The Soil Economy: Why Healthy Land Is the Backbone of Circular Agriculture

When we talk about the circular economy, we tend to think of recycling systems, renewable energy installations, or closed industrial production chains. But there is one resource without which the entire system collapses and it lies right beneath our feet. Soil is not simply a growing medium for crops. It is a living system, arguably the most complex ecosystem on Earth, and at the same time the very foundation on which the entire bio-circular model rests. Without healthy soil, the circular flows we design on paper have no place to begin.

The problem is that for decades we have treated soil as if it were an inexhaustible resource. Industrial agriculture of the twentieth century was built on the logic of linear consumption: take, grow, sell and compensate for destroyed fertility with synthetic fertilisers year after year. This approach worked in the short run. It increased yields, fed growing populations, and made farming look efficient. In the long run, it has brought us to a quiet but deepening crisis, one that rarely makes headlines but shapes the future of food security more than almost any other factor.

“Soil is not a dirty material. It is a bank account from which agrarian civilisation has been making withdrawals without ever making deposits.”

What kills soil, and how quickly

According to the Food and Agriculture Organisation of the United Nations (FAO), more than one third of all soils on the planet are already degraded: through erosion, salinisation, compaction, depletion of organic matter and chemical pollution. The numbers are sobering: nature needs between 100 and 1,000 years to form a single centimetre of fertile topsoil. We are capable of destroying that same layer within a single generation of intensive farming.

24 billion tonnes of fertile topsoil lost to erosion every single year worldwide (FAO estimate)

Erosion is the most visible enemy. Unprotected bare soil is washed away by rain and blown away by wind. Globally, the world loses around 24 billion tonnes of fertile topsoil annually: an amount irreplaceable on any human timescale. But erosion is not the only threat. There is a less visible, equally destructive process at work: the steady decline in soil organic matter content.

It is humus that makes soil truly alive. This dark, spongy layer of decomposed organic material retains water, provides physical structure, regulates temperature, stores nutrients, and serves as the home of billions of microorganisms. It is, in a very literal sense, the engine of soil fertility. Intensive tillage breaks it apart and accelerates its oxidation. Monoculture, growing the same crop in the same field season after season, depletes the biological diversity that sustains it. Together, these practices strip soil of its living character and reduce it to a chemical substrate that requires ever-increasing doses of external inputs just to produce the same yields.

The economic logic of this approach is deceptive. Cheap synthetic fertilisers and pesticides made degradation invisible for decades, masking the loss of natural fertility with chemical substitutes. But as soil health declines, input costs rise, water retention falls, and vulnerability to extreme weather increases. The hidden costs are being paid, just not always by those who caused the damage.

Soil as a bioreactor: the microbial economy underfoot

To understand what is at stake, it helps to think of soil not as a physical material but as a living community: a vast, self-organising bioreactor operating at a scale we are only beginning to comprehend. A single handful of healthy soil contains more living organisms than there are people on Earth. Bacteria, fungi, protozoa, nematodes, mites, springtails, earthworms: together they form a complex and interdependent food web that transforms organic residues into available nutrients, breaks down toxins, aggregates soil particles into stable structures, and regulates the flow of water and air through the profile.

Mycorrhizal fungi play a particularly important role in this underground economy. These symbiotic organisms weave their hyphae, hair-thin filaments, through the soil and into plant roots, effectively extending the root system hundreds of times over. In exchange for sugars supplied by the plant, the fungi help access water and phosphorus from pockets of soil that roots alone could never reach. Research consistently shows that plants living in mycorrhizal symbiosis better withstand drought, disease, and environmental stress. Disrupting the fungal mycelium, even through a single deep tillage pass or a broad-spectrum fungicide application, can take years to recover.

Soil microbial diversity is not a scientific abstraction. It is practical infrastructure that can substitute for tonnes of synthetic fertilisers, if we let it function.

Earthworms, often overlooked, are the soil’s primary engineers. A healthy population can turn over several tonnes of soil per hectare each year, creating channels that improve drainage, aeration and root penetration. Their castings, material that passes through their digestive system, are far richer in available nutrients than the surrounding soil. Yet intensive tillage and pesticide use have reduced earthworm populations by up to 80 percent in many European agricultural regions over the past 50 years.

Regenerative agriculture: returning to the closed loop

Regenerative agriculture is neither nostalgia for a pre-industrial past nor a rejection of modern productivity goals. It is a systemic approach that builds fertility rather than consuming it, one that works with biological processes instead of overriding them with chemistry. Its core principles are well known among practitioners: minimal soil disturbance, permanent soil cover, diversified crop rotations, retention of organic residues, and the thoughtful integration of livestock.

Cover crops are among the most powerful tools in the regenerative toolkit. Sown after the main harvest crop, they protect bare soil from erosion through the winter months, suppress weed pressure, and in the case of legumes, actively fix nitrogen from the atmosphere. When terminated and incorporated or left to break down on the surface, they return organic matter to the soil and feed the microbial communities that drive fertility. This is a textbook closed loop: the plant takes from the soil and gives back in equal or greater measure.

