A techno-economic analysis is performed on a negative emission power plant and a gas power plant with carbon capture. The two power plants are modelled in commercial software. The gas power plant with amine capture has been used as a reference to represent state-of-the-art power generation technology. The overall thermal efficiency for the negative emission power plant (sewage sludge as fuel) and the gas power plant (natural gas as fuel) with CO2 capture is estimated to be 35% and 54.3%, respectively. A dedicated experiment was conducted on a novel type of modular plasma gasifier with dual plasma sources in order to determine the mass and energy balance for further thermodynamic analysis. Both capital expenditures and operating expenses, as well as incomes from sewage sludge disposal and avoided CO2 emissions, have been included in the techno-economic analyses. The results show that the levelized cost of electricity of the negative emission power plant using an exhaust gas gasifier is comparable to the reference gas power plant with amine capture (107 vs. 91-95 & euro;/MWh), while the annual avoided CO2 emission of the negative emission power plant is considerably higher (1.67 vs. 0.41 Mt). A simple payback period of 8.5 years is estimated for a power generation of 142 MW when the exhaust gas gasifier is used. Due to the high electrical energy consumption and equipment cost, the levelized cost of electricity is much higher when the plasma gasifier is used. The value strongly depends on the income from sewage sludge disposal and avoided CO2 emissions. Further reductions of levelized cost of electricity are expected for the negative emission power plant with the development of the technology maturity.

Tomato waste is currently an untapped potential source of different bioactive compounds, including lycopene, polyphenols, polysaccharides, and proteins. Drying is an energy-intensive process with potentially significant environmental impacts. However, drying is a necessary pretreatment for tomato waste before lipid-soluble bioactive compounds can be extracted. This work attempts to optimise tomato waste drying from the point of view of minimising environmental impacts at an early stage of technology development by using prospective LCA as a tool for optimisation. A comprehensive approach is adopted, starting from experimental investigation, followed by modelling of process kinetics and extrapolating differences in resulting residence times into the size of equipment, which in turn influences LCA inventory, i.e., required size of equipment. Modelling showed that the modified Page model achieved the lowest square error when fitting to experimental data. The study determined that environmental impacts decreased with increasing drying temperature, owing to a decreased contribution from capital goods, which in extreme cases (drying at 75°C) could contribute as much as 36.9% of the climate change impact. The climate change impact could be decreased from 0.42 to 0.11 kgCO2eq per functional unit (1 kg of evaporated water) by replacing natural gas with biogas for the generation of heat for drying. However, other impact categories (eutrophication, ecotoxicity) showed a reverse trend, highlighting the need for further improvement in digestate and feedstock management in anaerobic digestion plants supplying biogas for the production of heat for such dryers.

Separate collection and treatment systems for municipal solid waste (MSW) are designed to support efforts in sustainability. Biowaste accounts for the majority of MSW; thus, its proper management is essential. This study analyzes the impact of the presence of composting or anaerobic digestion (AD) facilities on MSW management. The management systems in Poland with composting and AD facilities were compared. Five fractions, including mixed/residual waste and biowaste, were collected in the analyzed regions; however, the rules for sorting biowaste varied. A drop in the collected residual/mixed MSW was noticed (by 3.8% to 6.6% year-on-year), while the biowaste stream increased, resulting in a 4-10% increase in the share of biowaste. The proportion of the organic fraction in biowaste was found to be 85-88%, but the proportion of food waste was slightly higher in the region with an AD facility (by about 3%). Plastics were the primary contaminants, accounting for approximately 5.5%. The presence of AD facilities has a positive impact on MSW management, including higher biowaste collection levels (67.5 kg per person versus 48.1 kg per person). Furthermore, under comparable regional conditions, economic gains were observed, such as relatively lower gate fees for biowaste (about 57 EUR per ton versus about 62 EUR per ton) and greater differences in fees between biowaste and residual/mixed MSW (about 80 EUR per ton versus about 14 EUR per ton).

Biogas is a crucial renewable energy source, as it supports a circular economy by facilitating the efficient recovery of energy from organic waste through recycling. This study presents a comparative case study assessment of one agricultural and one municipal biogas plant regarding process stability, production efficiency, and digestate quality. The analysis was conducted at two full-scale anaerobic digestion (AD) facilities operating under different technological and feedstock conditions. The agricultural biogas plant, processing mainly maize silage and agri-food residues, demonstrated slightly higher biogas yields (average 127 m3/ton) and methane concentrations (53.7-55.1 %) compared to the municipal biogas plant treating selectively collected biowaste (116 m3/ ton and 50.4-52.3 %, respectively). Despite the municipal plant's higher operational complexity and purification requirements, both installations maintained stable digestion processes, confirmed by appropriate pH levels and acidity/alkalinity ratios. Digestate from both plants met the legal standards for use as a biofertilizer, though the agricultural digestate showed a higher nutrient content. The findings confirm that both agricultural and municipal full-scale AD configurations can operate as effective and stable methods for biowaste treatment and energy recovery, contributing to circular economy goals and climate neutrality.

