Net Calorific Value Research Articles

Techno-Economic Feasibility Study of a Combined Cycle Power Plant Utilizing Natural Gas and Biogas from Cattle Manure Co-firing in South Central Timor

The low electrification ratio in East Nusa Tenggara, particularly in South Central Timor Regency, poses a significant issue. Despite reaching an electrification rate of 92.33%, efforts to achieve 100% are ongoing. South Central Timor as one of the largest cattle farming areas in Indonesia, with its large grasslands and dry climate ideal for cattle farming, has substantial biogas potential from beef cattle manure through anaerobic digestion. Biogas from beef cattle manure has a net calorific value of 18.36 MJ/kg. Based on projections for 2027 using best fit regression, the average daily manure production capacity from 260,217 cattle in South Central Timor is 7.55 kilotons, which is equivalent to approximately 301,852 m3 of biogas. A small-scale combined cycle power plant (CCPP) is proposed to capitalize on this, with a capacity of 20.73 MW and a net thermal efficiency of 55.33%. The plant’s fuel mix will consist of 30% biogas and 70% natural gas by mass, with a fuel mass flow rate of 1 kg/s. The levelized cost of electricity (LCOE), internal rate of return (IRR), and net present value (NPV) obtained from the economic calculations are Rp1,126.76/kWh, 9.62%, and 222 billion IDR with assumptions of a 20-year plant lifetime, an electricity selling price of Rp1,352/kWh, and a discount rate of 6%. The plant is expected to reduce carbon emissions by 61 kilotons annually, while creating new job opportunities in the energy, livestock, and logistics sectors.

Energy Recovery from Municipal Sewage Sludge: Combustion Kinetics in a Varied Oxygen–Carbon Dioxide Atmosphere

Energy from municipal sewage sludge can be obtained by applying a thermal conversion method. In this study, the combustion kinetics of municipal sewage sludge were analyzed in an O2/CO2 atmosphere. Studies were conducted in different gaseous atmospheres consisting of varying proportions of oxygen and carbon dioxide. The participation of oxygen was as follows: 20, 40, 60, 80 and 100% vol. The experimental temperatures varied from 873 to 1273 K. The experimentally obtained results helped establish the basic kinetic parameters, such as the reaction order n, factor Ko and activation energy Ea of sludge grains. The values of the activation energy Ea and Ko were, respectively, 46 kJ/mol and 0.0127 mg/m2sPa. They show that the limiting factor of combustion is the diffusion of oxygen and that combustion reactions take place in the outer layer of the unreacted core. Therefore, sludge is promising for energy recovery because it has quite a high net calorific value (NCV) and a high gross calorific value (GCV). The GCV was 14.1 MJ/kg and the NCV was 12.8 MJ/kg. The experimental studies with a wide range of process parameters helped to create an array of apparent reaction rates as a function of the temperature and oxygen concentration, showing the significant effect of oxygen on the apparent reaction rate, in contrast to the effect of temperature.

Biomass Resources from Vineyard Residues for the Production of Densified Solid Biofuels in the Republic of Moldova

This paper explores the utilization of biomass resources derived from vineyard residues for producing densified solid biofuels in the Republic of Moldova, with the aim of quantitatively and qualitatively evaluating the residue from vine pruning, focusing on the feasibility of its use as raw material for the production of briquettes and pellets. The methodology includes the analysis of statistical data, as well as experimental investigations conducted at the Scientific Laboratory of Solid Biofuels of the Technical University of Moldova. Waste biomass samples were collected from various vineyards in the different districts of all three regions of the country, focusing on regions with significant plantations. Both quantitative and qualitative aspects of the biomass were assessed, considering the moisture content, calorific value, and ash content. It was found that about 1013 kg/ha of waste biomass is generated from the pruning of technical grape varieties with a net calorific value of 15.6 MJ/kg at a moisture content of 10 wt.% and about 1044 kg/ha with a calorific value of 16.4 MJ/kg from the table ones; both with an average ash content of 3 wt.%. The results indicated that vineyard pruning residues in the Republic of Moldova could provide a substantial biomass source, with an estimated total energy potential of approximately 370 TJ/y (80% located in the Southern region); they also highlighted the need for technological advancements and quality assurance procedures through which to ensure the efficiency and sustainability of biofuel production. The conclusions emphasize the numerous benefits of utilizing viticultural residue, both economically and ecologically, contributing to the sustainable development of the viticulture industry in the Republic of Moldova, as well as environmental protection.

