Slurry Solid Fraction Research Articles

Nutrient Potential Leachability in a Sandy Soil Amended with Manure-Based Fertilisers

The application of manure-based fertilisers (MBFs) is considered an important practice for achieving agricultural sustainability. However, the potential losses of nutrients to the environment need to be thoroughly evaluated. This study aimed to assess nutrients’ potential leachability from a sandy soil, fertilised with MBFs produced by mixing manure from one single animal species with N- or P-mineral fertilisers, to achieve target N:P ratios (1:1, 2:1 and 0.5:1). MBFs were prepared by combining pig slurry, cattle slurry or poultry manure with N- and P-mineral fertilisers, or slurry-derived materials, obtained by solid–liquid separation. A leaching experiment was set-up in soil columns treated with MBFs, for 59 days, with seven leaching events. Poultry manure application to soil led to higher potential N leaching, while pig slurry induced higher P leaching. All 2:1 MBFs decreased P leaching, relative to the original manure, with the higher reduction (52%) being observed for pig slurry with urea. The addition of urea to poultry manure also diminished its potential for N leaching. The behaviour of P-enriched materials, pig slurry solid fraction and both 0.5:1 MBFs obtained with phosphoric acid addition showed a higher risk of P leaching, while the use of superphosphate as a P-mineral source decreased the risk of P leaching. Concluding, it is possible to use specific MBFs, enriched with N and P from mineral sources, and have lower N and P leaching potential, reducing the risks associated with manure soil application, while increasing their interest as alternative fertilisers.

Valorization of Pineapple Leaves Waste for the Production of Bioethanol.

Being a lignocellulose-rich biomass, pineapple leaves waste (PL) could be a potential raw material for the production of biofuel, biochemicals, and other value-added products. The main aim of this study was to investigate the potential of pineapple leaves in the sustainable production of bioethanol via stepwise saccharification and fermentation. For this purpose, PL was subjected to hydrothermal pretreatment in a high-pressure reactor at 150 °C for 20 min without any catalyst, resulting in a maximum reducing sugar yield of 38.1 g/L in the liquid fraction after solid-liquid separation of the pretreated hydrolysate. Inhibitors (phenolics, furans) and oligomers production were also monitored during the pretreatment in the liquid fraction of pretreated PL. Enzymatic hydrolysis (EH) of both pretreated biomass slurry and cellulose-rich solid fraction maintained at a solid loading (dry basis) of 5% wt. was performed at 50 °C and 150 rpm using commercial cellulase at an enzyme dose of 10 FPU/gds. EH resulted in a glucose yield of 13.7 and 18.4 g/L from pretreated slurry and solid fractions, respectively. Fermentation of the sugar syrup obtained by EH of pretreated slurry and the solid fraction was performed at 30 °C for 72 h using Saccharomyces cerevisiae WLP300, resulting in significant ethanol production with more than 91% fermentation efficiency. This study reveals the potential of pineapple leaves waste for biorefinery application, and the role of inhibitors in the overall efficiency of the process when using whole biomass slurry as a substrate.

Impact of organic soil amendments in antibiotic levels, antibiotic resistance gene loads, and microbiome composition in corn fields and crops

The potential spreading of antibiotic resistance genes (ARG) into agricultural fields and crops represent a fundamental limitation on the use of organic fertilization in food production systems. We present here a study of the effect of spreading four types of organic soil amendments (raw pig slurry, liquid and solid fractions, and a digested derivative) on demonstrative plots in two consecutive productive cycles of corn harvest (Zea mays), using a mineral fertilizer as a control, following the application of organic amendments at 32–62 T per ha (150 kg total N/ha) and allowing 5–8 months between fertilization and harvest. A combination of qPCR and high-throughput 16S rDNA sequencing methods showed a small, but significant impact of the fertilizers in both ARG loads and microbiomes in soil samples, particularly after the second harvesting cycle. The slurry solid fraction showed the largest impact on both ARG loads and microbiome variation, whereas its digestion derivatives showed a much smaller impact. Soil samples with the highest ARG loads also presented increased levels of tetracyclines, indicating a potential dual hazard by ARG and antibiotic residues linked to some organic amendments. Unlike soils, no accumulation of ARG or antibiotics was observed in corn leaves (used as fodder) or grains, and no grain sample reached detection limits for neither parameter. These results support the use of organic soil amendments in corn crops, while proposing the reduction of the loads of ARGs and antibiotics from the fertilizers to greatly reduce their potential risk.

