Which is a major drawback to the use of ethanol-based energy?

a. The use of ethanol is only efficient near rivers.

b. Ethanol creates toxic waste that must be stored forever.

c. Burning ethanol releases greenhouse gases.

d. Ethanol may run out in the next 100 years

Burning ethanol releases greenhouse gases. - c.

b. Ethanol creates toxic waste that must be stored forever

Explanation:

Although several technologies for potential improvements, especially for adding value to waste generated, were developed by researchers, the sugarcane ethanol industry has absorbed little of these innovations. Vinasse, one of the residues produced in sugar cane plants, is characterized as a nutrient-rich effluent. Vinasse has been applied mainly in fertigation practices, reducing water demand in the fields. Some studies, however, imply that such practices have negative long-term effects on soil and groundwater. The study in question warns of several potential solutions to reduce environmental risks that can, at the same time, generate other sources of income for the plants.