Energy usage of spruce with waste face masks and spent coffee grounds as fuel in a pellet boiler

It is necessary to reduce dependency on fossil fuels for heating and waste generation, while also utilizing the energy potential of waste materials. One possibility is to create fuel pellets where waste makes up a small proportion so that the properties of the wood are not significantly altered with. This article investigates the energy usage of pellets containing spent coffee grounds (5 % or 10 %) and waste face masks (5 % or 10 %), with spruce sawdust as the primary input material (80 % or 90 %). The elemental, thermogravimetric, calorific value, mechanical durability, emission and performance characteristics, and ash melting temperatures of the pellets were evaluated during the experiment. The results were compared with respect to pure spruce sawdust pellets and the specified limit values for wood pellets in commercial and residential applications as specified in ISO 17225 [18]. Both tested samples met the element content limit (N, S, Cl, As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn) for the highest quality grade (A1). No significant amounts of harmful elements were detected. The samples also complied with the limits of moisture content, ash content, and net calorific value (also known as lower calorific value). All samples met the emission limits in their respective classes (3, 4, or 5) according to STN EN 303-5+A1 [35]. However, the samples failed to meet the limit values for mechanical durability and ash melting temperatures. Despite this, the manufactured pellet samples represent a suitable fuel product for combustion purposes as a more sustainable thermal energy fuel.

Cenozoic tectonic evolution of the main lignite-rich grabens in Poland. Part 2. Tectonics versus autocompaction and compaction

This paper is a continuation of the previous one (Widera, 2024. Acta Geologica Polonica, 74 (1), e2). A new, alternative interpretation of the tectonic development of two lignite-rich deposits in the Lubstów and Kleszczów grabens in central Poland is presented. The maximum thickness of lignite mined from both deposits is >86 and >250 m, respectively. These grabens were selected for detailed tectonic analysis because syn-depositional or post-depositional tectonic uplift is undeniably evident. The current study focuses on the distinction between tectonic subsidence/uplift and autocompactional subsidence, and on the timing of their occurrence. Such a research approach allows for the presentation of new conceptual models of Cenozoic tectonic evolution during the formation of the third, very thick, Ścinawa lignite seam (ŚLS-3) and the second Lusatian lignite seam (LLS-2). As a result, it is shown here that the magnitude of both the downward and upward tectonic movements are significantly smaller than previously thought. This new interpretation is also confirmed by the low rank of lignite coalification and the net calorific value of the ŚLS-3 and LLS-2.

Influence of Hydrogen induction on performance and emission characteristics of an agricultural diesel engine fuelled with cultured Scenedesmus obliquus from industrial waste

The use of microalgae in waste water treatment has been recognised as crucial for managing and treating effluent from industrial sources. Present study used Scenedesmus obliquus (SO) strains in industrial waste cultured medium, grown algae were collected and dried, further with dried mass to algae bio fuel by transesterification process. Four fuel blends were created by adjusting the SO concentration from 10% to 40% by volume. Then SO blend was examined with impact of hydrogen induction on compression ignition engine. The addition of H2 to SO biodiesel enhances its net calorific value because of its high calorific content.Adding H2-inducted SO proportion to diesel reduces HC, NOx, and CO levels, with a negligible performance dip. At full loads, SO40 showed a significant improvement in emission levels, with a 19.81% reduction in NOx, a 51 ppm drop in HC and 1.146% dropobserved in CO compared to diesel. For the SO10 mix, BTE and BSEC were found to be 2.86% and 2103.77 kJ/kW-hr, respectively, superior to other SO blends. Subsequently, it is of crucial significance to acknowledge the significance of the potential those microalgaeprovides for the production of sustainable energy through the reprocessing of industrial effluents.