Co-Composting of Brewers’ Spent Grain with Animal Manures and Wheat Straw: Influence of Two Composting Strategies on Compost Quality

The main challenge of this work is to identify a novel approach to reuse and valorize brewers’ spent grain (BSG) to produce a new source of income for the brewers in terms of self-consumption or selling goods. Therefore, this study explored the composting behavior of BSG mixed with different organic materials: wheat straw with pig slurry solid fraction and wheat straw with sheep manure, MIX1 and MIX2, respectively. The composting process was carried out in bins by comparing two different composting strategies: manual turning (MT) and static composting xxx– without turning operations (ST). During the experimental trial, BSG mixtures were chemically analyzed for pH, total Kjeldahl nitrogen, ammoniacal nitrogen, nitrate-nitrogen, total organic carbon, volatile solids, carbon to nitrogen ratio, and moisture content. Furthermore, the final composted materials were evaluated according to the physicochemical and biological limits fixed by the European regulation (2019/1009) and the Italian law (D.Lgs 75/2010). At the end of the composting process, the C/N ratio ranged from 11.6 to 15.5, the humification ratio ranged from 12.4 to 13.8 and the NH4+-N/NO3−-N ratio was lower than 0.5 indicating, in all investigated treatments, a good degree of maturation. However, as evidenced by the high pH values and low Germination Index, the sheep manure, as starting material, proved less effective than the solid fraction of pig slurry, probably due to excessive trampling and slow litter change. Finally, concerning the two composting strategies investigated, the obtained results highlighted that the composting strategy did not affect the final compost quality.

Acidified Animal Manure Products Combined with a Nitrification Inhibitor Can Serve as a Starter Fertilizer for Maize

There is an urgent need for better management practices regarding livestock farm nutrient imbalances and for finding alternatives to the actual use of mineral fertilizers. Acidification of animal manure is a mitigation practice used to reduce ammonia emissions to the atmospheric environment during manure storage and land application. Acidification modifies manure physicochemical characteristics, among which soluble N and P significantly increase. The main objective of this study was to investigate if acidification and the addition of a nitrification inhibitor to manure and placement of the treated manure close to the seed can stimulate maize growth by enhancing nutrient availability, specially P and consequently plant P uptake, at early development stages without the use of mineral N and P as a starter fertilizer. Raw dairy slurry and solid fractions from dairy slurry and digestate from a biogas plant were acidified to pH 5.5 and applied with or without a nitrification inhibitor (DMPP, 3,4-dimethyl pyrazole phosphate) to maize in a pot experiment, where biomass productivity, nutrient uptake and soil P availability were examined. Acidification increased the water-extractable P fraction of all slurry and digestate organic residues (by 20–61% of total P) and consequently plant P uptake from solid fractions of both slurry and digestate compared to the untreated products (by 47–49%). However, higher plant biomass from acidification alone was only achieved for the slurry solid fraction, while the combination of acidification and DMPP also increased plant biomass in the digestate solids treatment (by 49%). We therefore conclude that the combination of acidification and a nitrification inhibitor can increase the starter fertilizer value of slurry and digestate products sufficiently to make them suitable as a maize starter fertilizer.

Development of a sustainable bioprocess based on green technologies for xylitol production from corn cob

In this work, a sustainable and environmental friendly strategy for the biotechnological production of xylitol was proposed and optimized. For this purpose, corn cob was hydrothermally pretreated at high solid loadings (25%) for an efficient solubilization of xylan in hemicellulose derived compounds, xylooligosaccharides and xylose. Xylose enriched streams were obtained from the enzymatic saccharification of the whole slurry (solid and liquid fraction) resulting from the autohydrolysis pretreatment. The xylitol production in a simultaneous saccharification and fermentation (SSF) process, by the recombinant Saccharomyces cerevisiae PE-2-GRE3 strain, was optimized using different enzyme and substrate (pretreated corn cob solid) loadings by an experimental design. This study demonstrated a significant effect of substrate loading on the production process achieving a maximal concentration of 47 g/L with 6.7 % of pretreated corn cob and 24 FPU/g of enzyme loading, with partial detoxification of the hydrolysate. Furthermore, the 1.42-fold increase in xylitol titer and 1.56-fold increase in productivity achieved in a SSF using an acetic acid free-hydrolysate evidenced the negative effect of acetic acid on the yeast-based xylitol production process. The combination of these green technologies and the optimization of the proposed strategy enhanced the overall xylitol production through the valorization of corn cob.

