Digested Pig Slurry Research Articles

Visible intruders: Tracing (micro-) plastic in organic fertilizers

Agricultural soils have been identified as potential reservoirs for plastic pollution, with adverse effects on soil properties. Primary sources of plastic input in agricultural landscapes are associated with the application of sewage sludge or compost. Understanding the sources and anticipated plastic content is crucial in mitigating plastic pollution in agricultural fields. This study presents one of the first investigations into the plastic content and other impurities, e.g. glass, of seven organic fertilizers (biowaste compost, digested pig slurry, sewage sludge compost, dry chicken manure, green waste compost, sewage sludge, and a mixed digestate comprising pig slurry, chicken manure, and 74 % renewable raw materials). Potentially visible foreign substances were assessed on the surface of each fertilizer pile. No impurities could be detected in digested pig slurry, chicken manure, and mixed digestate. For the remaining fertilizers, visible potential foreign substances were collected, cleaned, visually described, weighed, photographed, size measured, and chemically characterized using ATR-FTIR. The quantification revealed that plastic particles are the most abundant and are contained in all other fertilizers, in contrast to glass and metal. An increasing trend in plastic particle number per m2: green waste < biowaste < sewage sludge compost < sewage sludge, which is about 4 times greater in sewage sludge than in green waste compost, could be observed. However, sewage sludge compost has the largest plastic mass and surface area per square meter. This illustrates that sewage sludge compost application can be a significant entry pathway for visual plastics into agricultural soils.

Impacts on water quality of producing biogas on pig farms as a function of the associated agricultural practices

The aim of this study was to assess positive or negative impacts of anaerobic digestion (AD) on water quality using a systemic approach. To this end, we used the agro-hydrological model Topography-based Nitrogen Transfer and Transformation (TNT2), a spatially explicit model that simulates nitrogen and water flows at the watershed scale on a daily time step. Four scenarios were constructed and analyzed: a baseline before the introduction of AD (S0), AD with adjusted fertilization (S1), AD with unadjusted fertilization (S2), and agroecological AD (S3). The results showed that, when spreading practices were similar and an equivalent amount of effective nitrogen was applied, digested pig slurry generally had a predicted amount of nitrate leaching similar to that of undigested pig slurry. In addition, replacing catch crops with energy cover crops had little impact on water quality. Scenario S3 was the most favorable one for water quality and biogas production, but not for soil organic nitrogen storage and food and feed production. This study’s strength is its systemic approach, which considered both environmental and agronomic aspects to assess the scenarios.

Effects of Digested Pig Slurry on Photosynthesis, Carbohydrate Metabolism and Yield of Tomato (Solanum lycopersicum L.)

Soilless cultivation of vegetables is widely used in production. It is also well accepted that digested slurry is frequently applied as a fertilizer in agricultural production. However, the effect of digested pig slurry on yield and quality of tomato soilless cultivation, as well as the yield and quality influenced by plant carbohydrate metabolism, remain unexplored. Here, the dual inputs of fertilizers (digested pig slurry (D) and mineral fertilizer (M)) and soilless substrates (peat substrate (P) and cinder substrate(C)) consisted of four treatments. The dry biomass and fruit yields, photosynthetic parameters, carbohydrate contents and metabolism enzymes in leaves and fruits were recorded during the experimental period. The highest fruit yields were obtained in DP and MP treatments. Although DP treatment significantly increased the fresh weight of single fruits by 18.0% compared to MP treatment, it reduced the number of ripe fruits. The photosynthetic efficiency and carbohydrate contents (sucrose, glucose and fructose) in leaves were generally higher in DP treatment compared to other treatments, as well as the activities of sucrose phosphate synthase and AGPase in leaves. The soluble sugar contents of fruits in DP and DC treatments were enhanced by 12.3% and 37.0%, respectively, compared to MP and MC treatments. Moreover, the current results showed that DP treatment significantly increased the activity of acid invertase in fruit by 36.3%, 31.3%, and 42.2%, respectively, compared to MP, DC, and MC treatments, and decreased the activity of AGPase by 24.2%, 16.0%, and 36.4%, respectively. The current results have demonstrated that DP treatment had better yield and quality, owing to digested pig slurry increasing the photosynthetic efficiency and source strength, and regulated the activities of carbohydrate metabolism enzymes.

