Recycling of wastes from fish beneficiation by composting: chemical characteristics of the compost and efficiency of their humic acids in stimulating the growth of lettuce

Application of an organic-mineral biocomposite for sustainable remediation of post-industrial soil contaminated with potentially toxic elements (PTEs)

Numerous technological innovations have been developed for managing post-industrial soils, but assisted phytostabilization-a sustainable and environmentally friendly approach-has attracted significant global interest. This study evaluates the effectiveness of a novel biocomposite, composed of fish waste compost and chalcedonite, in assisting the phytostabilization of soil contaminated with potentially toxic elements (PTEs), using Lolium perenne L. (perennial ryegrass) as a test plant. The results demonstrated that the biocomposite significantly increased soil pH (by 0.19 units), organic carbon content (by 174.3%), improving soil fertility by increasing nutrient availability (available P by 219.6%, and available K by 146.9%), and plant growth. Additionally, it promoted PTE accumulation in the roots while reducing Pb (44%), Zn (24%), Cu (23%), and Ni (14%) concentrations in the aerial parts, as well as Cd (71%), Ni (33%), and Cu (29%) levels in the soil. The biocomposite also altered the fractionation of PTEs, reducing their mobility and bioavailability. Specifically, it decreased the exchangeable fraction (F1) by 45% for Cu, 71% for Cd, 41% for Pb, and 24% for Zn, effectively limiting their environmental risk. Moreover, it promoted the redistribution of Pb and Zn into the reducible fraction (F2), Cu and Pb into the oxidizable fraction (F3), and Cu, Ni, and Cd into the residual fraction (F4), indicating enhanced stabilization. The highest immobilization efficiencies were observed for Cd (53.9%) and Pb (52.3%), confirming the biocomposite's effectiveness in reducing PTE mobility. These findings highlight the potential of biocomposite amendments in remediating PTE-contaminated soil by improving soil physicochemical properties, reducing PTE bioavailability, and enhancing phytostabilization efficiency. This approach supports sustainable waste valorization and circular economy principles, offering a promising strategy for rehabilitating post-industrial lands with high PTE contamination.

Organic fertilizer type and dose affect growth, morphological and physiological parameters, and mineral nutrition of watermelon seedlings

Background

Organic agriculture has grown rapidly in recent years due to its environmental friendliness, sustainability, and improved farm profitability. Transplants are commonly used for fruits and vegetables to achieve consistent quality, uniformity, and easy field spacing control. The efficacy and optimal amounts of fertilizers for organic transplant production need to be investigated.

Methods

The effects of three organic fertilizers (Sustane 4-6-4, Nature Safe 7-7-7, and Dramatic 2-4-1) and one conventional fertilizer Peters Professional 20-20-20 (Conventional) with four doses (nitrogen (N) content was matched among fertilizers in each level, as 0.14 g/L, 0.28 g/L, 0.56 g/L, and 0.84 g/L N, respectively) on watermelon seedlings were compared in this study.

Results

The results showed that all organic fertilizer treatments were not significantly different from the Conventional group in terms of watermelon germination. The only exception was the highest dose of Sustane 4-6-4 (0.84 g/L N) which decreased the germination rate and relative emergence index. Generally, growth index, shoot fresh and dry weights, true leaf number, and stem diameter increased as the amount of N increased within each fertilizer type. The best shoot growth was observed in the highest doses of Conventional and Dramatic 2-4-1 treatments (0.84 g/L N). However, Dramatic 2-4-1 treatments resulted in the lowest root growth when compared to other fertilizers at the same N dose. The second highest fertilization dose (0.56 g/L N) of Sustane 4-6-4 had the best root growth according to root fresh weight, root volume, root area, total root length, as well as the numbers of root tip and crossing when compared to other treatments. For seedlings, a well-developed root system can ensure a good seedling establishment and high survival rate under stressful field conditions after transplanting. Thus, Sustane 4-6-4 at 14 g/L (0.56 g/L N) is recommended to produce high-quality organic watermelon seedlings among the treatments applied in this study.

