Wet Organic Waste Research Articles

Microbial electrolysis treatment of post-hydrothermal liquefaction wastewater with hydrogen generation

Hydrothermal liquefaction (HTL) directly converts wet organic waste into biocrude oil, but it also generates post-HTL wastewater (PHWW) with concentrated nutrients that require further treatment before discharge or reuse. While traditional technologies showed limited success, this study demonstrates that microbial electrolysis cell (MEC) can be an effective approach to treat the swine manure PHWW and recover H2 for onsite HTL biocrude upgrading. The onsite H2 production and utilization makes MEC an ideal wastewater treatment process for HTL operations. Using actual swine manure PHWW, the MEC reactors showed excellent removals of organics (90–98%) and nitrogen (57–93%) under various organic loadings, applied voltages, and flow rates. Increasing organic loadings and applied voltages showed positive influences on system performance, while changes of flow rates showed limited impacts. The highest H2 production rate was 168.01 ± 7.01 mL/L/d with a H2 yield of 5.14 ± 0.22 mmol/kg COD (3000 mg COD/L, 1.0 V), and the highest cathodic H2 recovery and energy efficiency were 74.24 ± 0.11% and 120.56 ± 17.45%, respectively. System configuration and operation can be further optimized to improve system performance.

Disposal of Kitchen Waste from High Rise Apartment

The high rise building has numbers of floor and rooms having variety of users or tenants for residential purposes. The huge quantities of heterogenous mixtures of domestic food waste are generated from every floor of the high rise residential buildings. Disposal of wet and biodegradable domestic kitchen waste from high rise buildings are more expensive in regards of collection and vertical transportation. This work is intended to address the technique to dispose of the wet organic food waste from the high rise buildings or multistory building at generation point with the advantage of gravity and vermicomposting technique. This innovative effort for collection and disposal of wet organic solid waste from high rise apartment is more economical and hygienic in comparison with present system of disposal.

Decentralized Production of Fischer–Tropsch Biocrude via Coprocessing of Woody Biomass and Wet Organic Waste in Entrained Flow Gasification: Techno-Economic Analysis

The present work addresses the techno-economics of the decentralized coproduction of Fischer–Tropsch biocrude and liquefied natural gas via thermochemical conversion of woody biomass and wet organic waste to syngas in an entrained flow gasification reactor. The process design considers thermal pretreatment of the feedstock based on integrated drying of both the woody biomass and the organic waste using direct-contact superheated steam, and torrefaction for the dried wood. The superheated steam required for drying is produced from recovery of residual heat from the main conversion process. The overall cost of biocrude production has been shown to decrease when increasing the fraction of organic waste when considering gate fees for the organic waste, at the production site, above 10$/ton. For gate fees of 50$/ton, which are realistic for the current waste market, the cost of biocrude ranges between 25 and 22$/GJ for plant scales between 150 and 600 MW based on the input feedstock energy to the entrained flo...

Influence of solid content and maximum temperature on the performance of a hydrothermal carbonization reactor

ABSTRACTHydrothermal carbonization is a thermochemical process that converts wet organic matter into a sterile, high-calorific solid material called hydrochar. This technology is considered an interesting option for low- and middle-income urban settings, often lacking adequate services and high fraction of wet organic waste. The aim of this study was to study the influence of the loading rate (total solid content) and the maximum temperature reached on the resulting energy ratio (ER) of the process and the fuel properties of the obtained hydrochar. Ten experiments were carried out with a standardized biowaste-feedstock. Different solid contents (2.54%, 4.93%, 7.44%, 9.45%, 12.83%, 15.2% by weight) and different targeted maximum temperatures (170°C, 180°C, 190°C, 200°C) were tested. Compared to the feedstock, all resulting hydrochars had an increased higher heating value (HHV) (average of 29.2 MJ/kgdb) and carbon content (average of 66.9%db) than the original biowaste (19.3 MJ/kgdb and 46.2%db, respectively). The HHV obtained were similar to those of charcoal (29.6 MJ/kg). Higher solid contents resulted in higher hydrochar yields and carbon efficiencies, whereas higher temperatures resulted in higher carbon content and HHV of the hydrochar. The experiment with the highest solid content (15.2%wt) achieved an ER > 1.

Hydrothermal Oxidation of Fecal Sludge: Experimental Investigations and Kinetic Modeling.

