Metal sorption by biochars: A trade-off between phosphate and carbonate concentration as governed by pyrolysis conditions.

Three feedstocks, pine wood, grass and cow manure, were pyrolyzed under various conditions and tested on their ability to sorb metals in aquatic systems. The feedstocks were pyrolyzed at 2 different temperatures (350 °C and 550 °C) and 2 different residence times (10 and 60 min) and resulting biochars were assessed on their capability to immobilize Pb, Cu, Cd and Zn. Manure-based chars, and to a lesser extent grass-based chars, featured high concentrations of phosphates and carbonates. These anions play an important role in metal sorption because they form insoluble complexes with the metals. Washing reduced the concentration of these anions, leading to a reduced sorption of metals by the biochar. The carbonate concentration on the biochars' surface increased at higher reactor temperature and longer residence times. The opposite trend was observed for the phosphate concentration and the cation exchange capacity. Accordingly, the optimal temperature-residence time combination for sorption was a trade-off between these properties. Biochar produced from cow manure and pyrolyzed at 550 °C for 10 min showed the best sorption for all metals considered.

Limitations for phytoextraction management on metal-polluted soils with poplar short rotation coppice-evidence from a 6-year field trial.

Poplar clones were studied for their phytoextraction capacity in the second growth cycle (6-year growth) on a site in the Belgian Campine region, which is contaminated with Cd and Zn via historic atmospheric deposition of nearby zinc smelter activities. The field trial revealed regrowth problems for some clones that could not be predicted in the first growth cycle. Four allometric relations were assessed for their capacity to predict biomass yield in the second growth cycle. A power function based on the shoot diameter best estimates the biomass production of poplar with R2 values between 0.94 and 0.98. The woody biomass yield ranged from 2.1 to 4.8 ton woody Dry Mass (DM) ha-1 y-1. The primary goal was to reduce soil concentrations of metals caused by phytoextraction. Nevertheless, increased metal concentrations were determined in the topsoil. This increase can partially be explained by the input of metals from deeper soil layers in the top soil through litterfall. The phytoextraction option with poplar short rotation coppice in this setup did not lead to the intended soil remediation in a reasonable time span. Therefore, harvest of the leaf biomass is put forward as a crucial part of the strategy for soil remediation through Cd/Zn phytoextraction.

Phosphorus retention capacity in red ferralitic soil.

In this study the main physical-chemical characteristics of red ferralitic soil to use as substrate in subsurface wetlands was determined. The P-removal was evaluated in a short-term isotherm batch experiment and in a column percolation experiment. The acid characteristic and high content of iron minerals in the red ferralitic soil facilitated the phosphorus removal. Also the sorption isotherms at two different temperatures were obtained. The results showed that the sorption capacity increases with an increase in solution temperature from 25 to 35 °C. The experimental data were fitted to Langmuir and Freundlich models, having a better fit to the Freundlich isotherms. The maximum P-sorption capacities estimated using the Langmuir isotherm were 0.96 and 1.13 g/kg at 25 and 35 °C respectively. Moreover a column experiment was carried out at two different flows. Sequential extractions of the phosphorus-saturated soil indicated that phosphorus is mainly bound with iron or aluminum minerals. The results have demonstrated a good potential for red ferralitic soil for phosphorus removal from urban wastewater.

Vertical flow constructed wetlands: kinetics of nutrient and organic matter removal.

The kinetics of organic matter and nutrient removal in a pilot vertical subsurface wetland with red ferralitic soil as substrate were evaluated. The wetland (20 m(2)) was planted with Cyperus alternifolius. The domestic wastewater that was treated in the wetland had undergone a primary treatment consisting of a septic moat and a buffer tank. From the sixth week of operation, the performance of the wetland stabilized, and a significant reduction in pollutant concentration of the effluent wastewater was obtained. Also a significant increase of dissolved oxygen (5 mg/l) was obtained. The organic matter removal efficiency was greater than 85% and the nutrient removal efficiency was greater than 75% in the vertical subsurface wetland. Nitrogen and biochemical oxygen demand (BOD) removal could be described by a first-order model. The kinetic constants were 3.64 and 3.27 d(-1) for BOD and for total nitrogen, respectively. Data on the removal of phosphorus were adapted to a second-order model. The kinetic constant was 0.96 (mg/l)(-1) d(-1). The results demonstrated the potential of vertical flow constructed wetlands to clean treated domestic wastewater before discharge into the environment.

