The pros and cons of incineration

This was originally published as a five part series in the Nation newspaper in March 1997.
It examined the advantages and disadvantages of incineration for Barbados and came against the background
of a raging debate on where to put the island's next landfill or whether there should be some other method of disposal

Some observers believe that incineration is inevitable in Barbados because of the dwindling availability of land for landfills and the fact that the two major political parties are committed to incineration.

Government officials said they had received about 40 proposals from local and foreign private companies seeking to build a number of alternate waste disposal systems, including incinerators, pyrolysis and thermolysis.

This article looks at some of the major issues that are likely to surface, should the greenlight be given for the construction of a national incinerator. Some of these issues include the cost to build and to operate it, as well as the impact it can have on human health and the recycling industry.

Abroad, environmentalists have been waging a strong battle against this method of disposal, pointing particularly to the health impacts, such as pollution by dioxin - an unwanted by-product of chlorine - formed in incinerators and which causes cancer, affects the functioning of hormones, and damages the immune system.

Types

Incinerators today include generation of electricity. These are known as Waste-To-Energy (WTE) or Energy-From-Waste (EFW) facilities. The incinerator is lit by regular fuel and the fire kept going by the garbage which burns 24-hours daily, reducing the need for imported fuel. A 250-tonne per day incinerator can generate about 6.5 megawatts of electricity daily (about one-tenth of what the Barbados Light and Power generated last year), and can save about $3 million to $5 million in fuel annually.

It can cover capital and operating costs by selling electricity and by charging a tipping fee, similar to what will be done at Greenland. The cost to build the incinerator is far higher than a landfill and was therefore disqualified by the consultants who were hired to come up with a least cost solution to Barbados' solid waste management problems.

Proponents argue that incineration is cheaper in the long term.

An incinerator can last 20 to 40 years as compared to Mangrove Pond which is being closed after five years and Greenland which is projected between ten and 20 years.

There are two types of incinerators, one which burns everything up front and takes out recyclables afterwards (metals would not be in good shape). The other removes the recycables before incineration which reduces wear and tear on the furnace, but more expensive because it requires more manual labour.

In both designs, the garbage is stored in a pit. A crane then picks it up and dumps it into a furnace. As it is incinerated "bottom ash" falls into a receptacle to be transported to the landfill. This ash is usually non-toxic, if temperatures, at which chemicals are destroyed, are maintained, though the World Health Organisation has reported instances of traces of toxic chemicals in bottom ash.

Flue gases (air emissions) from the furnace passes through a scrubber where it is sprayed with lime to remove sulphur dioxide and hydrogen chloride. The flue gas is then channelled to a baghouse, where "fly ash" which contains the pollutants is trapped, before being released through the smoke stack into the atmosphere. The final emissions are virtually invisible but small quantities of pollutants may still be released. This method drastically improves the quality of the emissions with 99.9 per cent efficiency.

Incineration reduces the volume of garbage by about 90 per cent. The ten per cent of ash is usually buried in a landfill, though some countries are doing revolutionary things with the ash, such as vitrifying it for creation of artificial reefs or mixing it with clinker to make cement.

World turning to burning

Incineration of regular garbage has been routine for over a century in Europe, Japan and the United States.

In the 1950s, when energy costs skyrocketed, countries on both sides of the Atlantic went in different directions. Europe and Japan used energy recovery in their incinerators and incorporated them as part of their central heating systems for cities and located them near population centres. Today, 50 per cent of solid waste incinerated in Sweden produces eight per cent of the country's heating needs. This is projected to rise to ten per cent using 70 per cent of their solid waste.

The US, on the other hand, started closing down incinerators in the 1950s and 1960s mainly because of polluted flue gas emissions. The cost of installing pollution control devices was too high, and at any rate, it was not a priority because there was an abundance of land to use for landfilling. In addition, they were not aware, at that time, of the negative impact of landfills on the environment. Also, energy recovery was not a priority because the cost of energy was low in the US. However, when the global oil crisis of the 1970s struck, the US was back into the incineration market with emphasis on energy recovery.

Today, Europe is moving away from landfills towards recycling and incineration. Many members of the European Union are either prohibiting the dumping of incinerable materials in a landfill; imposing levies on top of tipping fees to encourage recycling, reuse and incineration; banning compost material from landfills by the year 2000; permitting disposal of materials with only three per cent or less carbon; or, passing laws to encourage the construction of incinerators.

