Renewable energy solution optimises farm resources
Aims: Hybrid renewable provide Dried Manure Solids as Bedding for Dairy Cows
Customer: Dairy farm with a herd of 760 cattle
The aim of the project was to deliver an efficient, renewable energy solution for the generation of green bedding. A combination of three ground source heat pumps and two biomass boilers were installed to produce heat to a drying floor where recycled manure solids were dried to generate bedding material. These were linked in with the existing wind turbine, enabling the most efficient use of energy based on wind conditions and heating requirements.
Benefits / Business Case
- The project fully utilised the renewable energy available through the wind turbine and water wells on the farm. In addition, Biomass boilers are fuelled with sustainable wood chip.
- The installation of the drying floor enables the generation of 1300 tonnes of green bedding per year. This provides savings on traditional sawdust and stream products of £50,000/yr
- The drying floor will also be utilised to dry grain and can provide an additional revenue string if used to dry 3rd party crops.
- Utilising the Renewable Heat Incentive scheme enabled the project to be financed, with full return on investment in less than 7 years
- Private cable from Wind Turbine resulted in a 50% reduction in farm power costs
Purpose of Project / Business Challenge:
In Britain, virtually all dairy cows are housed at some stage during the year, not least to provide protection from inclement weather over the winter months. While the animals are housed, the use of safe, comfortable, dry bedding is an important consideration for good health and welfare. Materials used typically include, straw (whole or chopped), synthetic cubicle mattresses, sand, sawdust, wood shavings, and a variety of proprietary products. Increased costs and reduced availability of bedding sources has prompted many dairy farmers to search for more accessible, cost effective and sustainable alternatives.
Using separation technology, to produce recycled manure solids (RMS) for bedding, commonly referred to as ‘Green Bedding’, has been increasing in many countries around the world. For example, this has become common practice in many US herds, and is also being used in several European countries.
The advantages include increased cow comfort relative to other bedding materials, reduced cost and increased environmental sustainability.
For this project, the biomass boilers (producing up to 1MWth) and ground source heat pumps (300kWth) supplied heat to a closed water system which pumped water through two radiators. The hot air produced is then channelled through to the drying floor.
Utilising the farms wind turbine provided the most cost effective solution for power to the heat pumps. For every kilowatt of electric used from the wind turbine, 4 kilowatts of heat are generated by the heat pumps. Managing the system was key, so on windless days where the turbine wasn’t operational the more expensive power from the grid could be minimised, instead using just the biomass boilers. When wind is available, increased heat generation from the GSHP reduced requirement of boilers and therefore wood chip consumption.
The water supply for the heat pumps was via an ‘Open loop system’, pumping water out of 3 wells on the farm, through the heat pumps, and then re-injecting this water down two further wells back into the ground water system.