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Assessment of Alternative Phosphorus Fertilizers for Organic Farming: Chars, Ashes and Slags

Möller, Kurt (2016) Assessment of Alternative Phosphorus Fertilizers for Organic Farming: Chars, Ashes and Slags. Dossier/Fact sheet, no. First edition. Universität Hohenheim, ETH Zürich, Research Institute of Organic Agriculture (FiBL), Bioforsk, BOKU, Newcastle University, University of Copenhagen .

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PDF - English (Fact sheet)

Document available online at: https://shop.fibl.org/en/article/c/fertilization/p/1709-fact-sheet-ashes.html


The application of sewage sludge to agricultural land, a common practice to recycle nutrients in the past, is currently prohibited in organic farming due to the risk of soil contamination from pollutants (e.g. toxic and potentially toxic elements, persistent organic pollutants, etc.). Incineration or disposal to landfill of dewatered sludge is costly, leads to greenhouse gas emissions, and eliminates the possibility of nutrient recovery, especially phosphorus. Options to treat dry organic matter are combustion and gasification, among other technologies to produce ashes or chars and to recover the residues for nutrient recycling. Dependent on the technology applied as well as the input material, nutrient concentrations and concentration of contaminants vary widely. Due to organic matter degradation, non-volatile elements including mineral nutrients like phosphorus, potassium, magnesium and calcium are enriched in ashes and chars.
Thermal processes have high P recovery rates of 80 to 90 % depending on the treatment procedure. For organic farming, ashes from sewage may allow the recycling of P from the food chain by rather simple technologies. The risks of reducing the soil quality by xenobiotic compounds may be minor with incinerated products. Permission to use such fertilizers in organic farming in the EU would contribute to better nutrient cycling between rural and urban areas, reduce problems of declining phosphorus concentrations in some organic farming systems and could also contribute to the development of practical methods for processing sewage. This fact sheet describes different types of chars and ashes with their characteristics and possible applications. Beyond that it indicates ways to enhance the use of ashes in organic agriculture.

EPrint Type:Report
Keywords:ashes, lags, chars, phosphorus, recycling, fertilizer value, IMPROVE-P
Agrovoc keywords:
Subjects: Crop husbandry > Composting and manuring
Soil > Nutrient turnover
Research affiliation: European Union > CORE Organic II > IMPROVE-P
Austria > Univ. BOKU Wien > Sustainable Agr. Systems - IfÖL
Austria > FiBL Austria
Switzerland > ETHZ - Agrarwissenschaften
Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil
Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Sustainability > Climate
Germany > University of Hohenheim > Institute of Crop Science
Denmark > KU - University of Copenhagen
Norway > Bioforsk - Norwegian Institute for Agriculture and Environmental Research > Bioforsk Organic Food and Farming Division
UK > Univ. Newcastle
Related Links:http://www.coreorganic2.org
Deposited By: Möller, PD Dr. Kurt
ID Code:30920
Deposited On:19 Dec 2016 09:28
Last Modified:19 May 2021 11:32
Document Language:English
Refereed:Not peer-reviewed

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