Organic wastes can be treated to produce compost (using aerobic treatment) or a biogas (using anaerobic treatment).
Separate collection of biological waste has become an important aspect of the closed substance cycle. It concerns materials arising in conjunction with human nutrition, either as kitchen waste or as waste from food processing. It also includes grass cuttings and garden waste. In total, between five and six million tonnes of biological waste in Germany are processed into high quality compost in approximately 500 composting plants employing some 4,000 people. For the Federal Republic as a whole, the total potential for biological waste is estimated at between ten and twelve million tonnes.
The German Government passed its Biological Waste Ordinance in 1997. The Ordinance contains stringent provisions governing the hygiene properties and pollutant levels of biological waste and compost, as well as taking agricultural requirements into account. Under the collective term "biological waste", the Ordinance basically covers all treated or untreated biodegradable waste applied to agricultural and horticultural areas. In particular, this includes compost from biological waste. The maximum amount for application is 20 or 30 tonnes per hectare over three years, depending on the quality criteria adhered to. Compost heaps in private gardens and allotments are not affected by the Ordinance.