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Whendee Silver - Soil
1. From Garbage to Gold:
Managing Grasslands for Climate Change Mitigation
Whendee L. Silver
Department of Environmental Science, Policy, and Management
University of California, Berkeley
True Cost Accounting of American Food
April 15, 2016
2. A large fraction of anthropogenic climate change
resulting from CO2 emissions is irreversible on a
multi-century to millennial time scale, except in the
case of a large net removal of CO2 from the atmosphere
over a sustained period. Surface temperatures will remain
approximately constant at elevated levels for many
centuries after a complete cessation of net anthropogenic
CO2 emissions. Due to the long time scales of heat
transfer from the ocean surface to depth, ocean warming
will continue for centuries. Depending on the scenario,
about 15 to 40% of emitted CO2 will remain in the
atmosphere longer than 1,000 years.
IPCC AR 5 (2013)
3. A large fraction of anthropogenic climate change resulting
from CO2 emissions is irreversible on a multi-century to
millennial time scale, except in the case of a large net
removal of CO2 from the atmosphere over a sustained
period. Surface temperatures will remain approximately
constant at elevated levels for many centuries after a
complete cessation of net anthropogenic CO2 emissions.
Due to the long time scales of heat transfer from the
ocean surface to depth, ocean warming will continue for
centuries. Depending on the scenario, about 15 to 40% of
emitted CO2 will remain in the atmosphere longer than
1,000 years.
IPCC AR 5 (2013)
5. Grasses allocate a high proportion of their photosynthate
belowground to roots greater soil carbon pools
6. Grasslands are geographically expansive
The majority of grasslands are degraded
30% of global land surface area
30% of US land area
23 million hectares in California (40-50 % of the land area)
7. At a rate of 0.5 Mg C ha-1 y-1
= 21 MMT CO2e/y
Units:
Mg = Metric ton
MMT= Million metric tons
CO2e = CO2 equivalents
At a rate of 1 Mg C ha-1 y-1
= 42 MMT CO2e/y
Using half of California’s grasslands
8. At a rate of 0.5 Mg C ha-1 y-1
= 21 MMT CO2e y-1
Units:
Mg = Metric ton
MMT= Million metric tons
CO2e = CO2 equivalents
Emissions data: CA GHG Inventory 2013
At a rate of 1 Mg C ha-1 y-1
= 42 MMT CO2e y-1
Using half of California’s grasslands
•Livestock (enteric fermentation)
~ 12 MMT CO2e y-1
•Commercial/residential
~ 43 MMT CO2e y-1
•Electrical generation (in state)
~50 MMT CO2e y-1
9. Amendments of livestock manure increased soil
carbon by 50 Mg C ha-1 in the top meter of soil
Not amended Amended
0
100
200
300
SoilCarbon(MgCha-1)
From Silver et al. In prepAnalysis of 35 fields (1050 samples) from Marin and Sonoma Counties
10. 0 10 20 30
Agricultural Soil
Management
Stationary Combustion
Mobile Combustion
Manure Management
Nitric Acid Production
Wastewater Treatment
Composting
0 50 100 150 200
Enteric Fermentation
Natural Gas Systems
Landfills
Coal Mining
Manure Management
Petroleum Systems
Wastewater
Treatment
Rice Cultivation
Composting
Livestock manure is a large source of greenhouse gases
x10
U.S. Methane Emissions (MMT CO2e) U.S. Nitrous Oxide Emissions (MMT CO2e)
U.S. EPA EPA 430-R-15-004 2013; Owen and Silver 2015 Global Change Biology
12. One time application
Did not increase field
nitrous oxide and
methane emissions
Created a slow release
organic fertilizer
Composted organic matter
has much lower emissions
13. 0
500
1000
1500
2000
2500
3000
3500
4000
2008 2009 2010 2011 2012
Soilorganiccarbon(gm-2)
A single application of compost increased both plant (forage)
production and soil carbon stocks for multiple years
AbovegroundNetPrimaryProduction(gm-2)
control compost
0
250
500
750
1000
1 2 3 4
Year
2009 2010 2011 2012
Ryals and Silver 2013, Ryals et al. 2015, Silver et al. in prep.
Year
14. 9/08 9/09 9/10 9/11
Date
Changeinsoilmoisture(%) Compost-treated soils had higher soil moisture
during the growing season in most plots
Ryals and Silver 2013 Ecological Applications
15. Model results suggest that carbon gains persist for
approximately 100 years
Ryals et al. 2015 Ecological Applications
16. GHG Mitigation
GHG Emissions
Compost Manure Fertilizer
-40
-30
-20
-10
0
10
20
30
Globalwarmingpotential(MMTCO2e)
Net
Life cycle assessment suggests high climate change
mitigation potential even at small scales
Emissions from livestock
Redrawn from DeLonge et al. 2013
Applied to 5% of CA Rangeland
Emissions from household
energy use
17. 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
18. Science Action
It is critical that carbon sequestration be included in
climate action planning at all levels
Agriculture is poised to contribute to climate change
mitigation; this is supported by science
Soil is a resource that can facilitate both mitigation
and adaptation; more research is needed in this area;
we are just scratching the surface
Creative solutions may cross sectors, posing new
regulatory challenges, and new opportunities
19. Ryals et al. 2016
Compost amendments did not significantly change plant diversity
Notes de l'éditeur
What many people don’t realize however is that
Grasslands are a great place to try to sequester C in soils because grasses put a lot of their energy (and thus C) below ground in roots. They do this because they need to search for water and nutrients in the seasonally dry climates where they grow. From UK Agriculture: “Grassland is the UK's most important crop by area covering just over half of the entire UK landmass - nearly three times as great as all other crops combined.
The whole of the UK (24 million ha) is just a little larger than the grassland area in the state of CA (23 million ha) where I am from.
CA rangelands roughly store about 1-2 Pg C in the top meter;
There is considerable potential to offset some of California’s energy use with soil C sequestration
There is considerable potential to offset some of California’s energy use with soil C sequestration
Sites with and without organic matter amendments.
Note composting has lower emissions
Using a range of estimates from the EPA on the low end and a value from the DICE model by Moore and Diaz published last year. This gives us values of ~450-2700 million US$ last year is the social costs of C emissions from livestock manure in CA. The $$ saved over 25% of CA using this approach are ~780 to 4600 million US$.