Millions of tons of organic waste are generated in Germany every year – but not everything organic that is left over in the kitchen and the like is disposed of properly. There is a lot of potential in organic waste: it can be used to produce energy, compost and fertilizer. How is the waste recycled? What can go in the organic waste bin? And how can you avoid the annoying smell?
Since 2015, cities and municipalities have had to provide their citizens with a system for the separate collection of organic waste. In 2023, 5.2 million tons of waste were collected in organic waste bins in Germany. Nevertheless, every year around four million tons of organic waste still end up where it no longer belongs: in the residual waste bin. Correctly sorted organic waste has great recycling potential. Organic waste can be fermented into energy or composted into fertilizer. How does it work?
Utilized into biogas or compost
Before fermentation in the biogas plant, the waste is pretreated. Contaminants such as plastic or glass are removed and the organic material is sieved, ground or chopped. Microorganisms then break down the organic waste in the system and produce biogas. Depending on the technology, this is used directly in gas engines to generate electricity and heat or processed into biomethane and fed into the natural gas network. After fermentation, a digestate remains, which can also be reused: the solid portion is suitable as compost, the liquid portion can be used as fertilizer.
As an alternative to fermentation, the organic waste can also be completely composted. For this purpose, the organic waste is also first processed. Contaminants are sorted out, the material is sieved and separated into coarse and fine fractions. In the subsequent rotting phase, microorganisms decompose the organic material under controlled conditions. High temperatures arise in the large compost heaps, which accelerate microbial degradation, kill harmful germs and largely prevent the formation of methane, which has an impact on the climate. This is followed by several weeks of post-rotting, during which humus forms and the compost is biologically stabilized. Finally, the compost is often sieved again and sorted according to grain size.
Both processing processes are worthwhile and provide valuable materials: “One ton of organic waste produces 350 to 450 kilograms of compost in ten to twelve weeks. This could replace around ten kilograms of elaborately manufactured artificial fertilizer,” reports Deutsche Umwelthilfe e. V.. “In addition, an average of up to 130 cubic meters of biogas can be obtained from one ton of organic waste, which replaces 78 liters of heating oil.” However, the following applies to both types of recycling: the more contaminated the organic waste is, the greater the sorting effort, the costs and the loss of quality. It is therefore important to only dispose of suitable waste in the organic waste bin. But what kind of waste does this actually include?
What belongs in organic waste and what doesn’t?
The municipalities decide exactly what can go into the organic waste bin. Depending on how the organic waste is to be recycled later, not all organic waste always ends up in the appropriate bin. As a rule, old bread and baked goods, eggshells, vegetables, hair, wood chips, coffee grounds and filter bags, cheese, plant-based small animal litter, dairy products, nut shells, fruit, cut flowers, tea bags and potted plants are permitted.
Fish, meat and bones are usually also allowed, but should be wrapped in some kitchen paper or newspaper if necessary to absorb odors and prevent mold and maggot infestation in the organic waste bin. Cooked or spoiled food leftovers and garden waste can usually be thrown into the organic waste in normal household quantities.
For example, ash, animal excrement, glass, rubbish and plastic in general do not belong in the waste – even if it is labeled as certified biodegradable or compostable.
This can prevent unpleasant smells
The most environmentally friendly way is to put kitchen leftovers directly into the organic waste bin without any additives. To collect these in the kitchen, an easy-to-clean, lockable container that is emptied and rinsed regularly is suitable. However, some people are bothered by the possible smell and therefore avoid using an organic waste bin. But there is something that can be done about the smell. In general, the drier the organic waste, the fewer odors it produces. Absorbent material such as kitchen paper, egg cartons or even leaves in the organic waste bin bind liquid and prevent waste from sticking.
If you use a small collection container for the kitchen, you can also line the bottom with some kitchen paper or unprinted cardboard to absorb moisture. Coated paper bags are also suitable. However, special plastic organic waste bags should be avoided, as they are usually considered nuisance substances in compost and biogas plants.
The location and care of the organic waste bin also play a role in the formation of odors: it should be placed in the shade where possible, emptied regularly and washed out if necessary. Lids with built-in biofilters can also help reduce odors and maggot infestation. In summer, it may also be useful to occasionally spray the bin lid with a vinegar and water mixture to keep insects away.