On-farm energy input-output and economic analysis of important essential oil-bearing Mint species in subtropical India

Mint species are grown worldwide and known for their medicinal and aromatic properties however, studies on its energy assessment are very scarce. This study quantifies the energy input–output relationship of herbs and essential oil production of different mint species (M. arvensis, M. piperita, M. spicata, M. cardiaca and M. citrata) which were commercially grown in subtropical India. This study proposes for life cycle assessment and their effects on environment. The energy inputs and outputs were significantly varied with mints species. Results showed that mints essential oil production used more energy than herbs, and M. citrata utilizes the highest energy in both cases. Fire wood requirements for essential oil extraction accounts maximum (59.16 %) energy input. Mint herbs and essential oil yields were recorded higher in M. citrata (23.14 t ha−1), and M. arvensis (143.2 kg ha−1), respectively. Energy yields were estimated highest in M. cardiaca (herbs), and M. arvensis (essential oils), and required net calorific values were tested by automated advanced oxygen bomb calorimeter. Overall, M. arvensis showed the best results in energy production (0.07 kg MJ−1), profitability (0.27), net return (17156.40 MJ ha−1), and energy use efficacy (1.27) for mint herbs production. However, for essential oil production M. cardiaca performed well. This study revealed that mint herbs production was more energy efficient than essential oils extraction although essential oil production is fiscally secure.

Comparative Experimental Assessment of Pollutant Emission Behavior in Combustion of Untreated and Thermally Treated Solid Biofuels from Spruce Chips and Rapeseed Straw

Biomass energy for heating is going to be part of the spectrum of renewable energy sources. However, biomass combustion produces emissions of various pollutants with negative effects at both local and global scales. To reduce some of the locally important pollutant load, thermally treated biomass fuels may offer a partial solution. In this study, two biomass feedstocks, i.e., spruce chips and rapeseed straw, were thermally treated at 300 °C to produce biochars. Subsequently, both original materials and biochars were burned in a 25 kW retort combustion device. In both cases, the biochar showed lower emissions of carbon monoxide and nitrogen oxides, usually almost across the whole range of tested combustion conditions. In total, for the emission production per unit of net calorific value, the spruce biochar showed reductions in CO and NOx productions of 10.8% and 14.5%, respectively. More importantly, in rapeseed straw biochar, the difference was more pronounced. The total production was reduced by 28% and 42%, again in CO and NOx emissions, respectively.

Water Hyacinth (Eichhornia crassipes) As a Possible Alternative Energy Source: A Case Study for INSEE Cement Manufacturing Plant in Puttalam, Sri Lanka

