Managing Horse Manure Biogas Plants: A Practical Guide for Operators

Horse manure biogas plants are facilities where microorganisms break down horse manure in the absence of oxygen to produce methane-rich biogas. This gas can be used to generate electricity or heat, or refined as a transportation fuel. For equestrian facilities and agricultural operations with access to regular manure supply, a well-managed biogas system transforms what was once a waste disposal problem into a reliable renewable energy asset.

This guide is written for biogas plant operators and equestrian facility managers who need practical, actionable information on how these systems work, what daily maintenance tasks are essential, and what results to expect. Whether you’re running an existing horse manure biogas plant or considering one, understanding the operational realities will help you maximise efficiency and avoid costly downtime.

Why Horse Manure Matters for Biogas

Equine operations produce enormous quantities of manure. The average horse weighing 500 kg produces approximately 25 kg of manure daily, and in stabled facilities, an additional 4 to 7 kg of waste bedding is added to this output. Across the UK alone, with approximately 850,000 horses, this represents a substantial biomass resource.

Currently, the primary use for horse manure in the UK remains agricultural—as a field fertiliser. However, under UK environmental legislation, horse manure can also be processed as biomass feedstock for anaerobic digestion to produce methane. This dual pathway creates both an environmental opportunity and a potential income stream.

A single horse’s daily manure output, combined with suitable bedding, possesses significant energy content. To put this in perspective: in 2019, during the FEI World Cup Jumping event in Helsinki, Finland, 100 tonnes of horse waste yielded enough biogas to power the entire event and produce surplus energy that was redirected to the grid to heat Finnish homes. One horse’s daily waste output was enough to heat a family home for a day.

How Anaerobic Digestion Works

At the heart of every biogas plant lies a carefully controlled biological process. Inside the digester tank, bacteria and archaea (microscopic organisms) break down organic matter—in this case, horse manure and bedding—in an oxygen-free environment. This process produces two main gases: methane (CH₄) and carbon dioxide (CO₂).

Figure 1: Schematic representation of an anaerobic digester system for horse manure biogas production, showing key monitoring points and safety equipment.

The Digestion Process: Four Stages

Acid-forming bacteria begin the work first, breaking down volatile solids and converting them into simple fatty acids. Methane-forming bacteria (methanogens) then convert these acids into methane and carbon dioxide. This process is described in more detail in our process stages of anaerobic digestion article.

Temperature is critical. Biogas bacteria produce gas most efficiently within two distinct ranges as discussed in detail in our mesophilic and thermophilic article.

Gas production drops significantly outside these temperature windows. Maintaining consistent temperature is one of your most important daily tasks.

pH balance also matters. Bacteria thrive in a slurry with a pH around 7.0 (neutral). Under normal, stable conditions, the digestion process self-regulates acidity and alkalinity. However, sudden changes to feedstock or operating conditions can disrupt this balance and cause digestion to slow or stall.

Horse Manure vs. Other Manures: What You Need to Know

Horse manure is a valuable biogas feedstock, but it differs from cattle or pig manure in important ways.

Horse manure produces less methane than ruminant manures (cattle and sheep). This is because horses digest their feed differently—as hindgut fermenters rather than ruminants—which changes the chemical composition of their manure. The microbes that pass through a horse’s digestive system are less suited to methane production in the biogas digester.

Bedding compatibility is a real constraint. Traditional bedding materials such as straw, sawdust, and wood shavings contain lignin and cellulose, which are difficult for the anaerobic digestion process to break down. These materials can accumulate in the digester and cause operational problems. Many successful horse manure biogas operations either use alternative beddings (such as rubber mats or paper-based materials) or blend horse manure with other feedstocks (such as cattle manure or food waste) to balance the carbon-to-nitrogen ratio and improve gas yields.

Stable population density matters. Biogas plants require consistent, reliable feedstock. A single horse may not produce enough manure to justify a digester. Most viable horse manure biogas operations either serve multiple horses (such as riding schools or stables with 50+ animals) or operate at a regional scale where manure is collected from several facilities within a short distance.

