Inventory and Impactsof Reactive Nitrogen in the 

Environment

Thomas L. TheisInstitute for Environmental Science and Policy

University of Illinois at Chicago

RET 15 July 2008

What is Reactive Nitrogen (Nr)?

All chemical forms of nitrogen, except N2, that have an impact on the environment

Examples: NH3‐NH4+, N2O, NO, NO2, NO2‐, NO3‐

Organic‐N

Two faces of nitrogenTwo faces of nitrogen

Nitrogen problems

NNDYING DYING REEFSREEFS

FISH KILLSFISH KILLS

ALGAL BLOOMSALGAL BLOOMS

ACID RAIN & ACID RAIN & BIODIVERSITBIODIVERSIT

YY

GLOBAL GLOBAL WARMINGWARMING

GROUNDWATERGROUNDWATER

OZONE/PM OZONE/PM 2.52.5

RED TIDES & RED TIDES & DEAD ZONESDEAD ZONES

Why we need reactive nitrogen

• Human Nr requirement = 4.3 kg/cap/yr • US = 1.4 Tg/yr• World = 28 Tg/yr

The Nitrogen Cascade

Atmospheric

Terrestrial

Agricultural

animalscrops

soils

Vegetated

grasslandsforests

soils

Groundwater

Aquatic Surface Water & Wetlands

Coastal Bays & Estuaries

Oceans

NOy, NHx, Norg

NOx NH3, Norg

NOy, NHx, Norg

N2O

Populated

landscapepeople

soils

ecosystem acidification

greenhouse gases

eutrophication

ecosystem productivity

denitrification potential

N2O

troposphere

stratosphere

NOy , NHxNorg

ozone

Food Production& creation of synthetic fertilizers

Energy Production& combustion of fossil fuels

“new” nitrogen

NHx

NOx

ozone depletion

particulate matter

acidification

Reactive Nitrogen Inputs, US (2002)

4.8surface and subsurface water N flux Nr to Aquatic

0.2industrial point sources 1.3human waste 6.0manure production 10.9synthetic fertilizer use 7.7fixation in cultivated croplands 5.9atmospheric deposition

Nr to Terrestrial0.7other3.9combustion-transportation1.4combustion-power4.0agricultureTg/yrNr to Atmosphere

The Nitrogen Cascade

Atmospheric

Terrestrial

Agricultural

animalscrops

soils

Vegetated

grasslandsforests

soils

Groundwater

Aquatic Surface Water & Wetlands

Coastal Bays & Estuaries

Oceans

NOy, NHx, Norg

NOx NH3, Norg

NOy, NHx, Norg

N2O

Populated

landscapepeople

soils

ecosystems acidification

greenhouse gases

eutrophication

ecosystem productivity

denitrification potential

N2O

troposphere

stratosphere

ozone

Food Production& creation of synthetic fertilizers

Energy Production& combustion of fossil fuels

“new” nitrogen

NHx

NOx

ozone depletion

particulate matter

acidification

5.7

18.6

4.8

4.8

3.11.1

Storage 1.6

Source: USEPA SAB

U.S. NOX Emissions in 2005

On-Road Vehicles

43%

NonroadVehicles

12%

Stationary Fuel Combustion

38%

Industrial processes, waste disposal & other

7%

Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks, 1990-2005

U.S. N2O Emissions in 2005

On-Road Vehicles 7%Non-Road Mobile 0.8%

Agricultural and Soil Management

78%

Other Sources 14%

Source: Inventory of U.S. Greenhouse Gas Emissions and Sinks, 1990-2005

US ammonia emissions

Nitrification and Denitrification Reactions

Nitrification

NH4+ NH2OH [HNO]

NO

[X]

