• Energy Research

Plants, and microorganisms associated with them, offer an effective tool for removing pollutants, such as heavy metals, from the soil environment. The aim of this study was to determine changes caused by Ni2+, Co2+, and Cd2+ in the genetic diversity of soil-populating bacteria and the effect these heavy metals on the heating value of elongated coach grass (Elymus elongatus L.) and maize (Zea mays L.). Microorganisms support plants in removing heavy metals from soil. These plants can then be used for energetic purposes. The study aim was accomplished by determining counts of microorganisms and their resistance (RS) to Ni2+, Co2+, Cd2+, their colony development index (CD), ecophysiological diversity index (EP), and diversity established with the next generation sequencing (NGS) method. Further analyses aimed to establish test plants resistance to pollution with heavy metals and their heating value. Organotrophic bacteria turned out to be the most resistant to Co2+, whereas actinobacteria—to Cd2+ effects. At all taxonomic levels, the genetic diversity of bacteria was most adversely influenced by Cd2+ in the soil sown with Zea mays L. Bacteria belonging to Arthrobacter, Rhodoplanes, Kaistobacter, Devosia, Phycicoccus, and Thermomonas genera showed high tolerance to soil pollution with Ni2+, Co2+, and Cd2+, hence they should be perceived as potential sources of microorganisms useful for bioaugmentation of soils polluted with these heavy metals. Ni2+, Co2+, and Cd2+ had no effect on the heating value of Elymus elongatus L. and Zea mays L. The heating value of 1 kg of air-dry biomass of the tested plants was relatively high and ranged from 14.6 to 15.1 MJ. Elymus elongatus L. proved more useful in phytoremediation than Zea mays L.

Cadmium is a non-essential element for proper plant growth and development and is highly toxic to humans and animals, in part because it inters with calcium-dependent processes in living organisms. For this reason, a study was conducted to assess the potential for producing maize (Zea mays) biomass in cadmium-contaminated soil for energy purposes. The energy potential of Zea mays was evaluated by determining the heat of combustion (Q), heating value (Hv), and the amount of energy produced from the biomass. Starch, compost, fermented bark, humic acids, molecular sieve, zeolite, sepiolite, expanded clay, and calcium carbonate were assessed as substances supporting biomass production from Zea mays. The accumulation and redistribution of cadmium in the plant were also investigated. The study was conducted in a vegetation hall as part of a pot experiment. Zea mays was grown in uncontaminated soil and in soil contaminated with 15 mg Cd2+ kg−1. A strong toxic effect of cadmium on the cultivated plants was observed, causing a 62% reduction in the biomass of aerial parts and 61% in the roots. However, it did not alter the heat of combustion and heating value of the aerial part biomass, which were 18.55 and 14.98 MJ kg−1 d.m., respectively. Of the nine substances tested to support biomass production, only four (molecular sieve, compost, HumiAgra, and expanded clay) increased the yield of Zea mays grown in cadmium-contaminated soil. The molecular sieve increased aerial part biomass production by 74%, compost by 67%, expanded clay by 19%, and HumiAgra by 15%, but none of these substances completely eliminated the toxic effects of cadmium on the plant. At the same time, the bioaccumulation factor (BAF) of cadmium was higher in the roots (0.21–0.23) than in the aerial parts (0.04–0.03), with the roots showing greater bioaccumulation.

One of the major challenges faced by contemporary agriculture is how to achieve better yields of crops and, consequently, higher biomass, even in unfavorable environmental conditions. This challenge corresponds to the assumptions of sustainable development, wherein it is envisaged that plant biomass should be used on a large scale for heat generation or conversion of biofuels. Keeping pace with observed trends, the following study was conducted in order to determine the effect of Cr(VI) on the net calorific value of Zea mays, to assess the impact of this element on soil enzymatic activity, and to identify the effectiveness of compost and humic acids in alleviating possible negative effects of Cr(VI) toxicity. These aims were pursued by setting up a pot experiment, in which soil either uncontaminated or contaminated with increasing doses of Cr(VI) of 0, 15, 30, 45, and 60 mg Cr kg−1 d.m. was submitted to biostimulation with compost and the preparation HumiAgra, a source of humic acids, and cropped with Zea mays. The plant height, yield, and net calorific value of the aerial parts of maize, as well as its root yield, were determined. Additionally, the activity of seven soil enzymes and the values of the impact indices of compost and HumiAgra relative to the analyzed parameters were determined. It was found that Cr(VI) decreased the amount of energy obtained from the plants by decreasing maize biomass, and additionally by distorting the biochemical balance of the soil. Dehydrogenases, urease, and arylsulfatase proved to be particularly sensitive to this element. It was demonstrated that HumiAgra was more effective than compost in mollifying the adverse effects of Cr(VI) on the activity of soil enzymes and, consequently, on the biomass of Zea mays.

