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Abstract: The processing of agricultural crops results in waste, which is a potential energy resource for alleviating commercial energy supply problems to agricultural-led economies like Tanzania. The energy content of the individual agricultural waste is largely dependent on its chemical composition (C, H and O) and it is negatively affected by the inclusion of inorganic elements and moisture. In this work, fifteen tropical agricultural wastes emanating from export crops for Tanzania were analyzed. The methods used to analyze involved performing proximate and ultimate analysis for determining the biomass composition. Thermal degradation characteristic was established to five selected wastes (coffee husks, sisal bole, cashew nut shells, palm stem, and bagasse) using a thermogravimetric analyzer type NETZSCH STA 409 PC Luxx at a heating rate of 10K/min. On the basis of elemental composition, the palm fibre and cashew nut shells exhibited high energy content due to their higher H:C ratio with relatively low O:C ratio. Results of the thermal degradation characteristic study showed that the cashew nut shells were the most reactive feedstocks due to their highest overall mass loss and lowest burnout temperatures of 364°C. Further, kinetic studies done to the five tropical biomass feedstocks under the pseudo single-component overall model established the activation energy for the bagasse, palm stem, and cashew nut shells to be 460kJ/mole, 542kJ/mole, and 293kJ/mole, respectively. The respective activation energies for coffee husks and sisal bole were 370kJ/mole and 239kJ/mole. With the exception of the sisal bole, which exhibited zero order reaction mechanism, the remaining materials´ reaction mechanism was of first order. These experimental findings form a basis for ranking these materials for energy generation and provide necessary input to equipment and process designers. [ABSTRACT FROM AUTHOR]

• MSW gasification was performed under air and steam in a fixed-bed gasifier. • Naphthalene is the most stable compound in secondary tar thermal cracking. • Corona plasma-aided thermal cracking achieved naphthalene complete removal at 800 °C. • With a fixed energy input, the SEI increased when temperature increased. • Corona and plasma cracking have a synergistic effect below 800 °C. Gasification has been proposed as a good solution for recovering energy from waste and biomass in the form of syngas. However, the presence of tar limits syngas applications. Tar model molecules have been removed by cold plasmas up to 400 ° C, but to avoid syngas cooling tar removal above 600 ° C is required. To investigate tar removal by cold plasma at higher temperatures, two sets of experiments were done, one to identify tar composition from MSW gasification, and a second one to crack in a nanosecond-pulsed corona plasma at high temperatures the most refractory tar compound found, naphthalene. In this paper, we report the first results of cold plasma for tar cracking at temperatures up to 1100 ° C, revealing that this tandem can remove naphthalene completely at 800 ° C, compared to the 1000 ° C needed in case of thermal cracking alone. The synergy between plasma and thermal cracking is driven by higher energy densities when temperatures increase. However, this synergy stops when thermal cracking reactions predominate. [ABSTRACT FROM AUTHOR]

Catalyst research on reforming processes for syngas production has mainly focused on the active metals and support materials, while the effect of the catalyst's geometry on the reforming reactions has been poorly studied. The application of 3D-printed materials with enhanced geometries has recently started to be studied in heterogeneous catalysis and is of interest to be implemented for reforming biomass and plastic waste to produce H 2 -rich syngas. In this study, a geometry-enhanced 3D-printed Ni/Al 2 O 3 /FeCrAl-based monolithic catalyst with a periodic open cellular structure (POCS) was designed and fabricated. The catalyst was used for batch steam reforming biomass pyrolysis volatiles for syngas production at different parameters (temperature and steam-to-carbon ratio). The results showed complete reforming of pyrolysis volatiles in all experimental cases, a high H 2 yield of ≈ 7.6 wt% of biomass was obtained at the optimized steam-to-carbon ratio of 8 and a reforming temperature of 800 ° C, which is a higher yield compared to other batch reforming tests reported in the literature. Moreover, CFD simulation results in COMSOL Multiphysics demonstrated that the POCS configuration improves the reforming of pyrolysis volatiles for tar/bio-oil reforming and H 2 production thanks to enhanced mass and heat transfer properties compared to the regular monolithic single-channel configuration. [Display omitted] • A 3D-printed catalyst was tested in steam reforming of biomass pyrolysis volatiles. • Biomass pyrolysis volatiles were successfully reformed completely into syngas. • The highest H 2 yield obtained was around 38 mmol g−1 biomass (7.6 wt% of biomass). • CFD results show the 3D-printed catalyst has improved heat and flow properties. [ABSTRACT FROM AUTHOR]