Cement manufacturing is typically energy-intensive process and currently using alternative fuels partially or totally to replace fossil fuels to reduce the energy and environmental costs. Biomass is one of the main alternative fuel utilized by the cement industry with the potential to replace up to 20% of total energy demand. Water hyacinth (WH) is a problematic invasive alien species in aquatic ecosystems of all climatic zones in Sri Lanka. Because of it is non-edible, rapid growth, and freely available in larger quantities, WH has the potential to be used as biomass energy. Several countries have been studied for WH as feedstock for bioenergy production while physical and chemical composition of WH biomass has been tested by many researchers. However, biomass physiochemical properties may be varied by different place and conditions and there is no significant study for industrial application of WH biomass to burn in cement plant kiln as alternative energy source. Thus, this study aimed to elucidate the potential of WH biomass as an alternative energy source for the INSEE cement plant in Puttalam. The study was conducted in three selected reservoirs namely, Tabbowa reservoir (TR), Murukkuwatawana reservoir (MR), and Nawadankulama reservoir (NR) located in Puttalam district Northwestern province of Sri Lanka. The quantity of fresh and dry WH biomass was estimated with the WH covered area and fresh and dry weights of WH in unit area.WH covered area of in each reservoir during 2020 and 2021 was digitized directly in Google earth satellite images using Google Earth Pro software with help of visual interpretation techniques. WH biomass per unit area were measured by the subjective sampling method. WH samples from each reservoir were collected for analyzing biomass, and to determine the fuel characteristics such as net calorific value (NCV), Chlorine and Sulfur content, moisture, volatile matter, fixed carbon, and ash content. According to the results, the fresh WH biomass was recorded as 692.62, 389.85, 23.58 tons in 2020 and 3570.82, 584.53, 33.31 tons in 2021 in the TR, MR, and NR respectively, while the dry WH biomass was recorded as 41.65, 24.65, 1.31 tons in 2020 and 214.74, 36.96, 1.85 tons in 2021 in the TR, MR, and NR respectively. NCV of the WH composite sample was 12.02 MJ/kg. Moisture content, ash content, chlorine and sulfur content were recorded as 13.56%, 10.95%, 1.06%, and 0.14% respectively. Except for chlorine content, other parameters agreed with the acceptable limits for using WH as an alternative energy source for cement industry. To replace 1 ton of coal, 2.2 tons of dry WH were required from 35 tons of fresh WH biomass while to produce 1 ton of clinker, 0.32 tons of dry WH were required from 5.2 tons of fresh WH biomass. Since relatively large quantities are freely available and with high volatile content and calorific value, WH is suitable as an alternative energy source for cement industry. However, economic feasibility should be studied prior to the commercial application.
 Keywords: Alternative fuel, Biomass, Water hyacinth, Calorific value

Changes in the Characteristics of Pine Logging Residue during Storage in Forest Stands

A significant amount of logging residue is produced during roundwood harvesting. Logs are often left in forest sites due to, for example, ecological or logistical aspects. Taking into account the fact that the number of studies focused on changes in the properties of the residue is very low, it was decided to conduct research on the effect of a three-year storage period in forest stands on the chemical properties and energy potential of the wood. The research design allowed for the determination of changes during up to three years of storage. The performed analysis showed a highly negative impact on the characteristics of the material. These adverse effects were probably caused by the activity of microorganisms such as fungi and bacteria, as evidenced by the increased concentrations of ergosterol and low-molecular-weight organic acids. Moreover, it was found that wood stored for three years was characterized by a lower cellulose content; an increased percentage of lignin; a reduced content of sterols (desmosterol, stigmasterol, lanosterol and β-sitosterol) and phenolic acids; and reduced antioxidant activity, as determined with the ABTS+ method. Storing logs also led to a reduction in the energy potential of the residues, as shown by a reduction in net and gross calorific value and an increased ash content.

Characterization of fuel composite obtained by the mixing of biomass and coal

ABSTRACT This research investigates the potential of biomass-coal blends as an alternative fuel source, focusing on coal from Darra Adam Khel, Cherat, Harnoi, and Daola in the KPK province of Pakistan and Parthenium weed biomass. The study assesses the impact of varying biomass ratios on proximate analysis (net calorific value (NCV), sulfur content, volatile matter, ash content, and moisture content) and calorific values of the composite fuel. Results reveal a linear NCV decline with increasing biomass, affecting high NCV coals less. Daola and Darra coal, starting at 30.43 and 31.32 MJ/kg, decreased to 20.15 MJ/kg and 19.71 MJ/kg with 66% biomass. Sulfur content, notably high in high NCV coals, significantly reduces with biomass; Darra coal decreases from 3.31% to below 1% with 66% biomass. Volatile matter uniformly increases with incremental biomass, enhancing combustibility. Cherat coal, initially at 8% volatile matter, rises to 50% with 66% biomass. Biomass effectively reduces ash content, particularly beneficial for low NCV coals. Harnoi coal, starting with 73% ash content, decreases to 30% with 66% biomass. However, biomass addition raises moisture content due to challenges in removing moisture from Parthenium weed. In summary, these findings optimize biomass-coal blends for enhanced fuel performance, address environmental concerns, and improve combustion efficiency, highlighting their potential as sustainable and eco-friendly energy sources.

