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Carbon reduction vs efficient use of energy – Finding the balance in the water industry

22 November 2019

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Carbon emissions has been a hot topic in UK media, and let’s face it nearly everywhere else, for quite some time now and it’s a subject that isn’t going away any time soon. It only takes you to look in one or two of the UK’s biggest news publications on any given day and you’ll be sure to find an article around reducing your carbon footprint or similar. As one of the most energy intensive industries in the UK, the water industry can certainly not hide from this topic.  In this blog, we discuss how to find the balance between the all-important acts of carbon reduction against long-term efficient uses of energy- two things we think are difficult to balance. 

The carbon reduction drive

Thankfully, when it comes to the UK and Ireland, according to many sources, we aren’t in the top 5 or even 10 countries who produce the largest volume of carbon emissions[1]- the US, China and India seem to be commonly named the biggest offenders in numerous reports.[2] However, it doesn’t mean as a nation, we can pat ourselves on the back and move on. It’s important to note that when compared to the population of each of these countries that are considered the top 10 contributors to carbon emissions, the UK’s population is significantly lower than each of these. With a population that is continuing to grow[3], and a stark awareness of the detrimental effects of carbon emissions, we in the UK and Ireland, like all other countries, need to ensure we are doing all we can to reduce our carbon footprint.

When we consider carbon emissions, our minds often jump to car and other transport emissions, burning of fossil fuels in homes and large industrial factories.  Yet, the generation of electricity plays a major part is carbon emissions. According to Energy UK, “Most of the UK’s electricity is produced by burning fossil fuels, mainly natural gas (42% in 2016) and coal (9% in 2016). A very small amount is produced from other fuels (3.1% in 2016)”[4]. Therefore, we mustn’t underestimate the effect of our electricity consumption on carbon emissions- it is something we must strive to reduce.

How can the water industry decrease carbon emissions?

According to a report produced by CIWEM in 2013, “A Blueprint for carbon emissions reductions in the water industry”, the water industry contributes around 1% of the UK’s greenhouse gases and is the fourth most energy intensive industry in the UK.  In addition, as new technology has emerged to increase the effectiveness of water and wastewatertreatment, so too often has the energy consumption used in these technologies increased.

The Carbon Trust has set out many guides[5] and case studies[6], some published as recently as October this year, to help organisations, both public and private, to save energy.  There are many industry specific guides, and despite there not being one specific to the water industry yet, these contain very useful information that can be extracted and adapted to help water companies become more efficient in terms of energy consumption.

Carbon reduction in sludge screening, grit removal and anaerobic digestion- finding the balance

One aspect of carbon reduction that we felt was worth discussing, was the balance between long-term efficiency improvements and short-term wins on carbon reduction.  A key example of this is reducing the energy used in sludge pre-treatment within the water industry.  If water companies were to reduce the level of treatment at this stage, it would certainly reduce carbon emissions in this area of the wastewater treatment works (WwTW) , however we’d argue that when a holistic view of the entire work’s energy consumption is taken, it would quickly be seen how this increases energy consumption downstream.  If sludge isn’t treated effectively with rag and grit being removed as soon as possible upstream, these materials will cause abrasion and wear, resulting in increased maintenance and downtime which in turn often leads to increased energy consumption either to repair parts of the WwTW or to catch up on uptime afterwards.  If rag and grit is left in sludge, it also builds up in digesters downstream. The accumulation of these materials in AD tanks significantly reduces the capacity of the system, and in turn their efficiency and effectiveness. This means that more energy must be used to produce the same amount of biogas and more energy must also be used in excavating the tanks to once again increase their capacity.

The accumulated levels of settled grit in an anaerobic digester can be as high as a quarter to a third of its height by the time companies can no longer put up with the efficiency loss being caused and help is called in. The digester then needs to be taken offline, the heating turned off, the feeding stopped and then the gas generation needs time to wane down sufficiently for the digester to be safely vented and accessed. However, treating the source material before feeding has been shown to significantly cut down the need to clean out digesters.

A TOTEX approach may be what’s needed to ensure a comprehensive approach to carbon reduction in wastewater treatment works. Carbon reduction is essential but will only succeed if we make decisions that not only reduce energy use per m3 of drinking water produced or wastewater treated, but also maintain or improve quality.  Although carbon reduction is a major issue and one we all must face head one, we shouldn’t rush to make fast carbon reductions via electricity reduction alone in the short-term at the cost of quality and the water environment in the medium or long term.

We’d love to hear your thoughts on the matter. Get in touch with us on LinkedIn or contact us at to continue the conversation!

For more information on CDEnviro solutions for sludge dewatering or tank cleaning, visit our solutions pages or email us.


[1] Visual Capitalist (2019) All the World’s Carbon Emissions in One Chart [online] Last accessed 18/11/2019

[2] Statista (2017) Largest producers of territorial fossil fuel CO2 emissions worldwide in 2017, based on their share of global CO2 emissions [online] Last accessed 18/11/2019

[3] Office for National Statistics,

[4] Energy UK (2019) Electricity Generation, [online] Last accessed 19/11/2019

[5] Carbon Trust (2019) Tools, Guides & Reports, [online] Last accessed 19/11/2019

[6] Carbon Trust (2017) Industrial energy efficiency, [online] Last accessed 19/11/2019

Recycling wastewater water treatment sludge screening Grit removal