Search

Introduction: With the continuous growth of Atlantic salmon (Salmo salar L.) aquaculture, appropriate management of nutrient-rich waste streams from both land- and sea-based production has become increasingly important. Following a circular approach, nutrients contained in aquaculture sludge can be utilized for biomass production of the polychaete Hediste diversicolor. While the potential for upcycling nutrients has been established previously, this study aimed to assess nutrient flows in H. diversicolor fed aquaculture sludge as understanding these will be crucial for optimizing future large-scale production of this species. Materials and methods: We investigated the effect of low and high feed supply of smolt sludge on the nutrient flows of carbon (C), nitrogen (N), and phosphorus (P) in H. diversicolor on an individual level. Hereby we assessed ingestion, defecation, excretion, respiration, and uptake for growth. Results and discussion: Nutrient flows differed between the nutrients C, N, and P in the high feed supply group where C uptake for growth was significantly higher than N and P uptake, and N uptake was significantly higher than P uptake. In contrast, no significant differences were observed in the low feed supply group. In the high feed supply group, most of the ingested C, N, and P by H. diversicolor was allocated to uptake for growth (76% C, 83% N, 85% P) with smaller proportions allocated to defecation (7% C, 7% N, 11% P) and respiration/ excretion (18% C, 9% N, 5% P). The results from the low feed supply group suggest insufficient nutrient supply as most ingested C was allocated to respiration (84%), while most N was expended on uptake for growth (45%), and ingested P was either taken up for growth (58%) or spent on defecation (34%). Overall, nutrient uptake reflected the smolt sludge composition rather than nutrient requirements for H. diversicolor, which may be a short-term effect and needs to be investigated further. The flow of nutrients was strongly affected by feed supply, as ingestion, defecation, excretion, and uptake for growth were significantly higher in the high feed supply group than in the low feed supply group. [ABSTRACT FROM AUTHOR]

IntroductionWith the continuous growth of Atlantic salmon (Salmo salar L.) aquaculture, appropriate management of nutrient-rich waste streams from both land- and sea-based production has become increasingly important. Following a circular approach, nutrients contained in aquaculture sludge can be utilized for biomass production of the polychaete Hediste diversicolor. While the potential for upcycling nutrients has been established previously, this study aimed to assess nutrient flows in H. diversicolor fed aquaculture sludge as understanding these will be crucial for optimizing future large-scale production of this species.Materials and methodsWe investigated the effect of low and high feed supply of smolt sludge on the nutrient flows of carbon (C), nitrogen (N), and phosphorus (P) in H. diversicolor on an individual level. Hereby we assessed ingestion, defecation, excretion, respiration, and uptake for growth.Results and discussionNutrient flows differed between the nutrients C, N, and P in the high feed supply group where C uptake for growth was significantly higher than N and P uptake, and N uptake was significantly higher than P uptake. In contrast, no significant differences were observed in the low feed supply group. In the high feed supply group, most of the ingested C, N, and P by H. diversicolor was allocated to uptake for growth (76% C, 83% N, 85% P) with smaller proportions allocated to defecation (7% C, 7% N, 11% P) and respiration/excretion (18% C, 9% N, 5% P). The results from the low feed supply group suggest insufficient nutrient supply as most ingested C was allocated to respiration (84%), while most N was expended on uptake for growth (45%), and ingested P was either taken up for growth (58%) or spent on defecation (34%). Overall, nutrient uptake reflected the smolt sludge composition rather than nutrient requirements for H. diversicolor, which may be a short-term effect and needs to be investigated further. The flow of nutrients was strongly affected by feed supply, as ingestion, defecation, excretion, and uptake for growth were significantly higher in the high feed supply group than in the low feed supply group.

