Related by context. Frequent words. (Click for all words.) 79 renewable fuels 77 biofuels 74 bio fuels 72 biofuel 69 biodiesel 67 renewable energy 66 ethanol 66 bio diesel 65 fossil fuels 64 cleaner burning 64 cellulosic ethanol 61 hydrogen fuel 61 hydrogen powered 60 renewable energies 59 flex fuel 58 switchgrass 58 renewable 58 fossil fuel 58 bioenergy 57 hybrid electric 57 renewables 56 fuels 54 biomass 54 diesel 54 compressed natural 54 zero emission 54 environmentally friendly 54 hydrogen 54 reduce carbon emissions 53 feedstocks 53 fuel 52 reduce greenhouse gas 51 Hydrogen 51 internal combustion engine 51 energy 50 Renewable energy 50 Biofuels 50 diesel fuel 50 hybrids 49 Biodiesel 49 gasoline 48 diesel engines 48 diesels 48 Ethanol 48 greener 48 carbon dioxide emissions 47 carbon capture 47 environmentally sustainable 47 Clean Energy 47 greenhouse gas emissions 46 Renewable 46 EVs 46 greenhouse gases 46 environmentally sound 46 carbon emissions 46 electric hybrid 46 diesel powered 46 emission reduction 46 greenhouse emissions 46 reducing greenhouse gas 45 wood chips 44 emissions 44 efficiency 44 technologies 44 environmentally conscious 43 CNG 43 greenhouse gas 43 feedstock 43 carbon emission 43 Alternative Energy 42 hybrid 42 coal 42 smart grid 42 Renewable Energy 42 eco friendly 42 environmental sustainability 42 automobiles 42 CO2 emissions 41 natural gas 41 GHG emissions 41 mass transit 41 petroleum 41 sustainable 41 Chevy Volt 41 Hybrids 41 biogas 41 Biomass 40 solar 40 vegetable oils 40 global warming 40 lithium ion batteries 40 sustainability 40 gas guzzlers 40 cellulose 40 environmentally responsible 40 Energy Efficiency 40 organic farming 40 gas guzzling 40 emission 40 diesel engine 40 solar thermal