In the valorisation of wet biomass, the improvement of dewatering capabilities plays an important role, due to copious amounts of heat required for thermal drying. This work aimed at determining of influence of hydrothermal treatment on mechanical dewatering of wet brewer’s spent grain (BSG) and assessing its hydrophobic character, by performing mechanical dewatering in a hydraulic press, as well as molarity of ethanol droplet tests of dry samples. Hydrothermal processing at 170 °C resulted in the lowest moisture content of the valorised material after mechanical dewatering, whereas an increase in the process temperature to 200 °C resulted in higher final moisture content, attributed to secondary chars increasing the hydraulic resistance of the filtration cake. HTC treatment changed hydrophylic biomass into moderately hydrophobic fines and slightly hydrophobic coarse particles, showing the influence of particle size on the contact angle. HTC treatment of BSG resulted in an increase in carbon content and improvement in terms of grindability of the material.

Italy stands as the largest producer of tomatoes in Europe, with a total area of approximately 75 thousand hectares dedicated to this crop. The environmental impact of tomato production is a growing concern, with many studies devoted to the carbon footprint associated with different cultivation practices. Pressure on the environment could be alleviated by turning waste from tomato processing into useful products, according to circular economy principles. Among many different substances, tomatoes contain significant amounts of carotenoids (e.g., lycopene) and proteins/peptides. This work proposes and evaluates a novel valorisation route for tomato waste, consisting of supercritical CO2 extraction followed by subcritical water extraction. Such an approach can enhance the recovery of lycopene, with its concentration in the recovered oil reaching 0.66 mg/g, due to its high solubility in lipid-like phases which are efficiently extracted by supercritical CO2. Subcritical water extraction of the residual solids allows the recovery of proteins and peptides.

Carbon black is a product with multiple applications, including use as an additive for tyres or plastics, as well as ink or toner. Current methods of carbon black production are based on incomplete combustion of fossil fuels, followed by quenching, resulting in a high carbon footprint and related emissions. Even though unintended, biodegradable bioplastics at the end of life still pose problems to waste management plants. Most notably, the time required for bioplastics to biodegrade is longer than the typical residence time in state-of-the-art processes, such as anaerobic digestion and composting. This causes incomplete degradation and reduces the efficiency of waste treatment facilities. This work provides an experimental evaluation of a novel method of production of carbon black, using bioplastic waste (namely, cellulose acetate) as a feedstock. The proposed system consists of hydrothermal carbonisation (HTC) and subsequent pyrolysis of separated solid products. The novel product exhibits morphology and structure similar to commercial carbon black and high thermal stability. BET surface area as high as 175 m2/g can be achieved by combining hydrothermal carbonisation performed at 250 °C followed by pyrolysis at 600 °C. Further increase in pyrolysis temperature provided no additional benefits and resulted in collapse of the pores within the mesoporous range, with detrimental influence on BET surface and pore volume.

Municipal solid waste (MSW) management is identified as a significant sustainability concern. Source segregation (SS) is the most effective method of managing MSW, and anaerobic digestion (AD) is the most efficient treatment method. The aim of this study was to analyze the impact of waste collection rules on the efficiency and performance of AD. The potential biomethane yields for SS-kitchen waste and SS-biowaste were calculated, determined in laboratory tests, and verified full-scale. The content of the organic fraction in SS-biowaste reached about 81 to 86%; however, regarding SS-kitchen waste, it reached almost 92%. The primary contaminants were plastics. The obtained biogas yield was slightly higher for SS-kitchen waste (136.2 m3/ton), compared to SS-biowaste (116.6 m3/ton). The pH values, acidity, and alkalinity indicated no risk of exploitation using both feedstocks. However, in the case of SS-kitchen waste, the acetic acid content was about 2.5 times higher than that of SS-biowaste. Furthermore, the acetic acid was noted in the outlet section (about 140–160 mg/kg), indicating no complete organic matter decomposition. Regarding SS-kitchen waste, the calculated methane yield reached 137.1 m3CH4/ton and laboratory tests showed a methanogenic potential of 129.7 m3CH4/ton, while at full-scale, it reached about 82.2 m3CH4/ton. The research confirmed that the SS of biowaste positively impacts MSW management by improving waste composition and increasing recycling possibilities. AD is an effective biowaste treatment process, allowing energy recovery from waste.

Solid recovered fuel derived from non-recyclable waste represents an alternative energy source suitable for use in waste incineration or combustion facilities. Its adoption reduces fossil fuel consumption in heat and electricity production, thereby mitigating associated environmental impacts. This study evaluates the environmental benefits of substituting coal with SRF in the energy mix of the Moravian-Silesian Region (Czech Republic), a post-coal region currently dependent on fossil fuels. A life cycle assessment (LCA) was conducted according to the methodology outlined in EN ISO 14040 and 14044 standards, using the PEF 3.0 method and OpenLCA software, assessing three SRF composition scenarios and four energy conversion efficiency scenarios (WtE and CHP). The study focuses on key environmental indicators, such as "climate change" and "resource use, fossils," which collectively represent over 70 % of the total environmental impacts. The findings reveal that integrating SRF into the region's energy mix has the potential to significantly reduce the environmental footprint of electricity and heat production. Specifically, the reductions in the "climate change" indicator range from 4.42 % to 35.7 %, while the overall "environmental footprint" indicator shows reductions between 10.86 % and 40.5 %. These findings confirm SRF's potential as a key tool in transitioning toward a more sustainable regional energy strategy.

Proper sewage sludge management is challenging due to legal requirements, environmental concerns, and logistical complexities. Steam gasification offers a promising solution by producing high-quality syngas. While research has largely focused on fixed bed gasifiers, their scalability limitations restrict their economic viability. Entrained flow gasifiers, scalable to hundreds of megawatts as demonstrated in coal gasification, present a practical alternative for large-scale bioenergy with carbon capture and storage (BECCS) applications. However, designing such systems requires precise modeling approaches. This study experimentally validates equilibrium models and a computational fluid dynamics (CFD) approach for steam gasification of raw sewage sludge and hydrothermally carbonized (HTC) sludge. HTC pretreatment improved syngas quality by facilitating the use of CO2 as a feedstock carrier for entrained flow gasifiers. Among the models tested, the CFD approach and a tuned semi-equilibrium model closely matched experimental data, with average absolute errors of 4.5 % and 2.9 % in mole fraction, respectively. Using a 3-m drop tube furnace, entrained flow steam gasification demonstrated the production of high-quality syngas and offering practical scalability. This scalability enables the development of efficient BECCS power plants with negative CO2 emissions, showcasing the potential of entrained flow gasifiers for sustainable energy and environmental management.

Solid recovered fuel (SRF) is highly suited for thermal treatment, but its low bulk density and other physical properties limit the number of compatible energy systems that can effectively process it. This study presents the findings on SRF energy utilisation, focusing on mechanical treatment and a novel approach to its small-scale co-combustion with certified softwood (SW) pellets and catalytic flue gas control. In this study, the processes of certified SRF feedstock characterisation and mechanical treatment were thoroughly examined. Unique SRF pellets of proper mechanical properties were experimentally prepared for real-scale experiments. Mechanical and chemical properties, such as mechanical resilience, toughness, moisture and heating value, were examined and compared with standard SW A1 class pellets. The prepared SRF pellets possessed an energy density of 30.5 MJ∙kg–1, meeting the strict requirements from multiple perspectives. The influence of pelletisation temperature on pellet quality was investigated. It was found that increased resilience and a water content of 1.59% were achieved at a process temperature equal to 75 °C. Moreover, the moisture resilience was found to be significantly better (0.5 vs. 14.23%) compared with commercial SW pellets, while the hardness and durability values were reasonably similar: 40.7 vs. 45.2 kg and 98.74 vs. 98.99%, respectively. This study demonstrates that SRF pellets, with their improved mechanical and energy properties, are a viable alternative fuel, from a technical standpoint, which can be fully utilised in existing combustion units.

