Terms: Biofuels (19,400,000), biofuel (18,800,000),
Terms: biodiesel (21,500,000), bioethanol (1,380,000), biomass (24,500,000),
Terms: biofuel crops (408,000), biofuel from algae (20,000),
Boolean: biofuel +syngas (108,000), biofuel +methane (934,000), biofuel +microbes (300,000), biofuel +genetic (1,180,000),