Eli Carlisle, Dept. of Plant Sciences,
David R. Smart,
Dept. of Viticulture & Enology,
UC Davis
Joe Browde, California Sustainable
Winegrowing Alliance
Andrew Arnold, SureHarvest
ike many other agricultural and business sectors, the California grape and wine community is increasingly
interested in better understanding its “carbon footprint.”
A carbon footprint can be defined as a comprehensive
measure of the amount of greenhouse gases (GHGs) produced and consumed, and is used to determine whether or not
individual operations are contributing to the increase of GHGs in the atmosphere and therefore global climatic
change.
Some vineyard operations, such as tractor driving, “produce” GHG carbon dioxide (CO2). The key agricultural sources
of atmospheric CO2 are the combustion of fossil fuels and soil management practices that increase decomposition of
soil organic matter.
Grape growing, however, also “consumes” CO2 through photosynthesis. For this reason and others,
agriculture including grape growing, is a significantly smaller source of CO2 than transportation and other industries.
However, assessing a carbon footprint for an individual vineyard is somewhat more complex.
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Agricultural activities emit two additional GHGs
— nitrous oxide (N2O) and methane (CH4). The main GHG produced
by viticulture is likely N2O. It is generally believed that the CH4 footprint
in vineyards is insignificant.
The importance of N2O comes from its strong ability to act as a GHG. N2O is roughly 300 times more effective than CO2 at
trapping heat in the Earth’s atmosphere, so a small amount of N2O can cause as much global warming as a very large
amount of CO2.
Non-CO2 emissions
To calculate a carbon footprint, according to the protocol outlined by the International Panel on Climate Change (IPCC),
requires the assessment of all GHGs combined into a cumulative, representative
number, where non CO2
emissions such as CH4 and N2O are converted
to CO2 equivalents. For example,this is done for N2O by multiplying the amount of emissions by its global warming
potential (how much better it is attrapping heat than CO2,). One kg of N2O = 300 kg CO2.
Carbon Sequestration
Besides being a source of GHGs, agricultural systems can help offset emissions by the long-term
storage of carbon in vegetative structures and soils. This process is referred to as carbon
sequestration, and, according to some models, perennial crops like
vineyards and orchards are expected to sequester more carbon than annual crops.
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On the Ramal Vineyard Estate at Buena Vista Carneros Winery (Sonoma, CA), tillage is done in alternate tractor rows.
In November, cultivated tractor rows are seeded with selected cover crops to enhance soil building, increase organic
matter, and host beneficial insects. Alternate rows that are not cultivated are mowed twice during the growing season.
Strip spray, under the vines, is applied with soft herbicides, to minimize the application of preemergent
sprays. Nonchemical
alternatives are being considered to remove weeds from under the vines mechanically. Weed control also involves
using ancient hoeing/shoveling technique as an alternate. (Photo © Erik Almas)
Vineyard establishment and management
practices can differentiall influence the amounts and relative proportions of vineyard GHG emissions
and carbon sequestration and, thus, can be adapted to reduce emissions
and increase carbon storage to achieve a more desirable balance.
Vineyard Practices and Carbon Footprints
The relationship between vineyard management practices and carbon footprints is reviewed below. For some practices,
GHG and carbon sequestration
calculation tools can be used to indicate how farming practices influence
the vineyard carbon footprint.
The U.S. Department of Agriculture Voluntary Reporting Carbon Management
Tool ( website), (COMETVR),
shows the carbon equivalent emissions saved from reducing or eliminating tillage in annual crops.
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