A fuel bin was a storage receptacle for fuel.
In the 23rd century, the Delta-Vega Station was equipped with fuel bins. In 2265, while establishing a holding cell for Gary Mitchell at the station, Lieutenant Lee Kelso was worried that if the bypass wasn't managed properly, the bins might explode. Later, Captain James T. Kirk asked Kelso if the fuel bins could be set for self-destruction. He said that it was possible with the self-destruct switch being located in the control room. (TOS: "Where No Man Has Gone Before")