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Where does our waste go?—— A Visit to SENT Landfill

There are three strategic landfills in Hong Kong, namely, the West New Territories (WENT) Landfill, the South East New Territories (SENT) Landfill and the North East New Territories (NENT) Landfill. They are our current key waste disposal sites. How to operate a landfill? How exactly does a landfill handle a large amount of waste? How does it manage leachate and landfill gases produced by waste degradation? As these three landfills will be full very soon, are there any solutions?

“Where does our waste go?” was the theme of the visit we co-organised with the Alumni Association of the City University of Hong Kong on June 9 to the South East New Territories (SENT) Landfill located at Tseung Kwan O.  Ms Christine Chiu, former Environmental Protection Officer of the Environmental Protection Department, was invited to do a sharing with the event participants.

After participants arrived at the SENT landfill, they attended an introductory session conducted by the staff. The SENT Landfill occupies an area of 100ha and boasts a capacity of 43Mm³. Accepting only construction waste since 6th January of 2016, this landfill’s daily intake is about 2,500 tonnes.

Leachate is a major concern of landfills.  It is the liquid that has percolated through solid waste. The source of the liquid is primarily the water already present in the waste and any water induced from an external source such as rain water and ground water. Actually, the organic waste that SENT landfill collected before 2016 is still decomposing and excreting leachate to this day. The landfill uses an impermeable liner collection system to collect leachate. Composed of multiple layers made of different materials, the liner layers filter the leachate. The pipes that are entrenched near the bottom of the liner layers lead the leachate to a holding tank, so that untreated liquid could be trapped within the landfill area. The temporary leachate lagoon of the SENT Landfill was very large, almost equivalent to the size of 40 standard-size swimming pools. Another issue the landfill has to handle is landfill gases produced by waste degradation. These gases include methane which is harmful to our health and the environment. Facilities are installed at the landfill to recover gases for beneficial uses or proper treatment. 

After the introductory session, the SENT Landfill staff guided participants in a tour to the tipping area. As the shuttle bus moved along, participants could see the various facilities mentioned by the staff earlier. The smell of the waste was not as strong as imagined because this landfill does not accept organic waste anymore and has adopted odour mitigation measures, including the use of odour neutralizers. Landfill staff also cover the waste with soil to take away the smell, as well as to avoid water seepage. While the participants were looking at the tipping area, the guide suddenly pointed at the hill, telling us that once the waste reaches a certain mark, this landfill would be full. This startled everyone and we all realized what “will be full soon” really meant to the landfill.

The staff explained the operation of the landfill, but the more important question was how to solve the problem that our landfills would be full soon. Apart from building incinerators, what else can we do? After the tour, participants went to the City University of Hong Kong to continue with the discussion. Under Christine’s guidance, the participants brainstormed on how fast fashion, bottled drinks, gift packaging and cell phone products affect our environment. Then Christine showed everyone Hong Kong’s carbon emissions data in relation to our daily living, explaining how consumerism has led to global warming and how Hong Kong is being affected.  The issue of climate justice (ie. we consume, people from poor countries suffer) was also brought up and  Christine reminded us how consumer behaviour could affect the environment, and offered tips on carbon reduction. She hoped that everyone could start changing his or her lifestyle and play a part in reducing waste and carbon emissions.