Hello 2023!

Presenting to growers in Pijnacker-Nootdorp.

It’s been even longer, hasn’t it? I’m still here though.

Maybe I haven’t been blogging as much because as a researcher, the writer’s bandwidth I would have used here has been taken up by projects at work (and perhaps a certain lady as well…). Still, this evening I felt an itch to write a bit about what’s happened over the past year, and some plans for 2023 and beyond.

In short: projects, more projects, and a PhD position.

Circular Greenhouse Horticulture

2022 was the last year of the KB project on Circular Horticulture, led by Alexander Boedijn. I was given the opportunity to write my first journal paper, which was based on previous work done by colleagues to outline material flows in greenhouse horticulture. Getting an idea of (1) how much of each input is required, (2) how much of it ends up where and (3) how it ends up can help determine how to best integrate greenhouses into a circular economy. With the help of Alexander, Cecilia Stanghellini and others, the paper was published in the Journal of Cleaner Production.

The material flow diagram you may have seen before, with a few alterations after peer review.

Within the KB project, I was also put in charge of writing a white paper (not yet online) on a cross-over between mushroom production and greenhouse horticulture. We did some back-of-the-napkin calculations on exchanging CO2, ammonia and biomass between the two systems. There is quite some potential, at least quantitatively!

This wasn’t the only project on mushroom-greenhouse cross-overs. 2022 was the first year of a more detailed project looking at this: a collaboration with Renewi, grower BioVerbeek, mushroom grower Pilze-Nagy in Hungary, and Platform Tuinbouwreststromen, an organisation helping growers to valorise their by-products. I am working on a work package to model CO2 flows from the mushroom industry and see whether there is potential in using them in greenhouse horticulture.

I learned a lot about CO2 this year thanks to a ‘wildcard’ project for young researchers, which Luuk Graamans and I managed to get. This project was a literature study, with a few basic calculations, to answer broad questions on sustainable CO2 for greenhouse horticulture. As the world ditches fossil fuels, where will greenhouses get their CO2 from? Is there enough, what are the quality requirements, and how can it be distributed? We look into these questions in our report (nearly published – see poster here).

A visualisation of the difference between purity and concentration – two things we looked at for alternative CO2 sources.

Now for something much more practical: a project on using stems and leaves from vegetable crops to grow black soldier fly larvae. This was done with Wageningen Livestock Research, the Greenport West-Holland, and InsectoCycle. Working in a project with Seppe Salari and Jason Kiem after all those years of fantasising about indoor ecosystem agriculture felt like our wildest dreams becoming a reality. I spent a few fun afternoons putting tomato leaves through a juicer and storing the pulp in sealed plastic bags for InsectoCycle. These were included in the larvae’s diets and worked surprisingly well.

The other kind of ‘tomato juice’ (tough to clean as well!).

2022 was also the last year of the Club of 100 project on circular greenhouse horticulture. Led by Alexander Boedijn and informed by Club of 100 companies, we made an interactive PDF with various innovations contributing to circularity. The challenge was deciding how to place them within the Dutch government’s four strategies of ‘narrow the loop’, ‘slow the loop’, ‘close the loop’ and substitution of raw materials. Hopefully this will help give context to these terms and facilitate a common language for circularity within the industry.

The front page of the interactive PDF.

At the end of the year, I was asked to help out with a WUR report on biobased building materials, where I wrote a few paragraphs on greenhouse horticulture’s potential contribution. It’s relatively niche, but there is still plenty going on.

Other Projects in 2022

It’s incredible to see how circularity, something that was non-existent as a theme a few years ago, has so many projects running. I also had a couple of more general projects.

The first was for the 2030 Greenhouse in Bleiswijk, a greenhouse designed and built to showcase fossil-free growing. My task was to calculate and visualise energy consumption for the four compartments, growing strawberries, gerberas, freesias and anthuriums over the past 3 years. Very encouraging to see such a decrease in energy consumption!

The strawberry compartment in GREENHOUSE2030.

The second was for the KWIN – which stands for kwantitatieve informatie, or quantitative information. It’s a big book full of balance budgets for different greenhouse crops. What was the transport cost? How much energy went in? You’ll find all these numbers in the mighty KWIN. As the market is constantly changing, the KWIN needs regular updates. It’s been a very helpful way to get a better intuitive feeling for these numbers.


This is the last year of the project on calculating CO2 flows from mushroom production to greenhouse horticulture. I will be in touch with Pilze-Nagy to refine the initial calculations, which we can hopefully validate as well.

Other than that, two new projects started. The first is on peat alternatives. Peat is a material with excellent and unique properties, which makes it a popular growing medium. However, it is obtained by digging up peat bogs, which are an important carbon sink. This is why governments are starting to limit or even ban the use of peat, making alternatives necessary. This project, with Club of 100 members and co-funding from the government, will be about developing a mixing tool to help accelerate the search for alternatives.

There is also a new KB project on circular horticulture! This one will be about greenhouse horticulture’s role in a closed nutrient loop. We will be looking at various options and their associated trade-offs, before choosing one and diving into the details. This is to be done in a ‘living lab’ setting, involving stakeholders.


Writing an academic paper was definitely a highlight of 2022. My inactivity on this blog may have you think otherwise, but I really do enjoy writing. The peer-review process, whilst frustrating at times, is also a satisfying way to sharpen one’s ideas.

In the Netherlands, a PhD is essentially the result of writing four academic papers on a particular topic (along with some other activities). This means that, if my work produces papers, I could turn it into a PhD.

The first paper has been written. The second and third will come from the KB project (I am extremely grateful for the space Alexander Boedijn has given me to do this), leaving us with just the fourth. We have ideas, and hopefully they’ll become more concrete by that time.

Turning the process of writing papers into a PhD requires a promotor, a professor who formally promotes the candidate to a doctor. Finding a promotor on circular greenhouse horticulture was tricky, as it’s such a new topic. However, with my team leader Silke Hemming‘s help, I was blessed to find Martin van Ittersum from WUR’s Plant Production Systems group, who agreed to be my promotor in January this year. He was involved in forming WUR’s vision for a circular food system, with Imke de Boer. In fact, I’ve written about him here, in an article which ends in an uncanny foreshadowing. I can’t wait to work with him on the topic of finding greenhouse horticulture’s niche within the ecosystem.

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