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Concrete is prone to cracking over time, leading to the deterioration of concrete structures. Using the biomineralization capabilities of bacteria, cracks in concrete can be remediated in favorable conditions. In this study, Bacillus subtilis spores were immobilized in three different healing agents, namely lightweight expanded clay aggregates (LECAs), polyvinyl acetate (PVA) fibers, and an air-entraining admixture (AEA). Bacillus subtilis spores, with a turbidity equivalent to a 4 McFarland standard, were used in three different dosages, namely 0.01, 0.1, and 1% (by weight) of cement. Based on the dosage, three groups were developed and each group consisted of a total of nine mixes, which were differentiated based on the method of delivery of the bacterial spores. The specimens were pre-cracked after 7 days, using an embedded steel rod, after being post-tensioned in a universal testing machine. The self-healing efficiency of the concrete was evaluated using ultrasonic pulse velocity testing and surface crack analysis, using ImageJ software, and the self-healing precipitate was analyzed using microstructural tests, namely scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy analysis. The results verified that the self-healing efficiency of the concrete improved with the increase in the bacterial dosage and with an increase in the curing time. LECAs proved to be a promising bacterial carrier, by accommodating the spores and nutrient media over a period of 196 days. PVA fibers helped in bridging the cracks and provided nucleation sites for the bacteria, which enhanced the calcite precipitation. Similarly, the AEA also improved crack healing by encapsulating the spores and sealing cracks up to 0.25 mm, when used in conjunction with LECAs. Furthermore, microstructural tests verified the formation of calcite as a healing product within the cracks in the bioconcrete. The results of this study offer valuable insights for the construction industry, highlighting the ability of bacteria to reduce the deterioration of concrete structures and promoting a sustainable approach that minimizes the need for manual repairs, particularly in hard-to-reach areas. Full article

The effect of graded doses of ash from biomass wood chips and straw admixture combustion on compost properties was investigated through a set of large-scale experiments. In a compost plant, matured organic composts were prepared from raw organic mixtures based on biodegradable waste, separated digestate, straw, and biomass ash admixture of 0, 3, 6, and 9 wt. %. Final composts, as well as individual components, were analyzed for basic physical and chemical properties, total and available nutrients, and potentially hazardous elements. Biomass ash addition increased the total nutrient content (P, K, Mg, Ca, and S) in the studied composts. The highest ash addition (9 wt. %) increased the nutrient content as follows: Ca (2.6×), Mg (1.6×), K (1.5×), P (1.2×), S (1.3×). However, the availability of some nutrients (especially P, K, and Mg) for plant nutrition was reduced by the increasing amount of ash admixture. Even at the highest dosage of biomass ash addition, desirable chemical (nutrient content) and physical properties of composts (especially dry bulk density) were both obtained. The content of hazardous elements was below the legal limit values in all studied composts. Full article

Research highlights: The admixture of fir to pure European beech hardly affected soil-atmosphere CH₄ and N₂O fluxes but increased soil organic carbon (SOC) stocks at a site in the Black Forest, Southern Germany. Background and objectives: Admixing deep-rooting silver fir has been proposed as a measure to increase the resilience of beech forests towards intensified drying-wetting cycles. Hence, the goal of this study was to quantify the effect of fir admixture to beech forests on the soil-atmosphere-exchange of greenhouse gases (GHGs: CO₂, CH₄ and N₂O) and the SOC stocks by comparing pure beech (BB) and mixed beech-fir (BF) stands in the Black Forest, Germany. Materials and methods: To account for the impact of drying-wetting events, we simulated prolonged summer drought periods by rainout shelters, followed by irrigation. Results: The admixture of fir to pure beech stands reduced soil respiration, especially during autumn and winter. This resulted in increased SOC stocks down to a 0.9 m depth by 9 t C ha⁻¹ at BF. The mixed stand showed an insignificantly decreased sink strength for CH₄ (−4.0 under BB and −3.6 kg C ha⁻¹ year⁻¹ under BF). With maximal emissions of 25 µg N m⁻² h⁻¹, N₂O fluxes were very low and remained unchanged by the fir admixture. The total soil GHG balance of forest conversion from BB to BF was strongly dominated by changes in SOC stocks. Extended summer droughts significantly decreased the soil respiration in both BB and BF stands and increased the net CH₄ uptake. Conclusions: Overall, this study highlights the positive effects of fir admixture to beech stands on SOC stocks and the total soil GHG balance. In view of the positive impact of increased SOC stocks on key soil functions such as water and nutrient retention, admixing fir to beech stands appears to be a suitable measure to mitigate climate change stresses on European beech stands. Full article

A major argument for incorporating deciduous tree species in coniferous forest stands is their role in the amelioration and stabilisation of biogeochemical cycles. Current forest management strategies in central Europe aim to increase the area of mixed stands. In order to formulate statements about the ecological effects of mixtures, studies at the stand level are necessary. In a mixed stand of Norway spruce (Picea abies (L.) Karst.) and silver birch (Betula pendula Roth) in the Ore Mountains (Saxony, Germany), the effects of these two tree species on chemical and microbial parameters in the topsoil were studied at one site in the form of a case study. Samples were taken from the O layer and A horizon in areas of the stand influenced by either birch, spruce or a mixture of birch and spruce. The microbial biomass, basal respiration, metabolic quotient, pH-value and the C and N contents and stocks were analysed in the horizons Of, Oh and A. Significantly higher contents of microbial N were observed in the Of and Oh horizons in the birch and in the spruce-birch strata than in the stratum containing only spruce. The same was found with respect to pH-values in the Of horizon and basal respiration in the Oh horizon. Compared to the spruce stratum, in the birch and spruce-birch strata, significantly lower values were found for the contents of organic C and total N in the A horizon. The findings of the case study indicated that single birch trees have significant effects on the chemical and microbial topsoil properties in spruce-dominated stands. Therefore, the admixture of birch in spruce stands may distinctly affect nutrient cycling and may also be relevant for soil carbon sequestration. Further studies of these functional aspects are recommended. Full article

Parenteral nutrition (PN) has become an integral part of clinical management of very low birth weight premature neonates. Traditionally different components of PN are prescribed individually considering requirements of an individual neonate (IPN). More recently, standardised PN formulations (SPN) for preterm neonates have been assessed and may have advantages including better provision of nutrients, less prescription and administration errors, decreased risk of infection, and cost savings. The recent introduction of triple-chamber bag that provides total nutrient admixture for neonates may have additional advantage of decreased risk of contamination and ease of administration. Full article