Fraunhofer UMSICHT Institute Branch Sulzbach-RosenbergFraunhofer develops recycling process for tar-containing road debris
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Recycling of tarred road debris
Recycle material from roads sustainably
If old roads have to be renewed, the question arises: Where to put the parts that are contaminated with tar? Existing disposal methods are expensive, not very sustainable and generate a lot of CO2. In the »InnoTeer« project, four Fraunhofer institutes are developing an alternative to render tar from road debris harmless and to recover the remaining mineral content in high quality. With just one plant, large amounts of CO2 could already be saved.
Road debris often contains high concentrations of harmful tar and must therefore be disposed of carefully.
Fraunhofer research teams are developing a multi-stage process to efficiently process tar-containing road debris in decentralised plants.
The entire process chain in the recycling of road debris is technologically optimised.
Every year, about 3.3 million tonnes of tar-containing road debris are produced in Germany: Two million tonnes of it end up in landfills, 300,000 tonnes are transported by truck from Germany to the Netherlands - to Europe's only asphalt processing plant to date.
The raw material losses are large and the costs for disposal are enormous: in Germany alone, they amount to a total of 223 million euros per year. In addition, transport and thermal treatment are associated with high CO2 emissions.
With the plant technology currently in use, the tar in the asphalt is burnt at temperatures of 850 to 1000 degrees Celsius. However, 90 to 95 per cent of asphalt is aggregate, usually stones of different grain sizes. At temperatures above 600 degrees Celsius, these stones can be damaged, their compressive strength decreases. As a result, the material cannot easily be used in new roads, and a valuable raw material is lost.
Fraunhofer starts InnoTeer project
In the »InnoTeer« project, the Fraunhofer Institutes IBP, IML, IOSB and UMSICHT are now developing a multi-stage process to efficiently process tar-containing road debris in decentralised plants. The project, which started on 1 April 2022, will run for three years; the total budget is 3.5 million euros.
»Our goals in the project are clear: less CO2 emissions through fewer transports and treatment at lower temperatures. At the same time, better quality and greater quantity of recycled material for reuse in new roads. In the end, landfilling should be almost completely avoided,« says project manager Dr Alexander Hofmann from Fraunhofer UMSICHT.
To ensure that only the tar-containing components from the road demolition have to be treated further and the rest of the material remains in its original state, a process for the optical detection of tar is being developed at Fraunhofer IOSB. In particular, spectroscopic methods are used for this. »A particular challenge here is to distinguish the tar-containing material from black mineral and bitumen,« says Georg Maier from Fraunhofer IOSB. The method is then optimised for real-time use and integrated into an optical bulk material sorting system. This allows the uncontaminated parts of the road rubble to be reliably separated from the tar-containing parts. Non-contaminated material can be reused immediately.
There is also a new solution for the tar-containing parts. These are not burnt in a CO2-intensive way as before, but pyrolysed at lower temperatures in the absence of oxygen. In this process, the tar is thermally decomposed and critical constituents are rendered harmless. The aggregate remains undamaged. As a by-product, so to speak, a synthesis gas is produced that can be used for energy generation.
What remains is sand, limestone and carbon. »At Fraunhofer IBP, we are developing ways to use this mixture in building products, for example to incorporate it into asphalt again,« explains Dr Volker Thome, head of department at Fraunhofer IBP. In addition, the life cycle assessment of the current procedure is being evaluated and compared with the novel approach.
In parallel to the sorting and treatment processes, Fraunhofer IML is developing models that can be used to precisely evaluate the material flows depending on the locations and number of plants as well as the means of transport used and to control them according to different target criteria. »We estimate that with just one plant in Germany we could reduce logistics costs by about 40 per cent, and with four plants by another 30 per cent,« says Ralf Erdmann from Fraunhofer IML, referring to the enormous volume of transport that would result from dispensing with environmentally damaging landfill.
Prototype plant with 300 kilograms per hour
At the end of the three-year project, there should be a prototype plant that can process 300 kilograms of tar-containing road debris per hour. This could then be scaled up to a larger plant that can process 20 tonnes per hour. »There is already a lot of interest from construction companies and authorities,« says Hofmann.
Project consortium and technical contact persons
Fraunhofer Institute for Environmental, Safety, and Energy Technology UMSICHT
Institute Branch Sulzbach-Rosenberg
An der Maxhütte 1 | 92237 Sulzbach-Rosenberg
Contact: M.Sc. Thomas Fehn
Telefon: +49 (0) 0157 4268840
thomas.fehn@umsicht.fraunhofer.de
https://www.umsicht-suro.fraunhofer.de/en
Fraunhofer-Institut für Bauphysik IBP
Fraunhoferstraße. 10 | 83626 Valley
Contact: Dr. Volker Thome
Telefon: +49 8024 643-623
volker.thome@ibp.fraunhofer.de
Building on knowledge - Fraunhofer IBP
Fraunhofer-Institut für Optronik, Systemtechnik und Bildauswertung IOSB
Fraunhoferstraße 1 | 76131 Karlsruhe
Contact: Georg Maier
Telefon +49 721 6091-649
georg.maier@iosb.fraunhofer.de
Fraunhofer Institute of Optronics, System Technologies and Image Exploitation IOSB - Fraunhofer IOSB
Fraunhofer-Institut für Materialfluss und Logistik IML
Joseph-von-Fraunhofer-Str. 2-4 | 44227 Dortmund
Contact: Ralf Erdmann
Tel.: +49 231 9743 160
ralf.erdmann@iml.fraunhofer.de
Logistics in practice - Fraunhofer IML