Search

Anaerobic digestion and composting of biowastes are vital pathways to recycle carbon and nutrients for agriculture. However, plastic contamination of soil amendments and fertilizers made from biowastes is a relevant source of (micro‐) plastics in (agricultural) ecosystems. To avoid this contamination, plastic containing biowastes could be pyrolyzed to eliminate the plastic, recycle most of the nutrients, and create carbon sinks when the resulting biochar is applied to soil. Literature suggests plastic elimination mainly by devolatilization at co‐pyrolysis temperatures of > 520°C. However, it is uncertain if the presence of plastic during biomass pyrolysis induces the formation of organic contaminants or has any other adverse effects on biochar properties. Here, we produced biochar from wood residues (WR) obtained from sieving of biowaste derived digestate. The plastic content was artificially enriched to 10%, and this mixture was pyrolyzed at 450°C and 600°C. Beech wood (BW) chips and the purified, that is, (macro‐) plastic‐free WR served as controls. All biochars produced were below limit values of the European Biochar Certificate (EBC) regarding trace element content and organic contaminants. Under study conditions, pyrolysis of biowaste, even when contaminated with plastic, can produce a biochar suitable for agricultural use. However, thermogravimetric and nuclear magnetic resonance spectroscopic analysis of the WR + 10% plastics biochar suggested the presence of plastic residues at pyrolysis temperatures of 450°C. More research is needed to define minimum requirements for the pyrolysis of plastic containing biowaste and to cope with the automated identification and determination of plastic types in biowaste at large scales. [ABSTRACT FROM AUTHOR]

BACKGROUND: Despite the optimal characteristics of peat, more environmental‐friendly materials are needed in the nursery sector, although these must guarantee specific quantitative and qualitative commercial standards. In the present study, we evaluated the influence of biochar and compost as peat surrogates on yield and essential oil profile of two different varieties of basil (Ocimum basilicum var. Italiano and Ocimum basilicum var. minimum). In two 50‐day pot experiments, we checked the performances of biochar from pruning of urban trees and composted kitchen scraps, both mixed in different proportions with commercial peat (first experiment), and under different nitrogen (N) fertilization regimes (second experiment), in terms of plant growth and volatile compounds profile of basil. RESULTS: Total or high substitution of peat with biochar (100% and 50% v.v.) or compost (100%) resulted in seedling death a few days from transplantation, probably because the pH and electrical conductivity of the growing media were too high. Substrates with lower substitution rates (10–20%) were underperforming in terms of plant growth and color compared to pure commercial peat during the first experiment, whereas better performances were obtained by the nitrogen‐fertilized mixed substrates in the second experiment, at least for one variety. We identified a total of 12 and 16 aroma compounds of basil (mainly terpenes) in the two experiments. Partial replacement of peat did not affect basil volatile organic compounds content and composition, whereas N fertilization overall decreased the concentration of these compounds. CONCLUSION: Our results support a moderate use of charred or composted materials as peat surrogates. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Maritime Antarctic King George Island (South Shetland Islands) has experienced rapid warming in recent decades, but the impacts on soil organic matter (SOM) decomposition remain ambiguous. Most vegetation cover is dominated by bryophytes (mosses), whereas a few vascular plants, such as Deschampsia antarctica and Colobanthus quitensis grow interspersed. Therefore, SOM is mainly enriched with carbohydrates and C‐alkyl, provided by mosses, which lack lignin as a precursor for aromatic compounds and humus formation. However, there is no clear answer to how substrate and temperature increase changes in Antarctic microbial respiration. We determined in what way SOM mineralization changes with temperature and substrate addition by characterizing the temperature sensitivity (Q10) of soil respiration in an open‐top chamber warming experiment. We hypothesized that: (a) cold‐tolerant microorganisms are well adapted to growing in maritime Antarctic soils (~ 0°C), so would not respond to low and moderate temperature increases because they undergo various metabolic mechanism adjustments until they experience increasing temperatures toward optimum growth (e.g., by enzyme production); and (b) cellulose, as a complex carbonaceous substrate of vegetated areas in Maritime Antarctic soils, activates microorganisms, increasing the Q10 of soil organic carbon (SOC) mineralization. Soils (5–10 cm) were sampled after four consecutive years of experimental warming for SOC composition, microbial community structure, and C mineralization at 4, 12, and 20°C with and without cellulose addition. Functional group chemoheterotrophs, represented mainly by Proteobacteria, decomposed more refractory SOC (aromatic compounds), as indicated by nuclear magnetic resonance (NMR) spectroscopy, in ambient plots than in warming plots where plants were growing. The C‐CO2 efflux from the incubation experiment remained stable below 12°C but sharply increased at 20°C. Q10 varied between 0.4 and 4 and was reduced at 20°C, whereas cellulose addition increased Q10. In conclusion, as confirmed during field studies in a climate scenario, cold‐tolerant microorganisms in maritime Antarctic soils were slightly affected by increasing temperature (e.g., 4–12°C), with reduced temperature sensitivity, as summarized in a conceptual model. [ABSTRACT FROM AUTHOR]

