Horse Manure Becomes a Circular Economy Opportunity Through Smart Compost Business Models

Across Europe, the horse has quietly changed professions. Once the backbone of agricultural labour, the continent’s equine population now lives largely for leisure, sport, and therapy, concentrated in peri-urban and suburban settings rather than on working farms. That shift has transformed horse manure from a familiar farm input into a growing logistical, regulatory, and economic headache. A new open-access study published in Waste and Biomass Valorization argues that this underappreciated waste stream could instead become a flexible platform for compost-based products, provided that composting science is deliberately married to business model design. Led by Daniel Pleissner of Leuphana University of Lüneburg, together with Paula Podßun, Paul Hölscher, and Henning Friege, the research combines a comparative analysis of horse manure composting with a systematic mapping of compost products, applications, and organisational models across European Union member states.

The scale of the material is far from trivial. An adult horse of roughly 500 kilograms produces an estimated 20 to 31 kilograms of manure and bedding per day, amounting to some 9 to 11 tonnes annually. In regions with dense horse populations, those figures rival municipal bio-waste streams. The County of Wesel in Germany’s Lower Rhine basin, for example, counts more than 8,500 horses alongside 458,000 inhabitants; in 2024 the area collected 32,700 tonnes of bio-waste and 23,300 tonnes of green waste, while horse manure is estimated at around 75,000 tonnes. Yet because many stables sit far from farmland that could recycle those nutrients, manure increasingly generates disposal costs and storage constraints rather than agronomic value.

Chemically, horse manure is a distinctive feedstock. Pure manure contains about 1.0 to 1.7 percent nitrogen on a dry basis, much of it water-soluble and plant-available, along with 0.5 to 1.3 percent phosphorus as P2O5, roughly 1.1 percent potassium as K2O, and 84 to 95 percent organic matter. Its carbon-to-nitrogen ratio typically ranges from 20:1 to 32:1, but bedding materials such as straw or wood shavings can push mixtures above 50:1. That matters agronomically: high C:N materials trigger net nitrogen immobilisation in soil, reducing short-term plant-available nitrogen and potentially depressing yields. If manure is marketed as a fertiliser substitute, customers may perceive weak or even negative fertiliser effects, undermining willingness to pay. The bedding is therefore not a passive bulking agent but a design variable that shapes composting behaviour, nutrient dynamics, and ultimately market positioning.

Controlled composting resolves many of these problems. Thermophilic phases thermally degrade pathogens, parasite eggs, and weed seeds, while microbial activity stabilises labile nitrogen compounds into more predictable, plant-available forms. Finished horse manure composts reported in the literature contain total nitrogen of 1.7 to 2.3 percent, phosphorus up to 1.3 percent, potassium around 1.2 percent, and a near-neutral pH of 6.4 to 6.7, with the C:N ratio falling from an initial 27.3:1 to roughly 15.9:1 and moisture dropping to between 8 and 15 percent. Practical benchmarks, such as the German Organic Waste Ordinance, converge on sustaining temperatures above 55 degrees Celsius for more than two weeks. Studies of small-scale composting of manure with wood shavings show that weekly turning improves hygienisation uniformity, since outer pile layers can otherwise remain insufficiently sanitised. That quality assurance is what opens quality-sensitive horticulture, landscaping, and growing-media markets to manure-derived products.

Emissions, however, constitute the central technical trade-off. Composting generally suppresses methane relative to passive storage because aerobic conditions inhibit methanogenesis, but poorly managed piles can still release considerable methane. Meanwhile, ammonia volatilisation and nitrous oxide emissions can rise, eroding the product’s nitrogen content and contributing to eutrophication and climate forcing. Turning aerates the pile and cuts methane, yet can simultaneously increase ammonia losses by exposing ammonium-rich zones during thermophilic, alkaline phases. Research on dairy manure even shows that pile mixing can raise total measured greenhouse gas emissions while lowering methane alone. The authors conclude that good composting is not a compliance exercise but a core production competence: process control determines hygiene, nitrogen retention, odour, and customer-perceived value. Facilities with optimal aeration and exhaust gas treatment are preferable, which favours centralised processing where horse density or cooperative logistics allow efficient feedstock aggregation.

