Practising Sustainable Development

Putting the process into operation
Unfortunately Immler does not reveal any practical way of putting the process towards sustainability into operation. A start in the political arena seems too remote from the ultimate target urgently to be reached. Economics seem one step closer to the target but a disadvantage of Immler's theory is its strong reliance on a well ordered and promising economy which is characteristic only of western countries leaving the developing world more or less out of play. Most effective in starting the process towards sustainability seems to be technological innovations. Unfortunately Immler is not very specific in this field and he only indirectly hints at the application of renewable energy and the dangers of bio- and especially gene- technology. Therefore it seems obvious to increase the exploitation of gee-thermal and of solar energy in the different forms manifested: direct radiation, bio-, wind-, and hydro- energy. For example the solar energy hitting the earth is 200,000 times the total electric power actually installed. For this reason, in my opinion (see Fig. 2), a sustainable development should be very much concentrated on the application of this sustainable energy

Regeneration of nature by reversing pollution
It is especiallyinteresting to increase the input of these renewable energy sources in the field of preventing of the actual scattering of essential non-renewable materials as wastes into the environment. As presented in Fig. 2 this closely approaches Immler's regeneration of nature. From the foregoing, it appears that the sharing between North and South of both the knowledge to solve and the concern about the consequences of environmental problems may remove the blocking of the way to any form of Good Life. It certainly seems to constitute the most effective and firm base for a start of the process towards ecological sustainability. Reviewing in this respect the essential characteristics for processes to sustainable developments on a global scale, the leather sector is an interesting field of action. The making of leather is one of the first forms of industrial activities taken up by developing countries and since leatder is largely derived fromrenewable resources and improvements to more clever technologies can strongly contribute to a fundamental start of the development of sustainable economies in these countries.

The unsustainabilities of the leather world
To simplify the discussions only the globally most relevant form of leather making by chrome tanning of bovine hides is here considered. In a way the making of leather can be described as a form of sustainable environmental technology. The stabilisation of wastes from the meat industry (hides of animals) by tanning with wastes from the chemical industries (trivalent chromium as a residue of chromate-based oxidation processes) results in a high quality end product which fulfills a primary need of society. However, this simplistic view masks serious unsustainabilities.

Unsustainabilities of the chrome leather making process
Firstly, collagen, the constituent from which leather can be made, represents onby 30% of the animal hides processed; moreover not all chrome used as a tanning material is waste from chemical processes. Secondly, the making of leather comprises much more than the hydro- thermal stabilisation ofcollagen by means of chrome tanning. Unfortunately during the integral leather making process about 50% of the collagen and 85% of the chemicals applied are emitted as wastes (UNIDO 1997, "Mass Balance in Leather Processing"). Apart from these process, technological inefficiencies there are a number of logistical features which also contribute to unsustainabilities.

Logistic unsustainabilities
The existing leather trade is active in shipping hides, semi processed leather, leather and leather products all overthe world. These activities are mostly aimed at maximising financial revenues rather than creating added value. In an analogous way, governmental politics are sometimes aimed only at political revenues, when situating industries and promoting processes at locations which are unable to cope with the inevitable environmental consequences. For instance, it seems not a clever and sustainable procedure to ship hides containing about 20% curing salt from the USA to provide labour to a chrome tannery in an arid area inland area of an Asian country. Such transport of waste is a waste of transport and leads salt emission problems which cause irreversible forms of soil deterioration. If it is necessary to transport such wastes at all, the processing should at least take place near the port of entry of the receiving country, with access to open sea in which to emit the curing salt after removal. It is, of course, more clever to process hides (without salt-curing) to a semi- product, with a high content of collagen, near to or at the meat factory. This reduces transport labour and energy, prevents environmental problems and offers labour of higher quality and added value to the people of the receiving country. Although most of these ideas are not new, the instigation of innovations in this field is slow due their financial and economic consequences and the necessary international co-ordination and governmental policy making involved. As previously said, the most speedy way to solve unsustainabilities seems to be the sharing of cleverness between North and South. Most fortunately this does not require unequivocal opinions about concepts of the Good Life and the Good Economy. The development and implementation of the Integral Clean Chrome Leather Technology (ICCLT) can be considered as a representative example in this field.

The Sustainable Leatherworld within REACH?
The Integral Clean Chrome Leather Technology described implies a practical step into the direction of sustainable leather technology. However, to realise the Sustainable Leather World, additional measures remain necessary. It is common practice to seek under such conditions the solutions in the development of revolutionary new technologies. However, considering Covington's Wilson Memorial Lecture 1998 on New Tannages for the New Millennium it is clear that no new technology is to be expected which can compete with chrome tanning when aiming at sufficient hydrothermal stability and the strongly preferred typical quality aspect of mineral tannage. Moreover the available high exhaustion chrome tanning technologies and the exclusively small amount of tanning material needed (2.5% Cr) for a sufficient crosslinking of collagen will work out in a very positive way when comparing the results of lifecycle analyses of chrome leather and its alternatives.

For this reason contributions to a sustainable leather world have to be sought in another way; first by the trading of collagen in a more purified form. This can be established by concentrating beamhouse processes near to the place of slaughtering and pretanning the hides by means of glutaraldehyde before transport. As described by Heidemann'3, with relatively small amounts of glutaraldehyde and at nearly neutral conditions a strong fungal protection of the collagen can be obtained. Moreover, such pretanning can produce sufficient hydro- thermal stability to execute the splitting and shaving operations and enables a high uptake of chrome during main tanning. In this way the chrome consumption is minimised and the emission of solid and aqueous chrome containing wastes is prevented.

The second way by which contributions to a sustainable leather would have to be sought is by chrome-free retanning. Actually one of the most important sources of chrome emission is the retanning of leather by means of chrome. As revealed by Wolf and Magerkurth these type of emissions can be prevented by application of acrylate polymers in retanning. Instead of the addition of chrome and the increase of chrome emission such polymers effectively replace chrome as a retanning agent. Moreover, these polymers increase the bonding of the chrome present and in this way reduce the washing out of chrome.

The third way is by anaerobic digestion of organic solid wastes. This is an effective way to get rid of organic solids originating from fleshing, shaving and trimming. However such digestion requires milling or liquefaction of these wastes before they can be ~ into a reactor. As reported by Ravindranath", biological liquefaction can be attained in an easy practicable way by contacting the solid wastes at elevated pH with effluents of anaerobic reactors which by their nature contain the enzymes to degrade the protein matrix. After liquefaction and feeding into a UASB reactor the wastes are digested to carbon dioxide, methane and ammonia. A sustainable Leather World in the strict sense of the wording will remain an unattainable ideal. However, this ideal can be approached closely by combining the concept of the Integral Clean Chrome Leather Technology with rigorous applications of existing technologies on clean collagen trading, chrome free splitting, shaving and retanning and the anaerobic digestion of solid organic wastes in one viable chrome leather technology.

Conclusion
Integral Clean Chrome Leather Technology, combining the developed in-tannery, add-on and external environmental technology allows a production of chrome leather at a low environmental impact by application of self sustainable treatment technologies and without a prohibitive increase of treatment costs. The development of ICCLT demonstrates the feasibility of a sustainable co-operation between scientists from Europe and India in the field of clean technology with excellent perspectives for an effective implementation in developed as well as in developing countries. The exchange and joint building and implementation of the essential expertise constitute a first phase in the way to a sustainable (leather) world. A more rigorous and clever implementation on a global scale of available technologies may enable a close approach to the ideal of a Sustainable Leather World.  

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