Society always has been searching for the perfect way to make our wastes disappear. For-tunately, collection systems have be-come more sophisticated than the days when people depended on scavenging animals to remove wastes from their caves.
Since today's wastes are much more complex than the materials discarded hundreds of years ago, in-novative technologies are needed to pre-treat wastes and reduce their volume and potential to pollute. Hong Kong, for example, has taken some concrete steps to prepare for the future.
The British protectorate of Hong Kong, which is due to revert to Chi-na in 1997, is small in size. It in-cludes Hong Kong Island, mainland Kowloon and the New Territories which reach up to the Chinese border, as well as several other islands, the largest of which is Lantau. To al-leviate the severe overcrowding and housing shortages in some areas, the government has been trying to establish new towns in more rural, undeveloped areas.
In 1983, Hong Kong's Environ-mental Protection Department (EPD) became one of the first authorities in the world to use computer-based planning models to evaluate waste disposal options.
In 1989, the Hong Kong government outlined the region's strategy to waste management in its Waste Disposal Plan. The plan relies on an extensive network of waste transfer stations and large, rurally-located landfill sites to serve expanding disposal needs.
The decision to rely strictly on landfills stems back to localities' concern over three old, polluting in-cineration plants. In the past, 35 percent of Hong Kong's municipal solid waste (MSW) was sent to urban incineration plants; two plants have recently closed and the third will close in 1997.
In view of Hong Kong's high residential population density, rapid ec-onomic growth and premium land prices, it may seem illogical to base future waste disposal strategy en-tirely on landfills. But Hong Kong's Environmental Protection Depar-ment, which is responsible for implementing the program, is already proving otherwise. The territory's 6 million inhabitants, in addition to the 7 million annual visitors, will be able to reach their own conclusions shortly.
Waste Arisings Hong Kong's waste stream in 1993 was approximately 20,000 tonnes a day; approximately 8,500 tonnes a day were municipal waste. Munici-pal solid waste is expected to in-crease to 13,000 tonnes a day by the year 2006.
An estimated 500,000 tonnes of waste were recycled in Hong Kong during 1993 and 1.3 million tonnes were exported for recycling. China, for example, has been the main im-porter of Hong Kong's waste paper, ferrous scrap and secondary plastics. Although localities have contributed to recycling waste paper, ferrous metal and glass, Hong Kong does not have a recycling target.
EPD reports a two-fold increase in waste quantity between 1983 and 1993. Construction and demolition (C&D) wastes represent a disproportionate amount of the overall waste stream (see chart). For example, be-tween 1983 and 1993, there was a nine-fold increase in construction waste. These increases have placed enormous burdens on existing waste disposal facilities.
Hong Kong's best chance to reduce the volume of wastes for disposal is within the C&D sector. The C&D in-dustry offers other opportunities for environmental im-provements including reducing the importing of tropical hardwoods to Hong Kong which are used for shuttering and formwork in concrete construction, and then are discarded.
In the future, a fee will be charged to dispose of commercial wastes. The country hopes that this will serve as an incentive for businesses to reduce their waste output. For now, household wastes will be handled for free.
Selecting The Sites A main part of Hong Kong's solid waste strategy is three new landfills which are reportedly among the largest sites in the world; together, they can accommodate more than 140 million tonnes of wastes.
Selecting the sites, however, was a lengthy process. An estimated 75 percent of Hong Kong is too mountainous to be used as a landfill. Climate is another important consideration. Heavy rainfall, especially during monsoons, re-quires extra allowance for surface water drainage, and a typhoon can effect refuse stability on slopes.
Hong Kong's MSW contains an above average moisture level due to the high organic content in a typical diet. The country's hot climate degrades the organic wastes more quickly which, together with the high rainfall, allows more opportunity for the leachate to generate.
Each of the new strategic landfills has been designed and constructed by a consortia of private sector waste disposal firms, which will also operate the sites and restore them on completion. The contractor will remain responsible for the site and its maintenance for thirty years after the waste deposition ends, a first for Hong Kong.
Environmental quality guarantees have been required, as well as financial security through bonds. The bonds have been lodged by contractors, who also were monitored during construction to ensure environmental compliance over groundwater, noise, pollution and dust.
Of the territory's original 13 landfills, 10 have been closed and the remaining three (Tseung Kwan O, Shuen Wan and Pillar Point Valley), as well as the remaining in-cinerator at Kwai Chung, are close to exceeding capacity. Other disposal and treatment sites, such as the Kennedy Town Incinerator and a pilot compost plant, have closed within the past three years.
The Winning Sites The territory has an efficient local scavenging network through which building management employees and street scavengers remove and sell valuables such as aluminum cans, clean paper and cardboard before they are delivered to Refuse Collection Points (RCPs). RCPs are dotted around Kowloon on the mainland and Hong Kong Is-land.
