Feedstock Gas Research Articles

Comparative study on air gasification of plastic waste and conventional biomass based on coupling of AHP/TOPSIS multi-criteria decision analysis

A broad range of conventional biomass and plastic waste types was considered and their air gasification process was modeled using a Gibbs free energy minimization coupled with Lagrange multiplier approach. The comparison between the performances of biomass and plastic waste gasification is the main issue of this study. Another important novelty and contribution of this study is analytical hierarchy process/technique for order performance by similarity to the ideal solution coupled method that is employed in gasification of conventional biomass and plastic waste, to prioritize the considered criteria and to select the best feedstock for gasification. Hydrogen production was linearly reduced in the case of conventional biomass with an in increase in the equivalence ratio; however, there was an optimum equivalence ratio to achieve the highest hydrogen production in plastic waste gasification. Plastic waste had a higher low heating value compared to conventional biomass. However, carbon monoxide and nitrogen production from conventional biomass was smaller than from plastic waste. Ten types of feedstock, comprising six types of conventional biomass and four types of plastic waste, were selected as alternatives. The multi-criteria decision analysis coupled method revealed that waste polypropylene and polyethylene were the best alternatives.

Evolution of vacuum ultraviolet emission in dual-frequency capacitively coupled plasmas

In plasma material processing, vacuum ultraviolet (VUV) emission is released from gas discharges, leading to undesirable results. Energetic VUV photons enable the creation of an electron-hole pair current when their energy is larger than the bandgap energy of the plasma-facing top layer during plasma material processing. For example, the high energy of VUV photons from helium (21.2 eV), argon (11.6 eV), and oxygen (13.6 eV) is sufficient to generate induced currents in SiO2 thin films. These feedstock gases are widely used in many procedures utilizing low-temperature industrial plasmas. Thus, the VUV emission evolution with both the power ratio between high (60 MHz) and low (2 MHz) frequencies and pulse duty ratio of the low-frequency radio frequency (rf) power in a dual-frequency capacitively coupled plasma, which is indispensable in modern plasma etching processes, was investigated. Both the power ratio between high and low frequencies and the pulse duty ratio changed the electron temperature, leading to evolution of the VUV emission intensity.

Mesoscale bubble dynamics in the gasifier of a 1MWth dual fluidized bed gasifier for biomass gasification

Via the multiphase particle-in-cell method, the gasification of biomass feedstock in a pilot-scale dual fluidized bed gasifier is simulated to study the dynamical behavior of mesoscale bubble structure in this complex apparatus. After comparing the simulated data with the experimental results, the flow dynamics of rising bubbles together with the quantitative assessment of bubble properties in the gasifier are studied. The results observe that: (i) different from the traditional bubbling fluidized gasifier, two preferential rising paths of the bubbles exist due to the special gasifier geometry and the gasification of biomass; (ii) bubbles generated above the biomass inlet have the largest chord length along the depth direction and vigorous lateral motion. Bubbles close to the left side wall and newly generated above the biomass inlet have an apparent large rising velocity; (iii) the presence of biomass inlet reduces the bubble temperature by a value of 50 K and increases the bubble density with a value of 0.05 kg/m3 near the biomass inlet. The large thermal property of rising bubbles appears along the right path, while the large mass fraction of the gaseous product exists for bubbles along the right path.

Enhancing the intermediate-temperature CO2 capture efficiency of mineral MgO via molten alkali nitrates and CaCO3: Characterization and sorption mechanism

Carbonate looping using MgO-based sorbents has recently aroused the scientific interest as an auspicious technology for intermediate temperature (200−400 °C) CO2 capture, with the main hindrance being the slow sorption kinetics of MgO. This study investigated the preparation of MgO-based sorbents derived from mineral magnesite and promoted with a mixture of Li, Na and K nitrates, which by shifting into a molten state can reinforce the CO2 capture kinetics. Mineral limestone was also tested as promoter, which enabled the formation of CaMg(CO3)2 as another carbonate product except MgCO3. In-situ X-ray diffraction was employed to interpret the sorption mechanism of materials with different promoter contents and under various operating conditions. Even though CaMg(CO3)2 required a minimum temperature of 300 °C for formation in contrast to MgCO3, it generally displayed a faster nucleation rate, which was profitable mainly when applying a low CaCO3 to MgO molar ratio. However, the CaMg(CO3)2 decomposition demanded higher temperatures than MgCO3, which were associated with more pronounced sintering of the sorbent and elevated energy requirements of the process. The increase of the alkali nitrate content led to a deterioration of the pore network, but also enabled a faster generation and growth of carbonate products. Lowering the CO2 concentration of gas feedstock for more realistic carbonate looping applications required a slightly milder operating temperature for efficient CO2 sorption to enhance both CO2 solubility and carbonation kinetic driving force. The results proved the feasibility of mineral ores as sustainable low-cost precursors for intermediate-temperature CO2 capture.

