Solid Recycling Research Articles

Biotic and abiotic factors acting on community assembly in parallel anaerobic digestion systems from a brewery wastewater treatment plant

ABSTRACT Anaerobic digestion is a complex microbial process that mediates the transformation of organic waste into biogas. The performance and stability of anaerobic digesters relies on the structure and function of the microbial community. In this study, we asked whether the deterministic effect of wastewater composition outweighs the effect of reactor configuration on the structure and dynamics of anaerobic digester archaeal and bacterial communities. Biotic and abiotic factors acting on microbial community assembly in two parallel anaerobic digestion systems, an upflow anaerobic sludge blanket digestor (UASB) and a closed digester tank with a solid recycling system (CDSR), from a brewery WWTP were analysed utilizing 16S rDNA and mcrA amplicon sequencing and genome-centric metagenomics. This study confirmed the deterministic effect of the wastewater composition on bacterial community structure, while the archaeal community composition resulted better explained by organic loading rate (ORL) and volatile free acids (VFA). According to the functions assigned to the differentially abundant metagenome-assembled genomes (MAGs) between reactors, CDSR was enriched in genes related to methanol and methylamines methanogenesis, protein degradation, and sulphate and alcohol utilization. Conversely, the UASB reactor was enriched in genes associated with carbohydrate and lipid degradation, as well as amino acid, fatty acid, and propionate fermentation. By comparing interactions derived from the co-occurrence network with predicted metabolic interactions of the prokaryotic communities in both anaerobic digesters, we conclude that the overall community structure is mainly determined by habitat filtering.

Morphological analysis of mercury in solid wastes from natural gas processing plants: optimization of a temperature-programmed decomposition and desorption method.

Determination of mercury species over solid waste from natural gas processing plants is a prerequisite for solid waste decontamination and mercury recycling. The temperature-programmed decomposition and desorption method (TPDD) is a promising technique to determine the mercury species over solid waste. Mercury species over solid wastes with complex components and similar desorption temperature, however, cannot always be determined using only the TPDD method. In the present study, the EPA 3200 method was applied to optimize the TPDD process for speciation of the mercury compound over solid wastes collected from a natural gas processing plant, including four spent adsorbents and three sludges. The mercury species with similar desorption temperatures over solid wastes were completely separated by the EPA 3200 method optimized TPDD process. The mercury species over spent adsorbents and sludges could be determined based on the fingerprints of the mercury compounds. The mercury compounds over spent adsorbents were specified to be Hg0 and/or M-Hg amalgam, HgS(black) and HgO(red), of which HgS(black) was the primary mercury compound. However, the mercury species over sludge were analyzed to be Hg0 and/or M-Hg amalgam, HgCl2(minor), HgS(black), HgO(yellow) and HgS(red). The mercury recovery rates of solid wastes ranged from 73% to 120%. With the above results, it was considered that the EPA 3200 method optimized TPDD process was a promising method to specify and semi-quantify the mercury compounds in solid waste.

COVID-19, waste production and municipal recycling programs: Insights from Chile to the global south

The amount and characterization of municipal and industrial waste generated in numerous cities worldwide have changed dramatically in recent years due to the COVID-19 pandemic. Consequently, assessing the impact of COVID-19-related policies is important to provide decision-makers with adequate knowledge to respond effectively to future events and create successful policies that respond to specific contexts. This study focuses on Chile, Latin America's second-largest municipal and industrial solid waste producer, with tight quarantine procedures placed to prevent the virus from spreading, and a series of monetary incentives implemented to minimize the economic and social impact of the quarantines. The time series of municipal solid waste (MSW) and recycling in the metropolitan region show a decrease in the amount collected during the initial months of lockdown and a subsequent increase during monetary incentive implementation. The country recovered and exceeded pre-pandemic MSW generation and recycling levels. Furthermore, the lockdown and the withdrawal of retirement funds (WRF) had a varied impact on each municipality in the region. However, WRF had a larger direct impact than a lockdown, indicating that purchasing power has a greater impact than mobility in waste generation and recycling, at least in this region of Chile.

