Phosphorus Surplus & Mitigation Strategies John Bailey & Peter Frost Contributors of data and information: Alex Higgins, Conrad Ferris, Francis Lively & Elizabeth Magowan – AFBI Paul Caskie & Paul Keating - DARD Wendy 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

P Balance: Magnitude, Makeup & Mitigation

 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) Soluble Reactive P (mg P/litre) Soluble Reactive P (mean monthly) 127 Rivers P Balance: Magnitude, Makeup & Mitigation

 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) Soluble Reactive P (mg P/litre) minus = Phosphorus (kg 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 = P Balance: Magnitude, Makeup & Mitigation

(17.7) (9.1) (11.3) National P Balance (kg P/ha) Northern Ireland P Balance Soluble Reactive P (mg P/litre) 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 P Balance: Magnitude, Makeup & Mitigation

Northern Ireland P Balance (kg P/ha)  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: 1 st - Dairy – 37% 2 nd - Poultry – 33% 3 rd - Beef & Sheep – 24% 4 th - Pigs – 5% 6 th - Arable 1% 37% 33% 5% 24% 38% 37% 39% 22% 18% 34% 4% 3% P Balance: Magnitude, Makeup & Mitigation 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 Phosphorus Inputs (tonnes) Total P Inputs as Feed and Fertiliser P Balance: Magnitude, Makeup & Mitigation

Concentrate Inputs (tonnes)  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 Phosphorus Inputs (tonnes) Total P Inputs as Feed and Fertiliser Total Feed Inputs per Sector P Balance: Magnitude, Makeup & Mitigation

Fertiliser- P Inputs (tonnes)  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 P Balance: Magnitude, Makeup & Mitigation

Fertiliser- P Inputs (tonnes)  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) Fertiliser- P Inputs (kg P/ha) Mean Rates of Fertiliser P Applied per Sector (kg/ha) P Balance: Magnitude, Makeup & Mitigation

National P Balance (kg P/ha)  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 P Balance: Magnitude, Makeup & Mitigation

National P Balance (kg P/ha) Sector P Balance (kg P/ha)  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 P Balance: Magnitude, Makeup & Mitigation

Potential for Manure-P Re-distribution/Reduction 1. Redistribution Across the Region

Potential for Manure-P Re-distribution/Reduction  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/Reduction 1. Redistribution Across the Region

Potential for Manure-P Re-distribution/Reduction  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 Potential for Manure-P Re-distribution/Reduction

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 Potential for Manure-P Re-distribution/Reduction Phosphorus (tonnes) Sector Crop P Requirements & Manure-P Production Dairy Beef & Sheep 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 Potential for Manure-P Re-distribution/Reduction Phosphorus (tonnes) Sector Crop P Requirements & Manure-P Production Dairy Beef & Sheep P & P Phosphorus (tonnes) 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 Dairy Beef & Sheep P & P

P Balance 4.5 kg P/haP Balance 9.5 kg P/haP 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/Reduction 3. Redistribution Across Farms

Technologies Aiding Manure-P Export

(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 Technologies Aiding Manure-P Export

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% Technologies Aiding Manure-P Export

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 Technologies Aiding Manure-P Export

Dried fibre Separated fibre Precipitated struvite crystals (left) Granular struvite pellets (right) MINORGA® granular organic fertiliser with an N-P-K ratio of 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 Technologies Aiding Manure-P Export

Key Messages 1.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!