(Invited) A Continuous, Atmospheric-Pressure Plasma-Water Droplet Reactor for Nitrogen Fixation

Ammonia production via the Haber-Bosch process has a large carbon footprint due to the hydrogen gas feedstock. One possible solution is to use water as the hydrogen source in a process-intensified scheme whereby ammonia is produced by directly reacting nitrogen gas and water. Toward this end, we investigated a catalyst-free, atmospheric-pressure plasma process to continuously produce ammonia from nitrogen gas and atomized water droplets. Through several control experiments, the production of ammonia and other forms of fixed nitrogen were confirmed. By comparing water droplets versus water vapor as a feed to the reactor, it was discovered that the ammonia forms through gas-phase chemistry and the liquid phase does not appear to significantly contribute. By comparing hydrogen gas to oxygen gas and water as a feedstock, insights into the reaction mechanism were made. When hydrogen gas was used, no nitrates or nitrites were synthesized as expected, and the ammonia production was comparable to water, indicating similar mechanisms involving feedstock dissociation to atomic hydrogen may be occurring. When oxygen gas was used, no ammonia or nitrates/nitrites were detected, which suggests that water provides a unique reaction pathway for nitric and nitrous acid to form in the gas phase. Our study demonstrates that simple nitrogen gas and water droplets can serve as feeds in a plasma process for the sustainable and distributed production of ammonia or other fixed nitrogen compounds.

Comparative Study of Kinetic Hydrodynamic Theoretical Model Results in Fluidized Bed Reactor Using Different Fuels.(Dept.M)

This work presents a comparative study on different biomass feedstock gasification in a fluidized bed using air. This work aims to study the effect of different biomass fuel types on the gasification performance in a fluidized bed, using kinetic hydrodynamic model results and similar experimental results. The feedstocks used in this study are sawdust pellets, Napier Grass, Portuguese Peach Stone, Chinese Coal /rice straw, solid waste wood, rice straw and olive kernels. The theoretical results were obtained from the kinetic-hydrodynamic simulation of the fluidized bed. The theoretical results were compared with published experimental results. The results showed that the syngas contents are strongly affected by the gasification temperature, equivalence ratio, and fuel characteristics. Increasing ER increases the char burning rate to produce more H2 even medium equivalence ratio (usually less than 0.36) and decreases again. CH4, CO, and H2 increased as temperature increased. From the fuel proximate analysis, the moisture contents affect the combustion reactions to generate more hydrogen. The lower H/C ratio gives greater heating value, as well as gives more concentrations of CO and CO2. In the case of using waste woody and rice straw, the significant increase of carbon monoxide (from 9% to 19%) and carbon dioxide (from 25% to 33.1%) is due to a higher C/O ratio in these biomasses analyses. The proximate analysis of feedstock and its contents from fixed carbons and volatiles matters affect strongly the producer gas concentrations, as a result, it’s LHV. The maximum relative error between model results and experimental results within range ±10.2%.

Prediction and optimization of syngas production from steam gasification: Numerical study of operating conditions and biomass composition

