Your homegrown zucchini from the balcony is less sustainable than the conventional zucchini from the supermarket. Surprised? We were too! But that is the conclusion of an international study, the first to compare the carbon footprints of home-grown and farmed produce. Still, researchers say urban gardening is just as important – But it needs to be made more sustainable. So, let’s take a look at how that can be done!
The urban farming study
The study compared the fruit and vegetable production of 73 urban gardens in the United States, France, Germany, Poland, and the United Kingdom. It involved the Dortmund Institute for Urban and Regional Development Research and the University of Michigan’s School for Environment and Sustainability.
The urban farmers recorded exactly what they bought and how much they harvested. The scientists then compared this to a ” shopping basket” of popular supermarket fruits and vegetables grown conventionally in the region.
Result: Conventional agriculture produces six times less CO2
Well? Are you as surprised as we were? The explanation is actually quite simple: conventional agriculture, with its fields, greenhouses, and truck delivery chains, is more efficient (in the grand scheme of things) and thus produces fewer emissions than urban gardeners who grow a few raised beds in their backyards for personal use.
A simple example: Imagine you want to grow zucchini on your patio. You go to the hardware store and garden center, buy wood, soil, fertilizer, a watering can, zucchini seeds or seedlings, and always irrigate with water from the tap. In the end, you harvest 30 zucchini. If you now calculate the total CO2 emissions caused by a single zucchini, you can easily imagine that professional agriculture, which has already optimized its processes for the highest possible yields, has a smaller footprint. Of course, you’re not building a new raised bed or replacing all the soil every year, but we’ll get back to that!
The good news: Tomatoes from the balcony are better than those from the greenhouse!
Should you throw in the rake now? No. What you can do is plant tomatoes. They are one of the few vegetables that have a lower carbon footprint (compared to greenhouse tomatoes!). And there are other things you can do.
The 3 biggest urban gardening mistakes and how to avoid them
Before we get to the benefits of urban gardening and urban farming for urban development, let’s take a look at what we’re doing wrong and what we could be doing better. After all, 17 of the 73 gardens studied were more climate-friendly than conventional agriculture, so researchers have some clues about what makes ecological sense and what is counterproductive. Here are the most common mistakes and, of course, their solutions:
#1 Too short period of use
The authors of the study saw a problem in the fact that many urban garden projects exist for a short period of time (such as five years). This means that all materials purchased (raised beds, etc.) must be calculated for that time period.
Possible solutions:
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- Use your new raised bed as long as possible, pass it on to the next tenant, or sell it to other urban gardeners when you no longer need it. In this way, you can extend its lifespan.
- Build your raised bed from upcycled materials, such as old pallets or scrap lumber, and use topsoil excavated from other construction projects.
- Buy second hand. Whether it’s a raised bed, a planter, plants or even soil.
#2 Incorrect composting
Most urban gardeners use compost, which saves them 95 percent of the mineral fertilizer they would otherwise use. This sounds great, but unfortunately the researchers found that about 30 percent of the gardens they studied had improper composting techniques with inadequate air circulation, leading to methane emissions. Methane is a more powerful greenhouse gas than CO2. Learn how to avoid methane in your compost in this article on composting mistakes.
Possible solutions:
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- Make sure your soil is loose, especially during the winter when it can become very compact. Loosen it thoroughly in the spring.
- Learn about composting techniques. Perhaps a different technique would be more appropriate for your balcony (e.g. bokashi, worm bin, etc.).
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#3 Irrigation with drinking water
About 50 percent of urban gardeners use rainwater occasionally, but only five percent use it exclusively. Instead, 95 percent of watering is done primarily with drinking water from the tap or pumped well water.
Possible solutions:
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- Admittedly, the solutions here are limited. After all, not everyone can put a rain barrel on their balcony. But if you have the option, you should consider it!
- Alternatively, if rain is in the forecast, place bowls and buckets on the balcony to collect the water so you can use it to water your plants for at least the next few days.
- Another option is to collect gray water in your household. For example, when you rinse vegetables, cooking water from potatoes, eggs, etc., water you leave running in the shower until the hot water comes, etc..
Benefits of urban gardening and urban farming
Agriculture belongs in the countryside. This is how the study could be interpreted. Still, it makes sense to make cities greener – especially in times of global warming and rapid population growth. This is what the study says. Here are the key benefits:
- Trees and other vegetation in the city trap particulate matter and pollutants.
