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• Biomass conversion is characterized by devolatilization and extinction times. • Biomass residence time increases with decreasing air flowrate and increasing biomass load. • Increasing biomass load increases the char yield and heat loss during devolatilization. • Correlations are given for predicting biomass residence time, char yield and specific heat loss. Gasification of biomass in bubbling fluidized beds can be limited by accumulation of unconverted char particles during the process. The amount of unconverted biomass depends on the residence time of the fuel particles. This study demonstrates a method for measuring the biomass residence time over the conversion period at a given air flowrate and a given amount of biomass in a bubbling bed using the variation of bed temperature and fluid pressure recorded over time. The results show that biomass conversion is characterized by the devolatilization and extinction times. The two biomass residence times increase with decreasing air flowrate and increasing amount of biomass charged in the bed. The amount of unconverted char between the two characteristic times also increases with decreasing air flowrate and increasing biomass load. The total heat loss during the devolatilization is observed to increase with increasing air flowrate and amount of biomass in the bed. Correlations are proposed for predicting the mean biomass residence time, the amount of unconverted char particles and the devolatilization heat loss at a given operating condition. The results of this study can be used in determining the bubbling bed properties and solid circulation rate required to decongest the accumulated char particles in the bed. [ABSTRACT FROM AUTHOR]

Abstract For operational control and design of a fluidized bed reactor containing different types of solid particles, the bed void fraction and minimum fluidization velocity are vital parameters. This paper demonstrates a method for predicting the void fraction and minimum fluidization velocity of different binary mixtures of particles with improved accuracy. A new model for predicting the void fraction is presented. This model is non-linear and continuous, and it is developed by introducing a packing factor and establishing a mass balance between the solid phases in the packing environment. The results show that the model can accurately predict the void fraction of a binary mixture where the particles are well mixed, partially mixed or segregated. Using this void fraction model and the Ergun equation of pressure drop, the minimum fluidization velocity can be predicted with mean errors of 15.2% for a mixture of two inert materials and 7.0% for a mixture of biomass and inert particles. Graphical abstract Unlabelled Image Highlights • A new model for predicting the void fraction of a binary mixture was proposed. • For a well-mixed binary mixture, the void fraction can be predicted with an error of 1.5%. • Using the void fraction model and the Ergun Equation, accurate U mf can be obtained. • The U mf prediction error for a biomass-sand mixture is 7.0%. [ABSTRACT FROM AUTHOR]

This paper deals with marine plastic debris and its collection and recycling methods as one possible answer to the rising amount of plastic in marine environments. A novel approach is to use energy recovery, for example pyrolysis of marine plastic debris into high-energy products. Compared to other thermal processes, pyrolysis requires less technical effort and the end products can be stored or directly reused. In order to design such an onboard pyrolysis reactor, it is necessary to know more facts about the feedstock, especially the thermochemical behaviour and kinetic parameters. Therefore, a thermogravimetric analysis was carried out for three selected plastic sizes with a temperature range of 34–1000 °C. The results obtained from TGA showed the same curve shape for all samples: single stage degradation in the temperature region of 700–780 K with most of the total weight loss (95%). Small microplastics had an average activation energy of 320–325 kJ/mol. [ABSTRACT FROM AUTHOR]

The direct storage of biologically stable pyrolysis char in soils is discussed as a low-tech below zero emission technology option with positive side-effects. A rotary kiln pyrolysis process, which has already been successfully applied at industrial scale before, is selected as the reference technology. Cotton stalks are considered as feed for the pyrolysis plant, representing a typical agricultural by-product with short rotation times. The plant efficiency is calculated for the case that the thermal energy that runs the pyrolysis process is provided by combustion of a part of the pyrolysis gas, while pyrolysis oil is provided as a product. The remaining pyrolysis gas powers a gas engine-based combined heat and power (CHP) island. 100% of fuel power fed with the biomass are distributed as follows (based on the lower heating value): 52% stay in the biochar, 13% in the pyrolysis oil, 10% are converted to electric power in the CHP plant, and, finally 15% are available as heat at a temperature span between forward and back flow of 100 °C/70 °C and may be used on-site for drying of agricultural products and pyrolysis feedstock. A rough comparison of the proposed process to biomass power generation substituting coal-fired power generation shows that the net effects on the carbon balance are comparable, but additional carbon-neutral energy streams are generated in the pyrolysis case. [ABSTRACT FROM AUTHOR]

