The Crush - June 2020 - 1

Volume 47 Issue 6 June 2020


Vineyard Carbon Footprints and GHG Emissions
By Ted Rieger
Vineyard carbon footprints and activities that emit greenhouse
gases (GHGs) are increasingly being monitored and evaluated
by California grape growers as a component of sustainability
certification programs and as mitigation measures to reduce
impacts related to global warming and climate change. While
ag operations in general contribute a lower percentage of
GHGs (about 8 percent of annual California totals) in relation to
other economic sectors, vineyard management practices can be
modified to further reduce GHG emissions impacts and improve
carbon sequestration.
A GHG is any gas in the atmosphere that absorbs and re-emits
heat and keeps the Earth's atmosphere warmer. The main GHGs
are water vapor, carbon dioxide, methane, nitrous oxide and
ozone. The following GHGs are most commonly associated with
ag operations.
*	 Carbon dioxide (CO2) is produced by burning carbon, fossil
fuels and organic compounds. Burning of fossil fuels though
on-farm uses of tractors, machinery and irrigation pumps
contributes to CO2 emissions. Fossil fuels that contribute to
CO2 emissions (in order from higher to lower amounts) are
diesel, gasoline, propane and natural gas. CO2 emissions can
also be offset in ag operations as CO2 is absorbed by plants
during photosynthesis - grapevines, cover crops, hedgerows
and native vegetation.
* Nitrous oxide (N2O) is an atmospheric pollutant produced
from croplands and grazing lands by soil microbes through
nitrification and denitrification. N2O emissions can
be influenced by nitrogen fertilization
practices related to fertilizer type,
application rate, placement, and timing
related to soil moisture, irrigation and

Barley cover crop and GHG/carbon monitoring instruments for research trials at
UC Oakville Station. Photo: Kaan Kurtural

plant growth. N2O has a significantly higher global warming
potential (GWP) with one molecule equal to 298 GWP units
of CO2 (CO2 has 1 GWP unit per molecule). Agriculture
contributes 50 to 60 percent of California's annual N2O
production, making it a focus for mitigation.
* Methane (CH4) comes from natural sources such as wetlands,
animal digestion, and oil and gas production. Natural gas is
about 90 percent methane. CH4 has 25 GWP units.
The above three GHGs can also be emitted from ag soils under
certain conditions, and all three can be released from residue
burning. Ag management can mitigate GHG emissions in
two ways: 1) reducing sources of emissions and 2) offsetting
emissions by increasing the capacity for carbon uptake and
storage in soils or in biomass with carbon sequestration.
The COMET-Farm model was developed by the U.S. Department
of Agriculture (USDA) Natural Resources Conservation Service
(NRCS) and Colorado State University as a whole farm carbon


The Crush - June 2020

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