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Det er et mål å redusere klimagassutslipp relatert til jordbruket. Bedre gjødselhandtering og fermentering av bløtgjødsel i biogassanlegg er foreslått som tiltak som vil bidra til dette. En stor utfordring for estimatene i det nasjonale utslippsregnskapet er at det er gjort svært få målinger under norske forhold på utslipp av lystgass (N2O), ammoniakk (NH3) og metan (CH4). Fordi utslipp av alle gasser øker med temperatur og fordi temperaturen jevnt over er lavere i Norge enn i mange andre land, er det viktig å få mer kunnskap om hvor store de faktiske utslippene er ved ulik temperatur og lagerforhold av husdyrgjødsel i Norge. Derfor har vi i 2019 og 2020 målt utslipp av klimagasser fra utendørs gjødselkummer med storfegjødsel. I 2019 var det tre kummer som ble undersøkt og i 2020 ble antallet utvidet til fem. To av gjødselkummene var åpne, to hadde tak og en Plany flytedekke. Alle var plassert på gårder med melkeproduksjon. Metodikken vi brukte for å ta gassprøver fra gjødselkummene var basert på tysk utstyr for å måle gassutslipp fra vandige overflater med et kammer som samler opp gass kombinert med gassprøvetaking ved hjelp av sprøyter. Gassprøvene ble analysert for innhold av CO2, CH4 og N2O ved hjelp av gasskromatograf. I tillegg ble temperaturen i gjødsla målt i to ulike dyp, det ble tatt gjødselprøver fra kummene, prøver av eventuell skorpe og tykkelsen på skorpe ble målt. Gjødselprøvene ble analysert for næringsinnhold og pH. Det var utfordringer med temperaturregisteringer. En del sensorer og loggere tålte ikke forholdene i gjødsellageret over tid eller ble ødelagt på andre måter. Ved 150 cm dyp var temperaturen i gjødsla ganske stabil. Gjødsla var kaldere enn lufta når det var varmt i lufta og varmere når det var kaldt i lufta. Vi registrerte aldri høyere temperatur i gjødsellageret enn 15°C. Av utslippene vi registrerte var det metanutslipp som betydde mest for global oppvarming. Målt i CO2 ekvivalenter var utslippene av CO2 og N2O svært mye lavere enn CH4 utslipp. Gjennomsnittlig utslipp av metan fra gjødselkummene var 12 g CH4 per m3 gjødsel per døgn (variasjon 0,1 – 28). Dette er i samme størrelsesorden som resultater fra andre skandinaviske undersøkelser. Når lufttemperaturen var under 14 °C, var metanutslippene lave. Metanutslippene per enhet organisk stoff (VS) var høye når det var lite gjødsel i kummen i forhold til overflaten samtidig som det var varmt. Det var tendens til lavere metanutslipp per enhet organisk stoff ved økende mengde gjødsel, og når gjødsla ble tilført i bunnen av kummen. Lave registrerte utslipp av metan der ny gjødsel ble tilført i bunn selv ved høy lufttemperatur kan skyldes at temperaturen i gjødsla har holdt seg lavere da det var store kummer og det ikke ble tilført ny gjødsel ovenfra. Vi hadde forventet høyere tørrstoffinnhold og porøsitet i skorpa og lavere metanutslipp der ny gjødsel ble tilført i bunn og det samtidig var tak over kummen som beskyttet mot nedbør, men våre undersøkelser kan så langt hverken bekrefte eller avkrefte dette. Årsaken til lave utslipp av lystgass var sannsynligvis at det enten ikke var skorpe på gjødsla eller skorpa var våt og kompakt og dermed ikke porøs selv under tak. Ammonium ble dermed ikke oksidert til lystgass. Sannsynligvis av samme årsak, fant vi heller ikke reduserte metanutslipp med økende skorpetykkelse som vi hadde forventet, da skorpa heller ikke var porøs nok til at CH4 ble oksidert og dermed omdannet til CO2. Teoretiske studier av biogassanlegg og noen målinger gjort i Norge og i utlandet understreker behovet for tett oppfølging av etablerte biogassanlegg. Det vil si gjøre målinger og justeringer for drift og bruk av biorest slik at man oppnår beregnet og ønsket positiv effekt på klimaet. Ved å lagre bløtgjødsel og biorest kjølig, kan utslippene av metan og ammoniakk begrenses. Praktiske råd kan være å minimere mengden gjødsel i kummen om sommeren, og når ny kum skal bygges grave den ned og sørge for at gjødselkummen er mest mulig i skygge. Total tømming av lagret og rengjøring innen ny påfylling kan være en effektiv strategi for å redusere utslipp av metan. Årsaken er at gjødselresten kan fungere som et inokolum og stimulere metandannelsen når lagret fylles med fersk gjødsel. Ved