The process of gasification is well-known; however, to this day, the applications of such facilities, especially off-grid small-scale units for direct electricity and char production, are scarce. In this study, an off-grid fixed bed downdraft gasification unit is studied from the gaseous/solid product character perspective. This unit represents a possible solution for the emerging call for sustainable decentralised energy sources. Softwood chips were utilised in this study, and their conversion into synthetic gas (direct electricity supply) and solid biochar was observed and analysed. The results show promising values of synthetic gas for potential utilisation in different applications outside the direct combustion process, such as microbial syngas fermentation, with a lower heating value equal to 6.31 MJ·m-3. It appears that during the steam activation process of biochar, both high-quality off-gas of more than 70%vol. H2 (excluding N2) and activated carbon of a specific surface area of 565.87 m2·g-1 can be collected. Further investigations have revealed specific degradation of chemical bonds and material morphology changes during steam gasification. The microporous structure and high specific surface area of the material make it an attractive material for further development as an adsorbent in sorption cooling devices. Therefore, the waste generated within the gasification process is minimised, and the potential of the obtained products will be valued in favour of the sustainability of the remote locations.

A significant increase in the use of hydrogen, expected to reach between 667 and 4000 TWh, is forecasted for the whole EU in 2050. Electrolysis is believed to be a “silver bullet” due to its synergy with the needs of the grid. However, biohydrogen generation could be complimentary to electrolysis since it does not depend on electricity prices. This review presents a comprehensive picture of the landscape in biohydrogen production, showing state-of-the-art research on different biohydrogen production processes and highlighting potential problems and shortcomings for different processes, including microbial-based production and thermal processes. The work shows that “colour coding” used nowadays is insufficient in terms of providing accurate information regarding the sustainability of particular biohydrogen production technologies. Instead, LCA can provide substantial information for each investigated process. However, there is a need for a wider scope of LCA studies since currently published studies present a syndrome of “carbon tunnel vision”, often ignoring impacts other than global warming. Moreover, studies often tend to exclude the impact of capital goods production, which might provide an incomplete overview of such technologies. Moreover, it should not be overlooked that biohydrogen is capable of achieving negative values of CO2 emissions if CCS is implemented.

The advancement of plasma technology is intricately linked with the utilization of computational fluid dynamics (CFD) models, which play a pivotal role in the design and optimization of industrial-scale plasma reactors. This comprehensive compilation encapsulates the evolving landscape of plasma reactor design, encompassing fluid dynamics, chemical kinetics, heat transfer, and radiation energy. By employing diverse tools such as FLUENT, Python, MATLAB, and Abaqus, CFD techniques unravel the complexities of turbulence, multiphase flow, and species transport. The spectrum of plasma behavior equations, including ion and electron densities, electric fields, and recombination reactions, is presented in a holistic manner. The modeling of non-thermal plasma reactors, underpinned by precise mathematical formulations and computational strategies, is further empowered by the integration of machine learning algorithms for predictive modeling and optimization. From biomass gasification to intricate chemical reactions, this work underscores the versatile potential of plasma hybrid modeling in reshaping various industrial processes. Within the sphere of plasma catalysis, modeling and simulation methodologies have paved the way for transformative progress. Encompassing reactor configurations, kinetic pathways, hydrogen production, waste valorization, and beyond, this compilation offers a panoramic view of the multifaceted dimensions of plasma catalysis. Microkinetic modeling and catalyst design emerge as focal points for optimizing CO2 conversion, while the intricate interplay between plasma and catalysts illuminates insights into ammonia synthesis, methane reforming, and hydrocarbon conversion. Leveraging neural networks and advanced modeling techniques enables predictive prowess in the optimization of plasma-catalytic processes. The integration of plasma and catalysts for diverse applications, from waste valorization to syngas production and direct CO2/CH4 conversion, exemplifies the wide-reaching potential of plasma catalysis in sustainable practices. Ultimately, this anthology underscores the transformative influence of modeling and simulation in shaping the forefront of plasma-catalytic processes, fostering innovation and sustainable applications.

The possibilities of pistachio shell biochar production on laboratory-scale gasification and pyrolysis devices have been described by several previous studies. Nevertheless, the broader results of the pistachio shell co-gasification process on pilot-scale units have not yet been properly investigated or reported, especially regarding the detailed description of the biochar acquired during the routine operation. The biochar was analysed using several analytical techniques, such as ultimate and proximate analysis (62%wt of C), acid–base properties analysis (pH 9.52), Fourier-transform infrared spectroscopy (the presence of –OH bonds and identification of cellulose, hemicellulose and lignin), Raman spectroscopy (no determination of Id/Ig ratio due to high fluorescence), and nitrogen physisorption (specific surface 50.895 m2·g−1). X-ray fluorescence analysis exhibited the composition of the main compounds in the biochar ash (32.5%wt of Cl and 40.02%wt of Na2O). From the energy generation point of view, the lower heating value of the producer gas achieved 6.53 MJ·m−3 during the co-gasification. The relatively high lower heating value of the producer gas was mainly due to the significant volume fractions of CO (6.5%vol.), CH4 (14.2%vol.), and H2 (4.8 %vol.), while hot gas efficiency accomplished 89.6%.

