Farm Ireland

Monday 22 January 2018

Robotic milking machine's running costs will fall

John Upton

During 2011 and 2012, the total energy use of the AMS was 106 Watt-hours per litre of milk produced (Wh/l) during its first lactation (range 69-178 Wh/l), and 84Wh/l in its second lactation (range 53-113 Wh/l).

Table 1 (right) gives more information on the performance of the milking systems over two years.

Water heating accounted for the largest portion of energy use (39pc and 30pc in 2011 and 2012, respectively).

The energy consumption of the milk cooling system, air compressor, vacuum pump and robot in 2011 and 2012 are presented in Table 2.

Miscellaneous items such as wash pumps and an office consumed 16Wh/l and 13Wh/l in 2011 and 2012, respectively.

When the relevant tariffs were applied, the average cost of electricity was 1.36 cents per litre of milk (c/l) in 2011 (range 0.84-2.42c/l) and 1.09c/l in 2012 (range 0.68- 1.58c/l).

The average AMS running costs of 1.36c/l (2011) and 1.09c/l (2012) were high compared to an audit of conventional milking systems (0.43c/l) on 21 commercial dairy farms (May-October 2010) by Teagasc, Moorepark.

This may be due to either reduced milk output from the AMS during the start-up years (when milk yield is expected to be reduced by 10-15pc) and/or under-utilisation of the AMS.

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Some 63 and 72 cows were milked in this grazing-based study in the first two years of operation, but it would be possible to increase the number of cows milked by the AMS.


In the period immediately after installation, the AMS underwent a hot wash process three times per day, by default. This requirement is a consistent fixed cost, irrespective of the volume of milk produced because wash cycle scheduling is time-based.

Reducing hot water wash cycles from three times daily to twice per day in 2012 reduced energy consumption by the water heating system by 38pc (from 41Wh/l to 25Wh/l).

The average TBC results were 18,000 cells/ml across the 2011 and 2012 milking seasons.

A further important energy saving initiative was the installation of a variable speed drive (VSD) vacuum pump.

The VSD is able to adjust the rate of air removal from the milking system by changing the speed of the vacuum pump motor to equal the rate at which air is admitted to the system at a given vacuum level.

All of the energy used to move air through the conventional vacuum regulator is saved.

Changing from a standard vacuum regulator-controlled vacuum pump system to a VSD vacuum pump in week six of the 2011 season reduced vacuum pump energy use by 63pc (from 19Wh/l to 7 Wh/l).


The largest energy consuming processes associated with the AMS were heating water, compressing air and cooling milk.

However, it is likely that the energy use of the AMS will reduce further as cows become familiar with the AMS and optimum herd size/milk output for the AMS is reached.

In 2013, the effect of using a heat recovery system to recover waste energy from the milk cooling system, cold detergent wash cycles instead of hot washes and a solar thermal water heating system to reduce its running costs will be investigated.

Irish Independent