The application of N-butyl Phosphorothioate Triamine and Dicyandiamide changes the soil N2O production path

ABSTRACT This study aims to explore the effect of nitrification inhibitor combined with urease inhibitor on soil N2O emission under different nitrogen application depths. We carried out a soil column simulation test under 25°C. The combination of 1% N-butyl Phosphorothioate Triamine (NBPT) and 5% Dicyandiamide (DCD) was added to the soil. Anaerobically digested pig slurry (ADPS) was used as a nitrogen source and applied to four soil depths (soil surface (0 cm), 5 cm, 10 cm, and 15 cm, respectively). It was found that the inhibitory effects of NBPT and DCD on the soil N2O emission were significantly affected by different nitrogen application depths. When the ADPS was applied at 15 cm, 10 cm, and on the soil surface, the combination of 1% NBPT and 5% DCD could inhibit soil N2O emission by 46.1%, 21.7%, and 34.6%, respectively. Redundancy analysis (RDA) showed that the addition of inhibitors changed the microbial paths of soil N2O production. The dominant microbial path of soil N2O production after adding inhibitors was from ammonia oxidation dominated by AOB-amoA to denitrification dominated by nirS and nirK.

Anaerobic Digestion of Pig Slurry in Fixed-Bed and Expanded Granular Sludge Bed Reactors

Anaerobic digestion of animal manure is a potential bioenergy resource that avoids greenhouse gas emissions. However, the conventional approach is to use continuously stirred tank reactors (CSTRs) with hydraulic retention times (HRTs) of greater than 30 d. Reactors with biomass retention were investigated in this study in order to increase the efficiency of the digestion process. Filtered pig slurry was used as a substrate in an expanded granular sludge bed (EGSB) reactor and fixed-bed (FB) reactor. The highest degradation efficiency (ηCOD) and methane yield (MY) relative to the chemical oxygen demand (COD) were observed at the minimum loading rates, with MY = 262 L/kgCOD and ηCOD = 73% for the FB reactor and MY = 292 L/kgCOD and ηCOD = 76% for the EGSB reactor. The highest daily methane production rate (MPR) was observed at the maximum loading rate, with MPR = 3.00 m3/m3/d at HRT = 2 d for the FB reactor and MPR = 2.16 m3/m3/d at HRT = 3 d for the EGSB reactor. For both reactors, a reduction in HRT was possible compared to conventionally driven CSTRs, with the EGSB reactor offering a higher methane yield and production rate at a shorter HRT.

Environmental performance of the innovative, patented mixing system in an agricultural biogas plant based on LCA approach

Renewable energy production in biogas plants seems to be recognised in literature from the environmental perspective. However, innovative technologies are still launched to improve energy efficiency. In this perspective, the authors developed the patented hybrid pump to improve the yield of methane production and reduce the environmental impact of renewable energy production. This research assesses the environmental performance of an innovative, patented hybrid pump designed for mixing the input of anaerobic digestion of pig slurry, based on the Life Cycle Assessment (LCA) approach. The comparative environmental analysis of two different mixing systems installed in the pilot biogas plant was conducted on the basis of the selected impact categories. The application of innovative mixing technology with a hybrid pump increased the percentage yield of methane in biogas from slurry by about 10% compared to a conventional hydraulic pump. The application of a hybrid pump in the tested biogas plant reduced the Cumulative Energy Demand (CED) ratio by almost 30% compared to a conventional hydraulic pump. A similar level was obtained for other environmental impact ratios in terms of global warming potential, abiotic depletion of fossil fuels, human toxicity, acidification, and eutrophication.

