Conversion Of Solid Waste Research Articles

IEA bioenergy agreement task XI: Municipal solid waste conversion to energy end of task review

This paper overviews the main work and achievements of the International Energy Agency's Task on Municipal Solid Waste (MSW) conversion to energy. The objectives of the Task were to encourage information exchange between research and development programmes and other new initiatives relating to energy recovery from MSW, and to use this information to benefit research, development and deployment programmes on energy recovery from MSW in participating countries. Governments are now encouraging the sustainable use of MSW resources, both domestically and as part of their international obligations. These encourage development of a waste management hierarchy which places greater emphasis on waste prevention and minimisation through materials and energy recovery. The IEA Task provided participating countries with an international perspective in the areas of thermal technologies (incineration of MSW and refuse derived fuel and ash residues), biological technologies (landfill gas and anaerobic digestion of MSW) and generic issues relating to MSW conversion technologies (source separation, recycling, mechanical processing, sampling and analytical protocols). Work was carried out through meetings, study tours and networks. The main benefits from this international collaboration were that participants obtained up-to-date information on technical and non-technical issues affecting energy from waste technologies, including legislation, methodologies, and plant experience, that they could then use to encourage the development of energy from waste in their own countries. The work of the Task will continue for a further three years during 1995–1997.

The International Energy Agency's (IEA) work in harmonising sampling and analytical protocols related to municipal solid waste (MSW) conversion to energy

Legislation relating to the composition of waste and the end products from energy from waste processes is becoming increasingly strict, therefore appropriate sampling procedures need to be available to perform the analyses accurately. It is also important to be able to compare methods used and results obtained from analytical procedures carried out in different countries. Efforts are focused in three areas: Household waste: A considerable body of information has been compiled on methods used to produce compositional information on household waste. This has been added to by literature searches and from countries not participating directly in the work of the activity. The data collated has been used to review protocols being used for the sampling and analysis of household waste. Landfill gas: This work has focused on methods used to determine the concentration of trace organic compounds present in landfill gas. Concerns about such emissions focus on their potential contributions to: • • human toxicity • • environmental impacts (e.g. odour and global pollution events) • • corrosion in gas utilisation systems • • the composition of emissions from flares, engines, and turbines The methods used vary considerably, often focusing priority pollutants. Studies investigating such emissions are being carried out world-wide. Emission monitoring at MSW combustion facilities: New information concerning the potential application of advanced emissions monitoring techniques at coal and MSW combustion facilities has been collated. This is currently being incorporated into a new document which will update the 1991 IEA technology report “Review of Emissions and Performance Monitoring of MSW Incinerators”.

Can Systems Engineering Save the Environment?

ABSTRACTThe environmental impact report (EIR) and the environmental impact statement (E1S) are the lawyer's version of systems engineering. But systems engineering is a disciplined methodology for managing the risks and decisions involved in designing and implementing systems of optimum capability within the constraints of resources and time. Although it has come into widespread use in the defense industry and in some segments of the commercial industry, this methodology has not been widely adopted by municipal governments as a tool for making decisions and managing complex projects. In this article I present a framework in which local governments can use the methods of systems engineering to evaluate the environmental consequences of their projects. I illustrate this process by analyzing the trade-offs in solid-waste disposal. This analysis will show that by incorporating into the decision-making process the environmental consequences of either landfilling or the conversion of solid waste to energy, the ...

Dry Anaerobic Conversion of Municipal Solid Waste by Means of the Dranco Process

The Dranco process has been developed for the conversion of solid organic wastes, specifically the organic fraction of municipal solid waste (MSW), to energy and a humus-like final product, called Humotex. The Dranco process can be compared to landfill gas production, accelerated by a factor 1000. A Dranco installation with a digester of 808 m3 treating 10,500 tons of source separated waste per year will be constructed in 1991 at Brecht, Belgium. A description of the plant is elaborated. A demonstration plant of 56 m3 has been in operation for several years in Gent, Belgium using mixed garbage as a feedstock. The operating temperature in the digester is 55°C and the total solids concentration is ca. 32%. The mean gas production rate is 3.33 Nm3 CH4/m3reactor.day. The volumetric loading is 17.3 kg COD/m3reactor.day and the COD reduction is 55%. The gas production process is finalized in 3 weeks. The final product is dewatered and further stabilized in a 10 day aerobic post-treatment. The Humotex is free of pathogens. Low concentrations of heavy metals can only be obtained through separate collection of garbage. The Dranco process then also focusses on the digestion of source separated waste such as vegetable, fruit, garden and non-recyclable paper waste.