Soil as a C and N sink: Who is the major player - soil minerals, soil organic matter quality, microbial activity or their interplay? Nutrient availability in soils: Can our knowledge on soil interfaces improve biotechnological approaches or soil management to decrease the need for artificial fertilizers? In line with this and within the fourth session I Dynamics of pollutants at soil interfaces i , Mikhail Borisover (2021) introduced a new approach to quantify sorption-desorption hysteresis using single-point desorption isotherms in liquid-phase sorption experiments in terms of the Gibbs free energy of non-relaxed states. Soil can be seen as an important and delicate interface between the biosphere, hydrosphere, atmosphere and lithosphere. [Extracted from the article]

Hydrothermal carbonization and dry pyrolysis transform sewage sludge (SS) into nitrogen‐ (N) and phosphorus‐ (P) rich hydrochars (Hyd) and pyrochars (Py), respectively, which may act as slow‐release fertilizers with carbon (C) sequestration potential. Whereas this has been mostly studied with short‐term experiments, this study focused on the cycling of char‐derived N, P and C after ageing during a second grass cropping cycle. Lolium perenne was grown for 3 months in pots on soil mixed with 13C and 15N‐enriched SS, Hyd or Py and allowed to age during a first cropping period of 10‐month incubation. The δ15N of the plants confirmed that even during the second cropping, N derived from the amendments was plant accessible. Higher uptake of N from Hyd than from Py is explained by the lower biodegradability of the latter. Plant growth during the second cropping period was associated with a decrease of total P in all treatments, but only the soils with Hyd and Py evidenced an increase of Olsen P. Thus, during the second cropping, more insoluble P was mobilized from the carbonized residues than P needed for plant growth. Compared to control soils prepared with and without KNO3, higher biomass production was yielded with the amended soils. Hyd proved to have the highest longer‐term N mobilization potential. Following the change in δ13C of the soil, we observed that during the second incubation, independently of their aromaticity, all amendments and the native soil organic matter had comparable turnover rates, although the amount of organic matter with slower turnover added with the amendment increased with aromaticity. A rough estimation of the impact of thermal treatment of SS on its C‐sequestration potential revealed no major differences between char types. The higher fertilization capacity of Hyd, however, indicates that it is a good candidate for soil amendment as long‐term fertilization is combined with a long‐term increase of the SOC pool. Highlights: Medium‐term fertilization and C‐sequestration potential of chars from sewage sludge were tested.Hydrochar (Hyd) and pyrochar (Py) provide N and P for plant growth during a second cropping period.Compared to soils with and without KNO3, Hyd and Py increase plant productivity of the second crop.On a long‐term scale, native SOM, amended SS, its aged Hyd and Py show comparable turnover rates. [ABSTRACT FROM AUTHOR]