Recycling

The impact on the recycling industry depends on whether recyclable material is taken out before or after incineration.

In virtually all cases, glass and metals will be recovered and those industries will remain untouched.

The plastics and paper products are another matter. On the world market, the price of paper and plastics for recycling has plummeted. Paper, for example, which in the early days used to fetch US$270 per tonne is now attracting no more than US$40 per tonne which barely pays for local collection.

At least two local companies which deal in paper and plastics are feeling the crunch and are in danger of closing operations. If they close, it will mean that thousands of tonnes of paper and plastics will be headed for Greenland, increasing the volume of garbage than what was envisioned and shortening the lifespan of that facility. One of the companies is expected to pull out of Barbados to a neighbouring Caribbean island where the Government has offered generous concessions for a paper recycling operation.

'Dumps pollute more than burning'

The problem with landfills is that they can pollute the underground water by leaching toxic substances from certain types of garbage, into the ground. The situation is worsened when rain falls on the landfill and quickens the flow.

Engineers have since designed impermeable landfill liners and leachate collection tanks to deal with this, but in 1994 the United States Environmental Protection Agency revealed that landfills posed a bigger threat to air quality than to ground water.

In England, the Royal Commission on Environmental Pollution 17th report, Incineration of Waste , studying emissions of greenhouse gases, confirmed that landfills were responsible for much more air emissions with adverse global consequences than incineration. This has led to many European governments favouring incineration over landfilling.

In addition, findings from a 1994 lawsuit in the United States showed that a WTE facility was more environmentally friendly than a landfill. The study, which compared a 1 500 ton-per-day (TPD) WTE facility with a 1 500 TPD landfill, measured higher emissions of hydrocarbons, non-methane organic compounds, hazardous air pollutants, nitrogen oxides and dioxin and furans from the landfill than from the incinerator.

The only gas that the incinerator spew more than a landfill was carbon monoxide - 1 290 tons over the WTEs 30 year lifespan compared to 3 094 tons during the 130 year lifespan of the landfill. (The lifespan of the landfill was 30 years with another 100 years given to biodegradation of garbage after closure.)

The 1995 Stanley Environmental Impact Assessment for the Greenland landfill did not identify the potential gases which Greenland or Mangrove Pond would emit, but said that three major typical landfill gases were methane (47.5 per cent), carbon dioxide (47.5 per cent) and nitrogen (3.7 per cent). It did not mention dioxin as a landfill gas. Other gases mentioned included oxygen, aromatic and alkane hydrocarbons, hydrogen, carbon monoxide, hydrogen sulphide, ammonia and various volatile organic compounds.

The three major gases are normally present in the atmosphere and not a problem to human health, however a methane build-up can be explosive when mixed with air. The report recommended methods for monitoring and minimising production of landfill gases for Greenland.

Dioxin - cancer-causing pollutant

The chemical dioxin was first discovered in an old incinerator in the United States in 1978 and later at other incinerators throughout the country.

Countless studies were launched to determine the health and environmental impact of dioxin, and in the last 20 years it became one of the most studied chemicals in the United States. It is one of the several pollutants produced by an incinerator, and by far the most fearful because it is a cancer-causing, hormone altering chemical.

There is a great debate about the quantities of dioxin that are produced, whether there are "safe limits" and what these limits should be. Dioxin is made up of a family of 210 compounds (75 dioxin and 135 furans) which are accidental by-products of the chlorine industry. Compounds related to dioxin, and believed to be as harmful, are chlorinated dibenzodioxins (CDD), chlorinated dibenzofurans (CDF) and polychlorinated biphenyl (PCB). They are collectively called dioxin (polychlorinated dibenzo-para-dioxin or PCDD).

Dioxin is created in many different processes, such as in incinerators which burn regular household garbage or medical waste, as well as power companies that burn fuel to produce electricity. A forest fire can produce large quantities of the chemical, which is also formed during chlorine bleaching of wood pulp that is used to make paper or it can be found in vehicle exhaust emissions. In addition, the toxin can also be produced during the process of treating sewage sludge with chlorine to kill bacteria. It can also be produced by landfills.

Dioxin is formed through molecular re-arrangement. During combustion, when the chlorine molecules in chlorinated materials, such as paper, wood and plastics, split apart and interact with organic material, dioxin forms. Greater amounts of dioxin will be formed if a heavy metal, such as copper or zinc is present. If temperatures higher than 1500°F are achieved throughout the furnace for at least half a second, organic compounds in the gases will be destroyed, preventing the formation of dioxin.

