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[Display omitted] • C. vulgaris -S395-2- C. rosea for aquaculture wastewater treatment were proposed. • Gibberellins enhances the attenuation of studied aquaculture pollutants. • Pollutant attenuation showed a high fungus strains dependence. • The maximum OTC removal efficiencies were 98.29 % ± 1.15 %. This study assessed the effect of gibberellins (GAs) concentrations on antibiotic and nutrient removal using diverse microalgal-bacterial-fungal consortia. Five systems (Chlorella vulgaris , T1; C. vulgaris + S395-2 + Clonostachys rosea, T2; C. vulgaris + S395-2 + Ganoderma lucidum , T3; C. vulgaris + S395-2 + Pleurotus pulmonarius , T4; and C. vulgaris + S395-2, T5) were established, and optimal conditions and effective symbiosis were applied to improve antibiotic and nutrient removal. Consortium growth was T2 > T3 > T5 > T4 > T1, while GA impact ranked 50 mg L–1 > 20 mg L–1 > 80 mg L–1 > 0 mg L–1. After 7 days at 50 mg L–1 GAs, total nitrogen (TN), NH 4 -N, NO 3 -N, and total phosphorous (TP) removal reached 85.97 %, 78.08 %, 86.59 %, and 94.39 %, respectively. Florfenicol, oxytetracycline hydrochloride, ofloxacin, and sulfamethoxazole removal efficiencies were 67.77 %, 98.29 %, 90.47 %, and 94.92 %, respectively. These findings highlight GAs' significant role in enhancing antibiotic and nutrient removal. [ABSTRACT FROM AUTHOR]

• A closed-loop system of fusel alcohol production and nutrient recycling. • 3.8 g/L of mixed fusel alcohols were produced from M. salina hydrolysates. • Cellular N and P remineralized from algae biomass was recovered as struvite. • Struvite was recycled for subsequent algae cultivation as the major N/P nutrient. Improving the economic feasibility is necessary for algae-based processes to achieve commercial scales for biofuels and bioproducts production. A closed-loop system for fusel alcohol production from microalgae biomass with integrated nutrient recycling was developed, which enables the reuse of nitrogen and phosphorus for downstream application and thus reduces the operational requirement for external major nutrients. Mixed fusel alcohols, primarily isobutanol and isopentanol were produced from Microchloropsis salina hydrolysates by an engineered E. coli co-culture. During the process, cellular nitrogen from microalgae biomass was converted into ammonium, whereas cellular phosphorus was liberated by an osmotic shock treatment. The formation of struvite from the liberated ammonium and phosphate, and the subsequent utilization of struvite to support M. salina cultivation was demonstrated. The closed loop system established here should help overcome one of the identified economic barriers to scale-up of microalgae production, and enhance the sustainability of microalgae-based chemical commodities production. [ABSTRACT FROM AUTHOR]

The intensive agricultural practices are increasing the demand for chemical fertilizers, being currently produced from a non-environmental friendly way. Besides the environmental impacts, the nutrient uptake efficiency by the crops is very low, representing huge losses into the fields. Therefore, it is crucial to study alternatives for the current chemical fertilizers, which simultaneous improve nutrient efficiency and minimize environmental impacts. A sustainable solution is to recover nutrients from wastewater streams with microalgal cultures and the biomass conversion into bio-char for soil amendment. Wastewaters are loaded with nitrogen and phosphorus and can be used as culture medium for microalgae. Thus, nutrients can be recycled, reducing the requirement of chemical fertilizers. This paper aims to review nutrient recovery from wastewater using microalgae and the biomass conversion into bio-char. This process promotes nutrient recycling and the bio-char (when added to soil) improves the nutrient uptake efficiency by crops. [ABSTRACT FROM AUTHOR]

