The document summarizes the environmental and potential human health impacts of land applying dairy processing waste. It outlines current problems in the food system and opportunities for more sustainable practices. It then discusses the characteristics of dairy processing waste, including its nutrient content and potential risks to human health. Solutions for managing dairy waste through creating secondary-raw materials like struvite, biochar and ash are presented. A calculation tool was developed to determine safe maximum application rates of these materials to agricultural land. Further studies on emerging contaminants and improving the tool are suggested.

1. The Environmental and Potential
Human Health Impact arising from the
Land Application of Dairy Processing
Waste
The REFLOW project has received funding from the European Union’s
Horizon 2020 research and innovation programme under the Marie
Skłodowska-Curie grant agreement No 814258.
Wenxuan Shi
Marie Skłodowska-Curie Early Stage Researcher
Supervisors: Prof Owen Fenton (Teagasc)
Prof Mark Healy (NUI Galway),

2. 2
 Current problems in the food
system
 Opportunities
 Dairy processing waste
 Overview
 Potential risks
 Characterisation
 Solutions
 Future studies
Outline
The REFLOW project has received funding from the European Union’s
Horizon 2020 research and innovation programme under the Marie
Skłodowska-Curie grant agreement No 814258.

3. GHG emission Natural resources
consumption
Biodiversity loss Negative health
impacts
Current Problems in the Food System

4. Opportunities:
Policies

5. Optimise soil
fertility &
fertilisation
Improve
animal
welfare
Increase
organic
farming
Sustainable
use of
pesticides
Opportunities:
Main Practices

6. Dairy Processing Waste
Issues
Large volumes
High BOD, COD, chlorides and
sulphates
2.7-4% of Global GHG Emissions
Eutrophication
Advantages
Rich in Nutrients, especially in P
Low heavy metal concentration
Good feedstock for nutrients
recovery

7. Dairy Processing Waste
Dairy industry Wastewater Treatment
Sludge
Agricultural land spreading and
nutrient recycling

8. Sample
Type
DM pH OM TC TN TP TK Mg S Ca Fe Al Cu Ni Pb Cd Zn Cr As Mo
% of
wt.
/ % of DM g kg-1 mg kg-1
Al-DPS 12.5 7.1 68.4 32.6 57.6 34.7 7.4 3.6 5.5 41.8 1.4 34.5 13.5 4.4 1.9 <0.15 89.8 9.5 <1.5 2.7
Fe-DPS 20.1 7.3 52.1 25.2 45.6 40.7 9.2 2.9 3.4 78.1 111.9 0.8 8.7 13.9 6.0 <0.15 132.5 12.0 <1.5 0.5
Ca-DPS 21.8 7.2 47.2 27.4 30.8 52.8 4.1 4.9 2.5 155.9 1.3 0.8 10.2 6.7 2.7 0.2 91.2 7.7 <1.5 3.9
EU limit*
1000-
1750
300-
400
750-
1200
20-40
2500-
4000
16-25
Dairy Processing Waste:
Characterisation
 The dairy processing wastes are rich in N and P, but the K content is relatively low.
 The concentration of heavy metals are lower than the EU limit of biosolids.

9. Dairy Processing Waste:
Potential risks to human health
 Potential contaminants
• Heavy metals
• Microplastics
• Chlorates (Cleaning)
• Pesticides
• POPs
• Antimicrobial Drugs
• Hormones
 Disease spreading
 Negative effects on
microbial activity
 Excessive fertilisation
Shi, W., Healy, M. G., Ashekuzzaman, S. M., Daly, K., Leahy, J. J., & Fenton, O. (2021). Dairy processing sludge and co-
products: A review of present and future re-use pathways in agriculture. Journal of Cleaner Production, 128035.
Hu, Y., Khomoenko, Olha., Shi, W., Sanchez, A. V., Ashekuzzaman, S. M., Daly, K., Fenton, O., Healy, M. G., Leahy, J. J.,
Sørensen, P., Sommer, S. G., Taghizadeh-Toosi, A., Gattin, I. T. (2021). Systematic Review of Dairy Processing Sludge and
Secondary STRUBIAS Products used in Agriculture. Front. Sustain. Food Syst. 5:763020. doi: 10.3389/fsufs.2021.763020

10. Solutions:
Secondary-raw-material-based products
Sludge
Struvite
Biochar
Sludge
ash
Precipitation
Oxygen-depleted
thermochemical
conversion
Incineration by
oxidation

