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ME2902

Supplementary Notes

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Global Environmental Problems

• Thawing of permafrost to be ‘major factor’ in global warming, warns UN report.

• 27 November 2012 – Massive stores of carbon trapped under the northern hemisphere’s frozen expanses risk being unleashed and significantly contributing to global warming should thawing of the region’s permafrost continue to accelerate, a United Nations report warned today.

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Permafrost

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Global Environmental Problems• Released on the sidelines of the UN Climate Change

Conference in the Qatari capital of Doha, the UN Environment Programme (UNEP) report – Policy Implications of Warming Permafrost – underlines the potential hazards facing global ecosystems as well as national infrastructures if the rigid permafrost terrain were to become unstable.

• It also warns that the threat posed by carbon dioxide and methane emissions from warming permafrost has only begun to enter mainstream scientific discourse in recent years and, as a result, has not been included in climate prediction modelling.

• In a news release marking the report’s launch, Achim Steiner, the Executive Director of UNEP, emphasized the role permafrost could play in rapidly increasing the effects of global warming.

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Global Environmental Problems• “Permafrost is one of the keys to the planet’s future

because it contains large stores of frozen organic matter that, if thawed and released into the atmosphere, would amplify current global warming and propel us to a warmer world,” Mr. Steiner(Executive Director of UNEP) noted.

• Most of the planet’s permafrost formed during the last ice age and extends up to 700 metres in parts of Russia and Canada. It constitutes an active layer of up to two metres in thickness sitting atop a stratum of frozen soil.

• Although permafrost regularly thaws each summer and refreezes in the winter, an increase in thickness of the active layer due to global warming would cause huge quantities of organic matter trapped in the frozen soil to thaw and decay, releasing massive amounts of carbon dioxide.

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Global Environmental Problems

• The report’s finding that permafrost emissions could ultimately account for up to 39 per cent of total global emissions have prompted UNEP and the report’s authors to urge action at the Doha climate conference.

• “The release of carbon dioxide and methane from warming permafrost is irreversible: once the organic matter thaws and decays away, there is no way to put it back into the permafrost,” the report’s lead author, Kevin Schaefer, noted.

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Global Environmental Problems• UNEP also warns that changes in the permafrost could

have a substantial impact on human activities as the thawing would cause the terrain to become structurally weak and unsteady, ultimately adding to the growing costs associated with public infrastructure owing to climate change.

• With most climate change-related legislation ignoring the threat posed by the permafrost thawing, the report recommends a special assessment by the Intergovernmental Panel on Climate Change (IPCC) as well as the creation of national monitoring networks and adaptation plans as key steps to dealing with the potential impacts of what could be “a significant source of emissions” and “a major factor in global warming.”

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Global Environmental Problems• Mr. Schaefer confirmed that the thawing

permafrost represented a dramatic physical change with potentially huge impacts on human infrastructure networks.

• “Individual nations need to develop plans to evaluate the risks, costs and mitigation strategies to protect human infrastructure in permafrost regions most vulnerable to thaw,” he concluded.

• Site:http://www.un.org/apps/news/story.asp?NewsID=43611&Cr=climate+change&Cr1=

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AN OVERVIEW ON CHALLENGES FOR WASTE REDUCTION AND MANAGEMENT IN HONG KONG

WASTE BY TYPE Municipal Solid Waste (MSW) comprises solid waste from households, commercial and industrial sources. This excludes construction and demolition waste, chemical waste and other special waste. MSW is disposed of at landfills.

• Construction waste includes waste arising from such activities as construction, renovation, demolition, land excavation and road works. Ideally, the waste is separated and inert material is used as fill in reclamation sites, when available. However, a significant portion of the waste still goes to landfills.

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AN OVERVIEW ON CHALLENGES FOR WASTE REDUCTION AND MANAGEMENT IN HONG KONG

• Chemical waste comprises substances specified under the Waste Disposal (Chemical Waste) (General) Regulation as posing a possible risk to health and/or the environment. Chemical waste in Hong Kong is disposed of either on-site where the chemical waste is generated, at the landfill site or at other off-site disposal facilities including the Chemical Waste Treatment Centre (CWTC). All these facilities must be licensed by this department.

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AN OVERVIEW ON CHALLENGES FOR WASTE REDUCTION AND MANAGEMENT IN HONG KONG

• Clinical waste consists of waste generated from various healthcare, laboratory and research practices as defined in Section 2 and Schedule 8 of the Waste Disposal Ordinance. It should be managed properly so as to minimize danger to public health or risk of pollution to the environment. Chemical Waste Treatment Centre (CWTC) is designated as the facility to treat clinical waste.

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AN OVERVIEW ON CHALLENGES FOR WASTE REDUCTION AND MANAGEMENT IN HONG KONG

• Special wastes include animal carcasses, livestock waste, radioactive waste, grease trap waste and waterworks/sewage sludges. These wastes need to be treated separately. Some livestock waste is treated at the Sha Ling Composting Plant. Arrangements are being developed for the proper treatment and disposal of the other wastes, but more time is needed to address community concerns about such facilities.

