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