Anthropogenic Greenhouse Gases
and its Impact on Global Warming
The Greenhouse Effect
Greenhouse gases (GHGs) contribute to the
warming of the planet by absorbing and reemitting
radiation that would otherwise escape from the
earth’s surface
Atmosphere
Anthropogenic GHG Emissions Contributing to
Global Warming
Anthropogenic GHG Emissions, those
Caused by Human Activity, Include both CO2
and Non-CO2 GHG Emissions
Agriculture
Human Activities
that Generate
GHG Emissions
Industrial
Processes
Waste
Energy
CH4
20.7%
CO2
71.6%
Non-CO2
28.4%
N2 O
6.9%
High GWPs
0.7%
Source: Graph and data from “Global Anthropogenic Non-CO2 Greenhouse Gas Emissions: 1990 – 2030.” Revised December 2012. The U. S.
Environmental Protection Agency.
GHG Emissions in Rice Farming
7%
of Agricultural Non-Carbon
Dioxide GHG Emissions are a
result of Rice Farming
CH4 through
Methanogenesis
Rice
Farming
N2O through
Denitrification
CH4 and N2O, Common in Rice Farming, are
Stronger Contributors to Global Warming
than CO2 Emissions
25/
300/
Number of times the potential
global warming impact of CH4
surpasses that of CO2
Number of times the potential
global warming impact of N2O
surpasses that of CO2
Source: Graph and data from “Global Anthropogenic Non-CO2 Greenhouse Gas Emissions: 1990 – 2030.” Revised December 2012. The U. S.
Environmental Protection Agency.
Methanogenesis
Methanogenesis, or the production of methane (CH4), occurs in flooded rice fields as bacteria respire (or
“breathe”) in the absence of oxygen
3
CO2
CH4
2
1
H2O
bacteria
H2
1
Because rice fields are flooded,
soil gets waterlogged and cannot
store oxygen
2
bacteria
The bacteria that can “breathe” in
the absence of oxygen take in
carbon dioxide (CO2), abundant in
the form of plant matter and
hydrogen gas (H2), present in the
atmosphere
3
These bacteria “breathe” out
methane gas (CH4) in addition to
producing water (H2O) as a
byproduct of methanogenesis
Denitrification
Denitrification occurs as an alternative to methanogenesis, when bacteria “breathe” in nitrates (NO3-, NO2-)
and “breathe” out nitrogen gas (N2) and nitrous oxide (N2O)
N2
3
N2O
2
1
N2O
NO3-
NO21
bacteria
Because rice fields are flooded,
soil gets waterlogged and cannot
store oxygen
bacteria
2
NO-
bacteria
bacteria
Bacteria that can “breathe” in the
absence of oxygen take in nitrates
(NO3-, NO2-), abundant in
fertilizers, and produce nitrous
oxide (N2O) and nitric oxide (NO-)
as intermediates
3
These bacteria ultimately convert
the N2O to nitrogen gas (N2),
which makes up over 70% of the
gas in the atmosphere. However,
not all of the N2O gets converted
to N2, resulting in N2O emissions
How to Address this Challenge?
AgResults Vietnam
GHG Emissions
Reduction Pilot
Solution: Increase adoption of agronomic practices and products
that reduce GHG emissions in rice production and increase yield
Incentive: Provide prizes based on the practices adopted by
farmers and reduction of GHG emissions achieved
Practices that Result in
High GHG Emissions
Practices that Reduce
GHG Emissions
Saturation
of Rice
Fields
Overuse of
Fertilizers
Modified
Irrigation
Efficient
Use of
Fertilizers