There are many committed people working at the ZSW who care about sustainability and want to make a positive contribution to society and the environment through their work.
Here we introduce you to our colleagues.

Departments REG/SYS

A day with ...

Sebastian Holl, design engineer in the department of Renewable Fuels and Processes (REG)

The liquid is a gleaming bright turquoise colour. Sebastian Holl puts some white powder in the Erlenmeyer flask and gently shakes the glass container. The colour of the liquid turns dark purple. It may look like magic but it is just chemistry pure and simple. We meet Sebastian Holl at his place of work in the ZSW laboratory.

There are many small and large containers on the surface, each containing liquid of a different colour. He is like a magician, conjuring up new colours all the time. “I have always found chemistry fascinating,” he says. His love of tracing the origin of things and the pleasure he gets from breaking down matter into its various components were additional signposts pointing the way to scientific studies. “I wanted to study something practical which involves plenty of laboratory work,” he adds. He specialised in electroplating while studying for his degree in surface treatment technology and material science.


Electroplating, also known as electrochemical deposition, is the process of applying a metallic coating to a component, using either a chemical solution or an electric current. Sebastian demonstrates how the process works in the laboratory. We are faced with a conveyor line measuring five metres in length and consisting of row upon row of grey containers which all look the same. Each one holds a different liquid with a specific function.

Sebastian takes a metal disc and dips it into the grey containers in a certain order. “The electrodes are first activated and then coated using electric voltage,” he explains. The end result of the process is the coated electrode.


After completing his bachelor’s degree, Sebastian worked for three years in development for a manufacturer of process chemicals and then for two years as a process engineer at a large contract coating company. He was then hoping to do a master’s degree at the University of Stuttgart and, at the same time, he was looking for a job as a research assistant. He applied to the ZSW. “I applied for an internship and was offered a position as a research scientist,” says Sebastian, laughing as he recalls that the offer was too tempting to refuse. The job, after all, is all about process optimisation for hydrogen electrolysis. “Hydrogen production is exciting and I am conscious of the contribution I can make with my specialist knowledge of the subject,” says the design engineer. He also has a great deal of responsibility within his “quality control” remit. So he gave up the idea of doing the master’s degree and started working at the ZSW in May 2021. “There has not been one single day that I have regretted my decision,” continues Sebastian.

There are two interns in the laboratory next door who are busy working on an experiment. Sebastian Holl stops by for a quick chat about the test procedure and gives the students some tips on how to proceed. His brief also includes supervising the interns. There is a focus on teamwork at the ZSW where the working routines involve short chains of command. “My colleagues are really cool and we sometimes meet up for a beer after work,” he adds.

Dr. Jochen Brellochs, Circular Economy Project Manager in the Department of Renewable Fuels and Processes (REG)

Jochen is holding two bottles of granules. There are red granules in one bottle and grey ones in the other. “If you smelt the grey bottle, you would know straight away where the granules are from,” he said with a wink. The bottle contains dried sludge from a sewage treatment plant. Jochen turns this waste into something valuable and precious – and that is now in the other bottle. It is fly ash containing phosphorus. The metamorphosis takes place in the fluidised bed system – a huge structure made up of many silver pipes and hoses which is located in the ZSW pilot plant. The incinerator converts the sewage sludge into a phosphate-rich substance available for plant uptake. “When grain and vegetables are harvested, phosphorus is removed from the soil. We need to compensate for this loss otherwise the yield will decrease. Global phosphate reserves are finite and are confined to just a few countries. The recycling of phosphorus from streams of waste is therefore becoming increasingly important in Germany. Sewage sludge is one such waste stream and is typically incinerated at present without recovering the phosphorus contained in it. In Germany alone, 50 per cent of the total phosphorus requirement could be covered by sewage sludge,” explained Jochen Brellochs. Good stewardship of resources and replacement of raw materials with recycled materials – these are the subjects which fall within his postdoctoral research science remit at the ZSW.

Jochen Brellochs can almost be said to have been “home-grown in ZSW soil”. He came to the ZSW as a student assistant, wrote his thesis here, and was appointed to the staff in 2007. Since earning his doctorate in the field of biomass gasification, he has worked as a research scientist and project manager. He has been responsible for the fluidised bed system from the beginning. “The system is my baby – I conceived it and I have been growing it ever since. Now we are already in the third generation and it is getting more and more efficient,” added Jochen proudly. The subject of further development is also very important to him on a personal level. “This is what makes working at the ZSW so exciting. There is always a chance to explore other subjects, try out new things and expand your expertise. I value this freedom very much,” he continued. “Of course it is also a nice feeling to do something for sustainability in your own work. The demand for raw materials and energy is still increasing. Despite the high recycling rates in various sectors, it is still the case that precious few primary raw materials have been replaced by recycled materials.” And this is exactly what Jochen Brellochs is working on in his research into the circular economy.

Marion Walker, Systems Analysis (SYS)

The world in which Marion Walker lives consists of data, facts and figures. They are important, providing as they do a fundamental basis for key decisions. Marion Walker works in the Systems Analysis department at the ZSW which plays an active part in the creative process around the energy transition and advises politicians. In their remit in this context, Marion and her colleagues are responsible for monitoring courses of action, evaluating approaches, examining innovation mechanisms and investigating ways of adding value, and they ultimately use the data obtained to develop scenarios and solutions for a sustainable energy transition. “Each and every project is a new challenge requiring a fresh, individual approach,” said Marion. The job calls for a systematic approach to the relevant goal and an ability to think in abstract terms and draw logical conclusions.

Marion Walker at her desk with a colleague.
Marion Walker working on her computer.


Marion Walker joined the ZSW in 2007 where she was working full-time until 2010 and is now employed part-time following the birth of her twins. She has been occupied with the subject of renewable sources of energy since the beginning of her professional career. After studying forestry in Rothenburg, she initially worked as an engineer in a biomass cogeneration plant. In 2004 she switched to the Working Group on Renewable Energy Statistics (Arbeitsgruppe Erneuerbare Energien-Statistik - AGEE-Stat) which was headed up by the ZSW at the time, having been set up by the Federal Ministry for the Environment with the aim of improving the availability of data on renewable energies in a bid to facilitate political decisions. She is currently working on a number of projects including the brochure “Renewable energy sources in figures” (“Erneuerbare Energien in Zahlen”) which is being published by the Federal Ministry for Economic Affairs and Climate Action. “We have to present the facts and figures in such a way as to make it easier for politicians to see the bigger picture,” she continued. “It is rewarding for me to see how the data and the results of my work are being incorporated into policy decisions,” she concluded, adding why she likes her job at the ZSW where the benefits for her include good teamwork and the opportunity to combine family and working life.

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