Improve Energy Recovery Research Articles

Improved performance and cost efficiency by surface area optimization of granular activated carbon in air-cathode microbial fuel cell

Microbial fuel cell (MFC) architectural modification is increasingly becoming an important area of research due to the need to improve energy recovery. This study presents a low-cost modification method of the anode that does not require pre-treatment-step involving hazardous chemicals to improve performance. The modification step involves deposition of granular activated carbon (GAC) which is highly conductive and provides a high specific surface area inside a carbon cloth that acts as an anode and as a supporting material. The GAC particle size of 0.6–1.1 mm resulted in an increase in air-cathode MFC performance due to an increase in available surface area of 879.5 m2 g−1 for attachment of cells based on Brunauer, Emmett, and Teller (BET) results, and an increase in the appropriate surface for attachment of cells which was rough based on the scanning electron microscope (SEM) results. On the other hand, although GAC with size of particles of 0.45–0.6 mm had the highest available surface area for attachment of cells, it lacked the appropriate surface for attachment of cells and reduced MFC performance. This means that particle size optimization of GAC is essential since there is a limit to which the particle diameter can be reduced. The utilization of the GAC with the optimized particle size produced an output voltage of 507.5 mV and maximum power output of 1287.7 mW m−3 at current output of 2537.5 mA m−3. This study also showed that there is an economic benefit in modifying carbon cloth using GAC with optimized particle size.

Study on heat extraction performance of multiple-doublet system in Hot Sedimentary Aquifers: Case study from the Xianyang geothermal field, Northwest China

Hot Sedimentary Aquifers (HSA) are often rich in geothermal resources that are particularly suitable for direct-use. Fully understanding the effect of well layout and primary geological /human-controlled parameters in a multiple-doublet system on the fluid flow and heat transfer processes is imperative to achieve efficient heat extraction in HSA. In this study, two multiple-doublet layouts, chosen by considering the natural groundwater flow direction, reinjection-well-led (R-led) scenario and production-well-led (P-led) scenario, are proposed. Their heat extraction performance in hot sedimentary reservoir models based on Xianyang geothermal field in the Guanzhong Basin, Northwest China is systematically investigated using the coupled thermal-hydraulic modeling and economic analysis. Results indicate that thermal breakthrough occurs earlier in the production zone when the reinjection induced artificial flow is in the same direction as the natural flow. Under the P-led scenario, which is superior to the R-led scenario in preventing premature thermal breakthrough and lowering the Levelized Cost of Heat (LCOH), the doublet lifetime and energy production are increased by up to 36% and 33%, respectively. The optimization of multiple-doublet layout can improve energy recovery in reservoirs with greater permeability. In the case of the minimal negative interference of the natural flow field and adjacent geothermal production, the energy production can be increased by up to 2.2 times. Furthermore, due to the integrated effects of the higher energy production and larger initial investment in the deeper reservoir, the LCOH and its dependence on well depth decrease with reservoir depth. Sensitivity analysis highlights that a 10% decrease in the drilling cost can lower the LCOH by 6.4% for the deepest reservoir. This study will contribute to the optimization of the design of multiple-doublet systems for efficient geothermal exploitation in HSA.

Debottlenecking of existing hydrocracking unit by improved heat recovery for energy and carbon dioxide savings

The problem of energy use is one of the challenges of modern society. It is connected not only with the generation of harmful emission but also with the use of other associated resources. Energy efficiency in industry is one of the cleanest energy sources due to not generating energy. Current work proposes an approach for reducing primary energy use and harmful emissions at the oil refinery via thermodynamic analysis of process and energy streams and definition of an energy recovery potential. The proposed approach is based on the systematic reduction of energy consumption by an energy audit, a detailed process and units simulation, improved energy recovery and identifying the most reliable and economically viable process changes. It includes the heat and utility exchanger network analysis by grid diagram to find an energy gap and main drawbacks. The case study represents an application of the proposed method at the hydrocracking unit, where a considerable potential for energy efficiency was identified and utilised. The retrofit option was developed to show how debottlenecking and process changes contributes to overall operational efficiency. As a result, the energy consumption was cut by 54% and the economic efficiency of the proposed process changes confirmed by the discounted payback period of 9.5 months, excluding the time for the detailed design, equipment purchase, installation and start-up. Environmental results demonstrate the annual saving of 18,915 tons of carbon dioxide. Due to the slowing down of global economic growth, more attention should be paid to the modernisation of existing process plants. It may speed up the transition to an environmentally friendly economy and help solving global problems.

