Gasification of Organic Waste:Parameters,Mechanism and Prediction with the Machine Learning Approach

Gasification of organic waste represents one of the most effective valorization pathways for renewable energy and resources recovery,while this process can be affected by multi-factors like temperature,feedstock,and steam content,making the product’s prediction problematic.With the popularization and promotion of artificial intelligence such as machine learning(ML),traditional artificial neural networks have been paid more attention by researchers from the data science field,which provides scientific and engineering communities with flexible and rapid prediction frameworks in the field of organic waste gasification.In this work,critical parameters including temperature,steam ratio,and feedstock during gasification of organic waste were reviewed in three scenarios including steam gasification,air gasification,and oxygen-riched gasification,and the product distribution and involved mechanism were elaborated.Moreover,we presented the details of ML methods like regression analysis,artificial neural networks,decision trees,and related methods,which are expected to revolutionize data analysis and modeling of the gasification of organic waste.Typical outputs including the syngas yield,composition,and HHVs were discussed with a better understanding of the gasification process and ML application.This review focused on the combination of gasification and ML,and it is of immediate significance for the resource and energy utilization of organic waste.

Synergistic Treatment of Low-concentration Organic Waste Gas by Micro-nano Bubble Coordinated with Peroxymonosulfate

Continuous dynamic experiment was conducted for the treatment of low-concentration organic waste gas with xylene as a representative, using micro-nano bubble and peroxymonosulfate working in synergy. The degradation rule of xylene under different conditions such as the ORP value of the spray liquid, pH value of the spray liquid, liquid-gas ratio of the spray liquid, residence time of xylene, and initial concentration of xylene was investigated. The results showed that at a low concentration, the pH value of the spray liquid had little effect on the degradation rate of xylene. The degradation rate of xylene rose with the increase of the ORP value of the spray liquid, the liquid-gas ratio of the spray liquid, the residence time of xylene, and the initial concentration of xylene.

Screening on oil-decomposing microorganisms and application in organic waste treatment machine

As an oil-decomposable mixture of two bacteria strains(Bacillus sp. and Pseudomonas sp.), Y3 was isolated after 50 d domestication under the condition that oil was used as the limited carbon source. The decomposing rate by Y3 was higher than that by each separate individual strain, indicating a synergistic effect of the two bacteria. Under the conditions that T=25—40℃,pH=6—8, HRT(Hydraulic retention time)=36 h and the oil concentration at 0.1%, Y3 yielded the highest decomposing rate of 95.7 %. Y3 was also applied in an organic waste treatment machine and a certain rate of activated bacteria was put into the stuffing. A series of tests including humidity, pH, temperature, C/N rate and oil percentage of the stuffing were carried out to check the efficacy of oil-decomposition. Results showed that the oil content of the stuffing with inoculums was only half of that of the control. Furthermore, the bacteria were also beneficial to maintain the stability of the machine operating. Therefore, the bacteria mixture as well as the machines in this study could be very useful for waste treatment.

Conversion of organic carbon in the decomposable organic wastes in anaerobic lysimeters under different temperatures

The quantitative fractions of conversion of organic carbon in the decomposable organic wastes with initial moisture of 70% sorted from municipal solid wastes(MSW) in lysimeters into biogas, leachate and solid residue were characterized, under temperatures of 25, 30 and 41℃, respectively, and circulation of leachate generated within the lysimeters. It is found that 27% of organic carbon in the wastes are conversed into gases, 0.8% into leachate, and the other 72% remained in the decomposable solid residues, after 180 days' degradation at 41℃. Higher temperature will lead to more rapid degradation and result to higher conversion of the organic carbon to biogas and lower to both solid residues and leachate, while the pollutant concentrations in leachate will be lower at a higher temperature and the values of COD are quite consistent with TOC.

Biocompatible Blends Based on Poly(Vinyl Alcohol)and Solid Organic Waste

This work is aimed at the development of new green composite materials through the incorporation of the solid organic waste(SOW)in a thermoplastic matrix.After being ground,the organic waste was exposed to a sterilization process,though an autoclave cycle,in order to obtain a complete removal of the bacterial activity.The SOW was found to have a high amount of water,about 65-70%,which made uneconomical its further treatment to reduce the water amount.Therefore,a water soluble polymer,poly(vinyl alcohol)(PVA)was chosen in order to produce SOW based blends.However,in order to reduce the viscosity of the PVA/SOW slurry,further amount of water was added.The very low viscosity attained by the water suspension allowed to process the PVA/SOW blends by a pressure-free process,for the production of samples,which were afterwards subjected to physical and mechanical characterization.Flexural tests showed the promising properties of the developed blends.In particular,the relevance of porosity was assessed.Increasing the water amount involved a signification increase of porosity,due to a faster water evaporation during processing.On the other hand,compared to neat PVA,addition of SOW allowed to significantly decrease the porosity of the produced samples.Despite this,the mechanical properties of the PVA/SOW blends were shown to be lower than those of neat PVA processed analogously.

