Analysis: Decarbonising water

Water is one of the most energy-intensive sectors in the UK. It is also one of the business sectors most affected by climate change. Lois Vallely takes a look at what the industry is doing to cut carbon.

The water industry, and particularly the wastewater industry, is “at the forefront of climate change”, according to Water UK, as every major impact – temperature change, more intense rainfall, changing rainfall patterns, and sea level rises – directly affect companies’ activities.

Ofwat says climate change is one of the “fundamental challenges” facing the sector, putting extra pressure on resilience, environmental quality, and affordability. The regulator tells Utility Week it expects companies to understand the risks posed by the changes and “respond innovatively, sustainably and flexibly” to build resilience over the long term.

Yorkshire Water installed a wind turbine at Old Whittington wastewater treatment works in Chesterfield last month to increase the amount of renewable energy generated onsite. And this is just the latest step in the water sector’s war on climate change.

What are wastewater firms doing on climate change?

The UK has a legally binding commitment to achieve an 80 per cent reduction in carbon emissions by 2050. The decarbonisation of energy will play a key role in reaching this target and, as a significant user of energy, the water sector has a big role to play in mitigating climate change.

Greenhouse gas emissions from water operations are around 0.7 per cent of UK emissions, according to Ofwat. In 2014/15, water companies in England and Wales emitted the equivalent of just over 4,000 kilotons of carbon dioxide.

The amount of renewable energy generated by companies is on the rise, mainly because of significant investment in combined heat and power, and in generating biogas from the anaerobic digestion of sludge, a solid by-product of the sewage treatment process.

Water companies are also generating energy from hydro, solar and wind, and imported renewable energy. The most up-to-date figures (2010/11) state that around 10 per cent of all the energy used by the water industry came from its own renewable sources that year. However, companies are looking to increase that, with ambitious and challenging carbon reduction and renewable energy targets.

Anglian Water

Anglian Water has a target to reduce gross operational carbon by 7 per cent by 2020, from a 2015 baseline. It also aims to deliver a 60 per cent reduction in embodied carbon by 2020 from a 2010 baseline.

In the past five years Anglian Water has delivered around 1,000 energy projects, delivering savings of more than £16 million, and dramatically reducing its carbon footprint.

In May, the company announced that it was setting its sights on a “more ambitious” renewables strategy to help deliver this.

Northumbrian Water

Northumbrian Water has set a carbon reduction target of 35 per cent by 2020, from a 2008 base. To help achieve this, the company has a target to generate 20 per cent of its energy needs from renewable sources.

The wastewater company is the first and only in the UK to use 100 per cent of the sludge remaining after sewage treatment to produce renewable energy, at two thermal hydrolysis advanced anaerobic digestion plants.

Severn Trent Water

Severn Trent currently generates the equivalent of 28 per cent of the energy it uses from renewable sources. This energy is used at Severn Trent Water sites or exported to the national grid. The company says it is working to increase its energy production from renewable sources further, to 50 per cent of its consumption by 2020.

The firm has set itself a five-year carbon reduction target to reduce its emissions from 491 kilotons CO2 equivalent in 2014/15 to 458 kilotons CO2 equivalent by 2020.

In the long term, Severn Trent aims for carbon neutrality and energy self-sufficiency.

Southern Water

Southern Water exceeded its target to reduce carbon emissions to 281 kilotons of CO2 in 2015/16, achieving 267 kilotons. This was 2 per cent below the previous year and its lowest emissions for four years.

Southern says it is committed to keeping its carbon emissions to a minimum, and has increased the proportion of renewable energy generated to more than 17 per cent of its overall electricity consumption.

To do this, the firm is replacing all of its existing combined heat and power stock with higher efficiency units, is installing additional units, and is installing ground-mounted solar across five operational sites. It also has a programme of capital maintenance to replace less efficient assets with new higher efficiency units.

South West Water

South West Water is one of the largest electricity users in the South West, using 250GWh of electricity a year. More than 70 per cent of its carbon emissions are associated with its consumption of energy. Therefore, the company is working towards generating 50GWh of renewable electricity by the end of 2020.

South West Water wants to achieve an 80 per cent reduction in carbon emissions by 2050, on a 2006/07 baseline.

Thames Water

Thames Water has set itself a target of cutting greenhouse emissions associated with operations and electricity and natural gas use by 34 per cent by 2020, compared with 1990 levels.

The company aims to self-generate 33 per cent of its electricity by 2020, and already generates some of its own electricity renewably from sewage and solar panels.

