BIO – FAÇADE 
The United Nations forecasts that 70% of the world’s population will be urbanized by 2050, which means there will be a marginal increase for new building and eventually a growth for the demand of a new city as the time progresses. As more than 50% of the world’s population resides in cities, there is a need to incorporate environmentally sustainable habitat. To deal with this in recent times there have been a significant use of green walls and green facades in construction of new building projects. Integrating plants and vegetation into various architectural features has been a new trend followed worldwide. The development of technology has encouraged countries to prioritize environmental problems in their policies. One of the notable ways in which sustainability can be achieved through architecture and urban planning is including nature as a model and using nature inspired strategies to cope up with environmental goals.
A well-established architectural design and [plan can improve the quality of life by declining energy consumption and reducing air pollution. Inspired by the concept of nature and the sustainability the elements provide the concept of bio façade was curated. These kind of facades enhances the energy efficiency of the structure while being nature driven. 
Bio façade cannot be defined as a single type or component of sustainable architecture as it is further categorized into water façade, green façade and micro algae façade. All these facades play different roles in urban spaces.

WATER FAÇADE: 
This particular system uses water to absorb air pollutants from the purification of air by rain. During rain, water droplets purify the air by absorbing pollutants by dissolving them in themselves. One of the disadvantage of this system though is the impossibility of implementing it in all climate and surroundings and a potential risk of materials being eroded by salt present in the water.

GREEN FAÇADE: 
One of the most popular façade used to absorb air pollution in cities by integrating plants in the building framework.

MICRO ALGAE FAÇADE:
Microalgae are the simplest form of plants and are mainly single celled, having a high ability to absorb and reduce co2. They produce approximately 75% of the oxygen needed by living creatures and have the potential to contribute to lower ecological and carbon footprint of buildings and fossil fuel depletion. They do not require a source of clean water for their growth and can grow in all aquatic habitats, they are believed to absorb most of their nutrients from waste water. Incorporation of microalgae with building faced turns the wall into photosynthetic surface, thereby enhancing the thermal performance of the building. The basic prerequisite of integrating this with a faced is a water storage tank.

It converts sunlight and carbon dioxide into oxygen, heat and biomass. Biomass is a sustainable energy source that can produce other forms of energy such as electricity, heat and biofuels. Biofuels are renewable and sustainable energy source. The advantage of biomass is that it can be flexibly used for power and heat generation and can be stored virtually with no energy loss.
Algae is grown in two different systems, first one is an open pond system in which algae is grown in outdoor ponds and collected, though being an economical system it comes with the challenge of unwanted external contaminants.
The second system is a closed system or PHOTOBIOREACTOR. in this system the surface volume ratio is the most important principle for large quantity of production, this improves the photosynthesis process. This system usually captivates the algae in tubes to avoid cross contamination.

“PHOTOBIOREACTOR” can be described as an enclosed, illuminated culture vessel designed for controlled biomass production that is closed to the environment having no exchange of gases and contaminants with the environment - As quoted by Singh and Sharma. PHOTOBIOREACTOR are closed systems working either outdoors or indoors, in which a single species is inoculated to keep a clean culture operation.
There are many photo bioreactors that have been developed and the closest model to algae façade system is a plate photo bioreactor.  Plates with different technical design are mounted to form a small layer of culture suspension, which provides an optimized light supply. A plate photo bioreactor is usually made of clear transparent glass, Plexiglas, polyethylene, clear polycarbonate with the thickness of panel not exceeding beyond 5 to 6 cm. Bioreactors produce part of the energy require by a building through biomass and can minimize excessive costs of energy. The required nutrients of microalgae can be supplied through the building's wastewater. After culturing microalgae in a bioreactor, maintaining it under a controlled temperature until the time of operation is crucial. The exploitation of microalgae (conversion of microalgae biomass into oil, electricity, or any other products) can be done both indoors and outdoors.
The plate bioreactor can contribute to the natural composition of the culture medium by emitting air bubbles at the bottom of the panel and preventing the accumulation of dissolved oxygen.
Bio façades can be integrated with various types of urban buildings such as office, commercial and residential buildings. Even these façades can be implanted in industrial buildings.

The integration of living microorganisms into the walls of the building enhances its aesthetic aspects. Bioreactors can create attractive and dynamic views that easily attract customers and minimize the cost of construction and system operation in their eyes. In April 2013, world's first building to be powered entirely by algae the IBA in Hamburg, Germany, a building with an integrated glass plate photo bioreactor facade, was commissioned. It uses live microalgae in glass louvres to generate renewable energy and provide shade at the same time. The façade absorbs heat from the sun to warm the buildings hot water tank, sunny weather promotes the growth of algae and provide more shade to the occupants