• Other solid waste comprises dredged mud and excavated materials disposed of at marine disposal sites.

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AN OVERVIEW ON CHALLENGES FOR WASTE REDUCTION AND MANAGEMENT IN HONG KONG

• The EPD manages facilities for collecting, transferring, treating and disposing of a variety of waste types. Since 1989, the department has phased out older, environmentally-unacceptable landfills, restored them to a safe condition and is in the process of developing them for different recreational uses, such as football pitches and golf courses.

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Waste Management Facilities• Three strategic landfills are located in the New

Territories (Nim Wan, Tseung Kwan O and Ta Kwu Ling). Liners, leachate collection and treatment systems, landfill gas management systems, and surface and ground water management systems are in place to control air and water impacts.

• Thirteen closed landfills in Hong Kong are being restored to minimise potential safety and health risks. They are landscaped to provide green zones and can be developed into different public recreational uses such as golf driving ranges and courses, multi-purpose grass pitches, recreational parks and ecological park.

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WASTE MANAGEMENT IN HONG KONG

• Seven refuse transfer stations are located in different areas in Hong Kong. These are centralised collection points for the transfer of waste to the strategic landfills.

• The waste from smaller refuse collection trucks is compacted and transferred into containers, which are loaded onto lorries or barges for shipment to landfills.

• The wastewater, odours and emissions from the stations are all controlled.

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WASTE MANAGEMENT IN HONG KONG• The Chemical Waste Treatment Centre on Tsing Yi Island

opened in 1993. It accepts a variety of chemical wastes and also clinical waste commencing 1 August 2011. It has extensive controls on its emissions which are regularly monitored by the EPD. Chemical waste in Hong Kong is disposed of either on-site where the chemical waste is generated, at the landfill site or at other off-site disposal facilities including the Chemical Waste Treatment Centre (CWTC). All these facilities must be licensed by this department.

The Sha Ling Composting Plant in the northern New Territories opened in 1991 and accepts livestock waste. The waste is composted into soil conditioner for use in Hong Kong.

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WASTE MANAGEMENT IN HONG KONG

• Landfill space should also be conserved by state-of-the-art technologies that reduce the bulk volume of waste requiring disposal. • After extensive review, the EPD is now

planning to develop the Integrated Waste Management Facilities that would adopt advanced incineration as core technology to reduce bulk waste volume and to recover energy.

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Advanced incineration technology• Incineration is a thermal treatment technology used to

reduce the volume of waste requiring final disposal. Incineration can typically reduce the waste volume by over 90% and it is one of the widely used technologies for treating municipal solid waste prior to disposal at landfills. Most modern incineration plants incorporate heat recovery as well as power generation facilities to recover the heat energy in the waste.

• To ensure that the gas emissions meet the stringent standards imposed by regulatory bodies (e.g. EU Waste Incineration Directive) for public health and environmental protection, modern incineration plants adopt a number of advanced design and process controls as well as exhaust gas cleaning measures as illustrated by the flow chart below:

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Advanced incineration technology• Combustion - Waste is continuously fed into the furnace

by an overhead crane. The waste is combusted in the specially designed furnace at high temperature of > 850oC for more than 2 second with sufficient supply of air so as to ensure complete burning of the waste and to prevent the formation of dioxins and carbon monoxide.

• Boiler/ steam turbine - The heat from the combustion is used to generate steam in the boiler. The steam then drives the turbine which is coupled to the electricity generator. The excess heat generated can also be used for other purposes, e.g. heat for swimming pool.

• Site: http://www.epd.gov.hk/epd/english/environmentinhk/waste/prob_solutions/WFdev_IWMFtech.html

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Advanced incineration technology• Exhaust gas cleaning - The exhaust gas from the boiler is

typically cleaned by the following advanced pollution control systems to ensure compliance with the stringent environmental standards:

• Dry or Wet scrubbers – to spray lime powder or fine atomized slurry into the hot exhaust gas to neutralize and remove the polluted acidic gases (sulphur oxides, hydrogen chloride)

• Activated Carbon Injection – to adsorb and remove any heavy metal and organic pollutants (e.g. dioxins) in the exhaust gas

• Bag house filter - to filter and remove dust and fine particulates

• Selective Non-Catalytic Reduction - to remove nitrogen oxides (which is a cause of urban smog) by reacting them with ammonia or urea.

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Advanced incineration technology• Ash residues handling - The ash residues from incineration

generally include bottom ash from the furnace and fly ash from the exhaust gas cleaning units. The bottom ash is either reused as construction material or disposed of at landfills. Fly ash is typically stabilized and solidified by reagents (e.g. cement) and disposed of at dedicated landfill with continuous environmental monitoring. Ash melting that use the heat energy in the incinerator to melt the ash residues at a high temperature is a technology used in some place. The melted products are inert and contain no hazardous materials so that they may be re-used (e.g. as construction material). Comparatively ash melting is more expensive but it has the advantages of further volume reduction and fixation of any hazardous materials in the fly ash.