The present invention relates to a device for composting of organic material, especially household waste, comprising a composting vessel, from which a gas flow is emitted, containing components with a bad smell. Such devices are known in a variety of designs. Said components with a bad smell induce nuisance and may, at large devices, also be noxious and harmful to the environment.

Thus there is a need for removal of said components and the object of the present invention is to achieve a device of the art mentioned introductorily, that is simple, and that efficiently removes components with a bad smell in the gas flow from the composting vessel.

According to the invention such a device is primarily characterized by a biological filter in the form of a vessel with a bottom designed as a supporting sheet, penetrable to a gas flow, whereupon rests a layer of active biological material, the vessel being arranged as a cap to the composting vessel, so that said gas flows through the layer, whereby said components are absorbed and are decomposed in the layer. The active layer suitably consists of light humus rich soil with naturally occurring micro organisms. The active material may also consist of relatively inert material per se, like peat, sawdust etc, to which has been added micro organisms. The form of the biological filter may be varied within wide limits. The area size and the depth of the biological filter are determined by the desired purifying capacity. The filter depth also has to be adapted to the available pressure drop through the filter and the gas flow. The filter may be designed horizontally or vertically, or designs therebetween.

Beside the purification of the gas flow also a certain heat insulating and moisture levelling function is achieved. In many cases no temperature control of the filter is needed, as the active micro organisms show a large spectrum as to the temperature, at which they are active, about between 10 and 50 a 60 degrees Centigrade. In certain cases it may be suitable to control the temperature in the

filter by adding heat into the active material, depending on the temperature of the environment, especially at cold climate.

A requisite for the biological filter to operate satisfactorily is that the active material has a certain moisture content. This is needed partly in order to absorbe the components with a bad smell in the filter and partly in order to have the mico organisms function in the desired way. Per se, within a certain temperature interval it may occur, that water vapour, accompanying the gas flow from the decomposition of the organic material, partly condenses at the lower part of the active material and then climbs up due to the capillar force and gives a moisture, that admits the desired absorbtion of components with a bad smell and contributes to a suitable environment to the decomposing activity of the micro organisms. The requirements for an optimal activity of the micro organisms are not always present. Thus, in a suitable embodiment of the device a liquid dispenser is provided to dispense liquid in the active material. If the filter is arranged horizontally, it may be suitable to arrange a water- tight protective cap above the filter, a gas outlet being provided between this protective cap and the layer of active material.

The invention is disclosed in the following, reference being made to the enclosed, schematic figures, of which: figure 1 shows a device according to the invention, whilst figure 2 shows a vessel, i e a biological filter, provided with a heat loop in the active material, a water -tight protective cap at the upper side and a dispenser for adding of liquid.

In figure 1 a composting vessel is denoted by 1, and and a biological filter by 2, in the form of a vessel, provided connected above the latter. Household waste under composting is denoted by 3 and a layer of active material in the form of light, humus rich soil with active micro organisms common in soil, with 4. The soil rests upon a sheet of fibre fabric 5, penetrable to gas, supported by a net 6. The composting vessel 1 is provided, at the lower part, with a number of inlets 7

inlets 7 for air, which is marked by an arrow 8. The gas flow, emitted from the decomposision of the household waste, that has passed the layer, is denoted by an arrow 9.

In figure 2 there is shown an embodiment of the vessel, i e the biological filter, that admits addition of heat by a heat loop 10 in the active material and the addition of water through two dispensers 11 and 12. In this embodiment the vessel is provided with a water- tight protective cap 13, that contributes to safer moisture control of the active material. Between the protective cap and the active material there is a slot for the outgoing gas flow 15.