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Generating Enough Renewable Energy
Bruce E. Rittmann
Director, Center for Environmental BiotechnologyBiodesign Institute at Arizona State University
Regents’ Professor, School of Sustainable Engineering and the Built Environment
Ira A. Fulton School of Engineering
Trends in Atmospheric CO2• 1000 - 1800 -- ~ 280 ppmv (pre-industrial)• 1870 -- ~ 300 ppmv (industrial revolution)• 1950 -- ~ 305 ppmv (post WWII)• 1970 -- ~ 325 ppmv • 1988 -- ~ 350 ppmv• 2000 -- ~ 360 ppmv• 2006 -- ~ 375 ppmv• 2010 -- ~ 390 ppmv• 2050 -- est. from 450 to 550 ppmv• 2100 -- est. from 490 to 1000 ppmv
•Emissions target to hold at today’s CO2 level
IPCC hoped for stabilization level
Scale! Scale! Scale! Scale!
• Human activities now use about 13-14 TerraWatts (TW = a trillion watts = 10-billion 100-watt light bulbs) of energy.– ~ 84% is from fossil fuels (~ 11 TW): 34%
oil, 32% coal, 14% natural gas• We need to replace about 7 TW with renewable
energy. This means doable at a large scale.• To get the most high value services of fossil
fuels, we need to produce a lot more biomass in an environmentally acceptable manner.
Plants or Microbes?Photosynthetic Microorganisms• Fast growing - doubling time 0.5-1 day• Do not require arable land• Growth year-round• High areal production• Homogeneous (all cells are the same)• Water-efficient; can recycle minerals• Not lignocellulosic
Plants• Slow growing - usually only one crop a year• Require arable land• Growth seasonal• Low areal production• Heterogeneous (leaves, seeds, stems, etc.)• Require water and fertilizer; pollutes water• Largely lignocellulosic
Example: The areal production of biomass and its energy content is roughly 100 times greater with photosynthetic microorganisms. This puts the output into the TW range.
Photobioreactors for Microbial Phototrophs
The lipids go to “biopetrol,” and the non-lipid biomass can be converted to CH4, electricity, or H2.
17-L bench-top PBR (left)
2100-L rooftop PBR (right)
Synechocystis PCC6803
Generating Enough Renewable Energy
Bruce E. Rittmann
Director, Center for Environmental BiotechnologyBiodesign Institute at Arizona State University
Regents’ Professor, School of Sustainable Engineering and the Built Environment
Ira A. Fulton School of Engineering