Farm, Ranch, and Rural 

Communities Meeting

Washington DC

February 23, 2009

Integrated Nitrogen Management

James N. Galloway

University of Virginia

Thomas L. Theis

University of Illinois at Chicago

for the 

Integrated Nitrogen Committee

of the

USEPA Science Advisory Board
12/17/2013 2

Integrated Nitrogen Committee

• A self-initiated project of the Science Advisory Board 

begun 1/2007, projected completion 9/2009

• Cross representation from universities, industries, 

government, and NGOs

• Based on the need to develop better strategies to 

manage Nr

• Draft report: 

http://yosemite.epa.gov/sab/sabproduct.nsf/Meeting

Cal/F5B0375541B31DB78525753800486151?OpenDo

cument.

• Comments welcome through March 1
Overview of Talk

 Reactive Nitrogen (Nr) and the N Cascade

 Sources of Nr in the US.

 Nr Fate in the US. 

 Consequences, Impacts and Metrics.

 Selected Recommendations
12/17/2013 4

What is Reactive Nitrogen?

All chemical forms of nitrogen, except N2

Examples: NH3-NH4

+

, N2O, NO, NO2, NO2

-

, 

NO3

-

Organic-N
12/17/2013 5

Why do we need reactive nitrogen?

• Human dietary Nr requirement 

= 4.3 kg/cap/yr 

• US = 1.4 Tg/yr

• World = 28 Tg/yr
Nr Introduction into the US

 Fossil fuel combustion

 stationary sources

 transportation sources

 Haber Bosch Nr

 produced in US

 imported from other countries

 Import of N-containing commodities

 grain and meat

 Biological nitrogen fixation (BNF)

 managed lands

 unmanaged lands
The Nitrogen Cascade

The concept of the nitrogen cascade 

emphasizes that once a new Nr 

molecule is created, it can be 

sequentially transformed and travel 

throughout the environment and 

contribute to a series of major 

environmental problems. 
12/17/2013 8

The Nitrogen Cascade Atmospheric

Terrestrial

Agricultural

crops animals

soils

Vegetated

forests grasslands

soils

Groundwater

Aquatic Surface Water

& Wetlands

Coastal Bays

& Estuaries

Oceans

NOy, NHx, Norg

NOx

NH3, Norg

NOy, NHx, Norg

N2O

Populated

people landscape

soils

biogeochemical cycling

greenhouse gases

eutrophication

ecosystem productivity

denitrification potential

N2O

troposphere

stratosphere

NOy , NHx

 Norg

ozone

Food Production

& creation of synthetic fertilizers

Energy Production

& combustion of fossil fuels

ÒnewÓ nitrogen

NHx

NOx

ozone depletion

particulate matter

acidification
12/17/2013 9

Overview of Talk

 Reactive Nitrogen (Nr) and the Nr Cascade

 Sources of Nr in the US.

 Nr Fate in the US. 

 Consequences, Impacts and Metrics.

 Selected Recommendations
Nr Introduction into the US

Tg N/yr

3.5

1.9

7.7

10.9

4.2

6.4 Natural BNF
3.5

1.9

7.7

10.9

4.2

6.4

NOx transportation

Natural BNF

Nr Introduction into the US

Tg N/yr
3.5

1.9

7.7

10.9

4.2

6.4

NOx transportation

NOx stationary

Natural BNF

Nr Introduction into the US

Tg N/yr
3.5

1.9

7.7

10.9

4.2

6.4

NOx transportation

NOx stationary

Cultivation BNF

Natural BNF

Nr Introduction into the US

Tg N/yr
3.5

1.9

7.7

10.9

4.2

6.4

NOx transportation

NOx stationary

Cultivation BNF

HB-N Fertilizer

Natural BNF

Nr Introduction into the US

Tg N/yr
3.5

1.9

7.7

10.9

4.2

6.4

NOx transportation

NOx stationary

Cultivation BNF

HB-N Fertilizer

HB-N Industry

Natural BNF

Natural, 6.5 Tg N/yr Anthropogenic, 29 Tg Nr/yr

Nr Introduction into the US

Tg N/yr
12/17/2013 16

Overview of Talk

 Reactive Nitrogen (Nr) and the Nr Cascade

 Sources of Nr in the US.