Life-Cycle Assessment of Municipal Solid Waste Incineration Fly Ash Recycling as a Feedstock for Brick Manufacturing

The recovery of municipal solid waste incineration (MSWI) fly ash is currently considered to be the most viable solution for its management. However, in developing resource recovery technologies, it is crucial to consider the overall environmental impact. This study employed a life-cycle assessment (LCA) to compare environmentally friendly red bricks partially utilizing MSWI fly ash as a raw material with conventional red bricks. The results demonstrate that the use of phosphoric acid during the resource recovery process imposes the most significant environmental burden, followed by electricity consumption. To address this issue, in this study, we simulated the replacement of phosphoric acid with phosphoric acid monohydrate recovered from discarded fire extinguishers, resulting in the production of second-generation environmentally friendly red bricks. The analysis revealed that the environmentally friendly red bricks exhibited a mere 5.52% increase in total environmental impact compared with traditional red bricks. Moreover, by stabilizing heavy metals using recovered phosphoric acid monohydrate, the second-generation environmentally friendly red bricks achieved an 8.75% reduction in total environmental impact relative to traditional red bricks. These findings highlight the environmental benefits of fly ash reuse in red brick production, and the incorporation of other industrial waste or byproducts could further enhance its efficacy. The application of the LCA facilitated the identification of key areas for improvement and enabled precise evaluation of the environmental benefits associated with waste reuse.

Thermal Hydrolysis Pretreatment Effects on Endocrine Disrupting Compounds and Microbial Communities in Wastewater Sludge from Anaerobic Digestion

Concerns regarding endocrine disrupting compounds (EDCs) in wastewater treatment plant effluents have led to the need to better understand their fate during various treatment processes. The thermal hydrolysis process (THP) is a growing technology; this article aims to better understand the impacts of THP on EDCs. Serum bottles were used to understand how the THP of anaerobically digested wastewater influences concentrations of phthalic acid esters (PAEs) and antimicrobials. The succession of DNA-based microbial community was followed to assess conditions of contaminant biotransformation. Sludge samples were collected at different locations, placed in 250 mL serum bottles, and inoculated with samples collected from the anaerobic digestion solid recycle line to compare the influence of the THP pretreatment. Bottles were covered, kept at 37°C, and agitated for 22 days, with periodic destructive sampling for the chemical analysis of antimicrobials, PAEs, and transformation products, as well as the microbial community structure. Results demonstrated an increase in the concentrations of triclosan (TCS), triclocarban (TCC), and their transformation products with and without THP pretreatment. 2,4-Dichlorophenol increased at a significantly higher rate in pretreated sludge, while the TCC concentrations increased significantly faster in untreated sludge. Pretreatment did not significantly influence the formation rates of TCS and methyl triclosan. Pretreatment impacts on phthalate concentrations varied. Di(2-ethylhexyl) phthalate decreased and diisononyl phthalate concentrations were unchanged. Benzyl butyl phthalate increased in sludge that had undergone pretreatment and decreased in sludge without. PAE metabolites generally increased during the course of the experiments. Results demonstrate the potential for complex transformation processes and indicate the ability of THP to influence concentrations of certain compounds of concern. Analysis of the microbial community structure did not demonstrate any statistically significant difference between sludge with pretreatment and sludge without over the course of the experiment. These results indicate that changes in chemical concentrations could be due to other physicochemical mechanisms not examined.