Deployment of fossil fuels to quench the energy demand of the world's rising population results in elevated levels of greenhouse gas (GHG) emissions, especially CO 2 , which in turn is responsible for undesirable climate change. This necessitates a shift toward cleaner energy resources such as hydrogen. Enhanced hydrogen production via steam reforming of diverse fuels (methane, biomass, organic wastes, etc.) with in-situ CO 2 -sorption seems to be a promising alternative. Leading-edge, innovative and eco-friendly pathways coupled with high process efficiencies are needed for the development and growth of this technology. This review article evaluates the fundamental concepts such as criteria for CO 2 uptake, mechanisms, thermodynamics and kinetics of the water gas shift reaction along with different modeling methods for sorption enhanced processes. Moreover, research works carried out worldwide at lab-scale coupled with process development and demonstration units are discussed as a means to encourage this pathway for H 2 generation. Furthermore, light is shed on techno-economics as an approach to improve the viability and sustainability of the proposed technology. This paper analyzes different dimensions of the CO 2 -sorption enhanced process to promote it as a potentially carbon-neutral and eco-friendly pathway for hydrogen production. [ABSTRACT FROM AUTHOR]

• Hybrid bio-share energy systems offer a high potential associated with raw material price and conversion technology. • Waste biomass can significantly contribute to hybrid electrification. • A simulation tool using HOMER Pro-was successfully set-up and a mathematical model to calculate the range of system capacities. • An optimized system includes PV, biomass and grid connection. • PV module as well as biomass costs are the most sensitive parameters. Increasing household energy demand in the countries of the global south and the lack of conventional fuels and their high prices is forcing local authorities to look for alternatives. Based on the example of the city of Gaza, the primary renewable energy sources are large volumes of biomass, particularly waste-derived, which causes environmental and health damage, as well as abundant amounts of solar radiation. Hybrid renewable energy system (HRES) of solar and biomass is proposed, providing sustainable electrification for highly populated communities. By reviewing the literature studies on the electrification systems consisting of biomass and solar energy systems in the Middle East and North Africa (MENA) countries, and with respect to the corresponding technologies applied, we decided to incorporate a biogas engine generator. Simulation experiments are conducted by HOMER Pro-software of the residential district average daily demand is about 1074 kWh/day, and peaks of 84.5 kW p. The grid-connected system utilises renewable resources through photovoltaic panels and a biogas generator. Pre-mathematical model to evaluate the system components capacities is provided with different zones of load profile to achieve optimum solution of the biomass contribution and reveals at least $2.30 M net present cost (NPC) and $0. 438/kWh cost of energy (CoE). [ABSTRACT FROM AUTHOR]

Abstract: The dual fluidized bed gasification process, offers various advantages for biomass gasification as well as the utilization of other solid feedstocks. In order to improve the knowledge of the reactions in fluidized bed gasifier, different types of bed material used in the gasifier were tested in a micro-reactivity test rig. It has been previously observed that during long-term operation, the surface of the bed material used (calcined olivine) undergoes a modification that improves catalytic activity. The main reaction of interest is the water–gas shift reaction. Olivine taken from long-term operation at the 8 MW biomass gasifier at Güssing (Austria), fresh olivine as a reference, and calcite, which is commonly used for enhancing in-bed catalytic tar reduction, were tested using the micro-reactivity test rig. Tests were carried out at temperatures of 800, 850, and 900 °C and space velocities of 40,000 to 50,000 h−1 were applied. CO conversions of up to 61.5% were achieved for calcite. Used olivine showed a similar behavior, representing a large improvement compared to fresh olivine, which had CO conversion rates of less than 20%. [Copyright &y& Elsevier]

