This work aims to study the influence of an oxidant agent on syngas quality. A series of tests using air and steam as oxidant agents have been performed and the results compared with those of a pyrolysis test used as a reference. Tests were carried out at Sapienza University of Rome, using an updraft reactor. The reactor was fed with hazelnut shells, waste biomass commonly available in some parts of Italy. Temperature distribution, syngas composition and heating value, and producible energy were measured. Air and steam gasification tests produced about the same amount of syngas flow, but with a different quality. The energy flow in air gasification had the smallest measurement during the experiments. On the contrary, steam gasification produced a syngas flow with higher quality (13.1 MJ/Nm3), leading to the best values of energy flow (about 5.4 MJ/s vs. 3.3 MJ/s in the case of air gasification). From the cold gas efficiency point of view, steam gasification is still the best solution,... [more]

The paper presents the results of research on the physicochemical properties of plant biomass consisting of four mint species, these being Mentha × piperita L. var. citrata Ehrh.—‘Bergamot’, Mentha × rotundifolia L., Mentha spicata L., and Mentha crispa L. The research conducted consisted of the technical analysis of biofuels—determining the heat of combustion and the calorific value of the material under study, and the content of ash, volatile compounds, and humidity. In addition, elemental analysis was carried out for the biomass under study by determining the content of carbon, hydrogen, nitrogen, and sulfur. The research demonstrated that Mentha × piperita L. var. citrata Ehrh.—‘Bergamot’ had the highest energy potential with a gross calorific value of 16.96 MJ·kg−1, and a net calorific value of 15.60 MJ·kg−1. Among the tested materials, Mentha × rotundifolia L. had the lowest content of ash at 7.23%, nitrogen at 0.23%, and sulfur at 0.03%, and at the same time had the highest cont... [more]

The interest in pellets utilization for households heating has been growing significantly in the last several years. However, the pellets need to meet certain quality requirements, including the mechanical durability (DU) index. In the winter seasons, the pellets are very often stored in unheated in-door systems or are transported by trucks over long distances. As a result, the pellets are exposed to external weather factors, including very low temperatures (even freezing ones), which can have a negative impact on the quality parameters of the fuel. There are several parameters affecting mechanical durability, but little is known about the influence of a very low temperature on the pellet properties. The aim of this research was to analyze the influence of freezing temperature storage on the mechanical durability of commercial pellets made of different biomass. The research was carried out in accordance with the international standard for solid biofuels PN-EN ISO 17831-1:2016-02. The s... [more]

Common kinetic parameters were obtained for leached and non-leached samples of vine wood biomass. Both samples were considered to have different proportions of cellulose, hemicellulose, and lignin compositions as a result of the leaching process. The two samples were analyzed in terms of pyrolysis kinetic parameters using non-isothermal thermogravimetric analysis. Furthermore, the classic Friedman isoconversional method, a deconvolution procedure using the Fraser−Suzuki function, and a modified Friedman method from a previous study on the delay in conversion degree were satisfactorily applied. The observed difference when the deconvolution technique was applied suggests that the classic Friedman method is not adequate for studying the pyrolysis of individual vine wood biomass components. However, this issue was solved by studying the delay in conversion degree of both biomasses and calculating the kinetic parameters using the resulting information. This procedure was found to be useful... [more]

The utilisation of low- and medium-temperature energy allows to reduce the energy shortage and environmental pollution problems because low-grade energy is plentiful in nature and renewable as well. In the past two decades, thanks to its feasibility and reliability, the organic Rankine cycle (ORC) has received great attention. The present work is focused on a small-scale (7.5 kW nominal electric power) combined cooling, heating and power ORC system powered by the combustion of olive pomace obtained as a by-product in the olive oil production process from an olive farm situated in the central part of Italy. The analysis of the employment of this energy system is based on experimental data and Aspen Plus simulation, including biomass and combustion tests, biomass availability and energy production analysis, Combined Cooling Heat and Power (CCHP) system sizing and assessment. Different low environmental impact working fluids and various operative process parameters were investigated. Oliv... [more]

The increasing amount of residual waste presents several opportunities to use biomass as a renewable energy source. Agricultural biomass is a raw material with a high ash content, which can be a problem in any form of energy conversion. To obtain better quality biofuel, excess mineral matter must be removed. Demineralization is a simple form of mixing and washing biomass with various liquids to reduce ash content. Water, acetic acid, hydrochloric acid and nitric acid are common solvents used for this purpose. Ash is composed of different micro (Zn, Cu, Fe) and macro elements (Mg, Ca, K), which can have different consequences for the use of biomass for thermal energy. Different solvents have different effects on the individual elements, with inorganic acids having the greatest effect in demineralization processes, with a reduction in ash content of up to 80% for corn and about 99% for soybeans.

