Units

The following units are typically used in the sequestration field in the U.S. and internationally:

• Converting between carbon dioxide (CO₂) and carbon (C) units
• Converting methane (CH₄) and nitrous oxide (N₂O) to equivalent CO₂ and C units
• Converting mass units (e.g., short tons, metric tons, teragrams)
• Converting area units between acres and hectares
  

Converting between carbon dioxide (CO₂) / carbon (C) units:

1 unit CO₂ = 0.2727 or 12/44 units C

1 unit carbon (C) = 3.6667 or 44/12 units carbon dioxide (CO₂)

Converting methane (CH₄) and nitrous oxide (N₂O) to equivalent CO₂ and C units:

Global Warming Potential (GWP) of CO₂ = 1

GWP of CH₄ = 21 (over 100-year time period according to IPCC Second Assessment Report)

GWP of N₂O = 310 (over 100-year time period according to IPCC Second Assessment Report)

1 unit CH₄ x 21 = 21 CO₂ Equivalents

EXAMPLE: (17 metric tons of CH₄)(21) = 357 metric tons of CO₂ Equivalents x 12/44 = 97 metric tons of Carbon Equivalents

1 unit N₂O x 310 = 310 CO₂ Equivalents

EXAMPLE: (55 metric tons of N₂O)(310) = 17,050 metric tons of CO₂ Equivalents x 12/44 = 4,650 metric tons of Carbon Equivalents

NOTE: Although the GWPs have been updated by the IPCC in the more recent Third Assessment Report (TAR), estimates of emissions presented throughout this Web site continue to use the GWPs from IPCC’s Second Assessment Report. The guidelines under which EPA’s Inventory was developed, the Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories and the UNFCCC reporting guidelines for national inventories were developed prior to the publication of the TAR. Therefore, to comply with international reporting standards under the UNFCCC, official emission estimates are reported by the United States using SAR GWP values.

Converting mass units (e.g., short tons, metric tons, teragrams)

1 metric ton = 1,000 kilograms (kg) = 2,204 lbs

1 short ton = 0.9072 metric tons = 2,000 lbs

1 Teragram (Tg) = 10¹² grams = 1 million (10⁶) metric tons

1 Petagram (Pg) = 10¹⁵ grams = 1 billion (10⁹) metric tons

1 Gigaton (Gt) = 1 billion (10⁹) metric tons

Converting area units between acres and hectares

1 acre = 0.4047 hectares (ha)

1 hectare (ha) = 2.471 acres

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