Ammonium nitrate and calcium ammonium nitrate are the most commonly used straight nitrogen fertilisers in Europe, accounting for 43% of the total nitrogen used for fertilisers. They are both produced in a similar way; carbonate can be added as a last step to produce calcium ammonium nitrate. The environmental impact, fossil energy input and land use from using gasified biomass (cereal straw and short rotation willow (Salix) coppice) as feedstock in ammonium nitrate production were studied in a cradle-to-gate evaluation using life cycle assessment methodology. The global warming potential in the biomass systems was only 22-30% of the impact from conventional production using natural gas. The eutrophication potential was higher for the biomass systems due to nutrient leaching during cultivation, while the acidification was about the same in all systems. The primary fossil energy use was calculated to be 1.45 and 1.37 MJ/kg nitrogen for Salix and straw, respectively, compared to 35.14 MJ for natural gas. The biomass production was assumed to be self-supporting with nutrients by returning part of the ammonium nitrate produced together with the ash from the gasification. For the production of nitrogen from Salix, it was calculated that 3914 kg of nitrogen can be produced every year from 1 ha, after that 1.6% of the produced nitrogen has been returned to the Salix production. From wheat straw, 1615 kg of nitrogen can be produced annually from 1 ha, after that 0.6% of the nitrogen has been returned. © 2008 Elsevier Ltd. All rights reserved.

The effects of making a 1000 ha organic farm self-sufficient in renewable fuel were studied. Biomass grown on-farm can be transported to large fuel production facilities and the fuel transported back to the farm. Two fuels, Fischer-Tropsch diesel (FTD) and dimethyl ether (DME), produced from either straw or short-rotation willow coppice (Salix), were studied. The environmental impact, land use and energy balance were calculated using life-cycle methodology. It was calculated that the straw-based systems had only 32-39% of the impact on global warming (kg [CO2-eq]) compared to the Salix-based systems. For acidification and eutrophication, the differences between the systems were less significant. The energy balances were 8.9 and 9.6 for FTD and 10.1 and 10.0 for DME, from straw and Salix, respectively. To become self-sufficient in FTD, 108 ha has to be set aside for Salix production or 261 ha of straw collected from the existing crop rotation. For DME the corresponding figures are 38 and 70 ha. The many by-products in the FTD scenarios explain the large difference between fuels. Comparing FTD and DME, the differences in environmental impact were small. Considering this, FTD is a more likely alternative since DME requires a pressurised infrastructure system and engine modifications. © 2007 IAgrE.

This study analysed a future hypothetical organic farm self-sufficient in renewable tractor fuel. Biomass from the farm was assumed to be transported to a central fuel production plant and the fuel returned to the farm, where it was utilised in fuel cell powered tractors. The land use, energy balance and environmental impact of five different scenarios were studied. In the first two scenarios, straw was used as raw material for production of hydrogen or methanol via thermochemical gasification. In the third and fourth scenarios, short rotation forest (Salix) was used as raw material for the same fuels. In the fifth scenario, ley was used as raw material for hydrogen fuel via biogas production. The straw scenarios had the lowest impact in all studied environmental impact categories since the Salix scenarios had higher soil emissions and the ley scenario had comparatively large emissions from the fuel production. The energy balance was also favourable for straw, 16.3 and 19.5 for hydrogen and methanol respectively, compared to Salix 14.2 and 15.6. For ley to hydrogen the energy balance was only 6.1 due to low efficiency in the fuel production. In the Salix scenarios, 1.6% and 2.0% of the land was set aside for raw material production in the hydrogen and methanol scenarios respectively. In the straw scenarios no land needed to be reserved, but straw was collected on 4.3% and 5.3% of the area for hydrogen and methanol respectively. To produce hydrogen from ley, 4% of the land was harvested. The study showed that the difference in environmental performance lay in choice of raw material rather than choice of fuel. Hydrogen is a gas with low volumetric energy density, which requires an adapted infrastructure and tractors equipped with gas tanks. This leads to the conclusion that methanol probably will be the preferred choice if a fuel cell powered farm would be put into practice in the future. © 2009 Elsevier Ltd. All rights reserved.

