Gödselbaserad biogasproduktion har i flera sammanhang setts som en åtgärd för att minska växt­husgasutsläppen från gödselhanteringen. Det har varit ett av de drivande argumenten för flera styrmedel som syftat till ökad gödselbaserad biogasproduktion. Men bilden är inte entydig. I Sveriges växthusgasinventering skattas metanemissionerna från rötad flytgödsel vara något högre än från orötad flytgödsel.

I denna rapport har vi sammanställt emissionsfaktorer som kan användas på gårdsnivå för att skatta förväntade förändringar av växthusgasutsläpp från stallgödselhanteringen vid gårds­baserad biogasproduktion från stallgödsel. Emissionsfaktorer har sammanställts för metan, lustgas och ammoniak (ger indirekt lustgas), och de ska reflektera ett generellt snitt för svenska förhållanden. Utgångspunkten har varit metoden och upplägget i växthusgasinventeringen, men emissionsfaktorerna är anpassade för att användas inom Klimatklivet genom att uttryckas per ton stallgödsel eller per MWh biogas.

Emissionsfaktorer har sammanställts för stallgödsel som vanligtvis rötas i Sverige, både vad gäller djurslag och gödselslag. Den mesta gödseln som rötas är nöt- och grisflytgödsel, men det rötas även fasta gödselslag som exempelvis fjäderfägödsel och djupströgödsel från nöt­kreatur och suggor.

Eftersom emissionsfaktorerna ska kunna visa skattade förändringar i växthusgasutsläpp behövs det emissionsfaktorer dels för traditionell gödselhantering, dels för rötning av stallgödsel (inklu­sive lagring av flytande rötrest). Dessutom beskrivs emissioner från spridning av orötad och rötad stallgödsel. Emissionsfaktorerna uttrycks per ton stallgödsel respektive per ton stall­gödsel som rötats, och räknas därefter om till att uttryckas per MWh biogas.

Det finns mycket som talar för att vi har låga växthusgasutsläpp från den traditionella gödsel­hanteringen i Sverige. Snabb utgödsling av flytgödsel från stall samt kallt klimat under lagrings­­tiden gör att vi i en internationell jämförelse kan räkna med låga metanemissioner från den traditionella flytgödselhanteringen. Lustgasemissioner och växthusgasutsläpp från andra gödselslag är också generellt sett låga, men kunskapsunderlaget om dessa emissioner är sämre.

Men en konsekvens av att vi har så låga växthusgasutsläpp från den traditionella gödselhanter­ingen är att gödselbaserad biogasproduktion inte har så stor potential att minska växthusgasut­släppen ytterligare. De beräkningar som gjorts i denna rapport tyder på att växthusgasutsläppen från orötad flytgödsel, som är det dominerande gödselslaget som rötas, är en bråkdel av gödsel­krediten som ingick i Klimatklivets utsläpps­faktor för gödselbaserad biogas innan ansöknings­om­gången i september 2025. Värdet på gödselkrediten kom från normalvärdet (g CO2e per MJ biogas) för gödselbaserad biogas enligt EU:s förnybartdirektiv (REDII), och motsvarade de undsluppna emissionerna från traditionell gödselhantering.

Dessutom sker det växthusgasutsläpp från rötning av stallgödsel och lagring av rötrest. I flera fall är det inga eller mycket små skillnader i skattade växthusgasutsläpp (kg CO2e per ton stallgödsel) från gödselhantering­en mellan referens­­systemet (ingen rötning) och biogas­systemet. Det gäller till exempel för flytgödsel (nöt- och grisflyt) med täckning.

Växthusgas­utsläppen från djupströgödsel skattas minska (gäller samtliga djurslag), medan de skattas öka bland annat för fjäderfägödsel och fastgödsel från häst. Djupströgödsel samt fjäderfä- och hästgödsel utgör dock volymmässigt en begränsad andel av stallgödseln som rötas, och emissionsfaktorerna för dessa gödselslag är mer osäkra än för flytgödsel.

