Abstract: A panel comprising at least one layer of thermoformable plastics material having separate regions of different thickness, is obtained by a method comprising the steps of: extruding of a sheet of plastics material with the addition to the said material of an expansion agent, the extrusion being conducted in conditions such as to avoid expansion of the material or to cause only partial expansion thereof; heating the thus-obtained sheet to a temperature such as to cause post expansion of the material; and thermoforming the sheet in a thermoforming cavity of complementary shape to the desired panel so that the thermoformed panel produced has in the regions of greater thickness an expanded cellular structure where the material has a lower density than the density of the material in the regions of lesser thickness.

Abstract: A panel comprising at least one layer of thermoformable plastics material having separate regions of different thickness, is obtained by a method comprising the steps of:

Abstract: The urban waste is crushed (2) to dimensions no greater than 5 cm and intimately mixed (5) with a aqueous suspension of biological sludge preconditioned at a temperature of from 40 to 100.degree. C. (6) and having a dry content of from 3 to 30% by weight, the suspension thus obtained, inoculated with bacterial strains (7) which can effect anaerobic break-down, being supplied to a closed fermentation cell (11, 12, 13) operated as a fluidised bed and being kept under anaerobic fermentation conditions in the cell until the emission of biogas has effectively ceased. In the fermentation cell the suspension percolates through filtration means constituted by a non-woven textile covering the walls and the base of the cell and the flow of percolated suspension is recycled to the cell. The filtration means also facilitate the separation of the biogas evolved.