Pellet stoves are popular appliances because they are an affordable technology and because the fuel is easy to store and to use. The increasing concern for environmental issues, however, requires a continuous effort to reduce pollutant levels in the atmosphere. This experimental work focuses on flue gas recirculation (FGR) as a possible way to improve combustion and decrease the emissions of carbon monoxide CO, particulate matter PM, and nitrogen oxides NOx in order to fulfill European and Italian emission requirements, for NOx in particular. A pellet stove has been tested in several experimental sessions with and without FGR. Pollutant emissions have been measured and analyzed in terms of statistical summaries and instantaneous trends. With FGR, the average CO and PM emissions were found to be 80% and 45% lower than the corresponding emissions without FGR. Results for PM are significant since FGR reduces emissions well below the most restrictive limits enforced in Italy. The analysis... [more]

The co-pyrolysis of various biomasses mixed with two types of plastic waste was investigated in this study. Mixture M1 consisted of 30% m/m styrene−butadiene rubber (SBR), 40% m/m polyethylene terephthalate (PET), and 30% m/m polypropylene (PP). M2 consisted of 40% m/m PET, 30% m/m PP, and 30% m/m acrylonitrile−butadiene−styrene copolymer (ABS). The SBR, ABS, and PP used in this study were from the automotive industry, while the PET originated from scrap bottles. Co-pyrolysis was performed using wood biomass, agricultural biomass, and furniture trash. Thermal treatment was performed on samples from room temperature to 400 or 600 °C at a heating rate of 10 °C/min under N2 at a flow rate of 3 dm3/min. Based on the findings of the experiments, an acceptable temperature was found for the fixed-bed pyrolysis of biomass−plastic mixtures with varying ratios, and the raw materials were pyrolyzed under the same conditions. The composition of the derived gaseous fraction was investigated. The co... [more]

Climate change and the depletion of fossil fuels make it urgent to find an alternative to oil-based fuels, especially in machines powered by internal combustion engines. Biomass is currently a poorly used source of energy and meets the necessary conditions to replace a large part of oil-based fuels. However, current engines cannot burn solid biomass and a specific engine needs to be developed. This work proposes the thermodynamic cycle of a biomass-fueled internal combustion engine. The cycle is significantly different from the Otto cycle, since compression and heat absorption occur simultaneously, in a single stage. Since it is not possible to find a function that relates pressure to volume at this stage, an approximate method is proposed to solve the cycle without resorting to numerical methods. The results show that the maximum pressure and temperature of a biomass-fueled engine cycle are somewhat higher than those of the equivalent Otto cycle. However, more significantly, the cycle... [more]

An inexpensive bio-mass-derived hard carbon from tamarind pods was used as an anode, and nitrogen and nitrogen (N)/sulfur (S) co-doped graphene were used as a cathode for novel hybrid Na-ion supercapacitors. The structural and surface morphological analyses are investigated using a range of techniques. The 3D network of the heteroatom-doped graphene skeleton edges for N and NS-doping conformations were assigned as N-RGOs (N1s-5.09 at.%) and NS-RGOs (N1s-7.66 at.% and S1s-2.22 at.%) based on energy dispersive X-ray spectroscopy elemental mapping. The negative electrode (T-HC) hard carbon was pre-treated by pre-sodiation with a half-cell process by galvanostatic charge−discharge in a sodium-ion battery at 0.01−2.5 V vs. Na/Na+. The T-HC//NS-RGO, T-HC//N-RGO, and T-HC//RGO were used to construct the Na-ion supercapacitor device. In the CV experiments, the electrochemical galvanostatic charge−discharge was studied at 1.0−4.2 V. The specific capacitance was 352.18 F/g for the T.HC/NS-RGO de... [more]

