Written evidence submitted by Professor Johnson, Professor Tony Roskilly, Professor Simone Abram, Ms Lisa Hodgson, Rachael Richards from Durham University and Maggie Bosanquet, Richard Hurst of Durham County Council (SH0020)


  1. How can the Government measure progress towards its goal of making all soils sustainably managed by 2030? What are the challenges in gathering data to measure soil health how can these barriers be overcome? 


1.1              We propose that in order to measure progress in this area we don’t focus on measuring soil health. To explain, soil health, like human health is difficult to define. Indeed the parallels between human and soil health are prescient as both are heavily influenced by a healthy microbiome. Even with human health, where we do measure things like mass and blood pressure, ultimately we take a holistic approach, we take a systems-based approach where we supply macro and micronutrient inputs via a diverse diet which ensures a healthy gut microbiome which generally ensures a healthy individual. In soil, a healthy microbiome can be defined as “maintains a high diversity of functions across a range of organisms having as broad a range of traits as possible” (Johnson et al 2022a) The functions that soil delivers of course depend on the needs of society, but include food provision, carbon storage and flood resilience as well as provision of a healthy ecosystem. Soil science like medicine has become too complicated and even soil scientists don’t understand all the different chemical, physical and biological components of soil health.


1.2              For this reason, we propose that we adopt the precautionary principle around the issue of soil health in order to make progress towards achieving healthy soils by 2030. Instead of debating what is the best way to measure soil health the precautionary principle enables decision-makers to adopt precautionary measures when scientific evidence about an environmental or human health hazard is uncertain and the stakes are high. The stakes are high as 2/3 of all arable soils are degraded and soil health is currently in a vicious cycle with climate change (see Figure 1). And the scientific evidence for how to measure soil health (or even what it is or how to measure soil organic matter) can be very controversial. This is why Defra have been struggling to develop the soil health metrics. Instead of trying to measure something that is inherently difficult to define and to measure such as soil health, we propose adopting a systems-based approach based on measuring inputs and outputs of carbon and minerals which are the foundation of healthy soils.


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Figure 1 showing the vicious cycle between degraded soil health and climate change (from Johnson et al 2022a A nation that rebuilds its soils rebuilds itself)

  1. Do current regulations ensure that all landowners/land managers maintain and/or improve soil health? If not, how should they be improved? 

2.1 Current regulations do not. We suggest that this is because current regulations contain significant policy disconnects which exist within, not just the wider food and agriculture sector, but indeed the energy sector. Heat and soil vie for the same carbon rich wastes (Johnson et al, 2018). Industries dealing in carbon-rich organic wastes have invested millions in Bioenergy, notably Anaerobic Digestion (AD) and the vast majority of AD produces the biogas methane. The waste material from AD has resulting low C:N (Carbon:Nitrogen) ratios which means when the AD waste (digestate) is returned to the soil, C is lacking. So the plants might be OK as they enjoy high N concentrations but the long term soil health deteriorates due to a lack of carbon. It is this policy disconnect which is arguably most relevant to this Soil Health Inquiry as it creates significant hurdles in the transition to regenerative agriculture (where C:N ratios must be balanced) as well as in us achieving net zero targets using carbon storage in land.


2.2 To improve current regulations and a adopt a more holistic approach to the use of organic rich ‘waste’ materials, we propose that the UK constructs a database detailing the organic resources (often labelled as wastes) and mineral resources (again labelled as wastes) which are available in society. Defra already does this for waste and 2018 figures show that over 50% of all material landfilled (over 100 Mtonnes) is either subsoil or mineral material, much of which could be returned to soils. But this waste database is not seen as a list of potential resources which can be used as part of an ‘asset management plan’ for soil but it should be. Each region could then make evidence-based decisions based on their needs, which of these organic and mineral resources might be added to soil based on what functions/services we require the soil to deliver (food provision, climate change mitigation or adaptation, biodiversity). And then which of the 100Mtonnes of organic resources (see House of Lords report) might still be available for energy generation. At the moment soil is losing out every time.