biogassanlegg er metanproduksjonen allerede stimulert når bioresten kommer inn i lageret. Nedkjøling eller tett kum er derfor ekstra viktig her. Surgjøring av bløtgjødsel til ca pH 5,5, oftest med svovelsyre, reduserer både NH3- og CH4-utslipp under lagring. Surgjøring er hittil ikke mye brukt i Norge da det har praktiske utfordringer. Tak eller dekke på gjødselkummene hindrer nedbør i kummen, og dermed øker lagerkapasiteten samtidig som det blir mindre vann som må kjøres ut. Hvor mange timer kjøring som spares ved utkjøring av gjødsla avhenger av størrelsen på gjødselkummen, størrelse på gjødselvogna og avstanden til arealene som skal gjødsles. Økonomisk kostnad til tak eller dekke avhenger av diameteren på kummen. Kostnaden med å montere tak på en kum med diameter på 25 meter var ca 340 000 kr (regnet i 2020-priser).

This report presents instructions for manure sampling and analysis produced within the project MANURE STANDARDS financed by Interreg Baltic Sea Region Programme (2014-2020). The project developed joint guidelines for taking representative manure samples, recommendations for manure analysis in the laboratories and a farm-level calculation tool for farm-specific manure mass balance calculation. All materials areavailable in English at: https://www.luke.fi/manurestandards/en/frontpage/

When developing new types of fertilizers, it is important that they have chemical and physical properties that enable good spreading precision with machine types available on the market, otherwise the products will not be used. This study included two phosphorus products made from different phosphorus extraction techniques: 1) granules (EkoBalans) consisting mainly of struvite, precipitated from drainage reject water from wastewater treatment plants, with addition of ammonium sulphate and potassium chloride, and 2) pellets (Outotec) consisting of ASH DEC P-fertilizer product made of ash from incinerated sludge. Comparisons of these products were conducted with current market fertilizer products Axan (granules) and Biofer (pellets). Physical properties of the phosphorus products and the market products were determined in terms of grain size, dimensions (pellets), strength, flow properties and bulk density. Even simpler field techniques for determining grain size and strength were used during the spreading tests. Spreader tests were conducted in the field to evaluate spreading patterns using a centrifugal spreader, one of the most common fertilizer spreaders in agriculture. Test equipment used for field testing fertilizer spreaders was used. Trays were placed in rows perpendicular to the tramline to collect the fertilizer granules over the full swath width while passing with the spreader. The contents of each tray were collected and measured to obtain scatter figures from which the spreading evenness was calculated at different effective swath widths. The general conclusion was that both tested products were spreadable with today's centrifugal spreader. However, granules performed better than pellets mainly probably because the granules had a higher mass flow, which reduces the risk of vault formation and stops in the discharge. Both commercial products, Axan and Biofer were more "homogeneous" in size than the products of recycled phosphorus. The strength of the granules from EkoBalans was almost as good as for the market product. The phosphorus pellets from Outotec and EkoBalans also had good strength, while the commercial Biofer pellets were easily broken. The Outotec pellets had the greatest mass flow, partly because their high density. There was no major difference in mass flow between the commercial Axan and EkoBalans’ recycled phosphorus granules. The granules from EkoBalans had a lower bulk density than the reference fertilizer and relatively low phosphorus concentration, which meant a high dosage (mass, volume) to spread 22 kg P/ha. Some recommended dosages can thus be greater than the current spreaders can handle. Spreading EkoBalans’ granules and Outotec's pellets with an effective swath width of 24 meter should not be a problem, and even 36 meters should be possible. However, spreader tests in the field should also optimize the spreader so that acceptable spreading uniformity is achieved at the desired working width. Fertilizers