Hydrothermal oxidation (HTO) provides an efficient technique to completely destroy wet organic wastes. In this study, HTO was applied to treat fecal sludge at well-defined experimental conditions. Four different kinetic models were adjusted to the obtained data. Among others, a distributed activation energy model (DAEM) was applied. A total of 33 experiments were carried out in an unstirred batch reactor with pressurized air as the oxidant at temperatures of <470 °C, oxygen-to-fuel equivalence ratios between 0 and 1.9, feed concentrations between 3.9 and 9.8 molTOC L–1 (TOC = total organic carbon), and reaction times between 86 and 1572 s. Decomposition of the fecal sludge was monitored by means of the conversion of TOC to CO2 and CO. In the presence of oxygen, ignition of the reaction was observed around 300 °C, followed by further rapid decomposition of the organic material. The TOC was completely decomposed to CO2 within 25 min at 470 °C and an oxygen-to-fuel equivalence ratio of 1.2. CO was formed as an intermediate product, and no other combustible products were found in the gas. At certain reaction conditions, the formation of unwanted coke and tarlike products occurred. The reaction temperature and oxygen-to-fuel equivalence ratio showed a significant influence on TOC conversion, while the initial TOC concentration did not. Conversion of TOC to CO2 could be well described with a first-order rate law and an activation energy of 39 kJ mol–1.

Bio-oil Production from Food Processing Residues: Improving the Bio-oil Yield and Quality by Aqueous Phase Recycle in Hydrothermal Liquefaction of Blackcurrant (Ribes nigrum L.) Pomace

Hydrothermal liquefaction (HTL) of wet organic waste is a promising technology for producing renewable liquid fuels. However, implementation of the process at commercial scales must overcome several challenges. Efficient management of the contaminated aqueous phase generated after the conversion is necessary to limit water treatment expenses. In this study, we suggest the direct recycling of the aqueous phase at the inlet of the HTL process. The purpose is to evaluate the effect of recycling the process water on the bio-oil recovery and quality. HTL of blackcurrant pomace was performed in a batch autoclave, at a temperature of 310 °C, with a holding time of 10 min, and a dry biomass concentration of 14.5 wt %. The influence of recycling the process water at the inlet of the process was evaluated for five recycle rounds. Recycling the process water has a positive effect on the bio-oil recovery, with the bio-oil yield increasing from 26 wt % to 31 wt % after five recycles. The energy recovery respectively i...

Decentralized utilization of wasted organic material in urban areas: A case study in Hong Kong

Urban areas, characterized as areas with a high population density, generate large amounts of liquid and solid waste streams. Without proper treatment, these waste streams accumulate in the environment of urban areas and may lead to serious environmental problems. Contrarily, waste streams and particularly wasted organic materials contain valuable compounds, which can be biologically and/or chemically converted into products to cover the economic needs of urban areas. In this study, a concept is presented that contributes to treatment and utilization of wasted organic material in a way to (1) avoid environmental problems, (2) exploit its potential and (3) establish a recycling. In this context, technical aspects, such as hydrolysis, waste reduction, integration in urban structures and recycling of wasted organic matter, were discussed. An example of waste utilization is given based on the organic waste stream generated by a common building in Hong Kong with 640 residents. The 640 residents would generate more than 250kg of wet organic waste per day, which can be biologically hydrolyzed using decentralized processes on site. The hydrolysis of 250kg wet organic waste would result in the production of 33kg glucose, 15kg lipids, 0.6kg free amino nitrogen and 0.2kg phosphate, which can be used as nutrients in biotechnological processes or feedstocks in chemical reactions for the production of food, feed, chemicals and materials. Recycling of organic matter is not only a sustainable waste treatment, but contributes to the economy and self-sufficiency of urban areas in resource supply.

MUNICIPAL SOLID WET WASTE MANAGEMENT BY PUBLIC PARTICIPATION

The municipal solid wet waste is an organic fraction that contributes to around 40% of total waste and it is biodegradable. In the present scenario, wet waste is generally mixed with other kinds of waste that is not bio-degradable. The foul smell is generated from the wet waste if not disposed within 24 hrs. This smell creates problem for people exposed to handling and management system. All biological treatment technologies applied to the wet (organic) waste treatment would require segregation of biodegradable and non-bio-degradable components. Once the waste of different categories is mixed it becomes very difficult to segregate them effectively. Many large size plants in the country are constructed to treat biodegradable waste with the objective to recover energy and produce organic manure but its smooth operation faces great challenge of accurate segregation resulting into plant break down and failures irrespective of robust technology. This research paper focuses on unique approach of public participation for segregation at source by deploying micro level biological treatment plants of capacity ranging from 1.0 MT/d to 5 MT/d. With the implementation of above approach and treatment technology, huge efforts that are presently put to segregate the waste will be eliminated. In addition to this, the energy and organic manure as end product obtained from the treatment plant makes it as self-sustainable.

