Related by context. Frequent words. (Click for all words.) 58 fossil fuels 56 biofuels 56 bio fuels 55 biodiesel 55 alternative fuels 55 feedstocks 54 synthetic fuels 54 fossil fuel 53 fuels 53 syngas 53 feedstock 53 natural gas 52 coal 52 biomass 52 biofuel 52 cleaner fuels 52 renewable 52 coal gasification 52 diesel fuel 50 bio diesel 50 hydrogen 50 cellulosic 50 renewable fuels 48 renewable energy 48 diesel 48 vegetable oils 48 petroleum 48 cellulosic ethanol 47 renewables 47 fuel 46 internal combustion engines 46 renewable energies 46 cleaner burning 46 ethanol 46 Biomass 46 photovoltaics 46 gasification 45 alternative energies 45 bioenergy 45 gasoline 45 bioethanol 44 crude oil 44 switchgrass 44 gas 44 Biofuel 43 hybrid electric 43 Biodiesel 43 biogas 43 wood pellets 43 Hydrogen 43 wood chips 43 electricity 43 liquefied gas 42 Renewable energy 42 diesel engines 42 compressed natural 42 methanol 42 PetroSA 42 hydrocarbon 42 liquefied natural gas 41 lignite 41 hydrocarbons 41 energy 41 burning fossil fuels 41 low sulfur diesel 41 bioplastics 41 petrochemicals 40 jatropha 40 internal combustion engine 40 Biofuels 40 cellulose 40 methane 40 polymers 40 carbon sequestration 40 IGCC 40 hydrogen fuel 40 combustion 40 naphtha 40 LNG 40 baseload 40 Sasol 40 carbon capture 40 photovoltaic 39 thermal coal 39 heating oil 39 oil 39 soda ash 39 Btu 39 Liquefied Natural Gas 39 refrigerants 39 Renewable 39 hydrogen powered 38 cogeneration 38 Natural gas 38 flex fuel 38 bitumen 38 boilers 38 anaerobic digestion 38 solar cells 38 cooking oils 38 Methanol