Managing organic waste streams is a major challenge for the agricultural industry. Anaerobic digestion (AD) of organic wastes is a preferred option in the waste management hierarchy, as this process can generate renewable energy, reduce emissions from waste storage, and produce fertiliser material. However, Nitrate Vulnerable Zone legislation and seasonal restrictions can limit the use of digestate on agricultural land. In this paper we demonstrate the potential of cultivating microalgae on digestate as a feedstock, either directly after dilution, or indirectly from effluent remaining after biofertiliser extraction. Resultant microalgal biomass can then be used to produce livestock feed, biofuel or for higher value bio-products. The approach could mitigate for possible regional excesses, and substitute conventional high-impact products with bio-resources, enhancing sustainability within a circular economy. Recycling nutrients from digestate with algal technology is at an early stage. We present and discuss challenges and opportunities associated with developing this new technology. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is an established technology to produce renewable energy as methane-rich biogas for which microalgae are a suitable substrate. Besides biogas production, anaerobic digestion of microalgae generates an effluent rich in nutrients, so-called digestate, that can be used as a growth medium for microalgal cultures, with the potential for a closed nutrient loop and sustainable bioenergy facility. In this study, the methane potential and nutrient mobilization of the microalga Scenedemus dimorphus was evaluated under continuous conditions. The suitability of using the digestate as culture medium was also evaluated. The results show that S. dimorphus is a suitable substrate for anaerobic digestion with an average methane yield of 199 mL g −1 VS. The low level of phosphorus in digestate did not limit algae growth when used as culture medium. The potential of liquid digestate as a superior culture medium rather than inorganic medium was demonstrated. [ABSTRACT FROM AUTHOR]

A novel eco-engineered mixed anaerobic culture was successfully demonstrated for the first time to be capable of continuous regeneration in nutrient limiting conditions. Microbial catabolism has been found to support a closed system of nutrients able to enrich a culture of lithotrophic methanogens and provide microbial cell recycling. After enrichment, the hydrogenotrophic species was the dominating methanogens while a bacterial substratum was responsible for the redistribution of nutrients. q-PCR results indicated that 7% of the total population was responsible for the direct conversion of the gases. The efficiency of H 2 /CO 2 conversion to CH 4 reached 100% at a gassing rate of above 60 v/v/d. The pH of the culture media was effectively sustained at optimal levels (pH 7–8) through a buffering system created by the dissolved CO 2 . The novel approach can reduce the process nutrient/metal requirement and enhance the environmental and financial performance of hydrogenotrophic methanogenesis for renewable energy storage. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine if polycultures of algae could enhance tolerance to aqueous-phase coproduct (ACP) from hydrothermal liquefaction (HTL) of algal biomass to produce biocrude. The growth of algal monocultures and polycultures was characterized across a range ACP concentrations and sources. All of the monocultures were either killed or inhibited by 2% ACP, but polycultures of the same species were viable at up to 10%. The addition of ACP increased the growth rate (up to 25%) and biomass production (53%) of polycultures, several of which were more productive in ACP than any monoculture was in the presence or absence of ACP. These results suggest that a cultivation process that applies biodiversity to nutrient recycling could produce more algae with less fertilizer consumption. [ABSTRACT FROM AUTHOR]

The suitability of crude and purified struvite (MgNH 4 PO 4 ), a major precipitate in wastewater streams, was investigated for renewable replacement of conventional nitrogen and phosphate resources for cultivation of microalgae. Bovine effluent wastewater stone, the source of crude struvite, was characterized for soluble N/P, trace metals, and biochemical components and compared to the purified mineral. Cultivation trials using struvite as a major nutrient source were conducted using two microalgae production strains, Nannochloropsis salina and Phaeodactylum tricornutum , in both lab and outdoor pilot-scale raceways in a variety of seasonal conditions. Both crude and purified struvite-based media were found to result in biomass productivities at least as high as established media formulations (maximum outdoor co-culture yield ∼20 ± 4 g AFDW/m 2 /day). Analysis of nutrient uptake by the alga suggest that struvite provides increased nutrient utilization efficiency, and that crude struvite satisfies the trace metals requirement and results in increased pigment productivity for both microalgae strains. [ABSTRACT FROM AUTHOR]

