Phosphorus bioavailability in ash from straw and sewage sludge processed by low‐temperature biomass gasification

Dorette Sophie Müller-Stöver, Iver Jakobsen, Mette Grønlund, Morten Mikkel Mejlhede Rolsted, Jakob Magid, Henrik Hauggaard-Nielsen

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Reuse of phosphorus (P) from waste streams used for bioenergy conversion is desirable to reduce dependence on nonrenewable P resources. Two different ash materials from low‐temperature biomass gasification of wheat straw and sewage sludge, respectively, were investigated with regard to their P bioavailability. A set of pot experiments with spring barley was carried out to compare the ash P fertiliser value with mineral P fertiliser and the sewage sludge feedstock. An indirect radioactive labelling approach with 33P was used to determine the amount of P taken up from the fertiliser materials. Depending on the application rate, straw gasification ash produced a fertiliser response comparable to mineral P. However, P uptake from the ash was generally less than uptake from equivalent amounts of mineral P, and the calculated relative effectiveness was 44% after 6 weeks of plant growth. In contrast, the P fertiliser value of Fe‐rich sewage sludge after low‐temperature gasification was practically zero. These results suggest that ash from low‐temperature gasification could be developed into alternative P fertilisers; however, as the P bioavailability depends greatly on the feedstock used, a greater emphasis on feedstock composition is required.
Translated title of the contributionPhosphorus bioavailability in straw and sewage sludge ashes from low-temperature biomass gasification
Original languageEnglish
JournalSoil Use and Management
Issue number1
Pages (from-to)9-17
Publication statusPublished - 2018


  • Gasification
  • ash
  • fertilizer
  • phosphorous
  • Sewage sludge

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