Zero amount of Biomass on Mercury and high amount of Biomass on Mars.
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.
Terraforming
Biomass can start growing as soon as the requirements for plant life for temperature, pressure, water and oxygen are met. Sufficient biomass is necessary before a world can reach habitability and humans can live outside of habs 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 etc.
All population living outside of habs will consume biomass (unless you're playing with Biospheres). If you have a large population, keep a close eye on biomass, because the population may increase so fast that the biomass can't keep up, and they will all die. The game does not reduce your population to the point where your biomass sources balance the expenditure; all population outside habs would die instantly.
In order to prevent this from happening, you might consider building a Sky Farm satellite, which will make biomass and water levels irrelevant to habitability and make your population consume 0 biomass.
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.
A player may also choose to play using Biosphere instead of biomass.
Governors
The governors Zora Ikhwezi Michel, Yuna Freyja Song, Zhou Xi Wang-mu Lee and Rebecca Freyja O'Rourke have effects that can help your facilities produce biomass faster.
The governors Raj Ahmad Shah, Justus Black, Sofia Ishtar Batma and Rebecca Freyja O'Rourke have effects that reduce the amount of biomass consumed by the population in the city they are assigned to.
Buildings
Beginner Mode
| Building | Effects/level |
|---|---|
| Algae Colony | +4 |
| Kelp Forest | +15 |
| Coral Reef | +60 |
| Soil Farm | +2 |
| Grass Farm | +20 |
| Forest Stand | +50 |
Normal and Expert Mode
| Building | Effects/level |
|---|---|
| Algae Colony | +4 |
| Kelp Forest | +15 |
| Coral Reef | +60 |
| Soil Farm | +2 |
| Grass Farm | +20 |
| Forest Stand | +50 |
| Secondary | |
| Solar Shade | -10 |
| Orbital Mirror | -10 |
| Biofixture Lab | +5 |
| Kelp Farm | +10 |
| Comet Sling | -5 |
| Hab Dome | +5 |
| Transit Network | -5 |