Solid Biofuel Production Research Articles

Investigation of Buckwheat Hulls as Additives in the Production of Solid Biomass Fuel from Straw

The aim of this study was to further increase the amount of straw that can be used to produce solid biofuels, as currently only about 130–140 thousand of the 3 million tonnes of straw collected annually in Lithuania are used for solid biofuel production. Therefore, the use of buckwheat hulls as an additive in solid biofuel production was investigated. Mixtures of wheat straw and buckwheat hulls were used for this research, with an increase in buckwheat hulls from 25% to 75% of the total weight of the mixture. Results of the analysis of the chemical composition, moisture, ash, and volatile matter content of the mixtures, as well as their ash properties, were compared with the corresponding results obtained with pure buckwheat hulls, wheat straw, and wood chips. It is observed an increase in all ash melting temperatures by increasing the portion of buckwheat hulls in the mixture. Additionally, the ash shrinkage starting temperature was shown to increase as the total content of buckwheat hulls also increased in the mixture. This increase ranged from 90 °C to 210 °C. Furthermore, the Cl concentration in fuel mixtures and the corrosion risk of equipment are accordingly reduced by using buckwheat hulls, as an addition that does not contain Cl.

Determination of combustion characteristics and kinetic parameters of Ulva lactuca and its biochar

Utilization of macroalgae, which accumulated in the coastal area and considered as waste by municipals, for biofuel production is a good solution putting forward for both waste management and meeting the renewable energy requirement. This study aims to investigate the use of Ulva lactuca collected from the Marmara Sea coast as a raw material for solid biofuel production. Therefore, in this study, the combustion characteristics of Ulva lactuca and its biochar were investigated by the thermogravimetric method, and kinetic parameters were determined by using Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods. When the obtained thermograms are examined, it was observed that the combustion of raw seaweed occurs in three phases, while the combustion of biochars occurs in two phases. As a result of the calculations, the combustion activation energies of macroalga and its biochar were found to be approximately 261 kJ/mol and 146 kJ/mol, respectively, using the KAS method. It was found that the values calculated using the FWO method were similar to the KAS method. These data show that biochar requires less energy than raw algae during combustion.

Продуктивність міскантусу гігантського та стан родючості ґрунту за внесення добрив

Miscanthus giant is a tall perennial herbaceous plant with a well-developed root system, which is used for biofuel production. The aim of the study was to establish the effect of gi-ant miscanthus in the first year of growing season on the state of soil organic matter, removal and balance of nutrients and biological productivity of crops for fertilization. A four-year survey of the condition of miscanthus plantations was conducted at ‘Veselo Podilska’ research and breeding station during 2016‒2019 in the forest-steppe zone of Ukraine. Indicators of biomass productivity of giant miscanthus and the state of fertility of the grant for fertilizer application in the area of the left-bank of the Forest-Steppe of Ukraine for the production of solid biofuels are characterized. In the first year of the growing season, giant miscanthus produces more organic matter in the root system than in its terrestrial biomass ‒ 2.5 and 1.6 tons of dry matter/ha, respectively. It was found that foliar fertilization with microfertilizers significantly increased the yield of terrestrial biomass of giant miscanthus in the background of mineral fertilizers. The highest biological yield of ground mass of giant miscanthus was achieved with the introduction of N60P60K60 and two foliar fertilization with microfertilizer Vympel-K, 0.5 l/ha: yield of terrestrial biomass ‒ 3.1 tons of dry matter/ha with the advantage of control without fertilizers ‒ 1.5 tons/ha. In the first year of cultivation miscanthus giant uses a small amount of nutrients from the soil: nitrogen ‒ 20.4‒33.8 kg/ha, phosphorus ‒ 3‒5.3 kg/ha, potassium ‒ 6.1‒12.4 kg/ha . The application of N30P30K30 ferti-lizers was sufficient to form a balanced and expanded balance of nutrients in the soil. The appli-cation of mineral fertilizers did not affect the dynamics of organic matter in typical chernozem. Growing giant miscanthus in the first year of the growing season ensured the stability of the or-ganic matter content in the soil at the level of 4.04‒4.11%. At the same time, the content of mobile phosphorus at the end of the growing season decreased by 17‒18 mg/kg, potassium ‒ by 13‒43 mg/kg of soil. Reducing the content of mobile forms of phosphorus and potassium in the soil at the end of the growing season leads to efficient use of plant nutrients, chemical transformation of phosphorus into insoluble compounds and non-exchange adsorption of potassium ions by the soil complex in the biocenosis of miscanthus.

Insights into the Product Quality and Energy Requirements for Solid Biofuel Production: A Comparison of Hydrothermal Carbonization, Pyrolysis and Torrefaction of Olive Tree Pruning

Insights into the Product Quality and Energy Requirements for Solid Biofuel Production: A Comparison of Hydrothermal Carbonization, Pyrolysis and Torrefaction of Olive Tree Pruning

ОПТИМІЗАЦІЯ ЕФЕКТИВНОГО ПРОЦЕСУ ГОРІННЯ МАЛОГАБАРИТНИХ ПАЛИВНИХ РУЛОНІВ ІЗ ЗАЛИШКІВ ПІСЛЯ ЗБИРАННЯ ЛЬОНУ ОЛІЙНОГО

Currently, the use of secondary agricultural raw material is a topical issue. There are various applications of agricultural crop residues possible, but they are finance- and energy-consuming. Burning crop residues is very harmful for the environment. One of the ways to solve the problem is the production of solid biofuel that can be used to heat buildings. The authors suggest producing solid biofuel in the form of small-sized fuel rolls / pellets (SFR), which are made of oleaginous flax residues. As a result of the conducted experimental investigations, the authors have proved the efficiency and the environmental safety of SFR consumption. The new fuel can be recommended if the requirement of efficient and ecologically safe combustion is met. Thus, the influence of small-sized fuel rolls’ properties on the process of their combustion as well as quantitative and qualitative analysis of the combustion gases from burning solid fuel made of oleaginous flax residues have been investigated. The paper presents the results proving that SFR combustion is the most efficient on condition of providing reduced moisture (10-12%) and reasonable density (80 kg/m3) in the process of pellet production. In addition, it has been determined that there is a significant reduction of harmful CO emissions and normalization of СО2 concentration. The application of the suggested solid biofuel can make it possible to solve the problem of using oleaginous flax residues and provide cheap fuel for household purposes.

Sustainable Production of Solid Biofuels and Biomaterials by Microwave-Assisted, Hydrothermal Carbonization (MA-HTC) of Brewers’ Spent Grain (BSG)

This work addresses the management of Brewers’ Spent Grain (BSG) using a state-of-the-art, microwave-assisted, hydrothermal carbonization (MA-HTC) process, for the production of hydrochar, i.e., a renewable solid biomaterial with many industrial applications. For the first time, a detailed relationship has been established between the processing conditions and the properties of the hydrochar via a thorough physicochemical characterization. The experimental results revealed that the temperature (180–250 °C) and reaction time (0–2 h) used in the MA-HTC process exerted a significant influence on the yield and properties of the hydrochar. An increase in these variables (process severity) diminished the hydrochar yield. However, such increments were beneficial to enhance the fuel properties of this product, as the proportions of O and C decreased and increased, respectively. As a result, this process was capable of transforming up to 47% of the original BSG into a high-energy hydrochar with a calorific value of 32 MJ/kg. The characterization of the hydrochar revelated that it was a mesoporous, hydrophilic, rough material, containing several cavities and oxygen functionalities on the surface. These features not only provide the hydrochar with a high aromatic character but also are fundamental for its potential applicability as a bioadsorbent material. An increase in the MA-HTC severity augmented the amounts of aliphatic and aromatic structures in the hydrochar as well as the roughness and the presence of cavities, thus highlighting the excellent flexibility of the process. Therefore, these promising results, together with the energy-efficient and bespoke nature of the MA-HTC process, which substantially reduces the reaction temperature and processing times in comparison to standard carbonization procedures reported to date, represent a step-change not only for the production of biofuels and biomaterials but also for the management of BSG.

Аналіз процесу сушіння енергетичних рослин під час виробництва твердого біопалива

The article presents an analysis of the stages of production of solid biofuels from energy plants and notes that the drying processes in technological processes consume up to 70 % of total energy consumption. The relevance and advantages of low-temperature drying are substantiated. Aim: intensification of the process of dehydration of energy plants, determination of rational parameters of the drying agent and dehydration conditions. Energy willow was used as an object of dehydration. Drying was carried out until the material reached a residual moisture content of 5...6 %. Studies on the effect of drying agent temperature on the kinetics of moisture exchange have shown that increasing the temperature from 80 °C to 100 °C enhances heat and mass transfer and reduces the process duration to 25 %. Increasing the specific load has a positive effect on the productivity of the drying plant and increases the amount of processed raw materials. The total duration of dehydration from the minimum load to the maximum increases by 3.5 times. The paper notes that a significant parameter of the impact on the kinetics of drying and increase the efficiency of the process is the method of grinding raw material. The most intensive mode corresponds to the method of grinding willow by combining abrasion and impact. With this method of grinding, the drying time is reduced from 15 % to 25 % compared to those considered. The established conditions and parameters of low-temperature drying provide intensification and efficiency of the process and obtaining dried energy willow with low and evenly distributed residual moisture.

Correlations between the compressive strength of the hydrochar pellets and the chemical components: Evolution and densification mechanism

Hydrochars of cotton stalk (CS) at the hydrothermal temperature of 180−280 °C and the retention time of 0−120 min were used for the purpose of developing fuel pellets. Subsequently, the physical properties and combustion characteristics of the hydrochar pellets were evaluated to assess the solid biofuel production potential. Then, the hydrochar samples were analyzed by FTIR, TGA, XRD, and SEM, aiming to investigate the evolution mechanism of the chemical compositions (hemicellulose, cellulose, and lignin) with the increasing hydrothermal temperatures and their effects on the compressive strength of the hydrochar pellets. The results indicated that the hydrochar pellets exhibited higher fixed carbon contents, elevated heating values, enhanced physical properties, and more stable combustion characteristics than the raw biomass pellets. Moreover, the skeleton structure of the crystalline cellulose was the critical factor affecting the compressive strength of the hydrochar pellets. In parallel, lignin was observed to be beneficial for fabricating solid bridges and also exhibited a substantial influence on the bonding performance. However, the crystalline cellulose completely decomposed into amorphous carbon, and the high carbonization degree of the lignin caused it to lose its bonding capacity, which led to a sharp decrease in the compressive strength of the hydrochar pellets pretreated at 280 °C to 2.9 MPa, lower than the CS pellets (4.2 MPa). Finally, the pictorial depiction of the chemical components’ structural characteristics exhibited in the hydrothermal carbonization process was displayed along with their influences on the hydrochar densification process.

Co-hydrothermal carbonization of food waste with yard waste for solid biofuel production: Hydrochar characterization and its pelletization

In this study, Co-HTC of food waste with yard waste was conducted for biofuel pellets production, and also to understand any possible synergy between two feedstock types. The calorific value of blended raw feedstock was 13.5 MJ/kg which increased to 27.6 MJ/kg after Co-HTC at 220 °C for 1 h. Energy yield and fuel ratio calculated was 45% and 0.65 respectively. Hydrochar produced demonstrated a stable combustion profile as compared to reactive combustion profile for raw samples. The blend of food and yard waste hydrochar was easily pelletized, and its pellets showed improvement in mechanical properties as compared to pellets made from mono-substrate((food waste) hydrochar. Pellets produced from the blend of food and yard waste hydrochar showed higher energy (46.4 MJ/m3) and mass density (1679 kg/m3) as compare to the pellet produced from food waste hydrochar alone. Tensile strength obtained for the blended hydrochar pellet was 2.64 MPa while same for the pellets produced from food waste hydrochar alone was 1.30 MPa. In addition to improving hydrophobicity, soften lignin from yard waste also helped in binding the food waste hydrochar particles together within the pellets matrix during heated pelletization. The results presented in the study indicated that in the presence of all favorable conditions, there is a potential that approximately 11% of the global coal consumption could be replaced by the combustion of hydrochar produced from food and yard waste globally.

Удосконалення елементів технології вирощування проса прутоподібного в умовах Лісостепу України

Goal. To improve the elements of technology, methods of soil preparation and sowing of seeds, to increase the productivity of growing biomass of rod-shaped millet for the production of solid biofuels in the Western Forest-Steppe, taking into account the biological characteristics of plant development. Methods. Field, laboratory, measuring, comparative, statistical, and dispersion. Results. The results of research on improving the elements of technology for growing biomass of rod-shaped millet in the Western Forest-Steppe of Ukraine — pre-sowing soil preparation and sowing of millet seeds together with seeds of the beacon culture, which allowed early tillage and significantly reduce weeds. The highest biomass productivity of rod-shaped millet and energy yield (377.7 GJ/ha) was at a row spacing of 30 cm. Conclusions. Rod-shaped millet in the first year of the growing season is sensitive to soil moisture and temperature, which significantly influences the friendliness of the germination of seedlings. Favorable conditions for growing biomass of rod-shaped millet in the Western Forest-Steppe zone can be significantly improved by using 3-time pre-sowing tillage with harrows and sowing seeds with an optimal row spacing of 30 cm together with seeds of beacon white mustard.

EFFECTIVE ORGANIZATION OF WASTE USE OF AGRICULTURAL ENTERPRISES IN THE FORMATION OF ENERGY AND ENVIRONMENTAL SAFETY

The article substantiates that the effective use of organic waste for further processing today is a prerequisite for the development of agricultural enterprises, their competitive advantages and ensuring energy and environmental security. The basic principles of enterprise waste disposal are identified, which include: maximum use of on-farm resources, ensuring the economic efficiency of the technologies used, and compliance with veterinary and sanitary requirements. The most common methods for processing organic waste of agricultural enterprises, which include energy and non-energy areas, are investigated. The waste from the plant growing industry can be used for energy purposes in two directions: direct burning in order to obtain heat and electric energy, as well as for the production of solid biofuels. Livestock waste can be used to produce another type of biofuel – biogas. The non-energy direction of the use of organic waste from agricultural enterprises provides the production of secondary products (pulp, paper, cardboard), feed, bedding, compost. It is substantiated that the directions of use of crop waste, which is now preferred by agricultural enterprises, are mainly non-energy (like roughage, litter, as fertilizers) and ineffective (such feed is of little value for highly productive animals, enterprises do not comply with the technology of smelling residues, which minimizes positive effect). Various methods of processing waste products (secondary products) of the livestock industry are analyzed: composting, vermicomposting, composting using gumivit, infusion, and biogas production. A comparison of the economic efficiency of traditional and bioenergy manure utilization at a conditional enterprise is made. It is proved that modern methods of manure utilization with biogas production have advantages because they have an environmental effect, can provide energy autonomy due to the refusal to purchase fuel, electricity, it is possible to increase the efficiency of activities through the sale or own use of biological fertilizers, and the sale of other by-products.

Evaluation of different sweet sorghum cultivars for bioethanol yield potential and bagasse combustion characteristics in a semiarid Mediterranean environment