Effect of silane coupling agent on the mechanical steel of sugarcane baggase and polypropylene composites

A composite material is produced by combining two or more materials to give a specific combination of properties, one consisting of rigid, long fibres and the other a binder or ‘matrix’ holding the fibres in place. Compared to the matrix, the fibres are strong and stiff, typically orthotropic. More recently, natural fibres were used in plastics. The broad availability of natural fibre in India, such as Jute, Coir, Sisal, Pineapple, Ramie, Bamboo, Banana, etc., pays specific attention to the manufacture of natural fibre composites to pursue value-added applications. This natural fibre composites are well suited to substitute wood in homes and manufacturing. Natural fibre reinforcement in composites has recently drawn ads due to low cost, low density, fair basic features, fast separation, improved energy recovery, CO2 neutrality, biodegradability and recyclability. Thousands of tonnes of different crops are made, but most of their waste is useless. It contains wheat husk, rice husk and grass, hemp fibre and dried fruit shells. These agricultural waste may be used for fibre-reinforced polymer composites for commercial usage. This project explores the impact of the silane binding agent on the mechanical properties of the sugar cane baggase and polypropylene compounds. Coupling agent is the agent used to strengthen the connection between the reinforcement and the matrix. In this plant, silane was used as a binding agent for sugar cane bagasse bio-composites. Reinforcement content treated with a binding agent at varying concentrations of 0 per cent, 10 per cent, and 20 per cent. This element was present in the compression moulding method for the manufacture of composite boards. The influence of the silane binding agent on the mechanical properties of the composites, such as the tensile, flexural and impact forces, was evaluated.

Energy-Efficient Braking Torque Distribution Strategy of Rear-Axle Drive Commercial EV Based on Fuzzy Neural Network

<div class="section abstract"><div class="htmlview paragraph">Regenerative braking is identified as an essential step toward extending cruising mileage for electric vehicle (EV). Braking energy recovery strategies usually focus on passenger EV and commercial EV is ignored. In this paper, an energy-efficient braking torque distribution strategy is proposed for a rear-axle drive commercial EV to improve braking energy recovery and safety. Firstly, the braking force distribution curve is determined referring to the EU braking law for commercial vehicle and the ideal braking distribution curve. Secondly, a novel braking torque distribution strategy is established adopting fuzzy control algorithm, where the ratio between hydraulic braking torque and regenerative braking torque is updated instantaneously according to vehicle velocity, braking strength and state of charge of battery. Then, the corresponding controller is synthesized on ideal braking condition and several classic cycles. To further enhance the performance of the controller, a neural network based framework is established to optimize the membership function in fuzzy controller. Simulations on ideal braking condition demonstrate the controller can always meet emergency braking needs. For the standard cycles, including NEDC and WLTC, the energy-efficient strategy based on fuzzy control can recover up to 18.88% and 16.56% of energy under NEDC and WLTC cycles, and on this basis, the optimized strategy based on adaptive neuro-fuzzy control can improve energy recovery by 2.84% and 3.6% under these two cycles. The developed braking torque distribution strategy can potentially be embedded in real-time supervisory systems to realize the energy saving and increase the cruising mileage for commercial EV.</div></div>

Influence of the operating conditions of the intermediate thermal hydrolysis on the energetic efficiency of the sludge treatment process

The application of steam explosion between two stages of anaerobic digestion may improve energy recovery from sludge while increasing organic matter removal. The influence of the operating conditions of the thermal process: temperature (130–210 °C), retention time (5–45 min) and TS concentration (5.4–10.8%), on the efficiency of VS removal, the biochemical methane potential of hydrolysed sludge and the kinetic constant of the degradation were evaluated using a Taguchi design. Increasing temperature and time increased the removal of VS and the potential of methane production but the kinetic constant was higher at lower temperatures. An optimal operating scheme was found at 170 °C (6 barg), 25 min at the greatest TS concentration in the feeding. Under such conditions, the thermal energy obtained from biogas combustion in a CHP covered the requirements for vapour generation and a profit of 3.54 € m−3 of sludge was estimated.