Abstract: Gasification of wood pellets at a gasification temperature of 850°C and a fuel power of 90kW was performed in a dual fluidized bed gasifier. Pure steam was used as a gasification agent at a steam-to-fuel ratio of 0.6kgH2O/kgfuel,daf. One focus of the investigation was the influence of the position at which the solid fuel was fed into the gasifier. In one case the fuel was fed directly into the bubbling fluidized bed while in the second case the fuel was fed from the top onto the bubbling bed. With in-bed feeding much lower tar contents and a higher H2 content were observed, while with on-bed feeding the amount of product gas generated was significantly higher. A second focus of this test series was the gas composition inside the reactor. To investigate this, gas measurements were carried out at different height levels in the reactor for both fuel feeding options. It was observed that the gas composition changed drastically along the height of the gasifier. A decrease in the H2 content of about 12vol%db was measured from the lowest to the highest sampling point in the gasifier while the contents of higher hydrocarbons, CH4, C2H4, and C2H6, increased towards the gasifier outlet. [Copyright &y& Elsevier]

Abstract: Within the project ENEREED reeds from the Lake Neusiedl in Austria is examined as energy resource for thermal utilization. The aim of the project is to investigate methods for thermal conversion technologies as well as develop pre-treatment technologies for using reed as cheap, locally available and renewable feedstock. This paper presents the investigations and experimental results of thermal utilization of reed in a 3 MWth commercial district heating plant dedicated for combustion of wood chips. The results of the fuel analysis show that reed is a high quality straw-type biomass with an ash deformation temperature of over 1400°C. Chopped reed were mixed with wood chips in various ratios and fed into the heating plant. The results show that the higher sulphur and chlorine content in reed causes a higher SO2 (25ppm) and HCl (1.6ppm) content in the flue gas. However, with higher ratios of reed in the feedstock no increasing of dioxins or heavy metals could be measured. At the end of the experiment a short run with pure reed was carried out. The experiments show that chopped reed is difficult to feed alone, which would requires a specific feeding system, but it was proven that reed is a suitable feedstock for commercial district heating plants. [Copyright &y& Elsevier]

Abstract: Gasification of biomass and coal is an attractive technology for combined heat and power production, as well as for synthesis processes such as the production of liquid and gaseous biofuels. The allothermal steam blown gasification process yields a high calorific product gas, practically free of nitrogen. Originally designed for wood chips, the system can also handle a large number of alternative fuels. To demonstrate the influence on the system performance of fuels that have a different origin, wood pellets, as the designated feedstock, and hard coal as an example fossil fuel were fed into the DFB gasifier with a fuel blend ratio of 20% coal in terms of energy. A fuel power of 78kW and a steam to fuel ratio of 1.0kg/kgdb were achieved. The system was operated at gasification temperatures between 830 and 870°C. This paper points out the influence of the temperature on the system. [Copyright &y& Elsevier]

Abstract: In the last decade the reduction of CO2 emissions from fossil fuels became a worldwide topic. Co-gasification of coal and wood provides an opportunity to combine the advantages of the well-researched usage of fossil fuels such as coal with CO2-neutral biomass. Gasification itself is a technology with many advantages. The producer gas can be used in many ways; for electric power generation in a gas engine or gas turbine, for Fischer–Tropsch synthesis of liquid fuels and also for production of gaseous products such as synthetic natural gas (bio SNG). Moreover, the use of the producer gas in fuel cells is under investigation. The mixture of coal and wood leads to the opportunity to choose the gas composition as best befits the desired process. Within this study the focus of investigation was of gasification of coal and wood in various ratios and the resulting changes in producer gas composition. Co-gasification of coal and wood leads to linear producer gas composition changes with linear changing load ratios (coal/wood). Hydrogen concentrations rise with increasing coal ratio, while CO concentrations decrease. Due to the lower sulfur and nitrogen content of wood, levels of the impurities NH3 and H2S in the producer gas fall with decreasing coal ratio. It is also shown that the majority of sulfur is released in the gasification zone and, therefore, no further cleaning of the flue gas is necessary. All mixture ratios, from 100 energy% to 0 energy% coal, performed well in the 100kW dual fluidized bed gasifier. Although the gasifier was originally designed for wood, an addition of coal as fuel in industrial sized plants based on the same technology should pose no problems. [Copyright &y& Elsevier]

