**1. Introduction**

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Environmental Science and Technology 37:3399-3404.

56 Environmental Risk Assessment of Soil Contamination

Xenobiotic and other toxic compounds from industrial activities are presently being accumu‐ lated in the ecosystems at an unsustainable rate. From an anthropocentric point of view such contamination is unsustainable because it threatens basic ecosystem functions and services that are necessary to maintain food security and provision of potable ground water. Further‐ more natural habitats for plants and animals are threatened. Thousands of chemical com‐ pounds in varying concentrations and compositions have contaminated a wide range of habitats [1]. These contaminated sites demand diverse strategies and development of new technologies that are efficient and cheap enough to make remediation feasible even in remote areas and where financial support is limited.

Soil remediation has been a developing field for several decades and a common assumption is that it is a sustainable industry but very often clean-ups demand vast amounts of energy and lead to severe physical damage to the landscape. Traditional remediation technologies include soil excavation and landfill disposal. Sustainable remediation technology has been defined as a *"remedy or combination of remedies whose net benefit on human health and the environ‐ ment is maximized through the careful use of limited resources"* [1]. Such technologies are only modestly implemented at present but new landfill legislations against "dig and dump" technologies can favour green solutions over chemical and energy-intensive techniques in the future [2].

Microorganisms have colonized some of the most extreme environments on the earth and some of them are efficient degraders of the pollutants that our industrial society produces. Biore‐ mediation is a technology that uses living organisms and their enzymes to degrade, remove

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or immobilize toxic compounds [3]. Bioremediation have been gaining terrain recently [1] and some authors predict a further increase as technological advances surmount the limitations that exist today.

In this chapter we briefly discuss how principles of ecological engineering in concurrence with the application of basic thermodynamic principles and kinetic modelling can provide useful tools for the development of energy conserving and economically feasible bioremediation projects. We further discuss the potential of organic waste materials and by-products in locally adapted soil bioremediation. Finally we present some illustrative cases of novel research on sustainable bioremediation for tropical developing countries and remote locations and discuss some promising fields of future research and possible future applications.