Anaerobic digestion of post-hydrothermal liquefaction wastewater for improved energy efficiency of hydrothermal bioenergy processes.

Hydrothermal liquefaction (HTL) is a promising process for converting wet biomass and organic wastes into bio-crude oil. It also produces an aqueous product referred to as post-hydrothermal liquefaction wastewater (PHWW) containing up to 40% of the original feedstock carbon, which reduces the overall energy efficiency of the HTL process. This study investigated the feasibility of using anaerobic digestion (AD) to treat PHWW, with the aid of activated carbon. Results showed that successful AD occurred at relatively low concentrations of PHWW (≤ 6.7%), producing a biogas yield of 0.5 ml/mg CODremoved, and ∼53% energy recovery efficiency. Higher concentrations of PHWW (≥13.3%) had an inhibitory effect on the AD process, as indicated by delayed, slower, or no biogas production. Activated carbon was shown to effectively mitigate this inhibitory effect by enhancing biogas production and allowing digestion to proceed at higher PHWW concentrations (up to 33.3%), likely due to sequestering toxic organic compounds. The addition of activated carbon also increased the net energy recovery efficiency of AD with a relatively high concentration of PHWW (33.3%), taking into account the energy for producing activated carbon. These results suggest that AD is a feasible approach to treat PHWW, and to improve the energy efficiency of the HTL processes.

Catalytic conversion of waste biomass by hydrothermal treatment

The purpose of the work presented here is the production of liquid biofuels from wet organic waste matter in a continuous one-step catalytic process under hydrothermal conditions. The catalytic reaction of wet organic matter at near-critical water conditions ( T > 300 °C, p > 22.1 MPa) is used to produce a mixture of combustible organics which can be used as liquid biofuel. In order to achieve a good product quality in a continuous one-step process, two catalysts were applied, a homogeneous potassium carbonate catalyst and a heterogeneous ZrO 2 catalyst. In addition, the reaction mixture was recirculated. The continuous flow of concentrated waste biomass feed at low flow rates and recirculation of the hot reaction mixture were the most challenging obstacles to overcome. The scale of the plant (0.1 l reactor volume) allowed for a variation of the feed, reaction temperature, and recirculation rate in order to optimise the process conditions. Still, the product quantity obtained was sufficient to perform a analytical characterisation. The experimental results confirmed the feasibility of the process. Hydrothermal treatment of waste biomass, after dewatering, resulted in a biocrude oil of high calorific value.

Feasibility of increased biogas production from the co-digestion of agricultural, municipal, and agro-industrial wastes in rural communities

In rural communities, such as Olds, Alberta (population 7248) energy may be produced through anaerobic co-digestion of municipal, agricultural, and agro-industrial wastes. An inventory within a 20 km radius of Olds revealed that 291 000 tonnes of wet organic waste are generated annually (96.8% manure) with an electrical potential of 42 GWh (1 GWh = 106 kWh). Analysis of feedlot, hog, dairy and poultry manure, offal, food, grass, and biosolids identified the potential for waste blending to optimize solids content, nutrient balance, and pH level. In laboratory tests, biogas yield increased from 0.382 m3/kg volatile solid (VS) for feedlot manure alone to 0.513, 0.517, and 0.500 m3/kg VS with co-digestion of 30% hog manure, 15% offal, and 30% offal, respectively. Methane content of biogas increased from 75.8% in feedlot manure digestion to 78.8, 79.5, and 80.9% with co-digestion of 30% hog manure, 15% offal, and 30% offal, respectively.

