Life Cycle Comparison of Two Options for MSW Management in Puerto Rico: Thermal Treatment vs. Modern Landfilling

The management of municipal solid wastes (MSW) in Puerto Rico is becoming increasingly challenging. In recent years, several of the older landfills have closed due to lack of compliance with federal landfill requirements. Puerto Rico is an island community and there is limited space for construction of new landfills. Furthermore, Puerto Rico residents generate more waste per capita than people living on the continental US. Thermal treatment, or waste to energy (WTE) technologies are therefore a promising option for MSW management. It is critical to consider environmental impacts when making decisions related to MSW management. In this paper we quantify and compare the environmental implications of thermal treatment of MSW with modern landfilling for Puerto Rico from a life cycle perspective. The Caguas municipality is currently considering developing a thermal treatment plant. We compare this to an expansion of a landfill site in the Humacao municipality, which currently receives waste from Caguas. The scope of our analysis includes a broad suite of activities associated with management of MSW. We include: (i) the transportation of MSW; (ii) the impacts of managing waste (e.g., landfill gas emissions and potential aqueous run-off with landfills; air emissions of metals, dioxins and greenhouse gases) and (iii) the implications of energy and materials offsets from the waste management process (e.g., conversion of landfill gas to electricity, electricity produced in thermal treatment, and materials recovered from thermal treatment ash). We developed life cycle inventory models for different waste management processes, incorporating information from a wide range of sources — including peer reviewed life cycle inventory databases, the body of literature on environmental impact of waste management, and site-specific factors for Puerto Rico (e.g. waste composition, rainfall patterns, electricity mix). We managed uncertainty in data and models by constructing different scenarios for both technologies based on realistic ranges of emission factors. The results show that thermal treatment of the unrecyclable part of the waste stream is the preferred option for waste management when compared to modern landfilling. Furthermore, Eco-indicator 99 method is used to investigate the human health, ecosystem quality and resource use impact categories.

Developments in WTE Within Europe

A description is given of the key elements of European Union (EU) policy and EU directives, which may affect the desired switch from landfill to Waste-to-Energy (WTE) and recycling of waste within the 27 EU countries. The most important directive is the one which forces individual member states to reduce the landfill levels for MSW to 35% of the quantity of the base year 1995.

Keeping Up With Growth by Recommitting to a Long-Term Waste-to-Energy Future

The Solid Waste Authority of Palm Beach County (Authority) has owned the North County Resources Recovery Facility (NCRRF) since 1989, producing clean, economical and renewable energy from refuse derived fuel while preserving precious landfill space. As with any facility as it approaches the end of its first 20-year operating term, the Authority found it necessary to initiate a comprehensive refurbishment to ensure its continued effective operations. The operating agreement between the Authority and the Palm Beach Resource Recovery Corporation (PBRRC), a subsidiary of Babcock & Wilcox (B&W), is set to expire concurrently with the end of the this 20-year term. The Authority acknowledged that PBRRC has unparalleled institutional knowledge of the NCRRF and, as such, took the opportunity to renegotiate its operating agreement with PBRRC for an additional 20-year term. The Authority was also able to build into the new operating agreement conditions for PBRRC to provide assistance to a third party design-builder performing the refurbishment. Additionally, understanding that B&W produced many of the key combustion unit components of the original NCRRF construction, the Authority worked into the new agreement terms for B&W to provide several essential components for the refurbishment that will be installed by the design-builder. When the refurbishment is completed in 2011, the Authority will still only have disposal capacity through 2021 with its existing landfill. To be able to keep up with rapid growth in Palm Beach County, the Authority has initiated the due diligence phase for the development of a new mass burn waste-to-energy facility and landfill that will expand the disposal capacity of the Authority’s system for more than 100 years.

Unique Elements of the Olmsted County Facility Expansion

Olmsted County is currently expanding their existing waste-to-energy facility in Rochester, Minnesota to add a third mass burn waste combustor. The new unit will have a capacity of 200 TPD, effectively doubling the size of the existing capacity. This paper will discuss some of the unique aspects of this project and review the current status. Some of the interesting and unique features to be discussed include: 1. Environmental Permitting – The county decided to do a voluntary EIS. 2. Project approach – The county is using a Construction Manager at Risk approach for construction of the facility. 3. Engineering – The engineering scope includes several separate procurements of major equipment packages, balance of plant design and several auxiliary projects related to the ‘utility’ system. 4. Operator Collaboration – Olmsted County is one of a few public owners that operate their facility. Their knowledge of the existing facility and of operating a mass burn facility has been used extensively in the planning and design of the new unit.

Using a Carbon Balance to Estimate Greenhouse Gas Emissions and Mitigation From Municipal Solid Waste Management

Municipal solid waste (MSW) management is internationally recognized for its potential to be both a source and mitigation technology for greenhouse gas (GHG) emissions. Historically, GHG emission estimates have relied upon quantitative knowledge of various MSW components and their carbon contents, information normally presented in waste characterization studies. Aside from errors associated with such studies, existing data do not reflect changes over time or from location to location and are therefore limited in their utility for estimating GHG emissions and mitigation due to proposed projects. This paper presents an alternative approach to estimate GHG emissions and mitigation using the concept of a carbon balance, where key carbon quantities are determined from operational measurements at modern municipal waste combustors (MWCs).

