Is there a potential for P recycling in the
mineral fertilizer industry?
Laetitia Six
Co-authors: Antoine Hoxha and Kees Langeveld (ICL)
SPS 2014 Montpellier
Production of P fertilizers
Mining of phosphate rock
Ca5(PO4)2(F,Cl,OH)
Transport to Europe
The Hague Centre (2012) – based on USGS 2012
P fertilizers such as NPK,
TSP/SSP, MAP, DAP, …
Consumption in EU28:
2.6 million ton P2O5 /yr
Application rate:
23 kg P2O5/ha
Production processes
Phosphate
Rock
Wet process
+ H2SO4
Thermal process:
800-1000 °C
H3PO4
P4
+ K and N source
Acidulation with
H3PO4 or H2SO4
TSP/SSP
Nitrophosphate route
Reaction with HNO3
Mixture H3PO4 and
Ca(NO3)2
+ K and N source
NH3 neutralization
MAP, DAP,
NPK’s
NPK’s
Closing the loop…
Nutrients are precious and thus losses need to be limited and
uptake by plants maximized:
• Farming best management practices
• R&D for products with higher nutrient use efficiency, lower C
footprint, less prone to leaching,…
• Right time, right dose, right product, right place
• Fertigation and precision farming
• P recycling
From waste to…
… P fertilizer
‘Waste’ streams rich in P are:
o Manure
o plant residues
o animal waste
o food waste
o waste water
Needs:
(1) Nutrient accumulation or concentration from P sources into
final product when too diluted
(2) Nutrient in final fertilizer product should be present in
plant-available form (H2PO4- or HPO42-)
P-rich waste
Problem
Solution
Manure
High water content
Dewatering and monoincineration, pyrolysis or
gasification
Sewage sludge (SS)
High water content
Organic contaminants
Dewatering and monoincineration  SSA
Meat and bone meal
(MBM)
Direct use in feed
forbidden due to mad
cow disease
Mono-incineration  MBMA
Waste water
P is too diluted
Precipitate to form struvite
(MgNH4PO4.6H2O)
Main differences between the sources are the solubility of
phosphate, the contaminants (mineral and/or organic) they contain
and the physical form.
1. Mono-incineration ashes
P is not soluble in water or neutral ammonium citrate (NAC)  not
plant-available form  acidulation needed (cfr. phosphate rock).
Differences with phosphate rock and acidulation process:
•P from ashes is in complexes with Fe, Al or Ca, not always similar to
phosphate rock.
•Heavy metals and contaminants can react with acid  regular
acidulation doesn’t yield the physical and chemical results required.
•Fine powder  no grinding needed, but impact on storage and
handling.
a) Meat and bone meal ashes (MBMA)
MBMA ashes show most similarities with phosphate
rock:
Form: Ca3(PO4)2
P2O5 content 25-30 %
 Mix of MBMA with phosphate rock can react with H2SO4 or H3PO4
to give the regular products (SSP or TSP)
Acidulation with MBMA alone? More difficult processibility.
b) Sewage sludge ashes (SSA)
Al, Fe and heavy metal content is much higher compared to
phosphate rock, especially when expressed in content per % P2O5
Wt %
ppm
P2O5
Al2O3
Fe2O3
Cu
Mn
Pb
Zn
Cd
SSA (average 4 samples)
18
9
7
765
1372
192
1923
<1
Phosphate rock
31
0.1
0.2
14
7
<0.1
260
26
The processing of SSA is a challenge!
• During reaction: formation of FePO4, thus less free H3PO4 to
react to superphosphate  preference for H2SO4 acidulation
• Large differences in quality of SSA  large spread in resulting
products and quality
• Acidulation of SSA together with phosphate rock is difficult BUT
it is possible to mix acidulated phosphate rock with acidulated
SSA in granulator.
2. Struvite
Formation: addition of Mg2+ to waste water
Mg2+ + NH4+ + PO43- + 6 H2O  MgNH4PO4. 6 H2O
(15-20 % P2O5)
Phosphate in struvite is in plant-available form  No need for
acidulation, direct input in granulator together with acidulated
phosphate rock (max. 20 % of total input). Limiting factor is
moisture content.
Concerns with struvite:
•Presence of pathogens, pharmaceuticals, hormones , etc.
encapsuled in crystals.
•Odour
P recycling? YES but…
challenging!
Process-related challenges: Fe and Al content, moisture content,…
Safety: environmental, animal and human health
– Heavy metal content
– Organic contaminants (pathogens, farmaceuticals, hormones…)
Legislation needs to enable recycling  end-of-waste criteria
Supply of secondary raw materials
– Quantity
– Supply
– Quality
– Price fertilizers are high quality
Mineral
products, even when they are based on
recycled P sources.
Cartoon 1 European Sustainable
st
Phosphorus Conference 2013
Thank you!
Laetitia Six
www.facebook.com/fertilizerseuropepage
www.twitter.com/FertilizersEuro
http://www.youtube.com/user/FertilizersEurope
Group Fertilizers Europe
www.fertilizerseurope.com
www.productstewardship.eu
www.memberslounge.eu