Nutrient recovery and recycling from fishery waste and by-products

The circular bio-based economy offers great untapped potential for the food industry as possible valuable products and energy can be recovered from food waste. This can promote more sustainable and resilient food systems in Europe in follow-up of the European Commission's Farm to Fork strategy and support the global transition to more sustainable agri-food systems with the common agricultural and fisheries policies. With its high nutrient content, waste and by-products originating from fish and seafood industry (including aquaculture) are one of the most promising candidates to produce alternative fertilising products which can play a crucial role to replace synthetic mineral fertilisers. Whereas several studies highlighted the opportunities to recover valuable compounds from fishery waste, study towards their potential for the production of fertilising products is still scarce. This study presents an extensive overview of the characteristics of fishery waste and by-products (i.e., fish processing waste, fish sludge, seafood waste/by-products), the state-of-the-art nutrient recovery technologies and recovered nutrients as fertilising products from these waste streams. The European Commission has already adopted a revised Fertilising Products Regulation (EU) 2019/1009 providing opportunities for fertilising products from various bio-based origins. In frame of this opportunity, we address the quality and safety aspects of the fishery waste-derived fertilising products under these criteria and highlight possible obstacles on their way to the market in the future. Considering its high nutrient content and vast abundance, fish sludge has a great potential but should be treated/refined before being applied to soil. In addition to the parameters currently regulated, it is crucial to consider the salinity levels of such fertilising products as well as the possible presence of other micropollutants especially microplastics to warrant their safe use in agriculture. The agronomic performance of fishery waste-derived fertilisers is also compiled and reported in the last section of this review paper, which in most cases perform equally to that of conventional synthetic fertilisers.

Phosphorus recovery from wastewater and bio-based waste: an overview

Phosphorus is one of the most important macronutrients needed for the growth of plants. The fertilizer production market uses 80% of natural, non-renewable phosphorus resources in the form of phosphate rock. The depletion of those deposits forces a search for other alternatives, including biological waste. This review aims to indicate the most important ways to recover phosphorus from biowaste, with particular emphasis on wastewater, sewage sludge, manure, slaughter or food waste. A comparison of utilized methods and directions for future research based on the latest research is presented. Combining biological, chemical, and physical methods with thermal treatment appears to be the most effective way for the treatment of wastewater sludge in terms of phosphorus recovery. Hydrothermal, thermochemical, and adsorption on thermally treated adsorbents are characterized by a high phosphorus recovery rate (over 95%). For animal by-products and other biological waste, chemical methods seems to be the most optimal solution with a recovery rate over 96%. Due to its large volume and relatively low phosphorus content, wastewater is a resource that requires additional treatment to recover the highest possible amount of phosphorus. Pretreatment of wastewater with combined methods seems to be a possible way to improve phosphorus recovery. A compressive evaluation of combined methods is crucial for future research in this area.

The challenges and perspectives for anaerobic digestion of animal waste and fertilizer application of the digestate

The increase in livestock production creates a serious problem of managing animal waste and by-products. Among the wide range of waste valorization methods available, anaerobic digestion is very promising. It is a form of material recycling that also produces renewable energy in the form of biogas, which is reminiscent of energy recycling. The effluent and digestate from the anaerobic digestion process need to be processed further. These materials are widely used in agriculture due to their composition. Both the liquid and solid fractions of digestate are high in nitrogen, making them a valuable source for plants. Before soil or foliar application, conditioning (e.g., with inorganic acids) and neutralization (e.g., with potassium hydroxide) is required to eliminate odorous compounds and microorganisms. Various methods of conducting the process by anaerobic digestion (use of additives increasing activity of microorganisms, co-digestion, multiple techniques of substrate preparation) and the possibility of controlling process parameters such as optimal C/N ratio (15-30), optimal temperature (psychrophilic (<20 °C), mesophilic (35-37 °C) and thermophilic (55 °C) for microorganism activity ensure high efficiency of the process. Literature data describing tests of various digestates on different plants prove high efficiency, determined by yield increase (even by 28%), nitrogen uptake (by 20%) or phosphorus recovery rate (by 43%) or increase of biometric parameters (e.g., leaf area).

