Incineration as a Waste Management Option

J. PETTS

1 Introduction

Role of Incineration

For thousands of years the value of burning wastes has been recognized, both to reduce the quantity of surplus materials generated by households, trades, and agricultural practices, and to provide fuel for heating or cooking. Recognition of the potential environmental problems generated by burning wastes also has a long history. In the United Kingdom (UK) the existence of city controls on the burning of rubbish in open dumps can be traced back to the 13th century.

The industrial revolution and accompanying urban population explosion of the 18th and 19th centuries transformed the nature and volume of wastes arisings and the potential health problems of improper disposal practices. Mass-burning of wastes in enclosed and controlled conditions became an important waste management option. The first municipal solid waste (MSW) incinerator in England was commissioned at Nottingham in 1874, and by 1912 there were some 300 incinerators in the UK, 76 generating power from waste. Similar early developments took place in other countries, including Sweden, Germany, and the USA. Provision of industrial and hazardous waste incineration capacity was primarily by the major chemical companies requiring in-house facilities; for example, in the US, Dow Chemical installed the first rotary kiln in 1948. The development of large-scale commercial, or merchant, sector hazardous waste incineration capacity has primarily been post-1960s.

The specific benefits of incineration include:

(i) A reduction in the volume and weight of waste especially of bulky solids with a high combustible content. Reduction achieved can be up to 90% of volume and 75% of weight of materials going to final landfill.

(ii) Destruction of some wastes and detoxification of others to render them more suitable for final disposal, e.g. combustible carcinogens, pathologically contaminated materials, toxic organic compounds, or biologically active materials that could affect sewage treatment works.

(iii) Destruction of the organic component of biodegradable waste which when landfilled directly generates landfill gas (LFG ). Estimates suggest that LFG may account for over 40% of the UK 's total methane emissions to atmosphere.

(iv) The recover y of energy from organic wastes with sufficient calorific value.

(v) Replacement of fossil1uel for energy generation with consequent beneficial impacts in terms of the 'greenhouse' effect.

The range of wastes incinerated has expanded in many industrialized countries accompanied by development of specialized and dedicated facilities, including mobile plant. Incineration development has been influenced by: (i) concerns over direct landfill of certain materials, e.g. clinical wastes, (ii) legislative controls curtailing other disposal routes, e.g. for sewage sludge, (iii) identification of new environmental problems requiring remediation, e.g. contaminated soils, (iv) identification of problem wastes for which incineration represents the only commercially available method of disposal, e.g. polychlorinated biphenyls (PCBs), and (v) recognition of energy generation potential from wastes having the potential for adverse environmental impact if inappropriately disposed, e.g. scrap tyres. The extent of uptake of incineration in different countries has been influenced by the availability of other disposal options, in particular landfill, and the degree of central government market intervention in, and financial support of, capital investment and operation costs.

Issues and Concerns

Despite the versatility of incineration as a waste treatment method, opposition, particularly to commercial or merchant sector facilities, has developed to such an extent over the last two decades that in many countries proposals for new plant have faced long delays and often refusal, existing plant have closed, and even national waste management programmes have had to be delayed or modified following protest (for example, that of Spain and also Australia's proposals for handling hazardous wastes). The 1970s saw a rapid growth in the concern over incineration as a public health risk, particularly with the identification of chlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs ) in MSW incinerator emissions, which coincided with the release of 2,3,7,8-TCDD (tetrachlorodibenzo-p-dioxin) and subsequent environmental contamination in a chemical accident at Seveso in Italy.

Public perceptions of health risks are underpinned by the reaction of specific communities against existing and proposed facilities in their local area, including concerns about management and control capabilities, and the management of wastes generally. The balance of arguments for and against incineration forms the basis of national policy development. A justification of incineration as the Best Practicable Environmental Option (BPEO) for managing different waste streams has to be set in the context of reducing the pollution potential of wastes generated and achieving the BPEO by identifying the optimum balance in terms of emissions and discharges at a reasonable cost. In 1993, the UK's Royal Commission on Environmental Pollution (RCEP) published a report on the incineration of wastes, which urged the UK Government to give a higher priority to developing a national waste management strategy based upon the BPEO and commending incineration as having a more important place within such a strategy.

In order to place discussion of the role of waste incineration as the BPEO in some context it is appropriate to first consider the 'current' (i.e. 1993) situation with regard to its use. The potential for incineration is then considered in terms of: (i) policy development; (ii) the economics of incineration; (iii) environmental impact and risk assessment; (iv) technology development; and (v) public acceptance.

2 Use of Incineration

The UK

Table 1 presents approximate annual UK arisings for each of the main incinerable waste streams. As in many countries, the data are estimates being based upon variable arisings data collected by the local authorities at the disposal point rather than at source and in a variety of recorded formats. Figures for arisings of 'special' wastes as defined are subject to annual fluctuations, apparently partly caused by isolated disposals of contaminated soils and similar materials, but have not witnessed a significant growth compared to MSW. The UK imports hazardous wastes for treatment. Figures for the period 1991/2 show that approximately 47 000 tonnes were imported into England and Wales, of which 31% were incinerated. The UK's importance in...