Arsenic in drinking water wells on the Bolivian high plain: Field monitoring and effect of salinity on removal efficiency of iron-oxides-containing filters.

In the rural areas around Oruro (Bolivia), untreated groundwater is used directly as drinking water. This research aimed to evaluate the general drinking water quality, with focus on arsenic (As) concentrations, based on analysis of 67 samples from about 16 communities of the Oruro district. Subsequently a filter using Iron Oxide Coated Sand (IOCS) and a filter using a Composite Iron Matrix (CIM) were tested for their arsenic removal capacity using synthetic water mimicking real groundwater. Heavy metal concentrations in the sampled drinking water barely exceeded WHO guidelines. Arsenic concentrations reached values up to 964 µ g L⁻¹ and exceeded the current WHO provisional guideline value of 10 µ g L⁻¹ in more than 50% of the sampled wells. The WHO guideline of 250 mg L⁻¹ for chloride and sulphate was also exceeded in more than a third of the samples, indicating high salinity in the drinking waters. Synthetic drinking water could be treated effectively by the IOCS- and CIM-based filters reducing As to concentrations lower than 10 µ g L⁻¹. High levels of chloride and sulphate did not influence As removal efficiency. However, phosphate concentrations in the range from 4 to 24 mg L⁻¹ drastically decreased removal efficiency of the IOCS-based filter but had no effects on removal efficiency of the CIM-based filter. Results of this study can be used as a base for further testing and practical implementation of drinking water purification in the Oruro region.

Enhanced phytoextraction of uranium and selected heavy metals by Indian mustard and ryegrass using biodegradable soil amendments.

The applicability of biodegradable amendments in phytoremediation to increase the uptake of uranium (U), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb) and zinc (Zn) by Indian mustard (Brassica juncea) and ryegrass (Lolium perenne) was tested in a greenhouse experiment. Plants were cultivated during one month on two soils with naturally or industrially increased contaminant levels of U. Treatments with citric acid, NH4-citrate/citric acid, oxalic acid, S,S-ethylenediamine disuccinic acid (EDDS) or nitrilotriacetic acid (NTA) at a rate of 5 mmol kg(-1) dry soil caused increases in soil solution concentrations that were up to 18 times higher for U and up to 1570 times higher for other heavy metals, compared to the controls. Shoot concentrations increased to a much smaller extent. With EDDS, 19-, 34-, and 37-fold increases were achieved in shoots of Indian mustard for U, Pb and Cu, respectively. The increases in plant uptake of Cd, Cr and Zn were limited to a factor of four at most. Ryegrass generally extracted less U and metals than Indian mustard. Despite a marked increase of U and metal concentrations in shoots after addition of amendments, the estimated time required to obtain an acceptable reduction in soil contaminant concentrations was impractically long. Only for Cu and Zn in one of the studied soils, could the Flemish standards for clean soil theoretically be attained in less than 100 years.

Presence and mobility of arsenic in estuarine wetland soils of the Scheldt estuary (Belgium).

We aimed to assess the presence and availability of arsenic (As) in intertidal marshes of the Scheldt estuary. Arsenic content was determined in soils sampled at 4 sampling depths in 11 marshes, together with other physicochemical characteristics. Subsequently, a greenhouse experiment was set up in which pore water arsenic (As) concentrations were measured 4 times in a 298-day period in 4 marsh soils at different sampling depths (10, 30, 60 and 90 cm) upon adjusting the water table level to 0, 40 and 80 cm below the surface of these soils. The As content in the soil varied significantly with sampling depth and location. Clay and organic matter seem to promote As accumulation in the upper soil layer (0-20 cm below the surface), whereas sulfide precipitation plays a significant role at higher sampling depths (20-100 cm below the surface). The As concentrations in the pore water of the greenhouse experiment often significantly exceeded the Flemish soil sanitation thresholds for groundwater. There were indications that As release is not only affected by the reductive dissolution of Fe/Mn oxides, but also by e.g. a direct reduction of As(V) to As(III). Below the water table, sulfide precipitation seems to lower As mobility when reducing conditions have been sufficiently established. Above the water table, sulfates and bicarbonates induce As release from the solid soil phase to the pore water.

Effect of biodegradable amendments on uranium solubility in contaminated soils.

