All responsible companies are considering their carbon emissions and how they can adapt to a low-carbon future. The water sector is no exception and, as a major energy user, its first step is to address energy efficiency.
Water companies use 7,700 gigawatt-hours of energy each year, about 2% of all UK industrial consumption. The sector ranks fourth in terms of energy intensity, behind steel, cement and parts of the chemicals sector.
Pumping water is the main energy use but the industry has cut its consumption in recent years, according to sustainability indicators released by industry body Water UK. In 2005/06, firms cut their energy use by 5% compared with the previous year - a saving of more than 400GWh (ENDS Report 384, pp 9-10 ).
Water UK’s latest figures show the lowest industry total since 2002/03 when it first began compiling the data (see figure).
The trend is unexpected because since privatisation in 1989 water companies’ have generally experienced a steep rise in energy use - driven largely by tighter environmental standards.
Yorkshire Water’s energy manager Tony Harrington notes that the company used 299GWh per year at privatisation. This has steadily risen to 565GWh last year. Wessex Water reports that its energy consumption has risen by 35% since 1995.
On the clean water side, the drivers of higher energy use include regulations on the stomach bug cryptosporidium. These have often compelled companies to install extra filtration, while pesticide removal has required granular activated carbon treatment. A growing number of companies are also having to blend or treat sources that have high levels of nitrate pollution.
On the dirty water side the situation is even more acute. Higher effluent standards have pushed the industry towards energy-intensive processes including aeration, membrane treatment and, for coastal discharges, UV disinfection. At the same time low-energy alternatives, such as gravity-fed trickle filters, reed beds or lagoons, have fallen out of favour.
Water UK figures suggest a decline in annual energy use across the industry of about 450GWh - enough to power a medium-sized water company. But the cause of this reduction is difficult to see in data for the past four years given to ENDS by the big ten companies (see table).
The trend is a rise in average electricity use of about 2.5% a year. All companies report a rise over the four years, although there are fluctuations from year to year.
Yorkshire Water’s Tony Harrington explains the year-to-year variation in his own figures: "Like last year, 2003/04 was a dry summer. This means that we needed more energy to deliver drinking water to customers because we have less choice about where we take it from. Therefore, we need more pumping and the net energy cost of drinking water went up."
For wastewater, it is arguable that in wet years sewage pumping will increase, using more energy, but, for Yorkshire at least, the two factors do not cancel each other out. "It is quite dangerous to look at individual years. You need to look at the trend across several," Mr Harrington concludes.
But Water UK’s figures are for total energy use at fixed sites (excluding transport) rather than electricity use. For most companies, the two are similar because the industry’s key water treatment processes run on electricity (see table).
The difference is that total energy includes minor oil and gas uses such as office heating and starting biogas combined heat and power engines.
Most energy managers were surprised by the apparent fall. Angela Needle of Anglian Water says recent initiatives had brought a slight decline in electricity use, but a rise was expected in the longer term. The company’s website includes a forecast of 910GWh by 2010 - a sharp increase on 750GWh in 2005/06 - although Ms Needle insisted this has now been revised downwards.
South West Water’s energy and environment analyst David Rose says energy use is still rising as a result of its long-running sea discharge improvement programme Clean Sweep, now almost complete. More sewage treatment and pumping were the main cause.
Scottish Water’s head of energy management Rob Crusher says the firm’s energy use has risen by about 2.5% a year over the past four years as a consequence of its asset development programme.
One energy manager who asked not to be named sums up the situation: "All the legislation is demanding more treatment and it’s all heavy energy stuff. The trend in energy use is always upward and one new treatment works wipes out all the effort we put into energy efficiency. We are fighting to keep levels the same."
A Water UK spokesman was unable to give a further breakdown of its energy statistics or to explain the differences in the two data sets. South West Water’s energy manager Alan Burgess, who chairs the industry’s energy management forum, was likewise unable to shed light on the different trends.
Water UK explains that companies were sensitive about disclosing figures and the full data set is only seen by a consultant who prepares the sustainability indicators. The body, however, acknowledges that more work is needed on sustainability reporting. "We would like to move toward a more public benchmark. It is time to move things on a bit and I think most of our stakeholders would like that."
One company whose figures differ from the norm in its gas-electricity balance is Northumbrian Water. Its regional sludge treatment centre at Bran Sands includes a 9MW gas turbine. The plant’s gas use accounts for the unusually large difference between the company’s electricity and total energy figures (see table 2).