Despite environmental benefits of algal-biofuels, the energy-intensive systems for producing microalgae-feedstock may result in high GHG emissions. Trying to overcome energy-costs, this research analyzed the biodiesel production system via dry-route, based on Chlorella vulgaris cultivated in raceways, by comparing the GHG-footprints of diverse microalgae-biodiesel scenarios. These involved: the single system of biomass production (C0); the application of pyrolysis on the residual microalgal biomass (cake) from the oil extraction process (C1); the same as C0, with anaerobic cake co-digested with cattle manure (C2); the same conditions as in C1 and C2, by integrating in both cases (respectively C3 and C4), the microalgae cultivation with an autonomous ethanol distillery. The reduction of GHG emissions in scenarios with no such integration (C1 and C2), compared to CO, was insignificant (0.53% and 4.67%, respectively), whereas in the scenarios with integration with ethanol production system, the improvements were 53.57% for C3 and 63.84% for C4. [ABSTRACT FROM AUTHOR]

The chemical absorption of carbon dioxide (CO 2 ) is a technique used for the mitigation of the greenhouse effect. However, this process consumes high amounts of energy to regenerate the absorbent and to separate the CO 2 . CO 2 removal by microalgae can be obtained via the photosynthesis process. The objective of this study was to investigate the cultivation and the macromolecules production by Spirulina sp. LEB 18 with the addition of monoethanolamine (MEA) and CO 2 . In the cultivation with MEA, were obtained higher results of specific growth rate, biomass productivity, CO 2 biofixation, CO 2 use efficiency, and lower generation time. Besides this, the carbohydrate concentration obtained at the end of this assay was approximately 96.0% higher than the control assay. Therefore, Spirulina can be produced using medium recycle and the addition of MEA, thereby promoting the reduction of CO 2 emissions and showing potential for areas that require higher concentrations of carbohydrates, such as in bioethanol production. [ABSTRACT FROM AUTHOR]

In this study, the reuse of nitrogen from fuel-extracted algal residues was investigated. The alga Scenedesmus acutus was found to be able to assimilate nitrogen contained in amino acids, yeast extracts, and proteinaceous alga residuals. Moreover, these alternative nitrogen resources could replace nitrate in culturing media. The ability of S. acutus to utilize the nitrogen remaining in processed algal biomass was unique among the promising biofuel strains tested. This alga was leveraged in a recycling approach where nitrogen is recovered from algal biomass residuals that remain after lipids are extracted and carbohydrates are fermented to ethanol. The protein-rich residuals not only provided an effective nitrogen resource, but also contributed to a carbon “heterotrophic boost” in subsequent culturing, improving overall biomass and lipid yields relative to the control medium with only nitrate. Prior treatment of the algal residues with Diaion HP20 resin was required to remove compounds inhibitory to algal growth. [ABSTRACT FROM AUTHOR]

To reduce wastes and the costs of microbial lipid production, it is imperative to recycle resources, including spent cell mass, mineral nutrients and water. In the present study, lipid production by the oleaginous yeast Rhodosporidium toruloides was used as a model system to demonstrate resources recycling. It was found that the hydrolysates of spent cell mass were good media to support cell growth of various oleaginous yeasts. When serial repitching experiments were performed using 70 g/L glucose and the hydrolysates alone as nutrients, it produced 16.6, 14.6 and 12.9 g/L lipids, for three successive cycles, while lipid titre remained almost constant when spent water was also recycled. The cell mass hydrolysates could be used as equivalents to the mixture of yeast extract and peptone to support lipid production from corn stalk hydrolysates. Our results showed efficient recycling of lipid production wastes and should be helpful to advance microbial lipid technology. [ABSTRACT FROM AUTHOR]

Highlights: [•] Direct field emissions from organic fertilizer dominated environmental impacts. [•] The amount of avoided mineral fertilizers largely influenced environmental impacts. [•] Modified plant available nitrogen calculation considers total nitrogen emissions. [•] Calculation method for amount of avoided mineral fertilizers. [ABSTRACT FROM AUTHOR]

