Biotechnology and Waste - Environmental Biotechnology: Theory and Application - page 203

a number of long established businesses in the Britain, the US 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. AC 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 traditional composting, since
a period of pre-composting permits the thermophilic inactivation of pathogens,
while secondary worm action offers a high quality product more rapidly.
There are many advantages to this method, most obviously in that it allows
for the input biowaste to undergo established sanitisation procedures without
detriment to the worms themselves, which are, as discussed previously, temper-
ature sensitive. A less commonly appreciated benefit of this approach is that the
period of initial composting significantly reduces worm ammonia exposure, to
which, again, they are very sensitive. However, as with so much of these com-
bined approaches, there is a need to manage the treatment conditions carefully
to produce the optimisation desired. There is evidence to suggest that a pre-
composting phase has a negative effect on worm growth and reproduction rates
(Frederickson et al ., 1994) which obviously represents a direct reduction in the
overall rate of worm biomass increase. Obviously this has an effect on the overall
rate of stabilisation and processing, particularly since it has been demonstrated
that the enhanced waste stabilisation achieved under worm treatment is only
attained under conditions of high resident worm biomass (Frederickson et al .,
1994). It seems reasonable to suggest, then, that to maximise the effectiveness
of the combined treatment approach, the initial composting period should be no
longer than the minimum necessary to bring about pathogen control of the input
biowaste. Though this represents the kind of compromise balancing act so typical
of much of environmental biotechnology, it is one which holds much promise.
The combination of AC with composting permits both enhanced stabilisation rate
and product quality, with the additional bonus that the volatile organic content
is also significantly reduced. It is also possible that the natural ability of worms
to accumulate various hazardous substances within their bodies will also have
implications for waste treatment, particularly if it proves possible to use them
deliberately to strip out particular contaminating chemicals.
AC is currently very clearly a minority technology in this role, but the potential
remains for it to play a role in the future biological treatment of waste, either as
a stand-alone or, as seems more likely, as part of an integrated suite of linked
processes. This seems particularly likely if the characteristically superior product
derived from this process can be shown to be consistent, since specialist materials
in the horticultural and gardening market generally tend to offer better returns.
However, only time will tell whether this will prove to be sufficient financial
incentive to offset the costs of production and encourage wider adoption of
the technology.