Before your planet is ready to support a human population, you'll need to start seeding plant life and building a global ecosystem. Earth currently supports about 600.000 megatonnes of total biomass. As the biomass of your planet increases, you'll start to see more and more of the planet covered in lush green.
Biomass can start growing as soon as the habitability reaches PLANTLIFE. Sufficient biomass is necessary before a world can reach habitability and humans can live outside of habitations on the surface of a planet.
Biomass can increase through natural growth, but can also be added through the use of specific buildings, such as the Coral Reef, Kelp Forest, Soil Farm, Grass Farm, Forest Stand, and Algae Colony. A small amount is also produced as a side effect of the Biofixture Lab, Kelp Farm, and Habitation Dome. Coral Reefs generate thousands of space credits if you build many of them and population will increase. The amount of Biomass a planet can hold is dependent on its size:
Once the habitability is HABITABLE, population will consume biomass. To slow down the consumption, build more and more hab[itation] and biomass facilities. You will eventually have to build the Sky Farm satellite because you won't be able to keep the biomass increase higher than the decrease forever.
However, in Beginner mode, biomass consumption is not a thing as of the latest update. This makes Expert Mode biomass impossible to have a very high population (since you cannot afford the Sky Farm on that mode).
A player may also choose to play using Biosphere instead of biomass.
Earth has about 550 to 560 gigatonnes of biomass currently. It produces about 100 gigatonnes of biomass each year, but in the game, the biomass is about 750 Gt of biomass and decreasing for about -1000 per Earth minutes.
Bacteria will have less biomass than plants and animals do.