For example, systems can use feedstock materials, such as cellulosic and lignocellulosic materials and starchy or sugary materials, to produce ethanol and {HEAD ~ butanol}, e.g., by {TAIL ~ fermentation} 
For example , systems can use feedstock materials , such as cellulosic and lignocellulosic materials and starchy or sugary materials , to produce ethanol and { HEAD ~ butanol } , e.g. , by { TAIL ~ fermentation }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL