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Article

Improving the Biomass Energy Yield of Cocksfoot Cultivated on Degraded Soil Amended with Organic–Mineral Fertilizer

by
Urszula Wydro
1,*,
Elżbieta Wołejko
1,
Jolanta Joniec
2,
Agata Bober
3 and
Mariola Chomczyńska
3
1
Department of Chemistry, Biology and Biotechnology, Faculty of Civil Engineering and Environmental Sciences, Bialystok University of Technology, Wiejska 45E Str., 15-351 Białystok, Poland
2
Department of Environmental Microbiology, Faculty of Agrobioengineering, University of Life Sciences in Lublin, Leszczyńskiego 7 Str., 20-069 Lublin, Poland
3
Faculty of Environmental Engineering, Lublin University of Technology, Nadbystrzycka 40B Str., 20-618 Lublin, Poland
*
Author to whom correspondence should be addressed.
Energies 2025, 18(5), 1165; https://doi.org/10.3390/en18051165
Submission received: 4 February 2025 / Revised: 20 February 2025 / Accepted: 25 February 2025 / Published: 27 February 2025
(This article belongs to the Special Issue Energy from Waste: Towards Sustainable Development and Clean Future)
Browse Figures
Versions Notes

Abstract

:
The current difficult political and economic situation generates the need to seek new sources of energy, and the solution may be to increase biomass of energy crops through using organic–mineral wastes to improve soil quality. The research objectives were to determine the effect of coal gangue (CG) and sewage sludge (SS) based organic–mineral fertilizer (OMF) application on cocksfoot growth and subsequently on biogas and methane production. First, a 6-week vegetation experiment was conducted where degraded soil (DS) taken from the edge of a sand mine in Rokitno was amended with OMF at 1% (DS + 1), 2%, 5%, and 10%. Cocksfoot was sown on such prepared soils. At the end of the first stage of the experiment, plant and soil samples were collected. In cocksfoot, dry shoot and root biomass were determined. The main soil properties and soil dehydrogenases, alkaline phosphatase (ALP), acid phosphatase (ACP), and protease (PROT) activities were analyzed. Next, an anaerobic fermentation experiment was conducted. In batch assay of digestion, cocksfoot collected from arable soil (CS) and from DS + 1% was used. Concerning the pot experiment, there was higher PROT in DS + 5% (by 133%) and DS + 10% (by 417%) compared to CS, and ALP in DS + 10% was higher by 19% than in CS. Shoot dry matter in OMF-amended DS was 107–297% higher than in CS. Among the fermentation experiment, the greatest differences (20–37%) in average daily biogas production between CS and DS + 1% were observed at 2–4 days but methane content in biogas in both variants was similar. Summarizing, fertilizer based on SS and CG can be a valuable substrate for degraded soil and increase in energy crops biomass.

1. Introduction

Due to the progress of civilization and the increasing population, the amount of waste generated is increasing [1]. According to EU legislation, not all waste can be disposed of in landfills. This applies mainly to organic waste, for example, sewage sludge [2]. The diversity of waste combined with a lack of adequate infrastructure makes it difficult to recycle, convert, or dispose of it [3]. Some types of waste have properties that make it possible to produce products useful in various sectors, such as fertilizers needed for agriculture. Such activities not only eliminate the problem of accumulating waste but also satisfy the market demand for products.
According to the data provided by the EU [4], in 2022, mining and quarrying was ranked second in terms of waste generated and accounted for 22.7% of total waste produced. Romania generated the highest percentage of this type of waste (85.2%), while Poland produced 36.5%.
Mining waste includes coal gangue (CG), which is associated with the process of extracting useful minerals, mainly coal. In the case of the “Bogdanka Coal Mine” (Poland), CG is mined at a rate of approximately 4 million tons per year and is a significant problem for a mine [5]. In countries where mining and coal extraction is an important part of the economy (including Poland), national strategies and regulations related to coal gangue disposal and management have been developed [6]. CG is a mineralogically heterogeneous geological formation, consisting mainly of sandstone and clay rocks. Its occurrence in the vicinity of coal and other valuable deposits results in the occurrence of elements similar to it [7]. In general, the following are present in the CG: macro- and micronutrients (K, Ca, Mg, S, Fe, Mn, Zn, Cu, Co, B, and Mo), rare earth elements and radioactive elements (i.e., radium, thorium and uranium), and heavy metals and numerous oxides, such as silicon (IV) oxide, calcium oxide or aluminum (III) oxide [8,9,10,11]. The chemical composition of CG depends mainly on its origin and may change over time. In general, highest amounts of SiO2 (approx.58%) and Al2O3 (approx. 30%) are observed in CG, along with smaller amounts of Fe2O3 (4–7%), K2O (approx. 4%), MgO (approx. 1.25%), and CaO (approx. 2%). The carbon content of raw CG is about 2.61% [12,13]. According to Luo et al. [14], the organic matter content of CG is 2 to 10 times higher than in soil. The rich composition of CG provides a reason to use this waste as a component for fertilizing degraded soils for growing crops not intended for human or animal consumption, such as energy crops, whose biomass can be used for biogas production. An example is the use of CG under cocksfoot to increase its biomass, which can then be used for biogas and methane production. Cocksfoot is suitable for biogas production, but its effective use for energy depends on the yield and quality of its biomass (chemical composition), which can be regulated by proper fertilization and providing environmental conditions [15,16]. In general, ideally, the productivity of plants should be as high as possible with the lowest possible energy input in the biogas production process to ensure a positive energy balance [17].
There is an increasing amount of research into the use of CG as a fertilizer for soil improvement, which is being conducted in various geographic areas, including outside Europe [18]. Moreover, many studies are using mixtures of CG with other components or waste materials [8,19,20,21]. Combining the mentioned additives with CG is intended to neutralize the acidity of CG [10]. During the mining process, the pyrite and other sulfides contained in the CG are oxidized by processes associated with the presence of rainwater and microorganisms, resulting in the production of large quantities of sulfate and hydrogen ions, which are responsible for the acidic nature of CG [22]. In addition, studies indicate the composition of CG is variable over time and has different proportions of elements necessary for plant growth. Hence, it is important to replenish missing elements, e.g., by applying organic waste [10]. A solution to improve soil quality can be the application of sewage sludge. It is a source of organic matter and nutrients for plants [23]. Due to the properties of sewage sludge, it cannot be stored in landfills; hence, it requires alternative methods of management [2]. One of the parameters limiting the use of sewage sludge in the environment is the above-normal content of heavy metals, but in the case of small wastewater treatment plants from non-industrial areas, this problem is negligible, so they can be used, for example, for land reclamation and growing plants for energy purposes [24].
The second consequence of unsustainable economic development is soil degradation. This process results in the disappearance of naturally valuable areas and agricultural areas [25,26]. In order to restore the land to good condition, various treatments are carried out to improve its physical and chemical properties. One of them is to make plantings of vegetation resistant to conditions in the area. Such action protects the land from further degradation and, after a longer period of time, allows for the restoration of optimal soil conditions [27,28]. For this purpose, energy crops can be used, which not only allow for land reclamation, but also serve as a renewable substrate for energy production [29]. In addition, the cultivation of these plants on degraded land makes it possible to leave larger areas of soil of better quality, which can be used to grow crops for food or feed production [30]. Combining the cultivation of plants on degraded areas with the use of products created from waste, such as fertilizers from sewage sludge and waste rock, and using the resulting biomass to generate energy, is a combination of many areas relating to the idea of a closed loop, a major goal of sustainable development. However, it is important that the waste used is characterized by a low content of heavy metals, which are detrimental to the environment and its processes, and may pose risks to human health [31,32].
The innovative character of the presented study concerns the use of degraded soils previously supplemented with new organic–mineral fertilizer—Slafer (based on sewage sludge and CG)—for growing energy crops (cocksfoot). Accordingly, the hypothesis assumes that the application of organic–mineral fertilizer in different doses to degraded soil will improve the quality and productivity of the soil including higher cocksfoot biomass, which will be reflected in an increase in methane and biogas production. Thus, this study aimed to (1) determine the effect of increasing Slafer dose on cocksfoot growth and on enzymatic activity of degraded soil, and (2) determine the biogas and methane yield obtained for cocksfoot biomass after its growth on degraded soil supplemented with the selected Slafer dose.

2. Materials and Methods

2.1. Experiment Design

The experiments were carried out in two main stages (Figure 1). In the first stage, a vegetation experiment was performed to assess the impact of the addition of organic–mineral fertilizer to degraded soil as a material with reclamation potential. The second stage was a methane fermentation study to determine the biogas production parameters from the substrates in the form of plant biomass growing on arable soil and degraded soil enriched with the selected organic–mineral fertilizer additive.

