Dioxin Action Plan

Foreword

Executive Summary

Introduction

Taking Action on Dioxin

Why We Should Take Action

Sources of Discharges to Air

Actions for Waste Disposal Sources

Actions for Other Sources

Application of Actions

Appendix 1

Appendix 2

Appendix 3

6 Actions for Sources other than Waste Disposal

Options for reducing dioxin discharges from sources other than waste disposal in the near future are much more limited, for a variety of reasons. This does not mean that the objective of a substantial reduction in overall dioxin discharges cannot be achieved. Some of these sources of dioxin are declining due to other factors. Moreover, as shown in the previous section, waste combustion is the primary target and dioxin discharges from waste disposal sources can be reduced to a very low level.

This section deals with the three categories of non-waste disposal sources: fuel combustion, metallurgical production and processing, and other sources.

6.1 Fuel combustion

Industrial fuel combustion

Wood and coal

There are many boilers of varying sizes throughout the country burning wood and coal to generate process heat and space heat. Although the amount of dioxin discharged from any one unit is likely to be low, about 12% of total dioxin discharges to air come from this source. Cement manufacture, which also combusts coal, is included in this source category. Discharges from New Zealand's two cement producers are estimated to be 1% of total dioxin discharges to air.

Technical options for reducing dioxin discharges from wood-fired and coal-fired boilers do exist, so reduction of dioxin discharges is technically feasible. The installation of a baghouse (See footnote 26) will reduce dioxin discharges from wood-fired boilers burning virgin wood by 15 to 40%, and from coal-fired boilers by about 80%. If the filters in the baghouse are impregnated with a catalyst capable of destroying dioxin, discharges can be reduced still further.

However, cost-effectiveness analysis shows that these gains would be economically inefficient compared with that from, for example, waste incinerators. Each milligram of dioxin not discharged would come at a high cost, (See footnote 27) especially if the boiler is small. This is because the concentration of dioxin in the exhaust gases is very low compared with that in exhaust gases from waste incinerators, and the exhaust gas flows are typically high.

Over time, both boiler turnover and boiler upgrading will lower dioxin discharges to air from this source, although this may be partly counterbalanced by an increasing numbers of boilers. New boilers discharge less dioxin than old boilers because they burn fuel more efficiently, and can often achieve a higher standard of particulate control. Reducing particulate discharge will also reduce dioxin discharge. Both the decrease in the amount of fuel burned and the better combustion performance mean that less dioxin is created per unit of heat output from the boiler. Energy efficiency improvements to existing boilers, such as better control of the fuel/air mixture, are increasingly being done, especially in small boilers.

One study has shown that when 'contaminated' wood is burned, dioxin discharges can increase by a factor of 10 or more. Contaminated wood includes processed wood such as particle board and plywood, and chemically treated wood including wood treated with chlorinated pesticides. Contaminated wood may be burned primarily as a source of energy, but it also serves as a convenient disposal option for wood waste that would otherwise have to be taken to landfills. If contaminated wood waste were to be included in the group of waste covered by the NES, wood-fired boilers that burn contaminated wood would be classed as co-incinerators and the discharges would have to meet the 0.1 ng TEQ/Sm3 limit of the NES.

However, dioxin discharges from burning contaminated wood in New Zealand may be very small. Relatively little national data exist about the extent of the practice, or the types of contaminated wood burned. Any action on this source should begin with gathering information.

There is one caveat to this proposed action on contaminated wood burning. Pentachlorophenol (PCP) treated timber is contaminated wood, and PCP treated timber (and associated wood wastes) should not under any circumstances be burned in industrial boilers without meeting the 0.1 ng TEQ/Sm³ limit of the NES, and the associated requirements of this standard.(See footnote 28) This recommendation is not included in this section, but is incorporated within the proposed actions on waste disposal sources from the co-incineration of waste detailed in Section 5.

In summary, environmental concerns about the industrial combustion of coal should not be focused on dioxin. Concern about the dioxin from the industrial combustion of wood should be focused on the burning of contaminated wood.

