The object of the invention is a method for feeding a substance to a continuously operating composter, which is fed intermit- tently and pulsatingly with peat, dung, straw, turf, or other substance which is intended to be decomposed by the aerobic method and which typically leaves the composter after a few days and which is then transferred to a storage and/or further combustion pile. The invention is also concerned with a composter using this method.

Composters are typically used for the treatment of dung, in which case it is primarily rendered odourless and the problem of flies is avoided. The treatment kills weeds and bacteria that might spread disease. In addition, composted dung stores nutrients and provides them to plants in an easily assimilated form. In addition to the maturing of dung in cattle farming, typical areas of application of a composter are the treatment of wastes from housing, greenhouses, market gardens, and fur farms.

The dung or other waste to be treated by the composter is usually in the form of sludge. In this state its water content (85...95%) is too great for it to be fed directly to the composter and a substance with a high humus content, such as, for example, peat, is mixed with it. The dry matter content of the substance being fed to the composter should be about 25...35%. The mixture of peat in particular with sludge is difficult, because due to the great surface tension peat does not naturally absorb sludge but remains floating on the surface of the sludge. They do not necessarily mix when transferred by a feed screw or other known conveyor.

A continuously operating composter is affected greatly if even a relatively small amount of sludge is fed to it. In practice the water contents of the wastes being treated may vary greatly, which creates a continual problem in the feeding of the substance. On account of the lack of homogenity in the substance it is difficult to measure the water content reliab-

ly, so that it is difficult to apply control automation in this case.

The intention of this invention is to achieve a new kind of feed method for a substance and equipment, which will remove the danger of substance that is too wet being fed to the composter chamber.

The characteristic features of the method in accordance with the invention appear in Patent Claim 1 and the characteristics of an advantageous device for realizing the method appear in Patent Claim 3.

It is extremely advantageous if there is also a delay in the feed of the substance, so that the water in the sludge can be absorbed better into the peat or other humus substance. In practice a piston compressor has been found to be the most effective transfer device, because it also has a powerful mixing effect on the feed. The sludge always squeezes through the drier substance during the power stroke, but excess water is always able to drain off during the return stroke. In addition, the pressure created by a piston compressor further improves absorption.

In what follows the invention is illustrated by reference to the accompanying illustrations, which show one form of applica¬ tion of the invention.

Figure 1 shows the composter seen from the side Figure 2 shows the composter seen from in front Figure 3 shows the substance feed device in detail

The illustrations show a composter 1 adapted to the maturing of dung on cattle farms. The dung is dropped into the feed hopper 6, from which it is transferred along channel 4 to the compos¬ ter chamber 8, which is principally formed by a revolving drum in which _r after a few days' treatment the dung changes in the known manner into an improved form and is removed by the screw

conveyor 3. The device shown in Finnish patent publication 75335 can be used for the removal of the substance.

The feeding of the dung and humus substance to the hopper 6 can take place quite unevenly. The hopper 6 includes a pushed chain 11 and crusher rollers 12 by means of which the substance is both broken up and dropped into the feed opening 10 of the piston compressor that is used as a transfer device 7. The effective length of stroke of the piston compressor begins after the feed opening 10 and the feed unit is marked with the reference number 5 in the illustration. The piston compressor pushes the substance into channel 4, the volume of which is many times greater than that of a single feed unit 5. Channel 4 includes a vertical section 9, from which the excess water in the substance flows down. Sludge that is too wet slops back and forwards in the start of channel 4 until sufficient drier substance has been mixed with it. Drier substance, with a dry matter content of 25...35% adheres to the vertical section and rises stroke by stroke to the hopper of the feed screw 2 of the composter chamber 8. The feed screw 2 breaks up the lumps foamed in channel 4 at the same time as it transfers them into the composter chamber 8.

In practice it has been noted that substance that is about 30% adheres to a pipe with a diameter of 35 cm. The two meter high channel 4 used in connection with a 10 m ³ composter gives a delay of about 24 hours. The pipe material is stainless steel. If the diameter of the pipe is increased, it is advantageous to weld a few longitudinal ribs to the inside of the pipe, so that the relative friction remains sufficiently great to hold the substance in place over its entire cross-section.