In Germany, an experimental building with a unique heating system was opened to the public.
It uses algae to generate heat and build up biomass, which is organic matter.
At the same time sunlight, which is not used by the algae, is converted into heat.
The building is part of the International Building Exhibition in Hamburg, a model in future urban housing.
Al Jazeera's Nick Spicer reports.
Source: Al Jazeera