Figure 2: Blended feedstock approach improves gas yield and system stability compared to horse manure alone. (When adding food waste a pasteurisation stage and a waste permit will often be required. Feedstock ratios given will vary according to feedstock C:N analysis.)

The Digestate: A Valuable By-Product

What many operators overlook is the digestate—the solid and liquid residue left after biogas is produced. This is not waste; it is a high-quality organic fertiliser with significant plant-available nutrients.

Digestate contains nitrogen, phosphorus, and potassium in forms that plants can readily absorb. Because the digestion process has already broken down much of the organic matter, digestate acts more quickly than raw manure and smells far less. For equestrian facilities with grazing land, digestate can replace purchased fertiliser or be sold to neighbouring farms, creating an additional income stream or cost offset.

This circular economy benefit—converting manure into energy while producing a premium fertiliser—is one reason why horse manure biogas is attracting renewed interest in Europe and beyond.

Real-World Examples: Horse Manure Biogas in Practice

Germany: Südergellersen – A Successful Turnaround

In August 2018, the biogas specialist Weltec Biopower took over a 2.2-megawatt horse manure biogas plant in Südergellersen, Lower Saxony, that had gone into liquidation. The original plant, built in 2009 and expanded in 2014, was based on a simple concept: digest horse manure and sell the digestate as fertiliser pellets. However, the idea proved technically difficult and economically unviable under those constraints.

Weltec restructured the operation with a blended feedstock approach. The two digesters (each 3,000 m³ capacity) are now fed primarily with renewable raw materials and horse manure from local suppliers within a 15 km radius. By combining manures and balancing the substrate mix, the plant improved both gas yield and operational stability.

The biogas runs two cogeneration units producing 1.1 MW of electricity each, feeding power to the public grid. The exhaust heat from cogeneration is used to dry the digestate, reducing moisture and transport costs. This modernised operation demonstrates that horse manure biogas can work profitably, but it requires technical expertise, blended feedstocks, and careful management.

Finland: From Manure to Event Power

During the 2019 FEI World Cup Jumping qualifier in Helsinki, the Finnish energy company Fortum demonstrated the potential of equestrian biogas on a large scale. 100 tonnes of accumulated horse waste from the event was processed to produce electricity and heating energy, with surplus energy fed into the grid to warm local homes. According to the FEI press release, the energy equivalent was such that 20 millilitres of horse waste could recharge a smartphone, and one horse’s daily output was sufficient to heat a family home.

This high-profile success underscored a key insight: horse manure biogas works best where there is a temporary or permanent concentration of horses (equestrian events, riding schools, studs, or racing facilities) and access to end-use markets for the energy produced.

India: Matheran Hill Station

In 2017, the Matheran Hill Station Municipal Council in India commissioned a biogas plant fuelled by horse manure from the 460 horses and ponies used for local tourism. The trial, conducted by the Bhabha Atomic Research Centre, proved successful. The resulting biogas powers streetlights throughout the hill station, demonstrating how a local, decentralised approach can work in developing-world contexts.

Muckbuster SEAB MB400 Digester

The Muckbuster® digester unit has been suggested as a solution in a Swedish Technical Paper for turning slurry and similar farm waste into energy in the form of electricity and heat, whilst generating high-value fertiliser as a by-product.

Daily Operations and Maintenance: What Operators Actually Do

Running a biogas plant is not a hands-off operation. Every day, operators perform visual inspections, monitor key parameters, and log data to catch problems before they become costly failures. The difference between a plant running smoothly and one that experiences unplanned downtime often comes down to these daily habits.

The reality is this: Biogas plant operation is a specialised skill that demands attention to detail, consistency, and a structured approach. Many operators who struggle do so not because the technology is flawed, but because they lack a reliable system for tracking and completing essential daily tasks. A simple checklist—whether on paper or digital—can be the difference between smooth operation and costly downtime.

