Energy foundations and other thermo-active ground structures, energy wells, and pavement heating represent an innovative technology that contributes to environmental protection and provides substantial long-term cost savings and minimised maintenance. The paper focuses on earth-contact concrete elements that are already required for structural reasons, but which simultaneously work as heat exchangers. Absorber pipes filled with a heat carrier fluid are installed within conventional structural elements (piles, barrettes, diaphragm walls, basement slabs or walls, tunnel linings), forming the primary circuit of a geothermal energy system. The natural ground temperature is used as a heat source in winter and for cooling in summer. Hence no additional elements have to be installed below surface. The primary circuit is then connected via a heat pump to a secondary circuit within the building. ‘Free cooling’ may even run without a heat pump. The paper describes heat transfer in the ground, and between absorber fluid and concrete/soil. Temperature-induced changes of soil properties or of foundation behaviour are also discussed, and recommendations for design and operation are given. Pilot research projects and case histories bridge the gap between theory and practice, and special applications reveal the wide field of geothermal geotechnics.

Pseudomonas okovorans was grown in homogeneous media containing n-alkanoic acids, from formate to decanoate, as the sole carbon sources. Formation of intracellular poly(jI-hydroxyalkanoates) was observed only for hexanoate and the higher n-alkanoic acids. The maximum isolated polymer yields were approximately 30% of the cellular dry weight with growth on either octanoate or nonanoate. In most cases, the major repeating unit in the polymer had the same chain length as the n-alkanoic acid used for growth, but units with two carbon atoms less or more than the acid used as a carbon source were also generally present in the polyesters formed. Indeed, copolymers containing as many as six different types of ,-hydroxyalkanoate units were formed. The weight average molecular weights of the poly(Pi-hydroxyalkanoate) copolymers produced by P. oleovorans ranged from 90,000 to 370,000. In spite of the higher cell yields obtained with octanoate and nonanoate, the use of hexanoate and heptanoate yielded higher-molecular-weight polymers. These copolyesters represent an entirely new class of biodegradable thermoplastics.

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. In particular, four bacterial isolates (one isolate each of Arthrobacter sp., Janthinobacterium sp., Leifsonia sp., and Polaromonas sp.) were weathering associated. In comparison to what was observed in abiotic experiments, the presence of these strains caused a significant increase of granite dissolution (as measured by the release of Fe, Ca, K, Mg, and Mn). These most promising weathering-associated bacterial species exhibited four main features rendering them more efficient in mineral dissolution than the other investigated isolates: (i) a major part of their bacterial cells was attached to the granite surfaces and not suspended in solution, (ii) they secreted the largest amounts of oxalic acid, (iii) they lowered the pH of the solution, and (iv) they formed significant amounts of HCN. As far as we know, this is the first report showing that the combined action of oxalic acid and HCN appears to be associated with enhanced elemental release from granite, in particular of Fe. This suggests that extensive microbial colonization of the granite surfaces could play a crucial role in the initial soil formation in previously glaciated mountain areas.

Biological leaching of fly ash from municipal waste incineration by Aspergillus niger was examined in batch cultures and compared with chemical leaching. A. niger grew in the presence of up to 10% (w/v) of fly ash in the medium. In the presence of fly ash A. niger produced gluconate, whereas in its absence citrate was produced. Variation of the fly ash concentration in the growth medium (one-step process) resulted in different amounts of solubilized metals. A total of 3% (w/v) fly ash generally gave maximum extraction yields (in percent of the amount applied). In a two-step process A. niger first was cultivated in the growth medium, and subsequently the microbiologically produced citric acid was used as the leaching agent. At 6% (w/v) fly ash, the amounts of leached metals (leaching for 1 day) were 81% of Cd, 66% of Zn, 57% of Cu, 52% of Pb, 32% of Mn, 27% of Al, and less than 10% of Cr, Fe, and Ni, respectively. Chemical leaching with commercial citric acid of equal molarity was only slightly higher than microbial leaching. The environmental quality of the residues can be improved with respect to a re-use of these materials for construction purposes.

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