Prior information regarding the effects of the operating conditions and biomass composition on the syngas production is critical to predict and optimize the syngas production. Therefore, this paper proposes an effective method to predict and optimize the syngas production by combining a process model and data analysis techniques. Three agricultural waste types from Northeast China and 56 biomasses with different compositions were used as the gasification feedstock to investigate the effects of the operating conditions and biomass composition on the syngas production. A validated Aspen Plus process model was implemented to realize the biomass gasification process and techno-economic analysis. The sensitivity analysis results indicated that a lower temperature (approximately 600 ℃) and lower steam-to-biomass ratio (S/B) (approximately 0.1) were the optimal operating conditions to achieve a higher lower heating value (LHV) of syngas. The introduction of steam changed the relationship between the temperature and LHV of syngas from inverse to direct. Furthermore, the performance comparison of the three agricultural waste based gasification processes indicated that a higher temperature and higher S/B could weaken the effect of the C, H, and O contents on the syngas composition. More importantly, the partial correlation analysis of the 56 sets of simulation results highlighted that a higher content of C and H, C/O and C/H helped enhance the LHV of syngas. The C/O value and C content exhibited the most significant correlations with the LHV of syngas, with correlation coefficients of 0.945 and 0.840, respectively. Correspondingly, these parameters exhibited a reasonable linear response with the LHV of syngas, with R2 values of 0.864 and 0.533, respectively. Finally, the techno-economic analysis indicated that SS is the optimal feedstock for syngas production.

Integrated hydrogen liquefaction processes with LNG production by two-stage helium reverse Brayton cycles taking industrial by-products as feedstock gas

Hydrogen-rich industrial by-products, such as coke oven gas (COG) and synthetic ammonia exhaust tail gas, are often simply utilized as fuel gas, or even not utilized at all in many cases. An innovative and efficient utilization method is proposed and investigated in this paper. Aiming to coproduce liquid hydrogen and liquefied natural gas (LNG), three helium reverse Brayton cycles are constructed, optimized, analyzed and compared. The LN-He-1 process is constructed with reference to conventional industrial hydrogen liquefaction processes, but with different feedstock gas. The LN-He-2 and N–He processes, which are an improvement on the basis of LN-He-1. A combination of distillation and flash is utilized to reduce the separation load. Analysis of load variation, power consumption, exergy, heat transfer and turbomachinery efficiencies are carried out. For different feedstock gas compositions, the specific power consumptions of LN-He-1, LN-He-2 and N–He processes are within 26.45–54.78 kWh/kmol (feedstock gas), 26.32–53.78 kWh/kmol (feedstock gas) and 21.94–50.42 kWh/kmol (feedstock gas), respectively. The exergy efficiencies are between 13.0% and 66.5%.

Low-carbon production of iron and steel: Technology options, economic assessment, and policy

Summary Given increased urgency to transition the global economy to net-zero CO2 emission, governments and industry have increased focus on decarbonizing hard-to-abate sectors, including steel making, which contributes roughly 6% of global CO2 emission and 8% of energy-related emission (including power consumption emission). This paper reviews current global iron and steel production and assesses available decarbonization technologies, including hydrogen injection, solid biomass substitution, zero-C electricity substitution, carbon capture and storage (CCS) retrofit, and combinations of these decarbonization approaches. Blast furnace-basic oxygen furnace (BF-BOF) dominates production (71%) and is particularly stubborn to any decarbonization technology. Direct reduced iron to electric arc furnace (DRI-EAF) production is 5% and growing, it appears to have better decarbonization potential to move toward net-zero. Secondary steel production using mainly steel scrap in electric arc furnace (EAF-scrap) is 24% of global production and has both the lowest energy consumption and is technically simplest to decarbonize through electrification but is limited in market share to recycled steel capacity. Of the options assessed, blue hydrogen, carbon neutral biomass, and CCS appear to have the lowest cost and highest technical maturity. However, no single approach today can deliver deep decarbonization to the iron and steel industry and all approaches lead to substantial production cost increase. No uniform ideal solution exists, and different geographies, infrastructure, and economies will determine the local optimum solution with viability and cost. Policy measures will be required to provide financial incentives for decarbonization and to avoid unwelcome outcomes such as emissions leakage or job loss.

CO2-Tolerant Cryogenic Nitrogen Rejection Schemes: Analysis of Their Performances