Investigation of Attitudes towards Solid Waste and Recycling from a Social Perspective

Investigation of Attitudes towards Solid Waste and Recycling from a Social Perspective

Environmental Analysis, Monitoring, and Process Control Strategy for Reduction of Greenhouse Gaseous Emissions in Thermochemical Reactions

This review paper illustrates the recommended monitoring technologies for the detection of various greenhouse gaseous emissions for solid waste thermochemical reactions, including incineration, pyrolysis, and gasification. The illustrated gas analyzers are based on the absorption principle, which continuously measures the physicochemical properties of gaseous mixtures, including oxygen, carbon dioxide, carbon monoxide, hydrogen, and methane, during thermochemical reactions. This paper illustrates the recommended gas analyzers and process control tools for different thermochemical reactions and aims to recommend equipment to increase the sensitivity, linearity, and dynamics of various thermochemical reactions. The equipment achieves new levels of on-location, real-time analytical capability using FTIR analysis. The environmental assessment study includes inventory analysis, impact analysis, and sensitivity analysis to compare the mentioned solid waste chemical recycling methods in terms of greenhouse gaseous emissions, thermal efficiency, electrical efficiency, and sensitivity analysis. The environmental impact assessment compares each technology in terms of greenhouse gaseous emissions, including CO2, NOx, NH3, N2O, CO, CH4, heat, and electricity generation. The conducted environmental assessment compares the mentioned technologies through 15 different emission-related impact categories, including climate change impact, ecosystem quality, and resource depletion. The continuously monitored process streams assure the online monitoring of gaseous products of thermochemical processes that enhance the quality of the end products and reduce undesired products, such as tar and char. This state-of-the-art monitoring and process control framework provides recommended analytical equipment and monitoring tools for different thermochemical reactions to optimize process parameters and reduce greenhouse gaseous emissions and undesired products.

Study on the mechanism of removing fluoride from wastewater by oxalic acid modified aluminum ash-carbon slag-carbon black doped composite

In this study, SAA@CS-CB(aluminum-ash carbide slag carbon black doped composite) was prepared by sintering method and modified by impregnation with oxalic acid to obtain SAA@CS-CBoa. Fluoride adsorption experiments were carried out using this composite as adsorbent. With increasing pH values, the adsorption amount of fluoride decreases in the range of 2–11. The pseudo second order equation and Langmuir model were fit to the experimental data, and the adsorption of fluoride by SAA@CS-CBoa exhibited spontaneous and endothermic characteristics. When PO43-, CO32–, SO42-, Cl-, NO3–, Br- and HCO3– anions were individually or combined in solution, the adsorbents exhibited higher fluoride selectivity and sensitivity, while PO43-and CO32– weakened the adsorption of fluoride in solution in the same way regardless of the presence of the other 5 anions. The results of SEM, EDS, XRD and FTIR characterizations showed that the mechanism of fluoride adsorption and removal by SAA@CS-CBoa included the combined effects of electrostatic attraction, surface coordination precipitation and ion exchange. SAA@CS-CBoa is an effective composite material for water adsorption of fluoride, and still has an excellent performance of cyclic regeneration after 10 times adsorption desorption. This study provides a new approach for the utilization of fluoride removal resources for industrial solid waste resource recycling.

Reuse of Pretreated Red Mud and Phosphogypsum as Supplementary Cementitious Material

The combination of red mud (RM) and phosphogypsum (PG) can exert the alkalinity of RM and the acidity of PG as a calcium source to promote the gel hardening of composite cementitious material, which effectively improves the reutilization efficiency of RM and. In this study, the effects of the ratio and content of pretreated RM and PG on the non-evaporated water, porosity, hydration products, mechanical properties, pore size distribution, and microstructure of composite cementitious materials were investigated. The results show that, with the incorporation of PG, RM, PG, and RM, the non-evaporable water content, reaction degree, compressive strength, and flexural strength show a downward trend after rising first, and their values reach the maximum with 10% PG and 10% RM, which are higher than a pure cement system, while 70% PG, 70% RM, 70% RM + 10% PG, and 70% PG + 10% RM have the reverse effect. The results of hydration products, pore size distributions, and microstructure indicate that adding an appropriate dosage of RM and PG can efficaciously improve the compactness of cement systems. Nevertheless, the research results can contribute to using the combination of PG and RM to manufacture sustainable cementitious materials with good performance, and achieve the purpose of environmental protection and industrial solid waste resource recycling.

