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.

Stable Control of Influence Factor during Two-phase Anaerobic Digestion for Agricultural Organic Waste

Two-phase anaerobic digestion process is influenced by acid control for hydrogen production, reaction temperature, substrate detention time, sludge activity, and granular formation. Al of these technological parameters are directly related to success or failure of the system operation and treatment effect.

Research Advances in Agricultural Reutilization of Urban-rural Organic Wastes

The author summarized the advantages and potential risks of urban-rural organic wastes agricultural reutilization to reduce the potential risks of urban-rural organic wastes agricultural utilization. The results showed that： the organic wastes generated in urban-rural life as fertilizer applied into farmland made an impact on soil properties, then indirectly affected the soil microbial biomass and soil enzymes activities. In addition, the heavy metals in organic wastes would accumulate in the soil and damage to soil environment. Therefore, it was necessary to make a long- term research on the environment of soil which agricultural utilized of wastes.

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.

Separation-and-Recovery Technology for Organic Waste Liquid with a High Concentration of Inorganic Particles

The environmentally friendly and resourceful utilization of organic waste liquid is one of the frontiers of environmental engineering. With the increasing demand for chemicals, the problem of organic waste liq- uid with a high concentration of inorganic pollutants in the processing of petroleum, coal, and natural gas is becoming more serious. In this study, the high-speed self-rotation and flipping of particles in a three- dimensional cyclonic turbulent field was examined using a synchronous high-speed camera technique; the self-rotation speed was found to reach 2000-6000 rad.s 1. Based on these findings, a cyclonic gas- stripping method for the removal of organic matter from the pores of particles was invented. A techno- logical process was developed to recover organic matter from waste liquid by cyclonic gas stripping and classifying inorganic particles by means of airflow acceleration classification. A demonstration device was built in Sinopec＇s first ebullated-bed hydro-treatment unit for residual oil. Compared with the T-STAR fixed-bed gas-stripping technology designed in the United States, the maximum liquid-removal effi- ciency of the catalyst particles in this new process is 44.9% greater at the same temperature, and the time required to realize 95% liquid-removal efficiency is decreased from 1956.5 to 8.4 s. In addition, we achieved the classification and reuse of the catalyst particles contained in waste liquid according to their activity. A proposal to use this new technology was put forward regarding the control of organic waste liquid and the classification recovery of inorganic particles in an ebullated-bed hydro-treatment process for residual oil with a processing capacity of 2×106 t.a^1. It is estimated that the use of this new tech- nology will lead to the recovery of 3100 t.a 1 of diesel fuel and 647 t.a^1 of high-activity catalyst; in addi- tion, it will reduce the consumption of fresh catalyst by 518 t.a^1. The direct economic benefits of this process will be as high as 37.28 million CNY per year.

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.

Biogas Production from Organic Wastes to Promote Satisfying EU Requirements

Producing of renewable energy--as well in world as in national context--was necessitated by the synergistic effect of the climate change and the long term, continuous price rise of the fossil energy carriers. Main reasons for the spread of renewable energy sources are to increase the security of the energy supply or in optimal case, to realize the total energy independence. Furthermore, numerous studies demonstrate that production and also utilization of biofuels--including the organic waste-based fuels--are environmentally sustainable and have positive impact for the security of energy supply. This paper deals with production of biogas （from agricultural organic wastes） for energy. The production of biogas and the other biofuels will help you find the balance in agriculture because they can be generated from biomass, agricultural wastes and non-food plant material. In addition to the objective of saving emissions, EU biofuels policy aims to ensure the necessary energy and to decrease unemployment. So this paper would like to contribute to the EU requirements through the research. The producing system can be expansible by utilization of other organic material, so it is supported the efficient operation.

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.

Utilization and management of organic wastes in Chinese agriculture:Past,present and perspectives

Recycling and composting of organic materials such as animal waste, crop residues and green manures has a long tradition in China. In the past, the application of organic manures guaranteed a high return of organic materials and plant mineral nutrients and thus maintained soil fertility and crop yield. As a result of rapid economic development coupled with the increasing urbanization and labour costs, the recycling rate of organic materials in Chinese agriculture has dramatically declined during the last two decades, in particular in the more developed eastern and southeastern provinces of China. Improper handling and storage of the organic wastes is causing severe air and water pollution. Because farmers are using increasing amounts of mineral fertilizer, only 47% of the cropland is still receiving organic manure, which accounted for 18% of N, 28% of P and 75% of K in the total nutrient input in 2000. Nowadays, the average proportion of nutrients (N+P+K) supplemented by organic manure in Chinese cropland is only 35% of the total amount of nutrients from both inorganic and organic sources. In China, one of the major causes is the increasing de-coupling of animal and plant production. This is occurring at a time when 're-coupling' is partly being considered in Western countries as a means to improve soil fertility and reduce pollution from animal husbandry. Re-coupling of modern animal and plant production is urgently needed in China. A comprehensive plan to develop intensive animal husbandry while taking into account the environmental impact of liquid and gaseous emissions and the nutrient requirements of the crops as well as the organic carbon requirements of the soil are absolutely necessary. As a consequence of a stronger consideration of ecological aspects in agriculture, a range of environmental standards has been issued and various legal initiatives are being taken in China. Their enforcement should be strictly monitored.

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.

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.