Phosphorus Surplus & Mitigation Strategies John Bailey & Peter Frost Contributors of data and information: Alex Higgins, Conrad Ferris, Francis Lively

Phosphorus Surplus & Mitigation Strategies

John Bailey & Peter FrostContributors of data and information:

Alex Higgins, Conrad Ferris, Francis Lively & Elizabeth Magowan – AFBI

Paul Caskie & Paul Keating - DARDWendy McKinley, Robert Bailie & Catherine McGuire - NIEA

John Thompson & Sons Ltd and Moy Park

Overview

P Balance: Magnitude, Makeup & Mitigation

Potential for Manure-P Re-distribution/Reduction

Technologies Aiding Manure-P Export

Key Messages


0

0.05

0.1

0.15

0.2

0.25

1998 2002 2006 2010 2014

2003

2009

2014

2003, 2009 and 2014 were selected as reference years – i.e. when river SRP levels were either relatively high (2003), relatively low (2009), or ‘perhaps’ on an upward trajectory (2014)

So

lub

le R

eact

ive

P (

mg

P/l

itre

) Soluble Reactive P (mean monthly) 127 Rivers


0

0.05

0.1

0.15

0.2

0.25

1998 2002 2006 2010 2014

2003

2009

2014

2003, 2009 and 2014 were selected as reference years – i.e. when river SRP levels were either relatively high (2003), relatively low (2009), or ‘perhaps’ on an upward trajectory (2014)

For each of these 3 years, Regional NI Agricultural P Balances were calculated for the Agricultural land area – (excluding rough grazing etc)

So

lub

le R

eact

ive

P (

mg

P/l

itre

)

Inputs Outputs Balance0

5

10

15

20

25

minus =

Ph

os

ph

oru

s (k

g P

/ha

)

Feed-P

Dairy,Beef,

Sheep, Pig &

Poultry

Fert-P

Product

Milk, Meat,Eggs & Crops

Surplus

Soluble Reactive P (mean monthly) 127 Rivers

Northern Ireland P Balance Calculation

minus =


0

0.05

0.1

0.15

0.2

0.25

1998 2002 2006 2010 2014

2003

2009

2014

2003 2009 20140

4

8

12

16

20 (17.7)

(9.1)(11.3)

Nat

ion

al P

Bal

ance

(kg

P/h

a)

Northern Ireland P Balance

So

lub

le R

eact

ive

P (

mg

P/l

itre

) Soluble Reactive P (mean monthly) 127 Rivers 2003, 2009 and 2014 were

selected as reference years – i.e. when river SRP levels were either relatively high (2003), relatively low (2009), or ‘perhaps’ on an upward trajectory (2014)

For each of these 3 years, Regional NI Agricultural P Balances were calculated for the Agricultural land area – (excluding rough grazing etc)

As shown in the bar chart, the P balance or surplus declined appreciably between 2003 and 2009, but has since crept up again


No

rth

ern

Ire

lan

d P

Bal

ance

(kg

P/h

a)

2003 2009 20140

2

4

6

8

10

12

14

16

18ArablePigPoultryBeef &SheepDairy

Using Farm Census and DARD Survey statistics plus Industry information, the NI P Balance was apportioned to each sector (Beef & Sheep amalgamated)

Currently (2014), the sectors contributing most to the regional P surplus are:

1st - Dairy – 37%2nd - Poultry – 33%3rd - Beef & Sheep – 24%4th - Pigs – 5%6th - Arable 1%37%

33%

5%

24%

38%

37%

39%

22%

18%

34%

4% 3%


Northern Ireland P Balance Broken Down by Sector

Total P inputs were separated into Fertiliser and Feed P inputs

While Fertiliser P inputs declined between 2003 and 2009 and increased again by 2014, feed P inputs remained almost static

The reason for this was that although concentrate feed inputs increased, particularly, in the Dairy and Poultry Sectors, the concentrations of P in most concentrates declined

2003 2009 20140

5000

10000

15000

20000

25000Fertiliser PFeed P

Ph

os

ph

oru

s In

pu

ts (

ton

nes

)

Total P Inputs as Feed and Fertiliser


2003 2009 20140

200

400

600

800

1000

1200 DairyPoultryBeef & Sheep

Co

nce

ntr

ate

In

pu

ts (

ton

nes

)

Total P inputs were separated into Fertiliser and Feed P inputs

While Fertiliser P inputs declined between 2003 and 2009 and increased again by 2014, feed P inputs remained almost static

The reason for this was that although concentrate feed inputs increased, particularly, in the Dairy and Poultry Sectors, the concentrations of P in most concentrates declined

Therefore, the recent increase in the NI P Balance is owed primarily to the increased use of Fertiliser P since 2009

2003 2009 20140

5000

10000

15000

20000

25000Fertiliser PFeed P

Ph

os

ph

oru

s In

pu

ts (

ton

nes

)