A biochemical methane potential of pig slurry

This study assesses the methane production potential for the Anaerobic Digestion of Pig Slurry, using two different Substrate to Inoculum Ratios, 0.65, and 1, and its comparison with the theoretical prediction. The Specific Biogas Production, the Specific Methane Production, and the average methane content were determined for both experiments and adjusted to Standard Temperature (273.15 K) and Pressure (1 atm). The results reached in this study show that the experience conducted with a SIR of 1 produced more volume of biogas, with higher methane content than the one with the lower SIR. With a SIR of 1.0, it was achieved a SMP of 0.568 NL CH4/g VS with an average methane content of 83%. The Technical Digestion Time was found to be 12 days. By comparing the experimental BMP with the estimated value of 0.623 NL CH4/g VS, it was possible to conclude that the estimated value presented a deviation of just 2.96 % during the assay with a SIR of 1.

Optimisation of Scenedesmus almeriensis production using pig slurry as the sole nutrient source

Pig slurry was used as the sole nutrient source to produce biomass of the microalga Scenedesmus almeriensis using laboratory-scale bubble column photobioreactors. No differences in terms of biomass productivity were observed between fresh and digested pig slurry. The optimum dilution of the slurry to enable the processing of the largest amount of pig slurry per litre was 5%, which led to a biomass productivity rate of 0.68 g·L−1·day−1, comparable to that of the standard growth medium formulated using pure chemicals (0.70 g·L−1·day−1). The inlet N-NH4+ concentration was approximately 180 mg·L−1, with inhibitory effects being observed at concentrations higher than 200 mg·L−1. The N-NH4+, N-NO3−, P-PO43−, and chemical oxygen demand removal rates were 34.1, 0.5, 2.1, and 519.3 mg·L−1·day−1. The observed turbidity of the media did not affect microalgal growth at the studied dilutions. Ozonation effectively reduced the chemical oxygen demand concentration of the media, but no effect on microalgal growth was observed. Overall, pig slurry was an effective nutrient source for the production of S. almeriensis, and this strain was shown to be robust with a N-NH4+ tolerance up to 200 mg·L−1 and the potential use in the bioremediation of agro-industrial wastes.

Ammonium and Phosphate Recovery in a Three Chambered Microbial Electrolysis Cell: Towards Obtaining Struvite from Livestock Manure

Ammonia and phosphate, which are present in large quantities in waste streams such as livestock manure, are key compounds in fertilization activities. Their recovery will help close natural cycles and take a step forward in the framework of a circular economy. In this work, a lab-scale three-chambered microbial electrolysis cell (MEC) has been operated in continuous mode for the recovery of ammonia and phosphate from digested pig slurry in order to obtain a nutrient concentrated solution as a potential source of fertilizer (struvite). The maximum average removal efficiencies for ammonium and phosphate were 20% ± 4% and 36% ± 10%, respectively. The pH of the recovered solution was below 7, avoiding salt precipitation in the reactor. According to Visual MINTEQ software modelling, an increase of pH value to 8 outside the reactor would be enough to recover most of the potential struvite (0.21 mmol L−1 d−1), while the addition of up to 0.2 mM of magnesium to the nutrient recovered solution would enhance struvite production from 5.6 to 17.7 mM. The application of three-chambered MECs to the recovery of nutrients from high strength wastewater is a promising technology to avoid ammonia production through industrial processes or phosphate mineral extraction and close nutrient natural cycles.

In-situ methane enrichment in continuous anaerobic digestion of pig slurry by zero-valent iron nanoparticles addition under mesophilic and thermophilic conditions

The effect of zero-valent iron nanoparticles (nZVI) addition on methane production during anaerobic digestion of pig slurry was assessed. Experiments were conducted using two experimental set-ups: batch and long-term continuous operation at a fixed nZVI dosage. Two different temperature operation ranges (mesophilic and thermophilic) were assessed. Biogas production and methane content were monitored, and the specific methanogenic activity of the biomass and nZVI oxidation state were evaluated at different times. The results of batch experiments at mesophilic temperature operation showed an inhibition of methane production at all tested dosages (42, 84, 168 and 254 mgnZVI g−1 VSS concentrations), while methane production was boosted with the lowest dosage in thermophilic temperature operation. In continuous operation, nZVI addition produced an increase in methane content of biogas, achieving values between 80 and 85% in both temperature ranges. The average methane production rate increased 165% and 94% with respect to the control in thermophilic and mesophilic temperature range, respectively. The oxidation state of nZVI showed a value of +3 almost immediately after contact with substrate and a slower progressive oxidation during the reactors operation. The obtained results indicate that nZVI addition in anaerobic digestion is an interesting strategy for in situ biogas upgrading.

