Facts and Myths of Feeding the World with Organic Farming Methods - Principles of Sustainable Soil Management in Agroecosystems - page 100

Air and water
pollution,
ecological
feedback
to disease
Crop yields,
nutrition,
health benefits
of fossil fuels

Effects on
public health

Net public
health benefit

Human N fixation and use

FIGURE 4.3 Conceptual model of the overall net public health effects of increasing human
fixation and use of atmospheric N 2 . (From Townsend, A.R. et al., Ecol Environ 1:240-248,
20 03.)

up and what affect it has on the environment and public wellbeing. Galloway and
Cowling (2002) estimated that for every 100 kg of N fertilizer used for producing
crops, only 14 kg N was actually consumed by humans when they ate the products
directly, which would represent a vegetarian diet (Figure 4.4a). They further esti-
mated that if the cereals produced were fed to animals and the meat produced was
consumed by humans, only 4 of the 100 kg N added as fertilizer was actually con-
sumed by humans (Figure 4.4b).

(a)

N fertilizer
produced

N fertilizer
applied

N
in crop

N
harvested

N
in food

N
consumed

100 94 47 31 26 14

-6 -47 -16 -5 -12

(b)

N fertilizer
produced

N fertilizer
applied

N
in crop

N
in feed

N
in store

N
consumed

100 94 47 31 7 4

-6 -47 -16 -24 -3

FIGURE 4.4 Fate of N fertilizer produced by the Haber-Bosch process from the factory
to the mouth for (a) vegetarian diet and (b) carnivorous diet. (From Galloway, J.N., and E.B.
Cowling, Ambio 31:6 4 -71, 20 02.)