This article deals with the influence of the final drying degree of moist biomass used as fuel in a power or CHP plant on indirect dryer sizing. For a description of the drying process, experiments with wet bark containing approx. 50 wt% of water were carried out in a laboratory indirect dryer. A new parameter called drying effectivity was introduced, whose size varies according to the degree of biomass being dried. Its maximum value corresponds to the optimal biomass drying, when the relative size of the indirect dryer to evaporate the required mass of water from the biomass would be smallest. Based on the experimentally determined drying characteristics of wet bark, the optimal drying of 13 wt% of water content was evaluated. If the bark was dried to a lower water content, the required relative size and price of the dryer would increase. Similarly, drying a bark with water content above 31 wt% is not very advantageous because drying effectivity continues to increase rapidly at this s... [more]

The depletion of fossil fuels has led to a search for new methods of fuel and chemical production from biomass. One of the methods of converting biomass into valuable products is the process of pyrolysis. This process has been extensively researched in recent years due to the rising prices of energy and chemicals. This work contains basic information on the pyrolysis process concerning the individual components present in the biomass and the types of biomass used in the pyrolysis process. Particular attention was paid to sewage sludge, the management of which is a big challenge. The influence of the most important process parameters (temperature, heating rate, residence time of the solid and vapor, reaction atmosphere) on the pyrolysis products (char, oil, and gas) was presented. The paper presents an overview of the reactors used in the pyrolysis process, from slow to fast pyrolysis, together with their efficiency, advantages, and disadvantages. The analysis of the application of othe... [more]

Microalgal biomass is a promising alternative and renewable substrate for bioenergy production. The main problem for its commercial application is to obtain and keep a high level of production by providing microalgae with appropriate conditions for growth. The aim of this study was to determine optimal culture conditions such as temperature, photoperiod, and pH. The amount of biomass by gravimetry, optical density by spectrophotometry, and productivity were analyzed. Suitable values of cultivation parameters allowed for the increased growth and biomass productivity of Arthrospira platensis (4.24 g·L−1), Chlamydomonas reinchardtii (1.19 g·L−1), Chlorella vulgaris (2.37 g·L−1), and Dunaliella salina (4.50 g·L−1) and optical density for Ch. reinchardtii and C. vulgaris. These species had maximum biomass productivity of 0.72, 0.12, 0.36, and 0.77 g·L−1·d−1, respectively. Productivity was determined by cultivation temperature and for Ch. reinchardtii also by pH.

The accumulation of energy from non-programmable renewable sources is a crucial aspect for the energy transition. Using surplus electricity from renewable energy sources, power-to-gas plants allow to produce a substitute natural gas (SNG) that can be injected in the existing infrastructure for large-scale and long-term energy storage, contributing to gas grid decarbonisation. The plant layout, the method used for carbon dioxide capture and the possible cogeneration of electricity can increase the efficiency and convenience of SNG synthesis plants. In this work, a system for the simultaneous production of SNG and electricity starting from biomass and fluctuating electricity from renewables is proposed, using a plant based on the Allam thermodynamic cycle as the power unit. The Allam power cycle uses supercritical CO2 as evolving fluid and is based on the oxycombustion of gaseous fuels, thus greatly simplifying CO2 capture. In the proposed system, oxycombustion is performed using biomass... [more]

A dual fluidized bed (DFB) gasification process is proposed to produce sustainable reducing gas for the direct reduction (DR) of iron ore. This novel steelmaking route is compared with the established process for DR, which is based on natural gas, and with the emerging DR technology using electrolysis-generated hydrogen as the reducing gas. The DFB-DR route is found to produce reducing gas that meets the requirement of the DR reactor, based on existing MIDREX plants, and which is produced with an energetic efficiency comparable with the natural gas route. The DFB-DR path is the only route considered that allows negative CO2 emissions, enabling a 145% decrease in emissions relative to the traditional blast furnace−basic oxygen furnace (BF−BOF) route. A reducing gas cost between 45−60 EUR/MWh is obtained, which makes it competitive with the hydrogen route, but not the natural gas route. The cost estimation for liquid steel production shows that, in Sweden, the DFB-DR route cannot compete... [more]

