Energy is a resource that must be used efficiently and effectively. It makes no sense to waste it. Fuel costs (heating oil) have risen by 77 per cent since 2009, and there is concern that they will become an even more significant cost in the future. Typically a 1,000-sow integrated pig unit (i.e. rearing pigs from birth to slaughter) will spend €80,000 each year on fuel and electricity for the production of pigs.

As you read, this paper ask yourself the following questions:

1. Have you had an energy audit done for your farm?
2. How closely is energy use monitored on your farm?

What is the Energy Usage on Pig Farms?

In 2006, a Teagasc survey of eight Irish Pig Farms with a total of 4,701 sows (approximately three per cent of the national pig herd) showed an average usage of 27kWh per pig produced (with a range of 17 to 37kWh per pig produced; Clarke, 2006).

More recent audits done on 23 pig farms show a huge variation in the energy usage ranging from 18 up to 45kWh per pig produced with an average figure of 28kWh per pig produced. These audits for 23 farms included over 20,000 sows. The high variation from one farm to another suggests that a greater emphasis needs to be put on energy efficiency.

Another source of data available is from 83 pig farms recording on the Teagasc Pigsys records (2011). The energy cost (heat, power and light) is €3.39 per pig produced (or €81 per sow per year based upon 24 pigs produced per dow and year). This Pigsys data covers approximately 38 per cent of the national pig herd.

Energy on pig farms is mainly used for:

• heating the farrowing and first stage weaner houses,
• ventilation systems and fans,
• lighting throughout the buildings,
• feed delivery and mixing, power-washing, and
• manure pumps to mix and agitate slurry tanks.

This paper discusses the first three items in greater detail.

1. Heating the Farrowing and First Stage Weaner houses

Heat must be provided to the younger pigs on a pig unit. The temperature in the farrowing rooms is critical for the survival of newly born piglets. The ideal is to have a farrowing room temperature of 24°C once the first piglet is born in the room. This should be reduced to no more than 20°C when the youngest piglet in the room is over two days old.

Pig producers may use paper to supplement the heat source at farrowing rather than an infra-red bulb. If the average gestation period is 115 days, it is not necessary to heat up the creep area on day 113 of gestation. Poor temperature control can lead to unnecessary overheating of pads resulting in wasted heat production and wasted ventilation energy. This applies particularly in the first two weeks after farrowing.

First stage weaners (i.e. 7kg to 17kg liveweight approximately) also require a source of heat. The aim is to have newly weaned pigs kept at 28°C to 29°C initially, with a reduction of approximately 2°C in room temperature each week thereafter.

It is critical to check if the ventilation system is working in tandem with the heating system. The ventilation system may control house temperature at a massive cost to the heat supply system if the two systems are not working in tandem with each other. A lag time may occur before the temperature sensor shuts off the 'call' for heat. This problem can be compounded by the fan cutting in to remove the excess heat provided. Air quality will be fine but at a cost to energy usage.

Is there a potential to make cost effective improvements to reduce heat input? There may be scope to do so if weaning weights have increased. An extra one kilo body weight at weaning can reduce energy requirement by eight per cent in this stage of growth. So weaning heavier pigs will reduce the energy requirement.

Insulation of pig buildings

The provision of heat in buildings is very wasteful if there is a poor level of insulation in the building. The walls and ceilings should be insulated to achieve suitable U values. Check the insulation to see if it has been damaged by pests. The temperature fluctuation in the pig house should also be checked by using maximum-minimum thermometers to monitor if house temperatures vary considerably between day and night-time.

Heat pumps

A number of units have installed heat to air pumps to heat the heat pads in the farrowing units. These systems extract the heat from ambient air and use it to heat water via heat exchange systems. This can be ideal to heat water to temperatures of 55°C.

The capital costs of these systems can be high but they are effective in reducing fuel costs. A hybrid system also exists where the heat pumps operate to certain parameters but if the ambient temperature drops too low a boiler backup steps in to provide the heat supply. This system links to computerised controls which can adjust to changing costs of electricity prices, fuel costs etc as programmed.

2. Ventilation Systems and Fans

Pig houses are ventilated to control the levels of gas (i.e. carbon dioxide, ammonia, methane and hydrogen sulphide are the main ones) and airborne pathogens in the pigs environment. This is done to achieve good growth performance in terms of growth rates and feed conversion efficiencies.

Some pig houses are controlled without the use of mechanical fans to pull fresh air through the house. This system relies on the 'stack' effect which relies on warm air rising and being replaced by cooler fresh air from outside the building and is referred to as natural ventilation.