Chelate-assisted phytoextraction has been proposed as a potential tool for phytoremediation of U contaminated sites. In this context, the effects of five biodegradable amendments on U release in contaminated soils were evaluated. Three soils were involved in this study, one with a relatively high background level of U, and two which were contaminated with U from industrial effluents. Soils were treated with 5 mmol kg(-1) dry weight of either citric acid, NH(4)-citrate/citric acid, oxalic acid, S,S-ethylenediamine disuccinic acid or nitrilotriacetic acid. Soil solution concentration of U was monitored during 2 weeks. All amendments increased U concentration in soil solution, but citric acid and NH(4)-citrate/citric acid mixture were most effective, with up to 479-fold increase. For oxalic acid, S,S-ethylenediamine disuccinic acid and nitrilotriacetic acid, the increase ranged from 10-to 100-fold. The highest concentrations were observed 1 to 7 days after treatment, after which U levels in soil solution gradually decreased. All amendments induced a temporary increase of soil solution pH and TOC that could not be correlated with the release of U in the soil solution. Thermodynamic stability constants (log K) of complexes did not predict the relative efficiency of the selected biodegradable amendments on U release in soil solution. Amendments efficiency was better predicted by the relative affinity of the chelate for Fe compared to U.

Degradability of ethylenediaminedisuccinic acid (EDDS) in metal contaminated soils: implications for its use soil remediation.

Previous research has identified ethylenediaminedisuccinate (EDDS) as a promising biodegradable alternative for persistent compounds such as EDTA for application in soil washing or enhanced phytoextraction of heavy metals. This study examines heavy metal mobilization in three polluted soils varying in soil composition, with specific attention for competitive behaviour for complexation between the various metals and major elements, such as Al, Fe, Mn, Ca and Mg. In addition, amendment biodegradability was compared between the different soil types. The selected soils included a moderately contaminated calcareous clayey soil, a dredged sediment derived surface soil with similar soil characteristics yet more heavily polluted with Cd, Cr and Zn, and a sandy soil moderately contaminated by historical smelter activity (atmospheric deposition). Biodegradability of EDDS in the three soils varied distinctly. This was mainly expressed in the duration of the lag phase prior to metal complex degradation, and not so much in the half life when degradation effectively did set in. Differences in the lag phase were attributed to differences in soil pollution. However, EDDS was fully degraded within a period of 54 d in all soils regardless of initial delay. Assessment of the cation mobilisation patterns in the three soils under study revealed that mainly Ca, Fe and Al can reduce effectiveness of heavy metal mobilisation by competition for complexation.

Delivery of a DNAzyme targeting c-myc to HT29 colon carcinoma cells using a gold nanoparticulate approach.

The objective of the current study was to develop cellular delivery approaches for catalytic DNA enzymes (DNAzymes) which cleave targeted messenger RNA, using vectors based on colloidal gold. The model DNAzyme was a 32mer oligonucleotide designed to specifically interact with and cleave c-myc mRNA. Colloidal gold particles were prepared by reduction of tetrachlororauric [III] acid with sodium citrate. Particles could be produced in the 1-90 nm range. A cationic substrate linked to transferrin was electrostatically/hydrophobically bound to the gold particle. These vectors were then treated with the DNAzyme to yield the condensed DNA-cationic polymer-particulate product. The pH (4-11.5), the quantity of the DNAzymes (0.079-0.567 microg/probe), the cationic polymer (polylysine (PL) or polyethylenimine (PEI)) as well as the surfactant (PVP) concentration (0-0.5%) were varied to give stable constructs which decomplexed under the desired conditions (i.e., in lysosomes and at lower pH values). Cellular uptake of the FITC-labelled c-myc DNAzyme incorporated in this vector was measured using FACS analysis in human HT29 colon carcinoma cells. Data suggested that PEI gave better delivery efficiencies than PL. The use of PVP to stabilize the formed dispersions was detrimental to DNAzyme delivery when PL was used but had little effect in the PEI systems. In the best cases, delivery to 77% of the cells was possible using PEI with the PVP stabilizer and completing the DNA condensation at pH 5.5 with 0.118 microg of DNAzyme/probe. In contrast, the best conditions for PL gave only transfection to 43% of the cells (no PVP, condensed at pH 5.7 and with a loading of 0.079 microg DNAzyme/probe). The PL probe tended to be more toxic than the PEI-based systems (65% cell death in PL transfected cells compared to 22% for PEI). These results suggest that cellular targeting using colloidal gold appears feasible for DNAzyme delivery.

