When a company chooses to fund a project, it can do it in three key ways. It can raise equity capital by selling shares on the market, sometimes in a private way. It can borrow either internally from cash reserves by reinvesting profits or it could borrow from a lending institution or even issue bonds in the market.
The idea is that the cost of equity or debt (most projects have a mixture of both) should be representative of the risk within the project. The higher the risk the project has; the more volatile the earnings are likely to be and that will follow through with a larger beta factor as a consequence.