2.2. Vegetation Experiment Design

2.2.1. Soil and Mineral-Organic Waste Characteristics

Two types of soil were used in the experiment. The first soil was arable soil as a control soil (CS) classified as loamy dust (Alfisols according to USDA soil taxonomy), originating from Czesławice (51°18′24″ N, 22°16′04″ E). The second soil was degraded soil (DS) collected from the edge of slope after sand mining in Rokitno (51°23′40″ N, 22°41′36″ E), classified as Spodosols according to USDA soil taxonomy. The properties of the soils used in the study are summarized in Table 1. The degraded soil was very acidic and had very low potassium and phosphorus contents, medium content of magnesium, as well as an insufficient nitrogen amount regarding plant needs. The arable soil was acidic and was characterized by very high phosphorus, as well as high potassium and magnesium contents. The content of nitrogen was greater than in degraded soil, but it was not sufficient in terms of plant needs; hence, the arable soil could be described as that of medium quality.
Organic–mineral fertilizer (OMF), which is a mixture of stabilized sewage sludge from the Maszewo Wastewater Treatment Plant and CG from coal mining at the Lubelski Węgiel “Bogdanka” S.A. (Bogdanka, Poland), supplemented with 1% beneficial microorganisms (Bacillus sp.), was used as a substrate to improve the quality of degraded soil. The fertilizer was prepared by the company TAYLOR Sp. z o.o. (Lublin, Poland). The main characteristics of the OMF are shown in Table 1.
The OMF contained significantly higher amounts of available forms of nitrogen (N-NH4 and N-NO3), phosphorus, potassium, and magnesium than DS and CS. The total contents of heavy metals in the OMF (Cd, Cr, Cu, Ni, Pb, Zn, and Hg) did not exceed the limits set for organic–mineral fertilizers and sewage sludge by Polish legislation [33,34].

2.2.2. Preparation of Pot Experiment and Plant Growth Condition

This study was conducted as a pot experiment for six weeks. Cocksfoot (Dactylis glomerata) was used as the energy crop, which was grown in a phytotron under the following conditions: 13/11 photoperiod, 25 ± 1/16 ± 1 °C day/night temperature. The crop was cultivated on CS, DS soil, and a mixture of DS and OMF at the following soil/fertilizer (v/v) ratios: 1% OMF, 2% OMF, 5% OMF, and 10% OMF. The dose of 10% (v/v) was chosen as the highest, because it was expected that the use of even higher doses would not lead to an increase in the yield of the aboveground biomass of plants. Finally, the following research variants were obtained: CS (positive control, agricultural soil), DS (degraded soil), DS + 1% (degraded soil and 1% of OMF), DS + 2% (degraded soil and 2% of OMF), DS + 5% (degraded soil and 5% of OMF), and DS + 10% (degraded soil and 10% of OMF). Since soil pH is one of the factors that determine plant development, calcium carbonate was used to regulate the pH of the degraded soil in order to obtain the same pH conditions as in the arable soil. Thus, during preparation of media variants, CaCO3 was mixed with DS (in the dose of 66 mg per 100 g of soil) to adjust its pH to CS pH level.

2.2.3. Soil Preparation and Analysis of Soil Properties

The soil/substrate samples from each study variant were mixed and sieved through a 2 mm mesh sieve. Three subsamples were taken from the soil thus prepared. The soils for physicochemical analyses, i.e., pH, TOC, TN, micronutrients, and heavy metals, were dried to an air-dry mass and then stored in airtight containers for further analyses. The soil samples for enzyme activity analysis with field moisture content were stored at 4 °C.
The values of pH were determined potentiometrically in 1 M KCl solution using an Elmetron CPC 501 pH meter (Elmetron, Zabrze, Poland) equipped with a combined EPS-1 electrode [35]. The heavy metal content in the soil was analyzed using an inductively coupled plasma mass spectrometer Agilent 8900 ICP-MS Triple Quad (Agilent Technologies, Inc., Santa Clara, CA, USA) after mineralization with aqua regia. TOC was analyzed using RC 62 LECO apparatus (LECO, Tychy, Poland) after ignition of the samples at 450 °C. TN was measured with KjeltecTM 8200 Foss Tecator system (FOSS Analytical, Hilleroed, Denmark) where samples were mineralized with H2SO4 (95%) in the presence of potassium sulphate, copper sulphate, and Devarda’s alloy at 420 °C.
To determine the reclamation effect of OMF on the tested soil, dehydrogenase (DHA), protease (PROT), acid phosphatase (ACP), and alkaline phosphatase (ALP) activities were examined. DHA activity was determined colorimetrically according to the method described by Thalmann [36] with a TTC as a substrate, and results were expressed as mg triphenylformazan (TPF) per kg soil dry weight per day (mg TPF/(kg dm × d)). Protease activity was determined according to the method of Ladd and Buttler [37]. Casein sodium salt was used as substrate and results were given as mg tyrosine per kg soil dry weight per 1 h (mg tyrosine/(kg dm × h)). ACP and ALP activity was determined colorimetrically according to the assay given by Tabatabai and Bremner [38] and results were expressed as mg p-nitrophenol (pNP) per kg soil dry weight for 1 h (mg pNP/(kg dm × h)). Enzyme activity was measured on a UV 1800 spectrophotometer (Rayleigh, Beijing, China). All analyses were performed in triplicate.

2.2.4. Plant Preparation and Analysis of Plant Properties

After the pot experiment, plant shoots were cut, and roots were isolated from the pots containing the substrates of the different research variants.
In order to determine the productivity of the substrate after the addition of different doses of OMF to DS, the fresh and dry weight of shoots and the dry weight of roots were determined according to the assay described by Ostrowska et al. [35].

2.3. Methane Fermentation Study

For the anaerobic digestion experiment, plant feedstock was used from the CS research variant. Out of the studied variants (with 1%, 2%, 5%, and 10% v/v OMF addition), DS + 1% exhibited average dry shoot biomass that was quantitatively closest to that collected from the arable soil (CS). Therefore, the shoot biomass from the DS + 1% variant was also employed for the experiment. The shoot biomass as process substrate was obtained from a subsequent 6-week vegetation cycle of cocksfoot on the substrates of the aforementioned research variants carried out under identical conditions, as described in Section 2.2.2.

2.3.1. Analysis of Plant Biomass as a Feedstock to Fermentation

Plant biomass as a substrate for the methane fermentation process was analyzed to determine total nitrogen (TN), total organic carbon (TOC), volatile solids (VS), proteins, and monosaccharides. In addition, fiber fractions were investigated in the plant material: acid detergent fiber (ADF), neutral detergent fiber (NDF), and acid detergent lignin (ADL). Methods for the determination of these parameters are described in Section 2.2.3 and in Chomczyńska et al. [39]. All analyses were performed in triplicate.

2.3.2. Batch Experiment Design

Batch assay of anaerobic digestion of plant biomass was conducted in BioReactor Simulator (BRS) equipment (BPC Instruments AB, Lund, Sweden), which contained six bioreactors and was equipped with a system for mixing feedstocks. In the test, preincubated digestate from the biogas plant located in Piaski (Lublin, Poland) was used as inoculum. Its initial pH was 8.2 ± 0.1.
The process was performed in three replicates. The temperature of the process was maintained at 37 °C. To each bioreactor, 1200 cm3 of digestate and the sample of fresh, crushed plant biomass was introduced (in dose of 4–5 g of dry matter). Then, the bioreactors were closed and flushed with the N2 gas to remove oxygen. Digestion of plant biomass continued for 36 days. During the process, a gas volume analyzer (a subunit of BRS system) measured the volume of produced biogas. The obtained data were standardized to normal conditions. The chemical composition of biogas (including methane content) was examined by use of Trace GC Ultra gas chromatograph with TCD detector (Thermo Scientific, Waltham, MA, USA) at the end of the experiment.

2.3.3. Biogas Production Analysis

The data obtained as a result of batch assay were used for calculating the biogas potential (BGP), methane potential (BMP), and energetic potential (SE) of cocksfoot biomass according to the formulas presented in the study by Chomczyńska et al. [39].

2.4. Data Analysis

The obtained results were statistically processed using basic descriptive statistics. Results are presented as mean ± standard deviation (SD) or, in the case of enzymatic soil activity, mean ± SE (standard error of mean). In the case of comparing two mean values (main characteristics of plant biomass as a feedstock for the digestion process and biogas, methane, and energetic potential), Student’s t-test was used. An ANOVA was used when more than two means of studied parameters were compared, and significant differences were taken at α < 0.05. The assumptions of the analysis of variance (normality of distribution and homogeneity of variance) were verified. When different variances were recorded, means were compared using Tamhane’s T2 test. In the cases where the homogeneity of variance assumptions were met, differences between the means were assessed with the Tukey test at p < 0.05.
Pearson’s correlation analysis (for p < 0.05) was performed for the studied parameters, while the relationships between the studied variables were presented as a correlation matrix. Data were processed using the R environment (4.4.1) and R Studio (ver. 2024.09.0 + 375) [40].

3. Results

3.1. Physicochemical Soil Properties in Vegetation Experiment

Figure 2 presents the main soil properties, i.e., pH, TOC, and TN content, in the considered study variants. The soil pH was recorded to range from 5.23 (DS) to 5.87 (DS + 10%). The pH in DS + 5% and DS + 10% was significantly higher than in CS, where it was 5.52. In our study, the lowest TOC content was reported in DS (0.52%), while the highest in DS + 10% (1.33%). Only in the case of DS + 10% was the soil TOC content significantly higher than in CS (0.73%). As for TN, its content in the conducted study ranged from 0.057% (DS + 5%) to 0.133% (DS + 10%). It was also observed that the TN content in CS was significantly lower by 46% than in DS + 10%. In the other variants with OMF supplement (1%, 2%, and 5%), the TN content was significantly lower than in arable soil (CS) and similar to DS.

