Lec27 - Earth is a system open to the sun’s radiation •...

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University of California, Berkeley Professor Ken Johnson Civil Engineering 70 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 CO 2 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 must be recycled if it is to be called sustainably
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Unformatted text preview: 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 Lecture # 1 of 1 #/#/07 Written By Raymond Leung...
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This note was uploaded on 04/02/2008 for the course CE 70 taught by Professor Johnson during the Fall '07 term at Berkeley.

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