EXERGY AND EMERGY: COMPLEMENTARY TOOLS FOR ASSESSING THE ENVIRONMENTAL SUSTAINABILITY USE OF BIOSOLIDS GENERATED IN WASTEWATER-TREATMENT PLANT FOR ENERGYPRODUCTION

Taking advantage of the energy contained in the biosolids generated in a wastewater treatment plant (WWTP) is one of the processes of greatest interest due to the opportunity to obtain an energy resources from a waste. The aim of this research was to analyze the environmental sustainability use of biosolids generated in a wastewater-treatment plant for energy-production by fluidized-bed gasification under exergy analysis. The energy-production system was based on previous studies of sustainable-emergy alternatives using biosolids. Sustainability of the process was evaluated by identifying stages in the energy-production system (from drying application to electricity generation) where it is possible to reduce useful energy losses as well as identifying the value of waste streams within the system through exergy analysis. It was illustrated the destroyed exergy and the efficiency by stage and by product in order to assess the effects of inefficiencies in the process sustainability. The mixture of biosolids with coal was identified as a highly sustainable stage of the process, as it presents the highest index of exergy sustainability (0.99), in contrast to the stages of energytransformation (turbine) and gas-cleaning, which efficiencies are 0.17 and 0.4, respectively. Energy-transformation and gas-cleaning stages are of interest in terms of an improved energy recovery process, making it more efficient by applying new technologies and/or using the waste streams that have high energy potentials.

Generalized models to predict the lower heating value (LHV) of municipal solid waste (MSW)

Accurately and efficiently predicting the LHV of MSW is vital for designing and operating a waste-to-energy plant. However, previous prediction models possess limited geographical applicability. In this paper, we employ multiple linear regression and artificial neural network (ANN) techniques to predict LHV. These data-driven models utilize 151 globally distributed datasets identified during a systematic literature review, describing the wet physical composition of MSW and measured LHV. The results show that models built via both methods exhibited acceptable and compatible levels of performance in predicting LHV, based on the multiple statistical indicators. However, the ANN model proved to be more robust in handling of datasets of diverse quality. Models developed from both methods demonstrate clearly that the wet proportion of food waste has a negative impact on LHV. Supported by the strong and significant correlation between food waste and moisture content, we concluded that the negative impact of high moisture content in food waste on LHV outweighed its calorific value. Separating food waste or any other waste with high moisture content from the MSW for incineration can significantly improve energy recovery efficiency. Contrary to expectation, the models also reveal a higher contribution of paper waste to the LHV of MSW than plastic waste.

Optimal Anti-Lock Braking Control With Nonlinear Variable Voltage Charging Scheme for an Electric Vehicle

An optimal anti-lock braking control strategy using nonlinear variable voltage charging scheme for an electric-wheel vehicle is developed with aim of improving energy recovery efficiency on the premise of vehicle safety under the critical braking situation. A variable voltage charging control scheme is proposed with its operational principles to obtain maximum energy recovery as well as to balance the energy differences of each battery cell during the anti-lock braking. Given the nonlinearity of in-wheel motor, the nonlinear variable voltage charging control law is obtained on the basis of parameters fitting via experimental data. An ideal regenerative braking torque calculated by the nonlinear variable voltage charging control law is set as one of the disturbance vectors and an optimal sliding mode–anti-lock braking control strategy is developed to provide optimal hydraulic pressure for anti-lock braking system. In this manner, the torque allocation process is omitted by using a compensation control of the hydraulic braking torque. Simulation results corroborate the effectiveness of the proposed optimal anti-lock braking control strategy with higher energy recovery efficiency.

Evaluation of the potential beneficial pyrolyzed product yields from sewage sludge and bone waste disposal

Abstract Biomass such as sewage sludge (SS) applications has witnessed bio-char production and renewable energy yield via various thermal processes such as pyrolysis. At the same time, additional augmentation routes for improving energy recovery, high agronomy solutions to global issues of food deficient, and crop production matrix in the future still need to be sought. This research offers information on 10 wt% bone residues (BR) co-pyrolyzed with SS in a fixed bed reactor at 400 and 600 °C, and at the heating rate of 25 °C min−1. The H/C atomic ratio and calorific value for SS bio-oil were 1.10 and 17.50 MJ/kg, which increased to 1.30 and 20.13 MJ/kg, respectively, for the SSBR10 bio-oil. The SSBR10 biochar quality indicated satisfactory features to improve agronomy performance with a significant reduction in the oxygen content 4 wt%; since higher oxygen content biochars are prone to decompose within an elongated period. The results from this study are vital to simulate further developmental phases in pyrolysis system operation and design for the co-pyrolysis of SS and BR to generate beneficial products.