3.2. Content of Micronutrients and Heavy Metals in Soil

As shown in Figure 3, the content of macronutrients such as Mn, Mo, Co, and Fe in the soil varied depending on the study variant. For Mn, it was noted that in DS + 1%, DS + 2% and DS + 5% its content was significantly lower than in CS. Considering Mo, its content in DS + 5% and DS + 10% was significantly higher than in CS. The average Co content in CS was significantly higher than in DS, DS + 1%, and DS + 5%. In contrast, the Fe content in DS + 10% was significantly higher than in DS. The highest Fe content was recorded in CS.
Figure 4 provides the content of the main heavy metals in the soil, i.e., Cd, Cr, Cu, Ni, Pb, and Zn. Their content in the soil varied with the OMF dose. It was revealed that in DS + 10%, the content of Cd, Cr, Cu, Ni, and Zn was significantly higher than in DS. Furthermore, the Zn content in DS + 10% was significantly higher than in CS.

3.3. Activity of Soil Enzymes

Figure 5 indicates the activities of DHA, PROT, ACP, and ALP in the studied soil. DHA activity in the soil ranged from 0.24 (DS) to 1.33 mg TPF/(kg dm × d) (DS + 10%). It was demonstrated that DHA activity in DS + 10% was significantly higher by 81%, 82%, and 61% than in DS + 1%, DS + 2%, and DS + 5%, respectively. Furthermore, it was observed that at the highest OMF dose (10%), DHA activity was 42% higher than in CS, but these differences were not statistically significant (for p < 0.05).
In the conducted study, PROT activity ranged from 2.56 (DS) to 39.36 mg tyrosine/kg dm/h) (DS + 10%). It was observed that PROT activity in DS, DS + 1%, and DS + 2% had no significant difference compared to CS, where it was 7.61 mg tyrosine/(kg dm × h). Furthermore, PROT activity in arable soil (CS) was significantly lower at 57% and 81% compared to DS + 5% and DS + 10%, respectively.
The lowest ACP activity was in DS + 10% (154.32 mg pNP/(kg dm × h)), while the highest was in CS (205.64 mg pNP/(kg dm × h)). Furthermore, it was noted that the ACP activity in DS + 5% was similar to CS and was 193.45 mg pNP/(kg dm × h), while the ACP activity in DS + 10% had a similar value to DS (158.42 mg pNP/(kg dm × h)).
According to the obtained results, ALP activity ranged from 2.86 (DS) to 54.64 mg pNP/(kg dm × h) (DS + 10%). It was observed that the ALP activity obtained in DS + 1%, DS + 2%, and DS + 5% was significantly lower by 80%, 30%, and 31%, respectively, than in CS, where it was 45.84 mg pNP/(kg dm × h). Moreover, ALP activity in all variants with OMF supplementation was significantly higher than in DS.
The activity of the soil enzymes studied was mainly influenced by the soil micro- and macronutrient content (Figure 6). Positive significant correlations were recorded between soil pH, TOC, and TN content and ALP, DHA, and PROT activity, with correlation coefficients r ranging from 0.64 to 0.93. It was also observed that Mo, Cu, and Zn positively correlated with DHA, PROT, and ALP activity. In addition, ACP showed a positive correlation with Fe, Co, Pb, Cd, Cr, and Zn.

3.4. Plant Properties in Vegetation Experiment

To determine the productivity of soils after the application of different OMF doses, dry shoot biomass, dry root biomass, and fresh shoot biomass of cocksfoot were estimated, as shown in Figure 6. In the conducted study, it was observed that the highest dry shoot biomass was at DS + 5% and DS + 10% and was 0.96 and 0.88 g/pot, respectively. The lowest shoot dry biomass was recorded in DS (0.15 g/pot). In DS + 1% and DS + 2%, shoot dry matter was significantly higher than in CS and DS. As for root dry matter, it ranged from 0.24 (DS) to 0.56 g/pot (DS + 2%). It was also reported that in DS + 1%, DS + 2%, and DS + 5%, root dry matter was significantly higher than in CS, DS, and DS + 10%. When considering fresh plant biomass, the highest was obtained with DS + 5% (6.91 g/pot) and the lowest with DS (0.77 g/pot). In all OMF-supplemented soils, the fresh shoot biomass content was significantly higher than in the arable soil (CS).

3.5. Correlation Analysis of Studied Parameters in Vegetation Experiment

As shown in Figure 7, the accumulation of shoot dry biomass, root biomass, and shoot fresh biomass was significantly correlated with soil enzyme activity and soil properties, including soil micro- and macronutrient content. Negative significant correlations were recorded between soil Mn and TN content and root dry weight (r = −0.58 and r = −0.52, respectively), as well as between shoot dry weight and soil Mn content (r = −0.50). Positive correlations were observed between dry shoot biomass and fresh shoot biomass and ALP and PROT activity, as well as with pH and TOC content in the medium. Furthermore, positive correlations were observed between dry shoot biomass and fresh shoot biomass as well as Mo and Zn content.

3.6. Characteristic of Plant Biomass as a Feedstock in Batch Experiment

In Table 2, the main characteristics of cocksfoot considered for the anaerobic digestion process are summarized. The results showed that parameters such as TN, VS, protein content, C/N ratio, and monosaccharide content differed significantly in the compared research variants. In the case of TN, VS, protein amount, and monosaccharide content, higher values were found for DS + 1%, while in the case of C/N ratio, a higher average value was recorded for CS. The content of NDF and HCE in cocksfoot with DS + 1% was higher than in CS, but the differences were not statistically significant. Similarly, there were no significant differences in ADF, ADL, and CE contents between cocksfoot biomass obtained in the DS + 1% and CS variants.

3.7. Biogas and Methane Yield from Cocksfoot Biomass

The mean daily production of biogas from the cocksfoot biomass obtained on arable soil and on degraded soil with added 1% of OMF is presented in Figure 8. It is seen that biogas production in bioreactors of both variants (CS and DS + 1%) had already started on the first day of the process, and on this day, it was the highest. Biogas production in bioreactors with plant biomass of DS + 1% on the first day of the process was 13% of the final biogas amount while biogas production in CS was −12.7%. On the second day of the process, the noticed decrease in biogas production in both test series had appeared, but on the third and fourth day, biogas production increased again. After the fourth day, the biogas generation in the bioreactors started to decrease. The last noticed increase in biogas production was observed on the 10th day of the process. After 31st–32nd day (in which biogas production was almost equal to 0), a little biogas generation was observed again but it was so low that it was decided to terminate the test after 36 days from the moment of its start. The highest differences in mean daily biogas production between the test variants were observed during the first days of the biomass digestion (2nd–4th day of the process)—from 20% to 37%.
Biogas and methane yield and specific energy of cocksfoot biomass obtained on both studied soils are shown in Table 3. BGP, BMP, and SE of biomass harvested on arable soil (calculated per g of TS and VS) were significantly higher than those determined for biomass of plants growing on degraded soil supplemented with the 1% OMF dose. However, the differences between the compared parameters were numerically not great and amounted to 8–13%. It is worth noting that the methane content in biogas produced from both feedstocks was practically the same.