Så även om det skulle gå att producera gödselbaserad biogas utan några som helst emissioner från biogasanläggningen och rötresthanteringen skulle klimatvinsten i gödselhanteringen bara bli en bråkdel av gödselkrediten enligt REDII och av den utsläppsfaktor som användes i Klimatklivet innan ansökningsomgången i september 2025.

Det finns flera områden att arbeta med för att minska växthusgasutsläppen från biogas­system­et. Det handlar om god utrötningsgrad, hålla låg temperatur i rötresten som lagras och täck­ning av rötrestlager för att minska ammoniakemissionerna.

Det är främst metan som påverkar storleken på växthusgasutsläppen från hanteringen av stall­gödsel, såväl rötad som orötad. Emissionerna av kväve, som lustgas eller andra kväveformer, ger främst miljöpåverkan som övergödning och försurning. Lantbrukaren värderar såväl orötad som rötad stallgödsel främst för dess innehåll av växttillgängligt kväve. Därför är åtgärder för att minska kväveförluster viktiga, både för minskad miljöpåverkan och ökad beredskap via tillgång på värdefull stallgödsel.

Kunskapsunderlaget för att skatta emissionerna från svensk stallgödselhantering och rötning av stallgödsel är begränsat. Exempelvis bygger skattningarna av metanemissioner från flytgödsel och lagring av rötrest på ett fåtal studier i pilotskala. Det skulle behövas fler emissions­mätningar, gärna på biogasanläggningar och fullskaliga gödsellager, för att fånga upp de verkliga förhållandena och hur stora emissionerna kan vara i praktiken.

The biomass potential in Swedish agriculture needs to be used more effectively to produce food, feed and energy in the future and to meet Swedish sustainability goals by 2030. In the project, a biorefinery concept was designed, that consists of the three processes biogas, ley protein and bio-oil. The concept was evaluated with costs and mass balances regionally for Västra Götaland Region. Lab scale trials to produce bio-oil and biogas were also carried out. The results showed that the concept has potential to produce biofuel, protein feed and plant nutrition from agricultural residues and the cultivation of ley and create a high degree of self-sufficiency. However, a more in-depth techno-economic analysis is required as well as an analysis of possible obstacles and bottlenecks. 

The biomass potential in Swedish agriculture needs to be used more effectively to produce food, feed and energy in the future and to meet Swedish sustainability goals by 2030. In the project, a biorefinery concept was designed, that consists of the three processes biogas, ley protein and bio-oil. The concept was evaluated with costs and mass balances regionally for Västra Götaland Region. Lab scale trials to produce bio-oil and biogas were also carried out. The results showed that the concept has potential to produce biofuel, protein feed and plant nutrition from agricultural residues and the cultivation of ley and create a high degree of self-sufficiency. However, a more in-depth techno-economic analysis is required as well as an analysis of possible obstacles and bottlenecks. 

Precision seeding of winter oilseed rape The project aimed at increasing knowledge of precision establishment of oil seed rape. The hypothesis was that precision sowing in rows with low seed rates and close placing of N will optimize crop autumn development, overwintering, and seed pay-off. In total 12 field trials were conducted in southern and middle Sweden during the harvest years 2019–2022. Treatments included seeding with Väderstad Tempo, 45 cm row spacing, and seeding rates of 20, 35, 50 and 65 plants per m2. As a reference seeding was also done traditionally with a Väderstad Rapid, 12,5 cm row spacing and 50 plants per m2. In average there were no effect of neither seed rate nor row spacing on yield. In individual field experiments where low seed rates yielded better than high seed rates, this followed on a well-developed oil seed rape plant with a high shoot- and root biomass and a large root neck diameter in late autumn. Physiological plant development was affected by seed rate. Number of leaves, root neck diameter and above and below ground biomass was negatively correlated to the seed rate while there was a tendency for the growing point being positively correlated to the seed rate. The number of leaves per plant, shoot and rot biomass and to some extent also root neck diameter and the height of growing point was positively correlated to accumulated day degrees during autumn.

