The dairy industry faces the same basic issues as urban manufacturers: transforming raw materials into quality products quickly, with respect for the environment and cost-effectively. The answers to those challenges are similar too, usually combining investment with innovation, underpinned by solid business sense.

The Dairygold Co-operative Society, Ireland’s largest farmer owned food company, found just such a solution for its energy requirements at Mitchelstown, set in the foothills of the Galtee mountains, County Cork. The Dairygold operations in Mitchelstown produce more than 100 tonnes a day of natural, processed and cream cheese.

While cheese is a natural end-product, its manufacture has moved on considerably since the first cheese production plant in Ireland was founded in Mitchelstown in 1932. Energy is required for the pasteurising, milk separation, heating, chilling and mechanised production which has made the plant one of the most modern in Europe. That requirement has continued to grow as Dairygold looks to maximise the value of its milk by focusing on energy-intensive higher revenue-earning products, such as cheese and spreads, and launch new products, many of them aimed at the increasingly health-conscious consumer.

CHP solution
The need for efficiency and cost-effectiveness is met by an innovative energy system that has proven itself in Mitchelstown. The Combined Heat and Power (CHP) plant produces 10 megawatts of electricity and 50 tonnes of process steam per hour for all the Dairygold manufacturing plants in the town. The dairy industry is in some ways an ideal fit for CHP. It has a high electricity requirement and also a significant demand for steam for the heating and cooling processes that go into the high-value dairy products.

As a result, Dairygold only has to import one to two megawatts of power from the national grid during the peak production months of March to September. In winter, when demand at the plants is lower as milk production falls, it can export around five megawatts to the grid, providing an important additional revenue source. At Mitchelstown, additional gas firing is given to the exhaust gases to raise their temperature from 520OC to 800OC, thereby increasing the steam output from the boilers to meet the peak demand.

CHP is a simple way to dramatically improve the energy efficiency of a power plant. In a conventional plant, a turbine will transform gas fuel input into electrical output. A CHP plant will do that, but will also capture the heat from waste gases to produce steam. That steam can then be used for a variety of purposes, from hot water for heating, to energy for mechanical processes in a factory. The end result is more useful output from the same amount of raw fuel.

Dairygold took another step to further increase the effectiveness of CHP. It selected energy management specialists Fingleton White & Co as a partner in a joint venture set up to operate the Mitchelstown power plant, just as it had at Mallow. That decision brought outside expertise into the plant’s operations and allowed Dairygold to concentrate on its core business of food production.

Fingleton White & Co selected 501 gas turbines, produced by Rolls-Royce in Indianapolis, US and packaged by Centrax in the UK, for both the Mallow and Mitchelstown projects. The aero-derivative nature of the 501 gives Fingleton White & Co better performance flexibility and fewer servicing issues.

That gas turbine was commissioned into service in November 1999, and meeting that deadline allowed Dairygold to save IR£75,000 by avoiding higher winter tariff charges from the grid.

To ensure it met Dairygold’s requirements, Fingleton White & Co signed a maintenance contract with Centrax, covering the Mallow and Mitchelstown 501s.

The Mitchelstown plant is now officially recognised as a good practice case study. That recognition came from the Irish Energy Centre, the national agency for energy efficiency and renewable energy information, set up by the Government’s Department of Public Enterprise. As more Irish businesses consider how to maximise energy efficiency and minimise cost, Dairygold’s experience with CHP is cited as an example of how innovation can result in savings.