In the transition to a sustainable energy future, natural gas is a key player supporting a shift away from coal, where renewables and other nonfossil fuels may not be able to grow sufficiently on their own. The growing importance of natural gas has led to a re-evaluation of the potential of unconventional, stranded, and contaminated gas reserves that were previously considered economically unviable. Among them, nitrogen-rich natural gas feedstocks, which in the past were thought to be a not-so-interesting methane source, are now becoming a considerable fraction of the total treated gas. For this kind of low-quality gases, nitrogen removal is necessary to lower the inert content and to produce a pipeline-quality gas or liquefied natural gas (LNG). Considering the available nitrogen removal technologies, cryogenic nitrogen rejection is nowadays the leading one for large-scale applications, with capacities exceeding 0.5 million standard cubic meters per day (MSCMD), being very flexible regarding the inlet N2 content. Depending on the feed composition, different nitrogen rejection units (NRUs—i.e., the single-, the double-, and the three-column systems) are available for treating inlet gas mixtures. The aim of the present work is to evaluate the performances of different cryogenic nitrogen rejection schemes through energy and exergy analysis. Specifically, single-column and three-column nitrogen rejection schemes have been considered with various natural gas feed compositions, focusing on the range where different nitrogen removal schemes are applicable. The net-equivalent methane analysis accounts for the amount of methane required to supply the overall process energy demands through specific processes assumed as reference. On the other hand, exergy analysis evaluates the exergy efficiency of each process scheme through a thermodynamically rigorous approach, converting energy and material flows into their exergy equivalents. Results prove that the three-column process scheme reaches the highest thermodynamic performances, resulting in the best values of exergy efficiency and equivalent methane requirements with respect to the other configurations. This is mainly due to the lower prefractionation column condenser duty, resulting in a less irreversible heat exchanging process.

Three combined pretreatments for reactive gasification feedstock from wet coffee grounds waste

Abstract In this study, a new pretreatment for using wet food biomass waste as a high calorific and reactive feedstock for gasification is presented. The method involves the addition of calcium hydroxide, hot water treatment, and dewatering in vegetable oil. Hot water treatment at 230°C reduced the oxygen/carbon atomic ratio of coffee grounds waste to improve the calorific value, but this treatment also formed an inactive cross-linked structure caused by dehydration reactions. By mixing the coffee grounds waste with calcium hydroxide powder before the hot water treatment, cross-linking was suppressed and the gasification rate of the char significantly increased because of the catalytic effect. With or without hot water treatment, the time required to complete gasification for the chars of the grounds mixed with calcium hydroxide was reduced to about one-third of that for the char of the untreated grounds. After heating in vegetable oil at 150°C, moisture was completely removed from the coffee grounds and they became impregnated with a large amount of the oil. As dewatering in oil did not affect the gasification rate of the chars, a combination of these three treatments was found to efficiently convert wet food biomass waste into a gasification feedstock.

Influence of current modulation waveform on polycrystalline diamond film deposition using modulated induction thermal plasmas—numerical and experimental studies

In this paper, the influence of amplitude-modulated coil current waveform on polycrystalline diamond deposition was studied using modulated induction thermal plasma (M-ITP) with numerical and experimental approaches. The M-ITP is useful in undertaking the nucleation of diamond particles necessary for the first stage of diamond film deposition. First, numerical thermo-fluid calculations were conducted for Ar M-ITP with CH4/H2 feedstock gas to investigate the influence of a modulation waveform on particle fluxes of different hydrocarbon species onto a Si substrate. Furthermore, experiments were performed to fabricate polycrystalline diamond film deposition using M-ITP with different modulation waveforms. The modulation waveform for the coil current was set as a rectangular waveform, a saw-tooth waveform and a reverse saw-tooth waveform in the calculations and the experiments. The experimental results showed that the saw-tooth M-ITP provided a higher deposition rate, of 2.05 µm h−1, than other waveforms. This could be attributed to the higher fluxes of neutral hydrocarbons in the saw-tooth M-ITP according to the calculation results.

Investigation on the yield of producer gas from tamarind shell (Tamarindus Indica) as feedstock in an Imbert type biomass gasifier

Thermochemical gasification technology is given priority in recent years to meet the needs of decentralized power generation, and also to develop alternative energy sources for conventional thermal applications. The continuous operation of a gasifier becomes a challenge when there is scarcity for specific type of biomass in a particular region. To overcome this challenge and to establish gasification technology in rural areas, the suitability of gasifier in making use of commonly available biomasses in a region must be confirmed. Tamarind tree is common in many countries and the shell of its fruit can be a promising feedstock for a gasifier. Therefore, yield and CV of the producer gas during the thermochemical conversion of TS, in an Imbert-type gasifier are studied in this paper. The performance parameters are analysed to check whether the values are in accordance with the specifications of the gasifier. In this study, Species-transport CFD model is used to forecast the reliability of a gasifier, and an experimental study is also conducted to confirm the predictions and to identify operational issues. The result shows that the best equivalence ratio is 0.30. At this condition, the average CV and yield of producer gas are 5.76 MJ/Nm3 and 1.95 Nm3/kg. Moreover, the CO2/CO ratio and the conversion efficiency are 0.69 and 78.23% respectively. The coherence of the predicted values with the specifications of the gasifier, and also the observations noted during experimentation, confirms that TS could be an appropriate feedstock for the tested gasifier.

