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At the Research Center of Post-Mining (FZN) at TH Georg Agricola University (THGA), Bochum/Germany, Julia Tiganj (Figure 1) is studying the socio-economic aspects of post-mining. In times of raw material scarcity and the energy transition, the economics researcher’s attention is especially drawn to China. Will the world’s second-largest economy manage the transition to renewable energy? What are the greatest challenges they face and what will the rest of the world gain? There’s not much research yet but the topic is super hot right now, says Julia Tiganj being interviewed by Carmen Tomlik from the FZN.

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Carmen Tomlik: In your expert opinion, where does China stand on the energy transition and on post-mining?

Julia Tiganj: That depends on where you look. There are many provinces in China which vary greatly, e. g. in their reliance on coal. There are regions which are already working sustainably. On the other hand, there are provinces whose economies rely heavily on mining. Here, coal secures a lot of jobs, taxes, pensions and, of course, supports national economic growth – which is one of China’s primary goals. As you can see, the gulf between them is massive. For this reason, it will be difficult in future to meet the many different economic requirements and the needs of the people in the different regions. There are interesting pilot projects, e. g., some people are thinking of using old, disused mines to create “underground cities” to compensate for the demand for space in the cities. Of course, the idea is controversial – but it is quite an innovative one and begins to face the issues of post-mining. China is also a global leader in satellite technology. Here the question is how far this expertise is being used to monitor the legacy left by mining.

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Tomlik: China without CO₂? What are the greatest challenges on the way to carbon neutrality?

Tiganj: Coal is still the easiest and safest way to secure a stable energy supply. China intends to become carbon neutral by 2060. However, this also means that the highest CO₂ emissions peak needs to be behind them by 2030. At the moment, they are therefore still building new coal power plants which are designed to run for 40 years. These power stations, however, meet the latest environmental standards and are intended to replace out-dated, inefficient plants. At the same time, China is already a market leader in renewable energy. Around 90 % of the energy concentrates used in solar panels, silicon batteries or wind power are made here. Until now, preventing climate change had no priority within China itself. The latest five-year-plan, however, demonstrates that China wants to become “greener” and has recognised the urgency of this.

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Tomlik: What does “greener” mean in this case?

Tiganj: That’s the next big challenge. After all, renewable alternatives also produce CO₂ and are not yet 100 % recyclable. The rotary blades of wind turbines, e. g., are disposed of as hazardous waste after being in use for only 20 years. Air pollution or poisonous wastewater threatens certain areas of land and the people who live there so that clean energy can be produced in a different part of the world. This is not sustainability, this is a displacement of climate problems from A to B under the smokescreen of a green future. As you can see, the whole setting is far from ideal – and now we haven’t even talked about the labour market and the long-term challenges that structural change would bring to Chinese coal-mining areas. Nevertheless, it is an important step to say: We are reorienting ourselves, we are doing research and we want this transformation.

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Tomlik: What would the rest of the world gain if China becomes carbon neutral?

Tiganj: When large, influential players like China pay more attention to sustainability and protecting the climate, this has a positive impact on everyone else. Direct neighbour states often orient themselves in accordance with dominant China and its approach. Depending on import and export dependencies, other countries may also find it necessary to reorient themselves in order to keep up. Also, China is an important trade partner in rare earths and is highly influential on the advances of e-mobility in Europe or the USA. This and many other aspects are factors which are helping processes to become more sustainable globally. Generally, a lot of research and development is still needed in order for the energy transition to be successful. Here too, a “green” China could become an international driver of innovation. (THGA/Si.)

The Research Center of Post-Mining (FZN) at the TH Georg Agricola University (THGA), Bochum/Germany, has a broad field of focus. When it was established in October 2015, research focused initially on the perpetual tasks of the German coal mining industry: long-term mine water management, the management of polder areas and groundwater purification on former mine sites. In May 2019, the FZN added “geomonitoring in post-mining” to its research profile. The aim of this research is to develop innovative technical systems for the integrated monitoring of post-mining activities. The FZN celebrated its fifth anniversary in 2020 and since then has expanded its research further to include “materials science for the preservation of industrial heritage” and “reactivation and transition”.