Agave bagasse is a residual biomass in the production of the alcoholic beverage tequila, and therefore, it is a promising raw material in the development of biorefineries using hot compressed water pretreatment (hydrothermal processing). Surfactants application has been frequently reported as an alternative to enhance monomeric sugars production efficiency and as a possibility to reduce the enzyme loading required. Nevertheless, the surfactant’s action mechanisms in the enzymatic hydrolysis is still not elucidated. In this work, hot compressed water pretreatment was applied on agave bagasse for biomass fractionation at 194 °C in isothermal regime for 30 min, and the effect of non-ionic surfactants (Tween 20, Tween 80, Span 80, and Polyethylene glycol (PEG 400)) was studied as a potential enhancer of enzymatic saccharification of hydrothermally pretreated solids of agave bagasse (AGB). It was found that non-ionic surfactants show an improvement in the conversion yield of cellulose to gl... [more]

The possibilities of using curly-leaf pondweed for energy purposes were analyzed. This plant contributes to overgrowth of water reservoirs, causing their eutrophication. The plants examined were from two different water reservoirs: Lake Winiary (Gniezno) and Lake Rusalka (Poznan). On the basis of the investigations, it was determined that it is possible to use curly-leaf pondweed for energy purposes, both in the combustion method and in the biomethane fermentation process. Studies were performed to assess the suitability of the plants for combustion as a solid biofuel and studies on the use of pondweed as a fermenter feedstock. The calorimetric study showed the possibility of obtaining more energy for the curly-leaf pondweed coming from Lake Rusalka. The heat of combustion of these plants was 13.95 MJ·kg−1 (Winiary pondweed) and 9.10 MJ·kg−1 (Rusalka pondweed). On the other hand, the calorific value of these plants was 12.60 MJ·kg−1 (Winiary pondweed) and 7.80 MJ·kg−1 (Rusalka pondweed... [more]

The oxyfuel combustion of a model MSW (municipal solid waste) under various conditions was carried out in a lab-scale reactor. The aim was to study the behavior of MSW and identify challenges and opportunities associated with the development of this technology in the context of integration with CCS (carbon capture and storage). The experimental results show the effects of the oxidizer composition on the combustion process. Complete combustion can be attained under a variety of oxyfuel conditions, and the differences highlighted with O2/CO2 as an oxidizer compared with O2/N2 do not constitute showstoppers. MSW oxyfuel combustion hence offers a great potential for the combined (1) treatment of waste (contaminants’ destruction, volume, and weight reduction), (2) production of heat/power, and (3) CCS with negative CO2 emissions.

The energy supply in Austria is significantly based on fossil natural gas. Due to the necessary decarbonization of the heat and energy sector, a switch to a green substitute is necessary to limit CO2 emissions. Especially innovative concepts such as power-to-gas establish the connection between the storage of volatile renewable energy and its conversion into green gases. In this paper, different methanation strategies are applied on syngas from biomass gasification. The investigated syngas compositions range from traditional steam gasification, sorption-enhanced reforming to the innovative CO2 gasification. As the producer gases show different compositions regarding the H2/COx ratio, three possible methanation strategies (direct, sub-stoichiometric and over-stoichiometric methanation) are defined and assessed with technological evaluation tools for possible future large-scale set-ups consisting of a gasification, an electrolysis and a methanation unit. Due to its relative high share of... [more]

In general, the biomass raw materials burned by biomass power plants generally have the characteristics of variable fuel types, high moisture content, and high volatile content. In this paper, a 130 t/h biomass circulating fluidized bed (BCFB) model was established on the MWorks platform with Modelica language. The influence of biomass type changes on operation parameters, the corresponding steady-state characteristics, and the dynamic characteristics of the BCFB were carried out. The temperature corresponding to the combustion of pine was overall higher than that of the other fuels, and the flue gas from the combustion of pine had the highest concentration of SO2, up to 520.49 mg/Nm3. The flue gas from the combustion of pure cotton sticks had the highest concentration of NO, up to 254.34 mg/Nm3. The changes of fuel type and moisture content all have a great influence on the operation of BCFBs. The emission of pollutants was not only related to the element content of fuel, but also clo... [more]

