Practical testing of the processing of bulky waste,
mixed construction waste and used textiles in Thuringia

1 Introduction

The increasing demand for raw materials and the associated consumption of resources represent one of the greatest challenges facing modern industrialised society. To counteract these developments, the European Green Deal focuses on a transformation to a climate-neutral circular economy in which waste materials are to be utilised as valuable secondary raw materials. There is potential for the recovery and recycling of materials, particularly in the construction industry, the textile industry and private households.

One element of the Green Deal is the Circular Economy Action Plan, which aims to close material cycles and make resource-intensive economic sectors more sustainable. An important component of German environmental and resource policy is the Circular Economy Act (KrWG), which implements the EU directives on waste prevention, recycling and resource efficiency at a national level. The 2020 amendment to the KrWG, which strengthens the collection of waste, the recycling rate and the promotion of secondary raw materials, is of central importance.

2 Method

With its technical equipment, the Thuringian Innovation Centre for Recyclable Materials (ThIWert) offers an excellent platform for application-oriented research. It is of central importance for the project to analyse the waste streams of bulky waste, mixed construction waste and post-consumer textiles not only on a laboratory or pilot scale, but also under industrial conditions.

The methodological approach is based on a systemic circular economy approach that includes the entire value chain. The aim is to comprehensively characterise the aforementioned waste streams in order to systematically record and optimise their material recycling potential and contributions to decarbonisation. The methodology is divided into four coordinated work steps:

2.1 Collection and mobilisation

In the first step, a quantitative and qualitative analysis of the waste fractions is carried out, taking into account existing collection and collection structures. The aim is to identify potential for improved mobilisation of the material flows. To this end, data on transport and quantities are analysed and regional surveys and interviews with relevant stakeholders (waste disposal companies, local authorities, etc.) are conducted.

2.2 Processing and recycling

In the second phase, technologies for processing and material recycling are analysed. The technical suitability and efficiency of the various processes is assessed in the context of the respective material group. The aim is to identify high-quality secondary raw materials and optimise existing process chains.

2.3 Regulatory, economic and ecological assessment

Central legal framework conditions, in particular the Closed Substance Cycle Waste Management Act, the EU Waste Framework Directive and specific product and substance regulations, are systematically analysed. In addition, economic assessments and life cycle assessment analyses are carried out to quantify environmental impacts and sustainability potentials.

2.4 System integration and recommendations
for action

The results are summarised in an integrative manner in order to derive practice-oriented recommendations for action for politics, business and local authorities. The aim is to strengthen recycling and significantly reduce CO₂ emissions.

3 Waste generation in Thuringia

In 2023, around 75 000 t of bulky waste was handed over to the 20 public waste management authorities in Thuringia. This corresponds to a per capita volume of around 35 kg and is therefore around 20 % above the national average.

In the same year, the amount of construction waste handed over to the local authorities in Thuringia was 108 000 t. By comparison, the total volume of construction waste generated nationwide in the same year was 55.2 million t.

The collection of post-consumer textiles (PCT) in Thuringia is currently carried out by 98 commercial and non-profit organisations. There has been a sharp decline since 2024, which is mainly due to falling market prices for used clothing. To date, notification procedures in accordance with Section 18 KrWG do not require the reporting of collected quantities. The local authorities in Thuringia only collected around 6 % themselves between 2018 and 2024. In future, in-house separate collection will increase and the focus will increasingly shift to collection systems.

4 Challenges for the use of secondary raw materials

The substitution of primary raw materials with recycled materials is a key prerequisite for closed material cycles. Material quality and the provision of sufficient quantities of unmixed fractions are crucial for economic utilisation.

The recycling of bulky waste has so far been limited due to its heterogeneous composition, inadequate separate collection and limited technical processing options. In view of the EU target of increasing the municipal recycling rate to 55 % by 2025, innovative processes for recovering recyclable materials are increasingly required.

The growing variety of materials and the use of complex composite materials make it difficult to selectively dismantle and separate mixed construction waste by type on site. This puts a strain on both construction site logistics and processing in stationary plants, which currently mainly use mechanical processes. In future, sensor-based sorting processes and automated separation technologies will be required to improve the quality of secondary raw materials.

A lack of usage quotas is hampering the expansion of fibre recycling in the textile sector. Globally, less than 1 % of used textiles are processed in fibre-to-fibre recycling. The heterogeneous colour shades and material blends of PCT pose challenges. Technological advances in the field of material databases, near-infrared sensors and colour cameras are improving the purity of grades. Further automation is required, particularly for the removal of impurities, defibration and chemical analysis.

5 Recycling options and processing requirements for material streams

The research project focuses on the development and testing of technically adapted processing methods in order to efficiently break down the recyclable materials contained in the respective material streams, separate them free of contaminants and provide them in the qualities required for downstream recycling or analysis.

In 2023, the material recycling rate of bulky waste collected in Thuringia was only 16 %, while 64 % was thermally recycled and 20 % landfilled. Metals are the most valuable fraction of bulky waste and are generally recycled to a high standard. Wood, on the other hand, the most significant component in terms of volume, is predominantly treated thermally in unsorted form.

According to the Waste Wood Ordinance, bulky waste wood can be recycled or used to generate energy if it is collected separately, depending on its pollutant content. Mixed assortments from bulky waste are generally assigned to waste wood class III, which considerably restricts material utilisation. One possible utilisation is the production of industrial charcoal through pyrolysis. While thermal utilisation primarily serves to generate energy, pyrolysis enables material utilisation with additional CO₂ binding potential.

For mixed construction waste, the separation of light materials (e.g. bricks filled with insulating materials), which are form-fitting but without a solid material bond, is suitable using air classifiers or wet mechanical sorting processes. If, on the other hand, there are material composites, such as bonded thermal insulation layers or plaster coatings on bricks, mechanical separation is necessary before sorting.

Tests on plastered sample walls, which were crushed using both an impact crusher and a jaw crusher, show the following results:

Crushing with the impact crusher leads to a higher degree of disintegration and a finer crushed product.

The jaw crusher produces fewer fines and therefore enables a more efficient recovery of unmixed building material particles.

The separation of gypsum plaster and mortar from brick as a wall-building material was also analysed. For building materials with a high gypsum content, material recycling is not possible and landfilling is made more difficult. The use of new near-infrared sorting technologies makes it technically feasible to separate the fractions by type.

In the case of textiles, the processing of the fractions sorted by material and colour depends primarily on the recycling process. In addition to processing requirements, such as the removal of non-textiles (haberdashery and labels), the removal of finishes and functionalisation is crucial. An overview of the technological maturity of recycling processes is provided by Huygens et al.

6 Outlook

In future, the planned processing trials will focus on testing a modular sorting plant that can be used to treat bulky waste and mixed construction waste streams on an industrial scale. The modular design of the plant enables flexible adaptation of the sorting modules used for different material flows and varying sorting tasks.

The shredded used textiles will subsequently be fed into a recycling process. The investigations are supplemented by laboratory analyses, which can be used to test the tolerance limits of the processes and to characterise and evaluate the quality levels of the secondary fibres produced.

7 Conclusion

The preservation of recyclable materials and the associated conservation of primary resources are of central importance for a functioning circular economy. The knowledge gained from the investigations is not only relevant for application in the Free State of Thuringia: They can also be transferred to other regions of Germany due to the standardised national regulations for the municipal disposal of bulky waste, construction waste and textiles.

The seRo.inTech research group is a research project funded by the state of Thuringia and co-financed by the European Social Fund Plus (ESF+).