Biogas potential from apple waste

Biogas production can be used to recover energy from wet organic waste such as food industry residues. In this study, residues from apple juice production at the Epleblomsten juice production plant (Norway) are analyzed to determine the biogas potential.A series of batch experiments with different initial feed concentrations (0, 1, 2, 5 and I 0%) of the leachate from the apple residues are carried out to find the total biogas potential and to investigate the composition of the leachate. These experiments were also simulated by the ADM I (Anaerobic digestion model No. I) in Aquasim as a method to estimate the chemical composition of the leachate.&#x0D; According to the batch experimental data together with the simulation results it was estimated that the leachate organic matter consisted mainly of sugar and some organic acids. The estimated concentrations were used in a follow-up study to design and simulate a full scale process. The initial feed concentrations of I and 2% gave high biogas yields, while 5 and I 0% caused an overload and relatively low biogas yields. The biogas production potential was measured as the volume of biogas produced per I L feed consumed. There is no significant relationship between the residue leachate content and the gas compositions. The COD content of the feed was calculated to be about 160 g COD/L.

Nutrient recovery from anaerobically digested organic wastes

Effluents (digestates) resulting from anaerobic digestion of wet organic wastes can berecycled as fertilizers. Separation of such digestates into a wet and a dry fraction is common.The solid fraction is often sold as a soil enhancement product while the liquid fraction isusually discarded as wastewater. A large portion of the digestate nutrients is dissolved as ionsin the liquid. The aim of this study is to establish an efficient way to convert this into a liquid"organic fertilizer". Enhancement of the nutrient concentration is necessary in order to makethe final product commercially acceptable. Direct evaporative concentration is not suitable asit would lead to a significant loss of ammonia due to the fact that most of the availablenitrogen in these digestates is present in the ammonium/ammonia form. Thus stabilizing theproduct by partial nitrification prior to evaporation is proposed based on a series ofexperiments conducted to evaluate the appropriateness of this approach.The ammonium-N concentration of the digestate used was 1.7 g/L. The nitrification does notappear to be inhibited by ammonia, nitrate or nitrite accumulation, except when pH &gt; 7.5, asituation that can be avoided by regulating the feeding rate based on pH measurements.Significant nitrite accumulation was not observed either. Nitrification is however consistentlylimited by alkalinity so that only about 75% of the ammonia can be converted to nitratewithout alkalinity supplementation. The nitrification brings the pH down below 5.0 where theremaining ammonia is present as&gt; 99% NH/. At this condition the nitrified digestate can beevaporated without a significant nitrogen loss and the product is recognized to be a highquality liquid fertilizer. It is suggested that the production of concentrated partially nitrifiedorganic fertilizers can become a sustainable way of nutrient recovery from anaerobicdigestates originating from municipal organic wastes.

Environmental assessment of supercritical water oxidation and other sewage sludge handling options

Sustainable development relies on the eco-efficient use of all flows in society; more value created out of each resource unit. Supercritical water oxidation (SCWO) can be used for treatment of wet organic waste. The technology has been under development for over 20 years but has not yet been fully commercialized. SCWO allows for complete oxidation of all organics in sewage sludge and almost complete recovery of the inherent energy, essentially without harmful emissions. In this paper, a life-cycle assessment (LCA) of sewage sludge SCWO (Aqua-Critox) is presented and the results are compared with LCA results for other sludge handling options: agricultural use, co-incineration with municipal solid waste, incineration with subsequent phosphorus extraction (Bio-Con) and sludge fractionation with phosphorus recovery (Cambi-KREPRO). For SCWO, beneficial utilization of the heat of reaction is of crucial importance for the outcome. The electricity consumed by pumping and the nitrous oxide produced are other important parameters. The best sludge handling option from an environmental point of view depends on what aspect is considered more important in the impact assessment. Regarding global warming, the energy recovery methods perform better than agricultural use.

Applications of the anaerobic digestion process.

At the start of the new millennium waste management has become a political priority in many countries. One of the main problems today is to cope with an increasing amount of primary waste in an environmentally acceptable way. Biowastes, i.e., municipal, agricultural or industrial organic waste, as well as contaminated soils etc., have traditionally been deposited in landfills or even dumped into the sea or lakes without much environmental concern. In recent times, environmental standards of waste incineration and controlled land filling have gradually improved, and new methods of waste sorting and resource/energy recovery have been developed. Treatment of biowastes by anaerobic digestion processes is in many cases the optimal way to convert organic waste into useful products such as energy (in the form of biogas) and a fertilizer product. Other waste management options, such as land filling and incineration of organic waste has become less desirable, and legislation, both in Europe and elsewhere, tends to favor biological treatment as a way of recycling minerals and nutrients of organic wastes from society back to the food production and supply chain. Removing the relatively wet organic waste from the general waste streams also results in a better calorific value of the remainder for incineration, and a more stable fraction for land filling.

