New Landia Digester Mixing System for Farm-Based Biogas Plant in Japan

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At a farm-based biogas plant in a remote area of Hokkaido, the northernmost of Japan’s main islands, a Landia GasMix system has replaced mixers that were struggling to cope with manure and agricultural feedstock.

The new digester mixing system is designed to provide reliable and efficient mixing while addressing some of the challenges associated with high-solids agricultural waste. By using externally-mounted equipment, the Landia GasMix system also removes the need to enter the digester or drain the tank for routine servicing and maintenance.

The installation is helping the farm maintain a healthy anaerobic digestion process while providing a dependable way of handling the grit, straw and solids typically found in agricultural feedstock.

Reliable mixing for agricultural biogas feedstock

The original mixers at the Japanese biogas plant had become increasingly problematic due to the inevitable high levels of solids present in farm waste.

Frustrated by the problems caused by the original mixing equipment, the farmer switched to Landia’s externally-mounted GasMix system. The technology uses a Landia Chopper Pump, which was invented by Landia in 1950, to continuously break down heavy particles within the digester feedstock.

Handling solids effectively is an important consideration for agricultural anaerobic digestion plants. Manure and other farm-based feedstocks can contain significant quantities of grit, straw and other fibrous or heavy material which can create challenges for conventional mixing equipment.

The Landia GasMix system is designed specifically to address these conditions by combining pumping, particle breakdown and recirculation to create effective mixing throughout the digester.

External digester mixing simplifies maintenance

Another major problem with the previous mixers was the difficulty involved in retrieving them for maintenance or repair.

Because the mixers were installed inside the digester, accessing them required the farmer to drain down the digester. This was both costly and labour-intensive and could also result in significant disruption to the operation of the biogas plant.

The Landia GasMix system takes a different approach.

The system uses externally-mounted equipment, meaning there are no moving or wearing parts inside the digester. As a result, servicing can be carried out from outside the tank without the need to drain the digester.

This design can provide a significant practical advantage for farm-based anaerobic digestion plants where maintaining continuous operation is important.

gasmix reliability — The proven reliability of GasMix was a key factor in the decision of the Japanese biogas operator in a remote location to choose Landia.

Chopper Pumps and venturi nozzles deliver continuous mixing

The system installed at the Hokkaido biogas plant utilises two 18.5kW floor-mounted Landia Chopper Pumps together with venturi nozzles.

Despite the pumps’ relatively straightforward operating cycle, they provide the required mixing performance while only needing to run for 15 minutes per hour.

The Chopper Pumps recirculate digester sludge through the system where the venturi nozzles inject the sludge back into the digester.

This recirculation process homogenises the digester sludge and provides comprehensive vertical and horizontal mixing. By injecting the sludge back into the digester, the system increases the active surface area available for anaerobic bacteria.

Effective mixing is an important part of anaerobic digestion because it helps maintain a more uniform environment within the digester. It can also help ensure that feedstock and microorganisms remain in contact while supporting the overall digestion process.

No internal moving parts

One of the key features of the Landia GasMix installation is that there are no moving or wearing parts inside the digester.

This is particularly relevant for agricultural biogas plants where the feedstock can contain abrasive and fibrous materials. Grit, straw and other solids can place considerable demands on equipment operating within the digester.

By positioning the pumps and associated equipment externally, the GasMix system keeps the mechanical components outside the tank. This allows servicing and maintenance to be carried out without draining the digester and without the associated downtime.

For a remote farm-based biogas plant such as the installation in Hokkaido, reducing the complexity and disruption associated with maintenance can be particularly valuable.

‘In a remote, rural area, reliable equipment is essential’

“In such a remote, rural area,” said Fergus Clark from Landia (Asia/Pacific), “reliable equipment is essential. Many mixers are just fine in other, gentler applications, but at a biogas plant, unless they are designed for purpose, cannot deal properly with the grit, straw and solids that you always have to contend with in an agricultural feedstock.”

The comments highlight one of the key challenges faced by agricultural anaerobic digestion operators. While conventional mixing technology can be suitable for less demanding applications, agricultural feedstocks can require equipment specifically designed to handle high levels of solids and fibrous material.

For the Hokkaido installation, the GasMix system provides an alternative to submersible or internally-mounted mixing equipment by keeping the pumping and mechanical components outside the digester.

landia gasmix system — Landia’s externally-mounted GasMix system

‘Can utilise excess heat’

Clark added: “Now, with an efficient and highly dependable mixing system, the farmer has a perfectly healthy biogas plant that can utilise the much-needed excess heat for his cow sheds in Hokkaido’s very cold winters – and sell excess renewable energy to the grid.”

The ability to make productive use of the biogas generated by the plant is particularly relevant in Hokkaido, where winter temperatures can be extremely low.

The farmer can use excess heat from the biogas plant for the cow sheds during the cold winter months while also selling surplus renewable energy to the electricity grid.

The combination of reliable digester mixing, improved maintenance access and the ability to utilise both heat and renewable electricity demonstrates the wider role that efficient anaerobic digestion equipment can play on agricultural sites.

For farm-based biogas plants, maintaining consistent digester performance is essential to making the most of available feedstock. Equipment that can reliably handle solids while reducing maintenance requirements can help operators keep their plants running efficiently.

The Landia GasMix installation in Hokkaido therefore provides a practical example of how externally-mounted digester mixing technology can address the challenges associated with agricultural feedstocks while supporting reliable anaerobic digestion and renewable energy production.

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Landia's headquarters are located in Lem, which is how it has been since 1933. Today, Landia has subsidiaries in England, Germany, Norway and the US, and a sales office in China. In addition, Landia products are sold in 45 countries worldwide. Landia supplies pumping and mixing solutions to many different industries, with the most important ones being agriculture, wastewater, biogas plants and the fish industry. In general, you will find Landia's products wherever there is a difficult medium to be pumped or mixed. Landia survives by selling quality solutions in close partnership with the customers.

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