Gas

Dioxin discharges from the burning of gas are very low and not of concern. No action is required.

Used oil

Another fuel used in industry is used oil. Low-temperature burning of used oil in small boilers or space heaters and in larger industrial boilers occurs under varying combustion conditions, and pollution control equipment may often be absent. However, because of the relatively small volume of used oil burned in low-temperature appliances nationally, this source contributes < 0.1% of the total dioxin discharges to air. If the volumes of used oil burned at low temperatures were to increase significantly, or if new information showed higher than expected emissions, it would be appropriate to re-evaluate the significance of this activity as a source of dioxin as part of future inventories, and the need for policy interventions.

Used oil is also burned at a high temperature at a cement kiln. Here conditions ensure good combustion, and gas cleaning occurs. Dioxin discharges to air are known to be low.

An important step to minimise discharges of dioxin from used oil burning, especially at low combustion temperatures, is to ensure the oil is not contaminated with high levels of chlorinated chemicals, such as PCBs.

The Ministry for the Environment is currently addressing the future management of used oil in New Zealand. Following consultation on an issues and options paper,(See footnote 29) improvements to the recovery programme for used oil collection is the policy priority. Many regional councils address used oil burning in their regional plans, and the need to develop environmental standards for used oil is not thought to be strong. Also, the Chief Inspector, Explosive and Dangerous Goods, has set fuel specifications for used oil reprocessed as a fuel oil, which should address many of the concerns for adverse environmental effects from burning.(See footnote 30)

Domestic fuel combustion

Coal

Coal is not used extensively in many parts of New Zealand for home heating, although there are exceptions like the West Coast. Nationally, less than 1% of total dioxin discharges to air come from this source. Because poorer combustion conditions exist in open home fires and small solid fuel burners, dioxin concentrations in exhaust gases are typically higher than those from industrial coal combustion. Nevertheless, the smaller volume of coal used domestically means that the total amount of dioxin discharged from this source is currently only about a fifth of that discharged from industrial coal combustion.

Wood

The burning of wood for home heating is a major contributor to dioxin discharges, making up about 15% of the total estimated in the New Zealand inventory. Although there is some uncertainty about this estimate, a strong correlation between domestic wood combustion and dioxin levels in air in New Zealand cities has been found. It is also known that when contaminated wood is burned on home fires, (See footnote 31) there is a significant increase in dioxin discharges.

The trend away from open fires to enclosed wood burners should be reducing dioxin discharges from this source for two reasons:

• an open fire discharges about 10 times as much dioxin per kilogram of wood burned as does an efficient enclosed wood burner
• enclosed wood burners are much more energy efficient than open fires, so less wood need be burned for the same amount of useful indoor heat.

A second beneficial trend is toward better home insulation and, all else being equal, this will also reduce the amount of wood that need be burned and the accompanying dioxin discharges. However, all else is not equal, and the efficiency gains from insulation and from the switch to an enclosed wood burner are likely to be taken partly as a reduced fuel requirement and partly as a warmer indoor environment.

Both these trends should bring other environmental health benefits, such as the reduction of suspended particulates in locations where atmospheric temperature inversions lead to the formation of winter smog.

Some dioxin will still be discharged from domestic wood burning and the question of whether alternative heating fuels should be encouraged is legitimate. There are two 'global sustainability' reasons that make wood a good choice for a home heating fuel. First, the combustion of wood produces no net carbon dioxide, and so is positive from a climate change perspective. Second, wood is a renewable form of energy. The Energy Efficiency and Conservation Act 2000 requires that the use of renewable sources of energy be promoted.

Vehicle fuel combustion

The concentration of dioxin in the exhaust from vehicles is very low, although it is markedly higher for heavy diesel compared with light diesel and petrol. Before 1996 dioxin discharges from cars were higher because chlorinated chemicals had to be added to leaded petrol. About 2% of total dioxin discharges to air comes from motor vehicles.