with low density and/or low plant nutrient content can result in low spreading capacity. Light granules or pellets also increase wind sensitivity when spreading. In order to get a new product on the fertilizer market, it is important that current setting recommendations for the spreaders are available. Testing of the product should also be done continuously to ensure quality over time. A test bed with stationary, automated test equipment to determine physical properties as well as to develop P setting recommendations for spreaders would increase the possibilities of getting products on the market. Key words: Fertilizer, recycled phosphorus, granules, pellets, physical properties, spreading tests, spreading evenness Vid framtagning av nya typer av gödselmedel är det angeläget att dessa har kemiska och fysikaliska egenskaper som möjliggör god spridningsprecision med de maskintyper som finns på marknaden. Detta är en förutsättning för att produkterna ska kunna användas och vara attraktiva för jordbruket. I studien ingick två fosforprodukter framställda med olika fosforutvinningstekniker, nämligen granuler (EkoBalans) bestående av struvit utfälld ur slutavvattningsrejekt på reningsverk samt ammoniumsulfat och kaliumklorid respektive pelletter (Outotec) tillverkade av aska från förbränning av slam. Dessa produkter jämfördes med marknads­produkterna Axan (granuler) respektive Biofer (pelletter). Inledningsvis bestämdes de fysikaliska egenskaperna hos framtagna fosforprodukter och marknadsprodukterna avseende kornstorlek, hållfasthet, flödesegenskaper, skrym­densitet samt dimensioner (pelletter). Även enklare fältteknik för bestämning av korn­storlek och hållfasthet användes inför spridningstesterna. Därefter utfördes spridartester utomhus i fält för att kontrollera spridbarheten med den i lantbruket vanligaste typen av spridare, centrifugalspridare. För spridningstesterna användes en testutrustning avsedd för fälttest av gödselspridare. Backar placerades ut tvärs kördraget för att samla upp gödseln över hela kastvidden vid en överfart med spridaren. Innehållet i backarna mättes och s.k. spridningsbilder togs fram och sprid­nings­jämnheten beräknades vid olika avstånd mellan kördragen. Den generella bedömningen var att de testade produkterna är spridningsbara med dagens centrifugalspridare. Vid framställning av produkter från återvunnen fosfor är granuler att föredra framför pelletter, främst på grund av att granulerna har högre massflöde vilket minskar risken för valvbildning och stopp i utmatningen. Marknadsprodukterna Axan och Biofer var ”homogenare” i storlek än produkterna av återvunnen fosfor. Hållfastheten hos granulerna från EkoBalans var nästan lika god som för marknadsprodukten. Fosfor-pelletterna från Outotec och EkoBalans hade god hållfasthet, medan Biofer-pelletterna gick lätt sönder. Av de pelleterade produkterna hade Outotec störst massflöde, delvis på grund av hög volymvikt. För granulerna var det ingen större skillnad i massflöde mellan marknadsprodukten och EkoBalans produkt bestående av återvunnen fosfor. Granulerna från EkoBalans hade lägre volymvikt än referensgödseln och relativt låg fosforkoncentration, vilket innebar hög giva (massa, volym) för att sprida en fosformängd av 22 kg/ha. Den rekommenderade doseringen (giva kg per ha) i fält kan därmed bli högre än vad dagens spridare klarar av. Spridning av EkoBalans granuler och Outotecs pelletter med arbetsbredder upp till 24 meter ska gå bra, men även arbetsbredder upp till 36 meter bör fungera. Dock krävs vidare spridartester i fält för att optimera spridaren så att acceptabel spridningsjämnhet uppnås vid önskad arbetsbredd. Gödsel med låg volymvikt och/eller litet växtnärings­innehåll kan resultera i låg spridningskapacitet. Låg volymvikt, lätta granuler eller pelletter, ökar också vindkänsligheten vid spridning. För att få ut en ny produkt på gödselmarknaden är det viktigt att aktuella inställnings­rekommendationer för spridarna finns tillgängliga. Test av produkten bör också göras kontinuerligt för att säkerställa kvaliteten över tiden. En testbädd med stationär och automatiserad testutrustning för att bestämma fysikaliska egenskaper såväl som att ta fram inställningsrekommendationer för spridare skulle öka möjligheterna att få ut produkter på marknaden.

