Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
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SEPTEMBER/OCTOBER 2009
GRAPEGROWING
GHG estimates from combustion of fossil fuels
  • Diesel produces 12 kg CO2 equivalents (CO2 + N2O + CH4)/gallon
  • Gasoline produces 10.5 kg CO2 equivalents/gallon
  • Propane produces 8.5 kg CO2 equivalents/gallon
  • Natural gas produces 1.5 kg CO2 equivalents/meter3
Comparative GHG impact from vineyard nitrogen management practices

Synthetic Fertilizers (CAN, UAN, ammonium nitrate, other nitrate fertilizers, etc.)

  • GHG released during manufacturing (also applies to pesticides)
  • Small percentage directly lost as N2O onsite (currently thought to be about 1%)
  • Small percentage indirectly lost offsite through leaching/volatilization to NH3 followed by conversion to N2O (currently thought to be roughly 0.3%)
  • Potentially higher rate of leaching than organic fertilizers

Organic Fertilizers and Additives(green manure, compost, winerywastes, etc.)

  • Small percentage lost directly as N2O onsite
  • Small percentage indirectly lost offsite through leaching/volatilization to NH3 followed by possible conversion to N2O
  • Potentially lower leaching rate than synthetic fertilizers
  • Higher rate of volatilization than synthetic fertilizers, in some cases
  • More GHG produced by fuel use during tractor operations to apply manures than by fuel use during fertigation
  • Effective way to sustainably reduce synthetic fertilizer inputs and recycle winery waste
  • Good way to build soil organic matter and thus increase carbon sequestration
  • GHG cost of compost and manure transport can be high unless generated onsite

Legume Cover Crops

  • Small, but unknown percentage probably lost directly as N2O
  • Can decrease between row leaching rate and better retain nitrogen in soil
  • Good way to build soil organic matter and thus increase carbon sequestration
  • Not the most efficient way to provide nitrogen to vines
Another useful tool is the International Wine Industry Greenhouse GasProtocol and Accounting Tool (website), developed by Wine Institute and international partner organizations,which allows the calculation of estimated vineyard and winery GHG emissions.
Because these tools are in development, and impacts of sitespecific factors such as soil type, climate, rootstock, grape variety, and vineyard ageon GHG emissions are not fully understood, it currently is not possible to definitively evaluate the emissions forevery management practice.
However, use of the tools provides understanding about how carbon accounting works. Nevertheless, a number of vineyard activities clearly affect GHG emissions, for which current understandings and mitigation tactics are described below.
Fossil Fuel Combustion
Combustion of fossil fuels during the operation of tractors, ATVs, irrigation pumps, and other farm equipment often constitutes a large source of the vineyard GHG footprint. Different fossil fuels are associated with different amounts of GHGs.
However, all fossil fuels, including cleaner burning natural gas, combust to produce significant amounts of CO2 and variable quantities of other GHGs like N2O.
Although it has a greater energy content per unit volume, diesel produces more CO2 and N2O than gasoline, natural gas, or propane. Reducingfuel usage is one of the most obviousand effective ways to reduce the vineyard GHG footprint. Any reduction intractor passes, for example, diminishesthe carbon footprint.
Nitrogen Fertilizer applications
Another important source of vineyard GHG emissions is the use of nitrogen fertilizers. When any nitrogen is added to soil, some of the applied nitrogen can be converted to N2O. This can happen to any nitrogen containing additive including synthetic fertilizers (nitrate and ammonium) and organic materials (green manures and pomace).
All N2O production associated with vineyards results from soil microbes using the nitrogen instead of the vines. Moreover, some added nitrogen can leach into ground water and subsequently be converted to N2O. Minimizing N2O emissions may be challenging.
Comparative GHG impact from tractor-row tillage systems

Conventional Tillage (less than30% of crop residues left on surfaceafter tillage)

  • Frequent tillage (more than one or two times per year) releases more CO2 by exposing newly formed organic matter to microbial decomposition
  • Potentially increased loss of organic matter to erosion
  • Decreased capacity of soil to store carbon
  • Generally less carbon entering soil organic matter compared with other tillage systems
  • Possibly greater consumption of fossil fuel for tractor operations, resulting in more GHG emissions

Conservation/Reduced Tillage(more than 30% of crop residuesleft on soil surface)

  • Fewer tillage passes (1 pass per year or even less under certain conditions) releases less CO2 due to slowed organic matter decomposition
  • Decreased loss of organic matter to erosion
  • Increased ability of soil to store carbon
  • Generally more carbon enters soil organic matter than with conventional tillage
  • Often associated with cover cropping which also enhances soil carbon storage
  • Possibly less GHG emissions associated with tractor operations

No Tillage (no disturbance of soil surface)

  • No GHG emission from tractor tillage operations
  • Increased ability of soil to store carbon
  • Soil aggregates are not broken up, protecting organic matter from microbial consumption
  • Greatest rate of carbon entering soil organic matter from row vegetation
  • Cover crops often used, including leguminous plants that supply nitrogen and can lower synthetic nitrogen fertilizer needs
  • Depending on sitespecific factors, increased soil carbon can sometimes lead to higher emissions of the more potent N2O, which may counteract some benefit from carbon sequestration
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