Indirect data collection for waste statistics and waste indicators

Waste statistics is a broad term describing multiple categories of refusals and waste. These can include: liquid sewage, wet organic waste, dry municipal waste, hazardous material, pesticides, toxic chemicals, medical waste, nuclear waste, sludge containing heavy metals, metals, iron, car scrapes and more. In many countries, especially developing countries (with new industrial centres), no organised reporting system of waste quantities is available. The aim of this review is to show how quantifying waste material might be attempted even when data from well-planned data collections is not available. In such cases, information can be collected by Indirect Methods. This system, even though it is not a perfect data collection system, utilizes waste indicators that reflect waste production. Examples of using recycling data, lawsuit information, data on municipal and hazardous waste and others as indirect data are described. We suggest indicators for various waste categories even though the source of information is indirect. Advantages and disadvantages of utilizing this method are discussed. The manner in which “Indirect Data” (imperfect data) is currently obtained is an inexpensive way to roughly assess the situation. The estimates may lack reliability and should be evaluated critically: If available data on the indicator variables is inaccurate, indicators will be poor predictors of waste quantity and trends. Furthermore, indirect data does not make it possible to calculate an error term. The conclusion from this report is that governments should attempt to ensure sampling surveys for the different waste sectors. If such information is lacking, indirect data can be used for statistical analysis, providing estimates. Such information is important for efficient waste management. This knowledge will further assist in attempts to protect the environment from the destruction of natural resources by waste material.

Hydrothermal gasification of biomass and organic wastes

Wet biomass and organic wastes can be efficiently gasified under hydrothermal conditions to produce a hydrogen rich fuel gas. New experiments in two tubular flow reactors and in two batch autoclaves with carbohydrates, with aromatic compounds, with glycine as a model compound for proteins and with real biomass are reported for different residence times, temperatures and pressures. It was found that at 600°C and 250 bar all compounds are completely gasified by addition of KOH or K 2CO 3, forming a H 2 rich gas containing CO 2 as the main carbon compound. Concentrations of CO, CH 4 and C 2–C 4 hydrocarbons are low in the product gas (<1, ∼3 and <1 vol%, respectively). Carbon balances for the smaller flow reactor are closed to better than 96%. Ranges of product concentrations are given as estimated from experimental reproducibility. Some reflections for the engineering of a pilot plant are presented.

Thermal hydrolysis (TDH) as a pretreatment method for the digestion of organic waste

The recycling concept under consideration is based on the process of Thermal Hydrolysis (TDH) followed by an anaerobic digestion. By increasing pressure and temperature the organic part of the waste is split up in a first step into short-chain fragments that are biologically well suited for microorganisms. The following fermentation runs much faster and more complete than in conventional digestion processes and the biogas yield is increased. Left is just a small amount of a solid residue that can be easily dewatered and utilized as surrogate fuel for incineration or as compost additive. The thermal hydrolysis process allows a complete energy recovery from organic waste. During the total procedure more energy sources are produced than are needed for running the plant. The procedure is especially suited for wet organic waste and biosolids that are difficult to compost, such as food scraps, biological waste from compact residential areas and sewage sludge. As a complete disinfection is granted due to the process temperatures the procedure is also suited for carcasses.

Anaerobic waste digestion in Germany--status and recent developments.

Anaerobic treatment processes are especially suited for the utilization of wet organic wastes from agriculture and industry as well as for the organic part of source-separated household wastes. Anaerobic degradation is a very cost-effective method for treating biogenic wastes because the formed biogas can be used for heat and electricity production and the digester residues can be recycled to agriculture as a secondary fertilizer. Anaerobic technology will also be used for the common treatment of wastes together with renewable energy crops in order to reduce the CO2-emissions according the Kyoto protocol. Various process types are applied in Germany which differ in material, reaction conditions and in the form of the used reactor systems. The widespread introduction of anaerobic digestion in Germany has shown that biogenic organic wastes are a valuable source for energy and nutrients. Anaerobic waste treatment is done today in approx. 850 biogas plants on small farm scale as well as on large industrial scale with the best beneficial and economic outcome. Due to some new environmental protection acts which promote the recycling of wastes and their utilization for renewable energy formation it can be expected that several hundreds new biogas plants will be built per year in Germany. In order to use the synergetic effects of a combined fermentation of wastes and energy crops new process types must be developed in order to optimize the substrate combinations and the process conditions for maximum biodegradation.