The Swedish project P-to-Product focused on developing and adapting methods to promote recirculation of phosphorus (P) products extracted from sewage and sewage sludge. The project consisted of three work packages: 1) market introduction, 2) environmental impacts and 3) agricultural requirements. In wp 1 opportunities and barriers were identified and policy recommendations developed. This was done through interviews, surveys and workshops with stakeholders from sewage utilities, innovation companies, the fertilizer industry, the federation of Swedish farmers and national authorities. In wp 2 a simplified Life Cycle Assessment (LCA) was developed focused on nutrient recycling, global warming potential and energy use. In addition to this a chemical checkpoint was formulated with chemical analysis of a wide range of pollutants. For the development of methods in wp 2, granulated or pelleted nutrient products from the companies EkoBalans (a struvite based product with nitrogen and potassium added) and Outotec (a P-product with origin from incinerated sewage sludge) were used as case products. These products were also used in wp 3 where physical properties were evaluated and spreading tests were executed using existing machinery. The project provided a useful set of methods which soon will be complemented with methods to assess plant nutrient efficiency.

These instructions for manure sampling were formulated within the project Manure Standards (Advanced manure Standards for sustainable nutrient management and reduced emissions, Interreg Project No #R057) with the aim of harmonising sampling methods used within the Baltic Sea Region. The instructions are based on output from a previous project, Baltic Manure (Sindhöj et al., 2013), literature from within and outside the EU and feedback from tests of a first version on around 100 farms representing all nine countries bordering the Baltic Sea. These instructions have been circulated to project partners (see list in Appendix 2) and associate partners, including universities, research organisations, advisory services and other stakeholders in the Manure Standards project. A central factor during the work was to assess the impact on the analysis results of sampling factors such as number of samples (or subsamples), sampling depth, handling of samples, time period between sampling and analysis etc. Note that some countries, or even food companies, may have more rigid regulations on how sampling should be carried out (e.g. number of subsamples needed). In such cases, those special instructions should of course be followed in the first instance.

Samples of three different concrete qualities were prepared and hardened, before exposure in cattle slurry without sulphuric acid (A) and with sulphuric acid added until pH

Käesolev sõnnikuproovide võtmise juhend on koostatud projekti „Sõnnikustandardite arendamine parendamaks jätkusuutlikku toitainete kasutamist ja vähendamaks saasteainete emissioone“ (Interreg projekt Nr #R057) raames, eesmärgiga ühtlustada proovide võtmise metoodikaid Baltimere regioonis. Juhend tugineb projekti „Läänemeremaade foorum sõnniku jätkusuutliku käitlemise uuenduslikest tehnoloogiatest” (Sindhöj et al., 2013) tulemustele, sõnniku käitlemist käsitlevatele kirjandusallikate andmetele Euroopas ja väljaspool Euroopat ning samuti testfarmidest (ca 100) saadud tagasisidele. Testfarmid hõlmasid kõiki üheksat Balti mere riiki. Juhend on kättesaadav kõigile projekti s.h assotsieerunud partneritele (vt. Lisa 2), mille hulka kuuluvad nii ülikoolid, teadusinstituudid, konsulenditeenuseid pakkuvad ettevõtted ja teised projektiga seotud huvirühmad. Projekti keskseks eesmärgiks oli hinnata, kuidas mõjutavad erinevad tegurid, nt. proovide või osaproovide arv, proovi võtmise sügavus, proovi käitlemine, aeg proovi võtmisest analüüsini jne, analüüsi tulemust. NB! Mõnedes riikides või laboratooriumides võivad proovide võtmiseks ja käitlemiseks olla rangemad (spetsiifilisemad) eeskirjad (nt. vajalik osaproovide arv vms). Sellisel juhul tuleb esmalt järgida vastavaid (piirkondlikke) instruktsioone.

