1. Generating Enough Renewable Energy Bruce E. Rittmann Director, Center for Environmental Biotechnology Biodesign Institute at Arizona State University Regents Professor, School of Sustainable Engineering and the Built Environment Ira A. Fulton School of Engineering

2. Trends in Atmospheric CO 2 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 todays CO 2 level IPCC hoped for stabilization level

3. 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.

4. 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.

5. Photobioreactors for Microbial Phototrophs The lipids go to biopetrol, and the non-lipid biomass can be converted to CH 4, electricity, or H 2. 17-L bench-top PBR (left) 2100-L rooftop PBR (right) Synechocystis PCC6803

6. Generating Enough Renewable Energy Bruce E. Rittmann Director, Center for Environmental Biotechnology Biodesign Institute at Arizona State University Regents Professor, School of Sustainable Engineering and the Built Environment Ira A. Fulton School of Engineering