Drainage Services Department - Sustainability Report 2014-15

Managing the Environment / Energy Management and Emission Control

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Sub-sections in Managing the Environment

[Blue-Green Infrastructure] [Energy Management and Emission Control] [Water Resources Management] [Odour Management] [Green Office]

DSD puts strong focus on environmental management in every project it delivers in order to make Hong Kong a livable city. In recent years, we actively campaigned for Blue-Green Infrastructure, emphasising the protection of river ecosystems in addition to environmentally friendly construction practices. These initiatives, alongside various emissions reduction and energy conservation measures at our facilities, are instrumental in promoting sustainable development in Hong Kong.

Energy Management and Emission Control

DSD operates over 330 STWs and pumping stations which treat more than 1 billion cubic metres of sewage annually. Energy consumption of these facilities will lead to indirect emission of greenhouse gases and speed up climate change. In recent years, DSD has strengthened energy management and emission control to alleviate greenhouse effect. Since its establishment in 2007, the Energy and Emission Management Team has implemented various energy-saving measures. Apart from a better use of renewable energy and the electricity generated from biogas (a by-products in sewage treatment), we also introduced high-efficiency wastewater treatment technology to further reduce the demand on fossil fuels.

Carbon Auditing

We conduct regular carbon audits for our plants to identify the main sources of greenhouse gas and reduce the emissions accordingly by lower energy consumption, enhanced efficiency, use of renewable energy etc. We plan to extend carbon audit to more plants and construction projects in future with a view to further reducing our carbon emissions by appropriate carbon reduction measures.

Carbon Footprint in 2013 (in tonnes-of-CO₂ equivalent)¹

		Scope 1		Scope 2
Name of plant	Total emissions²	N₂O emissions through nitrogen removal	Emissions generated from direct combustion of fuels	Indirect emissions generated from the use of electricity	Others³
Stonecutters Island STW	39,589	0	9	38,996	585
Sha Tin STW	22,138	801	3,271	17,991	74
Tai Po STW	11,481	368	14	11,019	79
Shek Wu Hui STW	8,441	377	1	7,990	73
Stanley STW	2,561	33	3	2,518	6
Northwest Kowloon PTW	1,219	0	0.2	1,215	4
Sai Kung STW	1,452	16	6	1,433	3

(1)	The above table shows the carbon emission data from 7 major STWs of DSD. During the reporting period, these 7 STWs treated over 50% of sewage treated by DSD. DSD does not conduct carbon audit for its head office for the time being.
(2)	Totals may not add up due to rounding.
(3)	Included net Green House Gas emissions associated with tree planting, refrigeration, sludge digestion, fresh water consumption, and paper waste disposal.

Implementing Various Energy Conservation Measures

In the past eight years, we succeeded in conserving over 12.5 million kilowatt-hours of electricity through various measures (equivalent to reducing 8,750 tonnes of CO₂ emission4), including the installation of combined heat and power (CHP) facilities at STWs, and replacement of florescent lamps in plants and outdoor lights with LED lamps and induction lamps respectively.

In 2014-15, the CHP systems in Sha Tin STW and Tai Po STW saved 350,000 kilowatt-hours and 680,000 kilowatt-hours of electricity respectively. The result is encouraging.

(4)	The emissions is quantified using a territory-wide default value of 0.7kg / kilowatt-hours

Use of Renewable Energy

Installation of Photovoltaic Panels in Sewerage Facilities

Photovoltaic (PV) systems are installed in Yuen Long STW, Shek Wu Hui STW, Sandy Bay Preliminary Treatment Works (PTW) and Stonecutters Island STW to provide electricity for the plant equipments. The total capacity of electricity generation by these PV panels reaches 153 kilowatts, thereby contributing a total electricity output of 135,000 kilowatt-hours per annum.

By 2017, DSD will install PV panels at six STWs, including:
- Sha Tin STW;
- Tai Po STW;
- Shek Wu Hui STW;
- Stonecutters Island STW;
- Siu Ho Wan STW; and
- Central PTW.
Total capacity of electricity generation: 1,162 kilowatts.
In particular, the PV system at Siu Ho Wan STW will have a capacity of 1,100 kilowatts and will be the largest of its kind in Hong Kong. The project was commenced in February 2015 for completion by 2016.

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PV panels at Sha Tin STW

Energy Conversion from Biogas

CHP generators and Micro-turbine systems are installed in our facilities to generate electricity from biogas produced by the sewage treatment process so as to improve the overall energy efficiency of the process. As of March 2015, the capacities of electricity generation at each STW are as follows:

Location	Type	Electricity generation capacity
Sha Tin STW	CHP generator	1,400 kW
Tai Po STW		1,255 kW
Shek Wu Hui STW		635 kW
Yuen Long STW	Micro-Turbine engine	30 kW

Electricity Generated from Biogas

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In 2014-15, about 28 million kilowatt-hours of electricity were generated from biogas, which is about 12% increase as compared with 2010-11.

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CHP generator at Sha Tin STW

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High-voltage switchgear for CHP generator at Sha Tin STW

Use of Electric Vehicles

Electric vehicles (EVs) have zero emission and can help improve roadside air quality in Hong Kong. In March 2015, our fleet has a total of 16 EVs, which is twice as many as two years ago. Through gaining more experience, we plan for a wider use of EVs in future.

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EV at Sha Tin STW

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