• Different integration scenarios are proposed for DRI production using biosyngas. • Mature fluidised bed gasifiers (TRLs 9) are considered for producing biosyngas. • The novel biosyngas DRI route can compete with other existing and emerging routes. • Carbon negative is possible as up to 1.13 t CO 2 per t DRI can be captured and stored. Bioenergy with carbon capture and storage (CCS) in iron and steel production offers significant potential for CO 2 emission reduction and may even result in carbon-negative steel. With a strong ambition to reach net-zero emissions, some countries, such as Sweden, have recently proposed measures to incentivise bioenergy with CCS (BECCS), which opens a window of opportunities to enable the production of carbon-negative steel. One of the main potential applications of this route is to decarbonise the iron reduction processes that account for 85 % of the total CO 2 emission in the iron and steel plants. In this study, gasification is proposed to convert biomass into biosyngas to reduce iron ore directly. Different cases of integrating the biomass gasifier, Direct Reduced Iron (DRI) shaft furnace, and CCS are evaluated through process simulation work. Based on the result of the work, the proposed biosyngas DRI route has comparable energy demand compared to other DRI routes, such as the well-established coal gasification and natural gas DRI route. The proposed process can also capture 0.65–1.13 t of CO 2 per t DRI depending on the integration scenarios, which indicates a promising route to achieving carbon-negative steel production. [ABSTRACT FROM AUTHOR]

[Display omitted] • An integrated process integrates to treat the digestate and produce H 2 -rich syngas. • Applying HTC as a pretreatment will decrease the syngas yield. • The use of dewatering as a pretreatment will decrease the H 2 fraction of the syngas. • Pretreatment combined with HTC and dewatering has the best process efficiency. A novel process to produce a H 2 -rich syngas from a high moisture-containing agricultural waste digestate is proposed. This process combines the use of hydrothermal carbonization (HTC), dewatering, pyrolysis, and catalytic reforming. Due to the feature of the high moisture content in the digestate, the effect of the HTC and dewatering on the process performance is of interest, and four scenarios were considered. Furthermore, three pyrolytic temperatures were chosen to understand the effect of pyrolysis conditions on the produced H 2 -rich syngas. A life cycle assessment was conducted to investigate the environmental impact of the proposed process. Results show that the application of HTC technology, increases the process efficiency, produces less syngas from one ton of digestate, lowers the cumulative energy demand and the negative carbon emissions. When the dewatering technology is used, the syngas yield is promoted but the H 2 concentration in the syngas is reduced. The H 2 to CO molar ratio reaches the maximum value of 9.2 when using a 450 ˚C pyrolysis temperature, by only using HTC. When the combining process of HTC and dewatering is used, it results in the highest process efficiency, but the smallest relative negative CO 2 equivalent emissions by treating one ton of dry digestate. [ABSTRACT FROM AUTHOR]

