Manure happens: Altering the global nitrogen cycle by feeding about seven billion carnivorous humans

Manure Happens: Altering the Global Nitrogen Cycle by Feeding About Seven Billion Carnivorous

Humans

Eric A. DavidsonSeptember 9, 2014

The History of Nitrogen

0

1,000

2,000

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5,000

6,000

7,000

1750 1800 1850 1900 1950 2000 20500

50

100

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200

Humans, millions Haber Bosch, Tg N

N-Discovered N-Nutrient BNF

N2 + H2→ NH3

Invention of Haber Bosch Nitrogen

The Haber-Bosch process is one of the greatest public

health boons in human history

N Fertilizer Produced

N Fertilizer Applied

N in Crop

N Harvested

Nin Food

NConsumed

-6 -47 -12

100 144794 2631

-5

The Fate of Haber-Bosch Nitrogen

-16

14% of the N produced in the Haber-Bosch process enters thehuman mouth……….



N in Crop

N Harvested

Nin Food

NConsumed

-6 -47 -12

100 144794 2631

-5


-16

14% of the N produced in the Haber-Bosch process enters thehuman mouth……….if you are a vegetarian.

People and Animals

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7,000

1800 1850 1900 1950 2000 20500

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Humans, millions Meat,Total

Mill

ions

of p

eopl

e

Mill

ions

of m

etric

tons

of m

eat

1860 1880 1900 1920 1940 1960 1980 2000

Nitr

ogen

Inpu

ts (T

g N

yr-1

)

0

20

40

60

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100

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140 Manure-N Fertilizer-N NOx-N

Increasing consumption of animal protein

Westhoek et al. (2011) “The Protein Puzzle”Reay et al. (2011) European Nitrogen Assessment



N in Crop

N inFeed

N in Livestock

NConsumed

-6 -47 -3

100 44794 731

-24


-16

4% of the N produced in the Haber-Bosch process and usedfor animal production enters the human mouth.

Consumed Animal

Products

N inputs:

synthetic N fertilizers

manure

& natural N fixation

Consumed Crops

Crop production

Groundwater & surface waters

NH4+ NO3

- DON Npart

NH3 N2O NOX N2

NH4+ NO3

- DON Npart

NH3 N2O NOX N2

Atmosphere

feed

Agriculture

14%

4%Animal production

Nitrogen: A Very Leaky Element

Energy12%

Food51%

Fiber2%

Industrial products35%

N in Products

Natural19%

Intentional67%

Unintentional14%

Total N Fixation

Vehicles63%

Utility and Industry35%

Other2%

Unintentional N Fixation

H‐B Fertilizer46%

H‐B Industry25%

C‐BNF29%

Intentional N Fixation

Lightning2%

BNF98%

Natural N Fixation

6.5 Tg N 4.8 Tg N

24.7 Tg N

23.3 Tg N13.7 Tg N

N2O3%

NOx20%

NH313%

Hydrologic N21%

N lost to the Environment

Unknown20 – 40%

N2

3 – 23%Fates of intentional N fixation in the U.S. for 2007. C-BNF = crop biological N fixation; H-B = Haber-Bosch.

Alteration of N Flows in the U.S.

• Intentional Nr creation accounts for 2/3rds

of total N2 fixation in the U.S.

• Nearly 2/3rds of unintentional Nr is from vehicle use, while a majority of the remainder is from stationary power plants and industrial boilers.

• About 3/4ths of intentional Nr enters US agricultural systems. Synthetic fertilizer comprises 2/3rds of Nr input to U.S. agriculture, with the remainder originating from C-BNF. Industrial products like nylon and explosives account for the remaining 25% of intentionally fixed Nr in the U.S.

• About 1/3rd of total Nr is incorporated into products, about 1/3rd is lost as Nr to the broader environment, about 1/3rd is denitrified or lost to unknown sinks.

• Nitrogen use efficiency is about 38% for agriculture and about 55% for all intentional Nr.