NO2-

NO

N2O

NO3-

N2 N2O NO NO2- NO3

-

Denitrification

NO

Main ControlsSubstrate, O2, H2O, T

Facultative Anaerobic BacteriaMain ControlsSubstrate, available C, O2 , H2O, T

NitrosomonasNitrosospiraNitrosococcus

Nitrobacter

0.00

1000.00

2000.00

3000.00

4000.00

5000.00

6000.00

7000.00

8000.00

9000.00

AL

AZ

AR

CA CO CT DE FL GA ID IL IN IA KS

KY LA ME

MD

MA MI

MN

MS

MO

MT NE

NV

NH NJ

NM NY

NC

ND OH

OK

OR PA RI SC SD TN TX UT

VT

VA

WA

WV WI

WY

Wet Ndep, kg/km2/yr

N manure, kg/km2/yr

Synthethic Nfert, kg/km2/yr

Human Waste, kg/km2/yr

State subtotals surface balance

-1000

0

1000

2000

3000

4000

5000

6000

Nitr

ogen

, kg/

km2 /y

r

PEN

KEN

AN

DSA

CM

ERC

HA

BLA

CO

NH

UD

MO

HD

ELSC

HSU

SPO

TR

AP

JAM

Net import in feedNet import in foodFertilizer useAgricultural N2 fixationNet atmospheric depositionForest N2 fixation

Sources of N to watersheds

Alexander et al. 2002

SPARROW simulated N fluxes in stream reaches

TN Flux (metric tons/yr)< 100100 to 250250 to 1,000> 1,000

StatesKEY

TN Flux (metric tons/yr)< 100100 to 250250 to 1,000> 1,000

Total Fertilizer Consumption, US

0

2

4

6

8

10

12

14

1955 1965 1975 1985 1995 2005

ferti

lizer

con

sum

ptio

n, M

mt N

/yr

30354045505560657075

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Kg g

rain

per

kg

N .

Corn grain produced in the U.S. per Corn grain produced in the U.S. per unit of fertilizer N used, 1964 to 2005.unit of fertilizer N used, 1964 to 2005.

4343

6464*

*Application rate for 2004 estimated as avg of 2003 & 2005.

Data sources: USDA Ag Chem Use Survey & Annual Crop Production.

51% increase in N efficiency12% increase in N fertilizer useSince 1975:

Grain N recovery efficiency usually remains < 50% …room for improvement.

y = 1.829x - 3522r2 = 0.84

0

20

40

60

80

100

120

140

160

180

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Corn

yie

ld, b

u/A

U.S. corn yields, 1964 to 2006.U.S. corn yields, 1964 to 2006.

43 years of 1.8 43 years of 1.8 bubu/A/yr/A/yr

Concept by Cassman, 2006

Genetic Genetic

improvement improvement

Expansion ofExpansion of

irrigation irrigation

Increase inIncrease in

N fertilization N fertilization

Soil testing & balanced

Soil testing & balanced

NPK fertilization

NPK fertilization

IPM IPM TransgenicTransgenic

traits traits Cons.Cons.

tillagetillage

US NOx emission trends 1970-2006

0

1000

2000

3000

4000

5000

6000

7000

8000

1970

1975

1980

1985

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Year

Thou

sand

Met

ric T

ons

of N

itrog

en(c

onve

rted

from

sho

rt to

ns o

f NO

x, a

s N

O2) Misc

Highway vehiclesOff Highway vehiclesIndustrial Manufacturing and ProcessesIndustrial and Other CombustionElectric Utility

Percent reductions in NOx emissions by source, 1990-2002

-40 -30 -20 -10 0 10 20 30

Percent change from 1990 to 2002

Highway VehiclesOff Highway VehiclesIndustrial and Other CombustionElectric Utility

Changes in N wet deposition, 1994-2006

4546474849505152535455

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007A

tmos

pher

ic w

et N

dep

ositi

on in

USA

oxidized N in precipitation, %reduced N in precipitation, %

US Meat Production, 1970-2006

US Milk Production, 1970-2006

Change in U.S. Vehicle Movement, 1990-2005

% 0 10% 20% 30% 40% 50% 60% 70%

CommercialAircraft

FreightTrucks

Light-Duty Vehicles Vehicle Miles Traveled +39%

Ton-Miles +58%

Passenger Miles Traveled +68.8%

Sources: Highway Statistics 2006 Table VM-1, National Transportation Statistics 2005 Table 4-21