The study concerns acidification at the beginning of storage to reduce ammonia emissions during storage. The aim of the study was to evaluate the reduction of ammonia emissions by the acidification of cattle slurry, digested and non-digested, in storage under summer conditions. Cattle slurry (CS) and digested cattle slurry (DCS) were taken from a dairy farm with a digester plant. The sulphuric acid required for acidification to pH 5.5 was determined by titration before the pilot-scale experiment began. In the pilot-scale experiment, each slurry type was divided into two containers. One batch was acidified to pH

Kunskap om effektiva, funktionella och ekonomiska åtgärder krävs för att säkerställa små utsläpp av växthusgaser från lager med både orötad och rötad gödsel. I detta treåriga projekt har olika tänkbara åtgärder i flytgödsellager studerats genom mätning av växthusgaserna metan och lustgas under sommarförhållanden. Åtgärder som förlängd utrötningstid och surgörning av gödsel med svavelsyra, har utvärderats i RISE pilotskaleanläggning för lagring av flytgödsel. Åtgärder för att minska lustgasemissioner bildat i svämtäcke på gödselyta i ett fullskalelager har studerats på gårdsnivå. Kompletterande teoretiska beräkningar har utförts för att bedöma effekten av att täcka flytgödsellager samt laboratoriestudier av temperaturens påverkan på metangas-emissionerna. Grundläggande är att temperaturen har stor betydelse, vilket visades i laboratorieskalan. Vid ökad temperatur ökade metanproduktionen exponentiellt för rötad gödsel medan för orötad gödsel var ökningen betydligt mindre. De teoretiska värmebalansberäkningarna för lager med gödsel visade att beskuggning av gödselytan eller täckning av lager med vitt tak bör kunna reducera denna uppvärmning kraftigt på våren eftersom värmeinstrålningen från solljus till gödsellager kan förklarade största delen av gödselns uppvärmning. Studierna under första och sista året visade att metanemissionerna var signifikant större från gödseln när den var rötad än om den var orötad. Sammanlagda förlusterna av metan var 2,5 respektive fyra gånger så höga från den rötade gödseln under sommarlagringarna (ca fyra månader). Det betyder att det är speciellt viktigt att sätta in åtgärder vid lagring av rötad gödsel för att begränsa utsläppen av metan och därmed minska klimatpåverkan. En åtgärd för att få lägre metanemissioner från den rötade gödseln är att förlänga utrötningstiden, dvs. den hydrauliska uppehållstiden i rötkammaren. Studierna år 1 visar att vid en fördubblad uppehållstid, 48 dagar istället för 24 dagar, minskade metanemissionerna från lagret med 30 procent. På gårdar med rötningsanläggningar är ett gastätt tak med uppsamling av biogasen också en bra åtgärd för att effektivisera anläggningen och förhindra utsläpp av klimatgaser från lagret. Surgörning av flytgödsel med svavelsyra praktiseras främst i Danmark för att minska ammoniakavgången från flytgödsel, i stall, lager och vid spridning. Resultaten visar att det är en mycket effektiv metod för att minimera metangasemissionerna från lager med en reduktion med mer än 90 procent både för orötad och för rötad gödsel. Speciellt för gödselslag där det inte bildas naturligt svämtäcke kan surgörning vara intressant för att minska både ammoniak- och metanemissioner. Åtgärder som surgörning av svämtäcket för att minska lustgasemissioner visade sig inte behövas eftersom lustgasemissionerna var relativt låga, trots att svämtäcket var bortåt en halv meter tjockt. Den finhackade halmen som användes som strö, bildade ett slätt och tätt svämtäcke på gödselytan vilket troligen hämmande lustgasbildningen, till följd av att luften inte kunde penetrera skiktet. Så finhackningen av halmströ kan eventuellt vara i sig en tänkbar åtgärd, vilket också kan minska ströåtgången. Metanproduktionen från en rötkammare är ofta svår att mäta, och beräknas därför ofta indirekt utifrån producerad elproduktion. Ett exempel på nyckeltal för att visa klimateffektiviteten hos anläggningen visas där metanemissionerna från lager under sommaren var 10,2 % av producerad mängd metan från rötkammare vid enstegsrötning under 24 dagar respektive 5,5 % vid tvåstegsrötning under 48 dagar. På årsbasis blir procenttalen betydligt lägre eftersom emissionerna är låga under vintern. Ensuring low emissions of greenhouse gases from both undigested and digested animal slurry in storage requires a knowledge of effective, functional and economic measures. This three-year project