Search Results (23)

The pursuit of sustainable alternatives to portland cement has become a global imperative within the construction sector, driven by the need to reduce carbon dioxide emissions and energy consumption. Among the promising alternatives, agricultural ashes have garnered attention for their potential as alternative supplementary cementitious materials (ASCMs), owing to their inherent pozzolanic properties when appropriately processed. However, the availability and utilization of these ashes have predominantly been concentrated in tropical and subtropical regions, where such biomass is more abundant. This review offers a comprehensive bibliometric analysis to identify and assess agricultural ashes (specifically switchgrass, barley, sunflower, and oat husks) that are cultivated in temperate and cold climates and exhibit potential for SCM application. The analysis aims to bridge the knowledge gap by systematically mapping the existing research landscape and highlighting underexplored resources suitable for cold-region implementation. Key processing parameters, including incineration temperature, retention duration, and post-combustion grinding techniques, are critically examined for their influence on the resulting ash’s physicochemical characteristics and pozzolanic reactivity. In addition, the effect on fresh, hardened, and durability properties was evaluated. Findings reveal that several crops grown in colder regions may produce ashes rich in reactive silica, thereby qualifying them as viable ASCM candidates and bioenergy sources. Notably, the ashes derived from switchgrass, barley, oats, and sunflowers demonstrate significant reactive silica content, reinforcing their potential in sustainable construction practices. Hence, this study underscores the multifaceted benefits of contributing to the decarbonization of the cement industry and circular economy, while addressing environmental challenges associated with biomass waste disposal and uncontrolled open-air combustion. Full article

Biochar continues to attract growing interest as a promising soil amendment, particularly in areas contaminated with heavy metals. The present experiment was conducted on soil contaminated with zinc (Zn), copper (Cu), and nickel (Ni) in the following treatments: contamination with a single heavy metal (Zn, Cu, or Ni) and with a combination of heavy metals (ZnCu, ZnNi, CuNi, and ZnCuNi). The analysis was performed in soil samples with and without biochar addition. The biochar dose was 15 g kg⁻¹ soil. The biochar was produced from sunflower husks, with the following composition: ash—7.49%; organic carbon (C_org)—83.92%; total nitrogen (N_total)—0.91%; hydrogen—2.56%; sulfur—0.02%; oxygen—3.30%; and pH—9.79. Nickel, followed by Cu, induced the greatest decrease in Zea mays yields, whereas the smallest decline in yields was observed in response to Zn contamination. The combined application of the tested heavy metals had more damaging effects, in particular by decreasing maize yields. The values of the heavy metal impact index (IF_Hm) confirmed that heavy metals exerted a negative impact on the biochemical activity of soil. Copper applied alone and in combination with other heavy metals had the most inhibitory effect on soil enzyme activity. The toxicity of the analyzed heavy metals for plants and soil enzymes was reduced by biochar. This is confirmed by the tolerance index (TI) values for copper and nickel in Zea mays. The TI values for copper increased from 0.318 in soil without biochar to 0.405 in soil with biochar. For nickel, the TI values increased from 0.015 to 0.133. The values of the biochar impact index (IF_CB) also suggest that biochar stimulated enzyme activity in all treatments. Biochar also improved the chemical and physicochemical properties of soil, including the content of C_org and N_total and soil pH. Full article

The transition from fossil fuels to renewable energy sources often requires shifting toward biomass fuels such as agriculture residues and waste, which tend to emit higher emission rates during combustion, and one of them is sulfur compounds. The main objective of this study is to clarify the regularities of the formation of sulfur compounds depending on the technological factors when burning sulfur-containing biomass. The experiments were conducted on two experimental stands—models of 20 kW and 25 kW capacities of industrial boilers equipped with reciprocating grates—by burning sunflower husk pellets and meat bone meal. The influence of incomplete combustion (indicator CO concentration), flue gas recirculation, and combined effects of both factors on concentrations of SO₂, SO₃, and H₂S were investigated during experiments. In addition, 20–90% of the sulfur in the fuel is converted to SO₂, contingent upon the combustion conditions. These findings have practical implications for the design and operation of biomass combustion systems. The highest SO₂ emissions were observed when primary air was mixed with flue gas recirculation and at the highest content of CO. The correlation of SO₂ and SO₃ and SO₂ and H₂S concentrations in flue gases of boilers was investigated. The conversion ratio of SO₂ to SO₃ was determined under different combustion modes and showed that this ratio can reach up to 5%. The sulfur content in ash deposits in different areas of the actual industrial boiler was analyzed. The highest percent of sulfur (S = 20%) in ash was found on the first boiler pass. Full article

This study examines the qualities and potential uses of various types of biomass as fuel, focusing on wood pellets, sunflower husk pellets and mixed pellets. The primary objective is to analyze the thermal and energy properties of these pellets in order to evaluate their efficiency and acceptance by consumers in the Bulgarian market. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) are employed, revealing that the processes of drying and volatile substance release are accompanied by energy absorption, with combustion being the main stage where most heat is generated. The results show that wood pellets have 7.31% moisture, 0.72% ash and a calorific value of 18.33 kJ/kg; sunflower husk pellets have 7.62% moisture, 2.42% ash and a calorific value of 19.63 kJ/kg; and mixed pellets have 7.07% moisture, 0.69% ash and a calorific value of 18.05 kJ/kg. These findings indicate that the pellets achieve efficient combustion with minimal mass loss. The conducted marketing research reveals that Bulgarian consumers prefer wood and mixed pellets for their efficiency, although sunflower husk pellets are more affordable. Key factors influencing consumer choice include price, which is important for 51% of the respondents, and quality, prioritized by 34%. The conclusion of this study is that pellets are a promising energy source with good environmental and economic characteristics, and the results can contribute to the development of more efficient fuels adapted to the needs of the market and consumers. Full article

The conception of a circular economy is one of the crucial approaches that could accelerate the processes of achieving sustainable development goals, which challenge all industries and societies. Still, the potential of agricultural waste in this area is not fully covered by technologies. This study aims to develop a full-scale technology for self-sustaining double-stage circularity through the utilization of sunflower agriculture’s waste in bio-fertilizers. The investigation is performed in Bulgaria, as available sunflower husk ashes (SHA) are subjected to analyses regarding their applicability for bio-fertilizer production. The design of the technology and full-scale equipment commissioning process are described. The conditions and results from the adjustment tests are presented and, based on these, the optimal operating parameters are defined. The successful granulation of different samples of SHA at these conditions is performed and the final granular bio-fertilizers are characterized with a content of 30 wt. % K₂O and 5% wt. P₂O. The moisture of the prepared granules is approx. 5 wt. %, and they pass the crushing tests at 2.5 kgf. The biotoxicity of the bio-fertilizer is also analyzed, and the results show its applicability in agriculture. The proposed approach allows the initial sources of K₂O and P₂O from soil feeding the sunflowers to circulate in different industrial technologies and to reenter the soil through bio-fertilizers. Full article

This paper presents a circular business model (CBM) designed to promote the valorization of agricultural biomass ash for producing an alternative binder in construction, aiming to reduce CO₂ emissions and landfill waste. The circular economy framework emphasizes regeneration and restoration to minimize resource and energy use, waste generation, pollution, and other environmental impacts. Aligned with these principles of sustainability, the construction industry, energy sector and food processing industry can establish a shared interest through industrial symbiosis. In the proposed CBM, waste from one industry becomes an input for another. The model leverages industrial symbiosis by using sunflower husk ash (SHA) as an alternative hydroxide activator for alkali-activated materials. A case study of companies in the Republic of Serbia that produce SHA as waste forms the basis for this model, featuring promising results of experimental testing of three alkali-activated mortars produced by activating ground-granulated blast furnace slag (GGBFS) with different SHA contents (15, 25 and 35 wt% GGBFS), instead of commercially available hydroxide activators. The potential of SHA as an alternative activator was assessed by testing flow diameter and compressive strength at 7 and 28 days of curing. The highest 28-day compressive strength was attained for the addition of 25% SHA (28.44 MPa). The promising results provided a valid basis for CBM development. The proposed CBM is stream-based, resulting from merging and upgrading two existing industrial symbioses. This study highlights the benefits of the CBM while addressing the challenges and barriers to its implementation, offering insights into the possible integration of agricultural biomass ash into sustainable construction practices. Full article