Municipal solid waste conversion to energy

In recent years it has been recognised by an increasing number of nations that there is considerable energy potential within MSW. As a result many countries have established R,D& D programmes to examine methods of exploiting this potential. The IEA's MSW Conversion Activity was set up in 1986 to provide an infrastructure for sharing information and co-ordinating work in this area internationally. This Activity was extended in 1989 and currently a total of 9 nations participate in it. To cope with the wide scope of the area (encompassing both biological and thermal processing of MSW) the Activity was divided into three subgroups or Expert Working Groups (EWGs). Each of these dealt with a distinct area of expertise: •Downstream effects of source separation and screening of MSW •Sampling and analytical protocols •Landfill gas In addition to these groups a central secretariat based at Harwell (UK) has provided guidance, established and administered databases of contacts and produced a series of national reports. This paper describes the achievements of the Activity and discusses work proposed for the future.

CAN SYSTEM ENGINEERING SAVE THE ENVIRONMENT?

ABSTRACTThe Environmental Impact Report (EIR) and the Environmental Impact Statement (EIS) are the lawyer's version of system engineering. But System engineering is a disciplined methodology for managing the risks and decisions involved in designing and implementing systems of optimum capability within the constraints of resources and time. Although it has come into widespread use in the defense industry and in some segments of the commercial industry this methodology has not been widely adopted by municipal governments as a tool for making decisions and managing complex projects. In this article I present a framework in which local governments can use the methods of system engineering to evaluate the environmental consequences of their projects. I shall illustrate this process by analyzing the tradeoffs in solid waste disposal. This analysis will show that by incorporating into the decision making process the environmental consequences of either landfilling or the conversion of solid waste to energy the public interest is best served with conversion to energy.

Municipal solid waste conversion to energy

Municipal solid waste (MSW) conversion — the recovery of energy (and materials) from MSW — has been the subject of one activity within the 1986–88 International Energy Agency Bioenergy Agreement. The participating countries have been Canada, Sweden and the UK, with the activity being led by Harwell Laboratory. The major aim of the work has been to establish a co-operative approach to the R&D undertaken in each country on MSW conversion. The emphasis has been on R&D which concentrates on technical and environmental aspects of energy (rather than materials) recovery. This has encompassed a wide range of technology options — mass combustion, production and combustion of refuse derived fuels, abstraction and utilisation of landfill gas, anaerobic digestion, and thermal processing. The paper gives a summary of the approach taken in fulfilling the aims of the activity and summarises recent, current and proposed R&D programmes in each country. Proposals made at an expert workshop for specific co-operative ventures during 1989–91 are also summarised.

Bioconversion to single cell protein: A potential resource recovery from paper mill solid waste

Disposal of paper mill waste by bioconversion is a novel approach which allows a direct conversion of cellulosic solid waste into fungal biomass. A cellulolytic microorganism Myrothecium verrucaria has been used for protein production under batch conditions in flasks. Biomass yield of 0.375 g per g of substrate consumed with 50–60% solid waste usage was observed. The nutritional quality of the biomass in terms of fat and protein contents shows promise for feed supplementation of monogastric animals.

Conversion of Tomato, Peach and Honeydew Solid Waste into Methane Gas

ABSTRACT METHANE production by anaerobic digestion of tomato, honeydew and peach solid wastes was in-vestigated. Results from a two-year laboratory investiga-tion and seasonal operation of a pilot plant size digester are presented. For 4L laboratory digesters operating at 35 C the following loading rates and retention times were found to be optimal for tomato, honeydew and peach residues, respectively: 5, 3, and 1 kg VS/m^-d and 25, 20, and 15 d. Under these operating conditions 33 percent, 83 percent and 86 percent of the volatile solids were destroyed for tomato, honeydew and peach residues, respectively, and the corresponding gas productions, corrected to STP, were 0.43, 2.45, and 1.15 vol/digester vol/day. On a conversion efficiency basis these values relate to 0.14, 0.81 and 1.15 mVkg VS load-ed, respectively. Operation of the 22 m^ pilot plant generally confirmed the laboratory data for tomato solid waste.