has studied various potential measures for use in slurry storage. The greenhouse gases methane and nitrous oxide have been measured under summer conditions. Measures such as extended digestion time and acidification of slurry with sulfuric acid have been evaluated in a RISE pilot-scale plant for slurry storage. Measures to reduce nitrous oxide emissions formed in floating crust in a full-scale storage have been studied at farm level. Complementary theoretical calculations have been carried out to assess the effect of covering slurry stores. The impact of temperature on methane emissions has been studied in the laboratory. The fundamental point demonstrated on the laboratory scale is that the temperature is highly significant. As the temperature rose, methane production increased exponentially for digested slurry. For undigested slurry, the increase was considerably less. Most of the heat gained by the slurry can be attributed to solar radiation. Theoretical thermal balance calculations for slurry in storage indicated that it should be possible to reduce this heating significantly in spring by shading the slurry surface or provide the storage with a white roof. The studies in years 1 and 3 showed that methane emissions were significantly greater from digested than from undigested slurry. The total loss of methane from digested slurry was 2.5 and four times higher, respectively, during summer storage (approx. four months). It is therefore particularly important to implement measures to limit methane emissions from digested slurry in storage, thereby reducing the impact on the climate. One way to achieve lower methane emissions from digested slurry is to extend the duration of digestion, i.e. the hydraulic retention time in the digester. The studies in year 1 showed that doubling the retention time from 24 to 48 days reduced methane emissions from storage by 30 percent. At farms with digestion plants, a gas-tight roof with biogas collection is also an effective way to make the plant more efficient and prevent emissions of greenhouse gases from storage. Acidification of slurry with sulfuric acid is practiced in Denmark, to reduce ammonia emissions from slurry in housing, in storage and during spreading. The results show that it is also a very effective method for minimizing methane emissions from storage, with a reduction of more than 90 percent for both undigested and digested slurry. Acidification may be of interest as a way of reducing emissions of both ammonia and methane, particularly for types of slurry that do not naturally form a floating crust. Measures such as acidification of the floating crust to reduce nitrous oxide emissions did not prove to have effect because nitrous oxide emissions were relatively low, despite the floating crust being nearly half a metre thick. The chopped straw used for litter formed a smooth and dense floating crust on the surface of the slurry, and probably inhibited nitrous oxide formation because air was unable to penetrate the layer. Chopped straw litter in itself could therefore be a potential measure. This might also reduce straw consumption. Methane production from a digester is often difficult to measure and is therefore often calculated indirectly from the electricity produced. An example of key indicator for the climatic efficiency of the plant is given. For storage in summer, 10.2% of the methane produced was emitted during one-stage digestion over 24 days, and 5.5% during two-stage digestion over 48 days. The annual percentages are considerably lower because of low emissions in winter.

Nötflytgödsel tas tillvara på bästa sätt i vallodling om gödslingsstrategin är anpassad efter grödans näringsbehov, är ekonomisk och miljövänlig samt ger stor skörd och ett bra kväveutbyte. Men det är inte helt lätt att uppnå allt detta samtidigt. Så kan tjugo års forskning vid JTI – Institutet för jordbruks- och miljöteknik sammanfattas. Svenska studier har visat att ammoniakförlusten oftast är större vid spridning efter första skörden jämfört med spridning på våren. Det kan i första hand förklaras med lägre luft- och marktemperatur på våren, men beror också på att man sprider i en gröda på våren och på stubben efter första skörden. Grödans bladverk på våren dämpar ammoniakförlusten från flytgödseln. Det finns därför störst behov av teknik som minimerar ammoniakförlusten vid spridning på sommaren. Ammoniakförluster minskar gödselns värde samt orsakar övergödande och försurande utsläpp.

