CO2 certificates have been around for some time, you can buy them and thus pay for your CO2 footprint or buy your way out of being allowed to emit a certain amount of CO2. Vertical farming CO2 certificates are therefore only a matter of time. In this article, I explain the problem, give an insight into where energy conversion losses occur, how this affects the profitability of a site, and my personal opinion on the matter.
What is Vertical Farming?
For readers of this blog who are not yet familiar with the topic of vertical farming, the Vertical Farming is the agricultural cultivation of plants in the vertical. In developed countries, this mainly takes place indoors. This allows you to grow much more on a small footprint, whereby the footprint is multiplied by the number of levels by using the vertical. This cultivation area can then be used. For weight reasons, hydroponics and the nutrient film technique are used, in which the plants are placed in small holders. To ensure that the plants get enough light, LED lighting is used nowadays, which accounts for the bulk of electricity consumption.
What are CO2 certificates?
CO2 certificates (Emissions trading) in certificates that guarantee an entity, i.e. a company or a private individual, the right to a certain amount of CO2 emissions. If you consume less CO2, you can in turn sell this certificate to others if they have higher CO2 emissions than expected. So you can use Trading CO2 certificates.
Vertical farming also causes CO2
Like almost every activity in the world where humans are involved, CO2 is released. In conventional agriculture, this is virtually the case with agricultural machinery, which runs on agricultural diesel, for example, and releases CO2 when burned. With vertical farming, things look a little different. For technical reasons, vertical farms are found indoors, where there are no agricultural machines that run on diesel, so these are not a source of CO2.
The source of CO2 is actually very obvious to anyone who is familiar with the technical side of things, because it is the energy consumption. And in a vertical farm, we consume a lot of electricity. That means, Vertical farming, as of 2023, cannot operate CO2-free from a technical perspective and on the basis of absolute figures, on an annual basis.
Because even if, depending on the country and region, more or less renewable energy is used, the CO2 footprint will still be immense. But why is that the case?
To understand this, you have to understand how photosynthesis works and why we have conversion losses, which lead to a different carbon footprint depending on the country and energy mix.
Excursion into photosynthesis and RuBisCO
The Photosynthesis is an ingenious process that nature has designed, with RuBisCO and the Calvin cyclethe biochemical process that takes place in the plant Chloroplasts takes place in order to produce energy (glucose) from the captured photons, the process is also responsible for our life on earth; without the waste product oxygen, there would be no chance of survival for the human organism.
Now RuBisCO with the Calvin cycle is ingenious in itself, but not particularly efficient, a kind of legacy product of nature, comparable to the technical quote: "if it works, don't touch it", so if it works, then you shouldn't touch it anymore. And nature has probably kept it that way for the last billion years, ever since plant life has existed.
As the Photosynthesis not very efficient is, not every photon is captured by sunlight or LED light in a vertical farm, which means that we can produce plants indoors, protected from the outside world, in incredibly clean and hygienic conditions that are enviable, but with relatively large energy losses.
Excursus in efficiency calculation
One example: We want to supply a vertical farm with solar energy, which is to be used purely for LED lighting in the basic assumption. We are not looking at how much light the plant needs, but how much light reaches the plant.
The division:
Solar cells, photovoltaic cells, PV modules etc., have an efficiency of between 15 and 22% for commercially available solar cells. Higher values can be achieved for solar cells in the laboratory under laboratory conditions (Status 2022 Fraunhofer ISE 47.6%).
Depending on the geographical location, the sun sends us an average of 1000 watts Solar output per square meter to the earth. At 20% efficiency, this corresponds to a power yield of 200 watts of electrically usable energy per square meter.
For the sake of simplicity, we will skip the battery and charge controller losses and go straight to the switching power supply.
A switching power supplyA highly efficient energy converter that can generate a regulated DC voltage from DC voltage, but also AC voltage, depending on the type, which can be lower or higher than the input voltage. In technical terms, we speak of SMPS (Switch Mode Power Supplies), with linear converters the excess energy would be released in the form of heat. Nevertheless, even SMPS do not have 100% efficiency in conversion and, minus self-consumption, have to make do with 85-90%.
With 200 watts that we receive from the solar module, we can utilize 180 watts with an SMPS efficiency of 90% for the LED lighting.
The LEDThis is used for lighting, but not just one, because plants are also somewhat picky about light, depending on which growth phase the plants are in, they need a different light mixture, red and blue LEDs are most relevant for photosynthesis, in recent years these have also made great progress, according to OSRAM increases efficiency to 61% become that blue LED at least on 45% (as of 2007) (There are other studies that indicate higher efficiency, but these are rather part of research and not commercially available, if so, please correct me via contact form).
By 2023, full-spectrum LEDs, which have the wavelengths of sunlight but are needed for plants, will be increasingly used.
We can therefore speak of 50% efficiency for the LEDs if the cooling of these is also implemented well, because Heat is what affects LED performance.
From the 180 watts of electrical power, we have to say goodbye to 90 watts of waste heat and 90 watts of light power, which are then radiated onto the plant.