Experiments on the thermally enhanced permeability of tight rocks: A potential thermal stimulation method for Enhanced Geothermal Systems

ABSTRACT Creating a good fracture network in hot dry rocks is the key to the success of an Enhanced Geothermal Systems project. Instead of creating large-scale fractures, the proposed thermal stimulation method has clear advantages by generating small-scale cracks, increasing crack density, and forming fracture networks in tight rocks. Granite samples from a tight formation in Lijin County in China were thermally treated at various temperatures to evaluate the permeability enhancement and the feasibility of thermal stimulation. Scanning electron microscope (SEM) method was also used to investigate the changes in interior structure in granite rocks. The experiments show that the threshold temperature of Lijin granites is around 300°C, the permeability can improve approximately 2 orders and the porosity can increase more than 5 times when heating over 600°C. Both crack length and width increase about 10 folds under the experiment conditions, and the original mineral disappearance and new mineral generation were observed. Thermal cracking under high temperatures plays a key role in permeability and porosity enhancement. Numerical simulation results show that the heated zone is very limited if only heating in a borehole. To expand the affected zone and improve energy recovery, a new thermal stimulation method combining microwave excitation with proppants to heat inside hydraulic fractures is proposed and discussed.

Real-time realization of Dynamic Programming using machine learning methods for IC engine waste heat recovery system power optimization

This study aims to present a method for real-time realization of Dynamic Programming algorithm for power optimization in an organic Rankine Cycle waste heat recovery system. Different from existing studies, for the first time machine learning algorithms are utilized to extract the rules from offline Dynamic Programming results for optimal power generation. In addition, for the first time a single state Proper Orthogonal Decomposition and Galerkin Projection based reduced order model is combined with Dynamic Programming for its high accuracy and low computation cost. For a transient driving cycle, Dynamic Programming algorithm is utilized to generate the optimal working fluid pump speed. A total of eleven state-of-art machine learning algorithms are screened to predict this pump speed. Random Forest algorithm is then selected for its best pump speed prediction accuracy. A rule-based method is added to the Random Forest model to improve energy recovery. As one of the main discoveries in this study, in the rule extraction process, the Random Forest model reveals that the time delayed exhaust gas mass flow rate and exhaust temperature improve the rule extraction accuracy. This observation points out the difference between steady state and transient optimization and that the steady state optimization results do not necessarily hold true in transient conditions. Another key observation is that Random Forest – rule-based method retrieves 97.2% of the energy recovered by offline Dynamic Programming in a validation driving cycle. In addition, the inclusion of rule-based method significantly increases the Random Forest model’s energy recovery from 66.5% to 97.2%. This high accuracy means that the machine learning models can be used to extract Dynamic Programming rules for real-time application.

Four-Wheel Electric Braking System Configuration With New Braking Torque Distribution Strategy for Improving Energy Recovery Efficiency

In this paper, a four-wheel electric braking system configuration is proposed for electric vehicles and its braking performance is compared with other conventional braking system configurations at different initial vehicle speeds and different road conditions in the case of emergency braking. In order to make the vehicle wheel slip ratio track the optimal slip ratio, a control method that combines sliding mode control and extended state observer is designed. Neural-network sliding mode control is designed for the driver’s braking command tracking in the normal braking condition. In order to improve braking energy recovery, a new braking torque distribution strategy is developed for the proposed four-wheel electric braking system based on the motor characteristics and vehicle dynamics. The designed braking torque distribution strategy is able to improve the energy recovery by adjusting the braking torque distribution ratio between the front and rear wheel braking torque while tracking the driver’s braking command. Numerical simulations have been conducted and the simulation results show that although the braking performance of the four-wheel electric braking system is worse than the conventional braking system at high initial braking speed, it still is able to meet the vehicle braking international standards and simplifies the braking system structure and saves cost. The proposed braking torque distribution strategy can improve energy recovery efficiency compared with the average allocation strategy and deceleration based allocation strategy. The simulation results show that the four-wheel electric braking system configuration with the proposed braking torque distribution strategy is suitable for low to medium speed light electric vehicles.

Evaluation and Improvement of Energy Utilization Efficiency in Typical Iron and Steel Smelting Route Based on Input‐Use‐End Model

Evaluating the energy efficiency of the iron and steel smelting route is of vital significance to achieve energy saving and consumption reduction. By establishing an input‐use‐end model, a new index is put forward herein to evaluate the energy utilization of the iron and steel smelting route—energy utilization efficiency. Furthermore, energy utilization efficiency of a typical iron and steel smelting route is analyzed based on the established network diagram. The results show that 1) the cleaned coal is the largest energy input in the whole route, which is 14 460.4 MJ, followed by injected coal. 2) About 57.6% of primary energy is converted into byproduct gases and 31.7% of that is converted into various waste heats. 3) The energy loss of the whole route is 9583.8 MJ, of which the direct loss, indirect loss, and internal loss are 2630.8, 5366.9, and 1586.1 MJ, respectively, accounting for 14.5%, 29.5%, and 8.7% of the total purchased energy. 4) The energy utilization efficiency of the whole process is 47.6%. 5) Improving energy recovery is the most effective measure to improve energy utilization efficiency instead of degrading energy input and changing product structure.

