In a large pot, saute onion, carrots, and celery in a little olive oil until tender.
Add vegetable broth, water, sweet potato, basil, oregano, salt, pepper, tomatoes with juice, and beans. Bring to a boil, cover, and reduce heat to simmer for 30 minutes, or more.
Stir in spinach, and cook for another 10 minutes. Serve immediately.