From chapter by Benjamin Z. Houlton, Elizabeth Boyer, Adrien Finzi, James Galloway, Allison Leach, Daniel Liptzin, Jerry Melillo, Todd S. Rosenstock, Dan Sobota, and Alan R. TownsendBiogeochemistry (2013) 114:11-23

The upper photo shows a site in Southern California dominated by exotic annual grasses five years after a burn, and the lower shows a site immediately post-burn.

Both empirical studies and modeling indicate that N and climate change can interact to drive losses in biodiversity greater than those caused by either stressor alone.

In arid ecosystems of southern California, elevated N deposition and changing precipitation patterns have promoted the conversion of native shrub communities to communities dominated by a few species of annual non-native grasses.

A change in biodiversity can also affect ecosystem function, such as increasing fire risk where fuel accumulation was previously rare.

Climate-N Interactions and Biodiversity

From chapter by E. Porter, W. D. Bowman, C. M. Clark, J. E. Compton, L. H. Pardo and J. SoongBiogeochemistry 114: 93-120

Photos by Edith Allen

Reactive N in the atmosphere causes several forms of air pollution (as well as the GHG N2O)

O3

Fine Particulate Matter (PM2.5) NO2

EPA 2005 estimates for US:• PM2.5 exposure caused 130,000 annual

premature deaths • Ozone exposure caused another 4,700

annual premature deaths . • Hundreds of thousands of hospital

visits and millions of additional respiratory symptoms each year are also attributed to this pollution

Drinking Water Nitrate

U.S. standard of 10 ppm In place because of

methylglobinemia

The need for maintaining the standard is a matter of recent controversy

Methemoglobinemia“blue baby syndrome”

Davidson et al. 2012. Issues in Ecology, Report Number 15, Ecological Society of America.

WHO International Agency for Research on Cancer expert working group: “ingested nitrate or

nitrite under conditions that result in endogenous nitrosation is probably carcinogenic to humans”

NOCs are potent carcinogens and teratogens in animals including non-human primates.

Birth defect risks

Prenatal exposure to nitrate in drinking water is associated with neural tube defects, oral cleft defects, and limb deficiencies.

These birth outcome risks occurred at exposures below the current MCL for public water supplies.

However, nitrate may occur in conjunction with other contaminants (e.g., arsenic, pesticides).

USGS findings for 2001-2004:• The federal MCL drinking-water standard was exceeded in >20% of shallow (<30m below the water table) domestic wells in agricultural areas, an increase from 16% a decade earlier.

• About 1.2 million Americans use private drinking wells with [NO3-] between 5 and 10 mgN L-1 and about 0.5 million use wells that exceed 10 mgNL-1.

• The [NO3-] in deep groundwater increased from 1.2 to 1.5 mgN L-1, indicating that municipal water sources may be at risk in the future.


Hog production

NH3 emissions

Costaleutrophication

Grain production

Hypoxic Zones & Eutrophic Coastal Area

http://www.vims.edu/research/topics/dead_zones/

An American family with food for one weekA German family with food for one week A Somalian family with food for one week

Hungary Planet: What the World EatsFaith D'Aluisio and Peter Menzel, Random House, 2005

NATURE|Vol 461|24 September 2009“Editor’s note Please note that this Feature and the Commentaries are not peer-reviewed research. This Feature, the full paper and the expert Commentaries can all be accessed from http://tinyurl.com/planetboundaries.”

EPA. 2006. Global Anthropogenic Non-CO2 Greenhouse Gas Emissions: 1990-2020.