Transcriptome and translatome of CO2 fixing acetogens under heterotrophic and autotrophic conditions

Acetogens are anaerobic bacteria that utilise gaseous feedstocks such as carbon monoxide (CO) and carbon dioxide (CO2) to synthesise biomass and various metabolites via the energetically efficient Wood-Ljungdahl pathway. Because of this pathway, acetogens have been considered as a novel platform to produce biochemicals from gaseous feedstocks, potentially replacing the conventional thermochemical processes. Despite their advantages, a lack of systematic understanding of the transcriptional and translational regulation in acetogens during autotrophic growth limits the rational strain design to produce the desired products. To overcome this problem, we presented RNA sequencing and ribosome profiling data of four acetogens cultivated under heterotrophic and autotrophic conditions, providing data on genome-scale transcriptional and translational responses of acetogens during CO2 fixation. These data facilitate the discovery of regulatory elements embedded in their genomes, which could be utilised to engineer strains to achieve better growth and productivity. We anticipate that these data will expand our understanding of the processes of CO2 fixation and will help in the designing of strains for the desired biochemical production.

Energy, exergy, and environmental analyses of renewable hydrogen production through plasma gasification of microalgal biomass

In this study, an energy, exergy, and environmental (3E) analyses of a plasma-assisted hydrogen production process from microalgae is investigated. Four different microalgal biomass fuels, namely, raw microalgae (RM) and three torrefied microalgal fuels (TM200, TM250, and TM300), are used as the feedstock for steam plasma gasification to generate syngas and hydrogen. The effects of steam-to-biomass (S/B) ratio on the syngas and hydrogen yields, and energy and exergy efficiencies of plasma gasification (ηEn,PG, ηEx,PG) and hydrogen production (ηEn,H2, ηEx,H2) are taken into account. Results show that the optimal S/B ratios of RM, TM200, TM250, and TM300 are 0.354, 0.443, 0.593, and 0.760 respectively, occurring at the carbon boundary points (CBPs), where the maximum values of ηEn,PG, ηEx,PG, ηEn,H2, and ηEx,H2 are also achieved. At CBPs, torrefied microalgae as feedstock lower the ηEn,PG, ηEx,PG, ηEn,H2, and ηEx,H2 because of their improved calorific value after undergoing torrefaction, and the increased plasma energy demand compared to the RM. However, beyond CBPs the torrefied feedstock displays better performance. A comparative life cycle analysis indicates that TM300 exhibits the highest greenhouse gases (GHG) emissions and the lowest net energy ratio (NER), due to the indirect emissions associated with electricity consumption.

Syngas-fueled solid oxide fuel cell functionality improvement through appropriate feedstock selection and multi-criteria optimization using Air/O2-enriched-air gasification agents

An optimum carbonaceous feedstock is determined for a syngas fueled solid oxide fuel cell (SOFC) for enhanced performance and reduced levelized cost and CO2 emissions. Four configurations are investigated: simple SOFC, and SOFC with the anode and/or cathode gas recycling. The effect of enriching the gasification medium with oxygen is also investigated. Thermodynamics, economic and environmental aspects of the systems are then comprehensively compared. Finally, multi-criteria particle swarm optimization is employed considering various anode and cathode recycling ratios, and feedstock compositions. The results indicate that optimum values of local power output, and levelized cost and emissions are observed at higher current densities and fuel utilization factors. The SOFC with anode and cathode recycling performs better in almost all conditions. The results further indicate that enriching the gasification medium with oxygen can greatly improve system performance while increasing the levelized cost of products. The optimization results show that exergy efficiency, levelized cost of products, and levelized emissions respectively are 43.7%, 47.2 $/MWh, and 0.530 t/MWh, for a syngas fueled SOFC using air, and 44.2%, 67.9 $/MWh, and 0.481 t/MWh, for a syngas fueled SOFC using O2-enriched air. An appropriate feedstock for a syngas fueled SOFC with anode and cathode gas recycling is CH2.315O0.027 with 77.2 wt% carbon, 15.0 wt% hydrogen, and 2.8 wt% oxygen to achieve a well-balanced condition between exergetic, economic, and environmental indicators. In general, anode and cathode gas recycling and feedstock composition are observed to be influential parameters on the performance of SOFCs.