 Nr Fate in the US.

 Consequences, Impacts and Metrics.

 Selected Recommendations
Fate of Introduced Nr

 Lost as Nr from US

 via rivers

 via atmospheric advection

 via exports

 Stored as Nr

 in soils & vegetation

 In groundwater

 Denitrified to N2
N2

NOy NHx

C-BNF, 7.7

Fert. prod., 9.4

United States

Import, 6.0

Lightning, 0.1

Fossil fuel, 5.4

BNF, 6.4

N2O

US Nitrogen Budget

Tg N yr

-1
US Nitrogen Budget

Tg N yr

-1

N2

NOy NHx

C-BNF, 7.7

Fert. prod., 9.4

United States

3.1

2.7

0.8

Import, 6.0

Lightning, 0.1

Fossil fuel, 5.4

BNF, 6.4

2.1

N2O

0.8
US Nitrogen Budget

Tg N yr

-1

N2

NOy NHx

C-BNF, 7.7

Fert. prod., 9.4

United States

3.1

2.7

0.8

Import, 6.0

Export, 4.3

Atm advection, 4.6

Lightning, 0.1

Fossil fuel, 5.4

BNF, 6.4

2.1

N2O

0.8

Atm advection, 0.8

River, 4.8
US Nitrogen Budget

Tg N yr

-1

N2

NOy NHx

C-BNF, 7.7

Fert. prod., 9.4

United States

3.1

2.7

0.8

Import, 6.0

Export, 4.3

Atm advection, 4.6

Lightning, 0.1

Fossil fuel, 5.4

BNF, 6.4

2.1

N2O

0.8

Atm advection, 0.8

River, 4.8

Nr Inputs: 35 Tg N

Nr Outputs: 14 Tg N

Nr Missing: 21 Tg N
US Nitrogen Budget

Tg N yr

-1

N2

NOy NHx

C-BNF, 7.7

Fert. prod., 9.4

United States

3.1

2.7

0.8

Import, 6.0

Export, 4.3

Atm advection, 4.6

Lightning, 0.1

Fossil fuel, 5.4

BNF, 6.4

2.1

N2O

0.8

Atm advection, 0.8

River, 4.8

Nr Inputs: 35 Tg N

Nr Outputs: 14 Tg N

Nr Missing: 21 Tg N

Nr Storage: 5 Tg N

~ 2 Tg soils&vegetation

~ 3 Tg groundwater
US Nitrogen Budget

Tg N yr

-1

N2

NOy NHx

C-BNF, 7.7

Fert. prod., 9.4

United States

3.1

2.7

0.8

Import, 6.0

Export, 4.3

Atm advection, 4.6

Lightning, 0.1

Fossil fuel, 5.4

BNF, 6.4

2.1

N2O

0.8

Atm advection, 0.8

River, 4.8

Nr Inputs: 35 Tg N

Nr Outputs: 14 Tg N

Nr Missing: 21 Tg N

Nr Storage: 5 Tg N

~ 2 Tg soils&vegetation

~ 3 Tg groundwater

Nr Denitrified to N2: 

21 Tg N - 5 Tg N = 16 Tg N
12/17/2013 24

Overview of Talk

 Reactive Nitrogen (Nr) and the Nr Cascade

 Sources of Nr in the US.

 Nr Fate in the US. 

 Consequences, Impacts and Metrics.

