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Animal production intensification puts pressure on resources, leads to environmental impacts, animal welfare and biodiversity issues. Livestock products provide key components of the human diet and contribute to rural territories through ecosystem services such as nutrient and biomass recycling. Life cycle assessment (LCA) is key to assess environmental impacts in livestock systems and products. A harmonization of LCA methods is necessary to improve evaluations in these areas as LCA still lacks accuracy and robustness in addressing sustainability across livestock systems and products. Here, a participatory harmonization approach was applied to provide a framework to evaluate LCAs of current and future livestock systems. A total of 29 workshops with targeted discussions among 21 LCA experts were organised, together with two anonymous surveys to harmonise evaluation criteria. First, key research topics for improving LCAs of livestock systems were identified as follows: i) Food, feed, fuel and biomaterial competition, crop-livestock interaction and the circular economy; ii) Biodiversity; iii) Animal welfare; iv) Nutrition; v) GHG emissions. Next, general evaluation criteria were identified for livestock focussed LCA methods, considering livestock systems characteristics: Transparency and Reproducibility, Completeness, Fairness and Acceptance, Robustness and Accuracy. Evaluation criteria specific to each key topic were also identified. This participatory method was successful in narrowing down general and specific evaluation criteria through targeted discussion. Moreover, this study provided a holistic participatory framework for the evaluation of LCA methods addressing the impacts of livestock systems across a range of key topics which can be further used for other sectors.

For at producere mere effektive gødninger til økologisk produktion blev kløvergræs og kvæggylle brugt til at producere forskellige organiske gødningstyper samt biogas ved anvendelse af forskellige efterbehandlingsteknologier. Ideen bag var at øge mængden af plantetilgængeligt kvælstof (N) i gødningen og reducere emissionerne. Resultaterne viste en positiv effekt på gødningens klimapåvirkning sammenlignet med ubehandlet gylle, på grund af reducerede metanemissioner fra opbevaring af gylle og den producerede biogas, der kan erstatte fossile brændstoffer.

For at producere mere effektive gødninger til økologisk produktion blev kløvergræs og kvæggylle brugt til at producere forskellige organiske gødningstyper samt biogas ved anvendelse af forskellige efterbehandlingsteknologier. Husdyrgødning kan bruges direkte på marken som gødning. Alternativt kan husdyrgødningen afgasses i et biogasanlæg og den afgassede biomasse kan så bruges på marken som gødning. Et andet alternativ er gå videre med forarbejdningen og separere den afgassede biomasse i en flydende og fast fraktion, der så kan bruges som gødning på marken og derudover via en stripning af den faste fraktion og svovl fra biogasprocessen producere en NS-gødning. Disse forskellige gødningstyper har forskellige kemiske og fysiske egenskaber, hvilket kan påvirke drivhusgasemissionerne under forarbejdning, opbevaring og anvendelse på marken. I ClimOptic-projektet blev gødningerne fremstillet og brugt i et markforsøg med vårbyg, hvor emissioner under lagring og i marken blev målt. Livscyklusvurdering (LCA) blev brugt som metode for at undersøge klimaeffekten af at producere og bruge de forskellige gødningstyper fremfor at bruge husdyrgødningen direkte eller bruge det afgassede biomasse før separering til gødning. Klimaaftrykket af I) de producerede gødningstyper (kg CO2e per 100 kg total N) og II) vårbyg produceret med de forskellige gødningstyper (kg CO2e per t tørstof vårbyg) blev estimeret. Resultaterne viste overordnet en positiv effekt på gødningens klimapåvirkning sammenlignet med ubehandlet gylle, primært på grund af reducerede emissioner fra opbevaring af gylle og genanvendt biogas fra behandlingerne, der kan erstatte fossile brændstoffer. Klimaaftrykket af 100 kg total N i de forskellige gødningstyper viste en reduktion på 75-87%, når ubehandlet kvæggylle blev erstattet med afgasset biomasse eller mere forarbejdede gødningsprodukter. Den primære årsag til de reducerede klimaaftryk i de behandlede gødningstyper sammenlignet med ubehandlet kvæggylle er de reducerede

