Project AbifFa - Algae biofilm facades for cleaner air and improved urban climate

04/10/2022

• Challenge
• Objectives
• Methods
• Partners

The aim of the research project is to develop a concrete substrate that allows the establishment of an extensive and permanent biofilm on façades while ensuring it remains protected under different weather conditions. The aim of the project is not only to include aesthetic aspects of the façade but also to make a significant contribution for removing air pollutants in inner-city areas. Furthermore, it is expected that the novel facade greening can increase biodiversity and dampen the heat-island effect.

Main quantitative and qualitative objectives of this project, which would be achieved through interdisciplinary research, are: • Measuring metabolization efficiency of the new algal façade • Measuring the uptake of CO2 and NO2 under different climatic conditions • Measuring the uptake and mineralisation of particulate • Measuring potential evaporative cooling • Increasing species diversity in the anthropogenic habitat • Reducing construction and maintenance cost • Increasing visual attractiveness of concrete façade by applying green algal biofilm.

Both quantitative and qualitative methods are used to study algal facades. First, algae strains are investigated to identify the most adaptable one which can grow dominantly on the surface of a concrete panel and resist against harsh characteristics of the substrate and environmental factors. Simultaneously concrete mix designs and surface characteristics are studied to increase compatibility between both substrate and biofilm. Using weathering stands, a comparative study will be performed. Concrete panels covered by algal biofilm are evaluated for their visual appearance.

For this research project BAM division Building Materials collaborates with the research group "Model Biofilms and Geomycology" of the Department Materials and the Environment of BAM. Other partners include Solaga, a Berlin based startup, and a precast concrete manufacturer, BNB from Potsdam. At the end of the project the chair of social and health care buildings and design of the Technical University of Dresden will conduct an aesthetic evaluation of the façade samples in a workshop with architects.

Algae biofilm facades

Inner-city air pollution and the increasing impact of the "heat-island effect" due to climate change have long been identified as key problems in large cities and reduce quality of life and health of residents significantly. According to the European Environment Agency, around 90% of the urban population in the EU is exposed to concentrations of particulate matter, nitrogen oxides, and ground-level ozone which have health-threatening effects. Long-term or transient exposures can cause a range of symptoms from respiratory illnesses to premature death and even lead to premature births. Vertical gardens require high level of maintenance costs and intensive gardening. Therefore, it is important to find a bio-inspired alternative solution which can provide similar or superior values while needs less maintenance and consequently lower maintenance cost.

State of scientific knowledge

Different researchers have tried to find new bio-inspired solutions to mitigate the impact of concrete construction on climate change and global warming. For instance, establishment of moss on facade panels has already been assessed in various projects. However, mosses are not tolerant enough to climatic conditions and currently a research project "Moostex" has the aim to test additional moss species as well as different irrigation systems. Biofilms are easier to maintain and more tolerant of air pollution in comparison with mosses. Algae has been used for biomass production in a building in Hamburg for the first time, but it was based on installing glass panels containing algae and water on the building façade. Direct application of algae on concrete surface is a novel idea and only a limited number of researchers have studied it. Therefore, there are still key questions which need to be answered such as:

• How should initial biofilm be composed and stabilised to ensure long-term stability and visual appearance?
• Which concrete mix design and microstructure as well as which wetting behaviour favoures the attachment and uniform spreading of the microorganisms?
• What application method favoures rapid establishment of the biofilm on the facade?
• How must the demand-controlled irrigation and the supply of trace elements be designed to enable optimal growth and persistence?
• What is the contribution of façade systems to the metabolism of air pollutants especially CO2, NO2?
• What is the contribution of façade elements to the reduction of surface temperature after solar radiation and to the retention of precipitation water?
• How is the aesthetic impression assessed and how can the new elements be integrated architecturally?

This research will provide comprehensive answers to these questions.

Testing and measurements

This interdisciplinary research project is divided into five work packages. The first work package includes the design and manufacture of the test specimens. BAM division Building Materials will determine the chemical composition of the substrate as well as the attachment conditions and the water availability for the microorganisms which will be optimised. To ensure that product development is in align with the industry requirements, BNB which is a precast concrete manufacturer gets involved in the conception phase. BAM department Materials and Environment together with a small startup company named Solaga are responsible to select and characterise targeted microorganisms. The second work package comprises the execution of the laboratory test. As soon as the first substrates with biofilm are available, they are to be artificially weathered under defined conditions. BAM department Materials and Environment and Solaga will determine the species composition and quantify the biomass and the potential for uptake of CO2 and NO2 over time, while BAM department Safety of Structures will analyse the occupation density and the corrosive potential. The core of the third work package is the performance of outdoor weathering experiments, with regard to planned work in the second work package. In addition, systems for irrigation will be tested and the evaporation capacity will be recorded under real climatic conditions. Also, the metabolism of particulate matter over time can only be analysed under real conditions for reasons of representativeness. The core of the fourth work package is the upscaling of the most promising set-up, which is supported by the company BNB. In the fifth work package, aesthetic aspects of concrete panels covered by the algal biofilm will be evaluated in a design workshop conceived by the chair of social and health care buildings and design of the TU Dresden.

Project management

Bundesanstalt für Materialforschung und -prüfung (BAM) Building Materials division

Project partners

Bundesanstalt für Materialforschung und -prüfung (BAM) with
BAM's Building Materials division and
BAM's Materials and Environment department
Solaga UG
BNB-Potsdam GmbH
TU Dresden

Financial support

The project is funded by the Zukunft Bau programme of the Federal Ministry of Housing, Urban Development and Construction.