4. Discussion

4.1. Organic–Mineral Waste as a Substrate to Improve Soil Quality

According to the literature, there are gaps regarding the effect of organic–mineral fertilizer based on sewage sludge and coal gangue. Furthermore, the effect of each substrate as a single ingredient may vary depending on the origin, the treatment method, and their composition [10,41].
Previous studies report that the separate application of sewage sludge and CG to the soil can affect soil pH. The direction of changes depends mainly on the characteristics of the substrates, their origin, treatment, and the properties of the soil itself. Sewage sludge can both lower and raise the pH in soils. It is often observed that sludge causes an increase in pH in acidic soils due to the use of calcium carbonate in the sludge stabilization process. A decrease in pH, on the other hand, can result from the release of acids during sewage sludge decomposition [41]. Referring to CG, data in the literature mention that CG can release acidic leachate with low pH when exposed to prolonged weathering or the presence of rainwater; thus, the soil amended with CG may show lower pH [10]. Therefore, it seems more reasonable to apply CG to alkaline soils. In this study, there was an increase in pH (measured in 1 M KCl) in degraded soil after the application of OMF at a dose of 5% and 10%. It can be assumed that this is the cumulative effect of the application of a fertilizer, the pH of which is optimal for plant growth. The combination of two waste materials, sewage sludge (usually neutral to alkaline pH) and waste rock (acidic pH), provides a rational solution for minimizing the adverse properties of CG and allowing for the fertilizer to be applied at the optimum pH for plant growth.
The fertility of the soil is characterized, i.e., by its organic carbon content (TOC) and total nitrogen content (TN). Both sewage sludge and CG are rich in these nutrients. On the basis of the study by Lu et al. [21], the organic matter and total nitrogen contents were higher in the CG-enriched soils than in the control. Similar results were obtained by Li et al. [42]. According to the literature data, in soils enriched with sewage sludge, up to a threefold increase in TOC and an increase in TN were noted [43,44,45]. Within this research, the content of TOC as well as TN in the OMF-supplemented soil was higher than in the degraded and control soil, mainly after the application of a 10% dose of OMF, which supports the researchers’ findings regarding the effect of sludge and CG on soil.
In this study, the effect of the addition of OMF on soil enzyme activity was investigated. Soil enzyme activity is an indicator of the health, fertility, and productivity of the soil and at the same time is sensitive to changes in the soil [46]. Research reports indicate that sewage sludge can both inhibit and stimulate enzyme activity in the soil. This is related to their properties, as well as to specific enzymes themselves. [47,48]. DHA activity gives information on the respiratory metabolism of microorganisms and is an indicator providing information on the oxidation of organic matter in the soil. According to the results obtained by Farsang et al. [49], DHA activity decreased in the sludge-enriched soil, which can be explained by the timing of sampling, the presence of heavy metals, and the influence of other factors. Contrastingly, in a study presented by Lakhdar et al. [50], the application of sewage sludge had a positive effect on DHA activity, which was associated with an enrichment of the soil nutrient pool. Considering CG, previous studies indicate that CG-enriched soils have higher soil enzyme activity compared to controls, which is explained by the addition of essential micro- and macroelements that benefit the soil microflora and its activity [18,42].
Bo et al. [51] states that simultaneous application of organic and mineral fertilizers can improve the properties of degraded soils. The results of the conducted study demonstrate that degraded soil enriched with OMF had higher ALP, DHA, and PROT activity after application of the highest dose of 10% (ACP—dose of 5%) compared to the control. It can be hypothesized that this was related to the delivery of micronutrients and macronutrients (i.e., TN, TOC, Zn, Cu, Mo) from OMF, as suggested by the obtained positive correlation coefficients. The obtained results correspond with the reports of the authors mentioned above.

4.2. Organic–Mineral Waste as a Substrate to Increase Biomass Production

Another parameter determining soil fertility and the effectiveness of the use of organic–mineral substrates is the evaluation of soil productivity expressed in the obtained amount of plant biomass (shoots and roots). It should be noted that plant cultivation is one of the most effective methods of restoring degraded land to use [21]. It should be noted that the interaction between plant roots and soil microorganisms plays an important role in this complex process [52]. In areas that are difficult (highly chemically and physically degraded) and subjected to reclamation, it is advisable to grow plants including grasses of energy significance. Cocksfoot is an example of a plant that is resistant to unfavorable environmental conditions, grows on marginal land (including degraded land), and, at the same time, is a valuable input for biogas production [53,54].
In this study, OMF application to degraded soil resulted in an increase in the size of cocksfoot biomass (especially shoot biomass) compared to the control media of arable soil (CS) and degraded soil (DS). The findings obtained by Du et al. [11] support our evidence by reporting that CG added to the soil significantly increased alfalfa yield, which was associated with an increase in soil organic matter and nitrogen content. Luo et al. [14] conducted an experiment on co-composting CG with sewage sludge and tested the effect of the compost product on cabbage growth. The authors showed that the compost enriched the soil with nutrients improved the soil structure and had a positive effect on plant growth. Motesharezadeh et al. [55] studied the effect of introducing CG in maize crops inoculated with mycorrhizal fungi. The highest dry biomass of maize shoot and root was obtained at a CG dose of 10%, while dry matter accumulation of shoot and root was lower at higher dose (20 and 50%). The authors explained that improved soil properties may have had a beneficial effect on dry matter production. They also reported that at higher doses there may have been an imbalance between nutrients and other micro- and macronutrients introduced into the soil with the waste.
In the conducted study, the dry weight content of the cocksfoot shoot was highest at a dose of 5% OMF, while that of the root was highest at a dose of 2%, which may have been due to the combined effect of sewage sludge and CG as a fertilizer. At the same time, there were positive correlations between shoot dry weight and PROT and ALP activity and TOC content. These correlations confirm the function played by soil microorganisms. It is well known that bacteria and fungi play a role in the mineralization processes of organic matter brought in with fertilizers, thereby making elements (e.g., N and P) available to plants. These processes are enzymatic in nature. Correlations of enzymatic activity with yield quantity and quality are reported by Cuiyun et al. [56]. No significant correlation was recorded between root dry matter and TOC and TN content, which does not confirm the reports of Azam [57], who noted that the supply of organic matter to the soil favored better root development. In contrast, a significant correlation was observed between soil Mn content and root dry mass, which could explain the relation obtained and the lower dry mass at the highest fertilizer dose.
Wang et al. [58] presented research on the use of CG-based biochar and other raw materials on seed germination. It was shown that modified CG has the ability to release nutrients slowly and therefore has a beneficial effect on germination and plant growth. In addition, the researchers demonstrated the relationship between soil characteristics and plant quality. Parameters that determine soil fertility, such as the content of organic matter, total nitrogen, available phosphorus, potassium, and the activity of enzymes responsible for the transformation of essential nutrients are of particular importance in plant nutrition, the obtained yield, and plant quality. Enzymes such as phosphatases and ureases transform the organic phosphorus and nitrogen forms into plant-available forms by which they have a special effect on plant growth and thus their productivity.
According to the literature data, CG undergoes various modifications to improve its properties. These may include mechanical, chemical, microbiological, thermal, hydrothermal, and composite modifications. One interesting modification is the use of metabolic processes of microorganisms to degrade the minerals present in the CG, facilitating the release of nutrients and ultimately obtaining biofertilizer [18,59]. For example, arbuscular mycorrhizal fungi or bacteria that solubilize insoluble phosphorus have been used. It should be noted that the microbial approach offers advantages such as low energy consumption, environmental friendliness, and remarkable efficiency, making it worthy of extensive attention and research.
Other CG modifications of fertilizer importance are the selection of particle size (5–8 mm) and particle amount of 30%, which allows for an aggregate structure, crucial for microbial activity and soil fertility [18]. The study by Li et al. [42] also indicates that the fertilizer potential of CG depends on particle size and cover thickness. With a particle size of 0–1 cm and a cover thickness of 8–12 cm, the saturation water content increased by about 55%, the total nitrogen content by 71%, and the urease activity by 17% compared to the initial state, which positively affected the yield of grasses. The results obtained by the authors emphasize the importance of the physical properties of CG when it is used in soil remediation.
Fan et al. [19] applied CG and plant ash amended with Si-K after a process of calcination to saline soils with corn cultivation. The modification improved the availability of Si to plants and slowed the release of K. In addition, a pot experiment showed improved soil properties, including a reduction in pH and an increase in K+ content, which was positively correlated with corn growth indicators.

4.3. Effect of Organic–Mineral Fertilizer on Biogas Production

The course of changes in daily biogas production for both feedstocks was similar during the digestion process. The first peaks in biogas production observed in Figure 8 could be related to degradation of carbohydrates (mono- and disaccharides), which exhibit a higher hydrolysis rate as compared to proteins and lipids [60]. The following peaks (appeared on 5th day of the process) probably were a result of protein decomposition, but the increase in biogas production on the 10th day could have been caused by degradation of non-starch polysaccharides like cellulose and hemicellulose—compounds of raw fiber that are hardly biodegradable [60].
In fact, numerically small differences found between the values of biogas and methane potentials for the tested feedstocks cannot be attributed to the different contents of monosaccharides and proteins in the plant biomass of both research variants. The cocksfoot biomass obtained on arable soil was characterized by a significantly lower content of proteins and monosaccharides (as precursors of CH4) than the biomass of the plants of the DS + 1% variant (Table 2), and despite this, higher potential values were obtained for it (as mentioned earlier by 8–13%). Perhaps the C/N ratio played an important role here, because for the biomass of CS variant, it was in the middle of the values range considered as optimal for anaerobic digestion (20–30) [61], while for biomass of the DS + 1% variant this ratio was the lower limit of the optimal range. The lower value of the C/N ratio in the biomass harvested from degraded soil enriched with 1% OMF resulted from the higher N content (Table 2), which was a consequence of the enrichment of the degraded soil with N introduced with the OMF addition (Table 1).
The comparison of the biogas production characteristics obtained in the present studies with the literature data showed that these values were numerically similar [17,39,62] and sometimes even higher [17,39,62,63]. Obtaining higher values of biogas and methane potential (per g of TS and VS)—most often for biomass of the CS variant—could be caused by the fact that this feedstock was characterized by a higher total content of cellulose and hemicellulose and a more favorable C/N ratio as compared to the cocksfoot biomass used in digestion tests reported in the literature. The fact that the data presented in the literature referred to the cocksfoot biomass harvested at a more advanced growth stage [17,63], in which the biomass contains a higher share of crystalline cellulose that is more difficult to decompose than amorphous cellulose [17], could also be of importance.
Referring to the obtained values of biomass specific energy and the differences found between them (10–13%, Table 3), it is worth noting that the final assessment of energy yield from 1 hectare of cocksfoot cultivation under field conditions on arable soil and on degraded soil enriched with 1% OMF would depend on the yield of plant biomass per hectare. The yield of cocksfoot biomass in field conditions will also depend on the current environmental factors (e.g., temperature, precipitation). If these conditions differ from the optimal ones for cocksfoot cultivation, a decrease in the amount of biomass obtained from a unit of cultivation area can be expected, and thus a decrease in the methane and energy yield. Nevertheless, the results of the pot experiment showed that the dry yield of cocksfoot shoots obtained on degraded soil with 1% OMF was twice as high as on arable soil (Figure 6). Therefore, after conducting the research under field conditions and confirming the amount of obtained biomass yield, it could be expected that the energy yield from 1 ha of cocksfoot cultivation on degraded soil fertilized with 1% OMF is perhaps more beneficial, as compared to that for 1 ha of plant cultivation on selected arable soil.
Growing energy crops as perennial grasses (which include cocksfoot) on degraded lands provides environmental and social benefits. It is believed that cultivation of bioenergy crops reduces water and wind erosion, sequesters soil C, reduces net greenhouse gas emissions, improves soil biodiversity and water quality, as well as reducing competition for land between energy and food production, which improves food security in long term [17,53,64]. The literature indicates a shortage of data relating to the above-mentioned ecosystem services and confirmed under real conditions of energy crop cultivation on degraded soils (e.g., little is known about how wildlife habitat responds to energy crops in which aboveground biomass is removed once or twice a year) [65]. Therefore, an interesting issue in further research with cocksfoot as an energy crop would be to consider the impact of its cultivation on degraded soil with added OMF on selected ecosystem services. An important issue related to the use of cocksfoot as an energy species is determining the profitability of its cultivation. This requires, on the one hand, calculating the costs of cultivation on degraded areas and further processing of biomass for the purpose of producing biogas and, on the other hand, the financial profit resulting from the price of the produced biogas. An attempt to solve this problem in connection with the environmental performance of cocksfoot can be made in future studies using the recommended life cycle method [66].