And then there is photosynthesis itself, which, as already mentioned in the excursus on photosynthesis and RuBisCO, is very inefficient and this means that with normal sunlight we would have to be satisfied with 2% efficiency. However, since we are not working with sunlight, but with LEDs, which emit light within 400-700 nanometers and therefore work in the range that is relevant for plants and photosynthesis.
I used ChatGPT (GPT 4) to calculate the losses that occur during photosynthesis using the ChatGPT Python interpreter, with the premise that the conversion to glucose and cellular respiration, which are necessary for the plant, are not considered a loss:
The adjusted calculation of photosynthetic efficiency using LED light in the 400-700 nm range yields the following results:
Loss due to non-bioavailable photonsThis loss is completely eliminated with LED light in the 400-700 nm range.
- Loss: 0%
- Remaining light after this step: 100%
Loss due to incomplete absorptionSome photons are not completely absorbed.
- Loss: 30% (from 100%)
- Remaining light after this step: 70%
Loss due to energy conversion of the wavelengthsEnergy loss when adjusting the wavelengths.
- Loss: 24% (from 70%)
- Remaining light after this step: 53.2%
Since we no longer consider the conversion to glucose and cellular respiration to be losses, as they are necessary for plant growth, the Effective light utilization for photosynthesis 53.2%. This value represents the proportion of LED light that is effectively used by the plant for photosynthesis.
Of the 1000 watts per 1 square meter, the plant achieves only 47.88 watts after all direct losses in vertical farming, based on the photosynthetic efficiency calculation for vertical farming. This would give us a system efficiency of 4.78%
I think you should now be able to understand the facts about how big losses are. But let's get back to the CO2 issue, what do the losses have to do with CO2? In my opinion, the problem why the topic of CO2 and vertical farming is difficult is that people are trying to solve the problem in the wrong place.
Why does a vertical farm in France have a smaller CO2 footprint than a vertical farm in Germany?
Germany has so many renewable energies, but the problem lies in the fact that the Full load hours not so high over the year are. In Germany, the full load hours for solar energy are 10% (20% in the USA), for wind 16-57%. This means that they only produce energy when the sun is shining or the wind is blowing, and these are volatile, not constantly available. For example Grundremmingen nuclear power plantbefore the shutdown at the end of 2021, the full load hours were 85%.
The shutdown of the last nuclear power plants took place in April 2023, so on the one hand the base load stability was lost, on the other hand electricity now has to be generated by gas and coal-fired power generation, these already existed before, but are now increasingly responsible for the CO2 footprint and in the end are also reflected in the products, because these then have a higher CO2 footprint, measured in terms of the respective amount of energy for product quantity X.
France makes heavy use of nuclear power, but also has a greater cluster risk, as evidenced by outages in the past. However, due to the high proportion of low-CO2 electricity in France, from a climatic point of view, a vertical farm or products grown on a French vertical farm are significantly better than products from a German vertical farm.
In a post here on my blog, I already wrote my thoughts and calculations about the Vertical Farming Power Consumption to. 1800 kWh is needed for 100 kg of lettuce. Depending on which company tests and calculates (iFarm (no advertising), has a good listing), you get different values and therefore you can/must always calculate with your own LEDs and parameters.
According to my calculation from my previous article, the electricity consumption for 1 kg of lettuce was 18 kWh. If your calculation comes out with a higher electricity consumption per 1 kg of lettuce, these values will of course also be higher.
So 1kg of lettuce needs 18kWh.
per kWh generated in Germany in 2022, 434g CO2/kWh.
In the same period, France was at 73g CO2/kWh.
What does that mean?
18 kilowatt hours x {CO2 per kWh} = CO2 footprint for lettuce from a vertical farm
A German vertical farming salad would therefore produce 7.81 kg of CO2.
A French Vertical Farming salad, on the other hand, would only produce 1.31 kg of CO2.
These quantities relate to the CO2 share, which is only responsible for the electricity consumption of the LED lighting. This does not include cooling, logistics, storage and other control systems.
But I think we can clearly see that a French salad would be preferable from the point of view of climate-friendly production and food sourcing.
And so the reader of this article will probably already have an idea of what I think about CO2 certificates. And that brings us to my personal opinion.
My opinion
- These CO2 certificates are like selling indulgences; there is no control body that can say how much CO2 has actually been emitted. It is not possible to understand the pricing, nor can it be concluded that the money paid for them is also invested in climate measures and the amount of CO2 is offset.
- With rising CO2 prices, the costs for customers and consumers are also rising. Vertical farming is already not cheap today and would therefore reduce the customer base even further, as companies have to operate economically and have to pass on the costs of the CO2 certificates for the company to the customers in some form. Consequently, if customers want to purchase vertical farming products, they would have to import them via other companies abroad.
- Countries with a smaller carbon footprint in turn benefit from this and can better assert themselves, act in a truly competitive, economical and climate-friendly manner and also sell their products more cheaply and reach more customers due to the low CO2 content. This paralyzes your own economic development, while countries with less CO2 can grow better.
I hope I have been able to give the interested reader an exciting insight into this system and explain why I believe that CO2 certificates are not part of the solution.
If you have any questions, suggestions or ideas for improvement, please use the contact form or the comment function.
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