1. Carbon Sequestration in Grasslands:
Climate Change Mitigation Potential
Whendee L. Silver
Rudy Grah Chair of Sustainability and Professor of Ecosystem Ecology
Department of Environmental Science, Policy, and Management
University of California, Berkeley
True Cost Accounting in Food and Farming
December 6, 2013
2. Atmospheric CO2 concentrations are increasing
Atmospheric CO2 (ppm)
400
390
August 2013
380
370
360
350
340
330
320
310
1950
1960
1970
1980
1990
2000
2010
2020
Year
Data: Dr. Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography
4. Projected Atmospheric CO2 (ppmv)
450
Reducing emissions alone will not mitigate
climate change
440
430
420
410
400
390
380
370
360
350
Year
5. Atmospheric CO2 concentrations are increasing
Atmospheric CO2 (ppm)
400
390
August 2013
380
370
360
350
340
330
320
310
1950
1960
1970
1980
1990
2000
2010
2020
Year
Data: Dr. Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography
6. Atmospheric CO2 concentrations are increasing
Atmospheric CO2 (ppm)
400
390
Can land management
be part of the solution?
August 2013
380
370
360
350
340
330
320
310
1950
1960
1970
1980
1990
2000
2010
2020
Year
Data: Dr. Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography
8. Grasses allocate a high proportion of their photosynthate
belowground to roots greater soil carbon pools
9. Grasslands cover a significant portion of the Earth’s
land surface
*30% of global land surface *Over half of the global land use
*50% of the UK land area
*50% of California land area
10. Managing soils for increased carbon content
has many co-benefits:
•Fertility
•Water holding capacity
•Soil stability
•Sustainability
•Productivity
11. Converting waste to food
Food and agricultural
waste
Compost it…..
And create a
carbon sink
12.
13. Plant production (aka forage) has increased every year following a
one time compost application
control
compost
Aboveground Net Primary
Production (g / m2)
1000
750
500
250
0
1
2009
2
2010
3
2011
4
2012
Year
Ryals and Silver 2013 Ecological Application, Ryals et al. in prep.
14. A one-time application of compost increased soil carbon
Pre-treatment
2009
2010
2011
Ryals et al 2014 Soil Biology and Biochemistry
15. Global warming potential (MMT CO2e)
Life cycle assessment suggests much higher climate
change mitigation potential
Applied to 1 million hectare
30
GHG Emissions
GHG Mitigation
Net
20
10
0
-10
-20
-30
-40
Compost Manure Nitrogen
Fertilizer
Redrawn from DeLonge et al. 2013
16. A survey of 35 fields showed that organic amendments
increased soil carbon by depth
90
Soil Carbon (Mg ha-1)
80
Extensive (24)
Amended (11)
70
60
50
40
30
20
10
0
0-10
10-30 30-50 50-100
Depth (cm)
Silver et al. in prep
17. Soil Carbon (Mg ha-1 to 1 m)
…and that amended fields had an average of 40 Mg more soil
carbon per hectare
150
100
50
0
Extensive Amended
Management
Silver et al. in prep
18. 1 metric ton of carbon per hectare over 6 million hectares =
21 million metric tons (MMT) of CO2e
* 1 MMT = 1012 g
19. 1 metric ton of carbon per hectare over 6 million hectares =
21 million metric tons (MMT) of CO2e
•Livestock ~ 15 MMT CO2e/y
•Commercial/residential ~ 42 MMT
CO2e/y
•Electrical generation ~112 MMT
CO2e/y
* 1 MMT = 1012 g
21. Carbon sequestration potential
from improved grazing practices:
Scaled to 12 million hectares of rangelands
0.4 to 0.9 Mg C ha-1 y-1: 15-37 MMT CO2e y-1
1 Mg C ha-1 y-1: 42 MMT CO2e y-1
* 1 MMT = 1012 g
Data sources: Eagle et al. 2011, Conant et al. 2001
22. Summary
1. Agriculture can be part of the solution to climate
change (in a significant way!)