2.3 The benefits of an inputs and outputs type system for soil management would be that it would be simpler to implement and monitor as it would not require extensive soil (which is very heterogenous both temporally and spatially) testing. The disadvantages are much of the ‘right’ sort of minerals and ‘right’ sort of organic matter material (see Johnson et al 2022a) which would benefit soil and rebuild our terrestrial ecosystems are classed as waste and so policy changes would have to be made. However this has been done before where a case can be made to reclassify wastes as byproducts. Testing waste materials is also a well established process and much simpler than testing soil which is a living ecosystem. If this new system and policy changes were adopted we could ease the transition to regenerative agriculture (see Figure 2). Other rewards of returning missing minerals to soils include ensuring nutritious food then contains important micronutrients like zinc which is currently missing from many diets (eg Gwandu et al 2021). As well as reaping the other ecosystem services which a healthy soil delivers such as flood resilience (eg Kerr et al 2022).



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Figure 2 (from Johnson et al 2022a A nation that rebuilds its soils rebuilds itself) showing the virtuous circle between soil health and climate change mitigation and adaptation.

  1. Will the standards under Environmental Land Management schemes have sufficient ambition and flexibility to restore soils across different types of agricultural land? What are the threats and opportunities for soil health as ELMs are introduced?


Where the ambition is needed is in taking a wholly different approach to ELMs and engaging engineers with soil (Johnson et al 2015). We need to treat soil as a circular system that has a series of required inputs in order to provide the various outputs that society needs (eg bioresources like antibiotics and programmable materials which will underpin many health technologies) as well as providing the various services such as food security (SDG3), climate change mitigation (SDG13) and clean water storage (SDG6). Only then we will have the flexibility to restore a wide range of soil types as this system based approach will allow us to avoid getting mixed up with how to define and measure soil health. At the moment the necessary inputs to soil (the diverse diet it needs) are organic ‘waste’ containing carbon and ‘waste’ minerals which are currently seen as either resources for bioenergy (biomass) or as waste materials to be disposed of by the Water Industry and construction industry. Government, society and industry do not consider the fact that these resources are needed by soil and this must be corrected if the threat of food insecurity is to be avoided. The opportunities of rebuilding soil health by returning organic and mineral materials to soil are numerous. Firstly we know that returning organic material to soils with redox active minerals (such as iron oxides which are widely available across the UK from the Water Industry) benefits carbon storage (Tipping et al 2019). Returning carbon to land was highlighted as essential in the Paris Climate Change agreement and the UK Government signed up to this. The UN have also stated that soil health underpins all 17 SDGs (https://news.un.org/en/story/2018/08/1016902) and so rebuilding our soils to hold water and carbon will help us achieve many of these SDGs within the UK for example protecting our built and rural infrastructure from flooding. The opportunity for the UK lies in linking soil and energy policy through carbon accounting and ensuring that we lead the way in ensuring that soil is not forgotten in the race to keep the lights on.


  1. What changes do we need to see in the wider food and agriculture sector to encourage better soil management and how can the Government support this transition? 


a)      C mapping across industries – The main UK industries who return organic matter to land are agriculture, the Food industry and the Water industry. But in recent years these industries have been heavily influenced by increasing energy prices and have adopted Anaerobic Digestion (AD) as a method of treating their organic wastes before returning them to land. This adoption was driven largely by the Renewable Heat Incentive (now finished) as AD produces the biogas methane which is seen as a renewable energy source which helps industry achieve their own net zero targets. However, AD wastes (digestate) have much lower Carbon:Nitrogen ratios than undigested organic wastes, an unintended consequence has been less carbon being returned to land and also too much nitrogen being returned to the land which can then cause further climate change via nitrous oxide emissions. Detailed mapping exercises by local authorities of the wastes (SDG12) their industries generate are already carried out but we must understand how the carbon is being distributed between bioenergy (SDG7) and land (SDG15). Both might help us achieve net zero targets but at the moment no-one has calculated the trade-off. This baseline information will allow local authorities to best assess how to achieve net zero (SDG13) whilst maintaining and even enhancing critical natural capital such as soil. This baseline survey could align and compliment Defra’s plans to baseline soil health around the UK in order to understand which soils have capacity to hold more carbon or might need more minerals in order to do so (eg Tipping et al 2019). Figure 2 shows how the UK might lead the way in moving from the vicious cycle of degraded soil and climate change (Figure 1) to a virtuous circle.


