our sustainability initiatives are regularly reviewed to increase transparency and trust in our measures.“

„We see working with plastics as a symbol of a very mouldable future“, says Otto Skrabala, Head of Technology Centre at GF Piping Systems (supplier of plastic pipe systems) at the handover of an extrusion line to Kunststofftechnik Paderborn (KTP) at the end of May 2024.
The jointly operated plant at Paderborn University is used for in-depth cooperation in the fields of recycling and innovative extrusion processes for plastics and enables the production of pipes, the inner layer of which consists of recycled material or regrind, for example. Investigations into process optimisation and the gentlest possible production of piping systems are at the heart of the collaboration. According to Uwe Grebe, Managing Director of GF Deka, the extrusion line is „a pilot line for the production of three- or four-layer pipes“. „Different material flows are combined in a spiral mandrel distributor. It is therefore particularly suitable for testing new innovative materials and further developed extrusion processes. The machine is designed in such a way that it allows great freedom in combining different materials with variable layer thicknesses.“

CRB test: fracture surface of a specimen

3. Life cycle of recyclates: New test method speeds up testing procedures

The current methods for testing the long-term properties of plastic pipes have proven to be time-consuming and are also considered unsuitable for products made from recyclates.

Cracked Round Bar Test (CBR) as a new international standard
A few months ago, the Würzburg Kunststoff-Zentrum SKZ, one of the leading accredited testing laboratories in Europe, added a new type of test method to its service portfolio, which is designed to investigate slow crack growth in PE pipes. According to a statement from SKZ on
26 June, the cracked round bar test has successfully passed the assessment procedure by the German Accreditation Body (DAkkS).

Using the CBR according to ISO 18489, which was already developed at the Austrian Polymer Competence Centre Leoben (PPCL) and, according to the latter, „is now an internationally used standard for assessing the crack growth resistance of pipe materials“, it is ultimately possible to make „a precise prediction of fracture mechanical lifetimes“. In this context, „the assessment of the effects of added or complete recycling materials on the long-term failure behaviour of pipes for non-pressurised applications“ is of particular interest.

Very short test duration in a challenging test segment
According to the SKZ, slow crack growth (Slow Crack Growth, SCG) is one of the biggest challenges when using polyethylene pipes for applications subject to internal pressure. These include, for example, gas and water supply systems or industrial pipelines. „The durability and reliability of these pipes depends largely on their resistance to SCG. The higher the slow crack growth, the longer the pipes can withstand the normal stresses of outdoor use, resulting in significant cost savings and an extended service life. This conserves resources and makes a valuable contribution to sustainability.“

One of the many advantages of the cracked round bar test is the enormous time saving of the method: „Compared to other test methods such as the FNCT (Full Notch Creep Test) or NPT (Notched Pipe Test), which can take several thousand hours, the CRB delivers results in a comparatively short time“, says the SKZ. „A rupture usually occurs within 24 to 48 hours, which significantly shortens the test duration.“

Modern, faster test procedures such as the CBR test appear to offer good starting conditions for taking account of the changing material flows in the plastic pipe industry. Rapidly increasing the recycling rate – particularly in the pre-consumer segment – and completely closing material cycles in future would be desirable. The German government's „Nationale Kreislaufwirtschaftsstrategie“ has set the course for this in Germany.