A few weeks ago, I was at Alexander Boedijn‘s MSc thesis presentation. For the past year, Alexander has been looking at energy flows within Amsterdam and how they can be used in urban rooftop horticulture. 

After the presentation, a classmate and I discussed the topic of energy in indoor agriculture. One of the most noticeable challenges of indoor agriculture is its energy usage. Vertical farms under artificial lighting are the worst offenders. Even accounting for the difference in distance travelled, a head of lettuce produced in a vertical farm needs far more energy than its field-grown counterpart. Many companies present vertical farming as sustainable, yet the problem of energy demand is swept under the carpet. If we are to go ahead with vertical farming as a sustainable form of agriculture, this is something which will have to be addressed.

At the International Conference for Youth in Agriculture, Professor Josse De Baerdemaeker’s presentation highlighted that we are simply using energy – no matter the source – to produce biomass. How can we make this more efficient? Of course, ‘more efficient lighting and HVAC’ is the first thing that comes to mind. Also, we can make manufacturing and maintenance more sustainable. These are important parts of the solution. But what else is there? Here are three ideas I’ve recently come across.

Supply-based energy usage

Alexander Boedijn’s research involved identifying buildings where a rooftop greenhouse could be built. He also looked at energy flows within the urban environment, such as heat from hospitals, offices, and data centres. His research looked at the feasibility of such a setup.

The rooftop greenhouses in Alexander’s project would get their energy in a fundamentally different way compared to most current greenhouses. Rather being demand-based, the energy usage of these greenhouses is supply-based. They use whatever is available anyway. Energy is pushed, rather than pulled, from the environment to the greenhouse.

Mitigating the second law of thermodynamics

The second law of thermodynamics states that energy cannot be created or destroyed, only converted from one form to another. When I was at the AVF’s Brussels Workshop, I met a knowledgeable gentleman, Dave Lucas. He explained how growing different types of biomass can help mitigate the second law of thermodynamics, an idea of Jacque Fresco’s.

In every form of production – plants, fish, mushrooms, insects, and so on – there are waste products. These waste products contain energy. By throwing them away, or putting them on a compost heap, a lot of this energy gets released back into the environment as heat. This is the last thing we want. All that energy could be used more productively.

Ligninocellulose from tomato plants could be used to grow mushrooms. Chicken manure can be fed to worms and black soldier flies. Everything is food, waste products contain energy, and life can upcycle them. Energy losses cascade down. This, again, is already being practiced by The Plant in Chicago, a vertical farm mentioned in my previous post.

Flattening energy demand

The Plant has an ingenious way to control energy demand. Because artificially-lit vertical farms are independent of the lighting conditions outdoors, plants can be grown throughout the year. Not only that, but also during any time of the day. A vertical farm could be run during hours when energy demand on the grid is at its lowest.

The real genius behind The Plant’s lighting energy demand lies in the use of multiple timezones. By having more than one growing room, the lights can be on at different times. There are always lights on somewhere in the system, but not all lights are simultaneously on. The advantage of this is that The Plant no longer has a single peak of energy demand during the day. Using multiple timezones flattens energy demand. This is ideal, since The Plant aims to generate its own electricity. The average power requirement stays the same, but the maximum power of the generator can be halved.

These three ideas are connected in many ways. For example, Alexander Boedijn’s use of urban heat sources also mitigates the second law of thermodynamics, using energy before it leaks into the environment.