Sweet sorghum is a promising bioenergy crop that has great potential for bioethanol production due to its wide adaptability, high sugar yield, and drought tolerance. The objective of the present study was to evaluate the bioethanol yield potential and bagasse combustion characteristics of 13 sweet sorghum cultivars in a semiarid Mediterranean environment. The results showed that M81-E was the most promising cultivar for whole-crop bioethanol production due to it having the highest total ethanol yield, at 6885 L ha−1. Dale exhibited the highest juice ethanol yield (1764 L ha−1), with the lowest lignin (8.9%) and ash (2.31%) contents. The bagasse moisture contents of the cultivars were quite high, which varied between 66.61% and 70.51%, indicating that the bagasse must be dried before it is used as a feedstock for direct combustion. In this context, M81-E and Top76-6 were less suitable for solid biofuel production from their bagasse, because their comparatively long growth cycle did not allow for the open-air drying that was required to decrease the moisture content to an optimal level at a low cost. On the other hand, Umbrella was a promising cultivar in the study, because it achieved the highest dry bagasse yield (16.5 t ha−1) and a total ethanol yield (6350 L ha−1) comparable to that of Dale. These results suggested that sweet sorghum had a high potential for bioethanol production in a semiarid Mediterranean environment, but cultivation of the most suitable cultivars is the first step to ensure sustainability.

Comparison on solid biofuel production from wet and dry carbonization processes of food wastes

In this research, three categories of food waste (dried cabbage, chicken, and rice) were separately subjected to hydrothermal carbonization (HTC) under 180 °C, 200 °C, and 220 °C and pyrolytic carbonization (PC) under 200 °C, 250 °C, 300 °C, 350 °C, and 400 °C for solid biofuel production, respectively. Carbonization pathways, solid yield, high heating value (HHV), the transformation of nitrogen and ash, and char reactivity were detailly compared. After both pre-treatments, the ratio of fixed carbon (FC) to volatile matter (VM) of solid increased with the increase of the temperature, except for HTC of chicken. HTC of chicken led to more VM in solid product with very low solid yield and significantly lower N content. HTC-chars showed higher VM even at the same temperature as PC despite more severe carbonization (higher C content). Even though the N content can be reduced by both HTC and PC, HTC showed superiority than PC in regards to reducing the N content, indicating the potential to mitigate the N-related emission. Even though the HHV of HTC char was higher than that of PC char at the same pretreatment temperature, the product yield of the former one was much lower, resulting in lower energy yield in HTC char. The alkaline index (AI) can be used as the main factor for comparisons of gasification reactivity between (1) HTC and PC-chars and (2) Among HTC-chars from different temperatures. PC-chars presented higher reactivity than HTC-chars for all types of feedstock when considering at the same pre-treatment temperature at 200 °C. In conclusion, the key parameters including VM, the solid yield, HHV, the N content reduction, and char reactivity can be adopted to well evaluate the solid biofuel qualities production from different processes of HTC and PC, respectively.

Hydrothermal treatment of sewage sludge to produce solid biofuel: Focus on fuel characteristics

This research aimed to investigate the optimal conditions for solid fuel production from sewage sludge by hydrothermal carbonization (HTC) at relatively low temperatures and then to determine the fuel properties of the obtained hydrochar. HTC experiments were conducted at 100–200 °C for 0, 30 and 60 min, respectively. The maximum hydrochar yield, about 890 g/kg, was obtained at 150 °C for 60 min. However, the hydrochar produced at 150 °C for 30 min had the highest higher heating value (HHV) of 16.17 MJ/kg. The produced hydrochars under different reaction conditions are competitive to the low-rank coal like peat. Results from this work suggest that HTC at 150 °C for 30 min is the most suitable condition for solid biofuel production from the sampled sewage sludge only, achieving an energy recovery efficiency of 0.92. Under the above HTC conditions, the produced char demonstrates a high grindability highlighting its suitability as solid fuel for energy generation.