Biochar in bedding for loose housed laying hens - for the improvement of work and animal environment The aim of this project was to study how the ambient air environment in barns for loose housed laying hens is affected by mixing biochar into the bedding. The objectives were to investigate the bedding’s effect on the ammonia and the dust/particulate matter (PM) concentrations. Studies were performed by laboratory studies and by field trials in aviaries with loose housed laying hens. In the lab study, dust formation was tested by tumbling (stirring) three different types of biochar and one product of wood shavings. Wood shavings were used as a control/comparative bedding material, as it is the most common source of litter in Swedish laying hen flocks. The dust formation was higher for biochar compared to the wood shavings. Additionally, a higher dry matter content in the biochar resulted in higher dust concentrations. Presumably, this is because biochar is a porous material, which easily falls apart during mechanical processing. In practice, the mechanical processing will supposedly not be so forcefully because of e.g., the hens pecking in the bedding. However, it might be an aspect to consider during some work tasks, e.g., removal of the bedding. During the field trials, data of ammonia concentrations and PM were collected in four aviaries with 100 loose housed laying hens per aviary. Each aviary was provided with different mixtures of bedding material. The mixtures were 1) wood shavings and a bacteria/fungi additive, 2) only wood shavings, 3) wood shavings and biochar, and 4) peat or peat mixture (80% peat and 20% wood shavings). The measurements of ammonia were collected with a hand-held aspirator pump, one sample above the slatted flooring and two samples above the bedded flooring. No differences of the ammonia concentrations were obtained in the different aviaries, bedding materials and flooring. Differences in ammonia concentrations were not assumed above the slatted flooring, but above the bedded flooring. In future studies, continuous measurements and more data sampling would be relevant to analyze, to compare differences in the ammonia concentrations, depending on the bedding material, and correlate it to the time of day, the behavior/activity level of the laying hens, etc. The fractions of PM measured during the field trials were PM1, PM2.5, PM4, PM10 and total-PM. In each of the four aviaries, approximately 500 samples were taken with a laser photometer. The results were slightly different compared to the laboratory study. For all the PM fractions, the PM concentrations were highest in the bedding with only wood shavings. An influencing factor may be the dry matter content of the bedding materials, 90% for wood shavings and 70% for biochar. Another aspect is the laying hens’ activation and encouragement to process the bed by pecking, dust bathing etc. Both the laying hens and the eggs, in the aviary with biochar, appeared to have a greyish color at times. This study shows that the dry matter content of bedding materials is important for the dust/PM concentrations in the ambient air in animal production facilities. How different biochar with different properties, e.g. dry matter content and size fractions, affect the behavior of the laying hens (encouragement to process the bedding) is a topic for future research. One conclusion is that different biochar may have very different properties and that these varying properties can have quite different effects on the behavior of the laying hens, animal environment and work environment.

The agricultural industry plays a crucial role in transitioning towards a sustainable and fossil-free future. This article explores the potential of biorefineries using biomass from agriculture to reduce emissions and promote self sufficiency. Regarding a concept that integrated anaerobic digestion, grass and legume protein production, and hydrothermal liquefaction. A case study was conducted in the southwestern part of Sweden, involving interviews with a biogas plant and local farmers. The study analyzed the utilization of input goods in agriculture and evaluated the potential of biomass in the area. To assess the potential for farms to become self-sufficient in fuel, protein feed, and plant nutrients. The results show an overall positive outlook of the biorefinery concept. By utilizing 20% of the available biomass in the area can the biorefinery concept annually produce 100 GWh of biogas, 3800 tonnes of grass and legume protein concentrate and 1200 GWh bio-oil. This could theoretically cover 100 % of the need of soy meal, 44% for nitrogen, 50% for phosphorus and 100% for potassium.