5. Conclusions

The use of human-made waste for the remediation of degraded soil can address two important issues in today’s world, which are increasing soil degradation and rising energy demand. Fertilizer production based on waste materials, such as sewage sludge and mining waste—coal gangue, which fits into the concept of sustainable development and the related closed-loop economy. The obtained results allow for stating that the fertilizer based on sewage sludge and coal gangue is a valuable substrate that has a positive effect on the content of nutrients in the soil and its enzymatic properties, which is reflected in higher production of shoot and root biomass of cocksfoot. Greater root biomass is a source of organic matter in the soil and thus a substrate for the synthesis of humic compounds improving the physical, chemical, and biological properties of reclaimed soils. In turn, greater biomass of plant shoots constitutes a greater amount of substrate for biogas production in the process of methane fermentation. Under the experimental conditions, the application of 1% of organic–mineral fertilizer to degraded soil enabled obtaining cocksfoot biomass for which, as a substrate in methane fermentation, the biogas and methane potentials obtained were numerically slightly lower than those found for the biomass of cocksfoot growing on the selected arable soil.
The presented studies require supplementation and explanation of important issues related to the effect of organic–mineral fertilizer on the structure of the soil microbial community and the physiological parameters of the plant itself, both in terms of toxicology and biogas production. From the point of view of biogas production, it seems interesting to explain to what extent increasing the dose of OMF introduced into degraded soil would result in an increase in the nitrogen content in plant biomass and thus a decrease in the C/N ratio—a parameter important for the proper course of the methane fermentation process. In order to understand the mechanisms of action and confirm the reclamation potential of the fertilizer used, it is also necessary to carry out an experiment under field conditions. Such an experiment would also allow for the verification of biogas production parameters and would enable the selection of the range of OMF doses, which—after introduction to a given degraded soil—would result in obtaining satisfactory quality of biomass yield and, consequently, energy yield per hectare. Future studies can also concern the effect of cocksfoot cultivation on degraded soil with added OMF on selected ecosystem services. It is also worth conducting analysis of the profitability of growing cocksfoot on degraded soil enriched with OMF additive in combination with the environmental performance of this species.
In summary, the obtained results indicate the practical usefulness of the tested waste-based fertilizer in soil reclamation. In addition, the presented studies provided valuable information, thus bridging the gap in research on a broader approach to the use of OMF (Slafer) in soil remediation, with the aspect of simultaneous acquisition of biomass for energy purposes.

Author Contributions

Conceptualization, M.C. and U.W.; methodology, M.C., U.W., E.W. and J.J.; investigation, M.C., U.W., E.W., A.B. and J.J.; data curation, M.C. and U.W.; writing—original draft preparation, U.W. and M.C.; writing—review and editing, E.W. and J.J.; visualization, U.W.; supervision, M.C. All authors have read and agreed to the published version of the manuscript.

Funding

The research leading to these results has received funding from the commissioned task entitled “VIA CARPATIA Universities of Technology Network named after the President of the Republic of Poland Lech Kaczyński” under the special purpose grant from the Minister of Science contract no. MEiN/2022/DPI/2577 action entitled “In the neighborhood—inter-university research internships and study visits”.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