The production of fuel hydrocarbons from CO2-neutral raw materials is a promising task at present. The thermal dissolution of biochar obtained by the method of hydrothermal carbonization of sawdust was studied. The dissolution of biochar in tetralin (hydrogen donor solvent) was studied at different temperatures (350−450 °C) and with two types of dilution of the mixture with tetralin: 1/3 and 1/4. The process proceeded without a catalyst. It was found that the samples subjected to thermal dissolution at temperatures of 425−450 °C had the highest conversion and yield of liquid products. The reaction temperature also had a significant effect on the composition of liquid products. It was found that an increase in the reaction temperature led to a significant increase in benzenes, both in the direct and in the hexane fraction. A benzene yield of more than 50% was observed for both fractions at a temperature of 450 °C. It was also suggested that the possible positive effect of abietates on t... [more]

The article presents the possibilities of effective management of lignocellulosic waste by including it in the circular economy. The pyrolysis process was chosen as the thermal conversion method. This approach, due to a high flexibility of the obtained products, better quality of the solid residue (char), and the lower emission of pollutants into the atmosphere, e.g., SO2 and NOx, is a competitive solution compared to combustion process. Wood waste from alder and pine were analyzed. As part of laboratory tests, the elementary composition was determined, i.e., C, H, N, S, and O. The pyrolysis process was carried out at a temperature of 600 °C on an experimental stand for the conversion of solid fuels in a stationary bed. For the obtained data, using the Ansys Chemkin-Pro calculation tool, the detailed chemical composition of gaseous products of the pyrolysis process was modeled for a varying temperature range and residence time in the reactor. The studies have shown that for certain pro... [more]

In the world, as in Lithuania, there is a costant search for new crops suitable for energy conversion. The coarse-energy crops and their biomass studied for this paper were assessed in a comprehensive manner, i.e., not only their calorific value and ash content but also their ash melting properties and pollutants emitted during the thermochemical conversion. The calorific value of energy crops varies from 17.92 ± 0.32 to 18.50 ± 0.66 MJ kg−1 and decreases in the following order: A. dubia > M. giganteus > C. sativa. Ash content varies from 1.51 ± 0.03 to 3.36 ± 0.23% and decreases in the following order: C. sativa > A. dubia > M. giganteus. The lowest primary ash deformation (648 ± 8 °C) was recorded for C. sativa. Taking into account the specificity of our research and the changes in biomass ash content due to mineral nitrogen fertilization, it has been found that that higher levels of nitrogen fertilizers in the combustion products reduce CO and increase the total CO2 content of the c... [more]

Most studies on honeycomb catalysts have been conducted using simulation models and exhaust experiments from automobiles. Very few monolithic catalyst studies have been applied to the agricultural sector, especially the catalyst exhaust system for flue purification from the biomass industry. The importance of exhaust gas purification and particulate removal from biomass power plants has become critical for evaluating the performance and environmental sustainability of biomass combustion. This is one of the first studies to investigate the performance of honeycomb catalysts for the oxidation of flue (PM2.5), (CO), and (SO2) from a rice husk briquette combustion system. The experimental setup comprised a fixed-bed electric furnace, the catalyst, an aerosol sampler, and a flue gas analyzer. Rice husk (0.1 g/mL density) and rice husk briquettes (0.8 g/mL density), were burned at 600−1000 °C for 3 min. From the results, the catalyst CO conversion rate was 100% at the optimum heated temperat... [more]

Renewable energy sources and their part in the global energy mix are beneficial to energy diversification and environment protection. However, raw biomass is characterized by low heating value, hydrophilic properties, various mechanical durability, and the logistic challenges related to transportation and storage. One frequently used process of combined biomass valorization is torrefaction and pelletization, which increase the heating value, homogeneity, and hydrophobicity of the fuel. However, industrial clients need fuel characterized by favorable grindability, whereas, the individual clients (householders) need fuel with high mechanical durability. Due to the different expectations of final customers regarding biomass fuel properties, it is necessary to investigate the influence of the torrefaction on the mechanical durability of the pellets. In this paper, five various types of pellets and their torreficates (obtained at a temperature of 200 and 300 °C) were examined. Then the mech... [more]