In a food processor with the grater attached, shred carrots and celery. Mince garlic and set aside.
In a large (3-4 gallon) stock pot, cook sausage until no longer pink. Do not drain the fat! Add carrots and celery and saute for 3 minutes. Add garlic for last 30 seconds of cooking.
Reduce heat to a low simmer or change to the [slow cook] setting on the Instant Pot. Simmer for 4 hours.
Serve 1/2 cup sugo over 1 cup cooked spaghetti noodles for 32 servings. Or freeze both sauce and noodles in gallon freezer bags for a meal or two later.
Notes
Depending on whether the canned sauce you are using has salt added or not will determine how much salt to add to your sugo. If you are using "no salt added" sauce, I suggest adding 2 teaspoons of salt before letting the mixture simmer. If it still needs more, add 1/2 teaspoon at a time until you reach desired flavor.Pro tip: mix 1-2 cups of marinara with cooked pasta to serve. This prevents pasta from sticking.