In this literature review, measures of reducing the ammonia (NH3) emissions from pig production are described, with focus on systems that can be used under Swedish conditions. The entire production chain with feed, housing, manure storage and application on the field is described and taken into consideration. However, in order to limit the study, the production of crops for feed is not included. As compared to many other countries, emissions of NH3 in Swedish pig production are already low, due to low protein levels in the feed, housing systems with a small excretory area, and storage of slurry outside the building. Lowering the crude protein level from 14.5 % to 12.5 % would reduce NH3 emission by 20 % from the pig house. Including fiber in the feed, leads to a shift from nitrogen in the urine towards more nitrogen in the faeces. In combination with removing the manure daily from the pig house, this might give opportunities for reducing NH3 emissions. A reduction in NH3 emission of up to 50 % might be possible. However, using fiber leads to higher methane (CH4) emissions (from animal and housing), and therefore this should be combined with biogas production. More research is needed in this field. Adding acids or salts to the feed could reduce NH3 emission by up to 40 %, while also improving feed conversion efficiency. Of course, good practice when preparing the feed must be followed. By applying multi-phase feeding and feeding according to the sex of the animals, NH3 emissions could be reduced by 5-15 %. By reducing feed spillage, offering a good environment for the pigs and maintaining good pig health, nitrogen losses could also be reduced with about 5 – 15 %. The importance of having clean pens is also discussed in this literature survey. Swedish housing systems, having a relatively high percentage of solid flooring (with some bedding) and a small excretory area in the pen, provides an opportunity for reducing NH3 emissions from the housing system. However, one prerequisite for this is that the pigs keep the pens clean, and therefore the room temperature should not be too high. This means that during hot periods, the air has to be conditioned before entering the pig house, e.g., by taking in the air via channels under the building. Removing manure daily by means of scrapers (reduction up to 40 %) and cooling the manure under the slats (reduction up to 50 %) are measures that are already implemented in Swedish pig production. The effect of air temperature, air flow and ventilation system are also discussed. Cleaning the exhaust air using bio-filters (up to 65 % reduction), bio-scrubbers (up to 70 % reduction) and chemical scrubbers (up to 96 % reduction) is also an option. By only purifying the exhaust air from the manure channels, the costs for this method can be reduced substantially. The emissions of CH4 and nitrous oxide (N2O) from the housing system are also discussed. Removal of the manure under the slats appears to reduce CH4 emission from the building. The use of deep-litter bedding may in many cases result in high N2O emissions. More research is needed in this field. Treating the manure with sulphuric acid, in combination with aeration and re-circulation in the pig house, can reduce NH3 emissions by up to 70 %. Pumping slurry between different compartments in a pig house is not allowed according to the Swedish Welfare Legislation. Therefore it is not certain that the acidification of slurry, inside the pig house, can be applied in Sweden. Anaerobic treatment of biogas production, as another treatment of manure, may not reduce NH3 emissions when storing and spreading the manure, but it results in increasing the nitrogen availability for the crops. In that way nitrogen losses can be reduced since less nitrogen has to be spread per hectare. Besides, biogas production reduces odour problems as well as emissions of green house gas (GHG) by the production of energy and lower CH4 emissions. Aerobic treatment of manure, can reduce the emissions of NH3 and GHG. However, poorly controlled aeration processes can have the opposite effect. Storage of slurry in a tank having a cover lid has been pointed out in many investigations, to be the easiest and most effective way of reducing NH3 and CH4 emissions. The straw used for fattening pigs is mainly consumed by the pigs, and it is rare that a naturally stable crust will be developed on the slurry. However, within piglet production a crust on the slurry tank is often found. This crust can cause problems when the slurry tank is covered. Technical solutions have to be developed to solve this problem. On pig farms, the main crops are cereals, and the slurry is mainly applied either in the spring during tillage work, or band spread in the early summer on growing cereals. Incorporation of the slurry, e.g., by harrowing in the spring, effectively reduces the NH3 losses if it takes place as soon as possible after spreading, preferably directly or at least within 4 hours after spreading. Another possibility is to band spread the slurry onto the growing cereals because the canopy provides a microclimate which reduces the NH3 losses, as compared to spreading on a bare field. Late application during the vegetation period or spreading before the autumn sowing, often results in lower nitrogen utilization by the plants, and thereby higher risks of nitrogen leakage. Due to interactions between different sources on a farm, reduction in NH3 emission from the individual sections of the livestock production system cannot be simply added to give the net reduction in emission from the total system. Thus a whole