This study examines the impact of a waste-derived additive from alumina and shale oil production on the performance of coal combustion. The effects of individual additive components were investigated under oxidantlimited and oxidizing conditions using the isothermal flow reactor (IFR) equipped with gas analysers. The raw materials, as well as fly chars/ashes derived from the IFR, were characterized using standard physicochemical analysis, oxide analysis, oxygen functional group determination, the ash fusion test, thermogravimetry, scanning electron microscopy and energy dispersive X-ray spectroscopy. Results from experiments conducted under oxidant-limited conditions demonstrated that the analysed additive, at a 1% share, increased hydrogen content in char by over 3.5 times (from 600 ppm to 2160 ppm) and enhanced methane conversion by nearly 20%. Under oxidizing conditions, the additive reduced unburned carbon loss by approximately 50%, emissions of NOx from 400-460 ppm to 340-390 ppm and SO2 from 1410-1475 ppm to 1325-1410 ppm. The study emphasized the influence of moisture on thermochemical processes, confirming that a certain amount of water vapour accelerates the conversion of H2, SO2, and NOX. The analysis supported the commercial utilization of the additive from economic, environmental, and operational standpoints.

Current and future trends in the world population lead to the continuous growth of municipal waste volumes. Only in the EU-28 approx. 86 million tons of biowaste is produced yearly. On the other hand, the recent energy crisis calls for a fast transition towards more local and renewable energy sources. Most of this stream could be recycled through anaerobic digestion (AD) to produce energy and high-quality fertilizers. This paper presents a balance of dry anaerobic digestion of municipal biowaste based on three years of system monitoring in an industrial-scale AD plant. The results indicate that the average biogas production rate of 120 Nm3/ton of fresh waste can be achieved. Biogas utilization in combined heat and power (CHP) units leads to an overall positive energy balance at significantly reduced CO2 emissions. The overall CO2 emission reduction of 25.3–26.6% was achieved, considering that biogas utilization is environmentally neutral. Moreover, biowaste conversion allows digestate production to substitute mineral fertilizers in agriculture and other applications. It is beneficial for soil protection and a broader environmental perspective.

Around 40% to 60% of municipal solid waste originates from kitchens, offering a valuable resource for compost production. Traditional composting methods such as windrow, vermi-, and bin composting are space-intensive and time-consuming. Black soldier fly larvae (BSFL) present a promising alternative, requiring less space and offering ease of handling. This research encompasses experimental data collection, life cycle assessment, and machine learning, and employs the Levenberg–Marquardt algorithm in an Artificial Neural Network, to optimize kitchen waste treatment using BSFL. Factors such as time, larval population, aeration frequency, waste composition, and container surface area were considered. Results showed that BSFL achieved significant waste reduction, ranging from 70% to 93% by weight and 65% to 85% by volume under optimal conditions. Key findings included a 15-day treatment duration, four times per day aeration frequency, 600 larvae per kilogram of waste, layering during feeding, and kitchen waste as the preferred feed. The larvae exhibited a weight gain of 2.2% to 6.5% during composting. Comparing the quality of BSFL compost to that obtained with conventional methods revealed its superiority in terms of waste reduction (50% to 73% more) and compost quality. Life cycle assessment confirmed the sustainability advantages of BSFL. Machine learning achieved high accuracy of prediction reaching 99.5%.

One of the processes that can serve to valorise low-quality biomass and organic waste is hydrothermal carbonization (HTC). It is a thermochemical process that transpires in the presence of water and uses heat to convert wet feedstocks into hydrochar (the solid product of hydrothermal carbonization). In the present experimental study, an improvement consisting of an increased hydrophobic character of HTC-treated biomass is demonstrated through the presentation of enhanced mechanical dewatering at different pressures due to HTC valorisation. As part of this work’s scope, flashing-off of low-quality steam is additionally explored, allowing for the recovery of the physical enthalpy of hot hydrochar slurry. The flashing-off vapours, apart from steam, contain condensable hydrocarbons. Accordingly, a membrane system that purifies such effluent and the subsequent recovery of chemical energy from the retentate are taken into account. Moreover, the biomethane potential is calculated for the condensates, presenting the possibility for the chemical energy recovery of the condensates.