As a result, the FZN has all the skills and expertise required to help make the post-mining era sustainable, environmentally friendly and economically successful. The aim is not only to preserve this ever-growing expertise, but also to apply it in new ways. The interdisciplinary team shares its findings at specialist conferences and in working groups, and also makes the information available to the public in the form of studies and publications. Since 2019, the FZN’s final reports and studies have also been available as part of its scientific series “Reports on Post-Mining,” which is self-published by the THGA. Two reports have been published to date. In these reports, the authors examine aspects of the mine water rebound process in underground mines.

Volume 1 “Evaluation of Mine Water Rebound Processes” (Melchers et al., 2019) compiles the diverse experiences gained in the long-term and environmentally friendly management of mine water in selected European coal-mining districts (Figure 1). The hydrogeological, mining and water management aspects are systematically evaluated and site-specific features identified. The findings help to illustrate the mine water rebound process and aid understanding. Building on this, volume 2 “Model-Based Sensitivity Analysis of System-Determining Factors”(Westermann, 2000) provides an overview of the key natural and anthropogenic influencing factors. The scale of the effects of certain factors is determined for three underground mines by way of an example and applied to other sites. The findings are used to help actively shape the mining life cycle and plan ahead for the post-mining era.

The plan is to continually expand the scientific series “Reports on Post-Mining” with the FZN’s wide-ranging findings on the topics of mine water management, geomonitoring, materials science and structural change measures. Previous and future reports can be accessed free of charge in digital format at www.nachbergbau.org/berichte-zum-nachbergbau. (THGA/Si.)

Our underground is on the move. However, the shocks are often so small and spatially restricted that they are only detectable for very sensitive sensors. Even where mining was once conducted and people interfered with the natural geology and deposits, it may subsequently cause microseismic shocks. Paloma Primo, scientist at the Research Center of Post-Mining (FZN) at the TH Georg Agricola University (THGA), Bochum/Germany, pursues these mini-movements. In the new research project “PostMinQuake”, the expert examines how they occur exactly, identifies particularly endangered structures and develops a long-term risk management system for affected regions (Figure 1). To this end, she works closely with many European partners. Because also in the Czech Republic, Poland and France the post-mining period should not become a “nail-biting affair”. “The joint project is just as complex as the circumstances underground”, says Primo. “Our investigations go beyond the simple connections between seismicity and the geological activities in the decommissioned coal mines partly filled with water.”

Experts from various disciplines are working together in the project, including surveyors, geotechnical engineers or hydro-logists. Together they monitor the geological dynamics in the respective test areas, which have been changed by coal mining – in Germany this is mainly the Ruhr area, the Ibbenbüren and Aachen mining districts. “In these areas we document microseismic activities underground roughly once a week. There are also records from the past, which we analyse and put into context.” Primo obtains her data from the Geological Survey NRW, RAG Aktiengesellschaft, the Institute for Geosciences and Natural Resources (BGR), as well as seismological stations at the Ruhr-University Bochum (RUB). “At these stations we can determine time, size, place and depth of the event.”

The experts are pursuing an important common objective, explains Primo: “With our research we want to guarantee long-term safety, create transparency and inform the public. Because every municipality and every former mine operator should have sound knowledge of the processes that take place underground. When it comes to the topic of ground movements there are many fears and misunderstandings about what microseismic events are and the effects they can have.” Therefore, the main objective of the project is to gain a better understanding of the mechanisms of microseismic events after mining and create plans for the long-term monitoring of the soil after mining.

What external factors cause the micro-shocks? What factors can be used to realistically simulate the impacts on the PC? And how can satellite images help to properly interpret the data acquired from underground? “We’re talking here about vast amounts of data, which first of all we have to standardise in order to make it comparable and then be able to evaluate it using the latest methods”, says Primo. Over the next three years the project team will develop a reference database from the findings for European areas after mining. The research should also help to develop new monitoring strategies and interpretation methods for areas with increased risk of earthquakes. The project is part of the EU-financed Research Fund for Coal and Steel (RFCS). (THGA/Si.)