Is the assimilation to a solid recovered fuel a viable solution for automobile shredder residues’ management?

Directive 2000/53/EC and the European Circular Economy Package (2018) required the Member States to take all the necessary measures to reach the reuse-recycling goal of 85% for end-of-life vehicles (ELVs). In 2019, Europe achieved 89.6% of reuse-recycling, but most EC countries are still not completely compliant, Italy standing, for example, at only 84.2%. For this reason, actions are necessary to increase reuse-recycling for the waste generated in the operations of ELV shredding and separation, known as automobile shredded residues (ASRs). This study was aimed at assessing if the assimilation of ASRs to a solid recovered fuel (SRF) was a feasible solution. That would allow the waste to lose its status (end-of-waste, EoW), thus increasing the recycling rate. The assimilation of ASRs to SRFs requires the compliance with a series of parameters, namely net calorific value (NCV), content of chlorine (Cl), mercury (Hg) and selected heavy metals. The above-mentioned parameters were analyzed in the principal ASR fractions, namely textile, plastic and foam rubber, found in the samples collected during four sampling campaigns (2017–2021) performed at the same ELV treatment plant. Notwithstanding the great variability observed in the four samples, the results of the analyses revealed that the three fractions were compliant with NCV, Cl and Hg content. Conversely, the heavy metals' content was found a more critical parameter, in fact only the plastic fraction was suitable for SRF assimilation. Textiles presented criticality for the content of copper (Cu), nickel (Ni) and antimony (Sb). The heavy metals' contamination of foam rubber was found to be strongly related to particles' dimensions. A model which put particle size and metals’ content into relationship was developed and validated. Removing particles of <40 mm significantly improved the quality of the material, however the content of Cu and Ni remained a critical issue for particles up to 200 mm. The SRF assimilation of the plastic fraction would increase the reuse-recycling rate of approx. 2.4–3.3%, thus allowing the achievement of the EC goals concerning the ELV management.

Comparison of energy potential of the eucalyptus globulus and the eucalyptus nitens.

In this work a power characterization of adult stages of the species Eucalyptus globulus and Eucalyptus nitens has been made. The study has been made in six different plantations in Cantabria (North coast of Spain), located at a latitude 43º28'N, and a longitude 3º48'W. The region has approximately 30,000 Ha dedicated to the growth of Eucalyptus. After the collection of samples they were weighed, analyzed and burned, resulting a mean net calorific value of 17,384 kJ/kg and 17,927 kJ/kg for the E. globulus and E. nitens, respectively. Finally, the economic and environmental consequences that the crop of these species would suppose for the region of Cantabria were analyzed.

Refuse-derived fuel (RDF) production and analysis in mechanical-biological treatment (MBT) plant from the municipal solid waste

This study reports on the potential of refuse-derived fuels (RDF), which are produced from Sulaimani Municipal solid waste (MSW) using a biodrying process. Plastic, organic wastes, iron materials, and textiles were used in the formulation of RDF samples. A sample of raw MSW material was collected comprising of 40.6% organic, 29.3% plastic, 6.3% Textiles, 5.1% paper, 3.1% wood, 4.6% glass and stone, 5.2% iron containing materials, and 1.3% others. Physical and chemical properties of the RDF were investigated, including its moisture, ash, total chlorine, and heavy metal content with, calorific value. Based on the experimental results, RDF produced from MSW can be classified into net calorific and total chlorine content values NCV 2 and Cl 4 respectively. In accordance with the European Committee for Standardization (CEN standard), the results of this preliminary investigation of RDF samples made from non-biodegradable and non-recyclable MSW fractions, is necessary to analyze a larger pool of samples in order to project appropriate RDF energy-recovery-enhancing composition.