2. Soil carbon sequestration is possible and quantifiable
in rangeland soils
3. Key questions and next steps:
What are the best grazing practices work and why?
Testing in arid and semi-arid grasslands.
23. Marin Carbon Project
Nicasio Native Grass Ranch
Support provided by:
United States Department of Agriculture
United States National Science Foundation
The 11th Hour Foundation
The Marin Community Foundation
The Rathmann Family Foundation
The Lia Foundation
The Kearney Foundation for Soil Science
University of California, Berkeley
25. Availability of compost
Potential compost production: 27 to 33 MMT y-1
Enough to reapply to 12 million ha of rangelands
every 17-40 years
26.
27. 400
390
380
Atmospheric CO2 (ppm)
September 2012
370
360
350
340
330
320
310
1950
1960
1970
1980
1990
2000
2010
2020
Data: Dr. Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography .
28. 400
390
Can land management
be part of the solution?
380
Atmospheric CO2 (ppm)
September 2012
370
360
350
340
330
320
310
1950
1960
1970
1980
1990
2000
2010
2020
Data: Dr. Pieter Tans, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography .
29. Global warming can’t be explained by solar cycles
http://www.ncdc.noaa.gov/cmb-faq/globalwarming.html
30. Scalability
One quarter of the rangeland area in California:
= 23 Tg of CO2e y-1 (without including compost C)
= 337 Tg of CO2e y-1 (with compost C additions)
* 1 Tg (Teragram) = 1012 g
33. There are several sources and sinks of greenhouse gases
associated with soil amendment application to grasslands
+
DeLonge et al. in review
Editor's Notes
And of course we know that fossil fuel emissions are the primary culprit
We are all on thin ice
396.78
396.78
Using plant and animal waste products provides significant offsets in addition to the C gains at the field scale. The net offsets from compost amendments are very large, when applied to just 10% UK’s rangelands or 5% of CA rangelands
Up to 1 MgC/ha/y
California currently landfills approximately 10 million Mt of compostable organic waste per year and Cal recycle estimates over the next decade it hopes to increase organic waste diversion to compost to 14-16 million Mt/y. Add in approximately 6 million Mt of landfill paper, an additional 10.8 million Mt of animal waste, and approximately 6.5 million Mt of biosolids could be composted. Together this amounts to 33 million Mt of compost per year, increase to almost 40 million Mt by 2020.This will yield somewhere between 18-22 million m^3 of compost. It would cover 25% of CA rangelands in 17-41 years (I will have explained the fact that we don't need to apply very often) and sequester between 0.3 and 0.6 MMT CO2e per year assuming a rate of 0.5 and 1 Mt C/ha/y, respectively. It may be possible to get the same effect with less compost, in which case the net sequestration rate for the state would increase.
396.78
396.78
California currently landfills approximately 10 million Mt of compostable organic waste per year and Cal recycle estimates over the next decade it hopes to increase organic waste diversion to compost to 14-16 million Mt/y. Add in approximately 6 million Mt of landfill paper, an additional 10.8 million Mt of animal waste, and approximately 6.5 million Mt of biosolids could be composted. Together this amounts to 33 million Mt of compost per year, increase to almost 40 million Mt by 2020.This will yield somewhere between 18-22 million m^3 of compost. It would cover 25% of CA rangelands in 17-41 years (I will have explained the fact that we don't need to apply very often) and sequester between 0.3 and 0.6 MMT CO2e per year assuming a rate of 0.5 and 1 Mt C/ha/y, respectively. It may be possible to get the same effect with less compost, in which case the net sequestration rate for the state would increase.
Line is average minimum extent 1979-2010
That said, we realized that our field experiment was only a piece of a larger puzzle, and that to truly understand the implications of this management practice over large areas we would need to consider a wide array of other greenhouse gas sinks and sources.