Construction sites, closures, narrowed lanes: Since the end of March 2020 the patience of drivers who use the Dortmund/Witten motorway junction is being tested. But the remediation work on the A44 is urgently required, says Cedric Kamgaing Kamdom: “ Most recently we detected and backfilled a hollow space, which was around 10 m high and 3 m wide – roughly as big as a single-family house. And it was just below the road surface”, explains Kamgaing Kamdom, who works as a project manager at the responsible engineering firm arccon -Ingenieurgesellschaft mbH, Gelsenkirchen/Germany. The experts have now piped around 800 t of concrete mix into the holey underground in order to secure it. This corresponds to around 30 full semitrailers.

The near-surface cavities originate from olden times: At one time the miners here mined the -Vereinigte Wiendahls-bank mine through the ground. The mine closed down in 1924. The available data is sparse.

“The plans for the deposits are over 100 years old. This does not make it any easier for us.” Apart from that, there is also the so-called illegal mining, which is not recorded anywhere. You cannot simply drill straight over it, explains Kamgaing Kamdom: “Our most important task is to optimally detect the suspected cavities in order to save time and costs.”

And the concrete mix needs to be carefully chosen, depending on the nature of the cavities and loose zones. At the beginning of such a project is a basic evaluation, during which old mine plans are also evaluated. They can provide guidance on surface openings, old tunnels or working areas of a mine. Following this basic research, if necessary exploration, safety and safeguarding works are planned, tendered and executed in the form of drilling and backfilling at extreme depths.

Specialist knowledge that Kamgaing Kamdom acquired in the course of his studies. Five years ago he came from Cameroon to Germany and decided to study at the TH Georg Agricola University (THGA) in Bochum. He acquired a fresh perspective in the master programme “Geological Engineering and Post-Mining”: “I was unfamiliar with the labour market beforehand, but did know that the coal mining sector in Germany was due to end in 2018 and that then certainly people who are knowledgeable in post-mining would be recruited”, says Kamgaing Kamdom, who already studied geosciences in his home country.

He turned out to be right. Experts at the interface between mining, surveying and geotechnical engineering are not only in demand here in Germany, but also internationally. Because the mining of raw materials leaves its mark worldwide (Figure 1). Special safety and restructuring measures are required in order to manage the risks at former mining sites. The master programme at the THGA, which is the only such programme offered in Germany, trains engineers to responsibly plan and execute the complex processes of mine closures and the aftercare. This also includes intelligent after-use in the affected regions.

For Kamgaing Kamdom the language was initially a little obstacle. “Especially in the lectures I had to be very attentive, but the good contact with other students and the lecturers made things a lot easier. The course is also very practical and you are out and about on the road a great deal”, says the graduate.

And what’s happening now on the A44? “We are currently on schedule. But there is still one part to come.” Here there may be more unexpected challenges hiding somewhere for the engineers, but Kamgaing Kamdom is confident: “When we have completed our work, probably in summer 2021, we are forever on the safe side.” Ideally, for drivers this means: For starters, peace and quiet on the A44. And for Kamgaing Kamdom: Off to the next construction site! Because the post-mining era is significantly longer than the mining era itself and brings full order books also in the future. (THGA/Si.)

Save the date: Bereits zum sechsten Mal veranstalten die Technische Hochschule Georg Agricola (THGA) und die Bezirksregierung Arnsberg ihre gemeinsame Fachtagung. Thema diesmal: „Grubenwasser – analog gedacht, digital diskutiert!“ Dazu treffen sich die Expertinnen und Experten dieses Mal ausschließlich online!

