A method of producing synthesis gas via gasification in a Fischer-Tropsch plant, the method including providing a number of gasifiers, the number of gasifiers provided being at least one more than the base number required to provide 100% plant capacity of synthesis gas when each gasifier is operated at 100% gasifier capacity. A method of continually producing synthesis gas via gasification of a carbonaceous feed in a Fischer-Tropsch plant by providing a number of gasifiers, the number of gasifiers provided being at least one more than the base number required to provide 100% plant capacity of synthesis gas when each gasifier is operated at 100% gasifier capacity; and adjusting the amount of synthesis gas produced by adjusting the number of online gasifiers, the flow rate of carbonaceous feed to each gasifier, or a combination thereof. A system for carrying out the method is also provided.