Bioorganic waste samples are very common like garden waste or food residues and versatile. They can be ground in Rotor Mills much easier when they are dried to prevent blockages and sticky effects. Dried sewage sludge is commonly ground to about 2 mm particles in a Cutting Mill, here the basic model SM 100 a good choice. About 100 g sample require – depending on the sample properties like feed size and moisture residues – between 2-4 min. Garden residues containing twigs and other tough plant waste need to be pre-cut in the SM 200 or in the strong SM 300 models with higher speed and using the robust 6-disc rotor. Fine-grinding can be done in Planetary Ball Mills like the PM 200 or the Ultra Centrifugal Mill ZM 300, depending on the required sample throughput and final fineness. Food residues like orange peel also need drying before grinding in a Rotor Mill. Larger sample quantities such as 1 kg can be processed in the Rotor Beater Mill SR 300. As those samples tend to get warm during grinding, slow feeding is required, and the use of the distance rotor is beneficial. About 25 min are required for the 1 kg sample, when a 1.5 mm bottom sieve is used.

The Cutting Mill SM 300 is the most suitable mill to pre-cut soft sample materials. The parallel-section rotor and bottom sieves of 2 - 6 mm aperture are typical for this application. A cyclone helps to discharge the fluffy sample from the grinding chamber. Depending on the material, e.g. for more tough leather articles, cryogenic grinding may be required in the pre-cutting step. Here, immersing the sample for some minutes in liquid nitrogen embrittles the sample. In the case of cryogenic grinding, it is better to use the more robust 6-disc rotor.

The fine grinding step is either done in a Ball Mill or in the Ultra-Centrifugal Mill ZM 300. Embrittling the pre-cut fibrous samples may help to get fine ground particles. As the fibers do not keep the low temperatures and tend to warm up quickly, mixing with dry ice is superior to embrittling with liquid nitrogen. For this, the fibers are mixed 1:2 with dry ice snow and the complete mixture is fed into the ZM, usually equipped with a 0.5 mm ring sieve and operated at 18000 rpm. For cryogenic grinding, a cyclone should be used. Another way to get very fine particles of textiles is to use either the CryoMill or the MM 500 control. The MM 500 control offers larger grinding jars than the CryoMill and two grinding stations. Both mills embrittle the sample by using liquid nitrogen for cooling. In both cases first a pre-cooling time of 10-20 min is required to freeze the samples. The sample is then ground in ca. 10 cycles of about 1 min at 30 Hz with 1 min cooling breaks.