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Published online by Cambridge University Press: 02 September 2010
Conventionally heat consumption forms a small proportion (about 002) of the total cost of producing finishing pigs. Heating costs are incurred from farrowing to about 20 kg live weight and generally represent about 0–05 of production costs to this stage.
Apart from the incorporation of adequate insulation in the building structure, the main means of restricting heating costs is by good control of minimum ventilation rate. Efficient control systems are available but operators do not always fully understand how they are intended to work, so effective training is as important as clear operating instructions.
Techniques exist for the reduction of fossil fuel consumption but all involve the expenditure of additional capital and have running costs of their own. In relation to the current low costs of fossil fuels, oil and propane, even the simplest of these methods are difficult to justify in commercial practice. They include: heat recovery by static recuperator from ventilation exhaust air; and heat recovery by heat pump from low temperature sources such as aerobically treated slurry, ground water and exhaust air.
Alternative non-fossil fuels include biogas and straw. Biogas production by anaerobic digestion of slurry is expensive in capital and is only feasible where the slurry must be treated for other reasons, such as odour control. Heat production from straw may be economical where the straw is available at low cost and simple stoking aids (e.g. existing tractor fore-loaders) are used.
Fail-safe equipment to protect stock in the event of forced ventilation system breakdown must be carefully designed and installed to be reliable. Methods are available to suit the range of ventilation and housing systems. Failure of natural ventilation systems is less likely to cause problems, and indications to the stockman of abnormal temperature conditions should be sufficient to prevent loss of stock.