- All plants that use photosynthesis bind CO2. The total amount depends on the mass of the plant, which is why the effect of your tomato plant is much smaller than that of a larch. But in the spirit of “many small things make a big difference”, small gardens also absorb CO2.
- Plants produce oxygen, improving air quality.
- Urban gardens provide shade to cool streets and homes. This in turn reduces the energy consumption of air conditioners.
- Urban gardens encourage biodiversity. They provide food, habitat and shelter for insects, birds, hedgehogs, lizards and other small animals.
- Promote well-being: Many studies have shown that children, teens and adults feel good and happy in nature. Green facades and bright flower beds are pleasing to the eye.
- Mental health for urban gardeners: The carbon footprint study mentioned above found that participants experienced positive effects on their mental well-being. This was revealed in interviews with the managers of the 73 urban gardens and, according to the researchers, is a factor that should not be ignored.
- Freshness of food: For those who grow fruits and vegetables, freshness is often an argument in favor of organic farming – everything is allowed to ripen and be eaten right away.
- Growing your own food promotes education and appreciation. You (and especially children) learn how fruits and vegetables grow, how long it takes, and what it takes to finally harvest something.
Three exemplary urban gardening projects from our Green PearlsⓇ hotel partners
#1 Hotel Milano Scala – Milan’s first zero-emissions hotel
As a major industrial city, Milan is not necessarily “green,” but the city is famous for many innovations – not only in fashion and design, but also in urban development and urban gardening.
The two “Bosco Verticale” (Vertical Forests) skyscrapers built ten years ago by Milanese architect Stefano Boeri are particularly famous in this context. They were his first attempt to bring the forest into the city. Since then, Boeri has built other such buildings (including in Mexico).
“And then if you observe what is urban, cities occupy not more than 3 % of the surface of the major lands of the planet, but this 3 % produces basically 70 % of the CO2, which is bad for the atmosphere.” – Architect Stefano Boeri interviewed by Forbes
In addition to Bosco Verticale, Hotel Milano Scala deserves your attention. It is the first zero-emissions hotel in Milan and is powered by green energy. The centrally located hotel is also committed to greening the city. Standing in the lobby, you can look through a glass roof onto the green facades of the courtyard and up to the lush roof garden, whose fruits can be enjoyed in cocktails at the rooftop bar and restaurant.
- By the way, Milan has a train station that is well worth a visit and is environmentally friendly to reach by train. Read more about this in our blog: Italy by train.
#2 Green City Hotel VAUBAN – an example of green urban development
The German city of Freiburg not only has the most hours of sunshine in Germany, it also has a relaxed, modern and “green” atmosphere. At least in the relatively new Vauban district!
Created in 2006 from a former military area, the district is virtually car-free (except for occasional delivery traffic). Instead, there is an excellent network of cycle paths and direct access to public transport. Vauban is also a real recreational area with green belts, parks and urban gardening.
A highlight of this overall concept is the Green City Hotel VAUBAN. Not only does it have a green façade and green balconies, but the integrative establishment also assumes ecological and social responsibility in all areas of the hotel business.
- Sustainable travel in Freiburg:Sustainable exploration in Freiburg: In our blog post on sustainable city trips, Katharina from the Green City Hotel VAUBAN gives some tips on how to spend your free time (as well as the best cheesecake in town).
#3 Hotel Luise has created a microforest in Erlangen
Hotel Luise, now run by the third generation of eco-pioneer Ben Förtsch, is committed to improving the microclimate of Erlangen on several levels.
A real tree grows at the top of the roof terrace. But Ben’s pet project is his “microforest”. Thanks to precise planning (e.g. root symbiosis with mushrooms), the microforest at the Hotel Luise will have the same characteristics as a 100-year-old forest in just ten years. And this in the middle of the Bavarian city!
In addition to the value to biodiversity, the hotel benefits from the plantings in very practical ways: they provide shade (passive cooling), noise reduction, natural air filtration, and many songbirds.
Conclusion
The value of urban gardening cannot be measured by the carbon footprint of a single zucchini. However, we should not ignore the problems and the resulting suggestions for improvement to make our urban gardens do even more good!
Planning your own urban garden? Then save this article for later!