1990-2000

Stratospheric photochemical sink of N2O: 11.9 TgN2O-N/yr

Total N2O source = photochemical sink (11.9 TgN2O-N/yr) + atmospheric growth (3.9 TgN2O-N/yr) = 15.8 TgN2O-N/yr

Anthropogenic N2O source = total source (15.8 TgN2ON/yr) - current natural source (9.3 to 10.2 TgN2O-N/yr) = 5.6–6.5 TgN2O-N/yr

Agricultural contribution = 5.6–6.5 TgN2O-N/yr - industrial source (0.7–1.3 TgN2O-N/yr) = 4.3–5.8 TgN2O-N/yr

New anthropogenic fixed N = 86 Tg N Haber-Bosch fertilizer + 24.2 Tg N fixed due to fossil fuel combustion + 3.5 Tg new BNF = 114 Tg N/yr

Anthropogenic N2O yield = 4.3–5.8 TgN2O-N/yr 114 Tg N/yr “new” fixed N = 3.8 – 5.1%

Pre-industrial:

Stratospheric photochemical sink of N2O total N2O source 10.2 TgN2O-N/yr

Natural source from land and coastal zones = 6.2 to 7.2 TgN2O-N/yr

New annual N fixation = 141 Tg N/yr

N2O yield = 6.2 to 7.2 TgN2O-N/yr 141 Tg N/yr “new” fixed N = 4.4 – 5.1%

Crutzen et al. Atmos. Chem. Phys. 8, 389-395 (2008)

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1860 1880 1900 1920 1940 1960 1980 2000

Atm

osph

eric

N2O

(ppb

)Observed

Crutzen model

The Crutzen et al. (2008) model, based on 4% of annual newly fixed N, underestimates atmospheric N2O from about 1880 to 1980.

To match the observed rate of atmospheric accumulation in the 1950s, 10% of annual newly fixed N would have to have been converted to N2O. Davidson, E.A. 2009. Contribution of manure and fertilizer nitrogen to

increasing atmospheric nitrous oxide since 1860. Nature Geoscience, 2:659-662.

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1860 1880 1900 1920 1940 1960 1980 2000

Atm

osph

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N2O

(ppb

)

Observed

Crutzen model

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1860 1880 1900 1920 1940 1960 1980 2000

Nitr

ogen

(Tg/

year

)

Manure

Synthestic N Fertilizer

NOx

Holland, E. A., Lee-Taylor, J., Nevison, C., & Sulzman, J. Global N cycle: fluxes and N2O mixing ratios originating from human activity. Data set available on-line [http://daac.ornl.gov/CLIMATE/guides/N_Emiss.html] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. (2005).

Time-course analysis of sources and sinks of atmospheric N2O since 1860, using both top-down and bottom-up constraints

Previously compiled database (Holland et al. 2005) of:

• atmospheric N2O concentrations

• manure production

• fertilizer-N use

• legume cultivation

• NOx emissions

New annual estimates of N2O production from:

• fossil fuel N2O sources

• nylon production

• biomass burning

• tropical deforestation

• temporal estimates of the stratospheric sink for N2O

For each year, the anthropogenic biological source was calculated as follows:

Anthro-Bio source = Atmospheric growth – industrial & transport sources + anthropogenic sink + reduced natural tropical forest soil source

The fractions of annual manure-N production (Fm) and annual synthetic fertilizer-N production (Ff) that are released as N2O were estimated by multiple linear regression, using historical data for manure-N and fertilizer-N production:

Anthro-Bio source = Fm*manure-N + Ff*fertilizer-N

Anthro-Bio source = 0.0203*manure-N + 0.0254*fertilizer-N (p < 0.0001 for each coefficient; adjusted R2 = 0.98)

The entire 19th-20th century pattern of increasing atmospheric N2O can be fit to a regression model related to human food production systems, assuming that 2.0% of annual manure production and 2.5% of annual synthetic fertilizer-N production are released as N2O.

Sensitivity analyses of uncertainties in input data suggest that these coefficients likely fall within these ranges:

Manure-N production: 1.6% - 2.7%

Fertilizer-N production: 1.7% - 2.7%

These yield percentages are within the ranges of uncertainty of IPCC average emission factors.

However, these results differ from the Crutzen et al. (2008) model, because manure-N is not necessarily newly fixed N.

