The answer is the same anywhere in the world for someone in this position: you would have to go out and find firewood. If you live in a war zone, you would be in grave danger. In Darfur, civilians looking for firewood are often very brutally attacked.
Reading over the articles of the Darfuri-run news organization Dabanga (based in the Netherlands with reporters on the ground in Darfur), you see report after report of such crimes committed by armed actors against civilians looking for firewood (go to www.dabangasudan.org ). But the people who go through these crimes could be self-sufficient if given half a chance; they know better than most people in the world which wild-growing plants around them to live off of, how to raise cattle, donkeys, goats, horses and camels, and also how to raise crops (sorghum, cauliflower, tomatoes, cucumbers, millet, corn to name a few things) in semidesert conditions in which flooding (during the rainy months of May through about October) is a common occurrence. They know how to budget and live on very, very little.
These people would not live on aid unless it were absolutely necessary.