11.  Secondary-raw-material-based products characterisation
Sample
Type
TC TN TP TK Mg Na S Ca Fe Al Cu Ni Pb Cd Zn Hg Cr As Mo
% of DM g kg-1 mg kg-1
Chars
BC1 28.4 19.4 52.3 14.7 8.0 9.3 7.1 97.0 4.1 33.8 44.7 13.8 16.4 0.29 269.6 <0.1 25.7 2.2 5.4
Al-BC2 29.4 52.8 108.5 20.3 11.0 4.8 8.1 69.6 1.3 47.5 14.4 3.0 <2 <0.15 337.8 10.2 <1.5 4.4
Al-BC3 28.0 41.1 113.0 26.1 14.7 6.0 3.4 83.6 1.1 59.6 20.4 5.8 <2 <0.15 478.3 13.5 <1.5 5.4
Fe-HC1 22.6 37.5 78.9 13.5 3.7 2.8 3.2 68.0 177.3 8.0 47.8 7.6 5.9 <0.15 186.1 6.5 <1.5 <0.5
Fe-HC2 18.4 29.4 85.4 8.5 3.7 1.8 12.8 72.0 199.7 8.5 6.1 9.4 5.9 0.25 185.9 6.8 <1.5 <0.5
Fe-HC3 21.2 36.5 79.9 12.6 3.5 2.6 8.2 65.7 183.4 7.8 5.4 9.1 5.3 <0.15 171.7 6.8 <1.5 <0.5
Ashes
A1 0.90 1.1 99.3 26.7 17.0 20.5 11.9 227.5 7.5 82.1 92.7 27.4 32.6 0.68 482.4 <0.1 41.2 4.1 11.1
Struvites
MAP1 25.9 29.4 91.1 7.1 101.3 2.6 0.16 14.7 0.07 0.02 1.8 <0.6 <2 <0.15 30.1 <0.1 2.2 <1.5 <0.5
MAP2 38.8
11.2
66.9 7.5 62.2 8.8 0.46 34.5 0.17 0 0.21 <0.6 <2 <0.15 34.4 <0.1 2.8 <1.5 <0.5
CaMAP 31.6 56.7 38.6 6.5 18.8 31.7 0.62 66.9 0.39 0 0.38 <0.6 <2 <0.15 36.2 <0.1 3.3 <1.5 <0.5
Regulation
EU * 300 50 120 1.5 800 1 - 40 -
BC1 was from a mixture of biological DPS and spruce wood chips in a 50/50 ratio by weight is feedstock of BC1 (Kwapinska et al., 2019).
Al-BC2 and Al-BC3 were slowly pyrolysed from a Al-DPS sample at 450℃ and 700℃ for an hour.
Fe-HC1, 2 and 3 are hydrochars using a Fe-DPS sample with feedwater in different pH.
A1 is from BC1 in furnace at 650℃ for 3 h.
Three types of struvites were precipitated from dairy processing wastewater.
* EU Fertilising Products Regulation (EU, 2019).
 High P concentration of chars, ash and struvite.
 Low N concentration of chars and ash due to high temperature combustion.
 Struvites has very low heavy metal content.
 Chars and ash has high heavy metal concentration than their feedstocks.
 Regulated heavy metals are all lower than the upper limit of EU Fertilising Products
Regulation

12.  These products are highly variable in
terms of their nutrient-metal profiles
 Application rates calculated based on
soil P and nutrient and metal loading
rates
 A tool was developed for maximum legal
application rates for bio-based products
 Tool for safe land application of dairy
processing waste
Solutions: Calculation tool
* Shi, W., Fenton, O., Ashekuzzaman, S. M., Daly, K., Leahy, J. J., Khalaf, N., ... & Healy,
M. G. (2022). An examination of maximum legal application rates of dairy processing and
associated STRUBIAS fertilising products in agriculture. Journal of Environmental
Management, 301, 113880.

13.  Further studies on the emerging
contaminants
 Study on the fertiliser efficiency to get
optimised application rates
 Improve the calculation tool to avoid
excessive fertilisation and predict metal
accumulation
Future Studies
* Shi, W., Fenton, O., Ashekuzzaman, S. M., Daly, K., Leahy, J. J., Khalaf, N., ... & Healy,
M. G. (2022). An examination of maximum legal application rates of dairy processing and
associated STRUBIAS fertilising products in agriculture. Journal of Environmental
Management, 301, 113880.

14. Thank you
The REFLOW project has received funding from the European Union’s
Horizon 2020 research and innovation programme under the Marie
Skłodowska-Curie grant agreement No 814258.