Pilot-test about Treatment of Low-concentration Organic Waste Gas Using a Fixed Biological Bed

[ Objective] The study aims to discuss the feasibility of using a fixed biological bed to treat low-concentration organic waste gas. [ Method] A fixed biological bed was used to treat low-concentration organic waste gas from a phosphate workshop, and then the waste gas treated was assessed by human sense of smell to determine the most economical empty bed contact time, thereby verifying the feasibility of using a fixed biolog- ical bed to treat low-concentration organic waste gas. [Result] When empty bed contact time was 60 s, the smell of the treated waste gas was acceptable, and COD value of recycled water in the fixed biological bed was essentially unchanged. It proved that organic load of the waste gas was consumed by microorganisms within 60 s. [ Conclusion] It is feasible to use a fixed biological bed to treat Iow-concantration organic waste gas from a phosphate workshop.

Recovery of Organic Waste with Other Biological Components for the Production of Organic Fertilizer: Improved Biochar

The study was carried out in Baham district in the West Cameroon region, as part of the recovery of organic waste with other biological components for the manufacture of an organic fertilizer (improved biochar). Through observations and a survey questionnairy submitted to 100 farmers, it appears that the majority use synthetic chemical fertilizers. Farmers using chemical fertilizers find them dangerous to their health. In addition, 58.57% of these farmers said they felt unwell after spreading these fertilizers. However, 64.28% of these farmers do not acquire PPE for reasons of financial means on the one hand and ignorance on the other hand. 54.28% of respondents using only chemical fertilizers noted declining agricultural production. The surveys also reveal that biochar (of plant origin) as a solution proposed by CIPCRE is used by a minority of farmers (21%) in the said locality on the one hand and on the other hand has limits in terms of intake nutrients for crops;this was confirmed by analyzes of the physico-chemical parameters.

Potential of organic waste to energy and bio-fertilizer production in Sub-Saharan Africa:a review

Many growing cities of Sub-Saharan Africa(SSA)are marred by the inefficient collection,management,disposal and reuse of organic waste.The purpose of this study was to review and compare the energy recovery potential as well as bio-fertilizer perspective,from the organic waste volumes generated in SSA countries.Based on computations made with a literature review,we find that the amount of organic wastes varies across countries translating to differences in the energy and bio-fertilizer production potentials across countries.Organic wastes generated in SSA can potentially generate about 133 million GWh of energy per year.The organic waste to bio-fertilizer production potentials range from 11.08 million tons to 306.26 million tons annually.Ghana has the highest energy and bio-fertilizer potential among the SSA countries with a total per capita of 630 MWh/year and 306.26 million tons,respectively.The challenges and technical considerations for energy and bio-fertilizer approaches in the management of organic waste in SSA have also been discussed.This study is of help to the readers and strategic decision makers in understanding the contribution of bioenergy and bio-fertilizer to achieving sustainable development goals,namely,7(Affordable and Clean Energy)and 13(Climate Action)in SSA.

Influence of Stand-Alone Vertical Gas Vents on Aeration and Denitrification of Organic Municipal Waste Assessed by Two-Dimensional (2D) Lysimeters

Landfilled organic waste, in the presence of oxygen, can undergo aerobic decomposition facilitated by heterotrophic microorganisms. Aerobic degradation of solid waste can quickly consume available oxygen thus curtailing further degradation. The aim of this study was the investigation of a low-cost method of replenishing oxygen consumed in landfilled waste. Three 2D lysimeters were established to investigate the effectiveness of stand-alone, vertical ventilation pipes inserted into waste masses. Two different configurations of ventilation were tested with the third lysimeter acting as an unventilated control. Lysimeters were left uninsulated and observed over the course of 6 months with regular collection of gas and leachate samples. Lysimeters were then simulated for Oxygen (O2) and Nitrous oxide (N2O) to analyze the denitrification contributions of each. The experiment revealed that a single ventilation pipe can increase the mean oxygen level of a 1.7 m × 1.0 m area by up to 13.5%. It also identified that while increasing the density of ventilation pipes led to increased O2 levels, this increase was not significant at the 0.05 probability level. A single vent averaged 13.67% O2 while inclusion of an additional vent in the same area only increased the average to 14.59%, a 6.7% increase. Simulation helped to verify that lower ventilation pipe placement density may be more efficient as in addition to the effect on oxygenation, denitrification efficiency may increase. Simulations of N2O production estimated between 8% - 20% more N2O being generated with lower venting density configurations.

