Scorching heat in town squares, stuffy attic apartments, flooding on the streets – climate change is now an undeniable presence in our towns and cities. Large, shady trees can help to mitigate the impact of rising temperatures, but what is the best way to keep them healthy and promote their growth in urban spaces? The Geisenheim project 'Black2GoGreen', led by Professor Claudia Kammann, focuses primarily on the use of biochar macadam urban tree substrates – mixtures of crushed rock, compost, and biochar – to help towns and cities adapt in the face of climate change.
Professor Kammann explains: “Just a few grams of biochar can have an internal surface area of hundreds of square meters, which means that it can bind organic pollutants and heavy metals very well, similar to activated carbon. It can also retain nutrients and make them available to plants, as well as store a lot of water due to its porosity.” Its use also functions as a climate protection measure, as biochar allows for the long-term storage of CO2 that has been removed from the atmosphere through the growth of the biomass used for production.
International Exchange
The biochar macadam substrates were developed in Stockholm and have so far only been used in Sweden, Austria, and Switzerland. Projects from these countries have impressively demonstrated the impact of this new construction method. At Hochschule Wädeswil in Zurich, for example, biochar is used specifically to guide the roots of urban trees, which opens up entirely new possibilities in underground spatial planning. Biochar also plays an important role in the 'sponge city' construction method, holding onto excess rainwater and allowing it to drain into underground, load-bearing gravel structures, a concept that the city of Graz has employed to cope with heavy rainfall.
In order to advance research into biochar substrates as quickly as possible, 'Black2GoGreen' aims to network scientists, manufacturers, and interested parties from all over the world. Kammann acknowledges how successful this approach was at the recent symposium: “We are delighted that there was so much interest and that the networking between pioneers and players in this important field was so successful. Our aim is to help break down barriers and address open questions so that more local authorities can take the first steps towards employing this construction method in their urban green spaces.”
The Future of the Project
Following the inspiring symposium at Hochschule Geisenheim University, the 'Black2GoGreen' research project is continuing apace. An online platform has been established (www.black2gogreen.de), which serves as an open source knowledge hub for biochar substrates. Regular online meetings are planned to deepen the dialog and adapt methods to new regions. Projects from partner cities are also to be given scientific support. The next major milestone is the conference in March 2025, which will focus on further innovations and developments in the field.