Currently Swedish healthcare uses large amounts of disposable products, many of which are made from plastic. For example, Region Uppsala annually uses 3,2 million disposable plastic aprons. Currently these aprons are manufactured from fossil based polyethene plastic. This causes emissions of 270 tonnes of carbon dioxide equivalents over their life cycle from extraction of raw material to end of life through incineration. If substituting the fossil polyethene with plastic manufactured from renewable material, there is a potential to reduce the climate impact from disposable plastic aprons. Current study has compared disposable plastic aprons made from fossil polyethene with aprons made from renewable raw materials. Two renewable plastics were evaluated, disposable apron made of polyethene manufactured from bioethanol from Brazilian sugar cane and disposable aprons made of the renewable plastic polylactide (PLA) origination from sugar cane grown in Thailand. The result is that using biopolyethene reduces climate impact with 60 % and PLA aprons with 40 % compared to fossil polyethene. PLA has a component that currently is of fossil origin. If in the future this component is substituted with a renewable component there is a potential to reduce the PLA climate impact with as much as 20 % compared to current reduction in comparison to fossil polyethene.

Large amounts of domestic raw material will be needed for future biofuel production in Sweden. Various grasses and straw are interesting alternatives for ethanol production. In the ethanol production, hydrolysis lignin residual is produced, which does not yet have a well-formulated end-use.

HTL is a liquefaction process that can be used to produce bio-oil. In this project we have studied whether hydrolysis lignin residue from ethanol production could be used as raw material in the HTL process. The produced bio-oil can be upgraded together with fossil oil in a conventional refinery and converted into biofuel components.

In this system study, biofuel production based on straw and ley grass as raw material have been studied in terms of climate impact, mass flows and economy. Four scenarios were investigated, two with straw as raw material and two with ley grass as raw materi-al. In all scenarios, the raw material was assumed to be used for ethanol production. In two scenarios, lignin residue from ethanol production was sent for incineration. In the other two scenarios, the lignin residue is further processed bio-oil via the HTL process.

In all scenarios the climate impact was reduced compared to fossil fuels. Ethanol gives a reduction of 72 – 92% and biofuels from bio-oil a reduction of 64 – 81% compared to the fossil reference. Considering soil carbon however has a large effect on the climate impact; removing straw is a loss of carbon while cultivation of ley grass add carbon to the soil.

The cost of producing ethanol was calculated to be between SEK 3 200 – 4 800 per metric ton ethanol. The fuels produced via HTL were estimated to have a production cost between SEK 11 600 – 15 100 per metric ton of fuel. Thus, biofuels from hydrolysis lignin were calculated to be much more expensive than ethanol. This is mainly due to the costs associated with the upgrade of bio-oil. However, results should be carefully interpreted as there is a lack of input data and major uncertainties in the estimations.

Life cycle assessment (LCA) and life cycle costing (LCC) are well-established methods used for many years in many countries for system analysis of waste management. According to standard LCA procedure the assessment should include improvement analysis, in many cases this is performed by simple sensitivity analyses. An obstacle to perform more thorough sensitivity analyses is that it is hard to distinguish input data important to the results, i.e. key parameters. This paper further elaborates sensitivity analyses performed in an environmental system analysis for a hypothetical Swedish municipality. In this paper, the methodto identify and test input data that can be categorised as potential key parameters is described. The method and the results from computer simulations of the identified parameters are presented, and some conclusions are drawn regarding the robustness of the results for environmental impact from municipal solid waste management. The major conclusion is that the results are robust. Changes in results, when changing the preconditions, are often small and the changes observed do not lead to new conclusions; i.e., a change of ranking order between treatment options. © 2010 Elsevier B.V. All rights reserved.

