Turning water green

As the world races to cut greenhouse gas emissions, the carbon footprint of the water industry is actually moving in the opposite direction. That’s because the priority here is to guarantee access to safe drinking water and sewage services around the world – which means installing more infrastructure and processing more water and more wastewater. Total emissions will inevitably have to increase. The challenge, therefore, is to limit that increase as much as possible.

Today, the water and sewage industry generates around 1.55 billion tonnes of greenhouse gases per year – or around 3 per cent of all global emissions. Yet the problem is that one in four people do not have access to safe drinking water and 46 per cent lack safe sanitation.¹ The UN’s Sustainable Development Goal number six hopes to close the gap, targeting universal access to drinking water, sanitation and hygiene.

To reach these lofty goals, the industry’s carbon footprint will nearly double by 2050 to 2.82 billion tonnes if there is no improvement in efficiency, according to research by a member of the Pictet-Water Thematic Advisory Board.

However, some 200 million tonnes of CO2 emissions a year could be saved by decarbonising water production, the research shows. That could include better management of water pressure, as well as monitoring (and fixing) of any leaks.

Pumping water from A to B is a major contributor to the water sector’s greenhouse gas emissions. At present, only around 10 per cent of pumps work at optimal efficiency. Some need to be replaced altogether; others need to be optimised (for example by adjusting the pressure or even changing the location of the pump). However, such changes would be costly and could cause temporary supply disruptions. 

The state of current infrastructure is another problem. The water sector is very fragmented, using the same distribution models as a century ago. Efficiency could be improved with a more centralised structure, helped by consolidation within the industry.

Then there is the amount of water we use. At industry level, there has been much progress on reducing water use and increasing efficiency. Farming and agriculture still have much improvement to make. And, at the household level, water meters have proven highly effective.

Powered by sewage

The water industry could reduce its environmental footprint further still if it could find a way decarbonise the sewage – or waste water – sector. Here, there is the potential to achieve a negative carbon footprint by turning sludge into clean energy.

That involves capturing the methane released during anaerobic decomposition and turning it into heat and electricity. For sewage treatment plants, this approach not only reduces emissions and improves green credentials, but can also create a new revenue stream, with the potential to sell the resulting renewable energy to the local grid or to use it on-site to reduce bills.

Additionally, water can be separated from the sludge and re-used as a cheaper alternative to desalination.

Overall, analysis from the Pictet-Water Thematic Advisory Board shows that decarbonising the sewage sector – and harnessing it for renewable energy production – could save 2 billion tonnes of emissions per year by 2050.

Spotlight on solid waste

Last but not least, there is solid waste management. Although this isn’t directly related to water, it is a related industry as it often involves the same companies. Uncontrolled landfills are one of the main sources of underground water contamination, so efficient management of solid waste is very important to preserve the water cycle.

Here, two of the major greenhouse gas contributors are emissions from trucks used in waste collection and the gases generated by landfills (both from microbial decomposition and from the mechanical equipment).

Moving to electric vehicles could be part of the solution, as long as the electricity comes from renewable sources. Vehicles powered by compressed or liquefied natural gas (CNG/LNG) are also gaining in popularity, particularly in the US where they already account for 12 per cent of the waste collection fleet – a share that should grow as old trucks need replacing. Although not fully green, these have half the carbon intensity of diesel equivalents, marking a significant step in the right direction. Hydrogen trucks are another possibility, but these are still in development, with a pilot project underway in Northern Europe.²

For landfills, one problem is the methane produced during the anaerobic decomposition of organic waste. This is a particularly serious issue in the US, where organic waste is often not separated out for composting and ends up in landfills.

The faster and more efficient the decomposition, the less gas is released. Traditionally, landfill business models focused only on containment of the waste; there was no incentive to optimise the decomposition process. This is changing.

Optimal conditions for decomposition are high moisture content, warm temperatures of around 37C and a non-acidic environment (with pH above 7). But it’s not straightforward. Raising the moisture content can make the waste unstable, increasing safety risks. That can be partially addressed with the addition of woodchips, although they bring additional costs and use additional resources, which have their own environmental footprint.

The methane produced by landfills can be collected. Then the problem is what to do with it. Latest initiatives are looking at using the collected gas for the production of electricity and heat, following a similar process to the one being developed for sewage.

Potentially even more revolutionary are plans to use landfills as carbon repositories. In the US alone, there are some 1,400 holes in the ground that are ripe for carbon sinking. The idea is to remove carbon from the air using filtration systems, and then sequester (or trap) it for perpetuity. Latest technology from the likes of Climeworks AG is making the process more accessible and more affordable.

The growing focus of governments and consumers on protecting the environment opens the door for innovation to reduce the carbon footprint, future-proofing business models. Businesses which embrace greater efficiency and greener practices are expected to thrive over the medium term – and the water and sewage industry is no exception. Indeed, as we increase the provision of water and sewage services around the world, it is becoming ever more important to optimise their environmental footprint.