Project start: 01.07.2023
Project end: 30.06.2026
Sponsor: Bundesministerium für Umwelt, Naturschutz und nukleare Sicherheit
The preservation and planting of urban green, especially trees, play a crucial role in the adaptation of cities to global heating, as they provide natural cooling. Larger trees transpire up to 500 litres of water per day. Shade and evaporative cooling reduce the effect of urban heat islands. However, road salt, soil compaction and pollutants stress urban trees. Heat and drought intensify, so that new plantings often fail to grow and existing trees increasingly die before they reach a size that has an impact on the city's climate. Alternative tree substrates could provide a remedy, and also improve the infiltration of water from heavy rainfall events. One promising approach are biochar macadam substrates (PMS), i.e. defined mixtures of rock gravel, plant charcoal and compost. After compaction, the crushed stone results in a passable but pore-rich structure that creates space and aaeration for root growth and which are capable of absorbing high levels of precipitation. The production of the biochar also locks up biomass carbon over decades to millennia (=carbon sinks, i.e. carbon (dioxide) removal). PMS were developed in Stockholm and are so far only used in Sweden, Austria and Switzerland. The goal of "Black2GoGreen" is to create a network of municipalities, municipal enterprises, associations as well as manufacturers of biochar and biochar (tree, green-roof) substrates to transfer knowledge about already implemented solutions to Germany.