Increasing emission of greenhouse gases intensifies global warming and climate change.  To mitigate climate change, DSD has deployed additional resources in adopting renewable energy technologies on a wider and larger scale in the existing and new facilities for further reduction of the carbon emission.  The renewable energy generating systems are connected on-grid for supplying electricity to various equipment at the DSD’s facilities.  To help build a cleaner and more sustainable environment, DSD has been extending the application of renewable energy, such as solar energy, hydroelectric energy and waste-to-energy. 

Solar Energy

Over the years, DSD has endeavoured to make full utilisation of the open space in sewage treatment works and pumping stations to capture more solar energy.   The largest photovoltaic system in Hong Kong was installed and commissioned in Siu Ho Wan Sewage Treatment Works on 9 December 2016.  The solar farm comprises over 4,200 numbers of polycrystalline photovoltaic panels with an installed generation capacity of 1,100 kilowatts, which accounts for about 20 percent of the current annual electricity of the Siu Ho Wan Sewage Treatment Works.  Together with over 30 other photovoltaic systems in DSD’s venues, the total installed generation capacity is around 1,400 kilowatts.

Solar Farm at Siu Ho Wan Sewage Treatment Works

Hydroelectric Energy

Hydroelectric energy refers to capture energy from water when it releases from height and flows through a turbine for generating electricity.  Subsequent to the completion of Harbour Area Treatment Scheme Stage 2A project, DSD conducted an innovative pilot trial to harvest the residual energy from the water pressure to generate electricity through installing hydropower generators at the effluent shaft at Stonecutters Island Sewage Treatment Works.  The maximum power output of the micro hydro-turbine system is 38 kilowatts.  DSD is also exploring the feasibility of installing hydro-turbine system at other venues.

Waste-to-Energy

In DSD, biogas is one of the by-products in the anaerobic digestion process at the four major secondary sewage treatment works.  Biogas consists of methane, carbon dioxide and other trace amount of gaseous products, and it can be used as a fuel to generate energy.  Over the past three decades, DSD has been using biogas for electricity and heat generation.  In particular, the dual-fuel (biogas and diesel) generating system was brought into operation many years ago.  The heat generated is used for the hot water circulation system for the digesters in Shatin Sewage Treatment Works.  In light of technology advancement, DSD has introduced different types of biogas-fuelled generating systems including combined heat and power (CHP) generating systems and micro-turbine systems in the major secondary sewage treatment works for promoting the use of renewable energy.  Since March 2006, five CHP generating systems and two micro-turbine systems have been installed with total installed capacity of 3,900 kilowatts.

Dual-fuel generating system at Shatin Sewage Treatment Works	Micro-turbine system at Yuen Long Sewage Treatment Works
Combined heat and power generating system at Shek Wu Hui Sewage Treatment Works

Way Forward - Food Waste-Sewage Sludge Co-digestion

Apart from the use of biogas for supplying electricity to the sewage treatment plants, DSD is exploring opportunities for the use of sewage sludge co-digestion with food waste at Tai Po Sewage Treatment Works.