In semi-arid Mediterranean soils, water availability is the most limiting factor, negatively affecting the organic matter (OM) degradation. The aim of this work is to study under controlled laboratory conditions how three sources of OM [municipal solid waste (MSW), sheep manure (SM) and cow manure (CM)] behave when they are applied to an agricultural soil subjected to a severe year-long drought. In order to apply the same concentration of OM to the soil (16·92 Mg OM ha−1), 2 kg of soil was mixed with 30, 67·41 and 55·25 Mg ha−1 (dry matter) of MSW, CM and SM, respectively. Two levels of irrigation were employed: (i) watered soils and (ii) non-watered soils. Soil's chemical properties [water soluble carbon (WSC), humic acids, fulvic acids and protein mass distribution], biological properties (soil microbial biomass carbon and o-diphenoloxidase activity) and solid-state 13C cross-polarisation magic angle spinning nuclear magnetic resonance spectroscopy were determined. In watered soils, the soil microbial biomass carbon was higher in the SM than in CM and MSW treatments (9·9% and 23·1%, respectively). The WSC was significantly higher in SM than in CM (55·7%) and MSW (78·7%) treatments. A decrease in the content of O-alkyl C and an increase in alkyl C, aromatic C and carboxyl C were observed. In non-watered soils, the biochemical properties and alkyl C and alkyl/ O-alkyl ratio decreased, whereas WSC content and O-alkyl C increased. These results indicated that the evolution of OM and the activity of the microbial community in non-watered soils were very different to those in the watered soils. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT Self-standing films of poly(ω-hydroxyl hexadecanoic acid) [poly(ω-OHC16)] have been prepared by noncatalyzed melt-polycondensation in air at 150, 175, and 200 °C. Poly(ω-OHC16)s obtained are characterized as polyesters by infrared spectroscopy (FT-IR) and solid state magic angle spinning 13C nuclear magnetic resonance (13C MAS-NMR). Structurally, poly(ω-OHC16)s are quite crystalline as revealed by wide angle X-ray diffraction (WAXD). The presence of oxygen in the reaction atmosphere causes a mild oxidation in the form of peroxyester species, tentatively at the interphase between poly(ω-OHC16) crystallites, and the structure amorphization. The interfacial peroxyester phase ends up in the encapsulation of the polyester grains and provides a barrier towards the action of solvents. Thermal stabilization and insolubility resulting from the synthesis conditions used are interesting features to prepare solvent and heat resistant poly(ω-OHC16) coatings. Thus, a few microns thick poly(ω-OHC16) layer has been fabricated on aluminum foil and its resistivity towards a chloroform:methanol (1:1, v:v) mixture has been confirmed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44350. [ABSTRACT FROM AUTHOR]

Hydrochars, technically manufactured by hydrothermal carbonization (HTC) of biomass residues, are recently tested in high numbers for their suitability as feedstock for bioenergy production, the bioproduct industry, and as long‐term carbon storage in soil, but ecological effects in the soil–plant system are not sufficiently known. Therefore, we investigated the influence of different biomass residues and process duration on the molecular composition of hydrochars, and how hydrochar addition to soils affected the germination of spring barley (Hordeum vulgare L.) seeds. Samples from biomass residues and the corresponding hydrochars were analyzed by pyrolysis‐field ionization mass spectrometry (Py‐FIMS) and gaseous emissions from the germination experiments with different soil–hydrochar mixtures by gas chromatography/mass spectrometry (GC/MS). The molecular‐level characterization of various hydrochars by Py‐FIMS clearly showed that the kind of biomass residue influenced the chemical composition of the corresponding hydrochars more strongly than the process duration. In addition to various detected possible toxic substances, two independent mass spectrometric methods (Py‐FIMS and GC/MS) indicated long C‐chain aliphatic compounds which are typically degraded to the C2–unit ethylene that can evoke phytotoxic effects in high concentrations. This showed for the first time possible chemical compounds to explain toxic effects of hydrochars on plant growth. It is concluded that the HTC process did not result in a consistent product with defined chemical composition. Furthermore, possible toxic effects urgently need to be investigated for each individual hydrochar to assess effects on the soil organic matter composition and the soil biota before hydrochar applications as an amendment on agricultural soils. [ABSTRACT FROM AUTHOR]

The chemistry of wet Spodosols (Aquods) differs from well-drained Spodosols. Two different hypotheses have been suggested to explain the contrasting genesis of wet spodic horizons. This study attempted to determine whether Aquods at a Danish peat-bog wetland site are a result of(i) in situ illuviation under a fluctuating water cable, or (ii) degradation of a former Fe-rich, well-drained spodic horizon. Methods included soil surveys, wet chemical analyses, micromorphology, pollen analysis, and radiocarbon dating ofsoil organic matter (OM) fractions. Aquods, and soil material with spodic features, were exclusively found in sandy material at the margins of or underneath sphagnum peat bogs, whereas Inceptisols were found on well-drained sandy deposits only. Aluminum content was very high and Fe low in spodic materials with ortstein properties. Solid-state 13C nuclear magnetic resonance (NMR) spectra of wet sandy 2Bs horizons were dominated by alkyl C (70%) from water-insoluble OM and were clearly distinct from NMR spectra of overlying 2Bhsm material. Pollen analysis revealed that an open forest with a thick mor layer dominated until shortly after 5000 yr BP, when sphagnum was first recorded. Radiocarbon ages of bulk soil C in the spodic horizons had mean residence times of 4500 to 4400 yr. Accordingly, the spodic B horizon was probably formed by strong in situ illuviation of Al-OM complexes before the sphagnum peat bog formation. This suggests that spodic material formation and thus strong C accumulation underneath this Danish peat bog took place for a limited period, only in susceptible parent material, and at the margins of the expanding peat bog. [ABSTRACT FROM AUTHOR]