An intelligent braking system composed single-pedal and multi-objective optimization neural network braking control strategies for electric vehicle

The braking system is significant to improve the total energy efficiency and ensure driving security of electric vehicles. An intelligent braking system (IBS) composed single-pedal and multi-objective optimization neural network braking control strategies is proposed in this paper to improve the energy economy, braking stability and driving intelligence for electric vehicles. The braking operations of drivers are divided into two parts: (1) releasing the accelerator pedal and (2) stepping on brake pedal. In the first braking operation, a single-pedal regenerative braking control strategy (RBCS) of accelerator pedal based on adaptive fuzzy control algorithm is proposed to improve energy recovery and driving intelligence. Simulation results illustrate that the simulation velocities under the control of adaptive single-pedal RBCS can follow several standard test cycles (including US06, UDDS, LA92 and ECE) very well. The braking energy can be recovered effectively with a less usage of brake pedal. In the second braking operation, a neural network (NN) controller for the composite braking system (CBS) is proposed to optimize the energy economy and braking stability at the same time. The control effect is verified by simulation results under NEDC cycles. The hardware-in-loop (HIL) experiments of the IBS are also conducted in this paper. Compared with a parallel braking strategy used in EU260 electric vehicles, the energy economy of IBS is improved by 3.67% than EU260 in 3 NEDC cycles. IBS performs more closely to the I curve in a specific braking condition with a decreasing braking severity. The time ratio of hydraulic braking in IBS is 2.27% less than EU260 with an increasing driving intelligence.

A hydraulically optimized fluidized bed UF membrane reactor (FB-UF-MR) for direct treatment of raw municipal wastewater to enable water reclamation with integrated energy recovery

A hydraulically optimized pilot-scale fluidized bed ultrafiltration membrane reactor (FB-UF-MR) for water reclamation with integrated energy recovery was designed and operated for 576 days with raw municipal wastewater from a local wastewater treatment plant (WWTP). The design of the reactor and the fluidized bed flow regime were optimized by a computational fluid dynamic (CFD) model. By adopting a customized impact plate in the design, the recirculation flow rate could be reduced by approximately 38% lowering the energy demand significantly. Granular activated carbon (GAC) was used as fluidized medium and proved as successful fouling mitigation strategy, even at low concentrations of 1.7–3.3 g/L (based on total reactor volume) or 21–41 g/L (based on fluidized bed volume) as compared to previous studies. The optimal operational conditions of the FB-UF-MR were identified at (i) a sustainable flux of 8–10 LMH, (ii) an optimal backwash flux of 1.2 times of the permeate flux, (iii) an operational cycle of 10 min consisting of 9 min filtration and 30–60 sec backwashing and optional 30 sec relaxation. Chemical cleaning was applied every 4–6 weeks during long-term operation. Main foulants of the wastewater matrix were identified by 3D-fluorescence excitation-emission matrix (3D-EEM) measurements coupled with parallel factor (PARAFAC) analysis suggesting that protein-like organic matter were the main constituent of the cake layer. The results of this study indicate that direct treatment of raw municipal wastewater with UF is a promising option. Thus, it is possible to concentrate C and N (in a subsequent treatment step) for improved energy recovery while facilitating water reclamation.

Improving Energy Recovery Rate of the Regenerative Braking System by Optimization of Influencing Factors

The braking energy can be recovered and recycled by the regenerative braking system, which is significant to improve economics and environmental effect of the hydraulic hybrid vehicle. Influencing factors for the energy recovery rate of regenerative braking system in hydraulic hybrid vehicle were investigated in this study. Based on the theoretical analysis of accumulator and energy recovery rate, modeling of the regenerative braking system and its energy management strategy was conducted in the simulation platform of LMS Imagine Lab AMESim. The simulation results indicated that the influencing factors included braking intensity, initial pressure of the accumulator, and initial braking speed, and the optimal energy recovery rate of 87.61% was achieved when the parameters were 0.4, 19 MPa, and 300 rpm, respectively. Experimental bench was constructed and a series of experiments on energy recovery rate with different parameters were conducted, which aimed to validate the simulation results. It could be found, that with the optimal parameters obtained in the simulation process, the actual energy recovery rate achieved in the experiment was 83.33%, which was almost consistent with the simulation result. The obtained high energy recovery rate would promote the application of regenerative braking system in the hydraulic hybrid vehicle.