Impact of organic amendments (biochar, compost and peat) on Cd and Zn mobility and solubility in contaminated soil of the Campine region after three years.

To determine the long-term impact of organic amendments on metal (Cd and Zn) immobilization, soil from the Campine region was amended with holm oak-derived biochar, compost, and peat, and monitored over a 3-year period. Pot experiments were conducted by mixing the amendments independently at 2% and 4% (g/g) with the soil. The mobility and solubility of metals in the treatments were assessed by means of rhizon soil moisture samplers, sequential BCR extractions, and diffusive gradient in thin films (DGT). Over the three-year period, the 2% biochar addition resulted in an average decrease in pore water concentration of 40% for Cd and 48% for Zn whereas the 4% addition led to an average decrease of 66% for Cd and 77% for Zn. The immobilization effect in the biochar treatments was attributed to the consistently higher pH and lower concentrations of dissolved organic carbon (DOC) in the soil. The latter may have been caused by sorption of DOC onto the surface of biochar thereby increasing its negatively charged functional groups that are able to sorb cations. On the other hand, compost and peat had the unwanted effect of significantly increasing the concentrations of Cd and Zn in the soil pore water. This was partly due to the formation of soluble organo-metallic complexes as significantly higher DOC concentrations were found in the compost and peat treatments. Results from the DGT measurements, after a 24 h deployment time, revealed a low resupply (R ≤ 0.4) of Cd and Zn from the solid phase to the soil solution in both amended and unamended soil. This suggests a case of slow metal desorption kinetics in the soil that was relatively unchanged by the presence of organic amendments.

Rapid and irreversible sorption behavior of 7Be assessed to evaluate its use as a catchment sediment tracer.

Beryllium-7 (7Be) has been used as a sediment tracer to evaluate soil redistribution rates at hillslopes and as a tool to estimate sediment residence time in river systems. A key assumption for the use of 7Be as a sediment tracer is the rapid and irreversible sorption of 7Be upon contact with the soil particles. However, recent studies have raised questions about the validity of these assumptions. Seven soil types were selected to assess the adsorption rate of 7Be on the soil particles, subsequently an extraction experiment was performed to assess the rate of desorption. Next, different treatments were applied to assess the impact of soil pH, fertilizer, humic acid and organic matter on the adsorption of Be. Finally, the influence of regularly occurring cations present on the soil complex on the adsorption of Be on pure clay minerals was evaluated. The adsorption rate experiment showed a rapid and nearly complete sorption of Be for Luvisols and Cambisols under agriculture. For a temperate climate Stagnosol under forest and two highly weathered tropical Ferralsols sorption of Be was less rapid and less complete. This may result in an incomplete adsorption of 7Be on these three soils when runoff initiates, which could lead to an overestimation of erosion rates and sediment residence time. Additional observations were made during the extraction experiment, showing a significant loss of Be from the forest Stagnosol and a stable binding of Be to the arable soils. Of the different treatments applied, only pH showed to be of influence. Finally, Ca2+ and NH4+ on the soil complex had only a limited effect on the adsorption of Be, while Al3+ in combination with a low pH inhibits the adsorption of Be on the exchange complex of the pure clay minerals. All these findings more rigorously support the use of 7Be as a soil redistribution tracer in arable soils in a temperate climate at a hillslope scale. The use of 7Be in highly weathered Ferralsols or forest rich environments should be limited to avoid overestimations of erosion rates. The spatially extended use of 7Be to evaluate residence times of sediments should be avoided in catchments with rapid changing environmental parameters as they might influence the sorption behavior of 7Be.

Cadmium phytoremediation potential of Brassica crop species: A review.