+20 to 40% improvement in water-holding capacity observed in soils managed regeneratively for five or more years (Rodale Institute, 2023)

Livestock integration is another mechanism of profound importance. Rotational grazing, moving animals systematically between paddocks and allowing adequate recovery time, stimulates grass growth, encourages deep root development, and deposits manure evenly across the land. When managed well, grazing animals do not degrade grassland; they regenerate it. Farms that have reintegrated livestock into their crop rotations report measurable improvements in soil carbon, water infiltration and biological diversity within just a few seasons.

No-till and minimum-till approaches reduce the physical disruption of soil structure. By leaving the soil largely undisturbed, farmers preserve the mycelium networks, earthworm burrows, and aggregate structures that took years to form. Combined with cover cropping and diverse rotations, reduced tillage allows the soil food web to stabilise and expand over time. The transition can be challenging in the first years, yields may dip, and new management skills are required, but the long-term trajectory is consistently positive for both productivity and resilience.

Carbon farming and new financial incentives

Soil is one of the largest natural carbon reservoirs on the planet. Globally, soils hold approximately twice as much carbon as the entire atmosphere. When soils are degraded, this carbon is released as CO², accelerating climate change. When soils are restored and managed regeneratively, they actively draw carbon down from the atmosphere and lock it in stable organic forms, a process known as soil carbon sequestration.

1.5 – 5 Gt CO² could be sequestered annually through global soil restoration, comparable to the yearly emissions of entire industrial nations (Nature, 2023)

According to estimates published in Nature, restoring and regeneratively managing the world’s agricultural soils could sequester between 1.5 and 5 billion tonnes of CO² per year. Soil is not a marginal climate tool, it is one of the most powerful levers available to us, and one of the few that simultaneously improves food security, water resilience and biodiversity.

This potential is beginning to attract serious financial attention. Carbon markets, in which companies and governments pay for verified carbon sequestration to offset their own emissions, are expanding rapidly, and agriculture is increasingly seen as a viable source of high-quality credits. Farmers who can demonstrate, through soil sampling and digital monitoring, that they are building organic carbon in their fields can now earn additional income from that activity, income entirely independent of commodity prices or yield fluctuations.

Several promising models are emerging: farmer cooperatives that aggregate credits across many smallholders, digital platforms that automate monitoring and verification, and government schemes that pay for regenerative practices directly. The architecture of a genuine soil economy, one that rewards land stewardship rather than simply output, is being built.

From theory to the field: what is already working

Across Europe and beyond, regenerative and soil-focused farming is moving from niche to mainstream. In France, the “4 per 1000” initiative unites farmers, scientists and policymakers around the goal of increasing soil organic carbon content by 0.4% per year across agricultural land. If achieved globally, this single change would fully offset humanity’s annual CO² emissions. In the Netherlands, farmer cooperatives use digital platforms to measure and sell soil carbon credits collectively, turning soil health into a reliable revenue stream.

In Ukraine, and this is particularly relevant for the AGRI-BIOCIRCILAR-HUB’s network, the opportunity is enormous. Ukrainian black soils, the chornozem, were once considered among the richest agricultural soils in the world. Decades of intensive farming have significantly reduced their organic matter content. But the biological potential remains. Restoration programmes, paired with circular farming approaches, biogas digestate as fertiliser, cover cropping, reduced tillage, could rebuild that fertility within a generation.

Technology is also transforming what is possible. Remote sensing satellites now map soil organic carbon at field level. On-farm sensors measure moisture, temperature and biological activity in real time. Digital soil health platforms allow farmers to track progress over years and benchmark against regional averages. Precision agriculture, far from being in tension with regenerative principles, is becoming its most powerful enabler.

Restoring soil is not a cost. It is the longest-return investment the agricultural sector can make, and the only one whose returns compound indefinitely.

Where all the threads meet

The three previous essays in this series explored the bio-circular economy from different angles: the systemic shift it represents, the role of small farms as change-makers, and the biogas revolution that turns organic waste into energy and fertiliser. Soil is where all these threads converge. Biogas digestate is one of the most effective tools for rebuilding soil organic matter. Cover crops grown by small farms are a primary mechanism for building soil carbon. The systemic principles of the bio-circular economy only hold if the foundational resource, soil, is treated as part of the loop rather than a linear input.

Without healthy soil, there is no sustainable harvest, no quality organic matter to compost, no substrate for biogas production, no roots for the nutrient cycle to anchor to. Soil is not one element among many in the bio-circular system. It is the system’s ground condition, the thing that makes everything else possible.

Conclusion: start from the bottom

Turning attention back to the soil means shifting the horizon of thinking: from quarterly profit to decades, from this year’s yield to the fertility of future generations. It means measuring success not only in tonnes per hectare, but in earthworms per square metre, in organic matter percentage, in water retained after a summer storm.

This is not easy under the pressures of commodity markets and agricultural policy cycles calibrated to annual budgets. But it is the only path on which farming can become truly circular, not merely in the way it handles its outputs, but in the way it relates to the living system that makes everything else possible. Soil is not an input. It is a partner. And like any partnership, it requires care, reciprocity, and a long-term commitment to mutual flourishing.