Biomass Torrefaction for the Production of High-Grade Solid Biofuels: a Review

Torrefaction of biomass materials has received a tremendous attention over the years due to its ability to produce a high-grade solid biofuel with enhanced durability, excellent grindability, higher bulk density and calorific value, and greater energy density, as compared to the original untreated biomass material. It is a mild pyrolysis treatment technology under inert atmosphere which can improve the chemical and physical properties of raw biomass through the elimination of oxygen, reduction of moisture content, and change of chemical compositions. When raw biomass is mildly pyrolyzed in a default-oxygen or N2 atmosphere at moderate temperatures, the properties of raw biomass including low calorific value, hydrogen-carbon ratio, hygroscopicity, and grindability can be significantly enhanced. In the present review, the operating mechanism of different torrefaction processes including wet, dry, and ionic-liquid-assisted torrefaction is analyzed and discussed. More importantly, the reactor design for commercialization purpose, reaction kinetics and mechanism, economics, and sustainability of biomass torrefaction is discussed in detail. This review is extended to the torrefaction of agro-residue biomass since torrefied agro-residue-based pellets can be produced from agro-residues. The various technological applications of biomass torrefaction are also reviewed and the prospects in ensuring the continuous production of high-grade fuels are summarized.

PRODUCTION OF SOLID BIOFUELS FROM GRAIN PROCESSING WASTES

The article is devoted to the issues of solid biofuel production. The classification of biomass used in the production of solid biofuels by origin is given. The main types of grain waste in the southern region for the production of solid biofuels are identified.The article analyzes the soybean market in the world and Ukraine, shows the trend of growing soybean production, which is caused by the growing demand for food and feed purposes. Soybean yield indicators in Ukraine are analyzed and it is found that Kherson region is one of the leaders of soybean yields for 2019. It is shown that in soybean cultivation in Ukraine a considerable amount of secondary resource is obtained - straw, as a by-product of crop production. It is established that the average yield of rice of Kherson region prevails in Ukraine, a large amount of rice husk is formed during processing of raw rice. Physico-mechanical properties of rice husk and soybean straw have been determined. The possibility of production of fuel briquettes from the waste was considered, technological scheme of production of fuel briquettes from waste, which are formed at the enterprises of processing industry and by-products of crop production is given. The technology of production of fuel briquettes from soy straw and rice husk was introduced at the enterprise of Kherson region, which is engaged in cultivation and processing of soybeans and rice. Quality indicators of fuel briquettes were determined: humidity, ash, sulfur, carbon content, volatile matter yield and specific combustion heat. It is established that the quality of fuel pellets is significantly influenced by humidity, degree of grinding and physical and chemical properties of raw materials. When the moisture content of raw materials more than 14% decreases the density of the granules and, due to the evaporation of moisture, cracks appear in the granules, which reduce their strength. With the reduction of the average particle size of the biomass to 2 mm, the quality of the fuel products increases, but the fine fraction of the biomass of the matrix is erased. The heat of combustion of the obtained solid briquettes exceeds the normative values of European standards at a level not lower than 18 MJ / kg. Ash content (0.5 %), normalized by European standards, is practically unavailable for Ukrainian producers, fuel briquettes made from soy straw and husks have higher normalized ash values in accordance with 7.0 and 14.0 %, which reduces their quality indicators.

POTENTIAL AND PROSPECTS FOR USING AGRIBIOMASS FOR ENERGY IN UKRAINE

Purpose of the work is to identify promising directions for using agribiomass for energy in Ukraine. Current state and prospects for the development of this segment of bioenergy are considered. Analysis of the strategic goals for bioenergy development set by the National Renewable Energy Action Plan until 2020 and Energy Strategy of Ukraine until 2035 shows that only wide involvement of agribiomass in the country's fuel and energy complex can ensure attainment of these goals. Ukraine has considerable potential of agricultural biomass. According to data of 2018, it is 10.1 Mtoe, which is 44% of the total bioenergy potential. The main constituents of agribiomass potential are cereal straw and by-products of grain corn production. Today, of the various types of agribiomass, sunflower husk is most actively used for energy: more than 63% of its potential. Utilization of the potential of other types of agricultural residues is between 0 and 3%. For Ukraine, the most promising direction is priority use of corn stover for energy. Feasibility study of corn stalks harvesting as well as production of briquettes and pellets from them was performed. Main factors affecting the cost-effectiveness of projects on solid biofuel production are cost of raw materials, manufacturing line productivity and sale price of the finished product. Results of the feasibility study show that corn briquettes and pellets can be competitive in the biofuel market of Ukraine, and their production can be a profitable business project.