A direct multiple shooting method to improve vehicle handling and stability for four hub-wheel-drive electric vehicle during regenerative braking

Regenerative braking is an important technology to improve fuel economy for electric vehicles. Apart from improving energy recovery efficiency and vehicle stability, the arithmetic speed of the algorithm is also essential for an automotive-qualified micro control units. This paper presents a direct multiple shooting method–based algorithm to achieve multiple objectives for four hub-wheel-drive electric vehicle during mild braking situations. Mathematical models of the system are generated for numerical simulations in MATLAB, including a vehicle dynamics model, a modified tire model, a single-point preview driver model, and a regenerative braking motor efficiency map. With the limitation of hard constraint and minimization of adjustment rate in cost function, optimization tends to be accomplished by distribution of braking torque in front and rear wheels. Furthermore, the control strategy has been realized using a direct multiple shooting method to convert the nonlinear optimal control problem to a nonlinear programming problem, which will be settled by adopting a sequential quadratic programming method in each subintervals. The effectiveness and adaptation of the control strategy for four hub-wheel-drive electric vehicle has been evaluated by conducting many simulations during mild braking situations, and the simulation results also demonstrated that the direct multiple shooting–based strategy exhibits a better performance than that of proportional-integral-based or nonlinear model predictive control–based controller.

Techno-economic assessment of an integrated high pressure chemical-looping process with packed-bed reactors in large scale hydrogen and methanol production

A full-scale techno-economic analysis of a novel chemical looping based process using dynamically operated packed bed reactors has been carried out for the large-scale production of hydrogen (up to 30,000 Nm3/h) and methanol (up to 10,000 tons per day) with inherently integrated CO2 capture. The complete process is carried out in three main reactors, in which the reactions occurring are the dry and steam reforming of natural gas with H2O and CO2, the oxidation of the oxygen carrier (OC) with air and the reduction with a low-grade fuel such as plant off-gases. The thermal balance of the process is achieved by combining the endothermic reforming reaction with the exothermic chemical looping combustion. The chemical looping based process is fully integrated with the separation and synthesis units as well as the power and heat utilities of the two large scale production plants. The two plants are compared with state-of-the-art technologies, including the benchmarks for hydrogen and methanol production from natural gas through steam reforming and auto-thermal reforming. Compared to a conventional H2 production plant (without CO2 capture), the reforming efficiency is 3% higher, while the required primary energy consumption to separate CO2 is 0.47 MJLHV/kgCO2 which is significantly lower than that of an amine-based plant (>1.35 MJLHV/kgCO2) and the cost of hydrogen production with the proposed process is 2.19 $/kg with a CO2 avoidance cost of 58.7 $/tonCO2 (compared to > 70.6 $/tonCO2 for solvent based plant). In case of methanol production, the carbon conversion is comparable with the best available processes even though CO2 purification and separation (98% capture with >96% purity) units are included due to the improved energy recovery. By using chemical looping the cost of methanol production decreases overall by 17% compared to the benchmark plant due to the lower investment cost and higher electricity generation resulting overall in a negative CO2 avoidance cost (-303 $/tonCO2).

Effect of hydrothermal carbonization as pretreatment on energy recovery from food and paper wastes

In this study, food waste (FW) and paper wastes were subjected to hydrothermal carbonization (HTC) with a purpose to improve energy recovery potential. FW is suggested as the suitable feedstock for production of hydrochar (HC) having highest calorific value (29.6 MJ/kg). Carbon content in FW derived HC was increased from 50% to ∼72% whereas energy retention efficiency was found to be 5.74 times of that in FW. Wastewater recovered after HTC of FW was rich in carbohydrates with chemical oxygen demand of ∼56,000 mg/L which may further be subjected to anaerobic treatment for biogas generation. Energy balance calculations showed that the solid and liquid fractions recovered after HTC of FW yielded highest energy output (2950 kJ/kg FW) compared to incineration (2217 kJ/kg FW), anaerobic digestion (2605 kJ/kg) and in-vessel composting. HTC process can be adopted as decentralized facility by institutions where highly moisturized wastes are generated.