Total P Inputs as Feed and Fertiliser

Total Feed Inputs per Sector


2003 2009 20140

2000

4000

6000

8000

10000

ArableBeef &SheepDairy

Fer

tili

ser-

P I

np

uts

(to

nn

es) The chart shows total tonnages of

Fertiliser P inputs for the 3 land-based farming sectors

In all 3 sectors, inputs declined between 2003 and 2009, and then increased again but only in the Dairy and Beef & Sheep Sectors

But there is really little need for Fertiliser P in these 2 sectors

Fertiliser P Inputs per Sector (tons)

7


2003 2009 20140

2000

4000

6000

8000

10000

ArableBeef &SheepDairy

Fer

tili

ser-

P I

np

uts

(to

nn

es) The chart shows total tonnages of

Fertiliser P inputs for the 3 land-based farming sectors

In all 3 sectors, inputs declined between 2003 and 2009, and then increased again but only in the Dairy and Beef & Sheep Sectors

But there is really little need for Fertiliser P in these 2 sectors

Although total tonnages of P inputs were least in the arable sector, the average rates applied were highest

It should be possible to reduce the Arable rate by 50% since Pig and Poultry manure-P can be used in place of Fertiliser P

Fertiliser P Inputs per Sector (tons)

2003 2009 20150

10

20

30

40

50

ArableBeef & SheepDairy

Fer

tili

ser-

P I

np

uts

(k

g P

/ha

)

Mean Rates of Fertiliser P Applied per Sector (kg/ha)

17

4

15

24

13

7


Nat

ion

al P

Bal

ance

(kg

P/h

a)

2003 2009 20140

4

8

12

16

20Fert PReduced Fert P

6.9

17.7

9.1 11.3

6.5 6.9

Elimination of all Fertiliser P in the Dairy and Beef & Sheep Sectors, and a 50% reduction in the Arable Sector, would reduce the NI P balance to < 7 kg P/ha

BUT, this may not be sufficient to bring water-bodies to Good Water Quality Status

NI P Balance With & Without Reductions in Fertiliser P


Nat

ion

al P

Bal

ance

(kg

P/h

a)

2003 2009 20140

4

8

12

16

20Fert PReduced Fert P

6.9

17.7

9.1 11.3

6.5 6.9

2003 2009 20140

2

4

6

8

10

12

14

16DairyBeef & Sheep

Sec

tor

P B

alan

ce (

kg

P/h

a)

12.1 12.0 13.3

Elimination of all Fertiliser P in the Dairy and Beef & Sheep Sectors, and a 50% reduction in the Arable Sector, would reduce the NI P balance to < 7 kg P/ha

BUT, this may not be sufficient to bring water-bodies to Good Water Quality Status

Sector P balances – based on land areas occupied by each sector – are shown in the adjacent chart

Even without fertiliser P the Dairy Sector has a high P surplus (>13 kg P/ha)

NI P Balance With & Without Reductions in Fertiliser P

Sector P Balances With Reduced Fertiliser P

Pig & Poultry Manure


Potential for Manure-P Re-distribution/Reduction1. Redistribution Across the Region


One mitigation option may be to re-distribute dairy manure-P away from areas of high soil P status to areas where P is under-supplied

However, much of the land of low soil P status – and ‘supposedly’ under-supplied with P, is in fact upland, wetland or rough grazing areas, where there is actually no need for additional P inputs to support agricultural production

There is a risk that moving manure-P to such areas would not improve production but rather would needlessly increase the P loading of this land – and damage sensitive habitats and ecosystems

1. Redistribution Across the Region

The (NIEA) Map of Trophic Classification of River Water Bodies, shows that areas of High or Good Water Quality Status are in upland or westerly areas

The areas where water bodies are of Moderate or Poor Water Quality Status, correspond broadly with areas of high soil P status (Index 3 and above)

Potential for Manure-P Re-distribution/Reduction1. Redistribution Across the Region


The (NIEA) Map of Trophic Classification of River Water Bodies, shows that areas of High or Good Water Quality Status are in upland or westerly areas

The areas where water bodies are of Moderate or Poor Water Quality Status, correspond broadly with areas of high soil P status (Index 3 and above)

They also correspond with areas of highest Dairy P excretion rates

Redistributing manure-P away from areas of highest dairying intensity could risk causing reductions in water quality in the receiving areas

1. Redistribution Across the Region

2. Between Sectors


2. Between Sectors Crop P requirements were calculated and also manure-P production per sector

It is clear the Dairy manure-P is more than TWICE the sector P requirement – and there is NO scope for redistribution to other sectors

About 50% of Pig and Poultry manure is eliminating P deficits in the Beef & Sheep and Arable Sectors – BUT the un-required (50%) should be Exported

If the Dairy Sector P balance is reduced to 6 kg P/ha, by increasing milk from grass, eventually the gap between P requirement and manure-P production will close


Dairy Beef & Sheep Arable0

2000

4000

6000

8000

10000

P RequirementManure-PFertiliser P

Ph

os

ph

oru

s (t

on

nes

) Sector Crop P Requirements & Manure-P Production - 2014

Da

iry

Be

ef

& S

he

ep

P & P

P & P

2. Between Sectors Crop P requirements were calculated and also manure-P production per sector

It is clear the Dairy manure-P is more than TWICE the sector P requirement – and there is NO scope for redistribution to other sectors

