Interview with OWS

"It would be really nice that we can escape the lab and make a process that has a market, and have a future proof technology alongside with our anaerobic digestion technology that we can use for a treatment of organic waste."

Filip Velghe Process engineer

OWS is involved in several European bio economy projects. Could you explain your role in the different projects?

We have quite different roles, because at the moment we are in about 15 projects. OWS is a standardization lab for biodegradation and biodisintegration, so in more than a half of the projects our task is to assess the biodegradability of novel products and it is a large part of the lab activity. In some of them we are also performing LCA which is mostly combined with biodegradability, anaerobic digestion (AD) or composting.

And of course anaerobic digestion is an important task in may projects. The development of our anaerobic digestion technology DRANCO was the first commercial activity of OWS and as such still makes a large part of our daily activities. Through participation in research projects, we continuously aim to further improve our technology, both from a biological and technical perspective. In the recent projects, anaerobic digestion is mostly used in combination with other technologies and other partners or research centers are performing novel extraction technologies on organic waste streams or byproducts. But in the end some streams where nothing more can be extracted from remain, which still contain most of the original mass. At OWS we use it to produce biogas and make the overall extraction cascade more energy neutral.

In recent years, we’ve taken the AD process one step further (or one step back if you look at it biochemically) by focusing on volatile fatty acid production from organic waste streams and blocking the final methane conversion step. With this adapted AD technology, we hope to contribute to the production of new platform chemicals (VFAs) for the bio-economy as alternative to sugar.

What are the main challenges of the projects and what is important for you in the project?

Historically we are active in building AD plants that use municipal or industrial organic waste. With the growth of the bioeconomy  new chemicals are being extracted  out of this biowaste but in the end we still have a waste stream or residuals that has no value for chemical extraction.

So the challenge is to adapt the AD process and still recover the energy that is left and at the same time produce high quality compost or recover the nutrients for use as a fertilizer or soil improver.

And finally, about 5 years ago we started to develop the carboxylic acid production process to go beyond energy recovery. By integrating this new development with AD we are able to produce both chemicals, energy and fertilizer from heterogenous organic waste streams. That is where VOLATILE started and now with CAFIPLA we have a second project on this topic. We also have another project RUSTICA that started this year but that one focuses more on the recovery of nutrients from the carboxylic acid broth.

OWS is a relevant player in the field of innovative designs for biogas plants, what would say, how could biogas play a role in the future?

Biogas will play a role but the role will change. When I started in anaerobic digestion about 15 years ago it was really regarded as another way of producing renewable energy alongside with wind and solar power. But in recent years, solar and wind power have really boomed and the cost per kWh went down for these technologies whereas for anaerobic digestion the costs have more or less remained identical.

But anaerobic digestion should not only be regarded as an alternative for wind or solar in renewable energy production but more as a waste treatment technology, although it also has some unique advantages for renewable energy. With biogas you have 24/7 energy production and can more predict your output from it. As a gas it is also easier to store for a longer time in the existing natural gas grid, and compared to electricity no expensive batteries are needed. So biogas production should be seen as a waste treatment technology with the advantage that it also produces renewable energy.

And as I said before, in the research projects we are involved in which focus on the extraction of high value products from biomass, there still remains residual biomass and the challenge is to use these waste streams in anaerobic digestion to at least recover some energy from it. But it is a challenge of course because if you extract compounds you maybe end up with lower degradable material which makes it harder to produce biogas, or some chemicals were added for the extraction which makes it more challenging not to kill all of the bacteria.

So, how much energy do you lose? Or how much is left?

That depends. Sometimes you get more energy out of it because it is possible, that through the extraction pretreatment you break open some of the organic structures and you get more energy from it than without the pretreatment, even when part of the organic matter is already removed. But sometimes you also lose 10-30% and in some severe cases (e.g. when toxic chemicals were used in the extraction process), the biogas potential drops to zero.

You also change the structure of the materials so if you for example start with a more or less dry material (which would be suitable for the Dranco technology) but during the extraction cascade water is added you end up with a more diluted substrate and so you need a higher reactor volume to treat the same amount of waste which makes it economically less feasible. So it is quite challenging but I think it is still the technology that we need to close the circle in the end towards a zero-waste-approach.

Ok, to sum it up: Biogas will play a relevant role in the future but the focus could be more interesting on the pretreatment of the resources or the biomass itself than it is kind of used for the biogas process.