b)     Innovative methods to return organic wastes to land – Aligning with SDG12 (responsible use of resources and circular economy). We take the majority of our food from soils but we have not been putting the organic wastes (or inorganic mineral wastes) back into the soil. In fact in the UK, we only return 70% of our organic waste streams to the soil (House of Lords, 2014). The maths doesn’t add up and it is soil (and the ecosystem services it provides such as flood resilience and carbon storage) which is losing out. Along with cutting off natures supplies of organic matter and minerals to soil by straightening rivers and building dams, this is part of the reason why our soils are degraded. Of course, not all wastes are suitable and innovative methods are needed to allow us to continue to return wastes like Water Industry biosolids to land.  We suggest examination of this how to reuse organic and mineral wastes through a nexus lens taking into consideration SDG3 (health), SDG7 (energy) SDG12 (wastes) and SDG15 (healthy soils). Roskilly and others have expertise in converting AD plants to produce H2 instead of CH4, thereby keeping the carbon in the waste. More research needs to be carried out in this area to provide much needed underpinning evidence on the pros and cons of the Hydrogen economy including overlapping pros and cons for soil health. The recently launched (Jan 2022) Hydrogen BECCS Innovation Programme which will provide £5M for research into  how to generate hydrogen from biomass (rather than methane) is a step in the right direction as it looks to generate hydrogen rather than methane. But it does not mention soil and indeed the aim of the call is to maximise the potential energy production from the biomass, possibly to the detriment of soil. The biomass has come from the soil and without the return of the biomass to the soil, the missing carbon and other micronutrients are lost from our terrestrial ecosystems (Johnson et al 2022a).


c)      Coordinated community action - Opportunities for community input and engagement around climate change, net zero and soil health need to be explored. Durham has expertise in enhancing community resilience to climate change (see ROBUST project) and extreme events like flooding. It is important to note that urban planning does not successfully take into account community points of view on the transformation of urban soils into sealed surfaces. The opportunities urban soils present for improved human health as well as the provision of its ecosystem services to help with flood resilience are highly relevant to local communities. Many communities, both urban and rural, produce their own food and are exploring opportunities for producing bioenergy but they do so in ignorance of the potential needs of their soils. In addition, communities, local authorities and universities are also keen to be involved in carbon offsetting schemes like tree-planting and ensuring that these trees are planted in the correct place and in the right soils is another potential positive outcome of working with community groups around soil and net zero. There is therefore a need and an opportunity to prioritise coordinated schemes between local authorities, food and water industries and communities for community projects like composting - where high-quality organic matter could be produced and returned in a stable form to arable soils to maintain soil health and flood resilience.


d)     Joined up national/local strategies - Including soil in local authority net zero plans means everyone working together to make soil health play a central role in the Government’s 25 year plan for the natural environment. The Agricultural Bill outlines how agricultural soils will be considered under the Environmental Land Management scheme and be eligible to receive public funds for maintaining public services such as carbon storage and flood resilience. Urban soils are currently excluded from the definition of the natural environment in Defra’s draft 25year Environment plan. We would like to highlight how urban soils can in fact store significant amounts of carbon and with careful management store water but they are particularly vulnerable to degradation because they are currently completely unprotected by UK and international law. Although through Pt2A of the Environment Act, a new site must be investigated to ensure it is fit for purpose and not ‘contaminated’, engineers can and do deal with this by sealing the surface of the soil resulting in a loss of flood resilience and carbon storage potential. Soil sealing usually involves covering the soil surface with concrete; this reduces infiltration of water which in turn causes surface water flow which contributes to urban flooding. In addition, urban soils are what the public comes into contact with most frequently (over 80% of the UK’s population lives in cities) and will therefore be critical in raising the awareness of soil value to the wider population. Urban soils need protecting and should be included in the Environmental Land Management scheme as they form a crucial hydrological link between agricultural soils and a point of contact with nature for 80% of our population.


e)      Education - Generation Z must understand the important linkages between climate change, soil and human health. We propose a hands-on ‘ethics of care’ approach to engage society with soil, piggybacking on existing climate change educational resources. In addition the future of human health depends on food security, which depends on Generation Z wanting to grow food, which in turn depends on soil literacy (see Johnson et al 2022b).


