Fear of ‘forever chemicals’ could put paid to biosolids

By Lucinda Dann

23rd April 2024

The UK sludge market stands at a crossroads. Having pivoted to sending sewage sludge to agriculture after disposal in the sea was banned in the 1990s, the UK has led other countries in resource recovery.

Today 87% of the UK’s treated sewerage sludge is recycled as an agricultural fertiliser and soil improver – the only current disposal outlet alongside land restoration.

But wastewater company business plans for PR24 reveal the level of concern over the sustainability of this disposal route from as early as the next asset management period (AMP8). This is due to a raft of regulatory changes looming on the horizon, each with the ability to severely reduce the landbank available for disposal.

A major study funded by the industry in 2022 modelled five different scenarios based on the PR24 water industry national environment programme (WINEP) drivers to understand the effect of increasingly stringent environmental restrictions on landbank availability.

In scenario 4, the most likely of the five and the one water companies are now working towards, there will be an almost fivefold increase in landbank required compared to scenario 3, which is the baseline.

This means demand for land will outstrip supply and could mean only a third of biosolids can be recycled to agriculture, forcing water companies to look for alternative disposal routes.

Water companies have laid out plans to invest in developing advanced thermal treatment technologies during AMP8 in the hope the technology could be implemented from AMP9, allowing the industry to transition away from agriculture.

However, commentators have warned that while increased environmental restrictions have the power to severely upset the bioresource market, the threat the industry should be most concerned about is public perception of contaminants such as PFAS (Per- and Polyfluorinated Substances) and microplastics.

This has the potential to shut down recycling to land overnight, forcing water companies to turn back to incineration rather than look to upcoming technologies and potentially locking the UK out of the resource recovery market in the long-term.

Here Utility Week unpacks the threats to the industry and the likely cost, both financially and to net zero of a sudden change in direction.

Increased environmental restrictions

The industry’s current disposal strategy has already been given a stay of execution after the Secretary of State chose to intervene following much disagreement over the Environment Agency’s (EA) chosen interpretation of the new Farming Rules for Water.

This interpretation would have banned the majority of autumn applications, effectively shutting down agriculture as a disposal route as this is when 75% of biosolids are applied.

However, while the guidance has given the water industry certainty in the short term, it is due to be reviewed no later than September 2025. Some in the industry, like Yorkshire Water, think the progress that has been made by the industry with the Department for Environment, Food and Rural Affairs and the EA in the intervening time means the implementation of the most stringent restrictions is now “highly unlikely”.

Others, such as United Utilities, seem less reassured. It calls the situation a “hidden crisis”. The Grieve landbank assessment, which was commissioned to model the effects of extra restrictions, found between 2.5 and 6 million hectares of extra land would be required due to the loss of autumn applications. This alone would force water companies to look for alternative disposal routes.

Although increased autumn restrictions are not guaranteed, new rules around phosphate management are likely and will also have a major effect on the industry’s land requirement.

Firstly, the EA has challenged how application rates are calculated, which would mean that rather than biosolids being able to be spread on a field every year, this could rise to just once every 14.5 years, according to the worst-case scenario in the Grieve modelling.

As this would affect 70% of the soils used for biosolids recycling, the land requirement would increase by between 1 – 2 million hectares.

Further restrictions on top of those in the Farming Rules for Water are also expected in sensitive sites and catchments to meet government nutrient neutrality ambitions.

Tighter phosphate permits on wastewater treatment works will rapidly increase the phosphate content and quantity of sludge, exacerbating the problem.

United Utilities expects the nitrogen loading of its sludge to double by 2038, while increased chemical dosing and tertiary solids removal will see the quantity of sludge produced increase by 25-30%, undermining industry efforts to reduce the quantity of sludge produced.

By investing in advanced aerobic digestion, among other technologies, the industry could achieve a one million-hectare reduction in the required landbank, helping to counter the effects of population growth.

The industry is also awaiting another significant update which would introduce permitting to the sludge industry for the first time in the form of the EA’s Sludge Strategy.

This was due to be published in 2023, and although it is expected to include biosolids in the Environmental Permitting Regulations (EPR) framework for the first time, its true extent is not yet known. However, it is very likely to have a significant impact on the administrative process, logistics and operations of biosolids recycling, requiring thousands of permits each year.

This has the potential to result in delays in the transport and application of biosolids. Yorkshire Water believes such delays would make the process “increasingly difficult to manage” and ultimately make it “impracticable” to work with farmers.

Running out of time

Given the threats facing the biosolids industry water companies are looking at alternative technologies through which it can transition away from agriculture as a disposal route. Most companies are pinning their hopes on the continued development of advanced thermal conversion (ATC) technologies such as gasification and pyrolysis as these offer the greatest potential for resource recovery.

However, neither technology would be ready for deployment at commercial scale before at least AMP9. Water companies are hopeful they will be able to continue sending their sludge to agriculture long enough to be able to invest in developing these novel technologies, with Southern Water outlining that its ideal scenario will see it continue with its deployment strategy until 2040-50.

But the industry may not have time to wait for ATCs. Yorkshire Water confirms in its business plan that the removal of the Statutory Guidance around the Farming Rules for Water would force all wastewater companies to look at alternative disposal routes immediately.