Abstract: The steam gasification of solid biomass by means of the absorption enhanced reforming process (AER process) yields a high quality product gas with increased hydrogen content. The product gas can be used for a wide range of applications which covers the conventional combined heat and power production as well as the operation of fuel cells, the conversion into liquid fuels or the generation of synthetic natural gas and hydrogen. On the basis of a dual fluidized bed system, steam gasification of biomass is coupled with in situ CO2 absorption to enhance the formation of hydrogen. The reactive bed material (limestone) used in the dual fluidized bed system realizes the continuous CO2 removal by cyclic carbonation of CaO and calcination of CaCO3. Biomass gasification with in situ CO2 absorption has been substantially proven in pilot plant scale of 100 kW fuel input. The present paper outlines the basic principles of steam gasification combined with the AER process the investigations in reactive bed materials, and concentrates further on the first time application of the AER process on industrial scale. The first time application has been carried out within an experimental campaign at a combined heat and power plant of 8 MW fuel input. The results are outlined with regard to the process conditions and achieved product gas composition. Furthermore, the results are compared with standard steam gasification of biomass as well as with application of absorption enhanced reforming process at pilot plant scale. [Copyright &y& Elsevier]

Abstract: Catalytic steam reforming of a model biogas (CH4/CO2 =60/40) is investigated to produce H2-rich synthesis gas. Gas engines benefit from synthesis gas fuel in terms of higher efficiency and lower NO x production when compared to raw biogas or CH4. The process is realized in a fixed bed reactor with a Ni-based catalyst on CaO/Al2O3 support. To optimize the performance, the reactor temperature and the amount of excess steam are varied. The experimental results are compared to the theoretical values from thermodynamic calculation and the main trends of CH4 conversion and H2 yield are analyzed and verified. Finally, optimal reactor temperature is pointed out and a range of potential steam to methane ratios is presented. The experimental results will be applied to design a steam reformer at an existing anaerobic biomass fermentation plant in Strem, Austria. [Copyright &y& Elsevier]

Abstract: Gasification of biomass is an attractive technology for combined heat and power production. Although a lot of research and development work has been carried out during the past decade the commercial breakthrough for this technology is still to come. One problem that has not been completely solved so far is the tar content in the product gas, which can cause plugging in the colder parts of the plant. Among the possible gas cleaning methods, catalytic hot gas cleaning is rather promising because of the complete destruction of the tars instead of creating a waste stream which is difficult to dispose. Different catalysts were measured in laboratory scale reactors fed by synthetic gas mixtures and tar model compounds. Commercial steam-reforming catalysts for heavy hydrocarbons (particularly naphthas) proved best as tar decomposing catalysts. Based on these results 3 nickel-based monolith type of catalyst were produced and afterwards tested in a laboratory scale reactor fed by slip streams taken from the 8 MW dual fluidized bed steam gasifier plant in Güssing, Austria. Almost complete tar and considerable ammonia decomposition could be achieved over this catalyst at temperatures above 850 °C and space velocities of about 1100 h−1. [Copyright &y& Elsevier]

Three different waste streams from olive oil production from Montenegro are utilized energetically by hydrothermal carbonization (HTC – hydrochar) and pyrolysis (biochar). Pyrolysis experiments of three-phase olive mill solid waste (3POMSW) were conducted for different pyrolysis temperatures of 450, 550, and 700 °C and a residence of 60 min for each experiment. HTC experiments for two-phase olive mill waste (2POMW) and a mixture of olive mill wastewater (3POMWW) and 3POMSW were carried out at 180, 200, and 220 °C, autogenous pressure of (1, 1.6, and 2.3 MPa) for 60 min. Increasing reaction temperature led throughout all experiments to a lower carbon recovery. Furthermore, all hydrochar and biochar samples had energy densification of more than one, indicating a higher mass-energy density than the initial feedstock. The highest energy yields were achieved for the 3POMW, with 46.48 % in hydrochar treated at 180 °C and 44.09 % in biochar treated at 450 °C. Concerning the hydrochar from 2POMW, the highest energy and mass yields of 62.53 % and 49.65 %, respectively obtained at 180 °C. Summarizing, the energy potential of Montenegro's olive mill waste (OMW) was estimated at 43.69 PJ, which roughly could cover the whole energy demand of the olive oil industry in Montenegro. • Biochar and hydrocar energy potential derived from olive mills waste was evaluated. • Hydrocar derived at 200 °C for 60 min are suitable for substituting peat. • Biochar derived at 450 °C and above are suitable for substituting coal. • Pyrolysis and HTC are feasible methods to provide bioenergy olive mill waste. [ABSTRACT FROM AUTHOR]

