John Walsh afpa7a@bangor.ac.uk Determining the real value of on-farm Anaerobic Digestion

John Walshafpa7a@bangor.ac.uk

Determining the real value of on-farm Anaerobic Digestion

Penderfynu gwir werth Treuliad Anaerobig (Anaerobic Digestion) ar y fferm

Measure crop yield

Measure leachate levels

Above findings will provide the basic information to determine accurate economic values for AD, for government and farmer

Aims and Objectives Nodau ac Amcanion

Two soil types◦ Conventional ◦ Organic

Grass and grass/clover mix established

5 treatments◦ Control; NPK; N; Fresh

slurry; Liquid digestate ◦ Normalised for N

content (150 kg ha-1)◦ Applied via surface

spreading

5 reps, 70% field capacity

Managed for 15 weeks Three harvests

Analysed for◦ Yield (crop)◦ Leachate: amount of N

and P present (soil)◦ Bacterial and fungal

growth (soil)

Methods Dulliau

Crop Yield Fresh slurry (FS) produced half the yield of

liquid digestate (LD) in 3 out of 4 treatments No difference in yield between LD and NPK

21.8.11 in 3 out of 4 treatments

Leachate LD and FS statistically the same level of

leachate NPK had more leachate than LD in all

treatments

Results Canlyniadau

Crop Yield Cynnyrch Cnwd

Digestate had double the yield of fresh cow slurry in 3 out of the 4 treatments

NPK 21.8.11 cost £281/tonne At a rate of 150 kg N /ha, digestate saved

£103/ha on fertilizer expenditure

Simple valuation: introduction of AD doubles the value of a farmers organic fertilizer

Fertiliser Saving Arbed Gwrtaith

Treatment

OLDG ONPKG OLDC ONPKC HLDG HNPKG HLDC HNPKC

mg

/L

NO

3 -

0

20

40

60

80

100

Mg/L

NO

3-

Total Nitrate Cyfanswm Nitrad

Treatment

OLDG ONPKG OLDC ONPKC HLDG HNPKG HLDC HNPKC

mg

/L N

H4 +

0

2

4

6

8

10

12

14

16

18

Total Ammonium Cyfanswm Amoniwm

Treatment

OLDG ONPKG OLDC ONPKC HLDG HNPKG HLDC HNPKC

mg

/L

P2 O

5

0

1

2

3

4

5

6

mg/L

PO

4

Total Phosphate Cyfanswm Ffosffad

AD: 500 kW 11.5 (p/kWh) AD: 500 kW 9.0 (p/kWh)

Wind: 15 kW – 100 kW 24.1 (p/kWh) Wind: 100 kW – 500 kW 18.8 (p/kWh) Wind: 500 kW – 1.5 MW 9.4 (p/kWh)

Current FITs price doesn’t reflect all benefits of AD

Positive externalities of AD have not been valued

Feed-in Tariffs Tariffau I’w Cynnwys

Doubles the value of fertilizer produced on farm.

FIT’s and ROC’s under priced for AD

Double advantage of reducing fossil fuel usage and cutting down on current GHG emissions Only renewable energy source to do this

More nitrogen and phosphorus stays in the soil than inorganic fertilizers

Conclusions: AD Casgliadau: AD

My supervisors for guidance: Prysor Williams, Gareth Edwards-Jones, Davey Jones

Acknowledgements Diolchiadau