Seaweed as a climate fix for meat and dairy production: an LCA perspective

Dairy production delivers nutrient-dense food but it also constitutes a major source of greenhouse gas (GHG) emissions. Feed formulation plays a central role in shaping both productivity and the climate footprint of dairy systems. This thesis investigated how feed ration formulation can reduce GHG emissions from Swedish high-producing dairy production whilst maintaining productivity. This was addressed across multiple system levels, from the individual animal to the regional food system. Two feeding trials with dairy cows and heifers evaluated animal performance and enteric methane (CH4) emissions. Study I compared two pelleted concentrate mixes, formulated with low-carbon-footprint (CF) by-products (BYP) and/or domestically sourced (DOM) ingredients, to a commercially available mix (COM). Both reduced feed-related GHG emissions without compromising feed intake, milk yield, or enteric CH4 emissions from high-producing (43.3 ± 5.4 kg ECM/d) Swedish Holstein cows. Study II tested a ration designed for forage scarcity, where whole-crop wheat silage was partially incorporated (50:50 DM basis) in grass-clover silage-based diets fed to Holstein and Nordic Red heifers. This substitution did not negatively affect feed intake, growth rate, or enteric CH4 emissions. Results from these trials were integrated into a farm-level life cycle assessment (Study III). At the farm level, when compared to COM, BYP decreased total farm-level GHG emissions (-6%) and land use (-3.8%), whilst DOM achieved smaller reductions in farm-level GHG emissions (-2.1% to -2.6%) but increased land use (up to +6.8%). At the regional level (Study IV), scenario modelling of dairy production in northern Sweden illustrated trade-offs among climate footprint, land use, feed self-sufficiency, and milk output. This thesis demonstrates that feed rations based on low-CF ingredients can reduce GHG emissions from high-yielding Swedish dairy production without compromising animal performance. However, the environmental outcomes depend on ingredient choice and system boundaries, highlighting the need to evaluate feeding strategies at multiple system levels to inform sustainable dairy development.

Livestock production contributes to greenhouse gas (GHG) emissions. However, there is a considerable variability in the carbon footprint associated with livestock production. Site specific estimates of GHG emissions are needed to accurately focus GHG emission reduction efforts. A holistic approach must be taken to assess the environmental impact of livestock production using appropriate geographical scale. The objective of this study was to determine baseline GHG emissions from dairy production in South Dakota using a life cycle assessment (LCA) approach. A cradle-to-farm gate LCA was used to estimate the GHG emissions to produce 1 kg of fat and protein corrected milk (FPCM) in South Dakota. The system boundary was divided into feed production, farm management, enteric methane, and manure management as these activities are the main contributors to the overall GHG emissions. The production of 1 kg FPCM in South Dakota dairies was estimated to emit 1.23 kg CO2 equivalents. The major contributors were enteric methane (46%) and manure management (32.7%). Feed production and farm management made up 14.1 and 7.2%, respectively. The estimate is similar to the national average but slightly higher than the California dairy system. The source of corn used in the dairies influences the footprint. For example, South Dakota corn had fewer GHG emissions than grain produced and transported in from Iowa. Therefore, locally and more sustainably sourced feed input will contribute to further reducing the environmental impacts. Improvements in efficiency of milk production through better genetics, nutrition animal welfare and feed production are expected to further reduce the carbon footprint of South Dakota dairies. Furthermore, anaerobic digesters will reduce emissions from manure sources.

The Irish dairy industry aims to increase milk production from grass-based farms following the removal of the EU milk-quota system, but is also required to minimise greenhouse gas (GHG) emissions to meet European reduction targets. Consequently, the sector is under increasing pressure to reduce GHG emissions per unit of milk, or carbon footprint (CF). Therefore, the goal of the present study was to determine the main sources of the CF of grass-based milk production and to identify mitigation strategies that can be applied to reduce farm footprints. In total, the CF of milk was estimated for 62 grass-based dairy farms in 2014. The method used to quantify GHG emissions was a life cycle assessment (LCA), independently certified to comply with the British standard for LCA (PAS 2050). The LCA method was applied to calculate annual on- and off-farm GHG emissions associated with dairy production until milk was sold from the farm in CO2-equivalent (CO2-eq). Annual GHG emissions computed using LCA were allocated to milk on the basis of the economic value of dairy products and expressed per kilogram of fat- and protein-corrected milk to estimate CF. Enteric methane was the main source of the CF of milk (46%), followed by emissions from inorganic N fertilisers (16%), manure (16%) and concentrate feedstuffs (8%). The mean CF of milk from the 62 farms was 1.26 kg of CO2-eq per kilogram of fat- and protein-corrected milk, but varied from 0.98 kg to 1.67 kg as measured using the 95% confidence interval. The CF of milk was correlated with numerous farm attributes, particularly N-fertiliser, the percentage of grazed grass in the diet, and production of milk solids. Grass-based dairy farmers can significantly improve these farm attributes by increasing herd genetic merit, extending the length of the grazing season and optimising N fertiliser use and, thereby, reduce the CF of milk.

