Biotechnology for Sustainability: Achievements, Challenges and Perspectives

Biotech Sustainability (2017)
Bioremediation: A Biotechnology Tool for Sustainability
Chandra et al.
Figure 2: Ex-situ bioremediation by composting.
promising. The principles behind this are
relatively simple and related to those
involved in traditional composting
(Figure 2 summarizes composting as a
basic Ex-situ bioremediation process). In
general, vermicomposting consists of 4
major phases: Phase I: Collection of the
waste, separation of metal, glass,
ceramics etc. from the organic waste, and
storage of the organic waste.
Phase II: Earthworm beds are
maintained and the earthworms are fed
with the organic waste.
Phase III: After the organic waste
has been worked over by the earthworms,
the vermicompost, cocoons, earthworms
and the undigested material are separated.
Phase IV: Packaging of the
vermicompost and reintroduction of
undigested material into the vermipits.
Certain species of earthworms
(Eisenia fetida, E. Andrei, Lumbricus
rubellus, L. hortensis, L. terristris etc.)
can consume organic residues very
rapidly and fragment them into much
finer particles by passing them through a
grinding gizzard, an organ that all
earthworms possess. The earthworms
derive their nourishment from the
microorganisms that grow upon the
organic materials. At the same time they
promote further microbial activity in the
residues so that the faecal matter or casts
that they produce are much more
fragmented. During this process, the
important plant nutrients in the organic
material particularly nitrogen,
phosphorus, potassium and calcium are
released and converted into forms that are
much more soluble and available to plants
than those in the parent compounds.
Worms can digest waste several times
their own weight each day.
4.5. Bioventing
Bioventing is a process of
stimulating the natural in situ
biodegradation of contaminants in soil by
providing air or oxygen to existing soil
microorganisms. Bioventing uses low air
flow rates to provide only enough oxygen
to sustain microbial activity in the vadose
zone (Hinchee, 1994). This is an on-site
ISBN: 978-967-14475-3-6; eISBN: 978-967-14475-2-9 403