We have investigated and modeled the injection of biomass into blast furnaces (BF), in place of pulverized coal (PC) from fossil sources. This is the easiest way to reduce CO 2 emissions, beyond efficiency-improvements. The considered biomass is either pelletized, torrefied or pyrolyzed. It gives us three cases where we have calculated the maximum replacement ratio for each. It was found that charcoal from pyrolysis can fully replace PC, while torrefied material and pelletized wood can replace 22.8% and 20.0% respectively, by weight. Our energy and mass balance model (MASMOD), with metallurgical sub-models for each zone, further indicates that (1) more Blast Furnace Gas (BFG) will be generated resulting in reduced fuel consumption in an integrated plant, (2) lower need of limestone can be expected, (3) lower amount of generated slag as well, and (4) reduced fuel consumption for heating the hot blast is anticipated. Overall, substantial energy savings are possible, which is one of the main findings in this paper. Due to the high usage of PC in Sweden, large amounts of biomass is required if full substitution by charcoal is pursued (6.19 TWh/y). But according to our study, it is likely available in the long term for the blast furnace designated M3 (located in Luleå). Finally, over a year with almost fully used production capacity (2008 used as reference), a 28.1% reduction in on-site emissions is possible by using charcoal. Torrefied material and wood pellets can reduce the emissions by 6.4% and 5.7% respectively. The complete replacement of PC in BF M3 can reduce 17.3% of the total emissions from the Swedish steel industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • A pyrolytic kinetic predictive model was constructed by using machine learning. • The established model shows good accuracy for the prediction with an R2 of 0.9964. • The carbon content had the most influence on the pyrolytic activation energy. • Partial dependence analysis results give new insights into lignocellulose pyrolysis. An in-depth knowledge of pyrolytic kinetics is vital for understanding the thermal decomposition process. Numerous experimental studies have investigated the kinetic performance of the pyrolysis of different raw materials. An accurate prediction of pyrolysis kinetics could substantially reduce the efforts of researchers and decrease the cost of experiments. In this work, a model to predict the mean values of model-free activation energies of pyrolysis for five types of feedstocks was successfully constructed using the random forest machine learning method. The coefficient of determination of the fitting result reached a value as high as 0.9964, which indicates significant potential for making a quick initial pyrolytic kinetic estimation using machine learning methods. Specifically, from the results of a partial dependence analysis of the lignocellulose-type feedstock, the atomic ratios of H/C and O/C were found to have negative correlations with the pyrolytic activation energies. However, the effect of the ash content on the activation energy strongly depended on the organic component species present in the lignocellulose feedstocks. This work confirms the possibility of predicting model-free pyrolytic activation energies by utilizing machine learning methods, which can improve the efficiency and understanding of the kinetic analysis of pyrolysis for biomass and fossil investigations. [ABSTRACT FROM AUTHOR]

Highlights: [•] The performances of torrefaction based co-firing power plant are simulated by using Aspen Plus. [•] Mass loss properties and released gaseous components have been studied during biomass torrefaction processes. [•] Mole fractions of CO2 and CO account for 69–91% and 4–27% in total torrefied gases. [•] The electrical efficiency reduced when increasing either torrefaction temperature or substitution ratio of biomass. [Copyright &y& Elsevier]

[Display omitted] • Biomethane produced from organic fraction of municipal solid waste(OFMSW) • 151.4 kg CH 4 and 355.6 kg negative emissions are obtained from 1 ton dry OFMSW. • The process reach energy efficiency of 0.40 and cost of 6.74 MJ to store 1 kg of CO 2. • Operating expenses calculation result indicates a positive net profit. The use of bioenergy with carbon capture and storage (BECCS) is vital to reaching the desired climate goals. This study proposed a novel process combining anaerobic digestion, pyrolysis, catalytic reforming and methanation (APRM) to produce biomethane and to capture carbon emission from the organic fraction of municipal solid waste (OFMSW). The evaluation of the process was conducted by using modelling software and techno-economic analysis. The process modelling and evaluation result showed that 151.4 kg CH 4 and 355.64 kg stored carbon emission can be produced from 1 ton dry matter of OFMSW with an energy efficiency of 0.40. 6.74 MJ electricity was required to capture 1 kg of CO 2 via the proposed process. The energy balance of the pyrolysis reaction was investigated. The sensitivities of the pyrolysis temperatures, dewatering technologies and conversion of catalytic reforming on the process performance were analyzed. The result also indicated a positive net profit when using the APRM process to treat the OFMSW based on the calculation of operating expenses and revenue, when the CO 2 negativity can be sold as commodity. [ABSTRACT FROM AUTHOR]