Protein diversification

Greenhouse gas emissions and land use from confinement dairy farms in the Guanzhong plain of China – using a life cycle assessment approach

The impact of anthropogenic greenhouse gas (GHG) emissions on climate change receives much focus today. This impact is however often considered only in terms of global warming potential (GWP), which does not take into account the need for staying below climatic target levels, in order to avoid passing critical climate tipping points. Some suggestions to include a target level in climate change impact assessment have been made, but with the consequence of disregarding impacts beyond that target level. The aim of this paper is to introduce the climate tipping impact category, which represents the climate tipping potential (CTP) of GHG emissions relative to a climatic target level. The climate tipping impact category should be seen as complementary to the global warming impact category. The CTP of a GHG emission is expressed as the emission’s impact divided by the ‘capacity’ of the atmosphere for absorbing the impact without exceeding the target level. The GHG emission impact is determined as its cumulative contribution to increase the total atmospheric GHG concentration (expressed in CO2 equivalents) from the emission time to the point in time where the target level is expected to be reached, the target time. The CTP of all the assessed GHGs increases as the emission time approaches the target time, reflecting the rapid decrease in remaining atmospheric capacity and thus the increasing potential impact of the GHG emission. The CTP of a GHG depends on the properties of the GHG as well as on the chosen climatic target level and background scenario for atmospheric GHG concentration development. In order to enable direct application in life cycle assessment (LCA), CTP characterisation factors are presented for the three main anthropogenic GHGs, CO2, CH4 and N2O. The CTP metric distinguishes different GHG emission impacts in terms of their contribution to exceeding a short-term target and highlights their increasing importance when approaching a climatic target level, reflecting the increasing urgency of avoiding further GHG emissions in order to stay below the target level. Inclusion of the climate tipping impact category for assessing climate change impacts in LCA, complimentary to the global warming impact category which shall still represent the long-term climate change impacts, is considered to improve the value of LCA as a tool for decision support for climate change mitigation.

A life cycle assessment (LCA) approach was used to examine the greenhouse gas (GHG) emissions and energy balance of short rotation coppice (SRC) willow for heat production. The modelled supply chain includes cutting multiplication, site establishment, maintenance, harvesting, storage, transport and combustion. The relative impacts of dry matter losses and methane emissions from chip storage were examined from a LCA perspective, comparing the GHG emissions from the SRC supply chain with those of natural gas for heat generation. The results show that SRC generally provides very high GHG emission savings of over 90 %. The LCA model estimates that a 1, 10 and 20 % loss of dry matter during storage causes a 1, 6 and 11 % increase in GHG emissions per MWh. The GHG emission results are extremely sensitive to emissions of methane from the wood chip stack: If 1 % of the carbon within the stack undergoes anaerobic decomposition to methane, then the GHG emissions per MWh are tripled. There are some uncertainties in the LCA results, regarding the true formation of methane in wood chip stacks, non-CO2 emissions from combustion, N2O emissions from leaf fall and the extent of carbon sequestered under the crop, and these all contribute a large proportion of the life cycle GHG emissions from cultivation of the crop.

The hydrogen (H2) economy is seen as a crucial pathway for decarbonizing the energy system, with green H2—i.e., obtained from water electrolysis supplied by renewable energy—playing a key role as an energy carrier in this transition. The growing interest in H2 comes from its versatility, which means that H2 can serve as a raw material or energy source, and various technologies allow it to be produced from a wide range of resources. Environmental impacts of H2 production have primarily focused on greenhouse gas (GHG) emissions, despite other environmental aspects being equally relevant in the context of a sustainable energy transition. In this context, Life Cycle Assessment (LCA) studies of H2 supply chains have become more common. This paper aims to compile and analyze discrepancies and convergences among recent reported values from 42 scientific studies related to different H2 production pathways. Technologies related to H2 transportation, storage and use were not investigated in this study. Three environmental indicators were considered: Global Warming Potential (GWP), Energy Performance (EP), and Water Consumption (WF), from an LCA perspective. The review showed that H2 based on wind, photovoltaic and biomass energy sources are a promising option since it provides lower GWP, and higher EP compared to conventional fossil H2 pathways. However, WF can be higher for H2 derived from biomass. LCA boundaries and methodological choices have a great influence on the environmental indicators assessed in this paper which leads to great variability in WF results as well as GWP variation due credits given to avoid GHG emissions in upstream process. In the case of EI, the inclusion of energy embodied in renewable energy systems demonstrates great influence of upstream phase for electrolytic H2 based on wind and photovoltaic electricity.

