Environment / recycling

Feather and down recycling

To uphold resource-saving treatment of the environment, waste should be recycled wherever possible. This ensures it can return to the value-added cycle once again as secondary materials or substances. It is estimated that in Germany alone, the bed feather processing industry generates around 950 tonnes of waste feathers. Concerning the European market, this figure is multiplied accordingly. Up until now, waste feathers have either been collected by waste management companies (such as gardeners), taken to disposal sites or destroyed in incinerators. Nevertheless, the disposal of feathers in landfill sites or incinerators is set to become increasingly problematic in the future.

As a result of this, the EDFA commissioned the University of Hohenheim to carry out a research project on the use of a waste product from poultry feathers as organic nitrogen fertiliser in agriculture and horticulture.

In order to use feathers as fertiliser, consideration had to be given not only to the fertiliser law that governs the use of secondary raw material fertilisers, but also to three key requirements: :

  1. What are the active substances that have a positive effect
  2. What are the harmful substances?
  3. Will crops tolerate it and how effect is it as a fertiliser?

Active substances:

Comparison of nutrient content of feather meal, horn meal and manure
  Feather meal Horn meal Manure
(Mean values, examples) 45 70 18
Organ. substance (C) (%) 14 10 1.7
Nitrogen (%) 3.2 7 10.6
C/N ratio      
Other main nutrients (g/kg TS)   1.8 2.5
Phosphorous 2.9 1.2 5.0
Potassium 1.5 0.3 1.5
Magnesium 0.8    
Fig. 1 - Comparison of nutrient content of feather meal, horn meal and manure

Harmful substances

Heavy metal content of feather meal in comparison with green compost
  Feather meal Green compost
(Mean values; mg/kg TS)    
Lead

< 4

50
Cadmium < 0.4 0.4
Chrome < 4 25
Copper 15 30
Nickel < 4 10
Mercury < 0.02 0.2
Fig. 2 - Heavy metal content of feather meal in comparison with green compost

Plant tolerance and fertiliser effectiveness

Chemical bonding of nutrients in feather waste
Situation:

Nutrients are bound in keratins (horn substances)

= high molecular protein

which have high chemical and mechanical resistance

Problem:

Very low solubility and availability of the nutrients, e.g. for plant or animal nutrition

Immediately soluble nitrogen: approx. 0.5%

Solution:   

Nitrogen accessibility can be improved by grinding the waste feathers into feather meal (to promote the microbial conversion in the soil into soluble N compounds that can be digested by plants)

Project:

Study of the use of feather meal as organic nitrogen fertilizer in two research projects by:

  • The Institute of Plant Nutrition at the University of Stuttgart-Hohenheim (financed by the Association of European Bedfeathers and Bedding Industries)
  • Institute of Plant Nutrition and Soil Sciences at the University of Peking (China) (BAU) (financed by L. H. Lorch AG in Esslingen, Germany)
Fig. 3 - Chemical bonding of nutrients in feather waste

The study using feather meal concentrated on organic agriculture and horticulture, since no fast-soluble, synthetic fertilisers are used. In such areas, horn meal products and castor cake are often used as fertilisers. The use of feather meal would be ideal and conceptually feasible.

Within the framework of the research project, incubation tests were carried out to examine the length of time required for the release of nitrogen in feather meal. This was also compared to another organic nitrogen fertiliser (horn meal).

Soil specimens were mixed with different milling grades of feather meal, which were then kept for several weeks under controlled conditions (high temperature and humidity). At defined intervals, the pots with the soil and feather meal mixtures were tested to determine the content of mineralised (soluble) nitrogen (nitrate, ammonium). The tests were carried out in Germany and China.

It is interesting to note that the percentage of nitrogen released in the tests carried out in Germany using horn meal was slightly higher than with feather meal. In China, exactly the opposite was recorded.

Fig. 4: Release of nitrogen from feather meal and horn meal in clay soil with low nitrogen content (Institute of Plant Nutrition at the University of Stuttgart-Hohenheim)

 

Fig. 5: Release of nitrogen (in %) from feather meal and horn meal in soil used for vegetable cultivation and agricultural crops (incubation tests at the University of Peking)

The result is seen in Fig. 4. Nitrogen release of up to 50% after 12 weeks is a very good result. As a further stage of the research project, pot tests were carried out. The aim was to determine the effectiveness of feather meal fertiliser compared to horn meal and a mineral fertiliser (keratin).

Fig. 6: Harvest yields (fresh weights) of rapeseed after fertilisation with coarsely ground feather and horn meal (1mm) and urea on soil used for agricultural cultivation (pot experiments at the University of Peking)

Feather meal at various milling degrees was used to fertilise various soils to establish crop yields and crop nitrogen levels.

Conclusion:

The incubation and pot tests show

The use of feather meal as an organic nitrogen fertiliser in agriculture and horticulture has promising potential.

An enquiry sent to the Germany Ministry of Agriculture confirmed great public interest in the use of secondary raw material fertilisers, such as feather meal nitrogen fertilisers, and that the Ministry would even be prepared to grant a permit for this purpose.