We would like to gratefully thank TAYLOR Sp. z o.o. for providing the “Slafer” fertilizer for the research presented in this manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Khan, S.; Anjum, R.; Raza, S.T.; Ahmed Bazai, N.; Ihtisham, M. Technologies for Municipal Solid Waste Management: Current Status, Challenges, and Future Perspectives. Chemosphere 2022, 288, 132403. [Google Scholar] [CrossRef]
  2. Przydatek, G.; Wota, A.K. Analysis of the Comprehensive Management of Sewage Sludge in Poland. J. Mater. Cycles Waste Manag. 2020, 22, 80–88. [Google Scholar] [CrossRef]
  3. Abdel-Shafy, H.I.; Mansour, M.S.M. Solid Waste Issue: Sources, Composition, Disposal, Recycling, and Valorization. Egypt. J. Pet. 2018, 27, 1275–1290. [Google Scholar] [CrossRef]
  4. Waste Statistics. Available online: https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Waste_statistics (accessed on 14 February 2025).
  5. Development of a Gangue-Based Fertilizer and Soil Improver Using Beneficial Microorganisms (in Polish). Mapa dotacji. Available online: https://mapadotacji.gov.pl/projekty/744288/ (accessed on 14 February 2025).
  6. Song, W.; Zhang, J.; Li, M.; Yan, H.; Zhou, N.; Yao, Y.; Guo, Y. Underground Disposal of Coal Gangue Backfill in China. Appl. Sci. 2022, 12, 12060. [Google Scholar] [CrossRef]
  7. Hao, Y.; Guo, X.; Yao, X.; Han, R.; Li, L.; Zhang, M. Using Chinese Coal Gangue as an Ecological Aggregate and Its Modification: A Review. Materials 2022, 15, 4495. [Google Scholar] [CrossRef]
  8. Wang, Y.; Liu, M.; Di, Z.; Cao, W.; He, S. Feasibility Analysis of Bacterial-Treated Coal Gangue for Soil Improvement: Growth-Promoting Effects of Alfalfa. Minerals 2024, 14, 676. [Google Scholar] [CrossRef]
  9. Nan, Y.-C.; Yang, Y.-G.; Wang, Z.-Q.; Zhou, Y.; Su, Q.-M. Effects of Coal Gangue on Soil Property and Plant Growth in Mining Area. Ying Yong Sheng Tai Xue Bao 2023, 34, 1253–1262. [Google Scholar] [CrossRef] [PubMed]
  10. Li, Y. Review of Coal Gangue Characteristics and Ecological Restoration Management Technology. IOP Conf. Ser. Earth Environ. Sci. 2021, 781, 032033. [Google Scholar] [CrossRef]
  11. Du, T.; Wang, D.; Bai, Y.; Zhang, Z. Optimizing the Formulation of Coal Gangue Planting Substrate Using Wastes: The Sustainability of Coal Mine Ecological Restoration. Ecol. Eng. 2020, 143, 105669. [Google Scholar] [CrossRef]
  12. Zhang, J.; Chen, T.; Gao, X. Incorporation of Self-Ignited Coal Gangue in Steam Cured Precast Concrete. J. Clean. Prod. 2021, 292, 126004. [Google Scholar] [CrossRef]
  13. Yang, F.; Lv, J.; Zheng, Y.; Cui, J.; Huang, Y.; Cao, X.; Liu, H.; Zhao, L. Enhancement of Coal Gangue Performance by Surface Micro-Crystalline Glaze Derived from Mineral Powder. Sci. Total Environ. 2023, 858, 159986. [Google Scholar] [CrossRef] [PubMed]
  14. Luo, C.; Li, S.; Ren, P.; Yan, F.; Wang, L.; Guo, B.; Zhao, Y.; Yang, Y.; Sun, J.; Gao, P.; et al. Enhancing the Carbon Content of Coal Gangue for Composting Through Sludge Amendment: A Feasibility Study. Environ. Pollut. 2024, 348, 123439. [Google Scholar] [CrossRef] [PubMed]
  15. Muylle, H.; Van Hulle, S.; De Vliegher, A.; Baert, J.; Van Bockstaele, E.; Roldán-Ruiz, I. Yield and Energy Balance of Annual and Perennial Lignocellulosic Crops for Bio-Refinery Use: A 4-Year Field Experiment in Belgium. Eur. J. Agron. 2015, 63, 62–70. [Google Scholar] [CrossRef]
  16. Tilvikiene, V.; Kadziuliene, Z.; Dabkevicius, Z.; Venslauskas, K.; Navickas, K. Feasibility of Tall Fescue, Cocksfoot and Reed Canary Grass for Anaerobic Digestion: Analysis of Productivity and Energy Potential. Ind. Crops Prod. 2016, 84, 87–96. [Google Scholar] [CrossRef]
  17. Butkutė, B.; Lemežienė, N.; Kanapeckas, J.; Navickas, K.; Dabkevičius, Z.; Venslauskas, K. Cocksfoot, Tall Fescue and Reed Canary Grass: Dry Matter Yield, Chemical Composition and Biomass Convertibility to Methane. Biomass Bioenergy 2014, 66, 1–11. [Google Scholar] [CrossRef]
  18. Tang, T.; Wang, Z.; Chen, L.; Wu, S.; Liu, Y. Opportunities, Challenges and Modification Methods of Coal Gangue as a Sustainable Soil Conditioner—A review. Environ. Sci. Pollut. Res. 2024, 31, 58231–58251. [Google Scholar] [CrossRef] [PubMed]
  19. Fan, Y.; Jia, H.; Pino, V.; Wu, H.; Cheng, F. A Si-K-Based Amendment Prepared by Coal Gangue and Plant Ash Could Improve the Growth of Maize Plants in Saline Soils. J. Soil. Sci. Plant Nutr. 2024, 24, 761–774. [Google Scholar] [CrossRef]
  20. Lv, X.; Yang, S.; Deng, J.; Lei, J.; Shu, Z. Formulation of Ferric/Phosphorus Composite Coating on Coal Gangue as a Novel Fertilizer for Enhancing Slow-Release of Silicon and Implication of As, Cr and Pb. J. Environ. Manag. 2024, 354, 120347. [Google Scholar] [CrossRef]
  21. Lu, Y.; Song, C.; Yan, C.; Jin, Z.; Li, Y.; Lai, C.; Wang, D. The Use of Coal Gangue as a Planting Substrate in Arid Mining Areas. Glob. Ecol. Conserv. 2024, 56, e03328. [Google Scholar] [CrossRef]
  22. Zhu, Q.; Ruan, M.; Hu, Z.; Miao, K.; Ye, C. The Relationship between Acid Production and the Microbial Community of Newly Produced Coal Gangue in the Early Oxidation Stage. Microorganisms 2023, 11, 2626. [Google Scholar] [CrossRef] [PubMed]
  23. Kominko, H.; Gorazda, K.; Wzorek, Z. Potentiality of Sewage Sludge-Based Organo-Mineral Fertilizer Production in Poland Considering Nutrient Value, Heavy Metal Content and Phytotoxicity for Rapeseed Crops. J. Environ. Manag. 2019, 248, 109283. [Google Scholar] [CrossRef] [PubMed]
  24. Wydro, U.; Jabłońska-Trypuć, A.; Hawrylik, E.; Butarewicz, A.; Rodziewicz, J.; Janczukowicz, W.; Wołejko, E. Heavy Metals Behavior in Soil/Plant System after Sewage Sludge Application. Energies 2021, 14, 1584. [Google Scholar] [CrossRef]
  25. Brausmann, A.; Bretschger, L. Economic Development on a Finite Planet with Stochastic Soil Degradation. Eur. Econ. Rev. 2018, 108, 1–19. [Google Scholar] [CrossRef]
  26. Shanmugavel, D.; Rusyn, I.; Solorza-Feria, O.; Kamaraj, S.-K. Sustainable SMART Fertilizers in Agriculture Systems: A Review on Fundamentals to In-Field Applications. Sci. Total Environ. 2023, 904, 166729. [Google Scholar] [CrossRef]
  27. Wong, M.H. Ecological Restoration of Mine Degraded Soils, with Emphasis on Metal Contaminated Soils. Chemosphere 2003, 50, 775–780. [Google Scholar] [CrossRef]
  28. Tahat, M.M.; Alananbeh, K.M.; Othman, Y.A.; Leskovar, D.I. Soil Health and Sustainable Agriculture. Sustainability 2020, 12, 4859. [Google Scholar] [CrossRef]
  29. Blanco-Canqui, H. Energy Crops and Their Implications on Soil and Environment. Agron. J. 2010, 102, 403–419. [Google Scholar] [CrossRef]
  30. Monforti, F.; Lugato, E.; Motola, V.; Bodis, K.; Scarlat, N.; Dallemand, J.-F. Optimal Energy Use of Agricultural Crop Residues Preserving Soil Organic Carbon Stocks in Europe. Renew. Sustain. Energy Rev. 2015, 44, 519–529. [Google Scholar] [CrossRef]
  31. El Hafidi, E.M.; Mortadi, A.; Chahid, E.G.; Laasri, S. Optimization of Domestic Wastewater Treatment Using Ferric Chloride Coagulant: Physicochemical Analysis and Impedance Spectroscopy Studies. Water Air Soil. Pollut. 2024, 235, 68. [Google Scholar] [CrossRef]
  32. El Hafidi, E.M.; Mortadi, A.; Chahid, E.G.; Laasri, S. Monitoring of Domestic Wastewater Treatment Via Infiltration Percolation Using Impedance Spectroscopy. Environ. Technol. Innov. 2023, 32, 103421. [Google Scholar] [CrossRef]
  33. Ministry of Agriculture and Rural Development (Ministerstwo Rolnictwa i Rozwoju Wsi). Regulation of the Polish Minister of Agriculture and Rural Development of 18 June 2008 on the Implementation of Certain Provisions of the Act on Fertilisers and Fertilisation; No. 119 Item 765; Ministry of Agriculture and Rural Development (Ministerstwo Rolnictwa i Rozwoju Wsi): Warsaw, Poland, 2008.
  34. Ministry of Agriculture and Rural Development (Ministerstwo Rolnictwa i Rozwoju Wsi). Regulation of the Polish Minister of the Environment of 6 February 2015 on the Use of Municipal Sewage Sludge; Item 257; Ministry of Agriculture and Rural Development (Ministerstwo Rolnictwa i Rozwoju Wsi): Warsaw, Poland, 2015.
  35. Ostrowska, A. Methods for Analysis and Evaluation of Soil and Plant Properties; Dział Wydawnictw IOŚ: Warsaw, Poland, 1991. [Google Scholar]
  36. Zur Methodik der Bestimmung der Dehydrogenaseaktivität im Boden mittels Triphenyltetrazoliumchlorid (TTC)—ScienceOpen. Available online: https://www.scienceopen.com/document?vid=c8eab917-02b4-492d-81f1-da36da3a3458 (accessed on 23 December 2024).
  37. Ladd, J.N.; Butler, J.H.A. Short-Term Assays of Soil Proteolytic Enzyme Activities Using Proteins and Dipeptide Derivatives as Substrates. Soil. Biol. Biochem. 1972, 4, 19–30. [Google Scholar] [CrossRef]
  38. Tabatabai, M.A.; Bremner, J.M. Use of p-Nitrophenyl Phosphate for Assay Of Soil Phosphatase Activity. Soil. Biol. Biochem. 1969, 1, 301–307. [Google Scholar] [CrossRef]
  39. Chomczyńska, M.; Pawłowska, M.; Szczepaniak, O.; Duma, E. Biogas Generation from Maize and Cocksfoot Growing in Degraded Soil Enriched with New Zeolite Substrate. Energies 2022, 15, 377. [Google Scholar] [CrossRef]
  40. R: The R Project for Statistical Computing. Available online: https://www.r-project.org/ (accessed on 28 November 2024).
  41. Singh, R.P.; Agrawal, M. Potential Benefits and Risks of Land Application of Sewage Sludge. Waste Manag. 2008, 28, 347–358. [Google Scholar] [CrossRef]
  42. Li, S.; Li, X.; Qiang, X.; Yu, Z.; Li, H.; Sun, Z.; Li, Q.; He, J.; Han, L.; Zhao, N. Improving Saline–Alkaline Soil and Ryegrass Growth with Coal Gangue Treatments. Plants 2024, 13, 3419. [Google Scholar] [CrossRef] [PubMed]
  43. Achkir, A.; Aouragh, A.; El Mahi, M.; Lotfi, E.M.; Labjar, N.; EL Bouch, M.; Ouahidi, M.L.; Badza, T.; Farhane, H.; EL Moussaoui, T. Implication of Sewage Sludge Increased Application Rates on Soil Fertility and Heavy Metals Contamination Risk. Emerg. Contam. 2023, 9, 100200. [Google Scholar] [CrossRef]
  44. Nyamangara, J.; Mzezewa, J. Effect of Long-Term Application of Sewage Sludge to a Grazed Grass Pasture on Organic Carbon and Nutrients of a Clay Soil in Zimbabwe. Nutr. Cycl. Agroecosyst. 2001, 59, 13–18. [Google Scholar] [CrossRef]
  45. Deviatkin, I.; Lyu, L.; Chen, S.; Havukainen, J.; Wang, F.; Horttanainen, M.; Mänttäri, M. Technical Implications and Global Warming Potential of Recovering Nitrogen Released During Continuous Thermal Drying of Sewage Sludge. Waste Manag. 2019, 90, 132–140. [Google Scholar] [CrossRef]
  46. Joniec, J. Enzymatic Activity as An Indicator of Regeneration Processes in Degraded Soil Reclaimed with Various Types of Waste. Int. J. Environ. Sci. Technol. 2018, 15, 2241–2252. [Google Scholar] [CrossRef]
  47. Wydro, U.; Jankowska, M.; Wołejko, E.; Kondzior, P.; Łozowicka, B.; Kaczyński, P.; Rodziewicz, J.; Janczukowicz, W.; Pietryczuk, A.; Cudowski, A.; et al. Changes in Soil Biological Properties after Sewage Sludge and Pesticide Application in Wheat Cultivation. Appl. Sci. 2022, 12, 11452. [Google Scholar] [CrossRef]
  48. Wieczorek, J.; Gambuś, F.; Baran, A. Heavy Metal Content and Yielding of Italian Ryegrass Cultivated in the Soil Intensively Fertilized with Municipal Sewage Sludges. E3S Web Conf. 2013, 1, 15005. [Google Scholar] [CrossRef]
  49. Farsang, A.; Babcsányi, I.; Ladányi, Z.; Perei, K.; Bodor, A.; Csányi, K.T.; Barta, K. Evaluating the Effects of Sewage Sludge Compost Applications on the Microbial Activity, the Nutrient and Heavy Metal Content of a Chernozem Soil in a Field Survey. Arab. J. Geosci. 2020, 13, 982. [Google Scholar] [CrossRef]
  50. Lakhdar, A.; Scelza, R.; Scotti, R.; Rao, M.A.; Jedidi, N.; Gianfreda, L.; Abdelly, C. The Effect of Compost and Sewage Sludge on Soil Biologic Activities in Salt Affected Soil. Rev. Cienc. Suelo Y Nutr. Veg. 2010, 10, 40–47. [Google Scholar] [CrossRef]
  51. Bo, H.; Li, Z.; Wang, W.; Zhang, R.; Wang, H.; Jin, D.; Xu, M.; Zhang, Q. Combining Organic and Inorganic Fertilization Enhances Soil Enzyme Activity, the Bacterial Community, and Molecular Ecological Network Complexity in Coal Mine Reclamation Areas. Agronomy 2024, 14, 1427. [Google Scholar] [CrossRef]
