David Tompkins, Aqua Enviro

1. DIGESTATE MANAGEMENT
– USES OF DIGESTATE
#UKADBiogas @adbioresources
CHAIR:
DR NICK CHEFFINS, PEAKHILL ASSOCIATES
PANEL:
DR MARY DIMAMBRO, CAMBRIDGE ECO
DR DAVID TOMPKINS, AQUA ENVIRO
DR QUINTON FIVELMAN, ADFERTECH

2. www.aquaenviro.co.uk
Digestate: is it worth it?
Dr David Tompkins
Organics Technical Manager, Aqua Enviro
UK AD & Biogas 2015

3. www.aquaenviro.co.uk
Overview
1. Inherent fertiliser value is modest…
a. …and even worse in the autumn
b. …although digestate can be more than
the sum of its parts
2. Waste-derived digestates do not so easily
lend themselves to ‘upgrading’
3. Can operators afford not to upgrade in the
long term?

4. www.aquaenviro.co.uk
http://www.vcm-mestverwerking.be/publicationfiles/ARBOR_Digestate_CaseStudyReport1.pdf
“Treatment of the raw digestate
cannot be financed from the output
revenues only, even if they would be
sold at the market price reflecting the
real fertilizing value of their
components.”
The problem of fertiliser value

5. www.aquaenviro.co.uk
The problem of fertiliser value
Nitrogen
(N)
Phosphate
(P2O5)
Potash
(K2O)
Total
Nutrient content (kg/m3) 3.0A 0.5B 2.0B
Fertiliser price (£/kg) 0.74 0.59 0.44
Nutrient value (m-3) £2.22 £0.30 £0.88 £3.40
50,000t plant (year-1) £110,000 £15,000 £44,000 £169,000
A = crop available N (spring bandspread application); B = totals

6. www.aquaenviro.co.uk
The problem of fertiliser value
Nitrogen
(N)
Phosphate
(P2O5)
Potash
(K2O)
Total
Nutrient content (kg/m3) 0.75A 0.5B 2.0B
Fertiliser price (£/kg) 0.74 0.59 0.44
Nutrient value (m-3) £0.56 £0.30 £0.88 £1.74
50,000t plant (year-1) £28,000 £15,000 £44,000 £87,000
A = crop available N (autumn bandspread application); B = totals

7. www.aquaenviro.co.uk

8. www.aquaenviro.co.uk
http://www.bbc.co.uk/iplayer/episode/b05x76kw/countryfile-warwickshire

9. www.aquaenviro.co.uk
“You need agriculture…
agriculture doesn’t need
you”
Andrew Bauer
Deputy Director of Policy,
NFUS

10. www.aquaenviro.co.uk
Withers et al. (2014) Feed the Crop Not the Soil:
Rethinking Phosphorus Management in the Food
Chain. Environ. Sci. Technol. 48: 6523−6530
http://www.telfordhomes.plc.uk/cityscape/gallery.cfm
http://www.lawnsmith.co.uk

11. www.aquaenviro.co.uk
In conclusion
1. Digestate has inherent nutrient value
a. This won’t cover cost of recovery
2. Fibre digestate has greater inherent value
a. But separation can be challenging
3. To guarantee a market you may need to
upgrade digestate anyway

12. www.aquaenviro.co.uk
Thank you
DavidTompkins@aquaenviro.co.uk
07703 331947

13. DIGESTATE MANAGEMENT
– USES OF DIGESTATE
#UKADBiogas @adbioresources
CHAIR:
DR NICK CHEFFINS, PEAKHILL ASSOCIATES
PANEL:
DR MARY DIMAMBRO, CAMBRIDGE ECO
DR DAVID TOMPKINS, AQUA ENVIRO
DR QUINTON FIVELMAN, ADFERTECH