Spatio-Temporal Characteristics of Heat Transfer of Methanation in Fluidized Bed for Pyrolysis and Gasification Syngas of Organic Solid Waste

Methanation is an effective way to efficiently utilize product gas generated from the pyrolysis and gasification of organic solid wastes.To deeply study the heat transfer and mass transfer mechanisms in the reactor,a successful three-dimensional comprehensive model has been established.Multiphase flow behavior and heat transfer mechanisms were investigated under reference working conditions.Temperature is determined by the heat release of the reaction and the heat transfer of the gas-solid flow.The maximum temperature can reach 951 K where the catalyst gathers.In the simulation,changes in the gas inlet velocity and catalyst flow rate were made to explore their effects on CO conversion rate and temperature for optimization purposes.As the inlet gas velocity increases from 2.78 to 4.79 m/s,the CO conversion rate decreases from 81.6%to 72.4%.However,more heat is removed from the reactor,and the temperature rise increases from 78.03 to 113.49 K.When the catalyst flow rate is increased from 7.18 to 17.96 kg/(m^(2)·s),the mass of the catalyst in the reactor is increased from 0.0019 to 0.0042 kg,and the CO conversion rate is increased from 66.8%to 81.5%.However,this increases the maximum temperature in the reactor from 940.0 to 966.4 K.

Effect of organic wastes on the plant-microbe remediation for removal of aged PAHs in soils

The effectiveness of in-situ bioremediation of polycyclic aromatic hydrocarbons （PAHs） may be inhibited by low nutrients and organic carbon. To evaluate the effect of organic wastes on the PAHs removal efficiency of a plant-microbe remediation system, contaminated agricultural soils were amended with different dosages of sewage sludge （SS） and cattle manure （CM） in the presence of alfalfa （Medicago sativa L.） and PAHs-degraders （Bacillus sp. and Flavobacterium sp.）. The results indicated that the alfalfa mean biomasses varied from 0.56 to 2.23 g/pot in root dry weight and from 1.80 to 4.88 g/pot in shoot dry weight. Low dose amendments, with rates of SS at 0.1% and CM at 1%, had prominent effects on plant growth and soil PAHs degradation. After 60-day incubation, compared with about 5.6% in the control, 25.8% PAHs removal was observed for treatments in the presence of alfalfa and PAHs-degraders; furthermore, when amended with different dosages of SS and CM, the removed PAHs from soils increased by 35.5%--44.9% and 25.5%-42.3%, respectively. In particular, the degradation of high-molecular-weight PAHs was up to 42.4%. Dehydrogenase activities （DH） ranged between 0.41 and 1.83 ~tg triphenylformazan/（g dry soil.hr） and the numbers of PAHs-degrading microbes （PDM） ranged from 1.14x106 to 16.6x106 most-probable-number/g dry soil. Further investigation of the underlying microbial mechanism revealed that both DH and PDM were stimulated by the addition of organic wastes and significantly correlated with the removal ratio of PAHs. In conclusion, the effect of organic waste application on soil PAHs removal to a great extent is dependent on the interactional effect of nutrients and dissolved organic matter in organic waste and soil microorganisms.

A pilot field-scale study on biotrickling filter treatment of NH_3-containing odorous gases from organic waste composting plants

The use of a biotrickling filter was investigated for a pilot field-scale elimination of NH3 gas and other odorous gases from a composting plant in Tongzhou District, Beijing. The inlet gas flow rate was 3500 m3/h and NH3 concentration fluctuated between 2.76–27.84 mg/m3, while the average outlet concentration was 1.06 mg/m3 with an average of 94.9% removal. Critical volumetric loading (removal efficiency=100%) was 11.22 g-N/(m3·h). The odor concentration removal was 86.7%. NH3 removal efficiency decreased as the free ammonia (FA) in the trickling liquid increased. The pressure drop was maintained at about 50 Pa/m and was never more than 55 Pa/m. During the experiment, there was neither backflushing required nor any indication of clogging. Overall, the biotrickling filter was highly efficient and cost-effective for the simultaneous biodegradation of NH3 and other odorous gases from composting, suggesting the possibility of treating odorous gases at the industrial level.