  52. Wei, J.; Zhang, X.; Liu, X.; Liang, X.; Chen, X. Influence of Root Components of Celery on Pyrene Bioaccessibility, Soil Enzymes and Microbial Communities in Pyrene and Pyrene-Diesel Spiked Soils. Sci. Total Environ. 2017, 599–600, 50–57. [Google Scholar] [CrossRef]
  53. Tilvikiene, V.; Venslauskas, K.; Povilaitis, V.; Navickas, K.; Zuperka, V.; Kadziuliene, Z. The Effect of Digestate and Mineral Fertilisation of Cocksfoot Grass on Greenhouse Gas Emissions in a Cocksfoot-Based Biogas Production System. Energy Sustain. Soc. 2020, 10, 13. [Google Scholar] [CrossRef]
  54. Meehan, P.; Burke, B.; Doyle, D.; Barth, S.; Finnan, J. Exploring the potential of grass feedstock from marginal land in Ireland: Does marginal mean lower yield? Biomass Bioenergy 2017, 107, 361–369. [Google Scholar] [CrossRef]
  55. Motesharezadeh, B.; Ahmadiyan, E.; Alikhani, H.A.; Azarnivand, H. The Use of Coal Gangue as a Cultivation Bed Conditioner in Forage Maize Inoculated with Arbuscular Mycorrhizal Fungi. Commun. Soil. Sci. Plant Anal. 2017, 48, 1266–1279. [Google Scholar] [CrossRef]
  56. Cuiyun, Y.; Yihang, L.; Jing, Y.; Hongyou, Z.; Zhaoyou, D.; Deying, T.; Oo, A.K.; Lixia, Z. Correlation between Soil Environment and Yield and Quality of SHAREN (Amomi Fructus) Under Different Planting Patterns. Digit. Chin. Med. 2023, 6, 221–233. [Google Scholar] [CrossRef]
  57. Azam, F. Studies on Organic Matter Dynamics and Nitrogen Availability Using 14C and 15N. J. Agron. 2001, 1, 20–24. [Google Scholar] [CrossRef]
  58. Wang, B.; Ma, Y.; Lee, X.; Wu, P.; Liu, F.; Zhang, X.; Li, L.; Chen, M. Environmental-Friendly Coal Gangue-Biochar Composites Reclaiming Phosphate from Water as a Slow-Release Fertilizer. Sci. Total Environ. 2021, 758, 143664. [Google Scholar] [CrossRef] [PubMed]
  59. Bi, Y.; Xiao, L.; Liu, R. Response of Arbuscular Mycorrhizal Fungi and Phosphorus Solubilizing Bacteria to Remediation Abandoned Solid Waste of Coal Mine. Int. J. Coal Sci. Technol. 2019, 6, 603–610. [Google Scholar] [CrossRef]
  60. Bulak, P.; Proc, K.; Pawłowska, M.; Kasprzycka, A.; Berus, W.; Bieganowski, A. Biogas Generation from Insects Breeding Post Production Wastes. J. Clean. Prod. 2020, 244, 118777. [Google Scholar] [CrossRef]
  61. Abbasi, T.; Tauseef, S.M.; Abbasi, S.A. Biogas Energy; Springer: New York, NY, USA, 2012; ISBN 978-1-4614-1039-3. [Google Scholar]
  62. Seppälä, M.; Paavola, T.; Lehtomäki, A.; Rintala, J. Biogas Production from Boreal Herbaceous Grasses—Specific Methane Yield and Methane Yield Per Hectare. Bioresour. Technol. 2009, 100, 2952–2958. [Google Scholar] [CrossRef] [PubMed]
  63. McEniry, J.; O’Kiely, P. Anaerobic Methane Production from Five Common Grassland Species at Sequential Stages of Maturity. Bioresour. Technol. 2013, 127, 143–150. [Google Scholar] [CrossRef]
  64. Rodríguez, B.C.; Zuazo, V.H.D.; Rodríguez, M.S.; García-Tejero, I.F.; Ruiz, B.G.; De Torres, M.A.R.-R.; Ordóñez-Fernández, R.; Carbonell-Bojollo, R.M.; Tavira, S.C. Legumes Protect the Soil Erosion and Ecosystem Services. In Advances in Legumes for Sustainable Intensification; Elsevier: Amsterdam, The Netherlands, 2022; pp. 247–266. ISBN 978-0-323-85797-0. [Google Scholar]
  65. Blanco-Canqui, H. Growing Dedicated Energy Crops on Marginal Lands and Ecosystem Services. Soil. Sci. Soc. Amer J. 2016, 80, 845–858. [Google Scholar] [CrossRef]
  66. Bužinskienė, R.; Miceikienė, A.; Venslauskas, K.; Navickas, K. Assessment of Energy–Economy and Environmental Performance of Perennial Crops in Terms of Biogas Production. Agronomy 2023, 13, 1291. [Google Scholar] [CrossRef]
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Figure 1. Scheme of vegetation and fermentation experiments.
Figure 1. Scheme of vegetation and fermentation experiments.
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Figure 2. Influence of OMF on the main properties of soil (pH, TOC—total organic carbon, TN—total nitrogen). Explanations: arable soil (CS), degraded soil (DS), degraded soil with 1% OMF (DS + 1%), with 2% OMF (DS + 2%), with 5% OMF (DS + 5%), and with 10% OMF (DS + 10%). Results are shown as mean + SD; different letters above the bars indicate statistically significant differences assessed by Tukey’s test at p < 0.05.
Figure 2. Influence of OMF on the main properties of soil (pH, TOC—total organic carbon, TN—total nitrogen). Explanations: arable soil (CS), degraded soil (DS), degraded soil with 1% OMF (DS + 1%), with 2% OMF (DS + 2%), with 5% OMF (DS + 5%), and with 10% OMF (DS + 10%). Results are shown as mean + SD; different letters above the bars indicate statistically significant differences assessed by Tukey’s test at p < 0.05.
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Figure 3. Influence of OMF on content of main micronutrients (Mn, Mo, Co, and Fe) in soil. Explanations: arable soil (CS), degraded soil (DS), degraded soil with 1% OMF (DS + 1%), with 2% OMF (DS + 2%), with 5% OMF (DS + 5%), and with 10% OMF (DS + 10%). Results are shown as mean + SD; different letters above the bars indicate statistically significant differences assessed by Tamhane’s test (Co) and Tukey’s test at p < 0.05.
Figure 3. Influence of OMF on content of main micronutrients (Mn, Mo, Co, and Fe) in soil. Explanations: arable soil (CS), degraded soil (DS), degraded soil with 1% OMF (DS + 1%), with 2% OMF (DS + 2%), with 5% OMF (DS + 5%), and with 10% OMF (DS + 10%). Results are shown as mean + SD; different letters above the bars indicate statistically significant differences assessed by Tamhane’s test (Co) and Tukey’s test at p < 0.05.
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Figure 4. Influence of OMF on content of main heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) in studied soils. Explanations: arable soil (CS), degraded soil (DS), degraded soil with 1% OMF (DS + 1%), with 2% OMF (DS + 2%), with 5% OMF (DS + 5%), and with 10% OMF (DS + 10%). Results are shown as mean + SD; different letters above the bars indicate statistically significant differences assessed by Tukey’s test at p < 0.05.
Figure 4. Influence of OMF on content of main heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) in studied soils. Explanations: arable soil (CS), degraded soil (DS), degraded soil with 1% OMF (DS + 1%), with 2% OMF (DS + 2%), with 5% OMF (DS + 5%), and with 10% OMF (DS + 10%). Results are shown as mean + SD; different letters above the bars indicate statistically significant differences assessed by Tukey’s test at p < 0.05.
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Figure 5. Effect of OMF on activity of dehydrogenase (DHA), protease (PROT), acid phosphatase (ACP) and alkaline phosphatase (ALP) in studied soils. Explanations: arable soil (CS), degraded soil (DS), degraded soil with 1% OMF (DS + 1%), with 2% OMF (DS + 2%), with 5% OMF (DS + 5%), and with 10% OMF (DS + 10%). Results are shown as mean + SE; different letters above the bars indicate statistically significant differences assessed by Tukey’s test at p < 0.05.
Figure 5. Effect of OMF on activity of dehydrogenase (DHA), protease (PROT), acid phosphatase (ACP) and alkaline phosphatase (ALP) in studied soils. Explanations: arable soil (CS), degraded soil (DS), degraded soil with 1% OMF (DS + 1%), with 2% OMF (DS + 2%), with 5% OMF (DS + 5%), and with 10% OMF (DS + 10%). Results are shown as mean + SE; different letters above the bars indicate statistically significant differences assessed by Tukey’s test at p < 0.05.
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Figure 6. Effect of OMF on the shoot dry biomass, root dry biomass, and fresh shoot biomass of cocksfoot harvested from the studied soils. Explanations: arable soil (CS), degraded soil (DS), degraded soil with 1% OMF (DS + 1%), with 2% OMF (DS + 2%), with 5% OMF (DS + 5%), and with 10% OMF (DS + 10%). Results are shown as mean + SD; different letters above the bars indicate statistically significant differences assessed by Tamhane’s test (dry shoot biomass) and Tukey’s test at p < 0.05.
Figure 6. Effect of OMF on the shoot dry biomass, root dry biomass, and fresh shoot biomass of cocksfoot harvested from the studied soils. Explanations: arable soil (CS), degraded soil (DS), degraded soil with 1% OMF (DS + 1%), with 2% OMF (DS + 2%), with 5% OMF (DS + 5%), and with 10% OMF (DS + 10%). Results are shown as mean + SD; different letters above the bars indicate statistically significant differences assessed by Tamhane’s test (dry shoot biomass) and Tukey’s test at p < 0.05.
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Figure 7. Pearson correlation matrix for the study variables. The graph shows statistically significant correlation coefficients at p < 0.05 (root_d—root dry matter; shoot_d—shoot dry matter; shoot_f—shoot fresh matter; DHA—dehydrogenase activity; ALP—alkaline phosphatase activity; ACP—acidic phosphatase activity; PROT—protease activity; TOC—total organic carbon; TN—total nitrogen).
Figure 7. Pearson correlation matrix for the study variables. The graph shows statistically significant correlation coefficients at p < 0.05 (root_d—root dry matter; shoot_d—shoot dry matter; shoot_f—shoot fresh matter; DHA—dehydrogenase activity; ALP—alkaline phosphatase activity; ACP—acidic phosphatase activity; PROT—protease activity; TOC—total organic carbon; TN—total nitrogen).
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Figure 8. Daily biogas production during plant biomass digestion presented as mean ± SD.
Figure 8. Daily biogas production during plant biomass digestion presented as mean ± SD.
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Table 1. Properties of soil and organic–mineral fertilizer use in this study.
Table 1. Properties of soil and organic–mineral fertilizer use in this study.
ParameterUnitCSDSOMF
pH (in 1 M KCl)-5.424.226.8
N-NH4mg/kg dm2.433.08630.07
N-NO3mg/kg dm12.163.871461.2
P2O5mg/100 g dm23.006.45155.40
K2Omg/100 g dm20.712.7754.18
Mgmg/100 g dm8.634.0185.74
TOC%--15.08
Cdmg/kg dm--0.25
Crmg/kg dm--34.97
Cumg/kg dm--64.25
Nimg/kg dm--21.49
Pbmg/kg dm--18.12
Znmg/kg dm--317.46
Hgmg/kg dm--0.56
CS—arable soil; DS—degraded soil; OMF—organic–mineral fertilizer; TOC—total organic carbon; dm—dry matter.
Table 2. Main characteristics of plant biomass as a feedstock for the digestion process.
Table 2. Main characteristics of plant biomass as a feedstock for the digestion process.
VariantVS
(% of TS)		TN
(% of TS)		TOC
(% of TS)		Protein
(% of TS)		C/N
(−)		NDF
(g/kg TS)		ADF
(g/kg TS)		ADL
(g/kg TS)		CE
(g/kg TS)		HCE
(g/kg TS)		MS
(% of TS)
CS86.5 ± 0.3 a2.0 ± 0.0 a47.3 ± 0.7 a12.3 ± 0.2 a23.9 ± 0.2 b712.9 ± 20.5 a350.4 ± 35.4 a79.6 ± 6.2 a270.8 ± 29.8 a362.2 ± 33.5 a6.6 ± 0.3 a
DS + 1%89.2 ± 1.5 b2.4 ± 0.1 b48.3 ± 0.5 a15.1 ± 0.4 b20.0 ± 0.7 a720.7 ± 4.0 a319.3 ± 5.3 a70.2 ± 18.8 a249.4 ± 21.7 a401.1. ±8.8 a10.0 ± 0.4 b
TS—Total solid; VS—volatile solids; TN—total nitrogen content; TOC—total organic carbon content; C/N—total organic carbon and nitrogen ratio; NDF—neutral detergent fiber; ADF—acid detergent fiber; ADL—acid detergent lignin; CE—cellulose; HCE—hemicellulose; MS—monosaccharides; different letters by means ± SD indicate statistically significant differences evaluated by Student’s test at p < 0.05.
Table 3. Biogas and methane potential and specific energy of plant biomass.
Table 3. Biogas and methane potential and specific energy of plant biomass.
VariantBGP
NL/(gTS)		BMP
NL/(gTS)		SE
GJ/(MgTS)		CH4
%		BGP
NL/(gVS)		BMP
NL/(gVS)		SE
GJ/(MgVS)
CS0.629 ± 0.017 a0.360 ± 0.011 a12.90± 0.41 a57.27 ± 0.242 a0.726 ± 0.020 a0.416 ± 0.013 a14.90 ± 0.47 a
DS + 1%0.580 ± 0.010 b0.328 ± 0.004 b11.752 ± 0.14 b56.63 0.273 a0.650 ± 0.011 b0.368 ± 0.005 b13.19 ± 0.16 b
NL—volume in liters (L) under normal conditions; BGP—biogas potential; BMP—methane potential; SE—specific energy of biomass converted into methane; different letters by means ± SD indicate statistically significant differences evaluated by Student’s test at p < 0.05.
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MDPI and ACS Style

