Photobioreactor Facades: When Algal Shells Transform Our Buildings

project1253
3 hours ago
4 min read

Facades are no longer simple inert walls: they are becoming interfaces capable of interacting with the environment. It is within this dynamic that photobioreactor facades (PBR) are being developed, where microalgae transform light, absorb CO₂ and produce oxygen, while also giving urban envelopes a new visual identity.

A photobioreactor is a closed system allowing the cultivation of photosynthetic microorganisms under controlled conditions. Integrated into a building, it becomes a functional element that contributes to energy sustainability and to the aesthetics of the envelope.

A recent project presented by Xiujin Liu (2025) describes modular facades made of neutralizing algal bricks. These prefabricated modules, easy to transport and assemble, integrate an air circuit and a culture system. The major innovation lies in AI monitoring, thanks to a monocular camera that monitors in real time the health of the algae and signals their replacement when their efficiency decreases [1].

The Multiple Benefits of Photobioreactor Facades

PBRs are not limited to a single function, but bring a set of tangible advantages:

Sequestration of CO₂ and production of oxygen: microalgae directly absorb urban CO₂ and release oxygen, transforming facades into real natural filters].An algal façade can absorb up to 770 kg of CO₂ per year,the equivalent of 35 trees, while producing oxygen.[6]

Energy efficiency and thermal comfort: by creating dynamic shading, facades reduce the thermal load of buildings, provide acoustic insulation and contribute to the regulation of indoor temperature .It cools interiors by 2 to 4 °C and reduces air-conditioning needs by 20 to 30%.[7]

Production of biomass: algal biomass can be used to produce biofuels, bioplastics or other value-added materials. It generates around 4,500 kWh of biomass per year, equivalent to a household’s electricity use, which can be turned into green energy or materials. [8]

Aesthetic and cultural dimension: certain installations, such as the Photo.Synth.Etica biocurtain, illustrate the visual and artistic role of PBRs. This structure is capable of capturing 1 kg of CO₂ per day, the equivalent of 20 trees, while offering a spectacular architectural presence in the urban space [9].

These combined benefits draw the image of a living facade that goes beyond its simple function as a wall to become an active ecological actor.

Concrete and Inspiring Case Studies

To understand the potential of these facades, it is essential to look at examples already carried out or studied.

One of the most emblematic is the BIQ House in Hamburg, inaugurated in 2013 and considered as the first building in the world equipped with a PBR facade. This living envelope covers about 200 m² and generates 4,500 kWh each year, more than the average consumption of a German household. In addition to producing energy, the panels provide natural shading, reducing overheating, and illustrate the possibility of integrating innovation into modular residential housing [2][3].

A second interesting case comes from a study published in Frontiers (2025), which tested an algal window integrating two strains: Chlorella and Chlorococcum. The results show a daily production of biomass confirming the capacity of facades to capture carbon in a measurable way and to produce valuable resources [4].

Finally, research (ResearchGate, 2024) carried out in a temperate climate estimated that PBR panels could sequester between 84.87 kg and 770.13 kg of CO₂ per year. Although the return on investment remains long, these results confirm the relevance of the system in a context of energy transition [5].

The Obstacles of an Emerging Innovation

If photobioreactor facades nourish great hopes, their large-scale deployment still encounters complex realities.

The first obstacle is financial: recent studies estimate that the initial investment is only compensated after 16 to 24 years, a long delay in a sector where rapid returns are favored [5].

Next comes the question of cultivation conditions. Algae are sensitive to light and temperature and require constant monitoring. The most advanced solutions, such as those developed with monitoring assisted by AI, attempt to respond to this requirement of real-time tracking [1][4].

Finally, there is still a lack of a solid regulatory framework. Without clear standards on safety, maintenance and integration in different climates, it is difficult to imagine a massive adoption of these technologies [10].

These obstacles do not cancel out the potential of the sector, but show that the road towards algal facades becoming common in our cities goes through joint work between researchers, architects and institutions.

Conclusion

The perspectives offered by PBR facades open the way to a new generation of hybrid buildings. The approach of Xiujin Liu, which combines modular bricks and AI monitoring, makes it possible to facilitate maintenance and deployment, making algal facades more accessible and scalable [1].

Beyond their depollution function, these systems could contribute to the valorization of the biomasses produced, used in circular sectors such as biofuels or bio-based materials. In this vision, buildings are no longer simple energy consumers, but become living organisms capable of producing, filtering and regulating.

The BIQ House, the experimental windows of Frontiers or again the artistic projects such as Photo.Synth.Etica demonstrate that PBRs are not science fiction. They are already here, and even if they still require technical and economic improvements, they embody a concrete step towards cities that breathe with us.