A structured daily routine ensures consistent plant performance and helps operators spot problems early.

Morning System Health Checks (Daily)

Before any digestion occurs, begin with a safety briefing. Check that all personal protective equipment is available, review the overnight shift report, and identify any known issues or alerts.

Digester exterior and vents: Walk around the digester tank. Look for visible leaks, corrosion, or distortion of the tank walls. Use your nose—an unusual odour can signal a developing problem. Ensure all vent pipes are clear and there are no blockages.

Temperature and pressure gauges: Read the digester’s temperature and pressure gauges. Mesophilic digesters should read 37–41°C; thermophilic, 50–55°C. Pressure should remain in the 0–5 mbar range. Any deviation of more than ±2°C or ±2 mbar from your baseline should prompt investigation.

Engine compartment checks: If your plant includes a combined heat and power (CHP) engine, visually inspect for leaks of oil, coolant, or gas. Check the coolant level in the expansion tank (it should be between the minimum and maximum marks). Touch the bearing housing on pumps and mixers to confirm they are not abnormally hot (bearings should stay below 75°C).

Gas handling system: Test that the condensate drain in the gas lines operates freely. Condensate backup can reduce gas quality and damage equipment. Verify that your gas pressure and flow readings are consistent with recent baselines. If gas pressure drops suddenly or flow reaches zero, investigate immediately.

Safety systems: Confirm that gas detection panels show all zones green with no fault indicators. Check that fire extinguishers and eye wash stations are accessible, have intact seals, and display pressure gauges in the green zone. Inspection tags should be current.

Each of these checks should take less than five minutes per asset and should be logged. Digital logging (with photo verification where possible) creates an auditable record and helps you spot trends over time.

Feedstock Preparation and Feeding (Daily to Weekly)

Consistency is key. The digester needs a regular, predictable feed schedule. Sudden, large additions of fresh material can upset the bacterial community and cause gas production to drop or stop.

Monitor your feedstock composition. If bedding material is accumulating or if you are adding new types of manure or co-substrates (such as food waste), document the change and watch digester temperature and gas output closely over the next 3–5 days. This lag time is normal—the system takes time to adjust to new feedstock.

If you are using solid bedding: Pre-process it where possible. Some operators grind or shred straw and wood materials to increase surface area for bacterial breakdown. Others have switched to alternative beddings that are easier to digest (such as compostable paper or recycled plastic mats).

Manage your loading rate. This is the amount of organic matter (volatile solids) you add to the digester each day, usually expressed as kilograms per cubic metre per day. Overloading—adding too much too fast—is one of the most common mistakes. It acidifies the digester and can cause methane production to drop. Better to feed a little less consistently than to overload and then back off.

Weekly System Performance Checks

Once or twice per week, take time for a more thorough review:

• Gas quality sampling: Collect a gas sample and measure methane content. Pure biogas should contain 50–70% methane and 30–50% carbon dioxide. If your methane percentage drops significantly, this signals that the bacterial balance is shifting, often due to temperature swings, pH drift, or feedstock imbalance.
• Digester slurry parameters: Many operators periodically sample the digester slurry to measure pH, volatile fatty acid levels, and ammonia concentration. A pH below 6.8 or above 7.5 indicates the digester is becoming unstable.
• Engine and equipment performance: Review the cogeneration engine’s runtime, electrical output, and exhaust temperature. Note any unusual vibration, noise, or changes in output. Modern biogas plants often log this data automatically via SCADA (supervisory control and data acquisition) systems, so review the weekly summary.
• Digestate removal and storage: Ensure that digestate is being removed at the rate it is being produced. Overflow or pooling inside the digester will cause it to malfunction.

Scheduled Maintenance (Monthly and Seasonal)

Pump seal inspection: Seals on substrate pumps and circulation mixers can wear over time. Inspect them monthly for visible leaks.