NH3, N2O, and NO emissions from digested pig slurry stored under different temperatures: Characteristics and microbial mechanisms

Storage temperature is a key factor in determining gas emissions from slurry storage. The reactive nitrogen-related gas (NH3, N2O, and NO) emission characteristics and resulting mechanisms from digested pig slurry stored under different temperatures of 5 (A5), 15 (B15), 25 (C25), and 35 °C (D35) were investigated in this study. Results showed that the temperature increase from 15 to 25 °C was crucial for the changes in the total chemical characteristics of slurry, the increase of gas emissions, and the nitrifiers and denitrifiers accumulation in the slurry. Chemical oxygen demand, total nitrogen (TN), and total ammonia nitrogen content of the slurry decreased while pH increased significantly during storage under C25 and D35, while no obvious changes can be found under A5 and B15. NH3, N2O, and NO emissions increased by 284%, 451%, and 454%, respectively, when the storage temperature increased from 15 to 25 °C. The highest emissions of NH3, N2O, and NO were observed in D35, with the emission factor being 42.3% ± 9.0%, 2.26% ± 0.96%, and 0.11% ± 0.03% of initial TN, respectively; while the lowest emission factor was 4.2% ± 0.2%, 0.04% ± 0.01%, and 0.0003% ± 0.0001% for NH3, N2O, and NO in A5, respectively. The high temperature caused the increased abundance of Nitrosomonas, leading to the high N2O emission in D35. Vulcanibacillus and Thauera were the dominant denitrifiers in the microbial communities, and their increased abundance was another possible explanation for increased N2O emission on C25 and D35. Therefore, regulating slurry temperature to lower than 15 °C can effectively limit the NH3 and N2O emissions, and thus contributed to the air pollution reduction and global warming control. Meanwhile, compared with the cool temperature conditions, extra mitigation options were suggested to be applied to control the gases emissions when slurry was stored under hot conditions such as in summer.

Hydrophobic membranes for ammonia recovery from digestates in microbial electrolysis cells: Assessment of different configurations

The combination of hydrophobic membranes and microbial electrolysis cells (MEC) was assessed in two different configurations in order to recover ammonia from anaerobically digested pig slurry. Polytetrafluorethylene (PTFE) hydrophobic membranes were inserted both in an H-type three-chamber cell (MEC-H) and a two-chamber sandwich configuration MEC (MEC-S), both fitted with a cationic exchange membrane (CEM) dividing the anode and cathode compartments. The use of electrochemical techniques such as electrochemical impedance spectroscopy was applied to monitor the increase of the biofilm on the anode, related to the decrease of the charge transfer resistance. When operated in the higher organic loading rate (28 ± 5kgCODm−3d−1) the current density produced in the MEC-H was 1.40 ± 0.71 A m−2, compared to 0.61 ± 0.28 A m−2 in the MEC-S. The flux of ammonium through the CEM in the MEC-H was of 3.4 ± 1.2 g N m−2 h−1. Regarding the recovery of ammonia through the hydrophobic membrane, the flux of ammonia was of 1.5 and 0.7 g N m−2 h−1 in the MEC-H and MEC-S, respectively, mainly governed by the pH value and the ammonia concentration of the catholyte. The combination of MEC with hydrophobic membranes reveals as a suitable technology for the recovery of ammonia and treatment of high strength wastewater such as livestock manure.