Dioxin discharges from this source can be expected to continue to decline with increasing energy efficiency, the use of cleaner fuels and of control technologies such as catalytic converters. Government action to better manage the impacts of vehicle emissions on air quality is already taking place through the Vehicle Fleet Emissions Control Strategy.(See footnote 32) However, a decrease in dioxin discharges from existing initiatives would be partly offset by any increase in fuel consumption with increasing vehicle kilometres travelled.

There is no reason for taking any dioxin initiatives on this source, since changes taking place for other reasons should lead to the size of this dioxin source continuing to decline.

6.2 Metallurgical production and processing

In other developed countries, metallurgical production and processing is the second priority for dioxin discharge control after waste combustion. The United Kingdom has set a single concentration-based limit for the metallurgical industry, encompassing iron and steel works, and foundry operations processing zinc, lead, copper and aluminium.

Iron and steel manufacture

The iron and steel industry in New Zealand consists of only two major plants, one producing primary steel and the other recycling steel. These two plants account for about 0.4% of total dioxin discharges to air.

Dioxin discharges from the plant that produces primary steel are low, in large part because a sintering stage is not part of its operation. Overseas, high dioxin discharges from primary steel production have been associated with discharges from sintering of the raw iron ore. The plant that recycles steel has recently been upgraded with new pollution control equipment, and its dioxin discharges are also low.

This industry is localised to one region of New Zealand, and dioxin discharges are already at a comparatively low level.

There are also many smaller foundries that deal in ferrous metals as well as non-ferrous metals. Consideration of dioxin discharges from foundries that process scrap iron are included in the following section.

Non-ferrous metals

Secondary non-ferrous metal foundries process and recover metals and alloys from new and used scrap materials.(See footnote 33) Many of the foundries also deal in ferrous metal products, and there is often no clear distinction between the two.(See footnote 34) Dioxin is mainly discharged from the secondary processing of scrap that may contain organic impurities such as plastics and paint, and from the use of chemicals that contain chlorine.

Estimates of typical dioxin discharges from foundries are very uncertain because the industry is so varied and dispersed, but it is thought to account for about 5% or less of total dioxin discharges to air. However, the proportion could be much higher, and gathering more information about foundry sizes, discharges and practices should be included in a dioxin action plan.

Some foundries will have comparatively high discharges because of the variable nature of the furnace operations and because pollutant control systems are often absent. The installation of a baghouse can reduce dioxin discharges by up to 85%, but it may not be effective in some plants. Other control options are also potentially available.

Cost-effectiveness analysis shows that the economic efficiency of these technical options probably lies between that for waste incinerator options and that for wood-fired and coal-fired boiler options.(See footnote 35) When additional information becomes available, the need to set a voluntary or compulsory upper limit (i.e. a target or a standard) on dioxin discharges for non-ferrous foundries should be reconsidered.

From the few measurements that have been made so far, it appears that the average concentration of dioxin in exhaust gases of non-ferrous foundries in New Zealand is about 0.2 ng TEQ/Sm³, well within the UK limit of 1 ng TEQ/m³.

However, concentration-based limits are not appropriate if the amount of air flowing through the system is variable, as it is in foundries, because compliance can be achieved by increasing ventilation. Any proposed limits for foundries should be mass-based, and measured in units of ng TEQ/unit of throughput; for example, ng TEQ/tonne of raw material. The United States has recently set a mass-based limit on dioxin discharges from secondary aluminium production.

It would be premature to propose a discharge limit for secondary metal processing generally, because very little is known about foundries in New Zealand. However, actions to discourage, or prohibit, certain activities could be taken.

In general, the entry of plastic material into furnaces should be minimised. In particular, the burning of copper wire for reclamation should cease, because copper catalyses the formation of dioxin, and the insulation often contains PVC. This practice can be a significant source of dioxin. Although no precise details are available on the extent of this practice, and any operations are likely to be small scale and occurring without resource consents, available information indicates that this has occurred in the past, and probably still continues. There are alternative mechanical stripping processes available for separating the copper from the plastic insulation, which do not involve any thermal treatment. The proposed action is consistent with regional council air plans that classify the burning of electrical cable as a prohibited activity.