When gas prices rose steeply a few years ago the company found it more economical to buy in electricity and stand the plant down, technical strategy manager Les Ammon explains. The plant is now only in intermittent use to support the national grid.
The impact on the company’s energy statistics has been significant. Gas use has been cut by some 200GWh, while electricity use has increased by only 75GWh, saving 125GWh. However, it is likely that overall carbon emissions will have increased.
Northumbrian’s total energy use has declined from 643GWh in 2000/01 to the current 589GWh. The difference may be a large part of the decline indicated in Water UK’s statistics - a sign that the apparent downward trend may be an illusion.
Yorkshire Water’s Tony Harrington says he would be disappointed if there was no downward trend. "We are all focusing on energy efficiency like there is no tomorrow because of energy prices and our commitment to reducing our carbon footprint."
Every company has a story to tell about its energy efficiency efforts. The common themes are increased metering, management and benchmarking. The industry’s energy management forum has been active in sharing information on the energy use of various processes and establishing industry benchmarks.
Mr Ammon says Northumbrian Water has been monitoring plant efficiency more intensely, particularly pump operation. The largest are now managed and metered over shorter intervals and the focus is on energy used per megalitre of water per metre lifted - a key industry benchmark.
A value of about four kilowatt-hours is expected and any fall-off is investigated. Causes of inefficiency can include valves not opening properly, creating extra load on the pump, changing patterns of demand in a supply system, pump wear and tear and other mechanical or electrical failures.
Severn Trent’s energy management programme is designed to understand and challenge existing energy use on a site-by-site basis. The company is over half way through a plan to look at its 400 largest sites accounting for more than 85% of its electricity use.
Another programme is to test controlling the amount of air used to regulate ammonia levels at sewage treatment plants. The method has shown energy savings at the Coventry works.
Severn Trent also plans to expand automatic electricity usage meters to hundreds of its smaller sites by 2007 to help site managers identify and address unnecessary consumption.
Yorkshire Water is working with the Carbon Trust to study energy used to pump water around its network, which costs £8 million annually. The company hopes to develop software and optimise pumping configurations to cut energy use. It will share the results with the industry.
Increasing renewable energy generation is a second string to improving companies’ energy balance sheets and provides a boost to national CO2, emission reductions. According to Water UK’s sustainability indicators, renewable energy use in the industry rose to a high of 14% in 2005/06 - a steady rise from 3.9% in 2000/01.
But these figures include not only companies’ own generation but bought-in renewable energy. Companies such as Wessex and Anglian Water have been obtaining renewable energy from their suppliers and are proclaiming the benefits in their corporate sustainability reporting.
Wessex has just met its self-imposed target of obtaining 20% of its energy from renewable resources in 2005. Of this only 7.8% was generated in-house, the rest came from EDF Energy and was a mix of hydro and biomass, but included some generation from landfill gas and waste incineration.
Anglian claims that more than 22% of its energy used is from renewable sources. Relatively little of this was self-generated with the rest coming from British Gas.
Water UK explains that the indicator included self-generated power and hydro, wind, solar, biofuels, landfill gas and waste incineration.
Both companies say their power was certified as climate levy exempt and involved no price premium. Given the confusion over what constitutes ‘green’ energy, and the problem of additionality, or double counting, of renewable energy production, it is not clear what the benefits in reduced CO2, emissions really are (ENDS Report 384, p 11 ).
Interestingly, South West Water says 85% of bought-in electricity comes from good-quality CHP plants. Again this is climate levy exempt, and confers some CO2, emission reductions, but does not count towards Water UK’s renewables indicator.
Companies are on firmer ground with in-house generation - whether the electricity is used within the company or exported to the grid. Opportunities for renewable generation include biogas from anaerobic sewage sludge digestion, sludge incineration and ‘small’ hydro schemes in water mains which capitalise on the head of water from supply reservoirs.
Data gathered by ENDS show that the proportion of in-house generation by the major companies stands at nearly 7.5% (see table 2).
It appears to have at least held its own since 2000/01 - meaning a real increase in line with rising energy use.
Companies are actively looking for all financially viable ways to increase production and some companies have huge scope.
Anglian Water currently generates 11.5GWh annually from biogas CHP. "We have lots of plans to expand renewables - doubling or tripling our capacity," Ms Needle told ENDS.