Cadmium is an essential element for plant growth and development. Its accumulation in soil is more hazardous to human and animal health than to plants and microorganisms. A pot greenhouse experiment was conducted to determine the usability of Sinapis alba L. and Avena sativa L. for the phytoremediation of soil contaminated with cadmium and to verify cellulose viability in the remediation of soil under cadmium pressure in doses from 4 to 16 mg Cd2+ kg−1 soil d.m. (dry matter) The effect of cadmium on soil microbiome was investigated with the culture method and the variable region sequencing method. Sinapis alba L. and Avena sativa L. were found viable in the phytoremediation of soil contaminated with Cd2+. Avena sativa L. was more potent to accumulate Cd2+ in roots than Sinapis alba L. Although the fertilization of Cd2+- contaminated soil with cellulose stimulated the proliferation of microorganisms, it failed to mitigate the adverse effects of Cd2+ on bacterial diversity. Bacteria from the Sphingomonas, Sphingobium, Achromobacter, and Pseudomonas genera represented the core microbiome of the soils sown with two plant species, contaminated with Cd2+ and fertilized with cellulose. Stimulation of the growth and development of these bacteria may boost the efficacy of phytoremediation of cadmium-contaminated soils with Sinapis alba L. and Avena sativa L.

The aim of this study was to determine the effect of three active substances, diflufenican, mesosulfuron-methyl and iodosulfuron-methyl-sodium, applied in combination, on soil microbial counts, the structure of soil microbial communities, activity of soil enzymes and their resistance to the tested product, the biochemical indicator of soil fertility, and spring wheat yield. Soil samples with the granulometric composition of sandy loam with pHKCl 7.0 were used in a pot experiment. The herbicide was applied to soil at seven doses: 0.057 (dose recommended by the manufacturer), 1.140, 2.280, 4.560, 9.120, 18.240 and 36.480 mg kg(-1) soil DM. Uncontaminated soil served as the control treatment. It was found that a mixture of the tested active substances increased the counts of total oligotrophic bacteria and spore-forming oligotrophic bacteria, organotrophic bacteria and actinomycetes, decreased the counts of Azotobacter and fungi, and modified the structure of soil microbial communities. The highest values of the colony development (CD) index and the ecophysiological (EP) index were observed in fungi and organotrophic bacteria, respectively. The herbicide applied in the recommended dose stimulated the activity of catalase, urease and acid phosphatase, but it had no effect on the activity of dehydrogenases, alkaline phosphatase, arylsulfatase and β-glucosidase. The highest dose of the analyzed substances (36.480 mg kg(-1)) significantly inhibited the activity of dehydrogenases, acid phosphatase, alkaline phosphatase and arylsulfatase. The values of the biochemical soil fertility indicator (BA21) decreased in response to high doses of the herbicide. Urease was most resistant and dehydrogenases were least resistant to soil contamination with a mixture of diflufenican + mesosulfuron-methyl + iodosulfuron-methyl-sodium. The analyzed herbicide had an adverse influence on spring wheat yield, and doses of 18.240 and 36.480 mg kg(-1) led to eventual death of plants.

Soil contaminated with petroleum-derived products should be used to cultivate energy crops. One such crop is Zea mays. Therefore, a study was performed to determine the suitability of Zea mays biomass obtained from gasoline-contaminated soil for energy purposes. The analysis included determining the heat of combustion and calorific value of the biomass, as well as the content of nitrogen, carbon, hydrogen, oxygen, sulfur, and ash in the biomass. Additionally, the suitability of vermiculite, dolomite, perlite, and agrobasalt for the phytostabilization of gasoline-contaminated soil was evaluated. It was found that the application of sorbents to gasoline-contaminated soil significantly reduced the severe negative effects of this petroleum product on the growth and development of Zea mays. Gasoline contamination of the soil caused a significant increase in ash, nitrogen, and sulfur, along with a decrease in carbon and oxygen content. However, it had no negative effect on the heat of combustion or calorific value of the biomass, although it did reduce the energy production from Zea mays biomass due to a reduction in yield. An important achievement of the study is the demonstration that all the applied sorbents have a positive effect on soil stabilization, which in turn enhances the amount of Zea mays biomass harvested and the energy produced from it. The best results were observed after the application of agrobasalt, dolomite, and vermiculite on gasoline-contaminated soil. Therefore, these sorbents can be recommended for the phytostabilization of gasoline-contaminated soil intended for the cultivation of energy crops.

Ensuring a stable and cost-effective energy supply is a major challenge for the International Energy Agency (IEA). Additionally, the effectiveness of vermiculite and dolomite in mitigating the adverse effects of diesel oil, a petroleum-derived product, on plant growth and development, and on the biochemical activity of the soil, were assessed. Therefore, an attempt was made in the study to determine the energy properties of Zea mays, which is suitable for cultivation in contaminated areas. For these purposes, several parameters were analyzed in its biomass, including calorific value (Q), heating value (Hv), energy yield (Yep), ash content, and the presence of carbon (C), hydrogen (H), sulfur (S), nitrogen (N), and oxygen (O). Biochemical activity was measured through the evaluation of soil enzymes serving as indicators for the carbon (dehydrogenases, catalase, β-glucosidase), nitrogen (urease), sulfur (arylsulfatase), and phosphorus (acid and alkaline phosphatase) cycles. The plant greenness index was also determined. It has been demonstrated that diesel oil does not alter the calorific value of Zea mays biomass but significantly reduces the biomass quantity and destabilizes the biochemical properties of the soil. Zea mays contained an average of 6.84% ash, 49.88% C, 5.65% H, 0.17% S, 2.90% N, and 34.57% O. The calorific value of Zea mays ranged from 15.02 to 15.54 MJ kg−1 d.m. of plants, and the heating value ranged from 18.25 to 19.21 MJ kg−1 d.m. of plants. The biomass obtained from contaminated soil is recommended for energy purposes. The sorbents used—vermiculite and dolomite—proved to be less effective in the remediation of soil contaminated with diesel oil.