And there is another, potentially bigger problem. Public awareness around so-called “forever chemicals” is increasing thanks to the efforts of figures such as George Monbiot, who wrote an article for the Guardian last month entitled “Britain is becoming a toxic chemical dumping ground”.

His campaign, Fighting Dirty, has been granted a high court date to challenge what it calls is the “outrageous refusal to test or regulate the many toxins being spread on farmland in sewage sludge” by the government.

In 2020 the EA committed to bring in testing and regulation by 2023, but the latest update to its sludge strategy has removed that date and not replaced it, effectively abandoning the commitment.

Karyn Georges, managing director of consultancy Isle Utilities, says the number one concern for water companies should be the potential for another public relations disaster over contaminants such as PFAS.

“Things are changing rapidly in terms of public perception around these contaminants. With heightened public interest in water company activities, there is the real risk that the public outcry number two, after storm overflows, justifiably or not, will be biosolids to land,” she says.

“The fact is people are becoming aware of water company activities. Because there is such uncertainty around PFAS, microplastics and then other contaminants within sewage sludge and treated biosolids, if you look at the precautionary principle it seems sensible at the very least to be looking at whether agriculture is still the most sustainable way of recycling biosolids.”

Stephen Smith, professor of bioresource systems at Imperial College London agrees with Georges, saying the industry is at a “crossroads” after many years of stability.

Although awareness has been rising over the last ten years of the range of contaminants potentially creeping into sludge, the research industry has been very active looking at resource recovery opportunities.

“Hopefully resource recovery is going to be the future, but we could really mess it up, and contaminants are the thing that could destroy confidence in the progress we have made currently and what is possible going forwards.”

Back to incineration

The 40% reduction in farmer acceptability due to contaminants modelled in the worst-case scenario of the Grieve report would already force water companies to invest in incineration to some extent.

However, Georges says that in reality the level of public outcry that could be seen over contaminants has the potential to mirror that seen for storm overflows and could result in a knee-jerk reaction by the regulator.

“If the regulator is not proportionate and the industry were told tomorrow you can’t recycle biosolids to land, incineration is the only viable option. These other technologies, like gasification and pyrolysis, are not quite ready to scale rapidly to meet the demand,” she says.

The regulator’s refusal to allow Northumbrian to proactively invest in incineration for AMP 9 hopefully indicates that it would not force the industry back to the technology lightly.

“The regulators tend to have a more proportionate approach to things. Biosolids to land has been done for a very long time and has definitely had benefits so it’s a question of balancing all these environmental trade-offs,” says Georges.

Smith agrees that an immediate outright ban would be disproportionate. “In soil the rate of accumulation of contaminants is very slow. We’ve done a mass balance analysis for PFOS that shows that it won’t achieve its soil screening value for about 180 years, assuming three-year return periods on sludge application. There is time to get this right, let’s not mess it up, get it right and be rational about it.”

However, if it was needed, a decision around investing in incineration would need to be taken in AMP 8, something the regulatory framework has not factored in.

United Utilities, among others, is calling for an uncertainty mechanism for biosolids to be granted for PR24, saying in its business plan: “In contrast to previous AMPs there is a significant risk that there will be insufficient landbank for biosolids recycling in AMP 8. We have no clear way to accommodate and plan against such exceptional levels of risk within the PR24 regulatory framework.

“The scale of the investment that would be required if risks manifest as a cost-shock fundamentally threaten the ability of the existing business to deliver the required changes in time.”

UU puts the investment required during AMP 8 should it have to move away from agriculture as £300 million. While some of this would be spent on investing on incineration, it would also help pay to send sludge to landfill – the only immediate viable alternative set out in business plans. A further £700 million would be invested over AMP 9.

“The other alternative is landfill, its restricted and it’s really expensive, or they could just store loads of sludge, but that’s a lot of storage that they would need. They will have to invest in incineration, and it will take five years plus to build one due to planning permission issues,” says Georges.

Returning to incineration would represent a huge step back in terms of resource recovery as incineration only presents the opportunity for expensive phosphate recovery.

Anglian Water says such a move would “jeopardise our net-zero strategy” and “lock us into a low value, high regret solution into the long term”.

Several water companies are clear that investing in incineration and STC technologies is an either/or situation in AMP9 and AMP10, with Anglian putting the value at £400 million for either technology.

Given this, Georges says the priority for water companies should be developing STC technologies. “There’s still work to be done to make sure any of these advanced thermal destruction technologies are ready.

“Do they actually destroy PFAS and microplastics for example? What do we do with the products – if we generate biochar for example, what is the most beneficial use of it? How does regulation view the products, and what are the markets for them?”

Anglian Water is investing £10 million in AMP 8 alongside the other wastewater companies to generate a £100 million research fund to help develop STCs.

“We consider this a low-regret investment as it will provide further evidence to potentially avoid the need to commit to and invest in incineration,” it says.

However, Smith says water companies desperately need to do more on source control if it wants resource recovery to be an option in the future.

“We need to get a grip on these things or we will be incinerating everything. If we don’t get source control on contaminants we can kiss goodbye to the circular economy. And its not just sludge, its solid waste and everything.”

This article first appeared in Utility Week’s Digital Weekly edition. To read the issue in full, click here.