1. Emissions scenarios under a hydrogen economy
David Damm
EAS 6410
April 23, 2007

2. Outline Motivation for Hydrogen economy
Potential effects of molecular hydrogen emissions
Effects of hydrogen economy on GHG emissions
Effects of hydrogen economy on surface air quality
Proposed study

3. The role of hydrogen Primary Sources Energy Carriers CO2 CO2
Renewable (Solar, Wind, Biomass)
Fossil Energy (Oil, coal, gas)
Nuclear
Energy Carriers
gasoline (distillates)
Hydrogen
Electricity (Grid)
CO2
CO2
Stationary, industrial, residential
Transportation, small-scale distributed
Energy Utilization

4. Motivation Electrochemical conversion of hydrogen to work (fuel cell)
higher theoretical efficiency than combustion
no “pollutants” such as CO, NOx, SOx, HC
Enables energy pathways for GHG mitigation
via centralized carbon sequestration
via utilization of carbon-free primary energy sources
Would anthropogenic emissions of hydrogen pose an environmental threat?

5. Hydrogen emissions
Tromp (2003); stratospheric ozone depletion and temperature decrease (greenhouse warming potential)
requires unreasonably high increase in atmospheric H2 (Prather, 2003)
stratospheric H2 remains constant as CH4 has increased dramatically (Rohs, 2006)
Schultz (2003), Rhee (2006); most tropospheric hydrogen consumed by uptake in soils (82%) with tropospheric lifetime of only 1.4 yrs.
could soil sink accommodate increased H2 emissions?
How is tropospheric O3 affected by hydrogen economy (via changes in NOx, SOx, CO, HC emissions)?

6. Motivation
Do the potential benefits of hydrogen outweigh its potential environmental risks?

7. Methane

8. Methane

9. Nitrous Oxide (N2O)

10. Nitrous Oxide (N2O)
Industrial sources include: nylon and nitric acid production, power plants, and vehicular emissions (~0.11 TgN/yr)

11. Carbon Monoxide (CO)

12. Volatile organics (VOC)

13. Nitrogen oxides (NOx)

14. Emissions scenarios

15. CO2 emissions

16. CH4 Projections

17. Ozone precursor emissions

19. Warming potential of GHG
Scenario A1FI (IPCC report)

20. Hydrogen Economy study
Estimate effect (present – 2100) on:
Greenhouse gas emissions (CO2, CH4, O3)
surface ozone precursor emissions (CO, H2, NOx, SOx, VOC)
1. Reference case: business-as-usual
2. Complete transition to hydrogen-powered FCV over 15, 25, 50 yr timeframe
Hydrogen produced using fossil energy initially, transition to renewable within 25, 50 yr
No hydrogen-powered FCV
2x renewable energy capability as (2), but displaces coal power plants rather than gasoline-powered vehicles
Where should our investment be focused in the near term (considering only emissions and air quality)?

21. References
[1] Tromp TK, Shia RL, Allen M, Eiler JM, Yung YL. (2003) “Potential environmental impact of a hydrogen economy on the stratosphere”. Science 300 (5626)1740-2
[2] Prather MJ. (2003) “An environmental experiment with H-2”? Science 302 (5645) 581-2
[3] Rohs S, Schiller C, Riese M, Engel A, Schmidt U, Wetter T et al. (2006) “Long-term changes of methane and hydrogen in the stratosphere in the period and their impact on the abundance of stratospheric water vapor”. Journal of Geophysical Research-Atmospheres 111 (D14)
[4] Rhee TS, Brenninkmeijer CAM, Rockmann T. (2006) “The overwhelming role of soils in the global atmospheric hydrogen cycle”. Atmospheric Chemistry and Physics
[5] Schultz MG, Diehl T, Brasseur GP, Zittel W. (2003) “Air pollution and climate-forcing impacts of a global hydrogen economy”. Science 302 (5645) 624-7
[6] Intergovernmental Panel on Climate Change, “Climate Change 2001: The Scientific Basis”
[7] Intergovernmental Panel on Climate Change, “Climate Change 2001: Mitigation”
[8] Prather M, Gauss M, Berntsen T, Isaksen I, Sundet J, Bey I et al. (2003) “Fresh air in the 21st century?” Geophysical Research Letters 30 (2)