The thermal cracking of cotton stalks (CS) through pyrolysis was undertaken using a laboratory scale batch pyrolysis reactor. The distribution of pyrolysis products were studied dependent on the final pyrolysis temperature which ranged from 300 to 800 °C by 100K intervals. The maximum biochar yield of 46.5% was obtained at 400 °C. As the pyrolysis process temperature increased, the solid char product yield decreased. The largest higher heating value (25.845 MJ kg−1) was obtained at 600 °C. All biochar samples produced between 500 and 700 °C had an energy densification ratio of 1.41, indicating a higher mass-energy density than the initial feedstock. A larger share of syngas and bio-oil were produced at higher temperatures, as estimated. Preferential selection of a char based on the energy yield would lead to a selection of the 400 °C product, while selection based on the energy densification ratio would be for a product obtained between 500 and 700 °C. An energy simulation was conducted which determined that the process is self-sustaining at and above 400 °C. Furthermore, the global energy potential was determined from CS pyrolysis, which was estimated at 380 PJ yr−1 could contribute to roughly 0.1% of the actual global total primary energy supply of 576 EJ yr−1. • Biochar yields decrease and syngas yields increase with temperature increase from 300 to 800 °C. • The largest higher heating value (25.8 MJ kg−1) of biochar was obtained at 600 °C. • Process simulation showed that the pyrolysis process is energetically self-sustaining at 400 °C and above. • A temperature of 400 °C is optimal for deriving energy from the biochar. • Global energy potential from pyrolysis CS could contribute to 0.1% of the actual global total energy supply. [ABSTRACT FROM AUTHOR]

Cotton stalks (CS) are low-value agricultural residues which are usually burned in the fields, causing a major environmental problem. Bioenergy from agricultural residues has a two-fold advantage over other renewable energy sources: it allows for energy production as well as waste material recovery. In this work, the application of hydrothermal carbonization (HTC) to produce hydrochar from CS was investigated. The HTC experiments were carried out in a laboratory HTC reactor with an optical cell. The effect of reaction time was examined by altering it from 5 to 360 min at a constant temperature of 200 °C. It has been proven that hydrochar yields decrease and the heating value increases with an increase in reaction time from 5 to 360 min at 200 °C. The maximum higher heating value (20.41 MJ/kg) of hydrochar was obtained at 200 °C for 360 min. The highest degree of carbonization'of CS observed at 200 °C and a reaction time of 45 min and above. Furthermore, the experimental results were verified by mass and energy balances calculated with the simulation software IPSEpro. Based on these findings, a process sheet for an industrial application is suggested and calculated. • Hydrochar from cotton stalks was produced in a laboratory reactor with an optical cell. • The effects of reaction time on the energy and hydrochar yields were determined. • Cotton stalks HTC chars at 200 °C for 45 min and above are suitable for substituting peat. • Based on HTC simulation a process sheet for an industrial application was calculated. [ABSTRACT FROM AUTHOR]

The market offers a broad range of different combustion appliances dedicated to residential heating with biomass. The effect of fuel properties on the formation of slag and emissions varies and the technology influences the impact to a certain extent. The applicability of biomass fuels is not only determined by operational settings but also by the design of boiler components as grate area and combustion chamber. Aspects as the fuel load on the grate, residence time, geometry of grate and combustion chamber design, as well as feeding and de-ashing influence the extent of slag formation and emission release. The determination of characteristic numbers by means of constructional measures allows a systematic comparison and - in a further step - an assessment/categorization of combustion technologies. After conducting a boiler survey relevant parameters regarding grate, combustion chamber, feeding, and ash removal were gathered. Characteristic numbers were specified in order to compare technological aspects. The results of this study allow the investigation of the influence of the combustion technology on the performance. They will assist the systematic and targeted design of small-scale boilers and the optimization of combustion appliances in future, especially when it comes to fuel-flexibility. Image 1 • Technology indexes developed for coal combustion were applied for biomass boilers. • Data of 76 small-scale appliances were gathered to provide typical ranges of design. • Grate load, design of feeding system and ash removal strategy depend on approved fuel. • Results allow an investigation of technological influence on combustion process. • Findings provide a basis for a systematic and targeted design of small-scale boilers. [ABSTRACT FROM AUTHOR]

