Rendering plant

A Rendering Plant is located near The Rat's Nest residential neighborhood of Springfield.

History
When Homer and Marge were looking for a house to buy (while Marge was pregnant with Lisa), they worked with an agent from Stinking Fish Realty who showed them several houses. One of them was in excellent condition and located in a nice neighborhood, but as the agent made his presentation he had the living room drapes closed and held a handkerchief to his face as he talked. Marge noticed a stench, became suspicious and opened the drapes, revealing the rendering plant. The agent tried to make light of the situation ("Once you get used to the smell of melted hog fat, you'll wonder how you ever did without it"), but Marge was unimpressed and the Simpsons kept looking, even though Homer liked the smell.

Immediately after the Simpsons saw the house, Homer went into the rendering plant and looked at the processing area, his face pressed to the glass as he watched two workers moving containers of fat around. The workers had their backs to Homer, but just after he started watching them, one of the workers paused in his task and asked the other if he smelled something.