of University California, Berkeley Civil Engineering 70
Professor Ken Johnson Engineering Geology
Civil Engineering 70 Lecture 27
12/3/07
Sustainability o Switchgrass "You can get 1000 gallons of ethanol from 1 ton of switchgrass" Doesn't make sense o 1000 gallons = 2989 kg o 1 ton = 908 kg Biomass in switchgrass actually produce CO2 and ethanol 37% cellulose 29% hemi-cellulose o = 66% of switchgrass can be used for ethanol Therefore from 908kg of switchgrass, you can only get 254 kg of EtOH (ethanol) taking in account efficiency water input, etc. Plant Biomass 30 50% Cellulose 15 25% Lignin 20 40% Hemi-cellulose o Nothing every leaves the earth Everything be must recycled if it is to be called sustainably Earth is a system open to the sun's radiation About 6000K taken into the earth 300K are emitted o Ecosystems are self sustaining with only sun rays as the only input It takes a forest 120 years to achieve this stability At stability, the ecosystem is most evolved Then fires occur to restart the cycle Little fires are good, big fires will cause extinction But a microcosm can do it in 120 days o China For 4000 years has been engaged in sustainable agriculture They recycled everything o Solar power is significantly more efficient than agri-fuels systems o
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Written By Raymond Leung