Various methods and systems are provided for engine startup. In one example, a method for an engine includes injecting a fuel mixture with a proportion of a first fuel to a second fuel to decrease carbon emissions, in response to detection of or request for the engine to start. The proportion of the first fuel to the second fuel in the injected fuel mixture is decreased in response to engine speed reaching an idling speed. The first fuel may be a non-hydrocarbon-based fuel and the second fuel may be a hydrocarbon-based fuel.