  1. What does UK Government need to do to tackle other stressors on soil health such as soil contamination?


Returning biosolids and other organic resources to land has become a controversial topic in its own right after the Greenpeace FOI request of the consultant’s report to the Environment Agency on this issue a few years ago. Engineers and scientists working together with social scientists have the skills to consider all the issues, biological, chemical, physical and anthropological in order to close the loop for soil. Solutions to tackle stressors such as contaminants will include pre-processing organic waste streams with redox active minerals in order to put stabilised carbon back into soils where it belongs at the same time as ensuring chemical and biological toxicity is removed (eg Finlay et al 2021).  With the Paris Climate Change talks having made carbon storage in soils an explicit part of the agreement it is fundamental that we take this opportunity to understand and explore the not only fate of soil organic carbon but also persistent organic chemicals like Antimicrobial Resistance in our soils.


  1. The Team - this evidence submission is based on the research findings of Professor Johnson’s research around soil health in conjunction with research on bioenergy (green hydrogen) by Roskilly and Abram and the local authority expertise of Durham County Council in implementing net zero polices and engaging with communities on the UN’s Sustainable Development Goals SDG7, SDG13 and SDG15. Professor Johnson is an expert on carbon sequestration in soil minerals (eg Johnson et al, 2015, Johnson et al, 2018, Gwandu et al 2022, Johnson et al 2022a) and is passionate about the role engineers can play in developing a systems based approach to soil health so that we can address both climate change adaptation and mitigation. Professor Roskilly is an expert in low carbon heat provision. Professor Abram is an expert in energy use in society. Johnson, Roskilly and Abrams have worked with the Durham Energy Institute to identifiy current policy disconnects around achieving net zero carbon (SDG13) whilst maintaining healthy soils (SDG15) and providing sustainable energy (SDG7).  Durham County Council (DCC) believe a wider critique of the disconnects between soil and energy policies (not just food and agriculture) is essential not just for soil health but if local authority net zero policies are to be successful. Whilst soil is included in the DCC net zero plans, (‘Consider how soil conservation, soil regenerative farming, and agro-ecology can be promoted with farmers and landowners’), it is considered that given soil is the largest reservoir of organic carbon (after fossil fuels), further refinement of this action would be beneficial hence DCC’s input to this soil health inquiry.




  1. Relevant publications


Finlay, Nina C., Peacock, Caroline L., Hudson-Edwards, Karen A. & Johnson, Karen L. (2021). Characteristics and Mechanisms of Pb(II) Sorption onto Fe-rich waste Water Treatment Residue (WTR): A potential sustainable Pb immobilisation technology for soils. Journal of Hazardous Materials 402: 123433.

Gwandu, T., Blake, L. I., Nezomba, H., Rurinda, J., Chivasa, S., Mtambanengwe, F. & Johnson, K. L. (2021). Waste to resource: use of water treatment residual for increased maize productivity and micronutrient content. Environmental Geochemistry and Health

House of Lords Science and Technology Committee. (2014) Waste or resource? Stimulating a bioeconomy.Available online: http://www.publications.parliament.uk/pa/ld201314/ldselect/ldsctech/141/141.pdf [Accessed 4th August 2014]

Johnson, Karen L., Gray, Neil D., Stone, Wendy, Kelly, Bryce F.J., Fitzsimons, Mark F., Clarke, Cathy, Blake, Lynsay, Chivasa, Stephen, Mtambanengwe, Florence, Mapfumo, Paul, Baker, Andy, Beckmann, Sabrina, Dominelli, Lena, Neal, Andrew L. & Gwandu, Tariro (2022a). A nation that rebuilds its soils rebuilds itself- an engineer's perspective. Soil Security 7: 100060.

Johnson, K. et al (2022b) Boosting soil literacy in schools can help improve understanding of soil-human health linkages in Generation Z. doi: 10.3389/fenvs.2022.1028839

Johnson KL et al (2015). Nature Communications 6, Article number: 7628 doi:10.1038/ncomms8628

Johnson KL et al (2018). Nature Communications . Article number

Kerr, Heather C., Johnson, Karen L. & Toll, David G. (2022). Reusing Fe water treatment residual as a soil amendment to improve physical function and flood resilience. SOIL 8(1): 283-295.

ROBUST: https://www.dur.ac.uk/ihrr/robust/

Tipping and Rowe (2019) Modelling the physical states, element stoichiometries and residence times of topsoil organic matter, https://doi.org/10.1111/ejss.12785



February 2023