A simulation model, ORWARE (ORganic WAste REsearch) is described. The model is mainly used as a tool for researchers in environmental systems analysis of waste management. It is a computer-based model for calculation of substance flows, environmental impacts, and costs of waste management. The model covers, despite the name, both organic and inorganic fractions in municipal waste. The model consists of a number of separate submodels, which describes a process in a real waste management system. The submodels may be combined to design a complete waste management system. Based on principles from life cycle assessment the model also comprises compensatory processes for conventional production of e.g. electricity, district heating and fertiliser. The compensatory system is included in order to fulfil the functional units, i.e. benefits from the waste management that are kept constant in the evaluation of different scenarios. ORWARE generates data on emissions, which are aggregated into different environmental impact categories, e.g. the greenhouse effect, acidification and eutrophication. Throughout the model all physical flows are described by the same variable vector, consisting of up to 50 substances. The extensive vector facilitates a thorough analysis of the results, but involves some difficulties in acquiring relevant data. Scientists have used ORWARE for 8 years in different case studies for model testing and practical application in the society. The aims have e.g. been to evaluate waste management plans and to optimise energy recovery from waste. © 2002 Elsevier Science B.V. All rights reserved.

The aim of this work was to evaluate systems making organic farms self-sufficient in farm-produced bio-based fuels. The energy balance and environmental load for systems based on rape methyl ester (RME), ethanol and biogas were evaluated using a life cycle perspective. Complete LCAs were not performed. Important constraints when implementing the systems in practice were also identified. The RME scenario showed favourable energy balance and produced valuable by-products but was less positive in some other aspects. The use of land was high and thereby also the emissions associated with cultivation. Emissions, with the exception of CO2, during utilisation of the fuel were high compared to those of the other fuels in the study. The technology for production and use of RME is well known and easy to implement at farm scale. The production of ethanol was energy consuming and the by-products were relatively low value. However, the area needed for cultivation of raw material was low compared to the RME scenario. The production and utilisation of ignition improver and denaturants were associated with considerable emissions. Suitable ethanol production technology is available but is more optimal for large scale systems. The biogas scenario had a low relative need for arable land, which also resulted in smaller soil emissions to air and water. Another advantage was the potential to recycle plant nutrients. On the other hand, the potential emissions of methane from storage of digestate, upgrading of biogas and methane losses during utilisation of fuel produced a negative impact, mainly on global warming. Small scale technology for biogas cleaning and storage is not fully developed and extensive tractor modifications are necessary. The global warming effects of all three systems studied were reduced by 58-72% in comparison to a similar farming system based on diesel fuel. However, the fuel costs were higher for all scenarios studied compared to current diesel prices. In particular, the large costs for seasonal storage of gas meant that the biogas scenario described is currently not financially viable. © 2005 Elsevier Ltd. All rights reserved.

Grass-clover ley holds an importance role for a sustainable crop production and is mainly used as feed for ruminants. But ley also contains proteins, if extracted, suitable for monogastric animals such as pigs and poultry. If these proteins are extracted, the degree of self-sufficiency of proteins in Sweden can increase and better resource utilization is achieved. In this study we evaluated the utilization of fresh and ensiled grass-clover ley in a straw-based agricultural biorefinery for producing protein concentrate, ethanol, bio-oil and biogas.

Practical lab scale tests of extraction of high value components for food and feed applications from the liquid fraction after ley pressing were carried out. Pretreatments of the solid fraction prior to ethanol fermentation, bio-oil production using HTL (hydrothermal liquefaction) and biogas production were tested. The system for production and supply of the ley was described and the potential for increased ley production in Sweden was quantified. The environmental and economic efficiency of the proposed biorefinery system was evaluated using environmental systems analysis and technoeconomic assessment.

In terms of system profitability, a high protein yield in the extracted protein concentrate it is important. To achieve that, a thorough pre-treatment using mechanical biomass disintegration before fractioning is crucial. This may need to be done in several steps. Screw pressing is a common technique for fractionating ley into a liquid and solid fraction. Double pressing combined with enzymatic treatments or only water addition during the second pressing stage were found to increase the protein yield compared to single pressing. Second pressing had no effect on the amino acid profile of the protein concentrate.

After pressing fresh ley, heat coagulation or isoelectric precipitation can be used to precipitate protein concentrates in one- or two-step processes to produce protein fractions with different functional properties. Tests showed that it is possible to recover chlorophyll and carotenoids from the ley using supercritical carbon dioxide extraction. which is a suitable method for food applications as toxic organic solvents can be avoided. The ensiling process degrades the protein into smaller peptides or free amino acids which makes ensiled grass less suitable for protein recovery by heat coagulation or isoelectric precipitation. Fresh and ensiled timothy and meadow fescue showed a similar amino acid profile as soybeans.