In modern incinerators, even with a 99.9 per cent efficiency, trace amounts of organics do escape, leading to the formation of dioxin. The chemical is actually formed in the smoke stack, between 650°F to 300°F, when the flue gases (emissions) are being cooled. Modern WTE incinerators use a cooling device in the smoke stack and under ideal conditions, the temperature would change instantly and no dioxin would be formed. However, dioxin is formed as those ideal conditions are not always achieved.

Dioxin is hydrophobic, meaning that it will not dissolve in water, and therefore has to piggyback on various materials to be transported. This is why scientists call it a "stable" material, because it cannot easily be washed away.

Modern incinerators much safer

Since the discovery of dioxin in an incinerator in 1978 in the United States, there was much hysteria about the potential health impact of the chemical family, one member of which is a Class 1 human carcinogen (cancer-causing) and a proven teratogen (causes deformation in foetuses).

In animals, it disrupts hormones and affects the immune system and it is believed that the same might occur in humans, but there is no evidence, yet. There were two well-documented cases in which people ingested the chemical along with a few other incidents involving accidental exposure, which resulted in short-term health effects but no deaths (see box).

The World Health Organisation (WHO) in 1989, after examining several cases of exposure, was unable to reach a decision on the impact on human health. It said that the uncertainties were too great but recommended that "exposure should be reduced to levels as low as are reasonably practicable".

On February 14, 1997, the International Agency for Research on Cancer announced that it was declaring the most potent form of dioxin (2,3,7,8-tetrachlorodibenzo-para-dioxin or TCDD) to be a Class 1 human carcinogen. All the examples, however, of the health impact to people in Missouri, Nitro, Seveso, Yucho and Yu-cheng were extreme cases where they were exposed to levels in far greater concentrations than what a modern incinerator was likely to emit.

Levels

An incinerator today, equipped with proper environmental controls, will emit mere specks of dioxin compared to what these people were exposed - as much as one pound of TCDD.

"Safe" limits vary from country to country and even from agency to agency in the United States, but in each case, they are all equivalent to mere specks of dust. Sweden has the toughest regulations, limiting dioxin emissions to 0.1 nanogram per cubic metre (one billionth of a gram). In the US, the Environmental Protection Agency set a standard of 0.006 picogram (trillionth of a gram) per kilogram of body weight while the Food and Drug Administration's limit is 167 times higher. Canada accepts 10 picograms per kilogram of body weight, which is 1 667 times greater than the USEPA limit.

There are two schools of thought on whether there is a "safe limit" for exposure to a toxic chemical.

Environmental activists, such as Greenpeace, argue that as long as the chemical is toxic, there is no safe limit. But regulatory health and environmental agencies say that despite how toxic the chemical is, the health impact depends on the quantities, the length of time and the frequency that people are exposed to it. For example, the chemical atropine is extremely poisonous, a mere 10 milligrams can kill a child but a smaller dose is an antidote to treat people poisoned by certain pesticides or nerve gas.

In Barbados one also has to place incineration in context of what already happens in the environment. Is dioxin being spewed from the incinerators at the Queen Elizabeth Hospital or the Bridgetown Port or from the Barbados Light and Power smoke stacks at its Spring Garden generating plant? How much dioxin billows into the sky and lodges in the surrounding plants, trees and grass every time a wooden house goes up in smoke? How much dioxin has covered Arch Hall, Bennetts and surrounding villages when the Mangrove Pond landfill was on fire? Is there any dioxin continuously being produced by the landfill? Does a cane fire produce dioxin? Do these things spew more dioxin into the air than a modern incinerator will emit in its 30 or 40 year lifespan?

Studies suggest that a modern incinerator, (which removes 99.9 per cent dioxins and other pollutants), burning 416 000 tonnes of garbage per year (four and a half times what Barbados is likely to burn) will produce about 0.431 grams of dioxin per year.

Though the research seems to favour incineration in developed countries, the data must be carefully assembled and studied to determine the level of dioxin that already exists in the local environment, how much higher an incinerator will push it or whether it must first be reduced from all sources before incineration.

If incineration is chosen, it will have to be a policy decision, just like Greenland was, and then attention will have to be turned to ensuring that the levels of dioxin and other pollutants are kept to negligible quantities.