Wie gelingt ein verantwortungsvoller Umgang mit den Folgen des Bergbaus? Und welche Perspektiven bietet die Nachbergbau-Ära für Mensch und Umwelt? Diese Fragen stehen im Mittelpunkt der kommenden Fachveranstaltung NACHBergbauzeit in NRW. Die THGA und die Bezirksregierung Arnsberg als Bergbehörde NRW führen die interessierte Öffentlichkeit sowie Expertinnen und Experten der Branche zum intensiven Themenaustausch zusammen. Der Dialog im März 2021 findet erstmals als Online-Konferenz in der Zeit von 10:00-13:00 Uhr statt. Sie sind hiermit herzlich eingeladen, sich an der digitalen Diskussion zu beteiligen.

Themen 2021:

• Welche technischen Herausforderungen ergeben sich beim geplanten Grubenwasseranstieg in den ehemaligen Steinkohlerevieren an der Ruhr, der Saar und in Ibbenbüren?
• Grubenwasseranstieg europaweit: Was können wir von unseren Nachbarn lernen?
• Welche Methoden eignen sich zur langfristigen Überwachung von Bergbaufolgen?
• Wie lassen sich die Erkenntnisse aus der Steinkohle auch auf andere Bergbauzweige übertragen?

The history of mining is long – but the history of post-mining will be much longer. For five years now the Research Center of Post-Mining (FZN) at the TH Georg Agricola University (THGA) in Bochum/Germany has been attending to the issues that emerge as mining activity ceases. As the world’s first institution, it takes a comprehensive look at the post-mining era. The scientists are examining not only the tasks that mine water or former mining areas leave behind. They are also developing modern monitoring methods, advising affected regions on the structural transformation and trying to preserve the industry culture.

“The challenges of post-mining are complex, that’s why we are also becoming increasingly complex”, says Prof. Ulrich Paschedag, Head of FZN (Figure 1). “Since October 2015 we have been pooling the necessary know-how to shape the consequences of mining in a technically, economically and environmentally friendly manner.” In the interdisciplinary team around 40 independent experts in mining, geology and geo-technology, hydrogeology, chemistry, electrical engineering, materials science, land development, mine surveying and economics, all work closely together. This is the core around which a broad network has been established, nationally and internationally.

In the beginning the focus was still on researching the so-called perpetual tasks of the coal mining industry, but the FZN has been expanding its focus to this day. From the integrative approach come the four research areas: perpetual tasks and mine water management, geomonitoring in post-mining, materials science for the preservation of the industrial heritage, as well as reactivation and transition.

The experts are currently developing the scientific bases for an ecologically and economically compatible mine water ascent. The experiences from other European territories, in which such processes have already taken place wholly or partly also help. “The mine water rise is technically controllable”, says Prof. Christian Melchers. “Now it is about designing sustainable water management systems within the closed mines. Only then can the water resources in the former mining landscapes be reshaped in a near-natural way”, states the expert. The findings can also be transferred to other mining activities such as lignite or the gas and oil industry.

In the future geomonitoring will be about monitoring the impacts of mining over the long term using modern technology. “For this we must skilfully connect lots of information – like with a puzzle”, states Prof. Tobias Rudolph describing his area of research. Satellite data, historical maps, soil samples or multispectral aerial views with the drone are used here. “From these we can draw conclusions, e. g., about soil changes and detect changes in the vegetation.” In close cooperation with materiaIs scientists at the German Mining Museum (DBM) in Bochum, new methods are also being developed at the THGA to slow down or ideally stop ageing processes. The post-mining experts are helping to preserve the industry culture such as old winding towers or blast furnaces.

The cutting-edge research in the area of post-mining is in demand worldwide. More and more countries are interested in a far-sighted approach for handling active and former mining sites. The knowledge from Bochum also helps to make future mining processes more environmentally friendly. The FZN is in constant dialogue with its many international partners. It will also remain challenging in the future. “We are concerned with highly complex questions and interrelationships that take place in locations that are frequently still difficult to access. Underground, e. g., in places most people have never been to, and which will soon become inaccessible to all of us”, says Prof. Paschedag. “This is the reason why we, as scientists, have to make a special effort to formulate our post-mining findings in a way that can be generally understood by everyone.”
(THGA/Si.)