 Selected Recommendations
12/17/2013 25

Impacts of manufactured Nr

Positive

Protein requirements for ~3 billion humans

Fertilization of forests

Negative

Air quality impairment

Eutrophication/hypoxia

Loss of biodiversity

Global warming

Acid rain

Ozone depletion

Drinking water contamination
12/17/2013 26

Major (US) federal laws for 

managing nitrogen

• CAA (1990) regulates NOx emitted into 

atmospheric systems

• CWA (1977) regulates NH3 and total Nr 

released into aquatic systems

• SDWA (1996) regulates NO3

- and NO2-

in 

potable waters

• EISA (2007) requires the setting of biofuel 

standards based on life cycle
12/17/2013 27

Metrics for Nr

Quantity: Mass, concentration, flux, loading

Impacts: Category and ecosystem services 

Policy: Adverse risk

Economic: Price of benefits and costs

Regulatory: Criteria, Standards & Thresholds
12/17/2013 28

Metrics Case Study: Chesapeake Bay

Image from Chesapeake Bay Foundation
12/17/2013 29
12/17/2013 30

Share of Nitrogen (Mass) to the Chesapeake Bay

Watershed by Source

Share of NitrogenSources in the Chesapeake BayWatershed

According to Different Metrics

0%

20%

40%

60%

80%

100%

Tonnes N Million $

Damage

Mortality Mitigation

$/Tonne

Freshwater Emissions

Terrestrial Emissions

Atmospheric Emissions

Modified from Moomaw and Birch, 2005
12/17/2013 31

Nr to Chesapeake Using Different Metrics

Share of Nitrogen Sources in the Chesapeake Bay Watershed

According to Different Metrics

0%

20%

40%

60%

80%

100%

Tonnes N Million $

Damage

Mortality Mitigation

$/Tonne

Freshwater Emissions

Terrestrial Emissions

Atmospheric Emissions
12/17/2013 32

Overview of Talk

 Reactive Nitrogen (Nr) and the Nr Cascade

 Sources of Nr in the US.

 Nr Fate in the US. 

 Consequences, Impacts and Metrics.

 Selected Recommendations
Control Points

 The overarching objective is to maintain the 

benefits of nitrogen while minimizing the 

losses to the environment.

 Control points are locations in the N 

cascade where:

 N uptake processes can be improved 

 e.g., nitrogen use efficiency

 N losses to environment can be better managed 

 e.g., wastewater
12/17/2013 34

Selected Recommendations

INC makes the following five 

recommended actions at control points

These recommendations, if enacted, 

would reduce the anthropogenic Nr 

load to the US environment by 20%
The Nitrogen Cascade Atmospheric

Terrestrial

Agricultural

crops animals

soils

Vegetated

forests grasslands

soils

Groundwater

Aquatic Surface Water

& Wetlands

Coastal Bays

& Estuaries

Oceans

NOy, NHx, Norg

NOx

NH3, Norg

NOy, NHx, Norg

N2O

Populated

people landscape

soils

biogeochemical cycling

greenhouse gases

eutrophication

ecosystem productivity

denitrification potential

N2O

troposphere

stratosphere

NOy , NHx

 Norg

ozone

Food Production

& creation of synthetic fertilizers

Energy Production

& combustion of fossil fuels

ÒnewÓ nitrogen

NHx

NOx

ozone depletion

particulate matter

acidification

Control Point: Combustion

Current: 5.4 Tg N

Proposed: 3.4 Tg N

Reduction: 2 Tg N

• We recommend that the EPA expand its NOx control efforts to include 

90% decreases of emissions from heavy-duty on-road, all off-road mobile 

sources and currently uncontrolled electricity generation and industrial 

processes. 
The Nitrogen Cascade Atmospheric

Terrestrial

Agricultural

crops animals

soils

Vegetated

forests grasslands

soils

Groundwater

Aquatic Surface Water

& Wetlands

Coastal Bays

& Estuaries

Oceans

NOy, NHx, Norg

NOx

NH3, Norg

NOy, NHx, Norg

N2O

Populated

people landscape

soils

biogeochemical cycling

greenhouse gases

eutrophication

ecosystem productivity

denitrification potential

N2O

troposphere

stratosphere

NOy , NHx

 Norg

ozone

Food Production

& creation of synthetic fertilizers

Energy Production

& combustion of fossil fuels

ÒnewÓ nitrogen

NHx

NOx

ozone depletion

particulate matter

acidification

Control Point: NH3from Manure and Fertilizer

Current: 2.7 Tg N

Proposed: 2.0 Tg N

Reduction 0.7 Tg N

• We recommend decreasing livestock-derived ammonia emissions 

to approximately 80% of 1990 emissions, a decrease of 0.5 Tg N 

per year.