Cadmium (Cd) is a highly toxic metal released into the environment through anthropogenic activities. Phytoremediation is a green technology used for the stabilization or remediation of Cd-contaminated soils. Brassica crop species can produce high biomass under a range of climatic and growing conditions, allowing for considerable uptake and accumulation of Cd, depending on species. These crop species can tolerate Cd stress via different mechanisms, including the stimulation of the antioxidant defense system, chelation, compartmentation of Cd into metabolically inactive parts, and accumulation of total amino-acids and osmoprotectants. A higher Cd-stress level, however, overcomes the defense system and may cause oxidative stress in Brassica species due to overproduction of reactive oxygen species and lipid peroxidation. Therefore, numerous approaches have been followed to decrease Cd toxicity in Brassica species, including selection of Cd-tolerant cultivars, the use of inorganic and organic amendments, exogenous application of soil organisms, and employment of plant-growth regulators. Furthermore, the coupling of genetic engineering with cropping may also help to alleviate Cd toxicity in Brassica species. However, several field studies demonstrated contrasting results. This review suggests that the combination of Cd-tolerant Brassica cultivars and the application of soil amendments, along with proper agricultural practices, may be the most efficient means of the soil Cd phytoattenuation. Breeding and selection of Cd-tolerant species, as well as species with higher biomass production, might be needed in the future when aiming to use Brassica species for phytoremediation.

Accumulation of metals in a horizontal subsurface flow constructed wetland treating domestic wastewater in Flanders, Belgium.

This study assessed the accumulation of metals in a horizontal subsurface flow constructed wetland treating domestic wastewater of 350 PE after three years of operation. Metal concentrations in the influent wastewater, effluent, sediment, leaves, stems, and belowground biomass of Phragmites australis were analysed. Spatial variations were assessed by sampling at increasing distance from the inlet and at different positions across the width of the reed bed. All metals except Fe and Mn were efficiently removed in the CW, total metal concentrations in the effluent complied with basic environmental quality standards for surface water, and dissolved metal concentrations were often lower than analytical detection limits. Removal efficiencies varied between 49% for Ni and 93% for Al. Export of dissolved Mn and particulate Fe occurred, probably related to redox conditions in the sediment. After 3 years of operation, the sediment in the inlet area was significantly contaminated with Zn, Cu, and Cd, whereas Pb could form a contamination problem within the near future. The Cr and Ni levels in the sediment were low throughout the entire reed bed. At this stage of operation, the contamination problem was still situated within the inlet area and metal concentrations in the sediment decreased towards background values further along the treatment path. An exponential decrease of the metal mass in the sediment and belowground biomass was seen for all metals except Mn. Contrary to the other metals, Mn concentrations in the sediment increased with distance. For all metals, less than 2% of the mass removed from the wastewater after passage through the reed bed is accumulated in the aboveground reed biomass. The sediment acts as the primary sink for metals.

Influence of hydrological regime on pore water metal concentrations in a contaminated sediment-derived soil.

Options for wetland creation or restoration might be limited because of the presence of contaminants in the soil. The influence of hydrological management on the pore water concentrations of Cd, Cr, Cu, Fe, Mn, Ni and Zn in the upper soil layer of a contaminated overbank sedimentation zone was investigated in a greenhouse experiment. Flooding conditions led to increased Fe, Mn, Ni and Cr concentrations and decreased Cd, Cu and Zn concentrations in the pore water of the upper soil layer. Keeping the soil at field capacity resulted in a low pore water concentration of Fe, Mn and Ni while the Cd, Cu, Cr and Zn concentrations increased. Alternating hydrological conditions caused metal concentrations in the pore water to fluctuate. Formation and re-oxidation of small amounts of sulphides appeared dominant in determining the mobility of Cd, Cu, and to a lesser extent Zn, while Ni behaviour was consistent with Fe/Mn oxidation and reduction. These effects were strongly dependent on the duration of the flooded periods. The shorter the flooded periods, the better the metal concentrations could be linked to the mobility of Ca in the pore water, which is attributed to a fluctuating CO(2) pressure.

Influence of flooding, salinity and inundation time on the bioavailability of metals in wetlands.

Controlled flooding of lowlands is considered as a potential water management strategy to minimize the risk of flooding of inhabited areas during high water periods. However, due to industrial activities, river water, sediments and soils are often contaminated with metals which may have adverse effects on the ecosystem's structure and functioning. Additionally, salinity may greatly affect the bioavailability and toxicity of metals present or imported into these systems. The effect of contaminated soils under different flooding and salinity exposure scenarios on the growth, reproduction and metal accumulation in the oligochaete Tubifex tubifex (Müller, 1774) were examined. In these bioassays metal contaminated soils were flooded with water of different salinities (0 and 3 psu), and tested after 0, 6 and 12 months of permanent inundation. We indeed found that inundation time had significant decreasing effects on Cu and Zn accumulation; although initial accumulation of Cu and Zn was higher in the previously unflooded soil at the start of the flooding treatment, these differences seem to disappear after 6 months of permanent inundation. Moreover, the complex interaction between substrate type and salinity suggests that redox potential is probably of major importance.