The additives released from plastic waste during co-combustion significantly influence indoor air quality. It was found that the unauthorised burning of plastics in households increased the additive concentrations in the indoor air of living spaces by an average of 5 μg/m3. This effect was observed from the difference between background concentrations (indoor quality during combustion of wood) and concentrations during the co-combustion of plastics. The one-way ANOVA analysis shows that indoor air quality is affected not only by the migration of pollutants from the boiler room within the indoor environment (infiltration) but also by air exchange with emissions and outdoor air. The highest concentrations of released additives in the boiler room were found for polystyrene > polypropylene > polyethylene terephthalate > polyethylene (low-density polyethylene and high-density polyethylene). Phthalates from polystyrene (21.16 ± 3.15 μg/m3) were released at the highest concentration, while phthalates from other plastics reached approximately half of this value. During the combustion of high-density polyethylene with softwood, chemical compounds from the residuals of content in plastic packaging were identified in the air (6.26 ± 0.31 μg/m3). Almost all these compounds show significant adverse health effects (irritation of the skin and the respiratory system), and some are carcinogenic. [Display omitted] • Household burning of plastics affects the occurrence of additives in indoor air. • Additives include plasticisers, UV absorbers, antioxidants, and flame retardants. • During the combustion of plastics, phthalates form 59–84 % of all additives. • The combustion of HDPE packaging material releases hazardous chemicals. • Almost all identified additives have an adverse effect on human health. [ABSTRACT FROM AUTHOR]

This paper shows how chemical sludge (CS) generated during wastewater treatment at a paperboard mill can be quickly dried at low-temperature and employed in bark-fired boilers to reduce slagging and corrosion problems. By using a cyclone-dryer operated at an inlet-air velocity of 110 m/s and a temperature of 90 °C, the dry-matter content of CS was increased from approximately 19 to 82%. The residence time of CS inside the cyclone was approximately 2 s when using the inlet-air velocity mentioned above. Disaggregation of the feedstock caused by collisions with the cyclone wall and between particles played a crucial role in enhancing the efficiency of heat and mass transfer. Three co-pelletized mixtures of Scots pine bark (SPB) and dried-CS were combusted in a 40 kW fixed-bed burner. Flue gas analysis was performed with a gas analyser. Coarse and fine ash were analysed by SEM-EDS and XRD. NO x and SO 2 emissions increased with increasing amount of CS in the mixtures. Mono-combustion of SPB resulted in a large quantity of slag (i.e., molten ash) with a high degree of sintering (i.e., hardness of the slag), and ash deposits formed on heat transfer surfaces were rich in K 2 SO 4 and KCl. Mixtures of SPB and CS were less prone to slagging, and the amount of alkali chloride in the deposits was reduced in favour of alkali sulphate formation. Unlabelled Image • Chemical sludge was dried in a cyclone dryer operated at inlet-air temperatures of ~60–90 °C and velocities of ~60–110 m/s • The dry matter content of the sludge increased from 19 to 82% when the dryer was operated at 90 °C and ~110 m/s • Co-pelletized mixtures of Scots pine bark and dried chemical sludge were combusted in a 40 kW fixed-bed burner • NO x and SO 2 emissions increased with increasing amount of chemical sludge in the mixtures • All mixtures were less prone to slagging, and KCl in ash-deposits was reduced in favour of K 3 Na(SO 4) 2 formation [ABSTRACT FROM AUTHOR]

