Q&A Feed Webinar 3 February 2022

During the webinar Improving sustainability of livestock production the 3d of February, we received a number of questions from the viewers that are answered below.

1. Can you describe the PCP?
It is a white powder, 95% dryness that is fully soluble in citric acid.

2. What is the price of the PCP compared to MCP?
It is too early to say, but probably in a similar range or somewhat lower.

3. Is the PCP allowed in feed today or under approval scheme?
Regulation 767/2009 is still linear, focusing on origin instead of quality. Therefore, all recovered phosphorus with origin in wastewater and sewage sludge to be used in animal feed is prohibited, i.e. the recovered phosphorus from Ash2Phos is not allowed to be used as a feed phosphate in Europe at the moment. We are investigating the possibility to sell the PCP outside Europe if this regulation continues to block recovered feed phosphates.

4. What are the next steps in terms of lobbying at the EU level to change the regulatory framework in order to allow PCP in feed and when can we expect such a change?

The next steps will be to:

  • Use the results from the digestibility tests to show a good example that it is possible to recovery a pure feed phosphate form incinerated sewage sludge.
  • Launch a communication plan including several meetings with authorities, politicians and potential customers.
  • Compile information on how ash can be a safe starting point in the manufacturing chain (not to have wastewater as origin, but incinerated ash).

5. Even if legislation is adapted to allow phosphate from waste as a product going into feed, will the market accept it? Using such feedstocks carries a risk of contaminating the food chain, of which we've seen some examples. Even if the risks are controlled with a robust production process, responsibility will remain with the feed phosphate supplier to avoid any contamination of the food chain. Will the market accept this?
EasyMining fully supports strong safety requirements to prevent risks of pathogens and contaminations in animal feed and feed additives. The process is robust and can guaranty the purity of the recovered calcium phosphate with no risk for pathogens or contaminants due to several processing steps such as incineration in 850C°, acid treatment (pH=0) and base treatment (pH >13).

6. Given the PCP’s digestibility - 70-80% compared to MCP – is this good enough for feed producers/users? How is the digestibility compared to DCP, which also has a lower digestibility than MCP?
According to Bikker et al. (2016), the P apparent ileal digestibility (AID)for chickens were 59.0% for dicalcium phosphate (DCP), 70.7% for monodicalcium phosphate (MDCP) and 31.5% for defluorinated phosphate (DFP). Trairatapiwan et al. (2018) reported that the AID of P in chickens of MDCP and DCP was 60.2% and 69.3%, respectively.

For pigs, Petersen and Stein (2006) reported apparent total tract digestibility (ATTD) of P in DCP to 81%. Kwon and Kim (2017) reported a ATTD of P to be 78% for DCP, 79% for MDCP, 87% for monosodium phosphate (MSP) and 65% for tricalcium phosphate (TCP).

Thus, the PCP digestibility of 60.4% (ATTD in pigs) and 58.4% (AID in chickens) seems comparable with the reported digestibility values for DCP for chickens, but somewhat lower for those reported for pigs.

In order to determine the market value for PCP, the slightly lower digestibility values compared to MCP must be put in relation to other factors influencing the total environmental impact, i.e. CO2 –emissions, the benefits of closing the phosphorus cycle, prolonging the lifetime of the mines and possibilities to have domestic production of P.

7. If PCP is less digestible in animals, it means it's not used efficiently. It will end up in manure. Is this not a waste of a valuable resource?
In case the manure can be used as a fertilizer or incinerated, and the phosphorus being recovered from the ash there is no waste of valuable resource. This was the first time a recovered feed phosphate was tested in this type of trails. A next step will be to optimize the efficiency. From a holistic point of view, the whole value chain needs to be optimised and the total footprint of the production and product need to be considered.

Another possibility is if the PCP is used as raw material for production of MCP. Then it is possible to omit the limited reduction in digestibility (80% compared to MCP).

8. Is it demonstrated that PCP is a less digestible feed additive compared to MCP. In the highly competitive and saturated feed phosphate market, do you see real market opportunities? The general trend is towards MCP or mixed MDCP. Even a highly digestible DCP-dihydrate from Ecophos had much difficulty penetrating the market. What is the market perspective for PCP?
In case the manure can be used as a fertilizer or incinerated and the ash used for production of PK fertilizer or feed phosphate, the lower digestibility (ca 80% compared to MCP) is not a problem if the price of PCP is compensated for the lower digestibility. PCP can also be used as a raw material for production of MCP replacing purified phosphoric acid and lime (if legislation will allow) in that case no difference in digestibility. Since PCP is completely soluble in dilute citric acid it can also be used as a slow-release fertilizer (even for main crop production PCP is effective, tests have shown 80% efficiency compared to water soluble triple super phosphate).

9. What would the capacity of the planned Ash2Phos plant be?
The two planned Ash2Phos plants (in Schkopau, Germany and Helsingborg, Sweden) will have a capacity of 30 000 ton ash / y and will produce 15 000 ton PCP / year (16 - 17% P).

10. During acid extraction of phosphorus, heavy metals co-dissolution can occur in the Ash2Phos process. Why is it not required with an additional purification unit to purify the leachate before precipitation? Do you apply selective precipitation to recover first Al and Fe and then phosphorus as Ca-P? Do you recover or reuse in some way the process water and acidic solid residue? 
The process is based on several precipitation-dissolution reactions at different conditions that enable to separate phosphorus, iron and aluminium from the heavy metals that are later precipitated as hydroxides/sulfides.

11. With net zero carbon concerns re global climate change, how does the carbon intensity of Ash2Phos from sewage ash compare to say struvite from wastewater in terms of kw-hr per kg of P recovered as product?
Struvite recovery and recovery from ash cannot be compared directly. Struvite is mostly recovered on-site WWTP. Application is limited to certain WWTP designs and quantities of recovered P are rather limited.

P recovery from ash as done with Ash2Phos is independent from WWTP design and capacity. Ashes can be pooled or clustered providing a higher degree of scalability and mutually allows for volumes of recovered materials with higher market relevance.

Both routes, on-site struvite recovery, tapping a part of dissolved ortho-P from the aqueous sludge phase and down-stream like ash based recovery can be seen complementary, with the ash route tapping higher shares and larger volumes per facility.

We have an LCA comparing Ash2Phos to production of feed phosphates showing significant reduction in CO2. A main difference in phosphorus recovery from sludge ash compared to recovery of struvite is much higher recovery rate for phosphorus from ash (>90% compared to 15-50%)

12. Does anyone use algae derived from wastewater plants as an alternative fish feed ingredient for enhanced sustainability and circular economy in aquaculture?
In modern wastewater treatment plant, the phosphorus is removed with the sludge and very little phosphorus is available in the treated effluent for growing algae. Such a process will require to change the whole wastewater treatment process and probably will require very large surface area to provide light for algae to grow in competition with bacteria feeding on the organic matter.

13. Is there any poultry litter (chicken manure) digestate that is the subject material for P recovery and reuse?
If poultry litter is incinerated the ash can be used as a source for phosphorus recovery.

14. Is there any market potential for recovered iron phosphates from sewage sludge?
In the Ash2Phos process the phosphorus is recovered in form of calcium phosphate (that is completely soluble in citric acid) and not as iron phosphate.

Iron phosphate has in general a low solubility and is not suitable as a fertilizer or feed phosphate. It should be converted to another form to be used in agriculture.


Thank you for contributing!

If you have any further questions, believe your question wasn´t answered, or want to discuss the project or the results, please contact Sara Stiernström, Product Manager EasyMining: sara.stiernstrom@easymining.se