Phytotechnology and Photosynthesis - Environmental Biotechnology: Theory and Application - page 144

accomplish its goal. It may also have a need to be able to encourage localised
microbial growth.
One of the major advantages of phytotechnological interventions is their almost
universal approval from public and customer alike and a big part of the appeal
lies in the aesthetics. Healthy plants, often with flowers, make the site look more
attractive, and helps the whole project be much more readily accepted by people
who live or work nearby. However, the single biggest factor in its favour is that
plant-based processes are frequently considerably cheaper than rival systems, so
much so that sometimes they are the only economically possible method. Phy-
toremediation is a particularly good example of this, especially when substantial
areas of land are involved. The costs involved in cleaning up physically large
contamination can be enormous and for land on which the pollution is suitable
and accessible for phyto-treatment, the savings can be very great. Part of the rea-
son for this is that planting, sowing and harvesting the relevant plants requires
little more advanced technology or specialised equipment than is readily at the
disposal of the average farmer.
The varied nature of phytotechnology, as has already been outlined, makes any
attempt at formalisation inherently artificial. However, for the purposes of this
discussion, the topic will be considered in two general sections, purely on the
basis of whether the applications themselves represent largely aquatic or terrestrial
systems. The reader is urged to bear in mind that this is merely a convenience
and should be accorded no particular additional importance beyond that.
Terrestrial Phyto-Systems (TPS)
The importance of pollution, contaminated land and the increasing relevance
of bioremediation have been discussed in previous chapters. Phytoremediation
methods offer significant potential for certain applications and, additionally, per-
mit much larger sites to be restored than would generally be possible using more
traditional remediation technologies. The processes of photosynthesis described
earlier in this chapter are fundamental in driving what is effectively a solar-energy
driven, passive and un-engineered system and hence may be said to contribute
directly to the low cost of the approach.
A large range of species from different plant groups can be used, ranging
from pteridophyte ferns, to angiosperms like sunflowers, and poplar trees, which
employ a number of mechanisms to remove pollutants. There are over 400 differ-
ent species considered suitable for use as phytoremediators. Amongst these, some
hyper-accumulate contaminants within the plant biomass itself, which can sub-
sequently be harvested, others act as pumps or siphons, removing contaminants
from the soil before venting them into the atmosphere, while others enable the
biodegradation of relatively large organic molecules, like hydrocarbons derived
from crude oil. However, the technology is relatively new, only recently emerg-
ing from the development phase. The first steps toward practical bioremediation
using various plant-based methods really began with research in the early 1990s,