Filter and intake cleaning: If your feedstock system includes filters or intake screens, clean them monthly or more often if you are processing high-solids material (such as straw-heavy bedding).

Engine servicing: CHP engines require regular oil and filter changes. Follow the manufacturer’s schedule (typically every 500–1,000 operating hours). Neglecting engine maintenance is a common cause of unexpected shutdowns.

Heating system checks: If your digester is heated via a hot-water loop from the engine, check the heating system in winter and before seasonal changes. Poor heat transfer can cause the digester temperature to drift.

Troubleshooting: Common Operational Problems and Solutions

Gas Production Drops Suddenly

Likely causes:

• Temperature drop (check digester thermostat and heating system)
• Feedstock change (if you switched bedding type or added new manure sources recently)
• pH drift (acidification from overloading or alkalinity from excessive lime addition)
• Ammonia spike (excess protein in feedstock, or high feedstock nitrogen content)

Initial response: Stop adding fresh feedstock for 2–3 days and allow the digester to stabilise. Increase the digester temperature by 1–2°C (if using a heater). Reduce your feeding rate by 20–30% for the next week and monitor gas output daily.

Unpleasant Odours (Rotten Egg or Sewage Smell)

Likely cause: Hydrogen sulphide (H₂S) production, often from excess sulphur in the feedstock or incomplete digestion.

Response: Check your recent feedstock additions. If you added new sources of manure or bedding, this may be the source. Reduce feeding rate and ensure thorough mixing. Some operators add small amounts of iron oxide or biochar to absorb H₂S, though consult a biogas specialist before experimenting with additives.

Engine Shutdown or Reduced Output

Likely causes: Gas quality issues, fuel system blockage, or engine sensor faults.

Response: Check gas pressure and flow immediately. If gas pressure is below the engine’s minimum requirement, the engine will not run. Inspect the gas line for condensate backup or line blockages. If the engine runs but produces less electricity than usual, this may indicate incomplete combustion due to poor gas quality (too much CO₂, not enough CH₄). Review recent digester parameters and feedstock changes.

Building a Sustainable Operation: Key Success Factors

1. Invest in monitoring and control systems. Modern biogas plants benefit enormously from SCADA systems that automatically log temperature, pressure, gas flow, and engine performance. These systems allow you to spot trends and problems early and, in some cases, make automatic adjustments (such as increasing digester heating if temperature drifts).

2. Plan your feedstock strategy. Horse manure alone may not yield optimal biogas. Consider blending with cattle manure, food waste, or other agricultural co-substrates. This improves gas yield, stabilises the digestion process, and makes the operation more economically viable. However, each new feedstock type requires careful introduction and monitoring.

3. Standardise your daily routine. A structured checklist—whether on paper or digital—ensures nothing is missed. Many operators use mobile apps that log photos and timestamps, creating an auditable record that is invaluable if problems arise or during regulatory inspections.

4. Train your team. If multiple people operate the plant, ensure that all operators understand the same procedures, safety protocols, and how to recognise warning signs. Inconsistent operation is a common source of problems.

5. Keep detailed records. Log feedstock type and quantity, digester temperature and pressure, gas production, engine output, and any maintenance performed. Over weeks and months, this data reveals patterns and helps you optimise your operation. It is also essential for demonstrating compliance with environmental regulations.

6. Plan for digestate management. Know in advance how you will store and use (or sell) the digestate. This by-product can be a profit centre or a cost centre depending on your market and logistics. Many equestrian facilities use digestate on their own grazing land; others partner with local farms or sell it as a premium organic fertiliser.

Is Horse Manure Biogas Right for You?