RAG Aktiengesellschaft, Essen/Germany, started to digitise abandoned surface openings, shafts and mining galleries of the coal mining sector via the Sigfox-0G network. There are around 60,000 in North Rhine-Westphalia alone. The aim of this IoT connection is the continuous monitoring of changes in real time in order to increase protection against sinkholes and reduce the effort of on-site inspections. The Sigfox–0G-based mining shaft monitoring system, which is also used for long-term documentation, has been designed by the Research Center of Post-Mining (FZN) and the Electrical Engineering/Information Technology and Industrial Engineering research sector of the TH Georg Agricola University (THGA) in Bochum/Germany and developed to series production in cooperation with the RAG (Figure 1).

The 0G-based remote monitoring system which is operated by a solar generator comprises pull-wire switches and a microcontroller with radio transceiver, which transfers the data via Sigfox-0G networks to a monitoring cloud. The sensors monitor, e. g., the vertical movement of the filling column of an old mine shaft. The data collected via Sigfox-0G network can be shown in the cloud for monitoring purposes and in the event of an alarm can be automatically sent to a predefined message chain by SMS and e-mail.

“It is necessary to constantly monitor the over 5,200 km² hard coal easements in our area of responsibility which have around 7,200 former surface openings because sinkholes are possible at any time in a section of around 100 km². Therefore, around 6,000 inspections are carried out every year in order to be able to take preventative action in good time. To minimise these on-site inspections and for real-time monitoring of any changes, selected surface openings are now also constantly monitored via a Sigfox-0G network connection”, says Frank Wollnik from the Site and Geo Services Division of RAG.

“The Sigfox-0G solution for shaft monitoring is an element of the so-called Mineberry system, which works completely independently and is solar-operated and is suitable for almost every type of old mining objects thanks to the modular structure. In order to implement the cloud connection of our remote monitoring solution in a manner that is cost-efficient, long-lasting and maintenance-free, we connected proven sensor technology to the innovative Sigfox-0G network. And as it can be used worldwide without any roaming charges, our solution can also be used worldwide”, explains Prof. Bernd vom Berg, Head of the Laboratory for Electrical Measurement and the Laboratory for Microprocessor Technology at the THGA.

“The RAG monitoring system is an excellent example of the remote monitoring of things and states, which up to now could not always be given special attention because it was too expensive or too energy-hungry to record all this data in real time. However, with Sigfox 0G real-time monitoring of even the simplest objects and states is possible. In the case of mining, it is easy to imagine that there are many control points worldwide, which can be monitored via a Sigfox-0G network. Especially because after the fossil-fuel phase-out no more money is earned, cost-efficient and low-maintenance data communication channels like Sigfox-0G offers are particularly important”, explains Stéphane Pâris, Technical and Network Director at Sigfox Germany.

The 0G controller is installed aboveground outside the possible Ex zone for the remote monitoring system for surface opening monitoring, whereas the Ex-protected sensors are installed in the shaft. As radio signals can be transmitted via the Sigfox-0G network across many kilometres, their use is also possible in areas with a poor mobile phone connection. The controllers can also be operated for many years without changing the batteries thanks to the battery-saving radio technology. Installations in the equally radio-critical underground environment can be found in the water supply network of the city of Antwerp. However, prerequisites for extensive underground installations are repeaters, which must be positioned every 3 to 5 km. (THGA/Si.)

How can a former mining area be transformed into a revitalised landscape? What needs to happen so that the areas can be used once again? To be able to produce comprehensive simulations of scenarios such as this in future, the new “TRIM4Post-Mining” project is now being launched with participation of the TH Georg Agricola University (THGA), Bochum/Germany (Figure 1). European experts from the fields of industry and research are working together to develop an integrated information modelling system that will allow virtual planning for the process of phasing out coal – from active mining, all the way up to repurposing the former mining areas. The aim here is also to contribute to valuable materials being recovered from old stockpile locations of the lignite and coal industry. In this endeavour, the scientists from the Research Institute for Post-Mining (FZN) at the THGA are collaborating closely with the TU Berg­akademie Freiberg, the Delft University of Technology (TU Delft), as well as the companies Beak Consultants, MIBRAG, Special Industries and Eijkelkamp SonicsSampdrill. The project is part of the EU-financed Research Fund for Coal and Steel (RFCS).