Yes. At OWS historically we are focusing on municipal waste which is very heterogenous and in many countries people are now starting to build anaerobic digestion to replace composting so for the next 15-20 years the municipal waste treatment will grow rather than shrink.

But we want to do more than just produce biogas from waste streams. That is one reason for our participation in the Carboxylic acid production platform research. We are also experienced from these other projects where in most of them the focus is or was on converting waste to sugars and use these sugars for fermentation. Especially with heterogenous waste streams, the yields are often very low so with the carboxylic acid platform we believe that we can produce/extract more carbon in the form of carboxylic acids than only looking at sugars. The reason for the higher yields is that not only carbohydrates but also proteins and fats can be converted into carboxylic acids. That was also our focus in the former project VOLATILE. We looked at a combination with anaerobic digestion and carboxylic acid production which was a good starting point for CAFIPLA because after extracting carboxylic acids you end up with a press cake that still contains up to 50/70 % of the original mass which you can still use for anaerobic digestion. In VOLATILE we succeeded to getting more or less similar yields of biogas out of this streams. Of course, you lose 20/30% of your biogas potential by extracting carboxylic acids but it is promising that even existing digesters could run with the input after carboxylic acid extraction. So another big advantage is that you could use existing equipment, anaerobic digestion facilities (or) could just expand these plants with carboxylic acid production and extraction and use existing anaerobic digestion facilities to treat remaining material.

Looking at the projects OWS was working on – What are the accomplishments you are most proud of?

I am very proud of the VOLATILE project. Five years ago it was just an idea that we had at OWS arising from two different angles. The first spark arose from our participation in another EU funded project (TransBio) where it was observed that the sugar yield from agricultural waste streams were disappointingly low. And secondly, we know that the production of volatile fatty acids is something that is inherent to the biogas production process, and until then has always been regarded as a process failure when they started to build up in the reactor. We also know that volatile fatty acids are produced both from carbohydrates, proteins and fats (contrary to sugars which are only produced from carbohydrates). With this knowledge in mind, the premise of the VOLATILE project was to alter the AD process to optimize the volatile fatty acid production (which is quite a mindshift as so far we have done everything possible to minimize VFA build up) from heterogenous waste streams to provide an alternative carbon source for the bioeconomy (a VFA platform instead of a sugar platform).

 So that was when we sat together with Thomas Dietrich from tecnalia to work out the VOLATILE project and we can say it was quite successful as it is published on the European commission site as success story. So we are very proud of what we have achieved in the last five years and also with the follow up project CAFIPLA.

I am also proud that even in the COVID circumstances we were able to get a TRL 5 demonstration unit operational at Twence in the Netherlands last year in August where we produced the volatile fatty acids in a 5m³ scale together with the downstream processing with the centrifugation, membrane filtration cascade by tecnalia. Still a lot of things need to be optimised but at least we got a good starting point for CAFIPLA were we are gaining on these experiences.

Imagine you were giving a free wish – What is it that you would wish for current and future projects?

If I only had one wish I would wish for world peace of course.

But returning to the topic, I wish OWS will be able to continue to optimize the process and build on the good results we’ve obtained so far. You can have a good idea and write a good proposal but this doesn´t mean you will get the money to fulfil this. So, I really hope in the next years we can build on VOLATILE and CAFIPLA and that CAFIPLA is not the end of the story. I hope we can grow to technical scale and that in five or ten years we have the first industrial demonstration of the VFA technology close to one of our digesters so that we can produce in ton scale per years some carboxylic acids that are combined to some microbial protein by Avecom or bioplastic produced by Biotrend. It would be really nice that we can escape the lab and really make a process that has a market, and really have a future-proof technology alongside with our anaerobic digestion technology that we can use for a treatment of organic waste.

What would you recommend to somebody who wants to get to know more about the topic on the adaption of biogas digestion plants or on the extraction of carboxylic acids?

If they really want to know it in dept they should apply for a job at OWS because we are hiring. And follow us on newsletters, LinkedIn pages and Twitter. And for students look for a job in this sector. I have been there for 15 years and it is a very exciting sector! I’ve learnt a lot.

Thank you for your time Filip and your explanations.

Questions raised by DECHEMA e.V. (Lea König and Karoline Wowra, Dissemination manager of CAFIPLA project)

Image Source:  Adobe Stock: Header; OWS: profile picture