Horse manure biogas is not a turnkey solution for every facility. It works best when:

• You have a reliable, large supply of manure: At least 50–100 horses or equivalent animal count, or access to manure from nearby facilities within a short transport radius.
• You can manage or source compatible bedding: Traditional straw bedding is challenging; alternative or pre-processed materials work better.
• You have access to a market for the energy produced: Either on-site use (heating, electricity for farm operations) or a grid connection and power purchase agreement.
• You or your team are willing to commit to daily monitoring and maintenance: Biogas plants are biological systems; they require attention. Operators must be trained and engaged.
• Your facility has adequate capital and access to technical support: Initial setup costs are significant. Ongoing operational and engineering support is valuable, especially in the first 1–2 years.

If these conditions are met, a well-designed and properly managed horse manure biogas plant can generate reliable renewable energy, reduce greenhouse gas emissions, produce high-quality fertiliser, and create a tangible circular economy benefit for your operation.

Resources and Further Support

Running a biogas plant efficiently requires access to good information and, often, expert support. Consider:

• Joining biogas operator networks or forums where you can learn from peers and troubleshoot issues.
• Keeping a detailed daily operations log using a structured checklist or digital platform. This is essential for optimisation and regulatory compliance.
• Scheduling periodic reviews with a biogas systems engineer to audit your operation, identify efficiency improvements, and plan maintenance.
• Staying informed on regulatory changes related to anaerobic digestion, environmental permits, and renewable energy incentives in your region.

Managing a biogas plant is a specialised skill. The better your operational foundation, the more reliably your plant will convert manure into energy and the greater your return on investment.

Frequently Asked Questions

How much biogas can one horse’s manure produce per day?

A single horse’s daily manure output (25 kg, plus 4–7 kg of bedding) contains enough energy equivalent to roughly 3 litres of fuel oil or 30 kWh in ideal conditions. However, actual gas production depends on digester efficiency, feedstock quality, temperature stability, and whether bedding is pre-processed or blended with other substrates. Most small-scale operations produce 20–40 kWh per horse per day.

What is the difference between mesophilic and thermophilic digestion?

Mesophilic digestion operates at 37–41°C and requires less energy to maintain, making it more common for small and medium plants. Thermophilic digestion (50–55°C) produces somewhat more biogas but consumes more heating energy. For most equestrian facilities, mesophilic systems are more economical.

Can I use traditional straw bedding in a biogas digester?

Traditional straw bedding contains lignin and cellulose, which are difficult to digest. Many operators switch to alternative beddings or pre-process straw by grinding or shredding it. Alternatively, blending horse manure with easier-to-digest feedstocks (such as cattle manure or food waste) improves overall gas yield. Direct use of untreated straw bedding often leads to operational problems and reduced efficiency.

What is digestate and how can I use it?

Digestate is the solid and liquid residue remaining after biogas production. It contains nitrogen, phosphorus, and potassium in plant-available forms and has far less odour than raw manure. Many operators use digestate as an organic fertiliser on their own grazing land or sell it to neighbouring farms. It can be dried (using waste heat from the CHP engine) and sold as pelleted fertiliser, adding a revenue stream.

Do I need special training to operate a biogas plant?

Yes. Biogas plants involve engineering, microbiology, and safety systems. Operators should receive formal training on digestion processes, emergency procedures, gas safety, and equipment maintenance. Many biogas technology suppliers provide training; others recommend working with experienced operators initially to develop competence. Ongoing training and knowledge-sharing with other operators is valuable.

What is the typical lifespan of a biogas digester?

Well-maintained digesters can operate for 20–30 years. The key is consistent monitoring, preventive maintenance, and timely repairs. Internal components (mixers, heating systems, pumps) typically require replacement or refurbishment every 5–10 years depending on use and maintenance practices.

Can a biogas plant be profitable?

Yes, but it depends on several factors: the scale of manure supply, blended feedstock strategy, access to end-use markets (electricity grid connection, on-site heat use, or wholesale energy sales), regulatory incentives (renewable energy grants or feed-in tariffs), and operational efficiency. Facilities with 100+ horses or access to co-substrates are more likely to achieve profitability than very small operations. Expect a 7–12 year payback period for a well-planned operation in a supportive regulatory environment.