• We recommend decreasing ammonia emissions derived from 

fertilizer applications by 20%, a decrease by ~0.2 Tg N per year. 
The Nitrogen Cascade Atmospheric

Terrestrial

Agricultural

crops animals

soils

Vegetated

forests grasslands

soils

Groundwater

Aquatic Surface Water

& Wetlands

Coastal Bays

& Estuaries

Oceans

NOy, NHx, Norg

NOx

NH3, Norg

NOy, NHx, Norg

N2O

Populated

people landscape

soils

biogeochemical cycling

greenhouse gases

eutrophication

ecosystem productivity

denitrification potential

N2O

troposphere

stratosphere

NOy , NHx

 Norg

ozone

Food Production

& creation of synthetic fertilizers

Energy Production

& combustion of fossil fuels

ÒnewÓ nitrogen

NHx

NOx

ozone depletion

particulate matter

acidification

Control Point: Nr losses from Croplands

Current: 4.8 Tg N

Proposed: 3.8 Tg N

Reduction 1.0 Tg N

• We recommend decreasing flows of Nr into streams, rivers, and 

coastal systems by approximately 20% through improved 

landscape management, including wetland management improved 

tile-drainage systems and riparian buffers on crop land, etc. 
The Nitrogen Cascade Atmospheric

Terrestrial

Agricultural

crops animals

soils

Vegetated

forests grasslands

soils

Groundwater

Aquatic Surface Water

& Wetlands

Coastal Bays

& Estuaries

Oceans

NOy, NHx, Norg

NOx

NH3, Norg

NOy, NHx, Norg

N2O

Populated

people landscape

soils

biogeochemical cycling

greenhouse gases

eutrophication

ecosystem productivity

denitrification potential

N2O

troposphere

stratosphere

NOy , NHx

 Norg

ozone

Food Production

& creation of synthetic fertilizers

Energy Production

& combustion of fossil fuels

ÒnewÓ nitrogen

NHx

NOx

ozone depletion

particulate matter

acidification

Control Point: Nitrogen Use Efficiency

Current: 18.6 Tg N

Proposed: 16.2 Tg N

Reduction 2.4 Tg N

• We recommend an increase in crop N-uptake efficiencies of 25% 

over current levels through a combination of knowledge-based 

practices and advances in fertilizer technology (such as controlled 

release). 
The Nitrogen Cascade Atmospheric

Terrestrial

Agricultural

crops animals

soils

Vegetated

forests grasslands

soils

Groundwater

Aquatic Surface Water

& Wetlands

Coastal Bays

& Estuaries

Oceans

NOy, NHx, Norg

NOx

NH3, Norg

NOy, NHx, Norg

N2O

Populated

people landscape

soils

biogeochemical cycling

greenhouse gases

eutrophication

ecosystem productivity

denitrification potential

N2O

troposphere

stratosphere

NOy , NHx

 Norg

ozone

Food Production

& creation of synthetic fertilizers

Energy Production

& combustion of fossil fuels

ÒnewÓ nitrogen

NHx

NOx

ozone depletion

particulate matter

acidification

Control Point: Wastewater Treatment

Current: 1.9 Tg N

Proposed: 1.1-1.4 Tg N

Reduction 0.5-0.8 Tg N

• We recommends that a high priority be assigned to nutrient 

management through a targeted construction grants program for 

improved wastewater treatment under the CWA
Integrated Nitrogen Committee 

Summary of Findings

 Human action controls Nr introduction into the US.

 Added Nr has positive impacts for human health--

food production.

 Added Nr increases the risk to both human and 

ecosystem health--N cascade.

 Challenge is how do we achieve positive benefits at 

acceptable risk. 

 And how do we do this in an integrated fashion?