Population +19%

GDP +55%

Change in U.S. Vehicle Movement, 1990-2005

0% 10% 20% 30% 40% 50% 60% 70%

CommercialAircraft

FreightTrucks

Light-Duty Vehicles Vehicle Miles Traveled +39%

Ton-Miles +58%

Passenger Miles Traveled +68.8%

Sources: Highway Statistics 2006 Table VM-1, National Transportation Statistics 2005 Table 4-21

-47% NOx

-20.5% N2O

-24% NOx

N2O +1%

NOx +62%

N2O +35.2%

Factors Affecting Mobile N2O and NOX tailpipe emissions

• Fuel characteristics• Air‐Fuel mixes• Combustion temperatures• Use of pollution control equipment• N2O in particular can be formed by catalytic processes used to control NOx, CO, and hydrocarbon emissions

Freight Trucks• GHGs increased 69.4 percent (3.6 percent

annualized)• Medium- and heavy-duty trucks have become

less energy efficient since the mid-1990s – Fuel economy of medium trucks (10,000 to

26,000 lbs) decreased from 8.6 MPG in 1997 to 8.0 mpg in 2002

– FE of heavy trucks (over 26,00G0 lbs) decreased from 6.1 MPG in 1997 to 5.8 MPG in 2002

– Possible explanations for decreased fuel economy

• Demand for more powerful engines• Impact of congestion• Elimination of mandatory speed limits

Tropospheric NO2 Column, East Asia

Boersma et al. (2006) Atmos. Chem. Phys. Discuss., 6, 12301–12345

USEPA

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

Ethanol Explosion

Source: Renewable Fuels Association and preliminary CARD projections

0

3

6

9

12

15

1980

1983

1986

1989

1992

1995

1998

2001

2004

2007

Bill

ion

Gal

lons

Expansions/New Construction

Currently in Production

Ethanol Plants

U.S. corn exports at record high in 2007 U.S. corn exports at record high in 2007 with 25% of crop used for ethanolwith 25% of crop used for ethanol

USDA-FAS, 12/2007.

Continuation of this accomplishment will be challenging.

Iowa the Saudi Arabia of Biomass

Source: U.S. DOE

Energy Independence and Security Act (2007) Section 204 

EPA Report to Congress

SEC. 204.  Not later than 3 years after the enactment of this section and every 3 years thereafter, the Administrator of the Environmental Protection Agency, in consultation with the Secretary of Agriculture and the Secretary of Energy, shall assess and report to Congress on the impacts to date and likely future impacts of the requirements of section 211(o) of the Clean Air Act on the following:

(1) Environmental issues, including air quality, effects on hypoxia, pesticides, sediment, nutrient and pathogen levels in waters, acreage and function of waters, and soil environmental quality.

(2) Resource conservation issues, including soil conservation, water availability, and ecosystem health and biodiversity, including impacts on forests, grasslands, and wetlands.

(3) The growth and use of cultivated invasive or noxious plants and their impacts on the environment and agriculture.

In advance of preparing the report required by this subsection, the Administrator may seek the views of the National Academy of Sciences or another appropriate independent research institute. 

Energy and Independence Security Act (EISA)

• Requires EPA to develop new Renewable Fuel Standard to achieve goal of expanding biofuels to 36 billion gallons by 2022 

• Requires lifecycle assessments of different fuel types and blends compared to petroleum fuel  

• Requires that biofuel production does not adversely impact the environment or natural resources– EPA to assess and Report to Congress on environmental impacts of biofuel system

– Particular recognition of impacts to water quality, EISA amends the Clean Air Act to integrate water quality into a fuel assessment analysis

Renewable Fuel Standard Based on Lifecycle Assessment

• Lifecycle assessment required to determine which fuels meet mandated GHG performance thresholds compared to petroleum fuel replaced– 20% reduction for new facility renewable fuel– 50% reduction for biomass‐based diesel– 60% reduction for cellulosic biofuel

• Lifecycle assessment must include impacts on domestic and foreign land use 

• Corn based ethanol capped at 15 billion/gallons by 2015

How do we assess sustainability?

• Scoping–define goals and system boundaries

• Inventory–document material & energy flows

• Impact Assessment– characterize & assess env. effects using data obtained from inventory

Life Cycle Approach

Carbon and Nitrogen Global Cycles

Relative C/N Profiles