The pump-mixed anaerobic digestion of pig slurry: new technology and mathematical modeling

Biogas production is a relatively novel and developing branch of the renewable fuel sector, which allows agricultural waste, and more, to be used as a feedstock. New technologies have been integrated into the process to improve its efficiency. In this study, a pump-mixed anaerobic digestion concept is considered for both experimental and modeling approaches. The experiment included a total of nine configurations with the same geometry (140 dm3 of total reactor volume) but different hydraulic retention times and mixing intervals. The measurements were used to create and optimize a mathematical model. The complete-stirring assumption, which underlies most anaerobic digestion (AD) simulations, is no longer valid in this case. Thus, the novel concept is developed by assuming that the liquid phase is split into three separate sections, which approximates the concentration gradient in a real reactor. This method allows partial differential equations to be avoided, which could potentially affect the calculation efficiency. The final mean accuracy of the model in the tested range was estimated to be 86.60% while, in selected parts of the scope, was close to 90%. The pump-mixed anaerobic digestion technique in the experiment achieved high production performance (above 8 dm3 of product per 1 dm3 of feedstock) while maintaining a high methane content (approximately 65%). The comparison between the reactor stirred by an impeller, and the pump-mixed, indicated that the proposed configuration ensures better production stability. Additionally, it was possible to achieve a higher biogas production rate with the same feedstock concentration.

Biogas Upgrading and Ammonia Recovery from Livestock Manure Digestates in a Combined Electromethanogenic Biocathode—Hydrophobic Membrane System

Anaerobic digestion process can be improved in combination with bioelectrochemical systems in order to recover energy and resources from digestates. An electromethanogenic microbial electrolysis cell (MEC) coupled to an ammonia recovery system based on hydrophobic membranes (ARS-HM) has been developed in order to recover ammonia, reduce organic matter content and upgrade biogas from digested pig slurry. A lab-scale dual-chamber MEC was equipped with a cation exchange membrane (CEM) and ARS with a hydrophobic membrane in the catholyte recirculation loop, to promote ammonia migration and absorption in an acidic solution. On the other hand, an electromethanogenic biofilm was developed in the biocathode to promote the transformation of CO2 into methane. The average nitrogen transference through the CEM was of 0.36 gN m−2 h−1 with a removal efficiency of 31%, with the ARS-HM in the catholyte recirculation loop. The removal of ammonia from the cathode compartment helped to maintain a lower pH value for the electromethanogenic biomass (7.69 with the ARS-HM, against 8.88 without ARS-HM) and boosted methane production from 50 L m−3 d−1 to 73 L m−3 d−1. Results have shown that the integration of an electromethanogenic MEC with an ARS-HM allows for the concomitant recovery of energy and ammonia from high strength wastewater digestates.

Early adoption of no-till mitigates soil organic carbon and nitrogen losses due to land use change

Conversion of grasslands to agriculture has promoted land degradation and losses of soil organic carbon (SOC). Early adoption of no-till (NT) and use of organic fertilizers could mitigate SOC losses in response to minimum soil disturbance and increased carbon (C) inputs. To test this hypothesis, we assessed changes on soil C and nitrogen (N) pools in a Nitisol under natural grassland vegetation from Southern Brazil. The grassland was converted to agriculture in 2012 with a double-cropping system of maize (Zea mays L.) and black oats (Avena strigosa Scherb.). The experiment had split-plots replicated in four randomized blocks. Conventional tillage (CT) and NT systems were tested in the main plots (10 × 25 m, LxW). Maize was amended with 140 kg N-total ha−1 from different N sources in the subplots (10 × 5 m): urea (UR), pig slurry (PS), digested pig slurry (DS), and composted pig slurry (CS), besides a control treatment without fertilization (CTR). Soil was sampled in 2012 and 2017 to assess short-term changes (5 years) on total organic C (TOC) and N (TN) stocks in the 0−60 cm depth as well on the particulate and mineral associated C and N pools in the 0−30 cm soil layer. We also assessed C and N contents within water-stable aggregates (WSA) in the 0−5 cm soil layer. Soils under CT have lost 9 % of TOC and 21 % of TN (11.5 and 2.6 Mg ha−1, respectively) from the 0−60 cm layer as compared with original stocks under the grassland. No-till soils accumulated TOC at surface layers and mitigated TOC and TN losses by respective 82 and 34 % when compared with the grassland in the 0−60 cm layer. No-till increased particulate C and N fractions compensating losses on the respective mineral associated fractions. In contrast, depletion of mineral associated fractions accounted for most of total C and N stocks losses under CT. No-till soils had nearly doubled the mass of large macroaggregates and tripled the C and N contents within this WSA fraction as compared with CT. The use of CS augmented C and N contents within large macroaggregates by respective 35 and 40 % in comparison with UR and by 72 and 86 %, respectively, if compared with the CTR. Early adoption of NT can mitigate TOC losses following conversion of grasslands to agriculture. The association of NT with CS augmented C and N stabilization within large macroaggregates, improved soil quality and may contribute with SOC accrual in NT soils.