Inoculation of legumes is generally considered to increase yield and to lower the need of nitrogen (N) fertilization, especially in semiarid regions and on sandy soils. It has not been clear whether inoculation with Rhizobium sp. in cropping of faba beans (Vicia faba minor) under Swedish conditions would improve yield and protein content. In 2015–2016, three faba bean cultivars and two strains of Rhizobium were studied in field trials in Central Sweden, including analyses of N fixation capacities using 15N abundance. The study did not show any effects of inoculation of Rhizobium on yield or protein content of faba beans or subsequent spring wheat yields. Yields of faba beans varied between cultivars but were not connected to inoculation. 15N abundance was influenced by rhizobium. The study cannot support the opinion that, generally, inoculation is beneficial for improved outcome of faba bean cropping under Scandinavian field conditions. No residual effect of inoculation on subsequent spring wheat yield was found. Copyright © 2023 Fogelberg, Östlund and Myrbeck.

Agricultural Biorefinery - combining local and regional scale In order to achieve Sweden's sustainability goals and an increased degree of self-sufficiency, our resources need to be used in an innovative way. Resources that today are classified as residual streams can be used in a smarter way to produce the future's food, feed, fuel and energy. There is a great potential in utilizing agricultural biomasses. In the project, the potential of agriculture to supply ILUC-free feedstock to a local and regional biorefinery concept was calculated and the system was evaluated through mass and energy flow calculations, cost calculations and case descriptions on Vårgårda Herrljunga Biogas Plant (VH Biogas). In addition, practical tests were carried out on bio-oil production from dewatered digestate from participating biogas plants. Quantifications were also carried out of how the concept contributes to more resource-efficient crop cultivation with maintained humus content in soil despite increased removal of biomass from the farm. ...

The POWER project aimed to examine the effectiveness of innovations and best practise in achieving improved pig welfare in Europe. Free-range pasture systems for pigs support the organic principles of natural living, but intensive free-range production is characterized by high risks of nutrient losses, such as nitrogen (N) and phosphorus (P) leaching to surrounding water bodies and also ammonia (NH3) emissions. The scope of this grazing study, with housing pigs on pasture, was eight pig farms located in four countries: Austria, Denmark, Germany and Sweden. Collected farm data showed a large range in values, reflecting the diversity of pasture systems. Average animal density in paddocks per farm varied between 10 and 480 pigs per hectare, with a density in falling order as weaners>fatteners>sows. Vegetation in paddocks varied greatly between farms and also in paddocks within the same farm. Climate, animal density and soil type are important parameters influencing the risk of nutrient losses. Nutrient loads from faeces and urine in paddocks varied with animal density. The calculated loads were rather high in relation to fertilizing needs in crop production at some of the studied farms. This highlights the importance of having enough area for the pigs and/or to limit the period they are hold in the same paddock in order to apply nutrient loads balanced to subsequent crop or vegetation needs. With the highest N load registered in the study, pigs could be held in the paddock approximately one and a half month per year before exceeding the EU regulation of maximum application of 170 kg N per ha with animal manure.

Ecological intensification (EI) could help return agriculture into a ‘safe operating space’ for humanity. Using a novel application of meta-analysis to data from 30 long-term experiments from Europe and Africa (comprising 25,565 yield records), we investigated how field-scale EI practices interact with each other, and with N fertilizer and tillage, in their effects on long-term crop yields. Here we confirmed that EI practices (specifically, increasing crop diversity and adding fertility crops and organic matter) have generally positive effects on the yield of staple crops. However, we show that EI practices have a largely substitutive interaction with N fertilizer, so that EI practices substantially increase yield at low N fertilizer doses but have minimal or no effect on yield at high N fertilizer doses. EI practices had comparable effects across different tillage intensities, and reducing tillage did not strongly affect yields. © 2022, The Author(s)