Final answer:
Cellulosic ethanol is produced from plants containing cellulose. Humans cannot metabolize cellulose as a source of glucose due to the lack of enzymes in our digestive system.
Step-by-step explanation:
Cellulosic ethanol is ethanol produced from any plant containing cellulose. Cellulose is a structural polymer of glucose units found in plants.
Cellulose can be broken down into sugars that can be fermented to produce cellulosic ethanol. This process involves pretreatment of biomass for biofuel production.
Humans are unable to metabolize cellulose as a source of glucose because our digestive juices lack enzymes that can hydrolyze the ß-glycosidic linkages found in cellulose.