Lodge Farm, Wrexham 160kW Plant
Lodge Farm Anaerobic Digester
This is our own on-site AD system, which was developed by Fre-energy from the ground up and continues to be the platform for on-going testing and development.
Our impetus for researching and developing a new kind of AD system
After a trip to look at AD systems in Germany, it was decided that we wanted a waste digester that would process on-farm inputs and complement the core business of organic milk production, rather than growing crops to feed a large crop digester and essentially turning the farm into a rural power station.
Setting up the business
The business was set up by the three directors: Chris Morris, who had the time and experience to deal with the business set-up process; Jonathon Tomlinson, who had the engineering capability to build a digester; Richard Tomlinson having a dairy herd and land in order to feed the digester and utilise the by-product (digestate).
The Project
To ensure that the slurry was delivered to the digester as fresh as possible, a separate lagoon was constructed within the larger storage lagoon at the farm in order to store the slurry and pump it underground to the digester half a mile away on a fortnightly basis. This provided a clean and convenient solution as an alternative to transporting the slurry either across the land or by road.
The project was directly funded by the three Directors plus a £45K innovation grant from the Welsh Assembly Governrment.
Requirements for Operating and Maintaining the Installation
Day to Day Resources
Requires about 2 hours daily spent loading the feedstock into the digester and simple maintenance of pumps and mixers etc. Current inputs are 30 tonnes of cow slurry plus 6 tonnes of chicken litter from a local broiler unit.
Outputs
Energy Production
The outputs are 160kW of electricity and 200kW heat.
- Approx 30kW electricity is used on site to power the engineering business, the Fre-energy office, and a large 7 bedroom farmhouse.
- Approx 60kW of heat is used to heat the cow slurry and chicken litter in the digester up to 40°C and the rest is used to heat the house and office.
- The surplus of the electricity is exported to the National Grid
Digestate Usage
All the digestate goes through a separator. The liquid is stored in a lagoon that has 6 month storage capacity and from there it is spread onto the grassland using either umbilical cord through a spike aerator followed by a low level trailing shoe or by a 3000 gallon low ground pressure Vaccy tank with the same system attached.
The solid digestate, which contains a higher proportion of the phosphate and potash, is transported by road to land used for growing winter crops to feed the dairy herd. Several allotment owners in the local village have used this product and have been so impressed that we could market it for a substantial sum.
Trial work done by Bangor University has demonstrated that the BOD [biological oxygen demand] of both these products is reduced by up to 90%. This represents a substantial environmental benefit.
Environmental Advantages of the Fre-energy Closed Loop System
A waste digester that utilises farm derived inputs and then returns those inputs back to the land in the form of digestate is a closed loop system. Lodge Farm does not import any artificial fertiliser to grow grass or crops; it is completely served from the outputs of the AD. Another benefit is that any weed seeds that enter the digester are no longer viable when returned back to the land. The other social benefit is that digestate has ~80% less odour than straight cow slurry, thus making the spreading of manures far more socially acceptable.