The company is a latecomer to sludge digestion and is expanding its capacity. It aims to generate 50GWh by 2010, even though many of its sewage works are small and do not produce much sludge.
Severn Trent is the company with the largest biogas CHP capacity and still expanding. It plans to add a further 1.4MW in 2007 by building installations at five new sites and improving efficiency at existing plant.
Over the next two years, the company aims to increase its renewable generation by 5%. It also intends to add to its two hydro schemes at the Clywedog and Vyrnwy reservoirs.
Wessex has been working at improving the efficiency of its in-house generation. "We have replaced old 1960s engines at Avonmouth, our largest site, and we are also starting on work to increase the yield of biogas, by homogenising secondary sludges," sustainability planning manager Dan Green explains. The treatment helps to break down cell walls in sludges from activated sludge plants and increase the gas production.
United Utilities is also planning to improve its existing sludge biogas efficiency with a sludge pre-treatment method known as "enzymic hydrolysis".
United’s current 10.4% of electricity use generated in-house comes from sludge incineration, biogas and small hydro schemes. It has a target to increase self-generation from the current 8.5% of total energy use to 10% by 2010.
Scottish Water produces 5.3% of its electricity in-house, mainly from small hydro schemes. The company has ten or 12 schemes varying in capacity from 70 to 200kW. It has recently invested in recommissioning several schemes which had fallen out of use.
The company has only one biogas CHP plant - although some Scottish private finance initiative operators do have them - and its sludge gas resources are largely untapped. Head of energy management Rob Crusher is not optimistic about the prospects for their development: "I would not say there was scope. The vast majority of our sludge digesters are aerobic, not anaerobic [which produce gas]. For some reason the pre Scottish Water authorities decided on aerobic systems. It was one of those things that couldn’t be foreseen within the life of an asset."
Some companies are being adventurous in their search for other renewable sources. Severn Trent says it is considering both wind and solar generation. While Yorkshire has already obtained planning permission for wind turbines at two sites.
Loftsome Bridge water treatment works will host two 80-metre turbines and generate 5.3GWh of energy. Hull sewage works will get one turbine and generate about half as much.
Yorkshire has substantial land holdings which in theory could be highly productive for wind turbines. But this opens up some questions for the company and its regulator. As Tony Harrington explains: "We are currently having a debate with Ofwat over whether we get in to that or buy in power from elsewhere."
Generally companies are looking for everything feasible within a five-year payback period, and the income generated by the sale of Renewable Obligation Certificates (ROCs) has made the investment worthwhile and helped investment in increased capacity.
Again, the sale of ROCs prompts some issues about the additionality of carbon emission savings. Arguably, the sale of the ROC takes with it the carbon emission benefits of that energy.
Companies are increasingly looking at their climate impacts, with Wessex Water and Severn Trent in the lead (see box , and ENDS Report 367, pp 22-25 ). The industry has been working with the Carbon Trust on a carbon management report. This is almost complete, although it may be some time before firms have the courage to air it in public.
Although there are some interesting issues to be addressed around sewage and sludge treatment and emissions of the greenhouse gases methane and nitrous oxide, energy-CO2, will remain the main focus of the sector’s climate strategy.
There are signs that the industry’s regulators are beginning to take climate impacts seriously. Yorkshire Water’s Tony Harrington says: "We have seen a sea change in the Environment Agency and Ofwat and we are working with Ofwat to work out the carbon footprint consequences of our investment plans."
But he is realistic about the future: "The water framework Directive and its daughters have the potential to drive energy use through the roof."
"We need some joined-up government. In the Climate Change Bill they are talking about a 60% reduction in energy use. Yet the EU policy agenda keeps pressing for tighter and tighter standards for the aquatic environment and not paying heed to the energy cost."
The debate has already surfaced. Northumbrian Water is pressing the Environment Agency to allow it to switch off UV disinfection of six sewage treatment discharges during winter (ENDS Report 383, p 21 ). The move would cut CO2, emissions by 2,200 tonnes.
Surfers Against Sewage says the move would be "a significant step backwards". Although Northumbrian maintains that five sites would continue to achieve guideline microbiological bathing water standards, the sixth would meet mandatory standards.
At Aldeburgh, Suffolk, it found that secondary treatment would produce more than three times the footprint of simple screening and discharge through the existing one-kilometre outfall. No deterioration in water quality at the beach was predicted.