TECHNOLOGY FOCUS - POLYMERS - Preferred Polymer: The biodegradeable polyesters are preferably made from (a) aliphatic bifunctional alcohols, especially linear 2-10 C dialcohols such as ethanediol, hexanediol or (especially) butanediol and/or cycloaliphatic bifunctional alcohols, especially having 5 or 6 C in the cycloaliphatic ring, such as cyclohexanedimethanol, optionally partially or completely replaced by oligomeric polyols based on ethyleneglycol, propyleneglycol, tetrahydrofuran or copolymers with a mol. wt. of up to 4000, preferably up to 1000, and optionally small amounts of branched bifunctional alcohols, preferably 3-12 C alkyldiols, especially neopentylglycol, and optionally also small amounts of higher functional alcohols such as 1,2,3-propanetriol or trimethylolpropane as alcohol-functionalizing components, and aliphatic bifunctional acids, preferably 2-12 C alkyldicarboxylic acids such as succinic acid or adipic acid and optionally aromatic bifunctional acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and optionally also small amounts of higher-functional acids such as trimellitic acid as acid-functionalizing component, or (b) acid- and alcohol functionalizing components, especially with 2-12 C in the alkyl chain, especially hydroxybutyric acid, hydroxyvaleric acid, lactic acid or derivatives of these, especially SIGMA-caprolactone or dilactide; or a mixture of several of the said polyesters and/or one or more copolymers of components (a) and (b). Biodegradable polyesterurethanes are made by incorporating a reactant (c) of (cyclo)aliphatic bifunctional and optionally higher-functional isocyanates, especially 1-12 C isocyanates or 5-8 C cycloaliphatic isocyanates, such as tetramethylenediisocyanate, hexamethylenediisocyanate, isophoronediisocyanate, optionally together with linear and/or branched and/or cycloaliphatic bifunctional and/or higher functional alcohols, especially 3-12 C alkyldi- or -polyols or cycloaliphatic alcohols with 5-8 C such as ethanediol, hexanediol, butanediol, cyclohexanedimethanol and/or optionally also with linear and/or branched and/or cycloaliphatic bifunctional and/or higher-functional amines and/or aminoalclohols preferably with 2-12 C in the alkyl chain, especially ethylenediamine or aminoethanol, and/or optionally modified amines or alcohols such as ethylenediaminoethanesulfonic acid used as the free acid or a salt. Biodegradable polyestercarbonates are made by incorporating a reactant (d) of aromatic bifunctional phenols such as bisphenol-A or an aliphatic carbonic acid ester or derivative such as chlorocarbonic acid esters or aliphatic carboxylic acids or derivatives such as salt and a carbonate source such as phosgene. Biodegradable polyesteramides are made by incorporating a reactant (e) of (cyclo)aliphatic bifunctional amines, especially linear aliphatic 2-10 C diamines such as isophorone diamine or hexamethylenediamine, optionally together with small amounts of branched bifunctional amines and/or higher-functional amines, and linear and/or cycloaliphatic bifunctional acids, especially with 2-12 C in the alkyl chain and 5-6 C in the ring, especially adipic acid, optionally together with small amounts of branched bifunctional acids or aromatic bifunctional acids such as e.g. terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and optionally small amounts of 2-10 C higher functional acids; or (f) 4-20 C acid- and amine-functional components such as omega-laurolactam or eta-caprolactam. At least one layer of the film may be of a blend of the biodegradable polymer with at least one other component selected from aliphatic polyesters not made from the same monomers as the biodegradable polymer, especially polylactic acid, polyhydroxybutyric acid, polyhydroxybenzoic acid, polyhydroxybutyric acid/hydroxyvaleric acid copolymer, mixtures of these blend components or copolymers of the monomers forming these blend components, or (especially) poly-SIGMA-caprolactone.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Agent: The agent affecting the light transmission of the film is selected e.g. from carbon black or pigments or dyes which give the product a white or yellow surface. Claimed agents are chalk, talcum and/or gypsum. The layer containing the (I) and (II) preferably contains 0.05-20 (0.05-10) wt. % of the (I) and 0.05-20 (0./05-10) wt. % (II) on the total weight of the layer    TECHNOLOGY FOCUS - AGRICULTURE - Preferred Films: The films are preferably less than 200 microm thick. The films may also contain 0.5-25 (3-10) wt. % of active agents such as fertilizers, mineral nutrients, plant growth promoters, and other agents to improve the quality of the plants, harvest yield, etc. EXAMPLE - A single layer blown film 30 microm thick was made from a biologically degradable and compostable polyesteramide comprising (by wt.) 54 % eta-caprolactam, 23 % adipic acid and 23 % 1,4-butanediol (LP BAK 403-004 (RTM Bayer AG)) with the addition of 3.6 wt. % carbon black and 1.8 wt. % chalk. The base material had an MFI = 6 g/10 mins. at 190degreesC, 2.16 kg DIN 53 735 and a melting point of 125degreesC ISO 3146/C2 and contained 0.2 wt. % lubricant and 0.1 wt. % antiblocking agent. The composition was extruded through a ring die and air cooled using a maximum extrusion temperature of 180degreesC and a maximum die temperature of 175degreesC.