Sunflower husk (SFH) contributes 45–60% of the total sunflower seed weight and is a by-product of the sunflower oil industry. Among other elements, SFH ash contains K, Na, Ca and Mg. These elements cause rapid growth of ash deposits on convective heating surfaces of the boiler, resulting in reduced efficiency. The aim of this paper is to examine the possibility of producing quality fuel from SFH by its pretreatment with the technique of torrefaction in a fluidized bed in superheated water vapor. Continuous monitoring of the innovative SFH torrefaction process allowed for the determination of optimal process durations. SFH could be converted into a biofuel, having high calorific value and suitable characteristics for co-combustion with coal. Furthermore, the torrefaction in a fluidized bed of superheated water vapor allowed for a 6-fold reduction in the required process duration in comparison with data reported from the literature for the process of torrefaction in a dense bed, along with a 3-fold reduction in the chlorine content in SFH ash. These effects are beneficial to resolve the problem of corrosion on convective heating surfaces of boilers. However, torrefaction in superheated water vapor did not significantly reduce the content of alkaline and alkaline-earth elements in SFH ash. Still, this issue may be alleviated by significantly increasing the duration of SFH pretreatment. Full article

This study reveals the possibilities of the sustainable usage of pellets produced from waste biomass based on the thermal properties of processed raw materials. For this study, a thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and differential thermal analysis (DTA) were performed to better understand the thermal properties of the pellets. This study covered two types of wood pellets with different ratios of waste material: a kind of pellet made from a combination of wood and sunflower residues, and two types of pellets made from sunflower husks. The analysis revealed that the wood pellets offered the best thermal stability and high energy values, making them the preferred choice for heating systems. Mixed pellets showed a lower thermal capacity and combustion efficiency, showing possibilities for further optimization. Sunflower-husk pellets demonstrated a high calorific value, but their application was restricted by a significantly higher ash content and worse environmental impact compared with the first two types of pellets. In addition, the outputs from this study revealed that pellets composed of wood reduced their mass the most at temperatures in the range of 310 to 323 °C. In comparison, the mass loss of sunflower husk pellets was 35.6%/°C (at a 5 °C/min temperature gradient) lower than wood pellets and about 42%/°C lower at a 10 °C/min temperature gradient. These findings highlight the importance of pellet production and technology usage to achieve better sustainability and better thermal properties of the pellets. Full article

In recent years, there has been considerable focus on ensuring that energy is used in the most efficient manner possible. This is due to the fact that globally, over 70% of energy is generated from fossil fuels. Consequently, the matter of designing and utilizing materials that will negate energy losses within the construction industry is of paramount importance. Simultaneously, the necessity for a sustainable approach to the design and production of materials is strongly emphasized. This paper presents an innovative approach to the use of a combination of mineral and plant-based fillers in polyurethane foam technology as a thermal insulation material with the potential to be used in construction to reduce energy consumption. Polyurethane composites containing fly ash from biomass combustion and the addition of rice, sunflower, and buckwheat husks as plant fillers were proposed. The structure of the obtained materials was studied, and the most important physical properties were analyzed. These included apparent density, dimensional stability, water absorption, and the effects of UV radiation and water influence on the carbon, hydrogen, nitrogen, and oxygen content. Moreover, the mechanical properties of the materials were investigated, including compressive strength and brittleness. Additionally, the foams were subjected to flammability tests using a cone calorimeter. Furthermore, additional parameters were determined, including the limiting oxygen index and the vertical and horizontal flammability tests. The results demonstrate the beneficial effects of combining mineral and vegetable fillers in polyurethane foam. Full article

