Your questions about micro-AD

Micro-AD systems are small-scale biogas plants designed to run primarily on slurry from livestock. The system captures methane produced during slurry storage and converts it into renewable electricity and heat using a combined heat and power (CHP) engine.

Slurry is pumped from cow housing into a sealed digester tank where bacteria break down the organic matter in an oxygen-free environment. The methane-rich biogas produced is then used to generate electricity and heat.

Once processed, the slurry is returned to the farm’s slurry store as digestate and can be handled and spread in the same way as slurry.

In practice, well-managed Biolectric micro-AD units achieve 90-95% availability, which is much higher than other weather-dependent renewable energy options, such as wind and solar.

One 550-cow dairy in Cumbria installed a 74 kW Biolectric micro-AD system and is now largely self-sufficient in electricity, exporting around 35 kW, with a projected payback of 4.5–5 years.

Micro-AD technology has developed significantly over the past decade, both in terms of system performance and how installations are delivered and supported.

Earlier systems in the market did not always perform as consistently as expected, particularly where designs were still being refined or support structures were less established. Since then, continuous development of the technology, combined with closer collaboration between manufacturers and on-farm teams, has led to major improvements in efficiency, reliability and overall performance.

Today’s Biolectric micro-AD systems benefit from:

• More refined and robust digester and CHP technology

• Improved system design tailored specifically to dairy farms

• Better integration with on-farm slurry handling systems

• Full-service support, including remote monitoring and planned maintenance

For farmers considering micro-AD, this progression is important. It shows how the technology has matured into a practical, proven solution that fits more easily into modern dairy systems while delivering reliable long-term benefits.

Micro-AD technology is already widely used across Europe and has been operating successfully on dairy farms for many years.

Biolectric has installed more than 450 slurry-only anaerobic digestion systems across Europe, with numbers continuing to grow in the UK and Ireland as more farmers look for practical ways to generate renewable energy directly on farm.

The systems are designed specifically for livestock farms and use slurry produced by the herd as the sole feedstock. This makes them different from large, centralised AD plants that often rely on imported feedstocks or dedicated energy crops.

The technology has been successfully adopted across a range of dairy systems, from smaller family farms to larger commercial units.

Interest is continuing to grow as farmers look for ways to improve resilience in the face of volatile energy prices, tighter environmental regulations and increasing pressure from the supply chain to reduce agricultural emissions.

Micro-AD systems work best on dairy farms that produce a consistent supply of slurry and have a steady demand for electricity on site.

Biolectric units are typically suited to farms with around 100 to 900 cows, although the most appropriate system size depends on the herd’s slurry production and the farm’s energy requirements. Systems are designed so that the energy generated closely matches the farm’s own electricity use. 

In practice, the technology tends to work particularly well on farms where:

• Cows are housed for significant parts of the year

• Slurry is collected frequently, allowing fresh material to feed the digester

• The farm has consistent electricity demand

Because the system runs entirely on slurry produced by the herd, it does not require additional feedstocks or crops to operate.

The electricity generated is typically used directly on the farm to power day-to-day operations such as milking robots or parlours, milk cooling, pumps, lighting and other equipment, helping reduce reliance on grid electricity and improve overall energy resilience. Many farms also use the energy to help run diversification projects.

Every farm is different, but micro-AD may be a good fit where there is:

• A consistent slurry supply

• Housed dairy cattle

• Significant on farm electricity demand

• A focus on improving long-term resilience and sustainability

Biolectric works with farmers to assess herd size, slurry production, energy use and site infrastructure to determine whether a system is suitable.

For many farms, micro-AD represents a practical step towards a more circular farming system, making better use of the resources already produced on farm while strengthening long-term business sustainability.

The amount of energy generated by a micro-AD system depends largely on herd size and the volume of slurry available to feed the digester. Systems are typically designed to match the slurry produced by the herd and the farm’s own electricity demand.

Biolectric systems generally produce between 11 kW and 74 kW of electricity, depending on the size of the installation. 