Short-term effect of pig slurry and its digestate application on biochemical properties of soils and emissions of volatile organic compounds

Production of biogas through anaerobic digestion of organic wastes should play an important role in sustainable development of energy supply, and the environmental effects of digestates have to be assessed. We investigated the effect of anaerobic digestion of pig slurry (PS) on the molecular quality of the digestate produced. The consequences of digested (DPS) and undigested PS use as organic soil fertilizer on soil microbial and biochemical properties and C-gas emissions (CO2 and volatile organic compounds) were studied during a two-month incubation. PS and DPS differed in the amount of volatile organic compounds (VOCs) emitted, in their organic C and lignin contents but not in their active microbial composition. Application of both types of slurry to the soil immediately increased the content of soil dissolved organic carbon (DOC) compared to the control soil. The application of DPS induced few changes in the biochemical composition of soil organic matter compared to its raw material (PS) that increased the amount of phenolic compounds. After 60 days, both amended and control soils contained similar amounts of DOC, amended soils presenting a more diverse biochemical composition of their soil organic matter. Application of both slurries to soil triggered a succession of different active microbial communities, which could be attributed to the introduction of new microorganisms and the input of new labile organic carbon. Changes in fungal communities were stronger than those of bacteria and archaea; however, only slight differences were observed between the slurries. Different fluxes and emission dynamics of five VOCs (methanol, acetone, DMS, 2-pentanone and phenol) were observed during the incubation time following application of PS or DPS to soil while no differences in CO2 emissions were observed. The present study calls for long-term field studies with VOC analyses as a promising tool to differentiate organic fertilization practices.

The effect of acidification of pig slurry digestate applied on winter rapeseed on the ammonia emission reduction

The Agriculture is the main source of ammonia emissions. It generates around 75% of global emissions of ammonia to the atmosphere and soil fertilisation accounts for half of agricultural emissions. Ammonia emissions have a negative impact on ecosystems and human health, as it is able to accumulate both as solid particles and as an integral part of acid cases. Measures to reduce ammonia emissions can be divided into three large groups: the first group is ammonia-reducing measures in animal housing, the second group is ammonia-reducing measures during manure storage, and the third group is ammonia-reducing measures during the application of manure. Measurements of ammonia emissions were carried out in the parish of Jaunberze, which took place on 30 April and 1 May 2018. Sulphuric acid was used for acidification of pig slurry digestate. Picarro G2508 was used for on field measurement of ammonia concentrations with 1 second interval, a measurement time of one session was 400 seconds. The volume of the chamber was 60 l and was connected to the Picarro G2508 using a 10 m long Teflon tube. The measurement of ammonia emissions was with three repetitions for each measurement, with a reference error of less than 5%. Emissions were measured at different time intervals: immediately after digestate distribution, 2 hours, 4 hours and the 24 hours after digestate application. The emission of ammonia from digestate without vegetation after 24 hours was 13 kg ha−1, for acidified digestate without vegetation 8.5 kg ha −1, while the acidified digestate with vegetation within 24 hours reached 2.5 kg of ha −1 ammonia emissions, five times lower than that of non-vegetation.

