GHG emission management

Given that most GHGS are on the rise what kinds of strategies can be implemented in terms of new kinds of policies aim at reducing the observed rates? The most effective method would be increasing energy conservation at all levels among global consumers to lower overall impact on the Earth's natural systems. Relative to that approach, all the strategies proposed below are band aid solutions:

For carbon dioxide the following strategies are available:

• Improved Energy Efficiency: This includes better building heat management, improved electrical appliances, and significantly better fuel economy.
  
  
• Fuel Switching: Using switchgrass and other sources of cellulosic ethanol as a replacement for gasoline. Brazil has already demonstrated effectiveness as much of their light duty fleet now runs on fuel stock derived from sugar cane.
  
  
• Carbon Capture and Sequestration (CCS): There are several major obstacles to achieving this on any global scale. Some of these obstacles are a) sources of CO2 emission are highly distributed which would require a variety of different CCS techniques, b) it would be virtually impossible for CCS to operate in the transportation sector. Emission there is best regulated by fuel switching; c) there is a huge disparity between regional ability to sequester carbon in the appropriate underground geological formations and regional CO2 emissions. In particular, China greatly lacks in country favourable geological strata for effective sequestration; d) ultimately the feasibility of CCS is determined by the price of carbon or the social cost of carbon. As long as it's cheaper to put carbon in the air rather than underground, CCS is not likely to be implemented on any significant scale.
  
  

For methane the following strategies are available and some are practical and viable:

• Better management of Fossil Fuel Extraction methods: Upgrade infrastructure to store and transport fossil fuels in such a way so as to minimize leakage. Methane from coal mines, in particular, could be captured and used on site as an electricity generation fuel.
  
  
• Agricultural Sector: Manure management practices can evolve towards capturing more emissions. The same thing can happen for sewage treatment plants and for landfills. This practice would lead to a fuel commodity known as renewable natural gas and although quantities would be initially small, the extraction process is scalable and may have a bright economic potential. This potential is also being explored in various locations in Lane County.
  
  
• Modifications to animal feeding practices may reduce emissions from enteric fermentation and there is now considerable research on how to cultivate rice without the necessary flooding of the rice fields.
  
  

For nitrous oxide, the following management strategies are available:

• Fuel switching: N2O is a by product of fossil fuel combustion. Reducing that automatically reduces emissions. Catalytic converts, first introduced in the 1970s are effective at reducing N2O emissions from vehicles.
  
  
• Agriculture: Enhanced N2O emissions come from the application of nitrogen-based fertilizers. Researchers are trying to find either alternatives to nitrogen-based fertilizer or better utilization efficiency for nitrogen. Reduced used of nitrogen for topsoil fertilization also leads to excessive nitrogen run-off into ocean estuaries causing eutrophication and subsequent fatality to large shellfish populations.

GWP weighting of GHGS and the current equivalent CO2 abundance (CO2e)

There is general consensus in the scientific community, based on ice age calibration of the past relation between atmospheric CO2 levels and global temperature, that a doubling of CO2 content from pre-industrialized times will lead, depending on the role of various feedbacks (like the water vapor feedback loop), to an average temperature increase of 1.5 to 4.5 C. The upper end of this range would have significant global effects and represents a temperature change similar to that of the last ice age of 20,000 years ago. The pre-industrialized concentration of CO2 is agreed to be 280 ppm and so a doubling means 560 ppm; as of August 2018, the concentration of CO2 was 411 ppm-- a 47% increase in just about 150 years. But the real climate forcing effect comes from the entire contribution of all GHGS currently in the atmosphere. This is known as carbon dioxide equivalent or CO2e. Some have now suggested, considering CO2e instead of just CO2, that we are already 1/2 way towards the climate forcing that would be caused by just doubling CO2

CO2e for any atmospheric gas is directly calculated by multiplying GWP for that gas by its total mass that is currently in the atmosphere. For instance, there are currently 871 Gigatons of CO2 (411 ppm) and 5.14 Gigatons of CH4 (1858 ppb). Using GWP = 34 for methane means there are 5.14 x 34 = 175 Gigatons of CO2e due to methane currently in the atmosphere. This is 20% of the current CO2 amount which means CH4 has an equivalency of 82 ppm of CO2. Had the previous value of GWP = 21 been used for methane, the effect would have gone down to 12%. The role of methane as a GHG is generally not well recognized by the lay public or public policy makers. The recent IPCC adjustment upwards of its GWP is significant and currently, methane concentrations are globally rising faster than carbon dioxide concentrations.

The most important point is that CO2e is rising faster than CO2 by itself. This is partially because the GWP of methane is now known to be higher than what was assumed in the past. The only other GHG that contributes significantly to CO2e is N20. This is because, despite its low current concentration of 331 ppb, it has GWP approximately 300 and this converts to an effect that is 40% that of methane. Hence, CO2e for nitrous oxide is now ~ 32 ppm or 7.5 % of current CO2 ppm. Summing all contributions yields (411 + 82 + 31) = 525 ppm as the current value of CO2e. For comparison, the 2001 IPCC report used the 1998 mixture of GHGS to calculate that CO2e was 412 ppm. This means that there has been a factor of 1.27 increase in CO2e since then. In 1998 the observed CO2 concentration was 365 ppm and so it has risen by a factor of 1.13 to its current value of 411.

This rise rate is approximately 2/3 of the rising rate of CO2e. Hence, as of 2018 human activity is well on its way of raising CO2e to effectively doubling the pre-industrialized CO2 concentration relatively soon. It would seem the world is largely unaware of this coming physical reality.

The above can be conveniently summarized in the table below:

Gas	Gtons	PPM	GWP	CO2e
CO2	871	411	1	411
CH4	5.14	1.86	34	82
N2O	2.9	0.33	300	31
Sum	1116	525	1	525
1998		365		412

411/386 = 1.13 ; 525/412 = 1.27

The rate of CO₂e increase is larger than the rate of just CO₂ increase. At the current level of 525 we are well on our way of doubling the pre-industrialized concentration of just CO₂.