Life-cycle assessment of yeast-based single-cell protein production with oat processing side-stream.

Production of fish meal and plant-based feed proteins continues to increase to meet the growing demand for seafood, leading to impacts on marine and terrestrial ecosystems. Microbial proteins such as single-cell proteins (SCPs) have been introduced as feed alternatives since they can replace current fish feed ingredients, e.g., soybean, which are associated with negative environmental impacts. Microbial protein production also enables utilization of grain processing side-streams as feedstock sources. This study assesses the environmental impacts of yeast-based SCP using oat side-stream as feedstock (OS-SCP). Life-cycle assessment with a cradle-to-gate approach was used to quantify global warming, freshwater eutrophication, marine eutrophication, terrestrial acidification, land use, and water consumption of OS-SCP production in Finland. Dried and wet side-streams of oat were compared with each other to identify differences in energy consumption and transportation effects. Sensitivity analysis was performed to examine the difference in impacts at various locations and fermentation times. Benchmarking was used to evaluate the environmental impacts of OS-SCP and other feed products, including both conventional and novel protein products. Results highlight the importance of energy sources in quantifying the environmental performance of OS-SCP production. OS-SCP produced with dried side-streams resulted in higher global warming (16.3 %) and water consumption (7.5 %) than OS-SCP produced from wet side-streams, reflecting the energy and water requirements for the drying process. Compared with conventional products, such as soy protein concentrates, OS-SCP resulted in 61 % less land use, while exacerbating the environmental impacts in all the other categories. OS-SCP had more impact on global warming (205-754 %), water consumption (166-1401 %), freshwater eutrophication (118-333 %), and terrestrial acidification (85-340 %) than other novel products, including yeast protein concentrate, methanotrophic bacterial SCP, and insect meal, while lowering global warming (11 %) and freshwater eutrophication (20 %) compared with dry microalgae biomass.

Circular economy for phosphorus supply chain and its impact on social sustainable development goals.

To be able to grow crops, we have interfered with Earth's reserves of one of top three essential elements, phosphorus (P), as to which we face a problem related to its high consumption compared to available resources. This forces us to follow the alternative of closing the phosphorus loop from a circular economy perspective. However, there is a lack of research on regional and global social sustainability in this area, as emphasized in the United Nations' Agenda 2030 goals for sustainable development. In this paper, we address social challenges involved in global phosphorus supply chain, such as eradicating poverty, child labor and malnutrition; promoting gender equality; providing decent work and economic growth; maintaining sustainable water use; and achieving food security. Our research is driven by the question of whether the circular economy aims to direct phosphorus management towards tackling social issues associated with its supply chain. We use system dynamics modelling by combining the concept of material flow analysis and social life cycle assessment. Detailed analysis at regional and global levels indicates a paradoxical social impact of phosphorus circular model. This reflects the multiple stakeholders involved, and the regional interactions with phosphorus circular economy transitions. Improvements can be demonstrated in reducing poverty and providing safer work environment in many regions, e.g., Western Asia (93%), New Zealand, Central Asia, and Europe (44-61%), while achieving employment targets is limited in Northern and Eastern Europe. Circular model fails to promote gender equality, it also exacerbates exploitative child work problem for the Caribbean and most Africa. It provides sufficient nutrition to North America, Australia/New Zealand, and Northern Europe. It achieves water use targets in several regions with 53% savings worldwide. Finally, circular model contributes to P efficiency (average balance of 1.21 kgP/ha) and strengthens P security within most regions with an average of 64%.

Environmental sustainability of phosphorus recycling from wastewater, manure and solid wastes.

Phosphorus (P) is an important critical material essential for crops cultivation and animal husbandry. Effective phosphorous recycling is considered one of the most significant factors in alleviating its criticality. However, despite the importance of phosphorous recycling, its sustainability is not studied extensively. This paper aims to answer the question if recycling of phosphorus is an environmentally sustainable option. To address this problem, two issues are analyzed in this paper: energy consumption and greenhouse gas (GHG) emissions in phosphorous recycling. The analysis was performed by simulating mass and energy flows in the global phosphorus supply chain (from mining to recycling) in order to understand and analyze its environmental impact in 2000-2050. The results of simulation show that around 82% of recycled phosphorous originates from manure. Moreover, the calculations indicate that about 70% of total GHG emissions from phosphorous recycling is caused by wastewater processing. In addition, the results show that phosphorous obtained from recycled wastewater constitutes only 2% of the whole amount recovered in the recycling process. Therefore, the obtained results show a clear need for a detailed analysis of the sustainability of phosphorous recycling processes. Moreover, the analysis of scenarios of phosphorus consumption indicates that GHG emissions increase slowly in the mining phase and grow exponentially in the recycling stage. The main finding of this paper contradicts the general opinion about environmental friendliness of recycling. It shows that phosphorus recycling is not a sustainable solution in a longer perspective.