Unleashing the Power in Waste: Comparison of Greenhouse Gas and Other Performance Indicators for Waste-to-Energy Concepts and Landfilling

A CO2-evaluation is made for landfill and Waste-to-Energy (WtE) concepts. Different concepts are identified and compared for their performance on energy and materials recovery. Performance indicators for WtE are compared; like energy efficiency, EXergy efficiency, the R1-D10 formula from the EU Waste Framework directive, and CO2-emission and avoidance. It is shown that, due to the biomass content and the avoidance effect due to the recovery of energy and materials, conventional WtE has a near zero CO2-emission per ton of waste. Optimised WtE can have a significant negative overall emission of 200–300 kgCO2/ton of waste. This means an absolute net avoidance of CO2 by WtE. The reduction relative to land filling is as much as 500–1200 kgCO2/ton of waste. The potential for optimisation of the energy recovery as well as the material recovery of the WtE infrastructure is demonstrated. If WtE is evaluated as a power plant, an optimised plant can have an emission of only 0,336 kgCO2/kWh, lower than a gas fired electrical power plant, and this absolute figure does not include the avoided landfill emissions. With CHP this can be reduced even further. The actual potential of electricity production from WtE for the EU-15 is calculated to be over 7,5% of total electricity production. Additionally heat and the metal recoveries could be doubled.

Transforming Solid Wastes Into High Quality Bioenergy Products: Entropy Analysis

Although energy analysis of a pyrolysis system improves the thermal efficiency of the process, it did not account for the quality of energy used and produced from the process. This paper presents the entropy of analysis of converting solid wastes into useable bio-products during pyrolysis. The entropy balance was performed on a continuous flow pyrolysis reactor system using pine pellets as a feedstock at the pyrolysis temperature of 773 K. An interesting conclusion was drawn from the results that the pyrolysis process converted low quality and high entropy biomass into high quality and low entropy energy products char, bio-oil, and gases. The analysis concluded that the both pyrolysis and combustion were the process of low entropy production and most part of the irreversibility or positive entropy production was mainly associated with condenser unit. The high quality energy producing pyrolysis process may be included as part of the future biorefinery.

Advances in Fabric Selection for Dust Collection Equipment in WTE Plants

Fabric selection is a critical component in the operation of a dust collection system venting a waste to energy boiler. This paper will discuss the factors to be evaluated when selecting the proper fabric to use in filtration systems venting waste and refuse derived fuel fired boilers. Consideration will be given to the type of scrubbing equipment, the type of cleaning system, the design parameters of the unit, and the gas stream chemistry. Operating experience from existing filtration systems will also be presented. Special emphasis will be made on equipment design, particulate capture and filter service life. A look at new developments in fabric filtration, including fabric blends, micro-denier filtration, and the use of pleated filter technology, will complete this overview.

Plasma Gasification: A Proven Technology

Plasma gasification is an efficient and environmentally responsible form of thermal treatment of wastes. In the plasma gasification process, extremely high temperature gases are used to break down the molecular structure of complex carboncontaining materials — such as municipal solid waste (MSW), tires, hazardous waste and sewage sludge — and convert them into synthesis gas (syngas) containing hydrogen and carbon monoxide that can be used to generate power or other sustainable sources of energy. Gasification occurs in an oxygen starved environment so the waste is gasified, not incinerated.

Advanced Technologies Provide New Insights for Assisting Energy from Waste (EfW) Boiler Combustion Monitoring, Operations and Maintenance

This paper focuses on recent advancements in the areas of imaging technology and flue gas temperature measurement which are providing new insights for plant engineers into combustion conditions and operation in Energy-from-Waste (EfW) facilities. The paper describes how Covanta Energy, an operator of over 30 EfW facilities and Enertechnix, a manufacturer of advanced combustion products and services, are developing new technologies in these following areas: Infra-red (IR) imaging using a mobile camera to provide active viewing of the boiler and combustion conditions; Digital recording of images of slagging, waste stream movement, and refractory inspection; Online inspection in back pass convection areas with a video camera that extends up to 20 feet into boiler. Furnace Exit Gas Temperature (FEGT) measurement integrating proven acoustic pyrometer technology to replace inherently inaccurate contact temperature methods such as thermocouples. The paper examines how each of these technologies is being introduced into EfW facilities operated by Covanta Energy. Actual results are used to evaluate the potential these new methods have for improving combustion, reducing maintenance costs and providing plant operators with useful tools for operating EfW facilities. Video images of the furnace and convection sections will be provided and discussed. FEGT data from comparative technologies is presented. The data is interpreted in order to compare the accuracy of the acoustic pyrometer measurement against other methods. Potential and determined benefits are presented and outlined. The paper attempts to provide a framework to help facilities understand the importance and impact of accurate FEGT measurement in the combustion process.