Land-use change affects not only the amount of soil organic matter (SOM) but also its composition. We performed cross-polarization magic angle spinning (CPMAS) 13C and 15N nuclear magnetic resonance (NMR) spectroscopy to investigate the chemical composition of bulk SOM in topsoils (0–15 cm) under different land use, namely native forest (NF), 27-year cropland with wheat/soybean rotation (CL) and 27-year rangelands with guineagrass (RG) and with bahiagrass (RB), in south-east Bolivia. The findings of this study showed only a subtle alteration of composition of bulk SOM despite the large changes in carbon (C) content. Nevertheless, NF and RB showed a slightly lower abundance of aromatic C but a higher proportion of alkyl C compared to CL and RG where the loss of organic matter was substantial. This suggests that relatively stable components dominated by aromatic structures had relatively enriched during SOM decomposition under agricultural practices. A slight disparity of SOM composition observed between RG and RB (less O-alkyl C but more aromatic C in RG than RB) suggests that grass species influenced SOM quality even under the same land use, namely the rangeland. On the other hand, organic N composition was less affected by land use or management practice than C forms. [ABSTRACT FROM AUTHOR]

To elucidate the mechanisms responsible for the long-term retention of soil C, soil samples were retrieved from a paleosolic A horizon (Mbur) buried underneath a Bronze Age mound and from waterlogged anaerobic (Man) and aerobic zones (Mac) within the mound. For comparison with a modern soil, samples were taken from the surrounding arable field (Ar). The soils were characterized by cross-polarization magic angle spinning 13C nuclear magnetic resonance spectroscopy, by phospholipid fatty acid (PLFA) analysis, and by CO2 production during incubation. At sampling, the Ar, Man, Mac, and Mbur soils contained 22.6, 17.9, 6.5, and 6.2 g C kg-1 soil, respectively. Compared with the Ar and Man soils, the Mbur and Mae soils were depleted in alkyl C, N-alkyl C, and O-alkyl C and enriched in aromatic and carboxylic groups. The content of PLFA in the mound soils was much lower than normally found for arable soils and the ability of the deprived biomass to decompose glucose was retarded and included a 2- to 3-wk lag phase. The lability of C left under aerobic conditions for more than three millennia did not differ significantly from that of C in the contemporary Ar soil. Although the chemical nature of the C in the Ar and Man soils was similar, C that had resided under anaerobic conditions was less labile than C from the arable soil. We consider the persistence of C in the unwaterlogged parts of the burial mound to result from physical restrictions imposed on gas exchange and water availability, and thus restricted microbial activity, rather than from biochemical recalcitrance of the remaining C. [ABSTRACT FROM AUTHOR]

Soil contaminated with 2,4,6‐trinitrotoluene (TNT) and spiked with [14C]‐ and [15N3]‐TNT was subjected to an anaerobic–aerobic soil slurry treatment and subsequently analyzed by radiocounting and solid‐state 15N nuclear magnetic resonance (NMR) spectroscopy. This treatment led to a complete disappearance of extractable radioactivity originating from TNT and almost all of the radioactivity was recovered in the insoluble soil fraction. As revealed by solid‐state 15N NMR, a major fraction of partially reduced metabolites of TNT was immobilized into the soil during the early stage of the anaerobic treatment, although some of the compounds (i.e., aminodinitrotoluenes and azoxy compounds) were extractable by methanol. Considerable 15N intensity was assigned to condensation products of TNT metabolites. A smaller signal indicated the formation of azoxy N. This signal and the signal for nitro groups were not observed at the end of the anaerobic phase, revealing further reduction and/or transformation of their corresponding compounds. An increase of the relative proportion of the condensation products occurred with increasing anaerobic incubation. Aerobic incubation resulted in a further decrease of aromatic amines, presumably due to oxidative transformations or their involvement in further condensation reactions. The results of the study demonstrate that the anaerobic–aerobic soil slurry treatment represents an efficient strategy for immobilizing reduced TNT in soils. [ABSTRACT FROM AUTHOR]