Introduction: Focusing on circular bioeconomy and finding solutions for managing finite and scarce resources such as phosphorus are issues that need to be addressed across sectors to attain food security. Land-based aquaculture of Atlantic salmon (Salmo salar L.) smolt and post-smolt results in a large output of aquaculture sludge. These nutrient-rich side streams from aquaculture production constitute a valuable resource for cultivation of polychaetes Hediste diversicolor. The aim of this study was to evaluate the capacity of H. diversicolor to upcycle carbon (C), nitrogen (N), and phosphorus (P) contained in aquaculture sludge from Norwegian salmon production. Material and methods: We investigated the effect of two diets, smolt sludge and post-smolt sludge, which were supplied at four different feed levels, on the gain of C, N, and P in H. diversicolor and established uptake rates for the upcycling of these nutrients. Additionally, we examined how different feed composition (type of diet) and supply (feel level) influenced C, N, and P content as well as the elemental ratios of H. diversicolor. Results and discussion: Polychaetes fed with both types of sludge were shown to incorporate C, N, and P from their diets into biomass. Incorporation of C, N, and P in polychaete biomass was highest at the highest feed levels, following specific growth rates. Uptake of diet C, N, and P into polychaete biomass was similar for both diets and across feed levels. On average, C and N uptake rates amounted to 2-10% and 2-15%, respectively, while values for P uptake were lower at 0.5-1.5%. C, N, and P content of polychaetes was not affected by different diets or feed levels while the C:N ratio increased with increasing feed supply. Overall, we found that H. diversicolor can successfully take up nutrients contained in aquaculture sludge and thus can be beneficial for upcycling of side streams from Atlantic salmon production. [ABSTRACT FROM AUTHOR]

IntroductionFocusing on circular bioeconomy and finding solutions for managing finite and scarce resources such as phosphorus are issues that need to be addressed across sectors to attain food security. Land-based aquaculture of Atlantic salmon (Salmo salar L.) smolt and post-smolt results in a large output of aquaculture sludge. These nutrient-rich side streams from aquaculture production constitute a valuable resource for cultivation of polychaetes Hediste diversicolor. The aim of this study was to evaluate the capacity of H. diversicolor to upcycle carbon (C), nitrogen (N), and phosphorus (P) contained in aquaculture sludge from Norwegian salmon production.Material and methodsWe investigated the effect of two diets, smolt sludge and post-smolt sludge, which were supplied at four different feed levels, on the gain of C, N, and P in H. diversicolor and established uptake rates for the upcycling of these nutrients. Additionally, we examined how different feed composition (type of diet) and supply (feel level) influenced C, N, and P content as well as the elemental ratios of H. diversicolor.Results and discussionPolychaetes fed with both types of sludge were shown to incorporate C, N, and P from their diets into biomass. Incorporation of C, N, and P in polychaete biomass was highest at the highest feed levels, following specific growth rates. Uptake of diet C, N, and P into polychaete biomass was similar for both diets and across feed levels. On average, C and N uptake rates amounted to 2–10% and 2–15%, respectively, while values for P uptake were lower at 0.5–1.5%. C, N, and P content of polychaetes was not affected by different diets or feed levels while the C:N ratio increased with increasing feed supply. Overall, we found that H. diversicolor can successfully take up nutrients contained in aquaculture sludge and thus can be beneficial for upcycling of side streams from Atlantic salmon production.

Ecologically designed wastewater treatment systems (ex., Eco-Machines™) utilize a diverse ecosystem to treat wastewater to the same extent as conventional treatment, but require less energy and chemical inputs. The environmental benefits of Eco-Machines™ can be theoretically maximized by incorporating hyperaccumulating aquatic plants (ex., duckweed) to facilitate nutrient recovery and conversion into protein-rich biomass, which can then be harvested for a range of agricultural and bioenergy applications. Although it has been established that ecological wastewater treatment systems are more cost- and energy-efficient than conventional wastewater treatment systems, a systematic life cycle assessment (LCA) of an Eco-Machine™ coupled with its beneficial by-products has not been conducted. In this study, a series of LCAs were performed on different operational scenarios for a 1000 gallon per day, pilot-scale Eco-Machine™ that, in addition to producing irrigation-quality water, also produces duckweed biomass for aquaculture. The analysis revealed that Eco-Machines™ located in warm climates, which do not require a greenhouse or supplemental heating, use approximately a third of the energy and produce half of the greenhouse gas emissions compared to conventional wastewater treatment systems in similar locations, while also providing benefits to human health, ecosystem quality, climate change, and resources. In addition, increasing the growth area for duckweed using vertical farming techniques improves the overall impact of the system. This study suggests that with proper management, ecological wastewater treatment systems that upcycle nutrients and water into beneficial products can provide a net benefit to human health and the environment. • First LCA of ecological wastewater treatment coupled with duckweed production. • Eco-Machines™ can provide a net benefit to human health and the environment. • Increasing duckweed production increases the beneficial impacts of Eco-Machines™. [ABSTRACT FROM AUTHOR]