Agriculture Reference
In-Depth Information
manure from 25 farmers, and then trucks it back again in the form of wet digested residue
(six per cent dry matter), with its nutrient content boosted by the food waste. The biggest
cost of the operation is transport, involving 27 deliveries by 20-tonne lorries every week-
day. The plant is barely profitable, and would make a substantial loss were it not for the
gate fees that can be charged for accepting the food waste that can no longer be recycled
profitably to pigs.
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Profit aside, a great many solutions are technically possible and these waste problems
are also being addressed by people with an urban perspective. The German technological
city of Braunschweig (population 245,000), for example, has plans to grow biomass maize
on a dedicated 1500 hectare farm, turn it into gas in an on-site anaerobic digester and pipe
it 12 miles into town. In return Braunschweig will pipe back its waste water for irrigation.
This sounds like a raw deal for the countryside, which ought to be getting the sewage nu-
trients back as well. And a distance of 12 miles does not break the bounds of Günther's
ruralized regions. But it is easy to see how advocates of large cities and empty countrysides
- those who look to rural biomass to pay for the carbon excesses of an urban lifestyle -
could set about devising schemes involving tens of thousands of acres of biomass maize or
Miscanthus
, and pipelines ferrying the diluted waste nutrients of cities much bigger than
Braunschweig fifty miles or more out into their hinterland.
Meanwhile, chemical and waste disposal firms who recognize 'the problems that have
risen as a result of livestock intensification' have no intention of de-intensifying. On the
contrary they see these problems as an opportunity to devise even more ingenious tech-
nofixes, and for the last decade they have been researching ways to extract chemical fer-
tilizer from biomass. SBN, the owner of the largest sewage incineration plant in Europe, is
working on a project euphemistically called SUSAN, designed to extract phosphorus and
eliminate heavy metals from the ash of incinerated sewage sludge. Another process, deve-
loped by the US Department of Agriculture, removes first nitrogen and then phosphorus
from pig manure to produce chemical fertilizers, including bags of calcium phosphate. The
technology was developed 'to solve problems of excess nutrient land application due to
ate of this technology points out, the recovery of chemical phosphate:
is likely to be an economic option only in the case of large, geographically con-
centrated waste streams (sewage from urban areas, intensive livestock units). In rural
areas, agricultural sludge or manure spreading will probably always remain the best
option for recycling nutrients.
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In other words, if you don't want your poo turned into chemical fertilizer, move out to
the country.