Veterinary pharmaceuticals and antibiotics in manure and slurry and their fate in amended agricultural soils: Findings from an experimental field site (Baix Empordà, NE Catalonia)

The fate and transport of 34 veterinary pharmaceuticals (PhACs) is investigated in swine slurry and dairy cattle manure-amended agricultural soils, from an experimental field site, by using both analytical and modelled data. Potential differences on PhACs fate, attributed to the application of distinct swine slurry fractions (total, solid, and liquid), are herein assessed for the first time. Surface and deep soil layers, up to a depth of 120 cm, were analyzed at different periods after an annual fertilization event. Using input data representing typical agricultural soil conditions and the PhACs concentration measured in organic fertilizers the transport of these pollutants was modelled for a period of 10 years, including the monitored annual fertilization event. Fluoroquinolone, tetracycline and pleuromutilin antibiotics, together with anti-helmintics and analgesic and anti-inflammatories, were detected in manure-amended soils, at average concentrations ranging from 0.078 to 150 μg/kg dw in surface layers, with the highest levels found in the fields fertilized with the swine slurry solid fraction. Even though severe disagreements were observed between experimental and simulated PhACs concentrations along the soil column, both approaches pointed out that target compounds strongly adsorb onto surface layers, showing limited mobility along the soil profile. Thus, repeated manure and slurry fertilizations will contribute in building up persistent PhACs residues in the uppermost layers of the soil, while leaching will be a minor process governing their fate towards the subsurface. The ecotoxicological risks posed by the occurrence of PhACs in soils were estimated to be low for terrestrial organisms. Nevertheless the antibiotic enrofloxacin showed some potential to induce negative effects to crops.

Gaseous Emissions after Soil Application of Pellet Made from Composted Pig Slurry Solid Fraction: Effect of Application Method and Pellet Diameter

The study aimed at determining ammonia and GHG emissions from soil fertilized with pellets made from composted pig slurry solid fraction and to evaluate the effects of pellet diameter and pellet application method on gaseous emissions. A laboratory scale experiment was carried out investigating two composts: pig slurry solid fraction compost (SSFC) and pig slurry solid fraction mixed with wood chips compost (WCC). The two composts were pelettized in two different diameters—6 and 8 mm—by means of mechanical pelletizer. In total, eight fertilized treatments plus one unfertilized control were included in the experiment. The investigated pellets were applied at the same nitrogen rate (equivalent to 200 kg ha−1) using two different methods (on soil surface and incorporated into the soil). Ammonia (NH3) emission was monitored immediately after pellet application, while nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) were measured on a 57-day incubation period. As expected, ammonia volatilization was not detected from any of the treatments investigated. At the end of the experiment, the cumulative amounts of N2O, CO2 and CH4 ranged from 2.70 mg N-N2O m−2 to 24.30 mg N-N2O m−2, from 601.89 mg C-CO2 m−2 to 1170.34 mg C-CO2 m−2 and from 1.22 mg C-CH4 m−2 to 1.31 mg C-CH4 m−2, respectively. The overall results of the investigation highlighted that application on the soil surface reduced nitrous oxide emission, while the carbon dioxide emission increased significantly with smaller pellet diameter.

Recycling Pig Slurry Solid Fraction Compost as a Sound Absorber

The aim of this investigation was to determine the physical and acoustical properties of compacts made from composted pig slurry solid fraction (SF) in order to assess the potential to recycle this agricultural waste as a sound absorber. The compacts were obtained by compression. The physical parameters investigated were bulk density, durability, and particle size distribution. The acoustical features of the compacts were studied with an impedance tube device in order to verify the acoustic absorption coefficient. Two composts were prepared: pig SF compost without a bulking agent (SSFC) and pig SF compost with wood chips as a bulking agent (WCC). The study’s results indicated that compost particles dimension played a key role in the physical and acoustical properties of the compacts: the smaller the particles, the higher the physical and acoustical properties of the compacts. The densification process increased the bulk density of the investigated composts up to 690 kg m−3 for SSFC and 660 kg m−3 for WWC, with, respectively, medium (77.9%) and low (66.5%) durability. The addition of woody bulking agent significantly reduced the absorption coefficient: the best results, in terms of potential use as a sound absorber, were observed for compacts made from composted pig slurry solid fraction without the addition of wood chips.

