There is an intensifying realisation that we need to act on curbing greenhouse gas emissions to avoid a dangerous global temperature rise. While national governments are working to reach a global carbon accord in Paris later this year, much can be done at local level to turn the tide. Cities and their citizens can make a lasting contribution by changing their habits and practices. Unknown to many is the opportunity that exists to change the energy footprint of the urban water cycle: the way we manage our water and wastewater.

The energy used to supply water to cities and clean used water is responsible for between 3 – 8% of global greenhouse gas emissions. This is roughly similar to all global air traffic emissions. Increasing energy efficiency and producing energy from the urban water cycle can result in ‘urban water’ becoming a net energy producer and even achieve carbon neutrality. This would not only help to curb a good chunk of greenhouse gas emissions, it would also reduce the energy bills of consumers, utilities and industries alike.

How can this happen? Let’s start with citizens and consumers. A significant change in consumer energy behaviour will happen in coming years. The new energy consumers not only consume energy, they ‘produce’ energy through, for example, efficiency and home-based solar power. This move from consumers to prosumers is enabled, amongst others, by new products in the sector such as Google –Nest and cheap IKEA solar panels. These kinds of products reduce costs or offer consumers energy production at very competitive prices, leading to a potential rapid change in a citizen’s energy demand.

Looking at water, we’ve seen a significant increase in efficiency at household level due to the introduction of water efficient appliances such as water efficient washing machines and shower heads. As a result total water consumption is falling year by year. In Europe about 60% of household level energy is used to heat water for cooking, showering and washing. New technologies are now appearing on the market to capture this heat and re-using rather than leaking it away in drains and sewers. Further increasing household level water efficiency, and reducing the energy involved in the household water cycle, is a major opportunity to reduce carbon emissions and save household budget.

Looking at utilities, water and wastewater operators can reduce their energy consumption significantly. Reducing pumping, more effective aeration and reducing leakage can significantly lower energy consumption. Fluctuating energy prices often make it financially beneficial for utilities to embark on an aggressive energy saving plan. Combining this with producing energy from gravity fed water supplies or producing bio-gas from used water can bring utilities closer to energy and carbon neutrality. One example, the Concept Wastewater Treatment Project in China, might bring a paradigm shift from energy intensive to energy neutral or energy positive. This ambitious project, if successful, would propel China into a leading position in terms of energy neutrality in wastewater utilities.

Taking a city perspective, further opportunities arise to save and produce energy in the urban water and used water cycles. Using common heat-exchange technology, urban groundwater can be used to store or abstract heat, serving to cool in summer and heat in winter. Co-location of utilities and industries can enable using heat generated in one plant to energize production in a neighboring facility. Co-digestion of used water with organic waste from farmers and slaughterhouses can produce bio-gas to power city buses. At the same time, water can be re-used. In Macao, for example, the ambition is to have reclaimed water to constitute at least 10% of total water consumption by 2020. To capture energy saving and production opportunities throughout the urban water cycle, however, one has to reach out and connect to other sectors and professionals.

Utilities and their leaders have a major role to play in the transformation of the energy footprint of the urban water cycle. The development and implementation of an energy savings and production plan, that reduces costs and makes their operation far less affected by fluctuating energy prices, is well within their reach. Through informing their household clients, utilities can be pro-active and help consumers change behavior and reduce energy and water consumption. In connecting to industry they can be pivotal in transforming the total urban water cycle and its energy footprint. Yet, they can’t do it alone.

To enable the required transformation we need the powerful combination of entrepreneurship and regulation to be aligned. Creating a market for more efficient appliances needs regulation to allow market entry of new technologies and incentives to end wasteful usage. Allowing and stimulating pilot schemes to demonstrate proof of concept and practice is critical as a stepping stone to wide-scale adoption. Reviewing water and energy tariffs while water and energy saving technologies become widespread can be a further stimulus in the transition.

Impact and progress will only happen by bringing along consumers and citizens. To alter the energy footprint of the urban water cycle, citizen and consumer organizations can play a key role. Bringing citizens’ groups together to develop collective action, for example at neighborhood level, can become emblematic to change paradigms and practices. Engaging citizens in the urban water cycle energy transition is a fantastic way to connect many more people to the needed action to curb greenhouse gas emissions. Let’s act together, act responsibly and swiftly, we have little time to loose.