What can I do in the short term?
More frequent manure removal from laying hen housing with belt clean systems
WHY? On a weekly manure removal system, measurements have shown that ammonia emissions can increase substantially on the last two days prior to manure removal. If the laying hen houses are cleaned out on a more regular basis (twice weekly) the emitting source of ammonia will be removed before it gets to peak emitting phase.
HOW? Increase the frequency of cleaning to twice weekly rather than once per week. This system is only applicable to those houses which have belt clean systems. It is important when spreading this manure to incorporate it into the soil to further reduce losses.
WHAT IS THE EFFECT? Ammonia emissions would be reduced by up to 50% compared with weekly manure removal. The material removed would have a higher readily available N content so ammonia emissions during storage and following land spreading would be higher, but by a lesser amount. Overall manure N use efficiency would be improved. Air quality within the house including odorant concentrations should be improved.
WHAT IS THE INDICATIVE COST? £0.10/t of manure based on the increased frequency of running the belt systems. (2011)
Adopt (batch) storage of solid manures
WHY? FIOs die off during storage, as a result there are fewer microbial pathogens in the spread manure and lower nutrient losses in run off. The readily available N content of stored FYM is lower than in “fresh” FYM due to losses during storage which will lessen nitrate leaching losses and ammonia emissions.
HOW? Store fresh solid manure in separate batches for at least 90 days before land spreading. At present around 30% of FYM and 60% of poultry manure is applied “fresh” to land.
WHAT IS THE EFFECT? Nitrate leaching losses would be reduced because of the lower readily available N content of the manure and associated Nitrous Oxide and Ammonia emissions would be reduced at land spreading. Ammonia emissions would be increased during storage but by a lower amount. The effects on nitrous oxide balances at the farm scale are uncertain.
WHAT IS THE INDICATIVE COST? £1/t of solid manure based on construction of concrete pad / leachate collection facilities and associated areas for vehicle movements. (2011)
What can I do in the medium term?
Minimise the volume of dirty water (and slurry) produced
WHY? Minimising the volume of dirty water produced reduces the volume to be stored and spread. Farms will then be less likely to run out of storage space and be forced to spread dirty water or slurry at times where there is a high risk of runoff.
HOW? Minimise the volume of dirty water produced by: minimising unnecessary dirty yard areas, avoiding excessive use of water when washing down yards, preventing unnecessary mixing with clean water from uncovered clean yards and roofs, or roofing over yard areas and covering dirty water and slurry stores.
WHAT ARE THE EFFECTS? Nitrate leaching losses would be reduced by a small (1%) amount and phosphate losses by a small (2%) amount due to the better timing of dirty water and slurry applications through increased storage capacity.
WHAT IS THE INDICATIVE COST? £40/m2of roof, based on additional roofing over dirty concrete areas and diversion of clean water. (2011)
Compost solid manure
WHY? As part of the composting process the manure is “sanitised” and the readily available N content is reduced, lowering the risk of manure borne pollutants and nitrate losses when the composted material is spread to land.
HOW? Encourage the breakdown of solid manure by active composting. Turn the solid manure windrow twice in the first 7 days of composting to facilitate aeration and the development of high temperatures within the windrow.
WHAT ARE THE EFFECTS? Nitrate leaching losses would be reduced as a result of the lower readily available N content of the manure and the lower amounts of total N in FYM and poultry manure. At land spreading nitrous oxide and ammonia losses would also be reduced. Ammonia emissions would be increased during storage but by a lower amount. Effects on the nitrous oxide balance at the farm scale are uncertain.
WHAT IS THE INDICATIVE COST? £2.60 / tonne of solid manure based on the turning of FYM windrows twice using a tractor and front end loader. (2011)
Store solid manure heaps on an impermeable base and collect leachate
WHY? The impermeable base and leachate collection prevents the direct loss of pollutants in surface runoff and drainflow. If manure heaps are stored directly on the soil surface leachate from the heaps will seep into the soil and / or flow over the soil surface in response to rainfall. Storage on an impermeable base will prevent seepage and accumulation of nutrients in the soil below the heap and will reduce soil compaction from farm machinery forming and spreading field heaps.
HOW? This method is of most benefit on farms with medium or heavy soil. Construct a concrete pad on which to store the heap. The leachate collected can be spread at a later date when soil conditions are suitable and the nutrients can be utilised by crops or be added back into the heap or into a slurry store.
WHAT ARE THE EFFECTS? A small (5%) reduction in nitrate leaching losses and indirect nitrous oxide emissions. Ammonia emissions would be increased as a result of conserved N in recycled leachate. Overall manure N use efficiency would be increased and artificial fertiliser N inputs reduced. Phosphate losses would be reduced by a small (2%) amount.
WHAT IS THE INDICATIVE COST? £1/t of solid manure based on construction of a concrete pad and leachate collection facilities, and areas for vehicle movement. (2011)
Cover solid manure stores with sheeting
WHY? Sheeting heaps provides a physical barrier preventing the release of ammonia from the manure to the air.
HOW? Cover heaps with heavy duty polythene sheet. This method is less appropriate for management systems that involve regular additions of manure to existing heaps. It is most effective when combined with incorporating manure into the soil when spread.