Developing“precise-acting”strategies for improving anaerobic methanogenesis of organic waste:Insights from the electron transfer system of syntrophic partners

Methanogenesis is the last step in anaerobic digestion,which is usually a rate-limiting step in the biological treatment of organic waste.The low methanogenesis efficiency(low methane production rate,low methane yield,low methane content)substantially limits the development of anaerobic digestion technology.Traditional pretreatment methods and bio-stimulation strategies have impacts on the entire anaerobic system and cannot directly enhance methanogenesis in a targeted manner,which was defined as“broad-acting”strategies in this perspective.Further,we discussed our opinion of methanogenesis process with insights from the electron transfer system of syntrophic partners and provided potential targeted enhancing strategy for high-efficiency electron transfer system.These“precise-acting”strategies are expected to achieve an efficient methanogenesis process and enhance the bio-energy recovery of organic waste.

Region-gridding recycling of bulk organic waste: Emerging views based on coordinated urban and rural development

Bulk organic waste(BOW)has a large outputin China.The improper disposal of BOW will not onlybring serious environmental pollution,but also cause wasteof biomass resources.The viewpoint proposes a region-gridding recycling management system of BOW thathighlights the coordinated development of environmental,agricultural and energy elements in urban and rural areas.The viewpoint aims to drive the upstream and downstreamindustrial chains of BOW treatments,avoid the repeatedconstruction of resource facilities,guide the upgrading ofresource-based technologies,promote the professionaliza-tion of farmers,and thus built the high-quality modernagricultural recycling industrial park based on systemmanagement.

Comparative effects of composted organic waste and inorganic fertilizer on nitrate leachate from the farm soils of northern Guam

The purpose of this study was to quantify the release of nitrate into vadose zone as well as the nitrogen-holding capacity of compost applied on calcareous soils of northern Guam amended with both inorganic fertilizer and composted organic waste,to examine potentially adverse effect of these nutrient materials to groundwater quality.Three different nitrogen levels each of the composted organic waste and the inorganic fertilizer were applied to corn(maize)(farmland)study plots for three consecutive seasons,two dry and one rainy season.During each season,soil organic matter(SOM,w/w%)content and carbon-nitrogen ratio(C/N,w/w%),were determined for analysis of the nitrogen-holding capacity of these calcareous soils.Nitrate levels in soil pore water were also determined for study of potential groundwater contamination.For three seasons,compost plots showed higher SOM%contents and lower C/N%than fertilizer plots.That is,compost-treated soils showed higher SOM content and adsorbed more nitrogen under normalized soil mass than did fertilizer-treated soils.Nitrate levels in pore water were generally higher on compost plots during early stages of corn but were generally higher on fertilizer plots during active leaf,tasseling,and maturity stages.During the rainy season,nitrate leachate seemed to increase,but this trend could not be confirmed because rainfall amounts were not measured.Overall,composted organic waste proved to be a good amendment for soil productivity and agricultural sustainability while reducing nitrate leachate from northern Guam farmland.

Study on the resource utilization of high fluorine-containing organic waste through fluidized incineration