About 50% of Pig and Poultry manure is eliminating P deficits in the Beef & Sheep and Arable Sectors – BUT the un-required (50%) should be Exported

If the Dairy Sector P balance is reduced to 6 kg P/ha, by increasing milk from grass, eventually the gap between P requirement and manure-P production will close



2000

4000

6000

8000

10000


Ph

os

ph

oru

s (t

on

nes

) Sector Crop P Requirements & Manure-P Production - 2014

Da

iry

Be

ef

& S

he

ep

P & P

P & P


2000

4000

6000

8000

10000


Ph

os

ph

oru

s (t

on

nes

)

Sector Crop P Requirements & Manure-P Production when Dairy Sector P Balance is 6 kg P/ha and 50% of

Poultry Manure/Litter is Exported

Da

iry

Be

ef

& S

he

ep

P & P

P & P

P Balance 4.5 kg P/ha P Balance 9.5 kg P/ha P Balance 12.5 kg P/ha

Within individual dairy farms, there is definitely scope for manure-P redistribution from high P soils to those under-supplied with P

However, if the farm P balance > 10 kg P/ha, the P status of the entire area may be so high that within farm re-distribution will be of little benefit

Potential for Manure-P Re-distribution/Reduction3. Redistribution Across Farms


(a) Run down screen

(b) Brushed screen

(d) Decanting centrifuge

(e) Reverse osmosis

(c) Screw press

The first step in recovering P from manures is mechanical separation

Mechanical separation of whole slurries produces a fraction with an increased dry matter concentration (solid fraction) and a liquid fraction with a lower dry matter concentration than whole slurry.

A range of separation technologies are available

Screw press and centrifuge are both common in Europe


Fresh matter (%) Separation Efficiency (%)

TS NH4-N TN PO4-P K

Solid fraction 10.0 48.1 9.2 17.0 21.8 10.0

Liquid fraction 90.0 51.9 82.0 83.0 78.0 90.0

Percentage of component in total slurry input that was partitioned to each fraction

(adapted from KTBL, 2008)

Typical performance of a Screw Press

The advantages of a screw press separator compared to the decanter centrifuge are the low capital costs (£20k approximately) and low power requirements (0.4 – 0.5 kWh/m³)

Efficiency of P separation into the solid phase, however, is only 22%


Separator efficiency(%) Separated liquidvolume change

(% input volume)Solid fraction TS TN NH4-N TP K

With chemical 65.4 40.6 16.6 82.3 14.9 +9.1No chemical 50.9 24.6 13.7 63.9 13.0 -12.5

Percentage of component in total slurry input that was partitioned to solid fraction

(Frost and Gilkinson, 2007)

Decanting Centrifuge Performance (AFBI)

Decanting centrifuges are particularly effective at separating the majority of the phosphorus into the solid fraction

The power requirement of decanting centrifuges (3 – 5 kWh/m³) is high relative to other mechanical separators - the capital cost could be in the order of £120k

Efficiency of P separation into the solid phase is > 60% even without coagulants


Dried fibre

Separated fibre

Precipitated struvite crystals (left)Granular struvite pellets (right)

MINORGA®granular organic fertiliserwith an N-P-K ratio of 10-2-5

Further Processing of Anaerobic Digestate (and potentially slurries)

Processing of the solid fraction can be carried out to produce compost or pellets for land application and export

After mechanical separation the liquid fraction still contains large quantities of nutrients and solid material, depending on the type of separator used

The liquid fraction can be processed further to recover P by struvite precipitation.

Techniques involving membranes can be used to concentrate nutrients e.g. ultra-filtration and reverse osmosis


Key Messages1. The recent increase in the NI P balance is due primarily to increased use

of fertiliser P in the Dairy, Beef & Sheep Sectors

2. Eliminating fertiliser P use in these ruminant sectors will, nevertheless, still leave the Dairy Sector with an unnecessary high, and potentially environmentally detrimental, P surplus of some 13 kg P/ha

3. Manure P production in the Dairy Sector is currently more than DOUBLE the amount needed to meet the Sector’s grassland P requirement

4. Redistributing manure-P away from areas of highest dairying intensity (if feasible) could cause reductions in water quality in the receiving areas

5. Within individual farms, manure-P may be beneficially re-distributed away from soils of high P status provided land conditions in receiving areas are suitable – but redistribution does NOT reduce farm P surpluses

6. If fertiliser P is eliminated from the ruminant sectors, if the average Dairy Sector P surplus is reduced to 6 kg P/ha, if fertiliser P input to the Arable Sector is reduced by 50%, and if 50% of Pig and Poultry manure is exported, then manure-P production will eventually match crop and grassland P requirements across all land-based sectors

7. Technologies are available to help partition manure P into solid phase forms suitable for export - but costs can be high!

Documents

Phosphorus Surplus & Mitigation Strategies John Bailey & Peter Frost Contributors of data and information: Alex Higgins, Conrad Ferris, Francis Lively