Gasification of Waste Materials

Technologies for Generating Energy, Gas, and Chemicals from Municipal Solid Waste, Biomass, Nonrecycled Plastics, Sludges, and Wet Solid Wastes

Simona Ciuta, Demetra Tsiamis, Marco J. Castaldi

• Publisher: Academic Press
• Year: 2017
• Print ISBN:
  9780128127162
• eBook ISBN:
  9780128127179
• Topic: Technology & Engineering
• Subtopic: Renewable Power Resources
• Index: Technology & Engineering

Gasification of Waste Materials: Technologies for Generating Energy, Gas and Chemicals from MSW, Biomass, Non-recycled Plastics, Sludges and Wet Solid Wastes explores the most recent gasification technologies developing worldwide to convert waste solids to energy and synthesis gas and chemical products. The authors examine the thermodynamic aspects, accepted reaction mechanisms and kinetic constraints of using municipal solid waste (MSW), biomass, non-recycled plastics (NRP), sludges and wet solid wastes as feedstock. They identify the distinctions between pyrolysis, gasification, plasma, hydrothermal gasification, and supercritical systems. A comprehensive summary of laboratory and demonstration activities is presented, as well as field scale systems that have been in operation using solid waste streams as input, highlighting their areas of disconnect and alignment. The book also provides a summary of information on emissions from the stack, comparing them with other thermal conversion systems using similar feedstock. It then goes on to assess the areas that must be improved to ensure gasification systems become as successful as combustion systems operating on waste streams, ranging from feedstock processing to gasifier output gas clean-up, downstream system requirements and corrosion. The economics and future projections for waste gasification systems are also discussed. For its consolidation of the current technical knowledge, this text is recommended for engineering researchers, graduate students, industry professionals, municipal engineers and decision makers when planning, designing and deploying waste to energy projects, especially those using MSW as feedstock. - Provides field demonstrations of large scale systems, their results and the challenges that need to be overcome when developing commercial applications and possible solutions - Presents the most recent technologies in lab and demonstration scale - Examines the critical development needs and real life challenges for the deployment of waste to energy technologies - Provides information on the economics and sustainability of these technologies, as well as their future perspectives

Chapter One

Introduction and Background

Abstract

This chapter provides an overview of the status of municipal solid waste (MSW) management worldwide. It presents a summary view of MSW generation and impacts to society. The chapter completes with a summary of each chapter that is found in the text.

Keywords

MSW generation rate; zero waste; gasification; food-energy-water nexus

Contents

Acknowledgments 12

References 12

The management of municipal solid waste (MSW) in an environmentally sustainable and cost-effective manner is the grand challenge of our time. Yet, it has not received the attention and support that is commensurate with its impact on environmental and human health. In 2015, 2.0 billion tons of waste were generated, while 90% of third-world countries and small-island nations manage their waste through unsanitary landfills and open burning of waste, which is carcinogenic. There are numerous charitable organizations, institutions, nongovernmental, and government agencies focused on solving some of the biggest problems facing humanity. For example, the U.S. Energy Information Agency has quantified that nearly 18% of the world’s population does not have access to secure, clean energy [1], the United Nations has identified that nearly 11% of the world’s population does not have access to clean water, and the World Hunger Organization has determined that approximately 11% of the global population does not have sufficient food [2]. These percentages translate into an average of 910 million people which is larger than the entire population of the United States and the European Union combined. However, that is only 13% of the entire world population that lives with MSW disposal issues because the entire world has a waste generating capacity that must be managed. Yet, there is remarkably little effort compared to other challenges that are funded. The issue of waste management is normally left to regional and municipal agencies to develop an infrastructure focusing on collection. Once collected, the vast majority (~85%) is sent to a landfill or open dump [3].

Waste pollution is an issue that all communities worldwide must control, regardless of geography, culture, or economic standing. Improper waste management can lead to disease, poor standard of living, and environmental decline. One-third of the food generated worldwide is wasted. Municipalities and local authorities aim to manage their communities’ waste, but they are limited in their efforts when the waste generator does not participate in the established programs. For example, the Department of Sanitation in the City of New York has a 30-year old curbside recycling program to divert recyclables from landfills. However, in 2016, only 16% of recyclable items were actually recycled by waste generators; the remaining 84% of recyclables ended up in a landfill. Although mismanagement of waste may be attributed to human behavior, it is also largely attributed to a lack of education of communities and decision-makers. Communities are uneducated on the details of their waste diversion programs, such as recycling, composting, and reuse, and therefore dispose of many items that could otherwise be diverted from landfills. Furthermore, they are either unaware or uninformed of additional waste-management technologies like anaerobic digestion and thermal treatment that can recover value from their waste. A recent survey conducted by Earth Engineering Center at City College (EEC)|CCNY revealed that 34% of New York residents did not know what energy-from-waste (EfW) was and when they were informed, 88% wanted their waste to be managed incorporating this method [4]. Local authorities aim to assess waste-management techniques and determine a best practices approach for their communities based on available resources and current infrastructure. However, there is a lack of education that spans across all citizenry from the public to the municipal decision-makers.

There are several key players who are involved in addressing the issue of waste pollution—the industry, the decision-makers, and the waste generators. The industry aims to provide a solution by developing technologies and materials that would reduce the negative environmental impact of waste. The decisions-makers strive to assess best waste practices for their community based on available resources and infrastructure. The waste generator is an integral part that needs to be made aware of their impact on society. It must be recognized that waste management is not a one size fits all; it must be customized to the community because waste-management issues vary based on geography, affluence, and social culture. For example, in Ethiopia, a waste-management solution needs to be designed for a high food waste stream and minimal infrastructure, whereas in NYC, solutions need to handle higher concentrations of plastics in the stream and manage multiresidential collection. Therefore, education and dissemination of the available technologies and methodologies are key to helping communities develop waste-management solutions that are best for their community.