The initial hypothesis that mechanical pressing may disintegrate the lignocellulosic structure of ley sufficiently to produce a sugar stream with a high concentration of sugar for further fermentation by enzymatic hydrolysis was not confirmed. The content of sugars released after the enzymatic hydrolysis was relatively low. The fibre fraction after the mechanical pressing can be suitable for ethanol production if an additional pretreatment method will be incorporated. Fermentation of pressed and steam-exploded ensiled mixed ley showed promising results. The bio-oils produced with the HTL-process were described of high quality, i.e., high carbon content and low ash content. Although, the obtained materials are not directly integrable in today's refineries, the ensiling did not seem to affect the material's potential for biofuel production. The methane potential tests that were carried out in the project of the liquid residual fraction after protein extraction and after the HTL process showed that both can be suitable for methane production, but they showed great behavior differences.

The results from the environmental system analysis showed that extraction of high-quality products from ley, straw and sawdust according to the studied system reduces climate impact (CO2 eq) when the use of ethanol, bio-oil and biogas replaces fossil fuels, protein concentrate replaces soy as feed and carbon dioxide replaces fossil carbon dioxide. At present, the climate impact from extracted protein concentrate is higher than for soybean meal. Grass source for protein extraction followed by ethanol and bio-oil production as an alternative to straw-based ethanol and bio-oil production did not seem to improve the profitability of the studied biorefinery system. Profitability may be improved if protein extraction is performed the whole all year and not seasonal. Higher prices of the extracted protein concentrate may also improve profitability.

The potential for increased grassland cultivation in Sweden for biorefining was estimated at approximately 3.4 million tonnes grass per year. This included incorporating grassland in the crop rotation in grain-dominated areas, intensification of existing grassland cultivation, utilization of fallow and abandoned arable land for grassland cultivation.

Based on the results and the experience acquired from this project, we suggest an extraction plant for grass-clover ley that operates for both fresh and ensiled grassland all year. The plant needs to be supplemented with more advanced technologies such as membrane filtration for the extraction of amino acids from the ensiled ley during the winter season. The protein extraction plants should be located near farms. The extraction plant is also suggested to be located together with a biogas plant to enable co-digesting residual fractions with manure. Thereby, enabling plant nutrients and minerals in digestate to be returned to arable land. Utilizing the solid fiber fraction for biofuel production with fermentation and HTL in large-scale processes remains promising.

The aim of the present work was to evaluate systems for making organic farms self-sufficient in bio-based fuels. The energy efficiency and environmental load for systems based on rape methyl ester (RME), ethanol and biogas produced by processing raw material from the farm in industrial-scale plants were evaluated using a life cycle perspective. Eventual constraints when implementing the systems in practice were also identified and the farmer's costs for the systems estimated. The RME scenario showed some good characteristics; the energy efficiency and potential effects on global warming were favourable, the technology well known and no engine modifications were necessary. However, the high price of the organically produced rapeseed made the fuel expensive. The ethanol scenario provided fuel at a comparatively low cost, but the energy efficiency was low and existing engines would have to be modified. The biogas scenario was not as economically advantageous, due to high costs for storage and transport of the biogas and the extensive tractor modifications needed. The calculations further showed that systems based on so-called exchange of fuels, i.e. when the farm produces raw material for one type of biofuel, but instead uses another type of biofuel more suitable for its own tractors, were an economically favourable way of supplying the organic farms with 'self-produced' bio-based fuels. The exchange scenario based on delivery of organic wheat to a large-scale plant and use of RME at the farm was somewhat more expensive than scenarios based on production of biogas raw material at the farm. However, the wheat/RME system has the advantage of being possible to put into practice immediately, since industrial-scale wheat ethanol plants are in operation and RME fuel is available on the market. © 2007 Elsevier Ltd. All rights reserved.