An organic diet has the potential to create a positive effect on biodiversity and ecotoxicity, whereas climate impact is often at a similar level for organic and conventional diet, and land use per kg food is higher for organic food. The contribution of organic food production to the sustainability goals depends to a high degree on the composition of the organic diet. The aim of the present study was to investigate the environmental effect of changing from the current Danish conventional diet with an average composition of food items to an organic diet with same composition of food items. Furthermore, to investigate for both type of diets – the effect of changing from the current composition of the diet to a more plant-based diet. The environmental impact investigated was the climate effect, the effect on land use, on plant diversity on cultivated area, eco toxicity, pesticide residues in foods, and animal welfare. When changing from the current composition of the conventionally diet to a more plant-based diet, both carbon footprint and land use was reduced with around 30%. Ecotoxicity was reduced with 38%, as a high proportion of the contribution hereof came from the animal-based foods, whereas the amount of food with risk of pesticide residues was increased with 21% as pesticide residues were only found in plant-based foods. When changing from a conventionally to an organically produced diet, carbon footprint was not affected, but land use was increased. However, with the plant based organic diet, land use was 5% lower than in the current conventionally diet. The loss of plant species on the cultivated area for the organic diet was only half of that in the conventional diet, ecotoxicity of an organic diet was nearly 4 times lower, and the amount of food with risk of pesticide residues was more than 10 times lower that in the conventional diet. Finally, an organic diet has a positive effect on animal welfare.

Anaerobic digestion is a widely used method for treating liquid manure (slurry) and other biomasses, producing biogas as a renewable energy source for heating and electricity generation. The digestate from the biogas plant can be further processed to produce alternative organic fertilizers and enhance nutrient recycling, but the impact of digestate post-treatment on the environment needs to be further investigated. In this study, using a life cycle assessment approach, we explored how fertilizers derived from cattle slurry and grass-clover co-digestion treatment (digestate, solid and liquid fractions from digestate separation, and an enriched liquid nitrogen-sulfur product derived from post-processing of biogas and drying of the solid fraction) may influence the greenhouse gas (GHG) balance compared to the baseline scenario with untreated cattle slurry. To perform this analysis, results from experiments were used together with data from existing literature and databases. The chosen functional units were I) 100 kg of total nitrogen in the final organic fertilizer and II) 1 ton of spring barley dry matter (DM). The respective system boundaries were cradle-to-processing gate and cradle-to-field application, respectively. The global warming potential (GWP) of production and storage of the alternative organic fertilizers were 13 to 25% of the baseline scenario. When considering the second functional unit, the carbon footprint were 25 to 140% of the baseline scenario. The main hotspots in the carbon footprint of the fertilizers were GHG emissions from storage and field application of the organic fertilizers, and production of the grass-clover, whereas the biogas produced by anaerobic digestion greatly reduced the GWP. The present study shows that there is significant potential for climate impact mitigation in the replacement of untreated slurry with alternative fertilizers derived from anaerobic digestion, mainly due to reduced emissions during storage, and the production

In recent years, there has been a growing interest in investigating whether the organic food production and consumption result in better environmental profile compared to conventional food. To assess and compare environmental impact of organic food with conventional food as well as to assess impact of life cycle assessment (LCA) methodological choices, this meta-analysis systematically analysed 104 published studies on both animal and plant products. This was done comparing eight impact categories of global warming (GWP), acidification, eutrophication, eco-toxicity potential, biodiversity loss, energy, water and land use for both mass- and area-based functional units from cradle-to-farm gate. The review shows that the majority of studies have been performed in Europe and North America, with a large focus on GWP and little focus on biodiversity loss, eco-toxicity potential and water use. Only few studies included the effect on soil carbon sequestration for estimation of GWP or direct land use change, and such studies were more recent. The meta-analysis showed variation within the results across different studies due to differences in compared systems and research methods. The only impacts that were found to differ significantly between the two production modes were lower GWP per area unit plus higher land use and lower energy use per mass unit for organic compared to conventional food. The key methodological challenges in LCA of food products are to develop methodologies to assess biodiversity, toxicity and land degradation and to improve models for better estimation of changes in soil carbon especially for organic food. Furthermore, the choice of the functional unit can affect the results. Therefore, including several functional units for LCA of organic food and assessing their impacts in a dietary context are required. Including results both at the product and diet level might therefore provide more holistic assessments and allow more comprehensive decisions.