Devolatilization of Residual Biomasses for Chemical Looping Gasification in Fluidized Beds Made Up of Oxygen-Carriers

The chemical looping gasification of residual biomasses—operated in fluidized beds composed of oxygen-carriers—may allow the production of biofuels from syngas. This biomass-to-fuel chain can contribute to mitigate climate change, avoiding the accumulation of greenhouse gases in our atmosphere. The ongoing European research project Horizon2020 CLARA (G.A. 817841) investigates wheat-straw-pellets (WSP) and raw-pine-forest-residue (RPR) pellets as feedstocks for chemical looping gasification. This work presents experimental results from devolatilizations of WSP and RPR, in bubbling beds made of three different oxygen-carriers or sand (inert reference), at 700, 800, 900 °C. Devolatilization is a key step of gasification, influencing syngas quality and quantity. Tests were performed at laboratory-scale, by a quartz reactor (fluidizing agent: N2). For each pellet, collected data allowed the quantification of released gases (H2, CO, CO2, CH4, hydrocarbons) and mass balances, to obtain gas yield (ηav), carbon conversion (χavC), H2/CO ratio (λav) and syngas composition. A simplified single-first order-reaction model was adopted to kinetically analyze experimental data. WSP performed as RPR; this is a good indication, considering that RPR is similar to commercial pellets. Temperature is the dominating parameter: at 900 °C, the highest quality and quantity of syngas was obtained (WSP: ηav = 0.035–0.042 molgas gbiomass−1, χavC = 73–83%, λav = 0.8–1.0); RPR: ηav = 0.036–0.041 molgas gbiomass−1, χavC = 67–71%, λav = 0.9–1.0), and oxygen-carries generally performed better than sand. The kinetic analysis suggested that the oxygen-carrier ilmenite ensured the fastest conversion of C and H atoms into gases, at tested conditions.

Spent mushroom substrate performance for pyrolysis, steam co-gasification, and ash melting

Spent mushroom substrate is expected to be utilised as gasification feedstock in the future. This study investigated its performance in pyrolysis, steam co-gasification, and ash melting. During pyrolysis, derivative thermogravimetry showed shoulder curves indicating higher hemicellulose content compared with timber waste. Steam co-gasification was evaluated using a laboratory-scaled fixed-bed downdraft gasifier. The results showed that blending the substrate with Erianthus at a blend rate of 50 wt% enhances carbon conversion to gas and hydrogen by 7.5–8.8% points, with lower H2S yield due to the formation of CaSO4 on the biomass surface. Furthermore, blending the substrate with Japanese cedar resulted in increased softening and fusion temperature, which is explained by the formation of calcium minerals (e.g., gehlenite and albite–calcian). Based on these results, spent mushroom substrate demonstrates high potential to serve as regional feedstock by co-gasification.

Coal macerals and their separation methodologies – A review

Macerals are microscopically recognizable organic entities found in coal. On the basis of their optical properties they are classified into three categories, liptinite, vitrinite, and inertinite. Reactive macerals, Vitrinite and liptinite, are responsible for the thermoplastic nature of coal during coke formation. It is also found that these macerals can be used for making some high valued products such as carbon fiber, BTX, liquefaction and gasification feedstock. There are various methods applied by different researchers for coal maceral separation method. This review aims to discuss the various properties of coal macerals and the different methodologies adopted for their separation.

Enhancing environmental sustainability through waste to energy conversion of neem leaves

Biomass is a viable alternative to reduced coal and fossil fuels as a clean energy source. This study focuses on the feasibility of using waste neem leaves as the feedstock for downdraft gasifier. The moisture content, volatile matter, fixed carbon, and ash content of waste neem leaves were determined as 12.1%, 60.58%, 9.31% and 18% respectively. The elemental composition of biomass was determined as carbon 41.99%, hydrogen 6.265%, nitrogen 2.823%, sulphur 0.311%, and oxygen 48.611% respectively. The higher heating values of waste neem leaves is 16.85 MJ/kg, which is better than rice husk and coal.