Research on improving the administrative service efficiency of biomass, waste and solid biofuel recycling

ABSTRACT Many countries are using effective strategies to recycle biomass, waste, and solid biofuels as an important means to achieve carbon emission peaking and carbon emission neutrality. China needs to continuously improve its recycling system and promote the development of waste material recycling systems. To provide guidance for the upgrading of ecological network public opinion governance and recycling government service practice, based on the internal support and external pressure atmosphere of ecological environmental administration, this paper uses fuzzy set qualitative comparative analysis to analyze the four influencing factors of government resources, network environment, ecological environment, and public opinion environment so as to explore the path of recycling administrative service upgrades under the configuration perspective, the configuration analysis, and the upgrade path evolution of 30 provincial ecological administrations. It is found that the intersection of the influencing factors constitutes ‘netizen-motivated’, ‘virtual reality – driven’, ‘internal and external – regulated’, and ‘ecologically led’ paths. The four effective and mutually responsive configuration paths are applied to regional ecological and environmental administration service capacities from weak to strong.

Preparation of High Bio-Content Polyurethane Coatings from Co-Liquefaction of Cellulosic Biomass and Starch for Controlled Release Fertilizers

To manufacture high bio-content degradable polyurethane-coated fertilizer, the co-liquefaction of corn straw and starch was carried out to convert more biomass into bio-polyol so as to substitute petroleum-based polyol. The effect of the corn straw to starch ratio on liquefaction behavior was mainly investigated by monitoring acid value, hydroxyl value, and liquefaction rate. Both chemical structures and properties of bio-polyols and their coatings were characterized by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), etc. The results indicated that adding a certain amount of starch to corn straw for co-liquefaction could contribute to a higher hydroxyl content of bio-polyol than that from sole biomass. Compared to molecular weight, the hydroxyl value was a more significant index to ensure coating quality. The incorporation of starch segments to bio-polyol led to good thermal stability, limited residual small molecules, and high crosslinking density of the coating. The controlled-release ability of coated urea prepared by co-liquefied bio-polyol was better than that of corn-straw-based bio-polyol, and the optimal ratio of corn straw to starch was 3:1. Overall, this study provides a new route to fabricate corn straw as a cost-effective and degradable coating with good controlled-release properties, which benefits solid biomass recycling.

Has enough been done in plastics recycling?

The need to segregate urban solid waste is a fact, something that has been achieved in a certain way thanks to the dissemination and awareness that has been promoted through environmental education, taught in educational institutions at all levels and the transmission of information through social networks. The follow work addresses the problem of the deficiencies present in the environmental management of plastic waste, due to the lack of classification and separation of the same. It is no longer just a matter of separating the urban waste produced, with the aim of reducing, reusing or recycling it, since, even in the best case scenario of correctly separating plastics from all other solid waste, reuse or Recycling is practically not possible if these are mixed together. This research hypothesizes that a large majority of people do not know how to distinguish the different types of plastic with which the products and containers that are used on a daily basis are manufactured. The objective of this research is to propose strategies to solve the problem raised based on the results obtained.

Precipitation in AA6063 produced from swarf using additive friction stir deposition

• AA6063 via additive friction stir deposition (AFSD) refines the harmful Fe containing particles present in the swarf and exhibits a relatively refined and equiaxed grain structure. • A precipitation gradient is formed during AFSD but post heat treatment readily produces a uniform structure. • Heat-treated AFSD AA6063 shows a wrought-like property. Additive friction stir deposition (AFSD) is an emerging additive manufacturing technology with the unique capability to create large-scale, free-form depositions without melting. It has the added benefit of accepting input material that is readily formed from swarf. The present work addresses questions that have arisen over the impact of the process on the precipitation in 6063 aluminium alloys (AA6063). The mechanical properties and microstructure throughout the deposit was assessed and characterized in T4, T5 and T6 conditions using a combination of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). In the as-deposited condition, the degree of precipitation was highly heterogeneous across the different printed layers, resulting in a significant hardness gradient from the bottom to the top of the deposit. Such gradients in hardness and precipitation could be eliminated through the use of a T6 heat treatment. Additionally, the EBSD result shows that the deposited AA6063 exhibited a relatively refined and equiaxed grain structure, which evolved via continuous dynamic recrystallization during deposition. These results emulate those observed for 6xxx-series alloy deposits formed from primary material. This work demonstrates the capacity of AFSD as a viable method of solid state Al recycling, creating depositions with wrought-like properties when an adequate post-deposition heat treatment is conducted.