Enhanced fuel characteristics and physical chemistry of microwave hydrochar for sustainable fuel pellet production via co-densification

Microwave assisted hydrothermal treatment (MHTC) was compared with torrefaction in terms of carbonization efficiency and physicochemical characteristics of char products. The utilization of produced char was optimized for composite solid biofuel production. The results show that MHTC significantly improved the binding capability of the microwave hydrochar (MHC) particles during co-densification with unprocessed biomass and coal. One possible contributor to the improved binding is the pseudo lignin formed during the MHTC, which led to a better interlocking of the feedstock particles and promoted the solid bridge formation. Composite pellet prepared with 80 wt% of torrefaction char (TC-120), 10 wt% of microwave hydrochar (MHC-30), and 10 wt% of Coal-04 showed a higher heating value of 24.54 MJ/kg and energy density of 26.43 GJ/m3, which is significantly higher than that of the raw cotton stalk pellet (16.77 MJ/kg and 18.76 GJ/m3, respectively), showing great promise as a solid biofuel. The moisture resistance and oxidation reactivity are also significantly improved. The results demonstrate that MHCs provides dual functionalities in acting as binder and fuel promoter in the production of composite biofuel. This study can provide new insight into the unique functions of MHC during fuel application, which demonstrates the great potential of applying MHTC in energy recovery from lignocellulosic biomass.

Decision Support System for the Production of Miscanthus and Willow Briquettes

The biomass is regarded as a part of renewable energy sources (RES), which can satisfy energy demands. Biomass obtained from plantations is characterized by low bulk density, which increases transport and storage costs. Briquetting is a technology that relies on pressing biomass with the aim of obtaining a denser product (briquettes). In the production of solid biofuels, the technological as well as material variables significantly influence the densification process, and as a result influence the end quality of briquette. This process progresses differently for different materials. Therefore, the optimal selection of process’ parameters is very difficult. It is necessary to use a decision support tool—decision support system (DSS). The purpose of the work was to develop a decision support system that would indicate the optimal parameters for conducting the process of producing Miscanthus and willow briquettes (pre-comminution, milling and briquetting), briquette parameters (durability and specific density) and total energy consumption based on process simulation. Artificial neural networks (ANNs) were used to describe the relationship between individual parameters of the briquette production process. DSS has the form of a web application and is opened from a web browser (it is possible to open it on various types of devices). The modular design allows the modification and expansion the application in the future.

Hydrothermal co-carbonization of sewage sludge and high concentration phenolic wastewater for production of solid biofuel with increased calorific value

Hydrothermal carbonization has proven to be an effective method to convert sewage sludge into solid carbon-rich hydrochar, of which the high ash content is generally regarded as limiting factor for energy-related potential application. Hydrothermal co-carbonization of sewage sludge and high concentration phenolic wastewater was firstly investigated in this study as a scenario for production of clean solid biofuel with increased calorific value and decreased ash content, by means of polycondensation reactions between phenols and highly reactive intermediates of biopolymers in sewage sludge. Results showed that addition of phenolic wastewater into sewage sludge led to a substantial increase of hydrochar yield (1.83–31.11%) and higher heating value (1.01–10.01%) and a remarkable decrease of ash content (1.39–25.68%). The reaction temperature and residence time had a complicated impact on the contribution of phenol to hydrochar production. An increase in phenol mixing ratio was beneficial to the improvement of mass yield and higher heating value but showed a less influence on the reduction of ash content. The synergistic effects between phenols and sewage sludge on the production of solid biofuel were closely related to the phenolic species, which followed the order in the aspects of hydrochar yield increase and ash content decrease: phloroglucinol > p-nitrophenol > m-cresol > phenol. The changes of phenols content in liquid phase and variations of functional groups in hydrochars implied that phenols interacted with sewage sludge and incorporated into hydrochars during the hydrothermal co-carbonization. TG-DSC confirmed the improved combustion reactivity of the phenols-sludge-derived hydrochars.