The systematic EU mapping reveals a structured, application-driven compost market in which soil improvement dominates, followed by fertilising functions and a smaller but meaningful segment for growing-media components. Solid composts prevail, while compost-biochar blends and vermicomposts are increasingly documented. Application fields extend beyond agriculture into horticulture, landscaping, urban greening, engineered soils, remediation, and green roof substrates. That breadth is strategically significant for horse manure, because peri-urban stables are often spatially closer to urban green infrastructure markets than to bulk agricultural outlets, reducing transport costs and enabling circularity branding that raises willingness to pay. The trade-off is that these markets demand higher product consistency and safety, reinforcing the case for controlled composting and rigorous quality management rather than passive pile storage.

Organisational form emerges as a decisive determinant of economic viability. Centralised private plants exploit economies of scale and professional quality assurance but require collection logistics and sufficient horse density. Municipal and public-private systems monetise composting partly through avoided disposal costs and internal use of compost in public green spaces, aligning well with the peri-urban geography of horse keeping. Decentralised models suit small holdings with limited investment capacity, where the business case rests on avoided container rental, haulage, and disposal contracts rather than product sales, though governance mechanisms are needed if products leave the site. Notably, the literature review found no documented cases of co-composting horse manure with municipal bio-waste, despite the apparent synergy: blending manure with kitchen and garden waste would raise nitrogen and potassium in the finished compost and could improve the economics of both streams.

Product differentiation offers the most promising frontier. Vermicomposting can unlock premium horticultural markets through higher microbial activity and nutrient availability, but it demands prior hygienisation and careful process management, raising complexity and risk. Compost-biochar blends present a more scalable strategy: biochar incorporated during composting improves nutrient retention and microbial habitat, and its carbon can persist in soils for decades to centuries, qualifying as a plausible carbon dioxide removal pathway. Voluntary carbon markets have begun recognising biochar-based removals, suggesting that carbon monetisation is more credible in compost-biochar models than in composting alone, provided monitoring, reporting, and verification frameworks are in place. Formulation design also follows application logic: fertiliser-oriented composts target C:N ratios of 8:1 to 12:1, soil improvers sit between 12:1 and 18:1, and carbon-storage or remediation blends exceed 18:1, often above 30:1 with woody biomass or biochar.

Regulation threads through every business model. Under the EU Fertilising Products Regulation (Regulation (EU) 2019/1009) and national frameworks such as Germany’s Fertilizer Act, Fertilizer Ordinance, and Bio-waste Ordinance, requirements for storage capacity, spreading periods, and waste classification shape what is legally and commercially feasible. Directive 2008/98/EC mandates separate biowaste collection, and the EU Soil Strategy for 2030 raises demand for organic matter inputs in degradation-prone regions such as Southern Europe. The authors’ central message is that viable models must treat regulatory conformity and quality assurance as core capabilities enabling market access, not external constraints. Horse-specific data on emissions, pharmaceuticals, and antibiotic resistance genes remain sparse compared with cattle and pig systems, and systematic evaluation of decentralised peri-urban systems is scarce. Future work combining horse-specific process monitoring with economic modelling across organisational structures would strengthen the evidence base for policy and investment. The larger conclusion is striking: Europe’s horse manure problem is really a design problem, and its solution lies in engineering purpose-built compost products, organisational models, and carbon strategies around the material’s distinctive chemistry.

Subject of Research: Business models for utilising horse manure through compost-based value chains in the European Union

Article Title: Business Models for Horse Manure Utilisation in the European Union: Compost-Based Products, Market Pathways, and Carbon Integration

Article References: Pleissner, D., Podßun, P., Hölscher, P., & Friege, H. (2026). Business Models for Horse Manure Utilisation in the European Union: Compost-Based Products, Market Pathways, and Carbon Integration. Waste and Biomass Valorization. https://doi.org/10.1007/s12649-026-03776-9

Image Credits: AI Generated

DOI: 10.1007/s12649-026-03776-9

Keywords: horse manure, composting, circular economy, soil improver, biochar, carbon credits, peri-urban agriculture, EU Fertilising Products Regulation, waste valorization, growing media, greenhouse gas emissions, business models