Could your data center not just power your website, but also grow your salad?

Written by Tom Greenwood - June 1, 2021

I was recently introduced to Jeroen Burks, founder of a data center company called Blockheating based in the Netherlands. Chatting with Jeroen I quickly realised that he is working on something truly fascinating in the field of greener web hosting, with an innovative approach to combine data centers with agriculture. By the time you’ve finished reading this, you might never think of web hosting, or salad, in the same way again. If that sounds intriguing, then read on!

The beginnings 

It all began when Jeroen was an Applied Physics student at Delft University and began finding creative ways to recycle old computer hardware that was meant to be scrapped. In 2017 he started doing that on a larger scale to the point where Jeroen and his colleagues had 1MW of hardware, and realised that usually that amount of servers would run in a data center with air conditioning to keep it all cool. At the same time, he was asked if he knew an alternative method to heat a commercial building. 

Those two things came together and Jeroen led a project to install server racks in the basement of a building that was being renovated and use the waste heat to warm the offices. This was an exciting project, but when summer came and the offices got a bit too toasty, it became apparent that office buildings may not be the optimal place to implement this concept. Perhaps there was another application where the heating demands were more aligned with the “always on” nature of data centers.

A lot of hot air

In a normal data center, no matter how energy efficient it is, the waste heat is thrown out into the atmosphere. In Jeroen’s words “it keeps the pigeons from freezing in winter, and fries them in the summer”.

Jeroen realised that the traditional view of data center efficiency is highly misleading. It is normally measured using a metric called Power Usage Effectiveness (PUE), which measures the amount of energy used by the whole data center relative to the energy used by the servers themselves. A perfect PUE would be 1.0, meaning that no additional energy is used beyond the servers. 

“When cooling with aircons you typically have a PUE of around 1.2-1.5. There are however ways to “cheat” this. Adiabatic cooling (where water is evaporated) drastically lowers the PUE to <1.1, however good drinking water is used to get rid of the energy”. That in itself is a problem that is rarely talked about as the big data center companies keep water consumption figures secret.  

However, Jeroen points out a bigger issue with PUE, that it draws artificial system boundaries of where energy efficiency is measured, something that I have written about before. “For us there is no boundary. The datacenter should be the most efficient when looking at the full world view, in energy and materials. As long as the boundary is the perimeter of the Datacenter, then it’s totally different”. 

In other words, PUE as an efficiency metric takes for granted the fact that servers consume electricity and turn it into waste heat, so even a data center with a theoretical perfect PUE of 1.0 could be wasting huge amounts of energy and throwing it out into the atmosphere as heat. 

Turning up the heat

Inspired by his initial experiment in the office building and determined to find a solution to the issue of waste energy from data centers, Jeroen looked for places where heat is needed in a constant supply.

Being based in the Netherlands, the answer was right in front of him. Greenhouses!

The Netherlands is famous for its vast greenhouses growing crops such as tomatoes, peppers and cucumbers, but the Netherlands is not famous for its Mediterranean climate. 

Totmatoes growing in a commercial greenhouse

Salad crops such as tomatoes are often grown in vast, heated greenhouses

These greenhouses need to be kept warm. “They are all single glass, as sunlight is one of the main ingredients for these plants. This means that a lot of heat is lost, so they have a floor heating system that distributes warm air. Heat is produced by burning either natural gas or Biofuel, and is stored in a large buffer tank so that it can be distributed when it is needed.

Not all crops have the same temperature needs. These three are referred to as hot cultivated, meaning that the temperature can not drop below 17 degrees C, which means that even in the summer nights, there is a need for heating”.

Blockheating was born

Blockheating emerged from asking the question, “What would be the best way to integrate the ever growing demand for IT infrastructure in the real world”. The solution unites the problem of waste heat from data centers with the need for heat in commercial greenhouses. 

Instead of building large data centers on industrial parks, Blockheating builds small clusters of “mini” data centers distributed across farms and connected by fibre optic cables. Each cluster behaves together like a conventional, larger data center, but each small unit can be located directly next to the greenhouses that it will heat.

They use direct chip cooling of the servers, which means that water runs through the server to cool it down and then warm water is then pumped into the buffertank of the greenhouse. This allows the greenhouses to use their existing heating systems, but take the waste heat from the servers as their energy input instead of burning fuel. There are some heat losses through the data center walls and the cooling for routers, but around 95% of waste heat is fed back into the greenhouse.

It turns out that there is a lot of heat to recover! Jeroen told me that “in a typical datacenter, 5kW per rack is standard but we can go up to 27kW. For reference, 5kW is around 20 solar panels with a clear sky. In terms of computing power; a typical server with websites will use around 200-300 watts. With a whole data center of 9 racks we calculate around 180kW in total, which is enough to heat 20,000m2 of greenhouses in the summer and 5,000m2 in the winter. 1m2 will grow about 50 kg of tomatoes in a year”. Just nine server racks can grow hundreds of tonnes of tomatoes per year. That’s quite incredible.

In the process, the farmer gets very cheap heating provided without any additional CO2 emissions, and an extra source of heat to add to their resiliency.

Energy use is responsible for about 75% of the environmental impact of tomatoes grown under glass in the Netherlands, with carbon footprints ranging from about 0.78-2.0kg CO2e per kilogram of tomatoes. In other words, the emissions weigh as much as the food itself. By drastically reducing the amount of fuel burned to heat greenhouses, this new data center concept could also radically reduce the carbon footprint of some of our favourite foods.

A unique solution to green hosting

Blockheating has really captured my imagination as to what the next level of green web hosting and more sustainable agriculture could look like. It’s the first time I have seen a truly holistic perspective being applied to digital technology, and I find that very exciting.

The long term potential could be a full network of datacenters providing IT capacity where and when needed while providing a key role in local heating demands. Of course, this model works best in cooler climates such as the nordics, but northern countries are large markets for digital services and so this is still a huge opportunity.

Initially, you’re not going to be able to sign up to host an individual WordPress website with Blockheating as the business model is best suited to organisations with at least the need for a single server rack, and who have the skills to configure it to their own wishes (either internally or with partners). But perhaps it’s just a matter of time before someone decides to locate a larger WordPress hosting service on a farm in the Netherlands and grow some fresh salad on the side.

If you’re interested in learning more about innovative solutions to create greener digital services, check out other articles on our blog or read my book, Sustainable Web Design. And if you’d like to discuss a web project, drop us a line and say hi!

P.S. If you are curious about unusual, eco-friendly ways of growing tomatoes, check out my Climate Reality talk on “Eating sh*t tomatoes”.