Leachates from Solid Waste Recovery Operations

Conversion of urban solid waste to energy often produces solid residues that require subsequent disposal. Generally they are placed in ash ponds, spread on land, or placed in sanitary landfills. These residues were studied, and the potential environmental problems associated with their disposal were assessed. Peak concentrations of various leachate constituents exceed permissible discharge standards. These materials leach rapidly from the residues so that the total leached mass per unit of residue is quite small. Therefore, some type of treatment of ash pond overflow may be required if controlled discharge will not keep constitutent concentrations below permissible discharge levels.

Continuous cellulose-to-glucose process

A continuous cellulose-to-glucose process has been developed by W. Brenner at New York University as part of an EPA project for conversion of solid wastes to fuels; the technology could help improve the economics of fermentation of wood, paper, and agricultural and municipal wastes to ethanol for gasohol. A 1 ton/day demonstration plant has been built and is operating on sawdust and pulped newspaper. It uses a twin-screw extruder of the type used in plastics processing to slurry the cram-fed cellulosic feed. Dilute sulfuric acid is added near the outlet of the extruder to hydrolyze the cellulose, which is heated by steam to 450/sup 0/F, to glucose in up to 60% yield; the low residence time minimizes acid-catalyzed degradation. Energy consumption is 1600 Btu/lb cellulose, but this could be reduced by insulating the extruder barrel and quenching the reaction mixture in a heat exchanger. According to C. Rogers (EPA), this technology could produce ethanol by fermentation for $0.85-$1.00/gal, of which $0.60/gal would be for cellulose hydrolysis at mobile plants in the field, with the glucose syrup transported to local fermentation plants. V. R. Srinivasan (La. State Univ.) is studying continuous fermentation of the glucose syrup to methane.

Fuel and feedstock from refuse

Pyrolysis processes for the conversion of municipal solid waste to useful material are options to current disposal methods. Pyrolysis has the potential for volume and mass reduction and energy recovery. Fuel/feedstock products from a pyrolysis reaction system can be liquid, solid, and/or gas with the estimated heating values of 10,000 to 11,000 Btu/lb, 6,000 to 9,000 Btu/lb, and 100 to 600 Btu respectively. Shaft, rotary kiln and fluidized bed reactor types are described. Commercial pyrolysis processes are also discussed. (ND)

Conversion of Solid Waste to Liquid Fuel

A background in the chemistry of cellulose pyrolysis and hydrogenation is provided, and the cellulose liquefaction literature and state of the ait is reviewed. A concept of an ultimate process in which cellulosic solid waste is used both to produce process hydrogen by the water-gas shift reaction and to provide the raw material for conversion to oil is de veloped. The theoretical yield of hydrocarbon oil CnH2n-2 from cellulose is 35.7 weight % or 2.47 bbl/ton at 0.810 specific gravity. An economic process will probably use a reaction medium of cellulosics slurried in oil and will require a catalyst that permits operations at pressures below 1000 psig. The heating value of refuse is approximately 5000 Btu/lb, on an as, is basis and 9000 Btu/lb on a moisture and ash-free basis. At present, pyrolysis processes are capable of produc ing a tar (containing 20 weight % oxygen) with a heating value of 12,000 Btu/lb and an equal yield of char. Hydrogena tion processes have the potential of producing practically oxygen-free oil approaching 18,000 Btu/lb, without the char byproduct.

Developing Markets for Recycled Organic Products in Florida

Issues on various aspects of recycled organic products are drawing increasing attention from public and private sectors. However, most of the attention is being paid to organic recycling as a potential means of reducing wastes going to landfills. It is obvious that conversion of organic solid wastes to various products will reduce disposal problems. This is EDIS document FE499, a publication of the Department of Food and Resource Economics, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL. Published December 2004.
 https://edis.ifas.ufl.edu/fe499

Composting conversion of solid wastes for mushroom growing

AbstractMethods for composting small quantities of organic materials have been developed in order to be able to better study the composting process. A composting bin was developed which holds 27 cu. ft. of compost and which provides uniform conditions of temperature, moisture, and aeration within the compost mass. A system for indoor composting of less than one cubic foot of material has been developed and is described. The methods have been shown to be reliable and reproducible. The composts were evaluated for their suitability for mushroom growing and were found to give high yields of mushrooms.