Cu sorption on Phragmites australis leaf and stem litter: a kinetic study.

Decaying organic matter plays an important role in the cycling of metals in wetland ecosystems. Sorption kinetics of Cu(II) on Phragmites australis leaf and stem litter were studied. Fresh leaf and stem litter was sampled from a surface flow wetland at the end of the growing season. The effect of decomposition stage was studied with litter that had been decomposing for a period of 5 months. The Lagergren pseudo-first-order model, the pseudo-second-order model, the Elovich equation and two diffusion models based on spherical intra-particle diffusion were fitted to the experimental data. The sorption capacity was significantly affected by the decomposition of the litter. The sorption process was best described by the pseudo-second-order kinetics (R(2) approximately 0.99) but the rate constant was strongly dependent on the initial Cu concentration. The intra-particle diffusion model fitted the data only slightly less (R(2)>0.95) than the pseudo-second-order model. A theoretical comparison revealed that the good fit with the pseudo-second-order kinetics could be indicative of intra-particle diffusion. Sorption kinetics observed for the leaf and stem litter at different metal concentrations showed a fast initial sorption followed by a slow sorption phase.

Effects of sorption, sulphate reduction, and Phragmites australis on the removal of heavy metals in subsurface flow constructed wetland microcosms.

The removal of Co, Ni, Cu and Zn from synthetic industrial wastewater was studied in subsurface flow constructed wetland microcosms filled with gravel or a gravel/straw mixture. Half of the microcosms were planted with Phragmites australis and half were left unplanted. All microcosms received low-strength wastewater (1 mg L(-1) of Co, Ni, and Zn, 0.5 mg L(-1) Cu, 2,000mg L(-1) SO4) during seven 14-day incubation batches. The pore water was regularly monitored at two depths for heavy metals, sulphate, organic carbon and redox potential. Sorption properties of gravel and straw were assessed in a separate experiment. A second series of seven incubation batches with high-strength wastewater (10 mg L(-1) of each metal, 2,000 mg L(-1) SO4) was then applied to saturate the substrate. Glucose was added to the gravel microcosms together with the high-strength wastewater. Sorption processes were responsible for metal removal during start-up, with the highest removal efficiencies in the gravel microcosms. The lower initial efficiencies in the gravel/straw microcosms were presumably caused by the decomposition of straw. However, after establishment of anaerobic conditions (Eh approximately -200 mV), precipitation as metal sulphides provided an additional removal pathway in the gravel/straw microcosms. The addition of glucose to gravel microcosms enhanced sulphate reduction and metal removal, although Phragmites australis negatively affected these processes in the top-layer of all microcosms.

Fertilizer performance of liquid fraction of digestate as synthetic nitrogen substitute in silage maize cultivation for three consecutive years.

Following changes over recent years in fertilizer legislative framework throughout Europe, phosphorus (P) is taking over the role of being the limiting factor in fertilizer application rate of animal manure. This results in less placement area for spreading animal manure. As a consequence, more expensive and energy demanding synthetic fertilizers are required to meet crop nutrient requirements despite existing manure surpluses. Anaerobic digestion followed by mechanical separation of raw digestate, results in liquid fraction (LF) of digestate, a product poor in P but rich in nitrogen (N) and potassium (K). A 3-year field experiment was conducted to evaluate the impact of using the LF of digestate as a (partial) substitute for synthetic N fertilizer. Two different fertilization strategies, the LF of digestate in combination with respectively animal manure and digestate, were compared to the conventional fertilization regime of raw animal manure with synthetic fertilizers. Results from the 3-year trial indicate that the LF of digestate may substitute synthetic N fertilizers without crop yield losses. Through fertilizer use efficiency assessment it was observed that under-fertilization of soils with a high P status could reduce P availability and consequently the potential for P leaching. Under conditions of lower K application, more sodium was taken up by the crop. In arid regions, this effect might reduce the potential risk of salt accumulation that is associated with organic fertilizer application. Finally, economic and ecological benefits were found to be higher when LF of digestate was used as a synthetic N substitute. Future perspectives indicate that nutrient variability in bio-based fertilizers will be one of the greatest challenges to address in the future utilization of these products.