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[Blue-Green Infrastructure] [Combating Climate Change] [Water Resources Management] [Green Office]
In the 2015 United Nations Climate Change Conference held in Paris in December 2015 national leaders pledged to step up mitigation and adaptation efforts to combat climate change, prompting the Hong Kong Government to pick up the pace and respond to the issue.
In fact, the HKSAR Government first established the Inter-departmental Working Group on Climate Change in 2007, which was led by the Environment Bureau and comprising representatives from 16 departments including DSD. DSD plays a vital role in helping Hong Kong adapt to and mitigate climate change. As we review Drainage Master Plans (DMPs) and improve the city’s flood defences, we take into account the impact of climate change and undertake drainage improvement works deemed necessary. The Department is also dedicated to doing its part in reducing climate change through its many energy conservation and emission reduction measures at its facilities, such as introducing efficient sewage treatment technologies, using renewable energy and utilising biogas for electricity generation.
Climate change is a global challenge, and close liaison with other cities and regions facilitates the exchange of information and experience. DSD is a member of Connecting Delta Cities, a subsidiary of the international organisation C40 Cities Climate Leadership Group, and in this capacity the Department represents the Hong Kong Government to exchange flood prevention experiences with other delta cities. DSD is also a member of the Hong Kong/Guangdong Joint Liaison Group on Combating Climate Change, regularly exchanging lessons learnt in drainage system planning with the provincial government of Guangdong.
DSD will continue to work with various departments and regions on climate change, an issue affecting Hong Kong and the world alike. This chapter sets out the Department’s work on energy conservation and emissions reduction. For more details on Blue-Green Infrastructure and flood prevention work, please refer to Chapter 5: Our Core Responsibilities, and Chapter 6: Managing the Environment - Blue-Green Infrastructure.
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We conduct carbon audits at our plants to identify sources and quantities of greenhouse gas emissions, thereby implementing corresponding measures to lower energy consumption, enhance efficiency and reduce overall emissions. This year, we conducted two new carbon audits and six surveillance carbon audits. In future, DSD will extend these audits to other STWs and construction projects, with further carbon reduction measures undertaken to reduce our carbon emissions and mitigating climate change.
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| (1) | The above table shows carbon emission data from eight major STWs of DSD. During the reporting period, these eight STWs treated over 50% of sewage processed by DSD. DSD does not conduct carbon audit for its head office for the time being. |
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| (2) | Totals may not add up due to rounding. |
| (3) | Including net greenhouse gas emissions associated with tree planting, refrigeration, sludge digestion, fresh water consumption, and paper waste disposal. |
| (*) | STWs that conducted new carbon audits |
Electric vehicles (EVs) run on batteries and thus no petrol is combusted, resulting in zero direct emissions which helps improve roadside air quality in Hong Kong. As of March 2016, we currently have 20 EVs in our fleet with a combined mileage of about 254,000 kilometres during 2015-16. We plan to further encourage the use of EV by identifying suitable locations within our facilities for the installation of medium EV chargers.
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Charging socket at Sha Tin STW
We established an Energy and Emission Management Team in 2007 to improve DSD’s performance in energy and emissions in different ways, including benchmarking performance, implementing improvement measures, and reporting energy-saving results. We have seen excellent results in the reduction of energy usage and carbon emissions at our operations in recent years. By optimising and replacing operational facilities in STWs, installing photovoltaic (PV) panels, switching to light-emitting diodes (LEDs) etc., we managed to save about 1.69 million kilowatt-hours of electrical energy in 2015-16 (equivalent to reducing 1,176 tonnes of CO2)5.
| (4) | 2006-07 as baseline year |
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| (5) | Using Hong Kong-wide default values of 0.7kg CO2 equivalent per kWh. |
Large-scale PV systems, either off-grid or on-grid, have been deployed at DSD facilities to power on-site equipment. They include sewage treatment works at Yuen Long, Shek Wu Hui, Stonecutters Island, and Siu Ho Wan, and Sandy Bay. With the completion of the PV system installation in Siu Ho Wan STW in end 2016, the combined generation capacity of all PV systems in our sites will be about 1,250 kilowatts.
Biogas is a source of renewable energy emitted during the anaerobic digestion of sludge generated from the sewage treatment processes. DSD installed five combined heat and power (CHP) generators with a combined electrical generation capacity of 3,600 kilowatts at Sha Tin, Tai Po and Shek Wu Hui STWs, using biogas to generate electricity to partially offset the electrical demand of the plants. During the year, we generated over 32 million kilowatt-hours of electricity using biogas, which is about 28% increase as compared with 2010-11.
Some STWs produce less sludge and biogas than others which makes them unsuitable for conventional large scale CHP generators. To better utilise the biogas, we have been proactively exploring the adoption of micro-turbine system in these plants, and we completed a pilot programme at Yuen Long STW with the installation ofa micro-turbine engine (capacity at 30 kW). The result showed that the system was stable and reliable with electrical output in line with design specifications. We will continue to monitor the performance of this system and make modular expansions if needed. The operational data collected and lessons learnt from this trial will help us design similar facilities for other STWs.
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The PV system at Siu Ho Wan STW
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Micro-turbine engine at Yuen Long STW
According to A Food Waste & Yard Waste Plan for Hong Kong 2014-2022, the Government anticipates reducing food waste disposal to landfills by 40% in 2022 (using 2011 as the base year). In view of this, DSD and the Environmental Protection Department are implementing the six-year Food Waste/ Sewage Sludge Anaerobic Co-Digestion Pilot Trial at Tai Po STW.
We will begin by establishing pre-treatment facilities for food waste at the present Shuen Wan Leachate Pre-treatment Works, and constructing anaerobic digestion facilities at Tai Po STW. The pre-treated food waste will undergo anaerobic co-digestion with sludge at Tai Po STW, during which biogas will be generated. The scheme will raise city-wide food waste processing capacity and reduce carbon footprint by recovering energy from waste.
The contract for the investigation, design and construction of food waste pretreatment facilities commenced in October 2015. After commissioning in 2018, it is anticipated that the relevant facilities would treat a maximum of approximately 50 tonnes food waste per day.
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