Prediction and minimization of NOx emission in a circulating fluidized bed combustor: Improvement of bed quality by optimizing cyclone performance and coal particle size

• Improvement of cyclone performance contributes to reducing the NO x emission. • Reducing coal particle size can decrease the NO x emission. • NO x emission may be further reduced by reducing the height of the coal inlet. • Effects of cyclone efficiency and coal size on combustion efficiency are discussed. • A comprehensive CFB mathematical model is applied to further analyze the mechanism. The NO x emission of circulating fluidized bed (CFB) boilers can be evidently reduced via optimization of the cyclone performance and the coal particle size, which has been proved in industrial practices, while there are few reasonable interpretations for these phenomena so far. In this paper, a comprehensive 1-dimensional/1.5-dimensional CFB mathematical model was applied to investigate the effect of these two important factors on NO x emission. Simulation results on two commercial CFB boilers indicate that increasing the cyclone efficiency and reducing the coal particle size can significantly decrease the average size of bed materials and increase the solid suspension density in the freeboard zone; namely, the bed quality is improved. The local gas–solid flow behaviors inside the CFB furnace will be accordingly changed, such as the increasing volume fraction of bubble phase in dense bed, shortening of secondary air penetration depth, enrichment of particles in the downward-flow annulus or clusters, etc. Consequently, the reducing atmosphere will be formed or enhanced in local areas, leading to the effective inhibition of NO x formation. Meanwhile, the increase in the bed inventory of fine char particles also facilitates the reduction of NO x . Moreover, if appropriately reducing the height of the coal inlet or feeding fine coal particles from the solid recycle system, the NO x emission may be further reduced due to the adjustment of the volatiles release pattern. In addition, the reduction of coal particle size can contribute to the increase in fuel combustion efficiency, while the unburned carbon content in fly/bottom ash may increase or decrease with the improvement of cyclone efficiency. This study further analyzes the influence of gas–solid flow characteristics on the chemical reaction process and provides a new solution to the low-cost pollutant emission control for CFB boilers.

Process development of sugar beet enzymatic hydrolysis with enzyme recycling for soluble sugar production

Enzymatic hydrolysis of sugar beets for achieving liquefaction and sugar release is a critical step for beet-ethanol production. An enzyme recycling process was developed in this study to reduce the economic uncertainty raised by the high costs of enzymes by reducing the fresh enzyme usage. A mixture of cellulases and pectinases was used in the beet hydrolysis. The hydrolysate was centrifuged and then processed through a 50 kDa molecular weight cut-off polyethersulfone membrane to recover enzymes from the liquid. Liquid enzyme recycling with 50% fresh enzyme addition achieved a similar liquefaction extent and sugar yield compared to the positive control with 100% fresh enzyme. Solid enzyme recycling showed a lower liquefaction efficiency, requiring at least 75% of fresh enzyme addition for a comparable liquefaction extent. Five sequential batches of hydrolysis with liquid enzyme recycling were successfully conducted to hydrolyze sugar beets with similar liquefaction extents and sugar yields.