Fertilizer value and greenhouse gas emissions from solid fraction pig slurry compost pellets

SUMMARYConversion of pig slurry to pellets is a desirable fertilizer option for farmers who want to mitigate environmental pollution from slurry accumulation. The goals of the current investigation were to determine the fertilizer properties of pig slurry solid fraction (SF) pellets and to assess its potential to enhance soil properties in order to reduce ammonia (NH3) volatilization and greenhouse gas (GHG) emissions. Various parameters influence SF-based pellet fertilizer effectiveness: bulking agent use during composting, pellet diameter sizing and soil application type (superficially or incorporated into the soil). Two composts from the same pig slurry SF obtained from a screw press separator were prepared: pig SF compost without a bulking agent (SSFC) and pig SF compost with wood chips as the bulking agent (wood chip compost (WCC)). For each compost type, pellets of two different diameters (6 and 8 mm) were produced. A mesocosm experiment, conducted with maize plants, was used to test the fertilizer value of the considered pellets. In total, three compost fertilizers – SSFC, WCC and nitrogen: phosphorus: potassium mineral fertilizer 15 : 15 : 15, plus one unfertilized control treatment – were applied at the same N rate (equivalent to 200 kg/ha) using two different methods (surface and soil incorporation). After 65 days, above-ground biomass, roots and soil samples were collected and analysed. Subsequently, a second mesocosm study was undertaken to measure NH3and GHG emissions released from pellet fertilization. Ammonia volatilization was determined immediately after pellet application, while carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions were monitored for 57 days. Study results indicated that both pellet types were effective slow-release fertilizers for maize. Additionally, three actions seemed to make the nutrients contained in pig SF compost pellets more available to plants: addition of a bulking agent before composting, use of small diameter pellets and soil incorporation of the fertilizer.

Phytotoxicity and Chemical Characterization of Compost Derived from Pig Slurry Solid Fraction for Organic Pellet Production

The phytotoxicity of four different composts obtained from pig slurry solid fraction composted by itself (SSFC) and mixed with sawdust (SC), woodchips (WCC) and wheat straw (WSC) was tested with bioassay methods. For each compost type, the effect of water extracts of compost on seed germination and primary root growth of cress (Lepidium Sativum L.) was investigated. Composts were also chemically analysed for total nitrogen, ammonium, electrical conductivity and heavy metal (Cu and Zn). The chemicals were correlated to phytotoxicity indices. The mean values of the germination index (GI) obtained were 160.7, 187.9, 200.9 and 264.4 for WSC, WCC, SC and SSFC, respectively. Growth index (GrI) ranged from the 229.4%, the highest value, for SSFC, followed by 201.9% for SC, and 193.1% for WCC, to the lowest value, 121.4%, for WSC. Electrical conductivity showed a significant and negative correlation with relative seed germination at the 50% and 75% concentrations. A strong positive correlation was found for water-extractable Cu with relative root growth and germination index at the 10% concentration. Water-extractable Zn showed a significant positive correlation with relative root growth and GI at the 10% concentration. These results highlighted that the four composts could be used for organic pellet production and subsequently distributed as a soil amendment with positive effects on seed germination and plant growth (GI > 80%).

Improving the product stability and fertilizer value of cattle slurry solid fraction through co-composting or co-ensiling

Separating dairy cattle slurry in a liquid and solid fraction (SF) is gaining more interest, since it enables a more targeted use of both fractions. However, the valorization of the SF is limited on P-rich soils, due to its high P content, and the export or use as bedding material requires sanitation. Therefore, we investigated the influence of composting or ensiling the SF, whether or not mixed with bulking agents, on the product quality in terms of fertilizer value, sanitation and stability. Ensiling can be considered as a controlled storage method for conserving C and nutrients. Soil amendment with co-ensiled SF resulted in a higher N mineralization and crop growth compared to amendment of co-composted SF. Co-composting SF with structure-rich feedstock materials optimized the composting process and sanitation when compared with composting pure SF and did not increase the risk for extreme-heat-resistant spores of thermophilic aerobic spore-forming bacteria (X-TAS). Further, the composts contained more P per unit of fresh weight than the silages, beneficial for the export of the composted SF. The oxygen uptake rate was found to be less powerful to determine the stability of fresh, composted and ensiled SF.

