Agriculture Reference
In-Depth Information
and
to the farmers market, and consequently, more carbon
emissions. The relationship between food and carbon does
not depend solely on how food is produced, but also how it is
purchased.
Does Organic Food Have a Lower Carbon Footprint?
It depends. Carbon emissions are influenced by the type of
nitrogen fertilizer a farm uses. Organic advocates are quick
to point out that they do not use chemical nitrogen fertilizer,
and thereby avoid one large source of carbon emissions. Many
organic farmers acquire their fertilizer from livestock manure,
though, and many of these animals were fed forage that was
fertilized with chemical fertilizers. If this is the norm, then
organic farmers are reliant on chemical fertilizers but are
using it in a very inefficient manner that might increase the
carbon footprint of their food. Manure and human compost—
two sources of organic manure—both emit carbon as they are
stored, and these emission rates are rather large.
An advantage of organic fertilizer is its ability to sequester
carbon in the soil. Fertilizing a field with manure, compost, or
cover crops doesn't just add the three key nutrients of nitro-
gen, phosphorus, and potassium, but also increases the carbon
content of the soil. Such fertilizers are not strictly reserved for
organic production, though, and there are many farms raising
conventional crops using livestock manure. Still, most con-
ventional farms do not use organic fertilizer, while all organic
farms do. If a heavily farmed field low in organic matter is con-
verted to organic production, carbon will be extracted from
the atmosphere and stored in the soil, thereby reducing the
carbon footprint of organic food. The rate at which carbon is
sequestered in the soil is highly uncertain, though, and causes
considerable uncertainty in carbon footprint measurements.
Although organic producers may argue otherwise, organic
farming is less productive (this is discussed in detail in
another chapter). Organic farmers, by definition, have a