On many dairy farms, this level of output closely matches the farm’s base electricity demand. This helps reduce reliance on electricity purchased from the grid and protect the business from volatile energy prices.

As well as electricity, heat generation is available as part of the energy production process. How much heat that can be generated depends on the farm’s micro-AD setup and demand.

Where applicable, heat from the combined heat and power (CHP) process can be used around the farm, for example for parlour washdowns or to heat nearby buildings and accommodation.

Because the system operates continuously, provided there is a regular supply of slurry, micro-AD can provide reliable, round-the-clock energy generation, unlike some renewable technologies that depend on weather conditions.

Return on investment will vary from farm to farm depending on factors such as electricity prices, herd size, slurry availability and how much energy is used on the farm.

On most farms, systems that are well matched to a farm’s slurry supply and energy demand typically deliver the strongest financial returns.

What we typically see on farm is:

• Typical payback periods are around 4-8 years, with around five years being common.

• When all benefits are considered, Biolectric systems can add up to 5p per litre of milk produced on the farm through a combination of energy savings, improved fertiliser value and reduced emissions from slurry management. 

• The expected lifespan of a micro-AD unit is around 20 years, allowing farms to benefit from long-term energy generation once the initial investment has been recovered. 

Real farm examples demonstrate how these savings can add up in practice. Several UK dairy farms operating Biolectric units report electricity savings of around £2,500–£5,000 per month.

Alongside electricity savings, farms can also see additional financial benefits through reduced reliance on purchased fertiliser thanks to the improved nutrient availability in digestate.

The cost of a Biolectric micro-AD system depends primarily on the size of the unit installed and the farm’s energy demand. Systems are typically sized according to herd numbers, slurry availability and the amount of electricity used on the farm.

Typical installation cost approximately:

• 11 kW unit: around £170,000

• 74 kW unit: around £490,000

Most dairy farms install systems somewhere between these sizes depending on the scale of their operation and how much slurry is available to feed the digester.

The business case for micro-AD is usually based on several combined benefits, including:

• Electricity savings from generating renewable energy directly on farm

• Improved fertiliser value from digestate

• Greater protection from volatile electricity prices

• Reduced emissions from slurry storage

In practice, most farms see payback periods of around four to eight years, with many achieving a return in around five years.

The systems are designed to operate for around 20 years, meaning farms can benefit from predictable, long-term energy production once the initial investment has been repaid.

For many dairy farms, micro-AD becomes part of a wider strategy to improve resilience, helping control input costs, make better use of nutrients already produced on the farm, and strengthen the long-term sustainability of the business.

In most cases, very little needs to change.

Biolectric micro-AD systems are designed to integrate into a farm’s existing slurry infrastructure, so they can be incorporated into the normal flow of slurry handling on a dairy unit.

This means farmers can generally continue:

• Storing slurry in existing stores

• Separating slurry if required

• Spreading digestate using normal slurry equipment

Typically, slurry is pumped from the reception pit or directly from the housing system into the digester. After the digestion process is complete, the material is returned to the farm’s slurry store as digestate. From there, it can be handled, stored and spread in much the same way as slurry.

Because the Biolectric micro-AD system sits between the cow housing and the slurry store, it effectively becomes part of the farm’s normal slurry management process rather than replacing it.

The main requirement is a regular supply of fresh slurry, which helps maintain efficient digestion and consistent energy production. For this reason, micro-AD systems tend to work best on farms where cows are housed for significant periods of the year and slurry is collected frequently.

During the planning stage, Biolectric works with farmers to review the existing slurry system and identify the most practical way to integrate a digester into the farm’s current setup.

The space required for a Biolectric micro-AD system depends on the size of the unit installed, but it typically ranges between 300 m² and 800 m².

Ideally, the plant is located close to the cow housing and existing slurry store to allow slurry to be pumped easily into the digester and returned to storage once processed.

