Cellulosic ethanol is economically viable. The start up costs alone for the ethanol plants needed are very high. However, after the plants are built, Cullulosic ethanol is made out of raw materials and have been found to be extremely cost effective. Additionally, the amount of waste is very little and ethanol producers would actually pay plants to collect it.
Cellulosic ethanol is not economically viable, particularly without government subsidies. The abundance of oil reserves has made oil very cheap and hard for other sources of energy to compete with the price. Moreover, food based energy such as cellulosic ethanol raise the price of food and limit agricultural space which could cause food shortages.