Oxidized pellets production from stainless steel solid wastes: induration characteristics and harmful elements migration behavior

Stainless steel solid wastes (SSSW) treatment and recycling has attracted wide attention in recent years because of more stringent environment laws and regulations. Recycling of SSSW through carbothermal reduction of chromite (SRC)-electric furnace (EF) process is favorable to the effective treatment of SSSW and recovery of valuable elements. In this paper, SSSW are used to manufacture sufficiently strong oxidized pellets with the coexistence of chromite concentrates for ferrochrome production based on the SRC-EF process. The induration characteristics and harmful element migration behavior during oxidation of pellets are investigated and revealed. It is found that the oxidized pellets made from 100% SSSW possess low mechanical strength. Increasing the ratio of chromite concentrate from 0% to 80% can significantly improve the pellet strength from 460 N/pellet to 1868 N/pellet when preheating at 1000 °C for 12min and roasting at 1275 °C for 15min. Oxidized pellets made from SSSW and chromite are mainly dominated by the solid-phase consolidation due to the recrystallization of iron-rich spinel phases and sesquioxide derived from oxidation of ferrous oxides. In addition, slag bonding of CaO–CaF2–SiO2–FeO system also plays an important role in the consolidation of oxidized pellets. As for pellets made from 32% SSSW and 68% chromite concentrate, 39.96% F, 91.06% S, 66.73% Cl can be removed from the pellets when preheating at 1000 °C for 12 min and roasting at 1275 °C for 15 min.

Investigation of the mechanical and shrinkage properties of plastic-rubber compound modified cement mortar with recycled tire steel fiber

To facilitate the recycling of waste solids in cement-based materials, plastic-rubber (PR) compound modified mortar (PRM) samples and recycled steel fiber (RSF)-reinforced plastic-rubber modified mortar (PRSRM) samples were prepared and tested to evaluate their mechanical and drying shrinkage properties. PR compound particles, with a mesh size of #8, replaced the natural aggregates with four volume percentages: 2%, 5%, 7.5%, and 10%. The fiber was added with a constant volume fraction of 0.2%. Accordingly, control mortar, PRM mortar with different PR replacement ratios, and PRSRM mortar with RSF were prepared and tested. A numerical splitting tension test model was also established based on the two-dimensional Distinct Element Method (DEM) to investigate the crack initiation and propagation mechanism of the PRM samples. The mechanical test results indicated that the addition of RSF enlarged the compressive strength by 14–27% PRM samples. Meanwhile, both PR and RSF improved mortar flexural behavior by increasing the fracture energy. The SEM image of a fracture surface and DEM simulation showed the crack propagation path was changed by PR particles due to its lower stiffness. Meanwhile, the 7-days drying shrinkage length change was reduced by about 25% due to the PR’s porous structure and water-retaining ability. Overall, the sustainable material design with the combination of PR and RSF would promote the full-recycling of waste tires in cement-based materials.

Municipal solid waste incineration bottom ash recycling in concrete: Preliminary approach with Oporto wastes

The present research explored the feasibility of using dry finely ground bottom ash (GBA) from municipal solid waste incineration as SCM for concrete mixtures in cooperation with a local waste management company, LIPOR. A first study was performed using GBA as a sole partial replacement for Portland cement in paste and mortar specimens. GBA showed both beneficial and detrimental effects on paste/mortar mixtures. In terms of fresh properties, water demand on paste and workability on mortar containing GBA as cement replacement kept the same as reference specimens paste/mortars. Setting time was not affected by GBA incorporation, and ASR expansion was mitigated. The disadvantageous effect, namely, mechanical strength loss on GBA mortar, was mainly due to metallic aluminium, found on the main oxide composition and SEM of GBA, which is associated with hydrogen gas evolution. Thus, the amount of aluminium content remaining in MIBA should be analysed even after the ageing process.

