Hydrothermal gasification: a promising sector for the energy transition

What is hydrothermal gasification?

Frédéric Julliard (FJ) It’s a physicochemical process that transforms various types of wet or liquid waste and biomass residues into methane-rich renewable gas under high pressure and at high temperatures. It also allows for mineral salts to be extracted from inputs, which are recovered in the form of fertilizers, and to recycle the water that makes up more than 80% of this type of waste. A wastewater treatment plant can hence be converted into a circular economy factory.

Woot de Groot (W de G) There are many benefits to this technology. It converts almost all of the waste’s carbon content into gas, and recovers mineral salts and water, making an important contribution to the circular usage of waste flows. The technology can be used on an industrial scale due to the speed of the conversion (just a few minutes), its high energy yield, and its modular, compact facilities. Once the raw gas has been purified, renewable gas can be injected into the existing network at high pressure. Finally, it eliminates all trace of microplastics, pathogens, bacteria or viruses.

What stage are you at in developing this process?

W. de G. From 2019, we have demonstrated our ability to control the whole gasification process on an industrial scale. This includes blending the raw materials, conversion, gas processing, and high-pressure injection into the network. Now, we are focused on commissioning our first industrial demonstrator plant in Alkmaar in the Netherlands (around 20 MW capacity). Production is set to begin this summer.

F. J. From our side, working alongside our academic partner, the Institut Paul Scherrer, we are testing our first pilot installation (150 KW capacity) near to Zurich. And we will soon begin the installation of a pilot demonstrator in a municipal wastewater treatment plant, which will be tested under real-life conditions over several months in early 2023.

What did your development strategy involve?

W. de G. With the support of our partners – pension funds and the national promotional bank – we launched several large-scale pilot projects to develop and test the technology. At the same time, we set up our own research centre and our team. Based on SCW Research’s results, the pilot projects and the first industrial-scale facility, we now have an industrial-scale technology that we are able to duplicate.

F. J. We opted to develop our pilot in a laboratory setting. This allows us to collect data and to carry out many tests on various raw materials in order to design prototypes.

Do you think that your experience could support the sector’s development in France?

F. J. In terms of developing the technology, for sure. France does not have the technology, but it has a head start with its consultants and its network of highly committed partners. Gas operators are genuine ambassadors with a lot to offer.

W. de G. The rules for injecting gas into the network under high pressure are very strict. We needed some time to meet these demanding gas quality specifications, as this quality is based on our own system for processing high-pressure gas. As things stand, our technology has proved itself up to the task, include the gas processing system. Transmission and distribution network operators could consider the possibility of less restrictive specifications for specific injection points – and France could be a frontrunner in this area.

What can we do to develop a sustainable industrial European sector?

F. J. For a long time, industrial companies have been committed to a “zero carbon” strategy. And they are still leaning towards more sustainable technologies. For the municipalities, regulations are going to play a key role.

W. de G. HG is a comprehensive, fast and efficient technology. It allows for the treatment of contaminated wet waste flows and for the conversion, in just a few minutes, of 99% of the organic matter – compared to 50% with fermentation. After recovering valuable minerals, the residues are almost non-existent. This is something that should motivate industrial companies, government bodies and local authorities to adopt the technology!

So will HG play a major role in Europe in 2050?

W. de G. Absolutely. We will be able to produce more than 100 TWh per year from only EU sewage sludge - i.e. 5% of Europe’s current gas consumption. And it’s not just about sewage sludge. The potential is even greater if we include agricultural residues, end-of-life plastics and industrial waste, which can be converted into renewable gas with a significant impact on reducing CO₂ emissions.

F. J. This technology can – and should  – benefit the whole world, because industrial and wastewater sludge are everywhere!

Why are you taking part in the Bio360 Expo trade fair?

F. J. We are a small startup, and we need industrial partners to take things to the next level. The Bio360 Expo trade fair is a chance to present our technology and meet partners. With the support of stakeholders like GRTgaz, we will be able to take up a long-term position in the sector.

W. de G.

This was a chance for us to get to know the French market and meet partners who can help us develop HG in France. If we want to meet the goals of the Paris Climate Accords, the time to take action is now.

In March 2021, along with 26 partners, GRTgaz launched a national hydrothermal gasification working group (GT GH).

The goal? To promote the emergence of demonstrators and create favourable conditions to prepare for the technology’s industrialisation: defining a national regulatory framework; supporting pilot projects; identifying the best business modes, etc. Five members of the working group were at the Bio360 Expo trade fair, where they explained the reasons for their commitment.

“With its drive and its wide-range of stakeholders, the GT GH speeds up hydrothermal gasification’s arrival on the market and paves the way for industrial-scale production. French stakeholders from science and industry are strongly represented.”
Fabien Michel, VOLTIGITAL

“Our activities generate wastewater sludge, the current recovery methods for which are sub-optimal. Developing the HG sector seemed vital as a way to promote the solution and work together to overcome the regulatory and technological challenges.”
Mathieu Boillot, responsable d’Axe stratégique, SAUR

“As a component supplier that is heavily involved in the gas sector, we offer a manufacturer’s perspective, in particular regarding the industrial feasibility of technologies, in application of our R&D programmes.”
Fabrice Piotrowski, Directeur commercial, GAZFIO

“HG is one of the waste recovery technologies that France will soon have to manage. Within the GT GH, we want to be the player that can develop this technology from existing laboratory-scale research.”
Paul Clemens, Leroux & Lotz Technologies

“Our goal is to become a leading player in the HG market by setting up France’s first demonstrator as part of the experimentation contracts proposed by the French Directorate-General for Energy and Climate (DGEC).”
Thomas Chauveau, Directeur Power & Gaz Renouvelable, VINCI Environnement