6.3 Other sources

Crematoria

Crematoria account for less than 1% of all dioxin discharges to air, and discharges are likely to decline as more-modern crematoria replace the existing older-style units. New Zealand guidelines already exist for crematoria that specify furnace operation conditions to ensure complete combustion is achieved.(See footnote 36) Although not directed specifically at dioxin, these conditions should minimise their discharge.

It is possible to retrofit dioxin control technologies to crematoria, but the effect on national discharges of dioxin would be extremely small. Moreover, because the concentration of dioxin in the exhaust gases of crematoria is relatively low, and because crematoria are small incinerators, these dioxin control technologies are not nearly as cost-effective as they are on municipal and medical waste incinerators.

Dioxin emission limits have been set for crematoria in the UK and Germany, but a similar approach is difficult to justify in New Zealand. Other options appear more favourable.

Avoiding the entry of chlorinated and other plastics with the casket into the furnace would reduce dioxin discharges. This could be achieved by developing a best practice note to crematoria operators advising, for example, on the optimum operating conditions required to minimise dioxin formation and discharge, including the removal of plastic handles and other superfluous plastic materials before the casket is loaded into the furnace.

Accidental fires

Building fires, vehicle fires, and forest and scrub fires produce about 7% of the total dioxin discharges to air. Dioxin discharges from accidental fires could be reduced if smaller amounts of chlorinated materials were used in building construction, fittings and furnishing.(See footnote 37) More information about dioxin sources and alternative building materials is required before recommending this action. Fire prevention programmes run by the New Zealand Fire Service to reduce the frequency and severity of building fires can be expected to result in a reduction in dioxin discharges.(See footnote 38)

Minor miscellaneous sources

The New Zealand Inventory of Dioxin Emissions identified a number of other sources that discharge dioxin to air. These included cigarette smoking,(See footnote 39) the burning of landfill gas, and chemical recovery boilers at pulp and paper mills. Collectively, these various sources are estimated to contribute less than 0.2% to the total dioxin discharges, and no action is justified.

Footnotes:
26 It is not intended to prescribe control technologies. The use of a baghouse was selected as an example of an available technology, allowing cost-effectiveness analysis to be undertaken. A baghouse provides a high level of particulate control, they are commonly used overseas and are becoming increasingly so.

27 Costs could be of the order of $50,000 to $250,000 per milligram of dioxin not discharged.

28 The burning of PCP treated timber and PCP contaminated wastes would be a significant source of dioxin discharge to air if burned under poor combustion conditions or without appropriate pollution control equipment.

29 Used Oil Recovery, Reuse & Disposal in New Zealand, Ministry for the Environment, Wellington, December 2000.

30 This sets a maximum limit of 1000 milligrams per kilogram for halogens; Guidelines for the Management and Handling of Used Oil, Ministry for the Environment, Wellington, December 2000.

31 In practise, this amounts to people burning off-cuts of processed or treated timber products. This type of waste should be landfilled.

32 For example, the new '10 second rule' is aimed at reducing particulate emissions from smoky vehicles. This should also simultaneously reduce dioxin discharges.

33 These include aluminium, copper, lead, zinc and brass.

34 For the purposes of proposed action on dioxin, no distinction is made between ferrous and non-ferrous foundries.

35 Estimates of cost effectiveness range from $2,000 to $30,000 per milligram of dioxin not discharged.

36 Guidelines on the Siting and Construction of Crematoria, Department of Health, Wellington, 1992.

37 PVC, for example, a plastic commonly found in New Zealand buildings, can produce very high emissions of dioxin when burned.

38 The New Zealand Fire Service Commission has adopted as a high level strategic direction a "Focus on fire prevention, fire safety and fire outcomes".

39 Although smoking leads to dioxin directly entering the lungs, there is no evidence that this source and pathway is an important route of exposure. New Zealand research has found that there is no significant difference in the concentration of dioxin TEQ in the breast milk of smoking and non-smoking mothers.