Assessing the Formal and Informal Waste Recycling Business Processes through a Stakeholders Lens in Pakistan

With this study, we aim to assess integration possibilities of formal and informal waste management approaches in a low-income country context by using recycling as a tool towards sustainability. Using a holistic approach, this study examines both formal and informal aspects of recycling value chains through a stakeholder lens. Pakistan is far from being a circular economy, as evident from the dismal levels of municipal solid waste collection and recycling. This problem calls for the effective integration of formal and informal recycling business processes to fill the void. With this study, we seek to assess various aspects of formal and informal waste recycling in Pakistan through an inductive qualitative research design by examining the case of one of the most populous cities, Lahore, in the Punjab province of Pakistan. Equal representation to various stakeholders is accorded, with 25 interviews each with managers of private companies, public companies, waste pickers and scrap dealers in the target area. The study highlights that recycling sector in Pakistan is completely informal and unregulated with no or little support available due to a lack of funds and systematic planning. The empirical evidence suggests that the formal sector lacks the capacity for proper waste disposal of total waste generated. The recycling aspects are left to informal sector stakeholders who improvise to extract value from MSW in an entrepreneurial manner. The formal sector holds a bias towards informal stakeholders due to the fact that their work also serves as a theft bargain and resale platform under the guise of waste collection and recycling. The study highlights the most and least sought after recyclables, identifies gray channel markets of spare parts, metal recycling and counterfeit products, and practices of adulteration in the target area. This study recommends as a policy input, to overcome bias towards the informal sector, the creation of a central recycling commission to overlook and regulate the affairs of hitherto unregulated and informal municipal solid waste and recycling value chains.

Biomass Torrefaction Process, Product Properties, Reactor Types, and Moving Bed Reactor Design Concepts

Torrefaction, a thermal pretreatment process, is gaining attention as it improves the physical properties and chemical composition of biomass for recycling. During torrefaction, biomass is heated slowly in an inert or oxygen-deficit environment to a maximum temperature of 300°C. The torrefaction process creates a solid uniform product with lower moisture and higher energy content than the raw biomass. During torrefaction, moisture and some volatile organic compounds volatilize from the biomass. Depending on stoichiometry and other conditions, non-condensable gas species, including CO and CO2, are formed. The specific objectives of this research are to: 1) understand the impact of torrefaction on product quality in terms of the physical properties, chemical composition, and storage behavior of the biomass; 2) discuss the various reactors used for biomass torrefaction; and 3) develop a model for designing a moving bed torrefier, considering fundamental heat and mass transfer calculations. Torrefaction improves the physical properties, chemical composition, and energy and storage properties of biomass. Torrefaction of biomass at 300°C increases the energy content by about 30% as compared to the raw biomass. For example, when torrefied, the calorific value of the biomass increases from about 18–19 MJ/kg to about 20–24 MJ/kg. The torrefied material has a moisture content of about 1–3% wet basis (w.b.). The loss of the hydroxyl group during torrefaction makes the biomass hydrophobic. The brittle nature of the torrefied biomass makes it easier to grind. The devolatilization and carbonization reactions change the proximate and ultimate composition. The carbon content increases, whereas the hydrogen, oxygen, and nitrogen content of the biomass decreases. Despite its superior properties, the commercialization of torrefaction technology is slow due to challenges associated with reactor design and final product quality. The different types of reactors that are typically used for biomass torrefaction are the fixed bed, rotary drum, microwave, fluidized bed, and horizontal and vertical moving bed. The moving bed reactor has gained popularity among the different torrefaction reactor designs as it is easy to operate and scale. In addition, it helps produce a uniform torrefied product. In this paper, different moving bed torrefaction and gas recycle concepts are conceptualized to assess the features, advantages, and disadvantages of various design and operating concepts. These designs include example concepts for: 1) vertical and horizontal torrefaction reactors; 2) recycle of all or a portion of the torrefier off-gas; 3) counter and co-flowing gas and biomass in the torrefier; 4) controls for the system temperatures, pressures, flow rates, and gas compositions; and 5) the ability to sample the biomass feed, torrefied product, and gas streams for analysis as needed to investigate the thermal decomposition, physical behavior, and operational performance of the torrefaction system. The article also briefly describes the solid feed system, gas supply and recycle system, solid product management, torrefier gas monitoring, control system, and fugitive dust emissions control. The model presented in this paper includes a set of equations for basic calculations to configure the torrefaction reactor dimensions, such as diameter and height of the moving bed torrefier for different capacities based on target and calculated solids and gas velocities, residence times, and temperatures.