Manure was the dominant source in the 19th

century 0

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5

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1860 1880 1900 1920 1940 1960 1980 2000

Atm

osph

eric

N2O

-N G

row

th (T

gN/y

r)Total Source Model

NylonN2OTransportN2O

FertilizerN2O

ManureN2OBiomass Burning

Manure still dominates, but fertilizers are also important

Where does the N in manure come from? It may not all be newly fixed N.

Mining of soil N due to expansion of livestock and agricultural production from 1860 to 1960, before synthetic fertilizer-N could replace lost soil N, could explain why atmospheric N2O increased from 1860 to 1960 at a faster rate than predicted from a model of 4% of annual new N fixation.

David, M. B., McIsaac, G. F., Royer, T. V., Darmody, R. G. & Gentry, L. E. Estimated historical and current nitrogen balances for Illinois. The Scientific World 1, 597-604. DPO10.1100/tsw.2001.283 (2001).

David, M. B., McIsaac, G. F., Royer, T. V., Darmody, R. G. & Gentry, L. E. Estimated historical and current nitrogen balances for Illinois. The Scientific World 1, 597-604. DPO10.1100/tsw.2001.283 (2001).

Units are Gg N yr-1

http://www.unep.org/publications/ebooks/UNEPN2Oreport/

What are the technical, economic, and social impediments and opportunities for increased nitrogen use efficiency in crop and animal production systems?

Nitrogen Use Efficiency in Nebraska’s Central Platte

Valley

Richard B. FergusonProfessor of Soil ScienceDepartment of Agronomy & HorticultureUniversity of Nebraska-Lincoln

Hog production

NH3 emissions

Costaleutrophication

Grain production

Stakeholder input on performance indicators

They have power -ballot box and the

super market

Applying the Right Source at the Right Rate at the Right Time and in the Right Place, where Right is defined by practice impact on system performance

Paul Fixen

Trends in the Central Platte Valley

Average of values from producer reports in GWMA, representing ~ 300,000 acres

y = ‐0.1523x + 321.41R² = 0.824

y = ‐2.1092x + 4289.4R² = 0.6312

0

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Soil Re

sidu

al NO3‐N (lb/acre)

Groun

dwater NO3‐N(ppm

)

A study of 54 dairy farms in Wisconsin demonstrated that more of the N fed to cows ends up in the milk and less in the manure when:• the feed is modified to be more balanced• hormones are managed• when milking is done three times per day.

Adapted from Powell et al. 2006. J. Dairy Sci. 89,2268-2278

Balanced rations

Total mix-ed rations

bST

Milk 3x/d

Mixed economic signals N fertilizer costs are high enough for many farmers to want to

improve NUE. But most also agree that the economic risk of applying too little N

is high. N application provides an important economic margin of safety, like

relatively inexpensive insurance.

Estimated shares of variable costs per acre for rotation corn in Indiana in 2013

From 2013 Purdue Crop Cost & Return Guide. Purdue Extension publication ID-166-W.

Estimated costs for adopting several currently available management practices across the Ceder Creek Watershed, Iowa, for a 35% load reduction, implemented over a 20 year period. The total cost is $71 million per year, or $7.78 kg-1 N removed yr-1, or $42 ha-1 yr-1 (from Dan Jaynes, USDA-ARS, and Mark David, Univ. Illinois).


Linda ProkopyPurdue Univ.

RECOMMENDATIONS: Develop partnerships & networks between industry,

universities, governments, NGOs, crop advisors, and farmers to demonstrate the most current, economically feasible, best management practices.

Provide improved, continuing education to private sector retailers and crop advisors through professional certification programs by university and government extension

Provide science-based recommendations through trusted sources of information to help reduce the perception of risk and the perceived need to apply additional N for “insurance” purposes.

1995-97 2002-04

Source: IFDC

PAN AFRICAN SOIL NUTRIENT DEPLETION kg nutrient ha-1

Initial Goal of African Green RevolutionMoving from 1 to 3 tons per hectare

0 N added 1 ton/ha of maize

50 kg N ha-13 tons/ha maize