Biotechnology and Waste 203extremely efficiently, effectively reprising their role in nature under these engi-
neered conditions.
Despite the predominance of redworms within vermiculture for the reasons
outlined, there have been a number of cases that have used true earthworm
species, with varying degrees of success. Thus, members of the generaLumbricus
andAmynthashave featured, but perhaps one of the most notable successes was
withPheretima elongata, a deep burrowing worm, native to India, which was
used to great effect as part of the Bombay plague prevention project, which
was founded in 1994 in response to an earlier outbreak of the disease. The
growing amount of waste in the city had been strongly implicated in attracting
and harbouring the vector rats. The use of vermiculture proved very effective in
reducing the biowaste problem (Menon 1994) and hence was seen as a major
preventative measure against a recurrence of the plague.
The use of worms to break down waste is not a particularly novel idea, though
like many aspects of environmental biotechnology, it frequently seems to fall first
in and then out of favour on a fairly regular basis. The advantages of worm-based
biowaste treatment are fairly easy to see. In the first instance, vermiculture offers
a high potential volumetric reduction, often exceeding 70% while producing a
well-stabilised final product. Secondly, this product itself is rich in potassium,
nitrogen, phosphorous and other minerals, which is presented in an ideal form
for plant uptake, and hence represents a high fertiliser value. The market for
this product has already been successfully established in some parts of the world
and many others seem set to follow. This is an important issue, as it has been
estimated that for every one tonne of biowaste deposited on the bed, around half
a tonne of worm casts is produced (Denham 1996).
Finally, the rapid growth potential of worms under idealised conditions has
the potential to provide a harvestable biomass resource, typically either as seed
populations for other vermiculture operations or for direct sale into the fishing
market. The reputation of the bait outlet has been tarnished in the light of various
spectacular collapses, most notably the Californian pyramid franchise back in
the 1970s and other similar operations in the UK more recently. Often aimed
at farmers seeking diversification ventures, it is unlikely that worm production
will truly be the salvation for all of them. However, the fact remains that there
are a number of long-established businesses in Britain, the USA and elsewhere
successfully trading in live worms for various purposes.
The sequential combination of various approaches into treatment trains has
become one of the major themes of environmental biotechnology over recent
years. Annelidic conversion has particular potential for use in this way and this
may prove of increasing importance within the waste management industry in
the future. There is a particularly logical fit between this method and tradi-
tional composting, since a period of precomposting permits the thermophilic
inactivation of pathogens, while secondary worm action offers a high quality
product more rapidly.