Substituting Solid Fossil Fuels with Torrefied Timber Products.

As a push towards alternative and renewable resources for heat and power generation, biomass and thermally treated fuels from biomass may be viable options in the upcoming economic reality. This study the verified mass and energy balance of spruce woody biomass after low temperature pyrolysis between 250 and 550 °C. The results showed that low-temperature pyrolysis can yield high-grade biochar suitable for substitution of fossil fuels. Crucially, the net calorific value of biochar processed at 350 °C substantially exceeded that of brown coal. An economic analysis was carried out on the assumption of the current economic reality in the Czech Republic. It was shown that even if the price of the biochar slightly increased, it would still be beneficial to invest in torrefaction technology over paying carbon credits.

Online characterization of solid biofuels via pocket sized and low-cost near-infrared devices during small-scale boiler operation: Model development, evaluation and application tests

Optimal boiler settings are required to ensure high efficiencies during biomass combustion and to enable compliance with emission thresholds despite lower and fluctuating fuel qualities. Thus, an affordable and simple near-infrared retrofit solution for online fuel characterization was developed and tested to allow for automatic adjustments of the boiler control with respect to actual characteristics of the used fuel assortments. To this end, a low-cost online near-infrared spectroscopy device (SCiO™, Consumer Physics), with investment costs less than 1000 € was employed. Partial least squares regression models based on 13 different spectral preprocessing methods for the prediction of moisture, ash, nitrogen and potassium content, as well as the net calorific value were developed and validated in the lab. The resulting model predictions of biomass properties agree in terms of root mean square error and R2 with the reference values obtained from laboratory analysis. Furthermore, a near-infrared retrofit solution was successfully coupled to the fuel feeding system of a commercially available small-scale biomass boiler for automatic and continuous operation. The automatically predicted values obtained by the near-infrared retrofit solution during continuous boiler operation are stable while the predicted values for moisture and net calorific value are in the range of the reference values obtained from the laboratory analysis but with a small offset. Non-reliable results were obtained for ash and nitrogen content.

Synergy of blending HEFA with alternative petroleum fractions

Jet fuel is the fastest-growing oil-based commodity. As it is difficult to substitute it with other energies, more attention is being paid to sustainable aviation fuels (SAFs). Hydrogenated esters and fatty acids (HEFAs) dominate SAF now. The jet fuel consumption forecasts show that the share of petroleum hydrocarbons in jet fuel will remain high until 2050. As oil consumption will decline with electromobility, the availability of straight-run kerosene for jet fuel will also decline. For this reason, the utilization of alternative petroleum fractions, such as hydrocracking kerosene (Jet HC) or hydrotreated heavy FCC naphtha (FCC HN), and their miscibility with HEFA have been studied. These components were generally blendable with HEFA. All properties were linearly dependent on the HEFA content, with the exception of the smoke point. Taking into account the Jet A-1 requirements, only Jet HC met them completely. Since the components have opposing properties, blending them has opened an application window in jet fuel, wider for blends of HEFA with Jet HC (0–68 vol% HEFA) and narrower for HEFA with FCC HN (73–81 vol% HEFA). The limitations were the low density of HEFA and the high density, the high aromatic content, the low smoke point, and the low net calorific value of FCC HN. To expand the application window of FCC HN in jet fuel, further research will focus on the hydrogenation of aromatics.

