A large fraction of the municipal solid wastes (MSW) stream in the U.S. comprises of natural organic compounds (i.e., food and plant wastes) with high moisture content and low heating value. While these properties are undesirable during the combustion of MSW in waste-to-energy (WTE) plants, they are required for anaerobic digestion (AD). During AD, methane gas is produced that can be captured and used for energy generation. The required long residence times limit the throughput of an AD plant but further development may result in increasing the rates of bioreactions. This paper introduces current AD practices and identifies possible synergies between AD and WTE. It is suggested that co-siting of WTE and AD facilities may result in mutual benefits.

Municipal solid wastes (MSW) typically contain plastic materials, leather, textiles, batteries, food waste and alkalis. These materials are sources of chlorine, sulfur, potassium, zinc, lead and other heavy metals that can form corrosive media during combustion of the MSW in waste-to-energy (WfE) facilities. Chlorides and sulfates, along with fly ash particles, condense or deposit on the waterwall surfaces in the combustion chamber and on other heat exchanger surfaces in the convection path of the process gas, such as screens and superheater tubes. The resulting high corrosion spots necessitate shutdowns and tube replacements, which represent major operating costs. The aim of ongoing research at Columbia University is to gain a better understanding of the effects of fuel composition, products of combustion, and chemical reactions that lead to the corrosion of metal surfaces in WfE boilers. The potential chemical reactions and their chance of occurrence were determined by means of thermochemical calculations of the respective equilibrium constants as a function of temperature and gas phase composition. characteristics of the MSW fuel result in incomplete combustion, i.e. localized high CO levels, occasional high heat flux on the wall caused by flame impingement, and the formation of aggressive deposits. MSW contains alkali metals such as sodium and potassium, heavy metals such as lead, tin, and zinc and various chlorine-containing compounds, all of which can form potential corrosive agents.The surface temperature of the metal wall, gas temperature, gas composition and deposit characteristics are main factors that influence the high-temperature corrosion of WIE boilers. High temperatures of metal surfaces, either due to high thermodynamic software program developed by radiation flux to the wall or inadequate transfer of Outokwnpu Research in Finland [3]. D ep osit characteristics: Increasing concentrations in CI, S04, alkaline and heavy metal components influence both the physical and chemical

In the U.S., about 28.5 million tons of municipal solid waste are combusted annually in waste-to-energy facilities that generate 25–30% of ash by weight of the MSW feed. Since some residues were found to contain high levels of lead and cadmium prior to the 1990s, they were commonly associated with environmental pollution. However, for the last years nearly all ash samples have been tested non-hazardous. Research on the beneficial use of combustion residue has been conducted for the past few decades yet the actual ash reuse rate in the U.S. has remained close to 10%. Currently most of the ash is landfilled at considerable cost to the waste-to-energy industry. A consortium of researchers at Columbia University, the State University of New York at Stony Brook, Temple University, and other institutions seeks to develop and to advance the beneficial uses of combustion residues, such as in construction materials or remediation of contaminated abandoned mines and brownfields. This paper describes the search for beneficial use applications and provides an overview of the first year of this consortium.

Maintenance and capital dredging is absolutely necessary to keep shipping lanes open and harbors accessible. Since the early 1970s the ecological impact of dredging processes and disposal techniques has been studied carefully. Facing strict environmental regulations, ports worldwide are currently changing their dredged material management plans to stay economically viable. Restrictions and exclusion of traditional disposal techniques require a multifaceted approach to dispose of, recycle, decontaminate and reuse the material. For clean dredged material several strategies of beneficial use have been established successfully throughout the last decades. However, contaminated sediments are more difficult to place. Especially the productive use of the soft clay / silt fraction poses many unsolved problems because it tends to attract the pollutants. Existing technologies are often energyconsuming and expensive, treat only certain fractions of dredged material, raise issues of secondary pollution, or lack community acceptance. At Columbia University, research has been conducted on the beneficiation of dredged material from the Port of New York and New Jersey. Annually about 4.5 million cubic yards have been dredged to maintain and improve its waterways. The bulk of the dredged material is contaminated and not suitable for unrestricted use or disposal. Investigations of physical and chemical properties suggest a beneficial use as filler material in various applications. Prior treatment and detoxification is necessary. A method to prepare dredged material, and especially the fine fraction thereof, for further use was developed. Being able to engineer certain properties according to specific needs, one can obtain dredged material that functions as a valuable semiproduct or end product competing ecologically and economically with existing materials. Herein, the approach, findings and results of the search at Columbia University for beneficial use of dredged material are introduced. Beneficiation is the transformation of a waste material into a valuable resource, which requires the adaptation, modification and engineering of properties according to specific needs.

The combustion of municipal solid wastes for generating electricity (Waste-To-Energy) has been recognized by several states as a renewable source of energy. Yet, there has been determined opposition by some environmental groups to including WTE in the portfolio of renewable energy sources that will benefit from a tax credit designed to decrease reliance on non-renewable fossil fuels. While WTE is considered worldwide as a solid waste management option, the recognition and acceptance of WTE as a clean source of energy still requires public involvement and education. This paper will examine the “pro” and “con” arguments for considering WTE as a renewable energy source.