Synthesis, structure and mechanical properties of ice-templated tungsten foams

Abstract

Evaluation of two composting strategies for making pig slurry solid fraction suitable for pelletizing

In this study, two composting strategies (not turned and turned windrows) of pig slurry solid fraction (SF) were evaluated and compared in terms of their suitability to obtain a composted manure appropriate for further pelletizing (i.e., moisture content <40%). The effect of the two composting strategies on carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and ammonia (NH3) emissions were also investigated.Six identical SF windrows of approximately 4 m3 and 1800 kg were set up outside, on a concrete pad in an open-sided, roofed facility, and composted for a period of 72 days. During the experimental period, three SF windrows were composted unturned (NTW), while the others three SF windrows were turned (TW) six times: at day 7, 16, 28, 35, 50 and 57. Carbon dioxide, methane, nitrous oxide and ammonia emissions were measured three times a week for the first 3 weeks and twice per week thereafter for the 72 days of composting. In correspondence of each turning operation, gases emissions rates from TW, were evaluated two times: before and immediately after turning. Due to the production of heat generated during the composting process, high losses of water occurred from both NTW and TW. However, at the end of the trial the average moisture content in composted manure from NTW and from TW resulted, respectively, 46.7% and 34.6%. Therefore, under the specific conditions adopted in this study, composting of pig slurry SF in NTW did not give a suitable product for further pelletizing. In addition, composted manure from NTW resulted in significantly (p < 0.05) lower total nitrogen (2.9% vs 3.4%) and NO3–N (714 mg kg−1 vs 1358 mg kg−1) content. However, in terms of CO2-eq, total gaseous emissions recorded over 72 days of trial from TW (120.4 kg CO2-eq. t−1) were approximately 95% higher as compared to those (64.7 kg CO2-eq. t−1) obtained from NTW.

Nitrogen fertiliser value of digested dairy cow slurry, its liquid and solid fractions, and of dairy cow slurry

An understanding of crop availability of livestock slurry nitrogen (N) is necessary to maximise crop N use efficiency and to minimise environmental losses. Results from field and laboratory incubation experiments suggest that first-year crop availability of slurry N comes mainly from its ammonium fraction because net mineralisation of organic N is often negligible in the short term. A two-year field experiment during 2011 and 2012 in northern Italy was undertaken with several aims: to estimate the N fertiliser value of raw dairy cow slurry, digested dairy cow slurry, and the liquid and solid fractions of the digested slurry, and to verify if applied ammonium recovery was similar both among slurries and between slurries and inorganic N fertiliser (ammonium sulphate). Different fertilisers were applied before silage maize cultivation followed by an unfertilised Italian ryegrass crop. The results showed that ammonium recovery was significantly higher in mineral-fertilised (75%) versus slurry-fertilised (30%) treatments, except in digested slurry (65%). This indicates that ammonium applied with organic materials is less efficient than when applied with mineral fertiliser. For the digested slurry and its liquid fraction, most of the applied ammonium was available to the maize during its application year (55%) due to a low carbon (C)/organic N ratio. The apparent N recovery of the raw slurry and digested slurry solid fraction increased substantially between the first (-1.4%) and second (20%) years, as these materials had high C/organic N ratios; they likely immobilised N for several months post application, producing residual effects during the Italian ryegrass and next maize crops.

Influence of Dairy Cattle Slurry Solid Fraction Compost Combined with Mineral Nitrogen Fertilizer on the Growth of Greenhouse Lettuce

Winter lettuce response to the application of composts from the solid fraction of dairy cattle slurry was assessed in combination with mineral nitrogen (N) fertilizer throughout a randomized block experiment under greenhouse conditions. Lettuce yield did not increase with mineral N fertilizer, possibly because the lettuce was preceded by a heavily fertilized tomato crop, and the amount of mineral N (114 kg ha−1) in the soil at the beginning of the experience was greater than the amount of N (64–89 kg ha−1) accumulated in the lettuce shoots of all of the treatments. In contrast, lettuce yield and N uptake increased with compost application, suggesting other benefits in addition to N availability resulting from its use as a soil amendment. Therefore, dairy cattle slurry solid fraction mature compost can be recommended for vegetable production, and mineral N recommendation is suggested to pursue previous soil mineral N analysis.