Abstract Thermal conversion of ligno-cellulosic agricultural waste inside a pyrolysis reactor and soil-storage of pyrolysis char is discussed as a low-tech negative emission technology. Cotton stalks are a typical agricultural residue with little economic value and there is no direct competition to food or feed provision. Currently, the stalks are often burnt on the fields. The investigated rotary kiln pyrolysis process has already been successfully applied at industrial scale before. In the investigated scenario, the pyrolysis char is returned to the soil for long-term carbon storage while the volatile pyrolysis products are used energetically. The steady-state process simulation environment IPSEpro was used to assess a virtual conversion plant. The mass- and energy flows are determined based on earlier measurements at a 500 kg/h test plant. The results show that 52.8% of the carbon contained in the biomass accumulate in the biochar, whereas 38% of the input energy can be exported as heat energy at temperature levels suitable for electricity generation or industrial heat supply. The pyrolysis char shows a low molecular O/C ratio of 0.07 and an H/C ratio of 0.26. The expected half-lives of biochar in soil are in the order of 1000 years for O/C ratios below 0.2. This makes the presented approach an interesting low-tech negative emission option. The predicted net negative emissions through stored carbon amount to 2.42 t CO 2 per hectare and year. The overall CO 2 emission avoidance effect can be increased if fossil fuel is substituted by the energy exported from the pyrolysis process. Highlights • Low-value agricultural waste materials such as cotton stalks can serve as carbon precursor for negative emission solutions. • For slow pyrolysis of dry lingno-cellulosic material, roughly 53% of the carbon are found in the biochar product. • About 40% of the lower heating value-based energy in the feed biomass can be exported as heat. • The direct negative emissions through soil-storage of char from cotton stalks amount to 2.42 t CO 2 per hectare and year. [ABSTRACT FROM AUTHOR]

Boron (B) fertilizers are essential for global crop production. Sustainable B use demands a higher efficiency of B fertilizers through controlled B release and an enhanced B recycling from secondary sources, e.g. B-impregnated cellulose fiber insulation (CFI) waste. In this study, thermochemical treatments based on combustion and pyrolysis were investigated for processing CFI waste into a slow-release B fertilizer. Hot-water extractions of obtained materials confirmed that slow-release properties were achieved, and material characterization with XRD, FTIR and 11B-NMR showed that these were largely the result of formation of sparingly soluble Ca–B phases. A seedling toxicity test with fodder rape demonstrated the benefit of this slow-release B in comparison with conventional soluble B to circumvent toxicity, suggesting potential for B application via seed coatings. Finally, a fertilization trial with fodder rape and poppy seed showed that most slow-release B compounds were equally effective as soluble B at recommended B doses, while slow-release B can still benefit from reduced B leaching losses. [Display omitted] • Thermochemical processing of B-rich cellulose fiber insulation (CFI) was tested. • Obtained combustion and pyrolysis products had slow-release B characteristics. • Slow-release B was largely the result of formation of sparingly-soluble Ca–B phases. • B toxicity to plants could be avoided using treated CFI instead of soluble B. • In a plant fertilization trial, treated CFI was equally effective as soluble B. [ABSTRACT FROM AUTHOR]

The construction and testing of a cold flow model carried out aimed to study fluid dynamic behaviour of a dual fluidized bed pyrolysis. The modelled plant is able to convert various plastic wastes into high caloric fuels by pyrolysis in a bubbling fluidized bed section. A second turbulent fluidized bed provides the heating energy needed for the pyrolysis process. The cold-flow model had been designed and built according to Glicksman's criteria and is geometrically miniaturized on a scale of 1:3 in relation to the hot facility. These principles allow likewise the transformation of the results from the model to the pilot plant conditions. Pressure along the unit, the global solids flux rate and the amount of bed material loss through the product outlet were measured for operation under different values of pyrolysis fluidization rate ( φ FP ) and combustion fluidization rate ( φ FC ). The fluidization rate is calculated between 0 for minimum fluidization and 1 for sedimentation velocity. It was found, that at low fluidization rates the bed density is much higher at the lower part of the combustion riser than at the upper part. With increasing φ FC the pressure in the whole system rises and the distribution of the bed material in the combustion gets more even. φ FC is also highly correlating with the global solids flux and rises with it until U se is reached and pneumatic transport appears. Increase of the solids flux increased the bed expansion in the siphons and the pyrolyser and leads to a higher loss of material. The raise of φ FC has no major influence on the combustions pressure profile. Small changes in the combustions pressure profile result from the amount of bed material accumulated in the pyrolysis reactor not available for the global circulation. This also influences the global solids flux. With increasing φ FP the amount of bed material and the height of the bubbling bed decrease. The amount of bed material loss raises drastically with increasing φ FP . However, the loss can be used to somehow classify the loss on particle diameter, Thus, the caloric value of the product gas can be adjusted by enriching soot while the lager particles are kept within the system. [ABSTRACT FROM AUTHOR]

