We want better air quality in cities! To achieve this, we rely on the natural abilities of mosses and combine them with smart technology. This is complex and not always easy to understand. In the following, we answer the questions we have been asked most frequently in recent years and hope to make our approach easier to understand. If you have any further questions, please feel free to contact us at We also welcome your feedback.

In a Nutshell:

Green City Solutions, with its biotechnology that combines the capabilities of mosses with the latest Internet of Things technology, helps people in particularly polluted urban areas to get fresh air and thus more health and quality of life.

More detailed:

Innovative natural systems are the ideal complement to established urban greening. Where trees have no room to root and the care of green strips fails, Green City Solutions’ products offer a measurable and space-efficient improvement in quality of life and stay. The core product is an air filter and cooler based on moss. The biotechnology is more sustainable and energy-efficient than conventional systems with comparable performance. The products are developed and produced under Eco-Design guidelines, generate no excess waste, and are 99% recyclable. Their use contributes to three UN Sustainable Development Goals (SDGs): (3 – Good Health and Well-being; 11 – Sustainable Cities and Communities; 13 – Climate Action).

Climate change is one of the greatest challenges of our time. Rising temperatures and more extreme weather conditions are altering our familiar living conditions. Especially in cities, where heat lasts longer and is more intense, and heavy rainfall can quickly lead to flooding, affecting many people simultaneously due to high population density, these changes are noticeable. Intense wildfires and sandstorms contribute to additional air quality challenges. Worldwide, air pollution is already one of the major environmental problems, responsible for one in every seven deaths.

To mitigate the consequences of climate change, countries around the world have committed to environmental and climate protection. Regulations like the European Green Deal and increased public awareness are increasing pressure on decision-makers in businesses and cities to prioritize ESG (Environmental, Social, and Corporate Governance) and sustainability – often lacking transparent, measurable, and credible solutions.

According to the World Economic Forum, five out of the six largest risks to successful future economic activities are related to ecological factors, alongside mass destruction weapons.

Green City Solutions provides decision-makers with technology that offers local, transparent, and verifiable measures. These measures aim to provide fresh air to people in particularly polluted urban areas, promoting health and improving the quality of life.

When and where was GCS founded?

Green City Solutions was founded on March 25, 2014, by four students in Dresden after the four future founders first met in a project group in the summer of 2013.

How many employees does Green City Solutions GmbH have?

As of October 2023, Green City Solutions GmbH employs over 20 full-time employees, in addition to working students and interns.

Successful measures to combat air pollution often require long planning and implementation, making the process time-consuming for cities and businesses. Short-term implementable measures play a crucial role. Compared to a tree, Green City Solutions’ solution has an immediate effect and can be used on sealed surfaces. The local moss filter caretakers only need to ensure that the water tank is adequately filled. With the moss filter, cities and businesses contribute to sustainability and a healthy, livable city – visible and measurable.

The advantage is that the measure works locally and immediately, providing a high level of transparency and traceability. Performance reports regularly show the achieved performance parameters. The products also have respective environmental product declarations that assess the CO₂ footprint over the life cycle.


Contributing to “local urban climate improvement” is one of Green City Solutions’ goals. In this context, moss filters can contribute to biodiversity conservation in addition to air filtration and cooling. For example, CityTrees can be expanded with additional greenery, forming an essential component for increasing urban diversity.

Water Management:

Plants need water to remain permanently vital. However, increasing temperatures and prolonged periods of intense drought pose challenges. Rainfall tends to become more extreme, and heavy rainfalls in cities hit sealed surfaces that can absorb only minimal and slow water. Buffer solutions like cisterns and artificial basins can collect, store, and be used for cooling the city on hot days.

Especially the specialized mosses with active ventilation can achieve a noticeable temperature reduction due to their high evaporation performance.


Rainwater collected from roof surfaces and directed into storage, where moss modules are connected, actively evaporating water and cooling the air – this is how Green City Solutions envisions the best possible cycle and the concept of a sponge city. The additional greenery can be adequately supplied based on smart control and the type of planting.

10 CityTrees have a cooling capacity of up to 65,000 watts with approximately 500 watts of electrical power consumption. This is equivalent to about 810 newly planted street trees.

Mosses are believed to be the earliest land plants on our planet, estimated to be around 450 million years old. Therefore, it’s not surprising that there are approximately 16,000-20,000 different species, some of which even thrive in deserts within the Arctic Circle. This demonstrates exceptional robustness and adaptability. Mosses do not possess conductive roots; instead, they absorb nutrients and water through their entire surface. This surface of mosses is equipped with countless fine, sometimes closely spaced leaves, enabling up to a 30-fold enlargement of the actual base area – a principle of surface enlargement also known, for example, in lungs and alveoli. Substances dissolved in water thus penetrate directly into the cells and can be utilized. Furthermore, large amounts of moisture can be stored and evaporated on the leaf surface. This enables them to grow on stones and trees even without soil, hence they are also referred to as pioneer plants because they can take over initial colonization after natural and environmental disasters. Mosses also absorb climate- or health-damaging particles such as coarse and fine dust, soot, bacteria, and viruses, as well as gases like nitrogen oxides and CO₂. The biochemical processes behind this are not yet fully understood; there are indications, for example, that microorganisms symbiotically inhabit the surface of mosses and can convert and break down substances such as polycyclic aromatic hydrocarbons, which can then be absorbed by the mosses. These properties or natural abilities of mosses provide particularly suitable conditions for their use as a natural filtering medium.

The mosses are carefully selected based on criteria such as natural occurrence (climate), filtering capacity, growth rate, stress tolerance, and aesthetics. With around 20,000 different species, the selection process is crucial and a core competency of GCS. For research and development purposes, as well as the establishment of a healthy mother culture for self-propagation, we collaborate closely with the local nature conservation authority in regional nature conservation projects.

