Pollution and Pollution Control - Environmental Biotechnology: Theory and Application - page 78

Bio-stoning has been widely adopted to produce 'stone-washed' denim, with
enzymes being used to fade the fabric rather than the original pumice stone
method, which had a higher water consumption and caused abrasion to the denim.
However, perhaps the most fitting example of environmental biotechnology in
the textile industry, though not really in a 'clean technology' role, is the incor-
poration of adsorbers and microbes within a geotextile produced for use in land
management around railways. Soaking up and subsequently biodegrading diesel
and grease, the textile directly reduces ground pollution, while also providing
safer working conditions for track maintenance gangs and reducing the risk of fire.
Leather industry
The leather industry has a lengthy history of using enzymes. In the bating process,
residual hair and epidermis, together with non-structural proteins and carbohy-
drates, are removed from the skins, leaving the hide clean, smooth and soft.
Traditionally, pancreatic enzymes were employed. Moreover, something in the
region of 60% of the input raw materials in leather manufacturing ultimately
ends up being discarded and enzyme additions have long been used to help man-
age this waste. Advances in biotechnology, however, have seen the upsurge in
the use of microbially-derived biological catalysts, which are cheaper and easier
to produce, for the former applications and the possibility of converting waste
products into saleable commodities in the latter.
As well as these improvements on existing uses of biotechnology, new areas of
clean application are emerging for tanners. Chemical methods for unhairing hides
dissolve the hairs, making for efficient removal, but adding to the treatment cost,
and the environmental implications, of the effluents produced, which are of high
levels of COD and suspended solids. Combining chemical agents and biological
catalysts significantly lessens the process time while reducing the quantities of
water and chemicals used. The enzymes also help make intact hair recovery a
possibility, opening up the prospect of additional income from a current waste.
It has been estimated that, in the UK, for a yearly throughput of 400 000 hides,
enzymatic unhairing offers a reduction of around 2% of the total annual running
costs (BioWise, 2001). While this may not seem an enormous contribution, two
extra factors must be borne in mind. Firstly, the leather industry is very competi-
tive and, secondly, as effluent treatment becomes increasingly more regulated and
expensive, the use of clean manufacturing biotechnology will inevitably make
that margin greater.
Degreasing procedures are another area where biotechnological advances can
benefit both production and the environment, since conventional treatments pro-
duce both airborne VOCs and surfactants. The use of enzymes in this role not
only gives better results, with a more consistent quality, better final colour and
superior dye uptake, but also considerably reduces VOC and surfactant levels.
The leather industry is also one of the places where biosensors may have a role