Fish and fish waste-based fertilizers in organic farming - With status in Norway: A review

This paper reviews relevant knowledge about the production and uses of fertilizers from fish and fish waste (FW) that may be applicable for certified organic farming, with a focus on crop and horticultural plants. Fish industries generate a substantial amount of FW. Depending on the level of processing or type of fish, 30-70% of the original fish is FW. Circular economy and organic farming concepts were used to evaluate the potential of production of fertilizers from captured fish. Fertilizers produced from captured fish promote the recycling of nutrients from the sea and back to terrestrial environments. Nutritional composition of FW is assessed to determine the potential to supply plant nutrients such as nitrogen, or a combination of nitrogen and phosphorous, or to enrich a compost. Methods used in processing of FW to produce fish- emulsion, fish hydrolysate/fish silage, fish-compost and digestate from anaerobic digestion/co-digestion are presented. Using information about commercially available fish-based fertilizers listed by the Organic Materials Review Institute (OMRI), we present a scenario for establishing fish/FW-based fertilizers industry and research in Europe. With Norway's 9th position among top ten global capture producers and focus in Norway on developing organic farming, we brief how FW is currently utilized and regulated, and discuss its availability for possible production of FW-based organic fertilizers. The amount of FW available in Norway for production of fertilizers may facilitate the establishment of an industrial product that can replace the currently common use of dried poultry manure from conventional farming in organic farming.

Agricultural waste

The management of agricultural waste has become very important because the inappropriate disposal yields negative effects on the environment. The resource recovery from agricultural waste which converts waste into available resources can reduce the waste and new resource consumption. This review summarizes the 2018 researches of over three hundred scholar papers from several aspects: agricultural waste, and, waste chemical characterization, agricultural waste material, adsorption, waste energy, composting, waste biogas, agricultural waste management, and others.

The use of coal fly ash and vinegar residue as additives in the two-stage composting of green waste

Composting is an attractive way to recycle organic wastes because the product (compost) can be used as an organic fertilizer or a culture substrate. This study assessed coal fly ash (CFA; at 0, 15, and 35%) and/or vinegar residue (VR; at 0, 35, and 55%) as additives in the green waste (GW) composting process. Compost maturity was assessed based on the following indicators: water-holding capacity, pH, total organic carbon, electrical conductivity, total Kjeldahl nitrogen, and germination index. Other important compost properties that were determined included germination percentage and root length of seeds in a germination assay, crude fiber degradation, specific UV absorption, E₄/E₆ ratio, microbial numbers (culturable bacteria and volatile fatty acid-degrading bacteria), enzyme activities (dehydrogenase, β-glucosidase, acid-phosphatase, urease, and ortho-diphenol oxidase), and available nutrients. When added together, CFA and VR improved all of these properties. As indicated by the maturity indicators and other properties, the best treatment (the combined addition of 15% CFA and 55% VR) required only 23 days to produce a mature and high quality compost.

Zinc, copper, and oxysterol levels in patients with type 1 and type 2 diabetes mellitus

BACKGROUND

The present study has the objective to assess the zinc (Zn), copper (Cu), and oxysterols plasma levels in type 1 (DM1) (n = 26) and type 2 (DM2) (n = 80) diabetes patients, as compared to healthy controls (n = 71), in order to testify whether metal levels may have a significant impact on the association between oxysterols and diabetes.

METHODS

Plasma trace elements and plasma oxysterols were assessed using atomic absorption spectrometry and LC-MS/MS, respectively. Lifestyle, smoking status, alcohol intake, and drug usage, as well as microvascular complications, were also monitored and reported.

RESULTS

The obtained data demonstrated that both DM1 and DM2 patients were characterized by significantly elevated HbA1c, FBG, TC, LDL-C, VLDL-C, and TG levels as compared to controls. Plasma Zn levels and Zn/Cu ratio in DM1 and DM2 patients were about 3- and 2-fold lower than controls. No significant differences in plasma Cu levels were reported. The 7-ketocholesterol (7-kchol) levels in DM1 and DM2 patients exceeded these values in healthy individuals by 2.5 and 5-fold, respectively. Similarly, cholestan-3β, 5α, 6β-triol (chol-triol) levels were more than 3- and 6-fold higher when compared to the respective values in non-diabetic controls. In regression models decreased plasma Zn and elevated oxysterol levels were significantly associated with HbA1c and fasting plasma glucose levels, after adjustment for anthropometric and clinical variables, as well as routine biochemical markers.

CONCLUSIONS

Plasma Zn concentration is inversely associated with both 7-kchol and chol-triol levels. Assessment of Zn and oxysterol levels may be used both for risk assessment and as targets for the treatment of diabetes mellitus.