• A novel bioprocess is proposed for municipal wastewater treatment. • Sewage treatment can be with positive financial output. • Nutrients can be effectively recovered. • Recovering methane from effluent of AnMBR is important and feasible. • Much less excess sludge production can be achieved. Conventional sewage treatment applying activated sludge processes is energy-intensive and requires great financial input, hampering widespread implementation. The introduction of anaerobic membrane bioreactors (AnMBR) followed by an algal reactor growing species of commercial interest, may present an alternative, contributing to the envisaged resource recovery at sewage treatment plants. AnMBRs can be applied for organic matter removal with energy self-sufficiency, provided that effective membrane fouling management is applied. Haematococcus pluvialis , an algal species with commercial value, can be selected for ammonium and phosphate removal. Theoretical analysis showed that good pollutant removal, positive financial output, as well as a significant reduction in the amount of hazardous activated sludge can be achieved by applying the proposed process, showing interesting advantages over current sewage treatment processes. Microbial contamination to H. pluvialis is a challenge, and technologies for preventing the contamination during continuous sewage treatment need to be applied. [ABSTRACT FROM AUTHOR]

Abstract: In this study, an upper limit in the solar energy conversion efficiency which can be translated to a maximum potential algal yield of a large-scale culture is calculated based on the algal productivity model in which light and nutrient are made the growth rate limiting factors, and taking the design characteristics of the cultivation system into account. Our results indicate that for the production of low-cost biodiesel within the limits of the wastewater quality standards, that the culturing of high lipid content algae within a raceway pond would provide an appropriate solution for manufacturing biodiesel from algae. However, due to inefficient sunlight utilization and due to the large amount of fertilizer required in raceway ponds, a greater effluent recycle rate would have to be implemented to reduce the amount of fertilizer discharge to meet the wastewater quality standards and to maximize the attainable productivity of algal biomass. [Copyright &y& Elsevier]

Abstract: Chlorella vulgaris, Spirulina platensis and Saccharina latissima were processed under supercritical water gasification conditions at 500°C, 36MPa in an Inconel batch reactor for 30min in the presence/absence of NaOH and/or Ni–Al2O3. Hydrogen gas yields were more than two times higher in the presence of NaOH than in its absence and tar yields were reduced by up to 71%. Saccharina, a carbohydrate-rich macro-alga, gave the highest hydrogen gas yields of 15.1mol/kg. The tars from all three algae contained aromatic compounds, including phenols, alkyl benzenes and polycyclic aromatic hydrocarbons as well as heterocyclic nitrogen compounds. Tars from Chlorella and Spirulina contained high yields of pyridines, pyrroles, indoles and pyrimidines. Up to 97% TOC removal were achieved in the process waters from the gasification of the algae. Analyses for specific nutrients in the process waters indicated that the process waters from Saccharina could potentially be used for microalgae cultivation. [Copyright &y& Elsevier]

This study investigated the feasibility of using recovered nutrients from hydrothermal carbonization (HTC) for cultivation of microalga Chlorella vulgaris . Different dilution multiples of 50, 100 and 200 were applied to the recycled process water from HTC and algal growth was compared among these media and a standard growth medium BG-11. Algae achieved a biomass concentration of 0.79 g/L on 50× process water after 4 days. Algae removed total nitrogen, total phosphorus and chemical oxygen demand by 45.5–59.9%, 85.8–94.6% and 50.0–60.9%, respectively, on differently diluted process water. The fatty acid methyl ester yields for algae grown on the process water were 11.2% (50×), 11.2% (100×) and 9.7% (200×), which were significantly higher than 4.5% for BG-11. In addition, algae cultivated on process water had 18.9% higher carbon and 7.8% lower nitrogen contents than those on BG-11, indicating that they are very suitable as biofuel feedstocks. [ABSTRACT FROM AUTHOR]