The energetic fossil resources of the world have decreased drastically in recent decades, and the quick and efficient solution to replace them is to use renewable biomass resources. This category also includes vegetable biomass, and within it, sunflower seed shells have an important contribution. The present work aimed to analyze the pellets obtained from the husks of sunflower seeds, as lignocellulosic biomass resulting from the production of edible oil, and for comparison, some pellets from beech sawdust were used. The main physical properties (such as moisture content, density, coefficient of densification, etc.), mechanical properties (such as shear strength) and calorific properties (high and low calorific value, calorific density, volatile content and ash content) were determined and statistically analyzed. As the main element of comparison of these types of pellets, the pellets obtained from beech sawdust were used. For the comparison of the pellets obtained from the husks of sunflower seeds, especially to observe their differences compared to the torrefied pellets, charcoal was chosen. The conclusions highlighted the fact that sunflower seed husks are an important source of biomass that can be used to obtain lignocellulosic pellets, and the torrefied pellets obtained from these husks are comparable with the energetic value of charcoal. Full article

In recent decades, there has been growing interest in the thermal conversion of various alternative fuels, such as biomass and waste-derived fuels. One of the technological solutions for the so-called direct co-combustion of fuels is to create mixtures of various fuels, called mixed secondary fuel. However, mixed secondary fuel has different properties compared to primary fuels. Due to this, by properly selecting the types and proportions of mixtures, it is possible to eliminate their potentially negative impact on both combustion technology and the natural environment. In this paper, we decided to prepare mixed secondary fuel by mixing sunflower husk pellets with RDF (refuse-derived fuel) in a ratio of 1:1 and then analyze the combustion process of the produced fuel in fluidized bed conditions. The results obtained on the basis of the presented research indicate that the mixed secondary fuel eliminated the impact of alkali metal compounds on reducing the melting point of ash and, consequently, on the combustion process of the mixed secondary fuel. An additional benefit is the reduction of emissions of harmful compounds into the atmosphere occurring during the combustion of municipal waste and compliance with the concept of the circular economy. Full article

Energy produced from waste biomass is more environmentally friendly than that produced from fossil resources. However, the problem of managing waste from the thermal conversion of biomass arises. The overarching goal of this article was to propose a method of utilizing biomass ash (sunflower husk) as a filler that positively affects the properties of rigid polyurethane foams. The scope of the presented research is to obtain and characterize rigid polyurethane foams (RPUFs) with the addition of two types of fillers: sunflower husks (SHs) and sunflower husk ash (SHA). First, an analysis of the fillers was carried out. The carbon content of SHs (C~49%) was ten times higher in comparison to SHA’s carbon content (C~5%). The morphology of the fillers and the particle size distribution were determined, which showed that in the case of SHs, particles with a size of 500–1000 µm predominated, while in SHA, the particles were 1–20 µm. The content of inorganic compounds was also determined. Potassium and calcium compounds were the most abundant in both fillers. The second part of the research was the analysis of polyurethane materials with the addition of fillers. The obtained results indicate that filler addition had a positive effect on the dimensional stability of the foams by eliminating the risk of material shrinkage. The biodegradation process of polyurethane materials was also carried out. The reference foam weight loss after 8 weeks was ~10%, while the weight loss of the foam containing SHA was over 28%. Physical and mechanical properties, cell structure, and thermal stability tests were also carried out. The use of bio-waste fillers creates a possibility for the partial replacement of petrochemical products with environmentally friendly and recycled materials, which fits into the circular economy strategy. Full article

