Agriculture Reference
In-Depth Information
Funnily enough, although the FAO view urbanization and nutrient loading to be a prob-
lem for livestock, they do not consider it to be so for humans, nor do they advocate that
people's habitations should be determined by the 'specific natural endowments of given
locations'. Yet human waste treatment in cities is problematic for precisely the same reas-
on as animal manure is in factory farms; too much of it is gathered in one place, result-
ing in unmanageable concentrations of phosphorus and nitrogen. And it too is conveyed to
one spot by being commingled with vast amounts of water and pumped along antiquated
sewage pipes. Leaking and contaminating ground water on the way, it gathers up heavy
metals from industrial sources, as well as an extra dose of phosphorus from the detergents
used in washing machines and dishwashers. No sooner is this soup all gathered in one place
than the water has to be separated off and cleaned up for release into the rivers or sea, bear-
ing with it a permissible proportion of the nutrients and contaminants, and leaving the rest
of the phosphorus, together with the chemical precipitate that removed it, in a pile of tox-
ic sludge, which in John Driver's words 'is of dubious agronomic value and presents its
own disposal problems'. 81 When Ralph Borsodi coined the term 'cross-hauling' to describe
similar consignments of apples or meat going in opposite directions, he failed to observe
that the most pervasive form of cross haulage is the transport of huge volumes of biomass
into urban concentrations and then back out again.
In the UK, some of this sludge is landfilled or incinerated, but since dumping at sea has
been banned, the majority is now put back to the land - though not where the nutrients
are most needed (since its use is not permitted for organic agriculture), nor in the correct
proportions. A further problem is that, en route, the sludge tends to lose nitrogen, which
is volatile and leaks into the atmosphere (from what I can decipher less than 20 per cent
of the N gets back to the land). 82 However it not only retains most of the phosphorus we
excrete, but also gains as much again from the addition of detergents and other industrial
effluents. 83 The result is that 'the ratio of P to N in the sludge is significantly higher than
that required by plants. Hence the practice of applying biosolids at rates based on the N
requirements of crops results in an excessive P supply relative to crop needs'. 84 The phos-
phorus ends up in a HEAP while the remaining land is not seeing its phosphorus recycled.
Admittedly, the volume of domestic sewage is only about a quarter of the volume of
livestock dung available in livestock units. 85 But then humans make up for that with all the
other organic detritus of civilization: the grey water, the effluents from food, drink and fibre
processing plants, the waste food, the hedge clippings and lawnmowings, the unrecyclable
scraps of paper and cardboard, the chewing gum, the dog poo, the cat litter, the old clothes
and shoes, the human hair and flakings of skin, the ash, and the dust and fluff that seems to
arrive from nowhere and fills up hoover bags - all the sort of stuff that over time buried the
successive incarnations of Troy under a layer of midden 50 foot deep.
 
 
 
 
 
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