This series of localized collection points will feed a network of new transfer stations which will feed the three new landfills. A single transfer station can manage the waste from approximately 800,000 people, and siting the transfer stations in urban areas reduces traveling time.
The first landfill was commissioned in West New Ter-ritories (WENT), where it began receiving wastes in No-vember 1993. The WENT landfill is located at Nim Wan, Tuen Mun. The site has an estimated capacity of 61 million cubic metres and an approximate lifetime of 25 years.
Containerized, compacted wastes will come into the site from transfer stations. The Environmental Protection De-partment has made plans to maximize sea transport of wastes to the transfer stations. Computerized weigh bridges will be used to record waste input.
The WENT site is lined with two 2mm thick high-density polyethylene liners enveloping a 6mm thick bentonite matting and includes a leachate collection system. Leachate will be collected and treated before it is discharged into the public sewers.
Landfill gas management at the site includes an active gas extraction system. As gas is generated, it will be flared off or used to produce pow-er. Continuous environmental monitoring of the site will be conducted. Future plans include using the site as a recreation area after it is closed. The closure, however, will require a 1.5 metre thick cap.
The South East New Territories (SENT) landfill site was commissioned in 1994 and will be located in Junk Bay at Tseung Kwan O. A small on-site village, along with its 150 residents, were relocated while 50 hectares will be reclaimed from the sea. Sites constructed adjacent to the sea or, as in this case, re-claiming land from the sea, require certain precautions to prevent lea-chate from migrating through the sea wall.
SENT, which is slightly smaller than WENT, has an estimated lifetime of 13 years and an approximate capacity of 39 million cubic metres.
The site will accept between 6,000 to 8,000 tonnes a day of commercial and industrial wastes from Hong Kong Island and Kowloon and the municipal solid wastes from adjacent areas. When completed, the SENT landfill site, which is being constructed in the curve of a bay, will be over 100 metres high.
The last site, located in the North East, is known as the NENT landfill. The contract has been awarded and the site is expected to open in mid-1995. NENT's site should serve the region for 17 years with its estimated 35 million cubic metres capacity.
Transfer Stations Feeding these landfills are Hong Kong's fully-enclosed transfer stations, which will process 1,000 to 1,800 tonnes per day of refuse.
Before leaving the transfer stations, all bulk hauling vehicles will be washed. To reduce road transport impacts, transfer stations north of Hong Kong Island and one on Lan-tau Island will take compacted waste by barge to the WENT landfill site (see center picture on page 80). How-ever, alternative modes of transportation will be necessary for emergency situations such as typhoons.
The Kowloon Bay transfer station was the first of the region's new generation of privately operated transfer stations to go into operation. The two story plant can handle 1,800 tonnes of MSW a day. During Chi-nese New Year, the daily throughput can expand to more than 3,000 ton-nes. Kowloon's waste presently is de-livered to a landfill in the New Ter-ritories, but will be transported by road to NENT once it opens.
Using two self-propelled marine vessels, the Island East Transfer Station at Chai Wan provides the territory's first sea transfer of compacted waste. Constructed in 1991, the facility's 15 year operational contract includes replacing the open barges that had littered the Hong Kong harbor while carrying waste. The 1,200 tonnes-per-day plant also includes dust and odor filtration systems and a wastewater treatment plant.
Incoming waste to the two story Is-land East Transfer Station is tipped from the top level into hydraulically operated pits below. The waste is then compacted into 6 metre long containers. A total of 85 containers, each weighing about 14 tonnes, are stacked onto the marine vessels to be transported to the WENT landfill site.
The third transfer station is al-ready operating at Sha Tin. The current intake of Sha Tin is approximately 800 tonnes but will even- tually handle 1,200 tonnes per day.
Swire BFI Waste Services has the contract for the WENT landfill and the first three operational transfer stations. Four more sites will be commissioned in early 1997. The future sites will include: Island West (1,000 tonnes per day), West Kow-loon (2,500 tpd), North West New Territories (1,100 tpd) and the Out-lying Islands plant (600 tpd including construction waste). A station on North Lantau Island will be complete by mid-1997 and the last scheduled station, Tai Po, is expected to be op-erational by 2000.
Despite high technological standards, the region's new landfill sites are expected to cost Hong Kong less than the old ones.
The Environmental Protection De-partment is studying waste management strategies that will conserve airspace and reduce volumes and the toxicity of wastes. Specialists such as environmental consultancy ERM are evaluating options on be-half of the the Environmental Pro-tection Department. Educational programs to support waste reduction and recycling also are envisaged.
Although major political changes are in store for Hong Kong, they should not be allowed to eclipse the equally major changes currently be-ing wrought in the territory's waste management policies.