A Biolectric system usually consists of a digester tank where the slurry is processed and a combined heat and power (CHP) container where electricity and heat are generated. Compared with large commercial AD plants, these components are relatively compact and designed specifically to fit within working dairy farm environments.

During the planning stage, Biolectric works with farmers to assess the most suitable location on the farm. Taking into account slurry flow, access for installation and maintenance, and how the plant will fit alongside existing buildings and operations.

One of the advantages of Biolectric micro-AD is the relatively quick installation process.

Once the necessary groundwork and site preparation have been completed, a Biolectric system can typically be installed in around three days.

The digester tank and combined heat and power (CHP) unit are delivered to site and assembled quickly, allowing the system to be integrated into the farm’s existing slurry infrastructure with minimal disruption.

After installation, the plant needs a short commissioning period while the biological digestion process establishes itself and the system is fully calibrated. In many cases, farms begin generating electricity within a few weeks of installation.

Installation can usually be carried out without major changes to the day-to-day running of the farm.

Planning requirements for small-scale, slurry-based AD systems are generally simpler than those for large commercial AD plants.

Biolectric micro-AD systems are designed to operate within the existing infrastructure of a dairy farm and are significantly smaller than large-scale digesters. In many cases there is a dedicated planning pathway for agricultural AD installations, meaning there are often fewer regulatory hurdles compared with large-scale energy projects.

Local authorities are also increasingly supportive of technologies that improve slurry management and reduce methane emissions from agriculture.

Because each site is different, Biolectric works with farmers during the planning stage to assess the local requirements and guide them through the process where necessary.

Biolectric micro-AD systems are designed to integrate into normal farm routines and require minimal daily input from the farmer.

In most cases, operating the system involves around 10 minutes of daily checks to ensure everything is running smoothly. These typically include simple visual inspections and confirming that slurry is flowing correctly through the system.

The Biolectric micro-AD system itself is largely automated and continuously monitored through Biolectric’s remote monitoring system, which allows technicians to track performance and identify any issues early. Many adjustments or checks can be carried out remotely without requiring the farmer to intervene.

On most farms, one or two people are nominated to carry out the quick daily checks rather than involving the entire team.

Digestate is the material that remains after slurry has passed through the anaerobic digestion process.

While it looks and handles very similarly to slurry, the digestion process changes the form of some nutrients, making them more readily available to crops and grass. During anaerobic digestion, organic nitrogen in the slurry is converted into ammonium nitrogen, which plants can absorb more easily.

Farm testing has shown digestate can contain around 75% ammonium nitrogen compared with around 40% in untreated slurry, improving nutrient availability for crops and grass. 

The material is typically returned to the farm’s slurry store after processing and can then be spread using the same equipment and methods as slurry.

For many farmers, this improved nutrient availability means digestate can help reduce reliance on purchased fertiliser, while still supporting crop growth and soil fertility.

In this way, Biolectric micro-AD systems not only generate renewable energy but also help make better use of the nutrients already produced on the farm.

Installing a Biolectric micro-AD system is a long-term investment, so ongoing technical support is an important consideration. Biolectric provides full service support throughout the life of the system, from the initial design and installation through to long-term operation and maintenance.

Once installed, each unit is connected to Biolectric’s remote monitoring system, allowing the technical team to track performance and identify potential issues early.

Routine servicing and maintenance are carried out by Biolectric engineers, while farmers typically only need to carry out basic daily checks, which usually take around 10 minutes per day. 

This approach allows the system to operate largely automatically while ensuring professional support is available whenever it is needed.

Biolectric micro-AD systems are designed to operate reliably with minimal intervention, but if an issue does arise, support is available.

Each system is remotely monitored by Biolectric technicians, allowing many issues to be identified and addressed quickly. In some cases, adjustments can be made remotely without the farmer needing to intervene.

If an on-site visit is required, Biolectric engineers can attend the farm to resolve the issue. The aim is to minimise downtime and ensure the system continues to run efficiently as part of the farm’s daily operations.