NEWS
Sources of anthropogenic methane pro-
duction:
• Gas and coal mining / Natural gas
– 19%
• Enteric fermentation (ruminants) –
16%
• Rice cultivation – 12%
• Biomass burning (veld fires) – 8%
• Landfills (dumping sites) – 6%
• Animal waste (including manure) –
5%
A simple calculation can be made using
this information. Ruminants contribute
21% of anthropogenic methane pro-
duction (16% from fermentation and 5%
from waste). However, methane forms
only 18% of GHG, and 21% of 18% is
less than 4%. Thus, the contribution of
ruminants to GHG is less than 4%.
CO 2 , but its atmospheric lifetime is 12
years, compared to the 100 year to 200
year lifetime of CO 2 . Although it has a
larger effect, the duration of the effect
is much shorter. This is a frequently ig-
nored aspect.
It is also important to ask the question,
what will happen to the vegetation if it
is not consumed by productive (meat,
milk, fibre) ruminants? There are three
possibilities:
•
•
•
It should, however, be noted that the
global warming potential of CH 4 is ap-
proximately 23 times more than that of
It can be consumed by other ani-
mals that will also emit CH 4
It can burn and produce CO 2 that is
released into the atmosphere with
an atmospheric lifetime of 100 years
to 200 years
It can rot and produce Nitrate gases
with a global warming potential of
approximately 300 times more than
that of CO 2 .
Livestock production and water usage
The water footprint or the amount of
water required to produce 1kg of prod-
uct is of relevance. Some of the as-
sumptions on which published figures
are based, are debatable. For example,
in one calculation where it is claimed
that the water requirement is 15 500 L/
kg beef, it is assumed that it takes three
years to produce 200kg of boneless
beef.
In the estimate, only 155 L of water were
calculated for drinking, cleaning and
post farm gate activities; the remainder
was accounted for by irrigation of the
crops used for cattle feed and the rain
that fell on the property. The estimates
of water utilised for 1 kg pork (4 800 L),
1 kg chicken (3 900 L) and 1 L milk (1
000 L) also appear extreme. These fig-
ures have been widely quoted by anti-
livestock activists. In studies with more
Figure 1: Livestock grazing on rangeland
33
Grassroots
Vol 19
No 1
March 2019