Mosses that migrate into specific natural habitats and displace species such as reindeer lichens (Cladonia rangiferina) can, under certain conditions, be harvested. Our knowledgeable colleagues oversee the harvest, ensuring that only designated mosses are ethically collected. These mosses are relocated to our moss farm, where they are assessed, tested, and propagated. We make sure to value each moss plant as a living organism, avoid losses, and give the organism the attention it deserves.

The mosses are cultivated in a dedicated greenhouse and grow soillessly on a special textile, each covering an area of about 0.5 m². Since this type of cultivation is rarely known and described for mosses, Green City Solutions has developed its own method with an optimized cultivation strategy that is continuously improved. As mosses in nature can take up to 48 months, depending on the species and weather, to grow a widespread and dense structure, controlled cultivation aims to accelerate growth while maintaining vital and robust plants. Through fully digitized control and monitoring, special water treatment and supply, new fertilizer compositions, and lighting and temperature control tailored to the mosses, the mosses grow up to 16 times faster than in nature. Additionally, year-round cultivation is possible. The current annual production quantity is about 2,000 moss mats.

The moss modules serve as the technical casing that enhances the natural abilities of mosses and maintains their vitality even under stressful conditions such as heat, drought, and intense air pollution.

To demonstrate measurable cleaning and cooling effects, it is necessary to actively draw in ambient air and pass it through the mosses, similar to technical filtration systems. However, the mosses must not dry out, as the absence of water would paralyze substance transport and transpiration force. Therefore, the moss module consists of a ventilation unit, an irrigation unit, and a control unit with sensors, enabling up to a 10-fold increase in filtering and evaporation performance while preserving the vitality of the mosses.

Extensive measurements have revealed that the moss modules can remove up to 82% of particles (particulate matter) from the air and generate over 800 watts of cooling power. The measurable distance of this effect depends on various factors such as wind direction and strength. The more modules in use, the greater the effective radius becomes.

We use treated rainwater. The water is filtered, cleaned, and the pH value is adjusted.

Mosses have a certain drought resistance that varies depending on the moss species. There are moss species that remain undamaged after a long period of drought. Other moss species, on the other hand, are damaged by brief drought. Our moss species can easily endure a day without irrigation. A failed or missing ventilation does not affect moss vitality. The ambient air is sufficient.

If sufficient light and a suitable light composition are present, the moss filter should work because all essential living conditions are guaranteed: water, light, carbon dioxide.

No, only the photosynthesis of the moss goes into a kind of hibernation at temperatures below 4 degrees Celsius. Even at temperatures below 0 degrees, ventilation can still be used, as fine particles still accumulate between the numerous millimeter-sized leaves of the moss. Unlike leafy plants that completely shut down their activity once the leaves fall off, moss shows activity throughout the year. Once temperatures rise above 4 degrees again, the moss’s activity automatically increases, and fine particles can be metabolized in the moss again. Therefore, the filtering performance remains relatively constant throughout the year.

This question is unfortunate – trees and mosses have coexisted for millions of years, providing valuable environmental services. Mosses and the fine particulate matter filtered by them even formed the basis for higher plants like trees. We support this symbiosis in the city. We see our products as a complement to trees, not as their replacement. Moss filters can contribute to supporting existing greenery by increasing humidity and moderating temperatures, reducing failure rates, for example. The key advantage of moss filters is that they can be deployed where trees face challenges. A healthy tree requires roughly as much root space as its crown size, a space that is scarce in the sealed city with its underground infrastructure of shafts, pipes, and cables. Moss filters can thus operate where there is insufficient space for sustainably healthy trees. So, the regular street tree and moss filters are not in competition but rather complement each other as solutions to different problems. A tree acts as a more long-term measure, while moss filters provide full performance immediately upon installation, offering short-term benefits as well.

Mosses can be used both outdoors and indoors, especially in places where air quality needs improvement. The cleansing and cooling effect is particularly valuable where there is a high concentration of heat and particulate matter, and where many people gather (must be). Consider, for example, heavily trafficked (shopping) streets and squares in city centers, schoolyards or kindergartens, as well as company premises, office or manufacturing workplaces, atriums, shopping centers, or train stations and airports. In these locations, moss filters can purify the air and create fresh air zones and meeting places for people.

Attempting to clean the air of an entire city would be impractical – billions of cubic meters of air move within seconds, and pollutants are transported from nearby and far away. There are many places in the city where air quality is fine, or where people don’t really gather. Importantly, looking towards the future, it is crucial to establish green corridors and recreational areas in cities that ensure fresh and clean air, strengthen biodiversity, and favor water management.

According to the Leibniz Institute for Economic Research, advertising displays in Germany consume as much electricity annually as nearly 40,000 two-person households. While this might not seem significant compared to the overall German energy consumption, it certainly offers potential for savings. We welcome the decision of the federal government to consciously control light advertising and avoid unnecessary displays, especially at night.

The CityBreeze consumes about 30% less electricity than a typical advertising display (Digital City Light Poster). Additionally, the CityBreeze is the first out-of-home solution that cools the ambient air instead of adding heat. It has been observed that blue spectrum light advertising attracts insects, which then hover around the light in a disoriented manner until exhaustion. The living moss on the back of the CityBreeze provides a refuge. Instead of weakening the essential role insects play in the ecosystem, the CityBreeze promotes more nature in the city, benefiting not only humans and the climate but ultimately also insects.

We aim to consciously utilize the existing infrastructure of displays in urban areas and gradually upgrade conventional pillars to incorporate the aspect of air purification and cooling.

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