Compost and digestate from organic waste make for an ideal organic fertilizer for agricultural purposes, and also promote soil humus content stabilization or improvement. However, to achieve this it is necessary for organic waste to be collected separately, as this is the only way that allows for the production of quality compost and digestate that are suitable for agricultural and horticultural use. They also make an excellent substitute for horticultural peat and in this way reduce greenhouse gas emissions, and protect plant and animal habitats. However, the treated organic waste must meet the relevant quality standards and the treatment process should be as ecofriendly as possible.
In Germany, the practice of collecting organic waste separately and then composting it began around 25 years ago, and the use of recycled organic waste has risen steadily since then. According to Federal Statistical Office (Statistisches Bundesamt) figures, in 2011 around 14 million tons of organic waste were composted or converted into digestate (in biogas facilities) for use as fertilizer.
The organic waste processed at composting or anaerobic digestion plants stems from the following sources: households; yards and parks waste; restaurant and canteen kitchens; food processing plants; and agricultural residues. In 2011 alone, four million tons of organic waste were collected in bio bins from households in Germany, with yard and park residues contributing an additional five million tons. Most organic waste is still composted nowadays, and only a small portion of it is used to make biogas and digestate.
According to a study commissioned by the UBA titled Aufwand und Nutzen einer optimierten Bioabfallverwertung, in 2008 there were around 1,000 composting plants and 85 anaerobic digestion plants in Germany that used organic waste from households, businesses, yards and parks. For a complete listing of Germany’s composting and biogas facilities, see Handbuch Bioabfallbehandlung (UBA, 2012).
Compost and digestate derived from organic waste make for excellent fertilizer and promote humus formation. A study commissioned by the UBA titled Optimierung der Verwertung organischer Abfälle found that separate collection and recycling of organic waste are more ecofriendly than any other approach to organic waste management. The organic waste management alternatives investigated by the study included leaving organic waste mixed in with residual waste and then processing it at an incineration or mechanical-biological treatment facility. However, organic waste recycling is only ecologically advantageous if the waste is treated using state of the art techniques and if recycling is carried out in accordance with the highest possible quality standards. Organic waste should be processed in an anaerobic digestion whenever possible, as this allows for the energy in the waste to be used as biogas. Residues can be marketed either as liquid digestate or, after being composted, as solid digestate. This translates into a cascade that allows the energy content of organic waste to be used, followed by its substance properties.
According to the study titled Aufwand und Nutzen einer optimierten Bioabfallverwertung, only around 46 percent of consumers have an organic-waste container (bio bin) at their disposal, while the remaining 54 percent cannot or do not wish to collect organic waste separately. Expanding Germany’s organic waste container fleet could potentially increase organic waste output by two million tons. Altogether, separate collection of organic waste reduces the amount of residual household waste by up to one third. Added to this is the fact that separating residual waste from wet elements simplifies downstream processes such as mechanical sorting.
Germany’s 2012 Kreislaufwirtschaftsgesetz law is the first federal statute to require for the national level that organic waste be collected separately. This practice will become mandatory as of 1 January 2015.
The pamphlet jointly issued by the Federal Ministry for the Environment (BMU) and the UBA titled Ecologically sustainable recovery of bio-waste provides municipal decision makers with advice concerning the implementation and optimization of separate organic waste collection.
