Effect of biomass fly ashes from fast pyrolysis bio-oil production on soil properties and plant yield

The reusing of waste bio-oil as additive on enhanced urea-based selective non-catalytic reduction denitrification

Pyrolysis polygeneration has been proven to be effective in solid waste recycling, while cleaner production is hindered by nitrogen oxide emissions and waste oil utilization. In this study, waste bio-oil was proposed as additive for promoting urea-based selective non-catalytic reduction (SNCR) denitrification efficiency to establish bio-oil reusing process and the influence of waste bio-oil on promoting SNCR denitrification were investigated. Then the effects of temperature, bio-oil components and fly ash on SNCR denitrification characteristics were explored. The results illustrated that 5 wt% bio-oil additives would widen the optimum denitrification temperature window by 24.8 % (from 210.25 to 262.43 °C), reduce the reduction temperature by 62.11 °C (from 944.04 to 881.93 °C), and increase the denitrification efficiency by 21 %. Among the main components in waste bio-oil, acetic acid was more effective than phenol and furfural in promoting SNCR denitrification under 900 °C, a large amount of OH was produced to promote the reduction of NH₃ and HNCO. In addition, the existence of fly ash could promote urea oxidation and reduce denitrification efficiency because of the catalytic effect of CaO and Fe₂O₃ on urea oxidation.

Short-Term Effect of Fly Ash from Biomass Combustion on Spring Rape Plants Growth, Nutrient, and Trace Elements Accumulation, and Soil Properties

The short-term impact of biomass combustion fly ashes (BAs) fertilization on the spring rape growth, essential and trace elements accumulation in seeds, and selected soil and soil solution properties were analyzed in a pot experiment study. The pot experiment was carried out in the growing season (April-August) during the year 2018. The effect of BAs on the dry matter content in spring rape plants and the relative content of chlorophyll in leaves (SPAD) was analyzed. In addition, the effect of BAs on the accumulation of essential and trace elements in the seeds of this plant was analyzed. The impact of BAs on the basic physicochemical properties of soils was also assessed. Additionally, the solubility of compounds contained in BAs was monitored on the basis of the analysis of the changes in the physicochemical properties of soil solution during the experiment period. The present study demonstrated a positive effect of BAs fertilization on plant growth and development and improvement of soil physicochemical properties. A change has been achieved in the soil reaction class from a slightly acidic (control, NPK) to neutral (D1-D6), with the highest increase in pH induced by the highest ash dose of 3 mg ha^-1 (D6). It was shown that BAs contributed to a significant increase in the content of macroelements than trace elements in the analyzed soil. In turn, the accumulation of these elements in plant seeds exhibited an inverse relationship, which was mainly influenced by the soil pH and the content of N, Ca, Mg, K, and Na in the soil, as indicated by the correlation coefficients. The highest contents of Fe, Mn, Zn, Cu, Cr, and Ni were detected in the seeds of plants fertilized with BAs at a dose of 2.0 Mg ha^-1 (D4), and their respective values were 263, 363, 107, 51, 1835, and 137% higher than in the control. The Ca, Mg, S, and Na compounds introduced with BAs exhibited high solubility, as evidenced by the higher concentration of Ca²⁺, Mg²⁺, Na⁺, and SO₄^2- ions in the soil solutions and the dynamic changes in pH and EC observed during the experiment. The lowest solubility after the application of BAs was exhibited by N and P. The conducted PCA analysis to a large extent explained the variability between the applied fertilization and the factors analyzed in the experiment. Despite the positive impact of ashes, attention should be paid to the potential risks associated with their use. The use of higher doses of BAs may result in excessive alkalization and salinity of soils and may enhance the accumulation of trace elements in plants. These aspects should therefore be closely monitored, especially in the case of a long-term application of these wastes, in order to avoid serious environmental problems.

New trends on green energy and environmental technologies, with special focus on biomass valorization, water and waste recycling: editorial of the special issue

In this editorial piece, the Editors of the Virtual Special Issue (VSI) "New Trends on Green Energy and Environmental Technologies, with Special Focus on Biomass Valorization, Water and Waste Recycling", present summarized data corresponding to the accepted submissions, as well as additional comments regarding the thematic of the VSI. Overall, 83 manuscripts were received, with final publication of those having the highest quality, accepted after peer-reviewing. The Editors think that the result is a set of very interesting papers that increase the knowledge on the matter, and which would be useful for researchers and the whole society.

Effect of Biochar on Metal Distribution and Microbiome Dynamic of a Phytostabilized Metalloid-Contaminated Soil Following Freeze-Thaw Cycles

In the present paper the effectiveness of biochar-aided phytostabilization of metal/metalloid-contaminated soil under freezing-thawing conditions and using the metal tolerating test plant Lolium perenne L. is comprehensively studied. The vegetative experiment consisted of plants cultivated for over 52 days with no exposure to freezing-thawing in a glass greenhouse, followed by 64 days under freezing-thawing in a temperature-controlled apparatus and was carried out in initial soil derived from a post-industrial urban area, characterized by the higher total content of Zn, Pb, Cu, Cr, As and Hg than the limit values included in the classification provided by the Regulation of the Polish Ministry of Environment. According to the substance priority list published by the Toxic Substances and Disease Registry Agency, As, Pb, and Hg are also indicated as being among the top three most hazardous substances. The initial soil was modified by biochar obtained from willow chips. The freeze-thaw effect on the total content of metals/metalloids (metal(-loid)s) in plant materials (roots and above-ground parts) and in phytostabilized soils (non- and biochar-amended) as well as on metal(-loid) concentration distribution/redistribution between four BCR (community bureau of reference) fractions extracted from phytostabilized soils was determined. Based on metal(-loid)s redistribution in phytostabilized soils, their stability was evaluated using the reduced partition index (Ir). Special attention was paid to investigating soil microbial composition. In both cases, before and after freezing-thawing, biochar increased plant biomass, soil pH value, and metal(-loid)s accumulation in roots, and decreased metal(-loid)s accumulation in stems and total content in the soil, respectively, as compared to the corresponding non-amended series (before and after freezing-thawing, respectively). In particular, in the phytostabilized biochar-amended series after freezing-thawing, the recorded total content of Zn, Cu, Pb, and As in roots substantially increased as well as the Hg, Cu, Cr, and Zn in the soil was significantly reduced as compared to the corresponding non-amended series after freezing-thawing. Moreover, exposure to freezing-thawing itself caused redistribution of examined metal(-loid)s from mobile and/or potentially mobile into the most stable fraction, but this transformation was favored by biochar presence, especially for Cu, Pb, Cr, and Hg. While freezing-thawing greatly affected soil microbiome composition, biochar reduced the freeze-thaw adverse effect on bacterial diversity and helped preserve bacterial groups important for efficient soil nutrient conversion. In biochar-amended soil exposed to freezing-thawing, psychrotolerant and trace element-resistant genera such as Rhodococcus sp. or Williamsia sp. were most abundant.