Feeding a growing, increasingly affluent population while limiting environmental pressures of food production is a central challenge for society. Understanding the location and magnitude of food production is key to addressing this challenge because pressures vary substantially across food production types. Applying data and models from life cycle assessment with the methodologies for mapping cumulative environmental impacts of human activities (hereafter cumulative impact mapping) provides a powerful approach to spatially map the cumulative environmental pressure of food production in a way that is consistent and comprehensive across food types. However, these methodologies have yet to be combined. By synthesizing life cycle assessment and cumulative impact mapping methodologies, we provide guidance for comprehensively and cumulatively mapping the environmental pressures (e.g., greenhouse gas emissions, spatial occupancy, and freshwater use) associated with food production systems. This spatial approach enables quantification of current and potential future environmental pressures, which is needed for decision makers to create more sustainable food policies and practices.

Comparing the environmental efficiency of milk and beef production through life cycle assessment of interconnected cattle systems

Environmental impacts along intensity gradients in Norwegian dairy production as evaluated by life cycle assessments

Identification of an environmentally friendly symbiotic process for the reuse of industrial byproduct – an LCA perspective

Current and potential materials for the low-carbon cement production: Life cycle assessment perspective

Bioelectrochemical systems (BESs) such as microbial fuel cells (MFCs) present numerous benefits for the removal and recovery of heavy metals from industrial and municipal wastewater. This study evaluated the life cycle environmental impact of simultaneous hexavalent chromium (Cr(vi)) removal and bioelectricity generation in a dual chamber MFC. Results indicate a global warming potential (GWP) of −0.44 kg carbon dioxide (CO2)-eq. per kg of chromium recovered, representing a total saving of up to 97% in comparison with existing technologies for the treatment of Cr(vi) laden wastewater. The observed savings in GWP (kg CO2-eq.) reduced to 61.8% with the removal of the allocated credits from the MFC system's life cycle. Of all the various sub-systems considered within the chromium waste treatment plant, the MFC unit and the chromium metal recovery unit had the largest impact in terms of GWP (kg CO2-eq.), non-renewable energy use (NREU) (MJ primary), and mineral extraction (MJ surplus). A statistical analysis of the results showed that an increase in chemical oxygen demand (COD) was associated with a reduction in GWP (kg CO2-eq.), NREU (MJ primary), and terrestrial ecotoxicity (kg triethylene glycol equivalents into soil (TEG soil)-eq.). The life cycle assessment (LCA) output showed a high sensitivity to changes in the materials and construction processes of MFC reactors, indicating the need for further research into sustainable materials for MFC reactor construction. The observed interaction effects of process variables also suggest the need for combined optimization of these variables. Analysis with other types of metals is also important to further demonstrate the practical viability of metal removal through MFCs.

Extensive dairy production in less favorable production areas has a long tradition in Austria. Nevertheless, dairy production also contributes considerable environmental impacts (EIs), e.g., greenhouse gas emissions, nutrient losses, and land use. Therefore, 20 organic dairy farms located in the Lungau region in Austria were assessed concerning their EIs via life cycle assessment (LCA). Cumulative exergy demand (CExD), normalized eutrophication potential (EP), aquatic ecotoxicity potential (AE), and global warming potential (GWP) were considered as impact categories to describe the farms' EIs. The farms were part of a pilot project aiming to produce high-quality dairy products and keep production cycles closed within the project region. Consequently, the purchase of key off-farm resources was only possible within the project region. We adapted existing life cycle inventories to account for those regional resource purchases. Subsequently, the EIs of the 20 farms were related to the functional units (FUs) of 1 kg energy-corrected milk (ECM) and 1 ha agricultural area for milk production and compared to a representative model dairy farm (MDF) that was created based on statistical data and average production values of organic Austrian dairy farms. Compared to the MDF, results show an ~58% lower EP per ha and 44% per kg ECM of the Lungau farms. Further, the CExD per ha was about 24% lower due to a lower use of resources caused by the lower production intensity of the Lungau farms. Regarding GWP, Lungau farms are favorable considering 1 ha as the FU, whereas the MDF seems advantageous if 1 kg ECM is used as the FU. However, caused by a high variation of purchased roughage and the lower production intensity, the Lungau farms cause higher AE, regardless of the FU. Overall, we identified three principal production parameters determining the environmental performance of milk production in a closed production cycle in a less favorable area, namely, (1) the stocking rate, (2) the fed concentrate, and (3) the purchased roughage. Using those inputs at moderate intensity, the extensively managed Lungau farms can competitively contribute to producing food, thus highlighting the importance of site-adapted agriculture.