The only energy used in this system is to control the air inlet and outlets in the building. This system has very low running costs but may be a difficult system to manage particularly in very changeable weather or on very exposed sites.

Ventilation and feeding systems are the main users of energy in the weaner and finisher section of a pig farm. If the ventilation system chosen is Automatically Controlled Natural Ventilation (ACNV) and the feeding system is a liquid one the power usage is greater for the feeding system. Where the ventilation system is fan powered with restricted inlets and the feeding system is an augered wet/dry system, the consumption pattern may be reversed.

Mechanical ventilation relies on fans, air inlets and controllers to manage the volume of air to be moved through a house. This system has higher running costs because of the use of fans.

Fans

Fans are 'ever-ready' to consume electricity, sometimes with no advantage to improving the pig environment. How often do you see fans at full speed in a dry sow house in mid winter, or first stage weaner houses with fans at full speed and heaters glowing? Remember that when fans are set, either manually or on a curve, they will carry out that function, be it correct or incorrect until the settings are changed.

When assessing or choosing a fan the following should be checked at a minimum:

• Fan size must be matched to the stock type (i.e. weaners, finishers etc.) and numbers to be accommodated in the pig house to be ventilated – will the fans move adequate air to keep the air in the pig house fresh?
• Inlet size versus fan capacity – is there a risk of over-ventilating the room thereby chilling pigs and wasting energy?
• Fan efficiency: How much air is moved by the fan versus the power required by the fan? You need to check the data sheet provided by the manufacturer to get this information.
• The 'back pressure' is the resistance to air flow at the fan outlet. This needs to be factored into the equation also to determine fan efficiency. This efficiency may vary with different fan sizes and models supplied by different manufacturers.

Natural power ventilation

This is a new system which is designed to work as a naturally ventilated house when possible. It could be described as an adaptation of the natural system with the ability to mechanically ventilate when necessary. Extra air outlets are installed to allow the natural ventilation system operate. When there is a need for additional ventilation, the fans begin to operate.

This system may have a higher initial capital cost but is achieving a reduction in electricity usage for ventilation of approximately 80 per cent for finishing houses where this was monitored on 3 farms and compared with similar mechanically ventilated houses. This system did not compare pig performance in the houses and it is assumed that the pigs achieved similar growth performance in each housing system.

3. Lighting

A typical 500-sow integrated pig farm has 5,000 square metres of floor area to illuminate, approximately 10 square metres per sow and progeny. Lighting power consumption accounts for 10 to 15 per cent of electricity supplied onto the farm, (i.e. 2 to 4kWh per pig produced).

The relevant regulations (S.I. 311 of 2010) specify a minimum of 40 lux light intensity for a continuous period of at least eight hours (in any 24-hour period) for pigs.

A recommended light intensity of 100 lux for inspection of animals is reasonable. For dry sows and farrowing house 200 lux is recommended. Service houses should have light intensities of 300 lux for 14 to 16 hours each day to overcome seasonality effect of changing day-lengths.

The standard incandescent (Tungsten) bulb is five per cent efficient at converting energy to light and has an expected life of 1,000 hours versus a fluorescent at 7,000 to 16,000 hours. The compact fluorescents have been heavily promoted in recent years. They provide good energy efficiency and are easily fitted into the incandescent bulb holder.

Table 3 shows the 'lumen efficacy' of different light sources. The higher the lumen efficacy the more efficient the source is at producing light.

For efficiency, choose the T-5 (16mm) tube instead of the T-8 (25mm). Electronic control will further reduce energy usage by 20 per cent and extend lamp life by 50 per cent. These units are four times as efficient as regular incandescents and last 16 times longer.

The LED (light emitting diodes) is the latest technology in lighting. The light fittings are more expensive to install but last much longer and are more efficient from an energy use perspective. They do not heat and use less energy as a result. They are well worth considering in new buildings because of their lower energy requirements – particularly in loose sow houses.

Conclusions

Energy is a cost that is increasing on pig farms. Do you know how your unit compares with other pig farms in terms kWh per pig produced? Are there savings to be made by investing in new technologies on your farm?

Notes:

1. A conversion factor of 10.5kWh was used per litre of kerosene to calculate energy usage.

References

Clarke, S. 2006. Economising on electricity usage on the pig farm. Teagasc Pig Farmers Conference 2006.

S.I. 311 of 2010 - European Communities Welfare of Farmed Animals Regulations.

Further Reading You can view other papers presented at the conference by clicking here.

January 2013