Many studies have been done on estimating MSW generation that range from local municipalities to global data-gathering yet there remains a gap in the technology understanding and deployment available worldwide. The World Bank has one of the most comprehensive studies done on quantifying MSW generation across all countries and provides an informative categorization related to region and socioeconomic standing yet barely discusses technological solutions. Specifically regarding average waste generation as it connects to income level, the World Bank study presents the following data in Table 1.1 where it can be concluded that waste generation increases as a region’s wealth increases [3].

Table 1.1

World Bank Data of waste generation per capita by income level

Income level	Waste generation per capita (kg/capita/day)
	Lower boundary	Upper boundary	Average
High	0.70	14	2.1
Upper middle	0.11	5.5	1.2
Lower middle	0.16	5.3	0.79
Lower	0.09	4.3	0.60

This table is misleading in two important ways. First, it sends a message that in lower income regions the amount of waste is about one-third that of high income countries. Second, and more important, it is an incorrect metric. The average amount of waste generated is not the major problem regarding MSW management, it is the total amount of MSW produced and the corollary of how it is managed.

Inspection of the detailed data provided in the World Bank study presents a very different perspective that must be more widely understood and disseminated if any real progress is to be made in the sustainable management of wastes. Fig. 1.1 displays the full data set of waste generation compared to median income level, in $US, for all countries. Overlaid is the average zones that are shown in Table 1.1.

Figure 1.1 Complete data set of World Bank MSW generation compared to median income.

The linear regression line included in the data set does show an increase as the median income rises however the statistical fit is an unacceptable 0.07. The thin bars denote the average median income of the categories used by the study where it can be seen that they are clustered near the lower end of the range. The main observation from this data is there is a large scatter where even at the $100,000 median income mark the generation rate ranges from 2.9 to 6.1 pounds per person per day.

Continuing the analysis on a more statistical basis, Fig. 1.2 shows the averages of generation rate for each category of income as designated by the World Bank with standard deviation bars. Here, it becomes obvious that there is no statistical difference in waste generation rate for the different income categories. Moreover, there is a lower bound that appears to develop near 0.3 pounds per person per day as shown in the data on the left graph in Fig. 1.2.

Figure 1.2 Statistical analysis showing the range bound generation rate.

Taking the data and excluding the incomes below $10,000 $US per year reveals a very interesting result. Shown on the right graph in Fig. 1.2 is the same data presented in Fig. 1.1, yet the abscissa covers an order of magnitude from 10,000 to 110,000 $US per year. Those ranges include countries from Brazil and Croatia to Luxembourg and Norway where it can be seen the waste generation rate appears to be range bound between 1.5 and 5.5 pound per person per day. This data forces us to ask; is there a minimum amount of waste that must be generated to sustain life? It also forces the recognition of how to properly manage the waste to minimize the impact on the environment and human health.

A standard response to the waste generation problem is to develop strategies that will lead to a zero waste utopia or to strive to recycle all waste streams leading to a potential closed-loop of resource usage. Those efforts are unrealistic and establish a false opportunity that further removes the waste generators (i.e., the public) from the real ramifications of their behavior. The goal of a zero waste is a commendable one. The perfect culture would be structured to consume sustainably. However, in the 50 or so years in which the world has been actively promoting the concept of a zero waste society, only a fraction of the solid waste generated worldwide is in fact reused or recycled. Landfilling of waste, particularly municipal waste, continues to dominate the world’s waste-management practices. Most people in the developed world are already convinced of merits of environmental protection and would support the goal of zero waste in the abstract. The problem is that zero waste is more of a philosophy than a practical materials management strategy which means it cannot realistically be achieved either technically or culturally.

There is a risk with public perception that all solid waste can be reused or recycled. The short-term risk is the so-called environmentalists who are against any technology and focus on banning materials and asserting “zero-waste” is the solution. Zero-waste does not and will not exist. It is shameful to deny developing areas the benefits of plastics or to saddle them with ideals that cannot be achieved. This ensures that the waste generated continues to create environmental damage and human health hazards. Another short-term risk is the timespan of officials and decision-makers that avoid controversial issues. This leads to paralysis of the agencies and organizations that must take a lead in addressing this issue.

The long-term risks are financial and human resources. For example, at present, a mass-burn waste-to-energy (WTE) facility and a modern designed landfill can manage the garbage at the scale it is generated. However, the expenses of those options preclude poor countries and locales from deploying them. Therefore, other solutions and technologies must be developed or current ones must be adapted to fit. Exactly how this risk will be mitigated is unclear, yet once people are properly informed, they will not divert resources from maintaining the effort.

The sheer volume of generated MSW, coupled with an ingrained culture of disposability, creates a material management system that is inefficient at best, and unsustainable at worst. As local governments struggle with increasing challenges of collection and disposal, radically different approaches are proposed to address the problem. Although most people in the country do not focus on waste management, interested stakeholders seem to be divided into two primary camps. One espouses a cultural and philosophical change to what is called zero waste, holding that the developed world must change consumption patterns to achieve a society in which nothing is wasted and materials are handled in self-contained systems. The other promotes the use of an “integrated” waste-management strategy in which a significant diversion from landfilling via increased recycling/reuse/comp...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Chapter One. Introduction and Background
• Chapter Two. Fundamentals of Gasification and Pyrolysis
• Chapter Three. Laboratory/Demonstration-Scale Developments
• Chapter Four. Field Scale Developments
• Chapter Five. Emissions
• Chapter Six. Critical Development Needs
• Chapter Seven. Economic Summary
• Index