Even virtual and augmented reality are to be used in order to optimise the repurposing of mining areas, as explained by Stefan Möllerherm from the FZN: “To this end, however, we first need to feed our planned database with lots of information, which we can then examine spatially and over time. Modern monitoring systems such as satellites, high-resolution images from drones or multi-sensors help us here.” The scientists are also keen to analyse the dynamic processes in spoil tips, as well as deformations or geochemical processes underground. “This will ultimately lead to an interactive TRIM, a “Transition Information Modelling System”, which will enable us to produce detailed predictions and then use these to derive a system of risk management,” hopes Möllerherm.

Not only the technical effects of post-mining can be simulated in this way. Indeed, it is hoped that the planning system will later be able to check both the social and ecological feasibility individually. This will then also make it possible to identify areas requiring special redevelopment or long-term monitoring. “There are many rules and requirements to be observed, above all when the former areas are to be used for agricultural purposes, for local recreation or for other industrial applications,” comments Möllerherm. The objective of the post-mining experts with the “TRIM4Post-Mining” project is to massively simplify the comprehensive planning and testing processes required. (THGA/Si.)

We are surrounded by standards in our day-to-day lives. We all use the designation A4, e. g., as a standardised value for the height and width of paper sheets. Yet when it comes to standardising something worldwide, this is where the International Orga­nization for Standardization or ISO steps in. There are ISO standards for almost all sectors – from quality management, through physical units, all the way up to languages or correct dimensioning of sea containers (ISO 668) and soon also for post-mining. On the initiative of the German Institute for Standardization (DIN) and the Civil Engineering Standards Committee, a new committee has been established to draw up an international standard for the management of post-mining areas. Experts from the Research Institute of Post-Mining (FZN) at the TH Georg Agricola University (THGA), Bochum/Germany, are also involved in this.

“There has actually been considerable interest worldwide in standardising the handling of post-mining issues for quite some time,” explains Prof. Peter Goerke-Mallet, who is contributing his expertise in the new international committee together with Sebastian Westermann from the FZN (Figure 1). “Around the world, former mining operations are leaving behind a wide range of challenges and unresolved issues, often with a negative impact on both, people and the environment. However, the post-mining era also offers many interesting prospects. But for these to be utilised as effectively as possible, we need a standardised way to manage mining operations that have been decommissioned.”

Germany is a post-mining country, and thereby an international forerunner in terms of structural transformation, risk management, land recycling and similar. This experience is very much in demand. Alongside the experts from the FZN, representatives from mining and environmental authorities, as well as mining companies and consulting firms are all members of the international team of consultants. Under the leadership of Australian post-mining expert Corinne Unger, they will be drawing up a universal standard on “managing mining legacies” over the course of the next few years. The common objective is clear: “The focus is on addressing the consequences of mining operations as comprehensively as possible in order to reduce their risks and develop the opportunities of post-mining,” comments Westermann. “We are therefore not only examining the ecological and economic issues, but also the social issues in the environment of former mining sites and how they can be further optimised in future.”

The cooperation is also delivering new opportunities for the FZN itself. The global challenges are providing the scientists with new impetus and information for further research projects. (THGA/Si.)

On 15th May 2020, the TH Georg Agricola University (THGA), Bochum/Germany, appointed Kai van de Loo as honorary professor. Prof. van de Loo has already been passing his knowledge on to budding industrial engineers at the THGA for many years in his role as lecturer. From 1992 to May 2020, he worked for the German Coal Association (GVSt), Essen/Germany, in various functions and roles. In future, Prof. van de Loo will also be contributing his expertise to the Research Institute of Post-Mining (FZN) at the THGA.