• Bigger samples tend to auto-ignite at lower temperatures. • Beech wood ignites at lower temperatures than spruce wood. • Influence of hemicelluloses on auto-ignition. • Isothermal phases during heating before final combustion. The influence of size and temperature on the heating and auto-ignition of beech (fagus sylvatica) and spruce (picea abies) wood cubes were studied. Experiments were conducted in a furnace at five isothermal temperatures (240 °C, 270 °C, 300 °C, 330 °C and 360 °C) with four cube sizes (5 mm, 10 mm, 15 mm and 20 mm). Temperatures inside the cubes were recorded with thermocouples (TC). Arising temperatures from the experiments were compared to mass-losses and exothermic reactions measured with simultaneous thermal analysis (STA). While heating up isothermal phases at approx. 360 °C can be seen in the temperature curves due to ongoing pyrolysis. After pyrolysis, a combination of internal heating and heterogenous oxidation reactions on the surface lead to ignition and combustion. Differences in chemical composition between beech and spruce are the cause for exothermic reactions at lower temperatures. Bigger samples tend to ignite at lower temperatures due to lower surface to volume ratio and a larger reactive surface. [ABSTRACT FROM AUTHOR]

The paper aims to find a way of simply identifying the addition of unauthorised waste (plastics) in residential boilers burning wood as the main fuel. The burning of plastics leaves a trace in char deposits, which are otherwise made up mostly of lignin breakdown products. Identification of combusted plastics in char deposits is made possible by determining unique organic compounds formed during the pyrolysis phase of combustion by pyrolysis gas chromatography. At temperatures above 800 °C, the amount of charring product from the incineration of PET is 19.5 wt%, while for PP, it is 5 wt%, and LDPE with HDPE 2.1 wt%. Combustion of polypropylene with wood has been verified by the presence of the compounds 2,4-dimethyl-1-heptene, 2-methyl-1-pentene, and 2,4,6-trimethyl-1-nonene. The thermal degradation of PE has been demonstrated by the presence of triplets of alkanes, alkenes, and alkadienes. Combustion of PET in domestic waste can be demonstrated by the presence of benzoic acid and its esters, benzoate compounds, and terephthalic acid. In summarising, sampling char in boilers and analysing samples for markers of plastics incineration could be used as a method for identification of unauthorised waste combustion by authorities. [ABSTRACT FROM AUTHOR]

Cotton stalks (CSs) are an abundant, renewable lignocellulose residue, which is usually burnt in the field to prevent propagation of vegetal diseases, causing economic losses and environmental concerns. The production of biogas has been considered as an alternative. This work aimed to improve the biogas production from CS by steam or organosolv plus supercritical carbon dioxide (scCO 2) pre-treatment. All samples were pre-treated in a 500 mL autoclave for 140 min at 180 °C and fermented in 1 L eudiometer batch digesters for 42 days at 37.5 °C. The biogas and methane yields achieved from the untreated CS were 250 and 137 norm litres per kg of volatile solid (L N kg−1 VS), respectively. Pre-treatment of the CS samples with steam or the organosolv plus scCO 2 process increased the methane yield by 20% compared to the untreated samples. The highest methane yield of 177 L N kg−1 VS was achieved by organosolv plus scCO 2 pre-treatment at 100 bar and 180 °C for 140 min. Moreover, pre-treatment of the CS led to a significant reduction in the optimal digestion time from 30 days to 20 days for biogas production for the untreated CS. • Cotton stalks successfully pre-treated for anaerobic digestion. • Organosolv followed by super-critical CO 2 pre-treatment increased methane yield. • Anaerobic digestion of pre-treated cotton stalks led to high quality biogas. • Significantly reduced retention time in the fermenter due to pre-treatment. [ABSTRACT FROM AUTHOR]