Renewable energy is the energy that can be replenished easily. For years we have been using sources such as wood, sun, water, etc. for means for producing energy. Energy that can be produced by natural objects like sun, wind, etc. is considered to be renewable. Technologies that have been in usage include wind power, hydropower, solar energy, geothermal energy, and biomass/bioenergy.
Water purification: The whole idea/concept of having dirt/germ/pollution free water flowing throughout the environment. Many other phenomena lead from this concept of purification of water. Water pollution is the main enemy of this concept, and various campaigns and activists have been organized around the world to help purify water.
Air purification: Basic and common green plants can be grown indoors to keep the air fresh because all plants remove CO2 and convert it into oxygen. The best examples are: Dypsis lutescens, Sansevieria trifasciata, and Epipremnum aureum. Besides using the plants themselves, some species of bacteria can also be added to the leaves of these plants to help remove toxic gases, such as toluene.

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