Conversion of Large Scale Wastes into Value-added Products

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Introduction

M. Balakrishnan, V.S. Batra,

J.S.J.Hargreaves, and I.D. Pulford

Recently, concern about the fate of waste products produced by a whole range of

industrial processes has combined with a growing realization that they may have

potential uses and, therefore, value (Balakrishnan etal., 2011; Gupta etal., 2009).

This has led to a large number of studies aimed at utilizing such wastes, which is

the focus of this book. The following chapters discuss various selected classes of

large-scale waste and their current applications and potential future applications.

Chapter 2 details different wastes derived from metal processing. In Chapter 3,

combustion products are discussed; here, the focus is on coal combustion products

given the widespread use of coal. Chapter 4 details waste electrical and electronic

equipment (WEEE) and Chapter 5 discusses food waste. Before discussing eachof

these classes, it is important to make a number of general considerations.

CONTENTS

1.1 Drivers for Waste Recovery and Reuse ............................................................2

1.1.1 Problems of Disposal of Large Amounts of Waste ..............................2

1.1.2 Environmental Issues ............................................................................3

1.1.3 Resource Recovery ...............................................................................3

1.1.4 Economics.............................................................................................6

1.1.5 Legislation ............................................................................................6

1.2 Types of Waste ..................................................................................................8

1.3 Secondary Processes ........................................................................................9

1.3.1 Catalysis ................................................................................................9

1.3.2 Energy Production .............................................................................. 10

1.3.3 Agricultural ........................................................................................10

1.3.4 Environmental Clean-Up .................................................................... 11

1.4 Secondary Products ........................................................................................ 12

1.4.1 Cement, Concrete, and Ceramics .......................................................12

1.4.2 Chemicals ...........................................................................................13

1.4.3 Composts ............................................................................................13

1.4.4 Metal Recovery ...................................................................................13

1.5 Conclusion ...................................................................................................... 13

References ................................................................................................................13

2 Conversion of Large Scale Wastes into Value-added Products

1.1 DRIVERS FOR WASTE RECOVERY AND REUSE

A number of factors combine to act as drivers for waste recovery and reuse:

1. Problems of disposal of large amounts of waste

2. Environmental issues

3. Availability of resources

4. Economics

5. Legislation

The focus widens going down this list, from aspects that affect mainly the

producers of the waste to ones affecting the whole community. The environmental

and economic issues drove the political requirements that most developed, and

increasingly less-developed, countries have now translated into legislation.

1.1.1 Problems of DisPosal of large amounts of Waste

Some industries produce very large amounts of waste. For example, global y ash

production from coal combustion (Chapter 3) is estimated to be of the order of 500

million tonnes/year, while slag from iron and steel production and red mud from

production of aluminium (Chapter 2) both generate about 100 million tonnes/year.

(Rounded gures are used here; see individual chapters for more detail). As these

are continuous processes, the wastes must be removed from the systems in order for

them to function efciently. Traditionally, such wastes have been dumped in heaps

or lagoons, which can become extensive as more wastes are produced. The disposal

sites also have to be close to the source of the waste (blast furnace, power station,

etc.) in order to reduce transportation costs. As a result, large areas adjacent to such

facilities can be given over to disposal and storage of waste.

Waste from various food producing processes can also be signicant (Chapter 5).

For example, approximately 60 to 70 million tonnes of both rice husk and orange

peel are produced annually. Again, such waste is produced locally where foodstuffs

are processed. For example, it is estimated that 2.5 to 4.0 million tonnes of olive oil

processing waste are produced annually in the Andalusia region of Spain alone.

Over recent years, WEEE (Chapter 4) has become signicant, with an estimated

annual production of 20 to 25 million tonnes. Much of the material that goes into

this waste stream is bulky (refrigerators, television sets, etc.), which causes particular

storage problems.

In addition to the availability of land on which to store wastes, the main issues that

also need to be considered are safety and toxicity. Storage of large volumes of waste

presents the problem of physical containment. In some cases, the waste may contain

toxic components, whose dispersal into the wider environment could be detrimental

to human health and the ecology of the local area. There have been a number of

high-prole incidents over recent years where failure of the waste containment system

has led to fatalities, poisoning of humans, and contamination of land and water.

Selected recent incidents taken from a list of major tailings dam failures spanning the

previous 50+ years published on the Web (http://www.wise-uranium.org/mdaf.html)