The agricultural nitrogen cycle
and induced N2O emissions
Author: Benjamin Bodirsky
PIK RD I Earth System Analysis
“Price of Land “-Flagship Project
INTRODUCTION – Nitrogen: boon and bane
OUTPUT & VALIDATION – present and future N2O emissions
Reactive nitrogen (Nr) is not only an important nutrient for plant
growth, thus indirectly safeguarding human alimentation, but also
disturbs natural systems when it is abundantly available. In the form
of nitrous oxide (N2O), it is a key driver of ozone depletion and global
warming.
The results suggest, that the mix of Nr inputs is very heteregenous between
regions. In the future, fertilizer consumption rises significantly, as can be
confirmed by statistical data from 1995 and 2005 (fig. 2). Also the estimates
of regional emissions are in line with results of other studies (fig. 3).
Fig. 2 Industrial nitrogen
fertilizer consumption in
1995 and 2005 as
estimated, compared to
actual fertilizer
consumption.
The aim of this work is to estimate future N2O emissions of the
agricultural sector, depending on population growth and incomerelated diet change.
METHODOLOGY – Balanced budget approach
The analysis is based on the global spatial-explicit (0.5°) land-use
allocation model MAgPIE (Lotze-Campen et al. 2008), which
optimizes land-use patterns to meet a food demand at minimal
production costs. The food demand depends on population growth
and current regional diets. With increasing income per capita, the
caloric demand and the share of livestock calories rises. Livestock
production in turn requires the cultivation of feed crops.
The model was extended by introducing a nitrogen constraint, which
requires that in every grid-cell the nitrogen budget of the soil has to
be balanced out (fig. 1). The amount of Nr withdrawn from the field
by the harvested product or lost to the environment has to be
replaced by an endogenously calculated mix of Nr inputs like manure,
agricultural residues, biofixation or fertilizer.
Fig. 1 Agricultural
Nitrogen Flows
Withdrawals
1 Harvested Crop
2 Crop Residue
3 Livestock Product
Losses
4 Leaching
5 Volatilization
(N2O, N2,NHx,NOy)
Inputs:
6 Inorganic Fertilizer
7 Manure on Cropland
8 Manure on Pasture
9 Recycling of Residues
10 Biological fixation
11 Atmosph. Deposition
Finally, Nr inputs were linked to specific N2O emission factors based
on the 2006 IPCC Guidelines for National Greenhouse Gas
Inventories.
Fig. 3 Regional agricultural
N2O emissions in 1995.
Result comparison of
MAgPIE, USEPA (2006) and
EDGAR 32FT2000.
MAgPIE results were
calculated with two
different sets of emission
parameters (IPCC 1996 &
IPCC 2006)
CONCLUSIONS & OUTLOOK– mitigation and “meatigation”
N2O emissions from agriculture are major contributors to both global
warming and ozone depletion. The amount of emissions depends largely on
the dietary patterns and is very sensitive to the amount of livestock
products consumed (fig. 4).
Fig. 4 Global N2O and CH4
emissions under increased
(A) or decreased (B)
consumption of livestock
products (Popp et al. 2010)
Besides changing consumption patterns, mitigation can also occur by
improved management practices on the production side. Yet, both types
of mitigation require a policy framework, which gives incentives to
change behaviour. Such a policy framework will not only have an impact
on N2O, but also on further environmental, social and economic
parameters. It will be the aim of my future research to give a wholistic
overview over the impacts of environmental policies.
REFERENCES
•
IPCC. 1996. Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories. Institute for Global Environmental
Strategies (IGES).
•
Popp, A., H. Lotze-Campen, and B. Bodirsky. 2010. Food consumption, diet shifts and associated non-CO2 greenhouse
gases from agricultural production. Global Environmental Change.
•
IPCC. 2006. 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Institute for Global Environmental
Strategies (IGES).
•
US-EPA. 2006. Global Anthropogenic Non-CO2 Greenhouse Gas Emissions: 1990-2020. Ed. Elizabeth Scheehle.
Washington, DC: United States Environmental Protection Agency.
•
Lotze-Campen, H., C. Müller, A. Bondeau, S. Rost, A. Popp, and W. Lucht. 2008. Global food demand, productivity
growth, and the scarcity of land and water resources. Agricultural Economics 39, no. 3: 325–338.
•
Van Aardenne, J. A., F. J. Dentener, J. G. J. Olivier, J. Peters, and L. N. Ganzeveld. 2005. The EDGAR 3.2 fast track 2000
dataset (32FT2000). Emission Database for Global Atmospheric Research.
Contact Benjamin Bodirsky
Tel.: 0049 331 288 2415
[email protected]
Potsdam Institute for Climate Impact Research
Telegrafenberg A31 | D-14473 Potsdam
www.pik-potsdam.de