An analysis of the environmental effects and resource consumption by four systems for management of wastewater and organic household waste in a new city area have been performed, as follows: (1) conventional system complemented with advanced sludge treatment for phosphorus recovery, (2) blackwater system with urine diversion and food waste disposers, (3) blackwater system with food waste disposers and reverse osmosis, and (4) local wastewater treatment plant with nutrient recovery by using reverse osmosis. Substance-flow analysis and energy/exergy calculations were performed by using the software tool URWARE/ORWARE. Emissions were calculated and classified based on the impact categories global warming potential, acidification, and eutrophication, according to ISO14042 (2000). The analysis also included nutrient recovery (i.e., the potential to use nutrients as a fertilizer). Depending on which aspects are prioritized, different systems can be I considered to be the most advantageous.

This study assessed the environmental impacts of recycling the plant nutrients in anaerobically digested food waste as fertilizer in agriculture. This was compared with the impacts of using chemical fertilizer, where the food waste was incinerated, producing heat. The study site was a biogas plant in central Sweden and life cycle assessment methodology was used. The impacts studied were primary energy use, global warming potential (GWP), potential acidification, potential eutrophication, cadmium flow to farmland and use of phosphate rock. Use of digested food waste as fertilizer proved to have larger negative results than use of chemical fertilizer in all categories assessed except use of non-renewable phosphate rock. Sensitivity analyses showed that the scenarios were comparable in terms of primary energy use and better for GWP if some improvements in the anaerobic digestion system were made. However, acidification and eutrophication caused by digestate handling and the cadmium content of digestate should still be considered.

Biomass produced on farm land is a renewable fuel that can prove suitable for small-scale combined heat and power (CHP) plants in rural areas. However, it can still be questioned if biomass-based energy generation is a good environmental choice with regards to the impact on greenhouse gas emissions, and if there are negative consequences of using of agricultural land for other purposes than food production. In this study, a simplified life cycle assessment (LCA) was conducted over four scenarios for supply of the entire demand of power and heat of a rural village. Three of the scenarios are based on utilization of biomass in 100 kW (e) combined heat and power (CHP) systems and the fourth is based on fossil fuel in a large-scale plant. The biomass systems analyzed were based on 1) biogas production with ley as substrate and the biogas combusted in a microturbine, 2) gasification of willow chips and the product gas combusted in an IC-engine and 3) combustion of willow chips for a Stirling engine. The two first scenarios also require a straw boiler. The results show that the biomass-based scenarios reduce greenhouse gas emissions considerably compared to the scenario based on fossil fuel, but have higher acidifying emissions. Scenario 1 has by far the best performance with respect to global warming potential and the advantage of utilizing a byproduct and thus not occupying extra land. Scenario 2 and 3 require less primary energy and less fossil energy input than 1, but set-aside land for willow production must be available. The low electric efficiency of scenario 3 makes it an unsuitable option. © 2011 Elsevier Ltd.

The agricultural industry today consumes large amounts of fossil fuels. This study used consequential life cycle assessment (LCA) to analyse two potential energy self-sufficient systems for organic arable farms, based on agricultural residues. The analysis focused on energy balance, resource use and greenhouse gas (GHG) emissions. A scenario based on straw was found to require straw harvest from 25% of the farm area; 45% of the total energy produced from the straw was required for energy carrier production and GHG emissions were reduced by 9% compared with a fossil fuel-based reference scenario. In a scenario based on anaerobic digestion of ley, the corresponding figures were 13%, 24% and 35%. The final result was sensitive to assumptions regarding, e.g., soil carbon content and handling of by-products. © 2010 Elsevier Ltd.

There is a growing awareness of the climate impact of agricultural production, not least from cattle farms. Major sources of GHG emissions from milk production are enteric fermentation followed by fossil fuel use and manure/soil management systems. This study analyzes the potential to eliminate fossil fuel use from milk production farms in Sweden, by using residual farm resources of biomass to obtain self-sufficiency in fuel, heat and electricity. The change from a fossil-based energy system to a renewable system based on A) Biogas based on manure and straw and B) Biogas based on manure + RME were analyzed with consequential life cycle assessment (CLCA) methodology. Focus was energy use and GHG emissions and the functional unit was 1 kg of energy-corrected milk (ECM). The results show that organic milk producers can become self-sufficient in energy and reduce total GHG emissions from milk production by 46% in the Biogas system, or 32% in the Biogas + RME system compared to the Fossil system.

