There has been considerable brouhaha over Hong Kong’s waste strategy, especially plans to expand three landfills plus build an incinerator on an artificial island by Shek Kwu Chau – which passed two votes in the Legislative Council, but were then delayed, with the Finance Committee now set to vote on the plans in autumn.
While there is agreement on the wisdom of eventually reducing and even halting use of landfills, controversy swirls over ideas for heavy reliance on incineration. Arguments span issues such as locations, aesthetics, and costs. But what does science say?
First, remember that adopting incineration to reduce the volume of waste sent to landfills is not a new idea for Hong Kong. This was a strategy adopted from the late 1960s, leading to four waste incineration plants being built. Yet to the Environmental Protection Department (EPD), science showed incineration was a threat to human health.
“Incinerators are a major source of pollution in the urban areas,” reported a 1989 government white paper on pollution. “They account for approximately 18% of all respirable particulates emitted into the atmosphere of the territory and can be a source also of trace quantities of highly toxic substances.” The incinerators were phased out, with the last of them – at Kwai Chung – ceasing operation in 1997.
Recently, there has been a remarkable about face in the EPD’s attitude to waste incineration. This is exemplified by assistant director Elvis Au, who has boldly claimed that in the planned incinerator, high temperatures of at least 850°C can completely destroy organic pollutants.
Alas, this claim is not true. The chemistry of incinerators is complex, and their emissions may include 200 or more kinds of organic compounds, including known carcinogens. It appears Mr Au was misled into only considering dioxins, which are the most notorious toxins formed during combustion, and should indeed be destroyed at temperatures above 850°C, though can reform as chimney gases then cool.
Modern incinerators do tend to emit less dioxins than those in the past, but the particulates that the EPD was formerly concerned about are still an issue. It’s extremely hard to filter them out, especially the ultrafine particulates that can carry heavy metals and toxic molecules deep into the lungs, and even pass through lung tissue to enter the bloodstream.
We’re blithely reassured that the incinerator emissions will be within European Union standards. An environmental impact assessment included “detailed calculations” of these emissions, though to me – even with a PhD in physical chemistry – these look superficial, and more like gobbledegook than science.
Here, science would call for a pilot scheme, using actual Hong Kong waste, before building what would be one of the world’s largest incinerators. Yet the only recent waste incineration trials here have been by Green Island Cement, for a project given the thumbs-down by the EPD despite apparently strong results.
A pilot scheme would seem especially important given that even relatively new incinerators have been found to create significant air pollution. For instance, a large Dutch incinerator lauded by the EPD ranks among the top 500 polluters in Europe. Also, research into health effects of incinerators has found impacts such as premature births in Italy, increased deaths from cancer in Spain, infant deaths in Japan, and urinary tract birth defects in France.
This research was not mentioned in the environmental impact assessment, which merely asserted there would be no “unacceptable” health impacts. The assessment writers seemed fond of describing potential impacts to species like the endangered finless porpoise, along with fisheries and landscape, as “acceptable” – a vague, unscientific term.
While incineration reduces waste volume, it can’t make waste magically disappear. Whatever does not go out through the chimney, stays behind as ash. As well as bottom ash from beneath the fire, there is fly ash from the chimney and the filters – and this can be highly toxic. According to the British Society of Ecological Medicine, “Fly ash contains very high concentrations of dioxins (over 98% of dioxins produced by an incinerator) and heavy metals making it some of the most toxic material on the planet.”
Plans call for the ash to be dumped in a landfill north of Tuen Mun. However, this will soon be full. So where to put it afterwards? Jim Middleton, chairman of Clear the Air, noticed a planned reclamation site south of Cheung Chau, and suggested there might be ideas for making this an ash dump, much as Singapore disposes of its incinerator ash in an artificial island. Maybe so; I’ve heard the idea mentioned elsewhere.
Though seemingly convenient, dumping in an artificial island would be scientifically outrageous. After all, it’s inevitable that toxins will eventually leak into the sea, and a major typhoon with storm surge could scour and scoop out the ash, poisoning southern waters.
“Enough scientific nay saying already!” you may exclaim. “Environment secretary KS Wong says Hong Kong has no Plan B for waste, so there are no alternatives.”
Don’t despair so fast. There are alternatives a-plenty.The most futuristic of these is plasma arc gasification, which Scientific American featured among 20 ideas for making our planet cleaner, healthier and smarter. This involves the use of plasma torches to heat fuel made from waste to temperatures of over 1000°C – blasting organic molecules apart. This produces a relatively simple gas mixture, called syngas, along with a glassy, rock like material.
The syngas can be cleaned, to remove chlorine, then used in various ways like combustion to generate power, or creating jet fuel. With such versatility, along with minimal emissions and zero ash, the scientific case for plasma arc gasification is strong. Unsurprisingly, several projects are in progress or planned worldwide – though not in Hong Kong.
Less “sexy” but also scientifically sound options for dealing with waste include putting food waste through the Stonecutters sewage treatment facility.
But science can also help take a broader view of the situation. With resources like oil and rare metals increasingly scarce worldwide, plus concerns over global warming, there is clearly a strong case for having less waste in the first place, and making far better use of things we do throw away. Social science might be more useful than highfalutin physics or chemistry here, such as helping determine whether a mix of waste charging and deposits on plastic bottles can help steer Hongkongers towards sustainability.
Yet waste reduction and recycling seem like minor considerations here. Given the major issues with incineration and landfills, plus the range of alternatives, it’s clear that Hong Kong’s waste strategy is not scientific.