It generated a total of 12.5 per cent of its electricity requirements from renewable sources in 2014/15 – a 4 per cent increase on the year before.

Thames also has an energy efficienc y programme, which focuses on lighting management and pumping efficiency. By upgrading its pumping stations, the company saved 889 MWh of electricity in 2009/10.

United Utilities

In 2015/16, United Utilities’ carbon footprint was 454,857 tonnes of CO2 equivalent, 22 per cent below its 2005/06 baseline.

This year, the company has set a target to achieve a 50 per cent reduction on the 2005/06 baseline and to continue to reduce emissions to 60 per cent by 2035.

The company’s renewable energy production in 2015/16 was 138GWh, representing 17 per cent of its electricity consumption in the year. It has plans to generate around 35 per cent of its electricity consumption from renewable sources by 2020.

Wessex Water

Wessex Water says it aims to be carbon neutral in the long term, with a shorter-term target to generate 30 per cent of its own energy from renewable sources by 2020.

It also wants to lower greenhouse gas emissions to one-third below 1990 levels in 2020, and 50 per cent below by 2030. It then wants to be able to lock up the carbon equivalent of its remaining emissions by 2030.

Yorkshire Water

Since 2008/09, Yorkshire Water has reduced its operational carbon emissions by 18 per cent and its electricity consumption has dropped by 10 per cent since 2009/10. The company’s aim now is to halve the carbon emissions of new assets it builds by 2020.

Overall, Yorkshire supplied 11.3 per cent of its electricity needs through renewable self-generation in 2015/16. It hopes to generate approximately 18 per cent of its electricity needs by 2020.

Current plans to help the company achieve this include:

• a £71.9 million investment in a sludge treatment and anaerobic digestion facility at its Knostrop Works in Leeds, planned for completion in 2019;
• a £1.6 million investment by its sister company Kelda Water Services to install a 0.5MW wind turbine at Old Whittington treatment works in summer 2016;
• a planning application for the installation of solar panels adjacent to Elvington Treatment Works, which would provide 15 per cent of the site’s needs.

Welsh Water

Welsh Water wants to increase the total energy it self-generates from 15 per cent in 2015 to 25 per cent by 2020, and reduce the energy it consumes with its assets by 5 per cent by 2020, compared with 2012.

It also hopes to reduce its operational carbon emissions by a further 7 per cent by 2020, making a total reduction 32 per cent on a 2007 baseline.

Impacts of climate change on the water sector

• Precipitation: changes in patterns of rainfall will make it more difficult to meet demand, and could increase the risk of droughts.
• Abstraction: higher temperatures and less rainfall in the summer mean there is more pressure on already scarce water resources.
• Treatment: more frequent heavy downpours and changes to the ecology of rivers may reduce the quality of the water, which would then require more treatment.
• Distribution: important assets are at greater risk of flooding, and changes in soil moisture levels may lead to changing patterns of pipe bursts and leaks.
• Consumption: as the climate warms, demand for water is likely to increase.
• Drainage: changing rainfall patterns challenge the current approach to drainage. Climate change will increase the risk of surface water flooding and sewer flooding, which is one of the most serious types of service failure. Climate change may also increase the damage caused by overflows of untreated wastewater into the environment
• Wastewater treatment and discharge: reduced river flows may mean more carbon-intensive sewage treatment is needed to ensure rivers are protected.

Source: Ofwat

Case study: Wessex Water’s bio-bus

In 2009 Wessex Water created GENeco – now a functionally separated division of Wessex Water Services – to undertake sludge treatment services at its largest sludge treatment centre. GENeco generates around 40GWh of renewable energy annually, a 53 per cent increase since its operations began, and recycles more than 250,000 tonnes of biosolids to land each year.

The subsidiary launched its bio-bus in 2014. After running a successful trial route between Bath and Bristol Airport, the bus was launched to be used in regular service within the city of Bristol. The route is being operated by First West of England along the number 2 route from Cribbs Causeway to Stockwood.

Biomethane produced from sewage sludge and food waste has the same composition as natural gas, and can therefore be used as a direct substitute for natural gas. The gas fuel is stored on the top of the bio-bus, and pressurised to 200 bar. On a full tank of fuel, the bus range is approximately 300km.

“Well-to-wheel” biomethane produces 95 per cent less CO2 than diesel, and “tank-to-wheel” CO2 emissions are 20-30 per cent lower than from diesel vehicles. Therefore, biomethane represents a sustainable and renewably-sourced alternative to fossil fuels.