RISE har på uppdrag av Naturvårdsverket tagit fram klimatindikatorer för svensk konsumtion av livsmedel baserat på statistik för 2016 och 2018. Jordbruksverket publicerar årligen statistik på direktkonsumtion av livsmedel i Sverige och informationen om konsumerad mängd livsmedel i olika produktgrupper har använts tillsammans med klimatavtryck för livsmedel, vilka tagits från RISE Klimatdatabas för livsmedel v. 1.7, för att ta fram klimatpåverkan för svensk direktkonsumtion av livsmedel. Utifrån Jordbruksverkets indelning av livsmedel i produktgrupper i konsumtionsstatistiken har klimatindikatorer tagits fram för de åtta olika produktgrupperna i statistikunderlaget, plus tre för undergrupper inom köttproduktgruppen, samt en klimatindikator för total direktkonsumtion av alla livsmedel 2016 och 2018. Följande produktgrupper har klimatberäknats: 1. Bröd och spannmålsprodukter 2. Kött och köttråvaror, som även delats upp i a. Kött, färskt och fryst b. Charkuterivaror och konserver (inklusive innanmat) c. Frysta köttprodukter och fryst färdiglagad mat innehållande kött 3. Fisk, kräftdjur och blötdjur 4. Mjölk, grädde, ost, ägg och matfett 5. Köksväxter 6. Frukt och bär 7. Potatis, potatisprodukter, socker, sirap, kaffe, te, kakao 8. Andra livsmedel, malt- och läskedrycker, mineralvatten samt alkoholhaltiga drycker De olika produktgrupperna består i sin tur av varugrupper, där varje varugrupp angivits en konsumtionsvolym. RISE har med information från Jordbruksverket och statistik från SCB och Jordbruksverket brutit ner de aggregerade konsumtionsvolymerna för varje varugrupp till specifik konsumtion av de olika livsmedel som ingår i respektive varugrupp. På detta sätt har matchningen till representativa klimatavtryck i RISE Klimatdatabas för livsmedel möjliggjorts och således också beräkningen av klimatindikatorer för de olika produktgrupperna då klimatindikatorerna representerar summan av klimatpåverkan från varorna som konsumeras i respektive varugrupp. Enbart klimatpåverkan från primärproduktion och förädling fram till industrigrind (det vill säga då livsmedlet är färdigt för distribution till handeln) ingår i klimatavtrycken i RISE Klimatdatabas för livsmedel. Klimatpåverkan från förpackning ingår dock inte, inte heller klimatpåverkan från distribution, handel och konsument.

·   Om Sverige ska uppnå takdirektivets utsläppsmål för ammoniak till 2030, minska jordbrukets utsläpp av växthusgaser och samtidigt, enligt den nationella livsmedelsstrategin, öka vår självförsörjningsgrad genom ökad livsmedelsproduktion krävs snabb handling och en seriös åtgärdsplan för de kommande åren.

·   Surgörning är bevisat som en effektiv åtgärd för att minska utsläpp av ammoniak och metan från stallgödsel. Tekniken har främst använts i Danmark och mycket erfarenhet kan hämtas därifrån.

·   Surgörning skulle kunna implementeras i Sverige för att minska utsläpp av ammoniak och metan från stallgödselhanteringen och därmed minska miljöpåverkan från animalieproduktionen. 

·   I denna rapport redogörs för följande tekniker: surgörning i stall, surgörning innan lagring (tekniken ännu inte utvecklad) och surgörning innan spridning. Den sistnämnda kan ske antingen i lagringstanken strax innan spridning eller i fält vid själva spridningen men bägge varianter har liknande effekt på utsläppen.

·   För befintlig surgörningsteknik (surgörning i stall eller innan spridning) finns inga tekniska hinder för implementering, bara ekonomiska hinder. Surgörning blir en kostnad för lantbrukare eftersom värdet av det besparade kväve täcker inte kostnader. Det har funnits ett försök att etablera försäljning av surgörningsteknik hos en maskinstation i Skåne där erfarenhet om eventuella hinder till implementering av surgörningsteknik i Sverige kan hämtas.