In this study,the method of fluidized incineration and water washing to recover hydrogen fluoride(HF)was proposed to dispose of high fluorine-containing organic waste.The resource utilization of the waste was investigated in a fluidized bed incinerator with a disposal capability of 10 t/d.The evolution characteristics of fluorine,operation conditions of the incineration system,absorption coefficient for HF by water washing,and HF corrosion during combustion were assessed.The results showed that HF and fluorocarbons were detected as the initial gaseous fluorides released during combustion.The release of HF could be divided into three stages,in which HF was generated from the volatilization of HF in the waste and the hydrolysis of fluorine in water-soluble salts(60–220℃),oxidative decomposition of fluorinated organic components and residual carbon(220–800℃),and hydrolysis of insoluble fluorinated inorganic minerals(800–1000℃).Fluorocarbons could be destroyed through reactions with free radicals H,O,and OH or through single-molecule decomposition.Enhancing the temperature in the furnace and increasing the content of oxygen and hydrogen in the incineration materials were conducive to reducing the generation of fluorocarbons.By sampling and analyzing the bottom slag,bag filter ash and exhaust gas during the field test,the relevant pollutant discharge could meet the national emission standards.The waste heat utilization of high-temperature flue gas and the recovery of hydrofluoric acid and hydrochloric acid were realized.In the recovery of HF by water washing,the total absorption coefficients for 1#to 4#packed absorbers were 52.38 kg/(h m^(2)),39.96 kg/(h m^(2)),5.98 kg/(h m^(2))and 3.89 kg/(h m^(2)),respectively.In the actual operation,alumina showed good corrosion resistance to high-temperature HF and could be used as bed materials or refractory materials.Low-temperature corrosion of HF occurred in the quenching heat exchanger,which was damaged after 6 months of continuous operation.High-temperature corrosion of HF occurred in the waste heat boiler.No significant corrosion was observed in the 24 months of operation.

Assessment of Municipal Organic Solid Waste, as a Potential Feedstock for Briquette Production in Kampala, Uganda

The current shortage of energy resources coupled with environmental degradation problems resulting from deforestation in Uganda has contributed to increased demand for renewable energy resources including municipal organic solid waste and agricultural residues. However, organic waste from Municipal Solid Waste (MSW) may contain contaminants that are harmful to public health and the environment. This study determined the heavy metal concentration in MSW in Kampala City, Uganda. Also, the physicochemical properties of briquettes produced from the MSW were compared with charcoal. The waste samples were collected from residential, institutional and market areas over a period of two weeks. They were then analyzed for the presence of heavy metals. Briquettes were made from the bio-waste and were subjected to calorific and proximate analysis. Results indicated that the mean concentrations of Cd, Cr, Cu, Fe, and Pb were 1.25 mg/kg, 2.04 mg/kg, 38.2 mg/kg, 3.97 mg/kg and 1.99 mg/kg respectively while Hg was not detected. The calorific values of briquettes ranged from 8.9 to 15.3 MJ/kg and were lower than those of charcoal. Heavy metal concentrations in bio-waste collected were below the permissible acceptable limits. These findings indicate that the sampled MSW does not pose a health hazard arising from the presence of such heavy metals and therefore could be a safe source of renewable energy.

Assessment of the Solid Waste Disposal Method during COVID-19 Period Using the ELECTRE Ⅲ Method in an Interval-Valued q-Rung Orthopair Fuzzy Approach

As the quantity of garbage created every day rises,solid waste management has become the world’s most important issue.As a result,improper solid waste disposal and major sanitary issues develop,which are only detected after they have become dangerous.Due to the system’s lockdown during the COVID-19 pandemic,this scenario became much more uncertain.We are at the stage to develop and execute effective waste management procedures,as well as long-term policies and forward-thinking programmes that can work even in the most adverse of scenarios.We incorporate major solid waste(organic and inorganic solid wastes)approaches that actually perform well in normal cases by reducing waste and environmental disasters;however,in such an uncertain scenario like the COVID-19 pandemic,the project automatically allows for a larger number of criteria,all of which are dealt with using fuzzy Multi-Criteria Group Decision Making(MCGDM)methods.The ELECTRE Ⅲ(ELimination Et Choice Translating REality-Ⅲ)approach,which is a novel decision-making strategy for determining the best way to dispose and reduce garbage by combining traditional ELECTRE Ⅲ with an interval-valued q-rung orthopair fuzzy set(IVq-ROFS),is described in detail in this article.To confirm the efficacy of the recommended model,a numerical explanation is provided,as well as sensitivity and comparative analyses.Obviously,the findings encourage decision-makers in authorities to deliberate about the proposals before creating solid waste management policies.

Study on the Recovery of Rhodium from Spent Organic Rhodium Catalysts of Acetic Acid Industry Using Pyrometallurgical Process

A new process recycling rhodium from organic waste containing rhodium in acetic acid industry is developed. Use the special affinity of base metal sulfides (FeS, Ni2S3 , CuS, etc.) on platinum group metals, adopting high nickel matte trapping-aluminothermic activation method to recovery rhodium from incinerator residue of organic rhodium waste. The method is shorter process, lower equipment requirement, and the higher activity of rhodium black. In pyrometallurgy enrichment process,the recovery rate of rhodium reached 94.65%, the full flow of rhodium recovery rate was 92.04%.