Microstructure of Al Alloy Semi-Solid Slurry Made in Metallic Vessel Using Vibrating Plate

Recently, semi-solid slurry making method using metallic vessels, called "Cup-method", have been studied by the authors. In this method, semi-solid slurry with globular and fine structure is obtained only by pouring molten metal at certain temperature into a metallic vessel which is designed for desired slurry volume and solid fraction of the slurry. The method provides us shorter slurry making time and finer microstructure of α grain with around 50 μm in its size. However, the cup-method requires precise control in the slurry making condition; therefore it is difficult to obtain the homogeneous microstructure in the slurry, especially for the larger slurry. In this study, mechanical vibration was introduced to enhance homogeneity and fine microstructure generation. As a result, mechanical vibration provides the fine and homogeneous distribution of microstructure for wider slurry making conditions. Fine and non-dendrite structure of the slurry could be obtained even by using higher superheated melt, while the conventional method without vibration showed coarse and dendritic microstructure in the similar conditions.

Simple technologies for on-farm composting of cattle slurry solid fraction

Composting technologies and control systems have reached an advanced stage of development, but these are too complex and expensive for most agricultural practitioners for treating livestock slurries. The development of simple, but robust and cost-effective techniques for composting animal slurries is therefore required to realise the potential benefits of waste sanitation and soil improvement associated with composted livestock manures. Cattle slurry solid fraction (SF) was collected at the rates of 4m3h−1 and 1m3h−1 and composted in tall (1.7m) and short (1.2m) static piles, to evaluate the physicochemical characteristics and nutrient dynamics of SF during composting without addition of bulking agent materials, and without turning or water addition. Highest maximum temperatures (62–64°C) were measured in tall piles compared to short piles (52°C). However, maximum rates of organic matter (OM) destruction were observed at mesophilic temperature ranges in short piles, compared to tall piles, whereas thermophilic temperatures in tall piles maximised sanitation and enhanced moisture reduction. Final OM losses were within the range of 520–660gkg−1 dry solids and the net loss of OM significantly (P<0.001) increased nutrient concentrations during the composting period. An advanced degree of stabilization of the SF was indicated by low final pile temperatures and C/N ratio, low concentrations of NH4+ and increased concentrations of NO3- in SF composts. The results indicated that minimum intervention composting of SF in static piles over 168days can produce agronomically effective organic soil amendments containing significant amounts of OM (772–856gkg−1) and plant nutrients. The implications of a minimal intervention management approach to composting SF on compost pathogen reduction are discussed and possible measures to improve sanitation are suggested.

EFFECTS OF COMPOST MATURATION AND TIME OF APPLICATION ON THE GROWTH AND NUTRIENT ACCUMULATION BY ORGANIC CABBAGE

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Organic Horticulture: Productivity and Sustainability EFFECTS OF COMPOST MATURATION AND TIME OF APPLICATION ON THE GROWTH AND NUTRIENT ACCUMULATION BY ORGANIC CABBAGE

Evolução das características físico-químicas e dinâmica dos nutrientes durante a compostagem da fracção sólida do chorume

Cattle slurry solid fraction (SF) was collected from two dairy farms and composted in tall (1.7 m) and short (1.2 m) static piles to evaluate the physical-chemical characteristics and nutrient dynamics of SF during composting. Highest maximum temperatures (62–64 oC) were achieved in tall piles compared to short piles (52 oC). Therefore, tall piles enhanced compost sanitation. Final OM losses were within the range of 520-660 g kg-1 and nutrient content gradually increased throughout the composting period, due to the net loss of OM. Linear regression between nutrient and OM contents showed highly significant correlation coefficients (P <0.001), which decreased by the following order: N, Ca, P and K. The low temperature, C/N ratio, and content of NH4+-N combined with increased concentrations of NO3--N indicated that SF composts were stabilized. The high concentration of OM and macronutrients in the dry matter of final composts, together with a low electrical conductivity (0.6–1.4 dS m-1), suggested that SF composts would be effective as soil organic amendments and suitable for use in agriculture.