Attapulgite enhances methane production from anaerobic digestion of pig slurry by changing enzyme activities and microbial community

This study evaluated the effect of attapulgite addition on the anaerobic digestion of pig slurry. Results showed that attapulgite addition increased methane yield by 8.9%–37.3% and affected methane production kinetics. Attapulgite with the addition loading of 10 g/L obtained the highest methane yield of 210.4 mL/g volatile solids. Attapulgite accelerated the rates of hydrolysis, acetogenesis, and methanogenesis, as evidenced by the increases in the activities of β-glucosidase, protease, dehydrogenase, and coenzyme F420; the abundance of hydrolytic and acetogenic bacteria (Clostridiales, Syntrophobacterales, and Fibrobacterales); and the abundance of methanogenic microorganisms (Methanomicrobiales). These phenomena can be ascribed to both the reduced ammonia nitrogen due to attapulgite adsorption and the increased trace elements, such as Ca2+, Mg2+, K+, and Fe3+ ions, due to attapulgite release. However, excessive dose of attapulgite (≥30 g/L) decreased the promotion of methane production by reducing the enzyme activities of hydrolytic and methanogenic steps and lowering the abundance of hydrolytic, acetogenic, and methanogenic microorganisms due to the high levels of free ammonia and metal ions, such as Mg2+, at the initial phase of digestion. These results provided insights into the improvement of methane production during the anaerobic digestion of animal slurry.

The effect of anaerobic digestate derived composts on the metabolite composition and thermal behaviour of rosemary

The study reports on the effect of anaerobic digestate derived composts on the metabolite composition and thermal behaviour of rosemary (Rosmarinus officinalis L.). Plants were cultivated in semiarid soil under four different fertiliser treatments (composts of anaerobic digested cattle (C) or pig slurry (P) at 30t/ha and 60 t/ha, and two control treatments (inorganic fertiliser and no fertiliser application). Samples of leaves and stems were analysed to investigate the effect of treatment on chemical composition and thermochemical properties. Three orthogonal analytical approaches were used, namely: Fourier transform mid infrared spectroscopy (FTIR), gas chromatography/mass spectrometry (GC/MS) and thermochemical gravimetric analysis (TGA). FTIR and GC/MS showed fertiliser treatment resulted in tissue specific changes in sample metabolite composition. Fertiliser treatment was detected to change the thermogravimetric properties of the leaf samples and from inorganic and composted pig slurry digestate treatments had greater ash content and lower proportions of fixed carbon compared with samples from the unfertilised control treatment. This study provides information on how the composition of rosemary might be altered by fertiliser application in regions of poor soil, and has implications for biomass quality when rosemary is grown on semi-wild sites for the purpose of soil improvement.

Organic amendment-driven removal and speciation of metals using wormwood in two contrasting soils near an abandoned copper mine

To test the hypothesis that humic acid (HA), anaerobically digested pig slurry filtrate (APS), and their combination would differently affect the chemical speciation and extractability of metals (cadmium, copper, and zinc) and their uptake by plants, we conducted a pot experiment using wormwood in two texturally contrasting soils (sandy loam and clay loam) collected from a field near an abandoned Cu mine. Four treatments were laid out: HA at 23.5 g kg−1 (HA), APS at 330 mL kg−1 (APS), HA at 23.5 g kg−1 and APS at 330 mL kg−1 (HA + APS), and a control. Each treatment affected the chemical speciation and mobility of the metals, and thereby resulting in variable patterns of plant biomass yield and metal uptake. The APS supported plant growth by increasing nutrient availability. HA supported or hindered plant growth by impacting the soil’s water and nutrient retention capacity and aeration, in a soil texture-dependent manner, while consistently enhancing the immobilization of heavy metals. Temporal increases in whole-plant dry matter yield and metal accumulation suggested that the plants were capable of metal hyperaccumulation. The results were discussed in terms of the mobility of metals and plant growth and corroborated by the 15N recovery of soil- and plant-N pools under H and HS treatments. Therefore, for effective phytoremediation of polluted soils, an appropriate combination of plant growth promoters (APS) and chelating agents (HA) should be predetermined at the site where chemical stabilization of pollutants is desired.