Wydro, U.; Wołejko, E.; Joniec, J.; Bober, A.; Chomczyńska, M. Improving the Biomass Energy Yield of Cocksfoot Cultivated on Degraded Soil Amended with Organic–Mineral Fertilizer. Energies 2025, 18, 1165. https://doi.org/10.3390/en18051165

AMA Style

Wydro U, Wołejko E, Joniec J, Bober A, Chomczyńska M. Improving the Biomass Energy Yield of Cocksfoot Cultivated on Degraded Soil Amended with Organic–Mineral Fertilizer. Energies. 2025; 18(5):1165. https://doi.org/10.3390/en18051165

Chicago/Turabian Style

Wydro, Urszula, Elżbieta Wołejko, Jolanta Joniec, Agata Bober, and Mariola Chomczyńska. 2025. "Improving the Biomass Energy Yield of Cocksfoot Cultivated on Degraded Soil Amended with Organic–Mineral Fertilizer" Energies 18, no. 5: 1165. https://doi.org/10.3390/en18051165

APA Style

Wydro, U., Wołejko, E., Joniec, J., Bober, A., & Chomczyńska, M. (2025). Improving the Biomass Energy Yield of Cocksfoot Cultivated on Degraded Soil Amended with Organic–Mineral Fertilizer. Energies, 18(5), 1165. https://doi.org/10.3390/en18051165

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