WHAT IS THE EFFECT? A reduction in ammonia emissions as high as 90% from storage when covered with an impermeable sheet, although nitrous oxide emissions are likely to be increased during storage. Overall nitrate losses through leaching and ammonia emissions would be decreased. Effects on balance of nitrous oxide emissions at farm scale are uncertain. Overall manure N use efficiency would be increased and artificial fertiliser N inputs reduced. Phosphate losses would be reduced due to the production of less leachate. Methane emissions would be increased due to the anaerobic conditions under the sheet.
WHAT IS THE INDICATIVE COST? £0.50/t of solid manure based on provision of plastic sheeting and additional management time. (2011)
Transport manure to neighbouring farms
WHY? Where there is an excess of manures (and therefore of nutrients) manures can be exported to neighbouring farmland that may have spare livestock manure N capacity. This allows exporting farms to balance nutrient inputs with the capacity of the crops to use them.
HOW? This method will be most useful on farms in NVZs where livestock manure N loadings exceed 170kg total N per ha each year. It will be most easy to implement when receiving farm holdings are in close proximity.
WHAT ARE THE EFFECTS? A reduction in nitrate leaching losses on the exporting farm and increased (to a lesser extent) on the receiving farm with capacity. Ammonia and nitrous oxide emissions and phosphate losses would also be reduced on the exporting farm.
WHAT IS THE INDICATIVE COST? £5 / m3of slurry; £4/t of solid manure based on the need to transport manure over 5km. (2011)
What can I do in the long term?
Reduce dietary N and P intakes
WHY? Avoiding excess dietary N and P in the diet and / or making dietary N and P more available allows nutrient concentrations in the diet to be reduced without affecting animal performance. This will mean that the amount of N and P excreted either directly to fields or via handled manures is reduced.
HOW? Adjust the composition of livestock diets to reduce the total intake of N and P per unit of production. This may be achieved by restricting diets to recommended levels of N and P, or by changing the composition of the diet to increase the proportion of dietary N and P utilised by the animal. Benefits are likely to be greatest on dairy, pig and poultry units.
WHAT ARE THE EFFECTS? Nitrate leaching losses, nitrous oxide and ammonia emissions would be reduced by up to 10%. Phosphate losses would be reduced by up to 10% and in the longer term particulate P losses would be reduced.
WHAT IS THE INDICATIVE COST? £600 per farm (based on the farm typology used in this study) calculated on additional feed and management inputs to avoid excess N and P. (2011)
Convert caged laying hen housing from deep pit storage to belt manure removal
WHY? Ammonia emissions from a deep pit laying hen house often occur from the accumulated manure in the deep pit storage area. Operating a belt removal system weekly will allow most of the ammonia emissions to be emitted after the manure has been removed from the house.
HOW? Replace deep pit manure storage with a series of belts below each tier of cages which remove manure from the house. This is most appropriate for new build units. The practicalities of converting existing buildings will depend on their design and age.
WHAT ARE THE EFFECTS? Ammonia emissions from houses with belt clean systems are around 50% lower than from deep pit laying houses. There would be greater readily available N content of the manure and as such the ammonia emissions during storage and following land spreading would be increased by a lower amount. Overall manure N use would be increased and artificial fertiliser N inputs reduced. Air quality within the house would be improved.
WHAT IS THE INDICATIVE COST? £35 /t of manure based on the installation of new cages and belts. (2011)
In house poultry manure drying
WHY? Drying the poultry litter to achieve a dry matter content of 60-80% will inhibit the hydrolysis of uric acid N in manure reducing ammonia emissions.
HOW? Install ventilation or drying systems to reduce the moisture content of laying hen manure or poultry litter within the house.
WHAT ARE THE EFFECTS? Ammonia emissions would be reduced by up to 50% from the poultry housing. Overall manure N use efficiency would be increased and artificial fertiliser N inputs reduced. Air quality within the house would also be improved.
WHAT IS THE INDICATIVE COST? £0.50/t of manure based on the installation and running of drying equipment. (2011)
Anaerobic digestion of livestock manures
WHY? Methane generated from livestock manures during AD can be used to produce heat and power, and to replace fossil fuel use. Methane emissions during subsequent manure storage prior to land spreading are also reduced.
HOW? Farms with significant numbers of housed livestock would be the most suitable for on farm installations because of the significant costs involved.
WHAT ARE THE EFFECTS? Methane emissions from slurry storage would be reduced, plus heat and power would be produced. An increase in the readily available N content of the digestate would increase ammonia emissions during storage and following land spreading. Nitrate leaching losses would be increased by a small amount. Overall manure N use efficiency would be increased.
WHAT IS THE INDICATIVE COST? £55,000 per farm type used in the study for the capital costs. (2011)
Use poultry litter additives
WHY? Poultry litter contains high concentrations of P and readily available N. Research has shown that P concentrations in surface runoff are closely related to the soluble P content of the manure. Chemical additions to the poultry litter can change the phosphorus into a form that is not water soluble as well as reducing ammonia emissions which can result in heavier birds, better feed conversion efficiency and lower mortality.
HOW? Add aluminium sulphate to poultry litter during housing to reduce the pH of the litter.
WHAT ARE THE EFFECTS? Ammonia emission reductions of around 70% from housing, as well as reductions during storage and following spreading as a result of the low litter pH. As a result of the higher readily available N content of the poultry litter nitrate leaching losses and nitrous oxide emissions would be increased. Overall manure N use efficiency would be increased and artificial N inputs reduced.
WHAT IS THE INDICATIVE COST? £3/t of litter based on the purchase of aluminium sulphate and addition to poultry litter. (2011)