Abstract: The life cycle impacts were assessed for an integrated microalgal biodiesel production system that facilitates energy- and nutrient- recovery through anaerobic digestion, and utilizes glycerol generated within the facility for additional heterotrophic biodiesel production. Results show that when external fossil energy inputs are lowered through process integration, the energy demand, global warming potential (GWP), and process water demand decrease significantly and become less sensitive to algal lipid content. When substitution allocation is used to assign additional credit for avoidance of fossil energy use (through utilization of recycled nutrients and biogas), GWP and water demand can, in fact, increase with increase in lipid content. Relative to stand-alone algal biofuel facilities, energy demand can be lowered by 3–14GJper ton of biodiesel through process integration. GWP of biodiesel from the integrated system can be lowered by up to 71% compared to petroleum fuel. Evaporative water loss was the primary water demand driver. [Copyright &y& Elsevier]

Abstract: One of the common tendencies of animal production activities in Europe and in developed countries in general is to intensify the animal production and to increase the size of the animal production units. High livestock density is always accompanied by production of a surplus of animal manure, representing a considerable pollution threat for the environment in these areas. Avoiding over-fertilization is not only important for environmental protection reasons but also for economical reasons. Intensive animal production areas need therefore suitable manure management, aiming to export and to redistribute the excess of nutrients from manure and to optimize their recycling. Anaerobic digestion of animal manure and slurries offers several benefits by improving their fertilizer qualities, reducing odors and pathogens and producing a renewable fuel – the biogas. The EU policies concerning renewable energy systems (RES) have set forward a fixed goal of supplying 20% of the European energy demands from RES by year 2020. A major part of the renewable energy will originate from European farming and forestry. At least 25% of all bioenergy in the future can originate from biogas, produced from wet organic materials such as: animal manure, whole crop silages, wet food and feed wastes, etc. [Copyright &y& Elsevier]

No efficient, reliable, and scale independent disinfection methods for toilet waste are available today for safe recycling of plant nutrients. Therefore, two chemical treatment methods, addition of urea or of PAA (a quaternary mixture of 15% peracetic acid, 15% hydrogen peroxide and 30% acetic acid), were evaluated for disinfection of faecal matter.Degradation of the added urea resulted in 30 g of ammonia nitrogen per kilogram of treated matter and a pH increase to approximately 9.3. This produced an efficient disinfection of E. coli, Enterococcus spp., and Salmonella spp. within 3 weeks (>6log10 reduction) and a reduction of the chemical resistant Salmonella typhimurium 28b phage, corresponding to a decimal reduction within 7.5 days. No viable Ascaris suum eggs were found after 50 days of treatment. No reduction of spore forming Clostridia spp. was observed. Urea treatment proved to be efficient for disinfection of source separated faecal matter in a scale independent method used for safe recycling of nutrients found in the faecal matter.PAA reduced all of the above indicator organisms within 12 h after application. For this faecal material, with a dry matter content of approximately 10%, an addition of 0.5–1% of PAA (active substance, corresponding to 3.3–6.7% of the Proxitane® 15 used) was required before no viable organisms were found in the material. However, this was not tested for the A. suum. No viable spore-forming bacteria or phages were detected. A high rate of bacteria regrowth occurred at 0.15% dosage and 5 days of treatment. PAA is an efficient alternative for disinfection of separated faeces if a rapid treatment is needed. [Copyright &y& Elsevier]

A fixed-film (biofilm) reactor was designed and its performance was determined at various retention times. The goal was to find the optimal retention time for recycling plant nutrients in an advanced life support system, to minimize the size, mass, and volume (hold-up) of a production model. The prototype reactor was tested with aqueous leachate from wheat crop residue at 24, 12, 6, and 3 h hydraulic retention times (HRTs). Biochemical oxygen demand (BOD), nitrates and other plant nutrients, carbohydrates, total phenolics, and microbial counts were monitored to characterize reactor performance. BOD removal decreased significantly from 92% at the 24 h HRT to 73% at 3 h. Removal of phenolics was 62% at the 24 h retention time, but 37% at 3 h. Dissolved oxygen concentrations, nitric acid consumption, and calcium and magnesium removals were also affected by HRT. Carbohydrate removals, carbon dioxide (CO2) productions, denitrification, potassium concentrations, and microbial counts were not affected by different retention times. A 6 h HRT will be used in future studies to determine the suitability of the bioreactor effluent for hydroponic plant production. [Copyright &y& Elsevier]