farm system approach is needed for devising control strategies for reducing NH3 emission. Four scenarios were evaluated in this report. Scenario 1 consists of: Reduction of the crude protein in the feed from 14.5 % to 12.5 %, relatively simple technique inside the pig house to reduce NH3 emission, covering the slurry tank and new technique when spreading manure. Scenario 2 consists of: Using biproducts from industry (16.5 % crude protein instead of 14.5 %) and cleaning of exhausting air, covering the slurry tank and new technique when spreading manure. Scenario 3 comprises conditions similar to those of Scenario 1, including high dietary feed fiber content in combination with biogas production. Scenario 4 comprises conditions similar to those of Scenario 2, including high dietary feed fiber content and in combination with biogas production. Preliminary calculations indicate that the scenarios may reduce emissions by 47-68 %. It should be pointed out that the calculations are still very uncertain. The calculations show that Scenario 3 appears to be the most effective way of reducing NH3 emissions. So the combination of using low protein feed with high fiber content together with the production of biogas appears to be a promising method for future development. Even Scenario 1, which used only simple techniques, has a significant result: lowering the protein content affects the entire chain from feed to the field. From the literature review, it can be concluded that one should consider whole farm systems when trying to reduce NH3 emissions. Having a roof on the manure storage, using band spreading together with incorporation, e.g. harrowing, within a few hours after spreading, are the most important and easiest ways of reducing NH3losses. When discussing the method of animal keeping, feeding and housing, a low protein level in the feed has a positive effect along the entire production chain, and appears to be the most effective means of reducing NH3 emissions. Using more fiber or acids/salts in the feed will reduce the NH3 emission even more. When biproducts from industry are used in the pig feed, cleaning the exhausting air from the manure channel may be an option. More research is needed before recommendations can be given.

The increased use of bio-materials for energy purposes is generating large amounts of ash. In most cases, e.g. during incineration of straw and grain, bottom ash contains small amounts of heavy metals, but significant amounts of the plant nutrients phosphorus (P) and potassium (K). Bottom ash also contains some micronutrients (e.g. copper and zinc) that are good for plants in small doses, together with generally small amounts of undesirable heavy metals, including cadmium. Biogas plants are becoming increasingly common in Sweden. They produce considerable amounts of digestate, a liquid fertiliser with a high content of nitrogen (N) comparable with that of pig slurry but lower contents of P and K. High quality biogas digestate may now be applied to arable land. This study investigated techniques and systems for blending and spreading liquid digestate with ash admixture. The physical and alkaline properties and solubility in water of some ash types were therefore studied at laboratory scale, as were the buffering properties of some digestates. The influence of ash admixture on digestate pH and ammonia emissions was also studied. At pilot scale, the properties of different ash/digestate mixtures were studied and a cell wheel for liquid manure was tested for adding the ash. Three types of ash (from oats, straw and wood pellets) and two types of digestate were studied. The ash produced so much dust that dust reduction measures and breathing masks proved necessary during handling. It also contained so much abrasive material that the risk of wear to pumps, pipes and other parts of the spreading equipment was rated high. It is therefore best if the ash can be added as late as possible to equipment for spreading on arable land, and also it can be prevented from passing through pumps and other moving parts. Only a minor proportion of the oat ash and straw ash was soluble in water. All three types of ash were alkaline and therefore increased the pH when mixed with water. However, the digestate had a high buffering capacity, so the overall effect on pH when moderate amounts of ash were included was slight. When oat ash was mixed into digestate, equilibrium concentrations of ammonia did not increase. There is thus no risk of increased ammonia emissions as long as the mixture does not contain more than 5% ash. In fact, ammonia concentrations were lower when ash was added, possibly because of ammonia binding to some metal ions. In practice, the SNFS 1994:2 limit values for P and heavy metals mean that the test ash-digestate mixtures with 1% by weight of ash can be applied to the same field at most twice in a three-year period. Mixtures with 3% by weight of ash can be spread at most every third year and mixtures with 5% by weight of ash at most every fifth year. Batch admixture of ash into liquid digestate is unsuitable, because the majority of the ash settles and forms sediment in the bottom of the tank, despite efficient stirring. For continuous dosage of finely pulverised ash into digestate, a cell wheel made for dosage of liquid manure can be used. However, for dosage into a flow under pressure a sluice is necessary to prevent digestate being pressed up into the ash container. Admixture of ash into solid digestate is another possible alternative, e.g. during movement of the solid fraction from a digestate separator to a store.