Professor: Bernhard Rappenglück
Associate Professor, Atmospheric Chemistry; Atmospheric Sciences Graduate Advisor
Credentials:
Associate Professor, Atmospheric Chemistry; Atmospheric Sciences Graduate Advisor
Credentials:
- Habilitation, Bioclimatology & Atmospheric Environmental Chemistry, Munich University of Technology (TU Munich), 2003
- PhD, Physics, University of Munich (LMU Munich), 1996
- M.S., Meteorology, University of Munich (LMU Munich), 1991
- B.S., Technical Physics, Munich University of Technology (TU Munich), 1985
1) What would be the greatest step humans can make to reduce greenhouse gas emissions?
There is hardly "one sole great" step, but rather a variety of steps. I would consider the following three aspects as critical
2) Reducing primary and trace gases would reduce their concentration in the atmosphere thus reducing the atmospheric effects and health hazards that are associated with such gases. In your opinion, what are the short and long term (and where would we see them) benefits of using compressed natural gas for all public transportation vehicles on the local, regional and global levels?
Remark:
I assume that public transportation you refer to would be mainly buses. In many cities worldwide a significant part of public transportation is by subway, tram, train which usually use electric power. Also, there a bus systems using electric power. In that sense these systems are the cleanest systems on a local scale, as the energy is produced at a different location.
The scales "short term" and "local" are almost interchangeable. On that scales CNG would produce less emission of primary hazardous compounds such as NOx, CO, and particles as well as less formation of ozone and ancillary compounds. In terms of health aspects people using buses driven by CNG would be less exposed to hazardous compounds, locally, which might be most important for these persons. CNG driven buses would also contribute less to ozone formation on a regional scale, but this might be a marginal effect, as buses form minor part of the entire traffic fleet, at least in Houston. There are other cities, often located in developing countries, where bus public transportation makes a significant portion of the entire traffic fleet and, in addition, is poorly maintained. Here, CNG buses would result in highest benefits.
Long-term/global scale:
Public transportation using CH4 combustion as the primary energy source (here I would include buses and rail-bound transportation using electric power) would only slightly decrease CO2 emissions, but would certainly contribute to less particle emissions and ozone formation. The net effect would be significantly better, if the CH4 source would be biogas (instead of fossil CH4), e.g. through organic waste (some municipalities are looking into this). An interesting approach is the power-to-gas technology, which uses renewable energy to hydrogen and methane, where methane is produced
CO2+4H2 → CH4 + 2H2O
One additional remark, valid for any type of public transportation:
Most emission reductions can be achieved, if public transportation is made efficient and attractive, so that as a net result more people will be using the system instead of using an individual car. For instance: a public transportation railway system typically has around 500-600 seats (I am considering seats, only) at rush hour times, which would take a considerable number of individual cars off from any highways/streets.
3) If there is complete combustion of natural gas there are two main gases released, CO2 and H2O. What harmful trace gases are released during incomplete combustion of natural gas and what effect do they have on the environment? How harmful are PM 10, PM 2.5 and PM 0.1?
In principle incomplete combustion of CH4 may emit CO and soot (in particular at high combustion temperatures). Note: CH4 combustion in general requires O2, as such it requires air. This in turn would cause NOx emissions. However, still these emissions would be less than compared with gasoline/diesel driven vehicles.
Thus harmful gases would include CO, NOx, and soot, which would fall into the PM 0.1 category. PM 0.1 is more harmful than larger PM due to (1) larger surface area (which can contain low condensable compounds such as PAH) and (2) as it is alveolar.
4) Which fuel type is least detrimental to human health and the environment and why?
Electric power, as long as it is ultimately produced through sustainable energy sources
5) What health benefits, environmental and economic benefits might we see if we switch to natural gas as a fuel?
It looks like CNG would be cheaper than gasoline or diesel. In case national resources for bio gas can be used, this would provide additional economic benefits. For health and environmental benefits see reply to Q2.
There is hardly "one sole great" step, but rather a variety of steps. I would consider the following three aspects as critical
- Stabilize global population growth
- Increase efficient use of energy (which includes recycling)
- Increase use and efficiency of solar energy
2) Reducing primary and trace gases would reduce their concentration in the atmosphere thus reducing the atmospheric effects and health hazards that are associated with such gases. In your opinion, what are the short and long term (and where would we see them) benefits of using compressed natural gas for all public transportation vehicles on the local, regional and global levels?
Remark:
I assume that public transportation you refer to would be mainly buses. In many cities worldwide a significant part of public transportation is by subway, tram, train which usually use electric power. Also, there a bus systems using electric power. In that sense these systems are the cleanest systems on a local scale, as the energy is produced at a different location.
The scales "short term" and "local" are almost interchangeable. On that scales CNG would produce less emission of primary hazardous compounds such as NOx, CO, and particles as well as less formation of ozone and ancillary compounds. In terms of health aspects people using buses driven by CNG would be less exposed to hazardous compounds, locally, which might be most important for these persons. CNG driven buses would also contribute less to ozone formation on a regional scale, but this might be a marginal effect, as buses form minor part of the entire traffic fleet, at least in Houston. There are other cities, often located in developing countries, where bus public transportation makes a significant portion of the entire traffic fleet and, in addition, is poorly maintained. Here, CNG buses would result in highest benefits.
Long-term/global scale:
Public transportation using CH4 combustion as the primary energy source (here I would include buses and rail-bound transportation using electric power) would only slightly decrease CO2 emissions, but would certainly contribute to less particle emissions and ozone formation. The net effect would be significantly better, if the CH4 source would be biogas (instead of fossil CH4), e.g. through organic waste (some municipalities are looking into this). An interesting approach is the power-to-gas technology, which uses renewable energy to hydrogen and methane, where methane is produced
CO2+4H2 → CH4 + 2H2O
One additional remark, valid for any type of public transportation:
Most emission reductions can be achieved, if public transportation is made efficient and attractive, so that as a net result more people will be using the system instead of using an individual car. For instance: a public transportation railway system typically has around 500-600 seats (I am considering seats, only) at rush hour times, which would take a considerable number of individual cars off from any highways/streets.
3) If there is complete combustion of natural gas there are two main gases released, CO2 and H2O. What harmful trace gases are released during incomplete combustion of natural gas and what effect do they have on the environment? How harmful are PM 10, PM 2.5 and PM 0.1?
In principle incomplete combustion of CH4 may emit CO and soot (in particular at high combustion temperatures). Note: CH4 combustion in general requires O2, as such it requires air. This in turn would cause NOx emissions. However, still these emissions would be less than compared with gasoline/diesel driven vehicles.
Thus harmful gases would include CO, NOx, and soot, which would fall into the PM 0.1 category. PM 0.1 is more harmful than larger PM due to (1) larger surface area (which can contain low condensable compounds such as PAH) and (2) as it is alveolar.
4) Which fuel type is least detrimental to human health and the environment and why?
Electric power, as long as it is ultimately produced through sustainable energy sources
5) What health benefits, environmental and economic benefits might we see if we switch to natural gas as a fuel?
It looks like CNG would be cheaper than gasoline or diesel. In case national resources for bio gas can be used, this would provide additional economic benefits. For health and environmental benefits see reply to Q2.