Biologist Tjaša Griessler Bulc: Circular cities could defy climate change

Researcher Griessler Bulc is mostly active in green technologies for reducing undesired effects on the environment and people. She believes the problems of cities today stem from the fact that they function in a linear way.

This means that a city needs drinking water, food and many other goods that need to be delivered there. The city then pollutes the drinking and rain water, uses the food and other resources and produces waste.

Anything that the city releases is very disrupting for the environment. In the context of climate change causing floods, drought and possibly food deficiency, Griessler Bulc wonders whether in the future drinking water will always be able to reach cities and whether enough food will always be available to satisfy the growing needs of inhabitants of global cities.

How to solve this problem? Cities must find a way to become self-sufficient, and Griessler Bulc presents the idea that in the future linear cities should embrace the concept of circular cities.

"Circular cities are so-called cities of the future. They are designed to defy all those factors brought about by climate change.

Circular cities are cities where water and solid matter that is delivered to the city or which the city produces would be processed and reused. Thus, water and other resources would circulate; virtually nothing would leave the city and less water and food would need to be delivered there."

Natural solutions in cities of the future

One element of circular cities can be natural solutions. "Natural solutions mimic the processes that have developed in nature in millions of years. We study this and use it for example for purifying water or increasing the quality of other bodies of water."

According to the biologist, plants can only grow in water if the water has nutrients. "Plants can absorb the nutrients from the water and integrate them into their own biomass. We can remove the biomass from the water and reuse it - for wood, weaving chairs, as a structural material or even to build houses. These are the origins of circulation."

"Natural solutions in circular cities can be plant-based cleaning systems, green walls, green roofs, parks with water, they can be urban farming areas that are essential for a circular city."

According to Griessel Bulc, green roofs in cities keep the rain water during heavy rains on roofs, thus preventing floods or heat, plant-based cleaning devices purify polluted water, while green roofs can clean up the grey water from bathrooms to the extent that it can be used to flush toilets, or wash a car.

By using other elements for certain purposes the demand for drinking water becomes lower and other sources of water that are available in the city can be used. Everyone with a garden can collect rainwater to water their plants.

In addition, creeks controlled by concrete channels in cities would be revitalised and they would be given the shape of their natural beds, pools would be created and sandbars planted with plants. Thus, water would again be able to purify itself while flood control measures would be adhered, although this can only be done if biodiversity is very high - if we "have different organisms that have their food chain in the water thus removing most harmful substances".

Humans should strive to mitigate climate change

Sustainable solutions have been recognised by many European cities and elsewhere around the world, according to professor Griessler Bulc. In London, for instance, where it has been established that the city would need 40 times more area to grow own food, calculations are already being made to see how many green roofs and urban gardens could be created in the city. Slovenia too is taking part in the EdiCitNet/Užitna mesta project with Šempeter pri Gorici being one of 11 cities in the world trying to find solutions to make global cities self-sufficient in terms of food.

In the case of Šempeter, there are attempts to introduce urban farming. "Gardening is popular in Slovenia, but the point of this project is not about producing vegetables. It is more about understanding what we need to have a garden, where nutrients and sufficient amount of water can be obtained, and which water is good for watering our plants. Of course this needs to be healthy water that contains enough nutrients. But these nutrients can also be taken away from the city and thus the circle is complete."

What should city gardeners be mindful of? According to Griessler Bulc, the water used by garden owners can be a health hazard. "A water that is clear is not always clean. It may contain many substances dangerous to humans. Thus, a garden owner must know what kind of water they use for their garden.

"In recent years, municipalities have increasingly been striving to make sure that healthy water is used to water gardens while users are encouraged to use natural nutrients." Gardens are typically used to grow enough to satisfy daily needs so one can afford sustainable production there. She also highlighted the social, educational and therapeutic roles of gardening.

Households - main source of pollution in cities

People still need to be aware of the fact that households are the main source of water pollution in cities and the fact that despite the sewage treatment being available, there are still a number of pollutants that remain in the water and thesy are only being detected. "They include, for example, antibiotics, various mutagens, carcinogenic substances, microplastics that is coming mainly out of washing machines ..." said the researcher.

Namely, water is a solvent. Everything that is thrown into it can dissolve in it, she said. This is the water that we then use to water our garden, so everything returns to our plate: "The more we will be aware of the fact that it is a circle the more careful we will be about what we throw away and where, and what we eat, because we cherish our health above all."

Griessler Bulc's research team has also been studying the use of human excrement and urine in agriculture. "If a person is healthy, their excrement is healthy too, which means that it can be used after proper treatment. Especially in cities."