Irrigation in Jatropha curcas L. cultivation and its effect on biomass for bioenergy generation

The use of biomass as a source of bioenergy has intensified in recent years and has gained strength in replacing fossil fuels and their derivatives. Jatropha curcas L. oil is currently used as a raw material for the production of biodiesel through the physical extraction of the fruit, generating a large amount of waste. The heterogeneity characteristics of these materials impose the need for thermal pre-treatments for their recovery, such as torrefaction. Thus, this study aimed to investigate the biomass of Jatropha curcas as affected by water availability and its response to the torrefaction process. This research analyzed the biomass physical, chemical, and energy characteristics. TGA/DTG evaluated the thermo-degradation profile, and infrared spectroscopy (FTIR) determined the aromatic chemical structure. The fresh biomass of epicarp and cake presented different behaviors regarding water availability conditions, as variations in lignin contents from 29% to 2.7% and 30.9%–5.7%, respectively, and extractive range from 45.3% to 19.8% and 44.6%–21.6%, respectively. Torrefaction contributed to the increase in physical-chemical characteristics such as lignin and fixed carbon levels, from 29% to 82.4% and 19.8%–52.7%, respectively, and net calorific value of biomass, valuing them for energy use, as well as to decrease in the content of volatile materials from 80.7% to 71.8%. Using renewable biomass of Jatropha curcas cake and epicarp for energy purposes contributes to the reduction of environmental impacts by reducing the disposal of these residues in the environment, providing a sustainable and more efficient destination.

Production and characterisation of solid waste-derived fuel briquettes from mixed wood wastes and waste pet bottles

Wood waste and waste Polyethylene Terephthalate (PET) bottles are two of the solid wastes posing severe challenges to waste management facilities and constituting nuisance to humans and the environment in Nigeria due to poor management. These wastes could be utilized to produce solid biofuels for various energy applications to reduce CO2 emissions. This study, therefore, aims to investigate the potential of converting these wastes locally into solid waste-derived fuels (SWDF) briquettes in a bid to present an alternative approach to managing them. Four types of SWDF briquettes were produced from mixed wood waste and waste PET bottles in blend ratios of 100:0, 60:40, 50:50, and 40:60 using a screw press briquetting machine with single extrusion die. The effect of PET plastic amount on different properties, such as net calorific value, ash content, durability, and density, of the produced briquettes was investigated. In addition, obtained results were compared with the quality standards of densified fuels specified by the European Pellet Council. to ascertain the quality of the produced SWDF briquettes. The results revealed that the SWDF briquettes made only from mixed wood waste exhibited the lowest calorific value (17.15 MJ/kg) and highest ash content (2.74 %), while the SWDFs made from blends of mixed wood waste and PET bottles had higher calorific values (17.85–20.77 MJ/kg) and lower ash contents (1.05–1.37 %). Moreover, except for density and chlorine content (<750 kg/m3 and <0.03 wt% respectively), all the produced SWDFs complied with the quality standards of densified fuels specified by the European Pellet Council. These results suggest that these blends could yield SWDFs with improved quality and combustion properties, and could present a new way of managing these solid wastes.

Valorization of olive mill wastewater via autothermal reforming for hydrogen production

Olive mill wastewater (OMW) is an effluent of the olive oil industry that is extremely pollutant. Current solutions are either costly or inefficient. In this study, autothermal reforming (ATR) is presented, for the first time, as a solution to this problem, capable of high organic load removal, renewable hydrogen production and thermally neutral operation. The tests were conducted with a ruthenium-nickel catalyst, doped with La2O3, on a SiO2 support. Different operating conditions were tested (T = 400–700 °C and O2/C = 0.0–0.5 mol O2.mol C−1) and a comparison with traditional reforming (TR) was provided. Characterisation of the catalyst was conducted through temperature-programmed oxidation and inductively coupled plasma - optical emission spectroscopy. The catalytic tests showed hydrogen yields – up to 66.8 % for TR and 52.0 % for ATR – with high rates of organic pollutant load removal (always above 98 %, as inferred from the total organic carbon analyses). Furthermore, an energy balance revealed that ATR releases high amounts of energy, up to 272 kJ·molOMW−1, whilst TR has high energy demand, of up to 360 kJ·molOMW−1. In terms of the amount of heat released during the reaction and the net calorific value of the hydrogen produced, it was found that the ATR at 500 °C with O2/C = 0.25 had the best performance, with a total output of 1695 kJ·molOMW−1.