This article proposes an innovative two-stage technology for biomass torrefaction generating high-quality biochar, more specifically biocoal, as solid fuel, and offering a promising solution to the challenges posed by the combustion of biomass. In particular, the higher quality of biochar as solid fuel reduces the build-up of unmanageable deposits on fired surfaces, as these deposits inhibit heat transfer and reduce the efficiency of biomass boilers. The proposed two-stage technology involves torrefaction in a hearth-type reactor at temperatures up to 250 °C, followed by a subsequent stage of cooling achieved through washing with water. The two-stage torrefaction technology is integrated within a vertical hearth reactor vessel composed of three superimposed trays serving for biomass input, torrefaction, and water washing combined with biomass cooling, respectively. Upon contact with torrefied biomass, cooling water turned into water vapor; hence, eliminating the requirement for subsequent biomass separation and drying. The system was tested on sunflower husk, and results showed a reduction in the content of problematic elements such as alkali metal chlorides or sulfur compounds in biochar ash, suggesting lower corrosion rates of convective heating surfaces of the boiler under ash sediments. It is hypothesized that, while water exited hot biomass in the form of water vapor instead of liquid water, as is typically the case in water-washing processes, a share of undesirable elements may still have been removed from biomass through vaporization, without necessitating any additional process for ash removal. Hence, the index values calculated according to the chemical analysis of biomass ash suggested that sunflower husk biochar (biocoal) resulting from the proposed two-stage torrefaction process may display fuel characteristics similar to biomasses whose combustion ash may form reduced levels of deposits on boiler surfaces. Therefore, the proposed technology holds the potential to improve solid fuel characteristics of biomass, targeting enhanced efficiency and sustainability of biomass-fired power plants. Full article

One of the options for reducing harmful emissions in the production of heat energy is the use of biomass, including in combination with industrial waste (for instance, coal and coke dust). Recent studies demonstrate that a mix of biomass and coal makes it possible to obtain a bio-coal briquette with better characteristics, which is a motivating factor in the search for alternative sources of heat energy from local agricultural waste. The aim of this research is to study the properties of bio-coal briquettes from biomass (sunflower husks and leaves) and industrial waste (coal and coke dust). The raw material was grinded and used for the production of bio-coal briquettes of 20%, 30%, 40%, 50%, 60%, and 70% of biomass. The biomass was grinded to the size of no more than 2 mm for the fine fraction and no more than 6 mm for the coarse fraction. The briquettes were made mechanically using a hydraulic press with a compression pressure of 25 MPa without the use of any binder. The characteristics of the investigated bio-coal briquettes, such as density, strength, moisture content, ash content, volatile yield, calorific value, ignition time, burning duration, and burning rate, have good enough values. The fine fraction briquettes compared to the coarse fraction briquettes have a longer burning time (about threefold longer) and a lower burning rate. For all briquettes, an increase in the composition of coal dust results in a rise in the burning time, whereas the burning rate falls. The best in terms of strength, calorific value and combustion parameters are the following briquettes: 70% sunflower husk and 30% coal dust from the Karazhyra deposit; 60% sunflower husk and 40% coal dust from the Shubarkul deposit; briquettes from 70% sunflower husk and 30% coke dust; briquettes from 80% leaves and 20% coal dust from the Karazhyra deposit; and briquettes from 70% leaves and 30% coal dust from the Shubarkul deposit. The selected briquettes are suitable as an alternative source of fuel. Full article

Rigid polyurethane foams (RPUFs) are characterized by their excellent viable properties; thus, these materials can be successfully used as thermal insulation materials. The main problem, the solution of which is partly indicated in this paper, is that the products for the synthesis of RPUFs are produced from petrochemicals. Due to this, the use of natural fillers in the form of waste biomass is introduced for the synthesis of RPUFs. The biodegradable biomass waste used in the RPUF production process plays multiple roles: it becomes an activator of the RPUF foaming process, improves selected properties of RPUF materials and reduces the production costs of insulating materials. The paper presents the results of the foaming process with the use of six different fillers: sunflower husk (SH), rice husk (RH), buckwheat husk (BH), sunflower husk ash (SHA), rice husk ash (RHA) and buckwheat husk ash (BHA). In all cases, composites of rigid polyurethane foam with 10 wt.% of filler were produced. New foams were compared with polyurethane materials without the addition of a modifier. Moreover, the paper presents the results of the fillers’ analysis used in the tests and the effects of the fillers’ addition as activators of the RPUF foaming process. Promising results were obtained for two of the fillers, BHA and SHA, as activators of the foaming process and confirmed by the volumetric results, where the named samples reached their maximum value in half the time compared to the remaining samples. In addition, the expansion rate for PU_10BHA was a maximum of approximately 11 cm³/s and PU_10SHA was a maximum of approximately 9 cm³/s, whereas the remaining samples showed this parameter at about 3 cm³/s. During the research, the scanning electron microscopy method and infrared camera technique were used. Full article