·   Av befintlig surgörningsteknik skulle den som implementeras i stallet ge störst utsläppsminskning av både ammoniak och metan, men denna teknik kan kräva ombyggnad av befintliga stallar varvid tekniken förmodligen lämpar sig bättre vid nybyggnation. 

·   Surgörning innan lagring skulle vara lättare att implementera vid befintliga stallar i Sverige, men tekniken behöver utvecklas och valideras eftersom den inte finns kommersiellt tillgänglig i dagsläget.

·   Surgörning av flytgödsel innan/vid spridning skulle kunna implementeras på bred front i Sverige men det minskar bara utsläpp av ammoniak och inte metan. Om maskinstationer investerade i tekniken kunde även mindre gårdar utnyttja surgörning.

·   Surgörning av stallgödsel sparar kväve som annars i konventionell produktion ersätts med mineralkväve från inköpt handelsgödsel. Minskad användning av mineralkväve minskar utsläppen av växthusgaser ytterligare men denna utsläppsminskning ingår inte i beräkningarna som presenteras i denna rapport. 

·   Sparat kväve kan ha ännu större betydelse i ekologisk odling eftersom det är svårt att ersätta förlorat kväve med gödselmedel tillåtna i ekologisk produktion. Vid surgörning används dock svavelsyra som inte är tillåtet i ekologisk odling. 

·   Forskning krävs för att utvärdera tillämpning av surgörningsteknik under svenska förhållanden och för att utveckla tekniken för surgörning innan lagring som lättare kan anpassas till befintliga stallar. Det är viktig att forskningsresultaten kan användas som grund för att inkludera surgörningspåverkan i vår nationella klimat- och luftinventering. 

·   Främjandet av teknik som minskar utsläpp av ammoniak och metan från stallgödsel, som till exempel surgörning, bör vara en given del av en åtgärdsplan för Sverige att kunna uppnå takdirektivets utsläppsmål till år 2030 och vårt långsiktiga klimatmål om nettonollutsläpp av växthusgaser till år 2045 samtidigt som vi ökar vår självförsörjningsgrad av livsmedel. 

·   Politiska styrmedel är nödvändiga för att genomföra implementering av tillräckligt många åtgärder inom svenska jordbruket så att både miljömål och andra samhällsmål kan nås. Implementering av miljöteknik på bred front skulle utföra en samhällstjänst men då det ofta innebär en kostnadsökning för lantbrukarna så bör de få ersättning för merkostnader. Därför bör de politiska styrmedlen vara en blandning av ekonomiska incitament och strängare regelverk.

Recycling of plant nutrients in sewage products to arable land is considered to be a step towards a more sustainable society. Sewage sludge is the predominant sewage fertiliser product available today, but the use of sewage sludge in agriculture has been questioned as regards hazardous substances. In this respect, blackwater from separating systems seems to better fulfil agricultural requirements regarding fertiliser products. The objective of this paper was to analyse the environmental impact and resource use in a life cycle perspective for three systems, each including both wastewater handling and agricultural production. In the reference system, food waste disposers were installed in houses. Milled food waste and wastewater were treated in a wastewater treatment plant and the sewage sludge was used for producing a soil conditioner. In the sludge utilisation system, food waste from households was composted, wastewater was treated conventionally and sewage sludge was used in oat production. In the blackwater system, toilet water from low-flush toilets and milled organic waste were digested together and spread in growing oats. Data on the wastewater system were derived from simulations by the substance-flow model URWARE/ORWARE. The blackwater system required slightly more primary energy than the other two systems. In particular, construction of storage facilities contributed considerably to energy use. The emissions of greenhouse gases and SO2 were of the same magnitude for all three systems, while the eutrophying emissions were reduced significantly in the blackwater system. As regards NH3 and NOX, the emissions were highest for the blackwater system. High substitution of mineral fertiliser, optimal spreading technique and well-designed collection and storage facilities were important factors for the environmental outcome in the blackwater system. © 2005 Elsevier B.V. All rights reserved.