Energy demand analysis as a sustainability indicator in dairy production

The View from Teagasc: Energy consumption in milk production is important because it impacts directly on profitability and environmental footprint. In order to reduce energy consumption we must first understand how, and where, it is consumed.

Efficient use of energy is one way to improve the cost competitiveness of the Irish dairy sector.
The aim of this study was to measure baseline data on total energy inputs, as an indicator of the sustainability of the dairy production sector. 
Indicators based on energy consumption, together with other indicators for land and biodiversity, water use, social effects and financial performance are valuable as tools to assess overall sustainability of agricultural activities and to ensure the continued competitiveness of our food products.

Farm description and data collection

To calculate these energy indicators, data on farm production, direct farm energy use (ie, fuel and electricity) and indirect inputs (ie, fertilisers, purchased feed and chemicals) were collected from 22 commercial dairy farms for 12 months. 

The energy use of each input was calculated using energy co-efficients. The energy conversion factors for chemical fertilisers, herbicides, and ingredients of purchased concentrates were based on the international Life Cycle Assessment (LCA) database , and used to convert all inputs to the common unit of energy, the mega-joule (MJ).

Further data, in terms of scale and production, of the farms in this study are presented in Table 1. It is evident that the farms in this study had a much higher milk output than the national average farm and, therefore, were not representative for Irish dairy farms in 2011. The farms in this study represent the larger than average modern dairy farm, with a higher stocking density per ha (ie, more intensive).
However, milk output, and hence herd size, will increase in future if farmers respond to the potential for expansion in milk production identified in the Food Harvest 2020 report. Results of this study, and hence the conclusions drawn, therefore are relevant for larger and more intensive dairy farms.

Farm description and data collection
To calculate these energy indicators, data on farm production, direct farm energy use (ie, fuel and electricity) and indirect inputs (i.e., fertilisers, purchased feed and chemicals) were collected from 22 commercial dairy farms for 12 months. 

The energy use of each input was calculated using energy coefficients. The energy conversion factors for chemical fertilisers, herbicides, and ingredients of purchased concentrates were based on the international Life Cycle Assessment (LCA) database , and used to convert all inputs to the common unit of energy, the mega-joule (MJ).

Further data, in terms of scale and production, of the farms in this study are presented in Table 1. It is evident that the farms in this study had a much higher milk output than the national average farm and, therefore, were not representative for Irish dairy farms in 2011. The farms in this study represent the larger than average modern dairy farm, with a higher stocking density per ha (ie, more intensive).
However, milk output, and hence herd size, will increase in future if farmers respond to the potential for expansion in milk production identified in the Food Harvest 2020 report. Results of this study, and hence the conclusions drawn, therefore are relevant for larger and more intensive dairy farms.

Energy use is quantified for all processes involved up to the moment that milk leaves the farm gate, including production and transport of concentrates, roughage, seeds, herbicides and chemical fertiliser. Such a cradle-to-farm gate LCA, therefore, resembles quantification of the direct (ie, energy use on-farm) and indirect energy use (ie, energy needed to produce farm inputs) of milk production.

Besides milk, our production system also yields meat from culled cows and calves. In such a multiple-output situation, the energy use of the system has to be allocated to these various outputs. We used economic allocation implying that the energy use was allocated to the various outputs based on their relative economic value (ie, 88.3 per cent to milk).

Energy demand to produce a litre of milk

Total energy use averaged 2.5 MJ/L of milk produced, ranging from 1.25 to 3.90 MJ/L, of which 20 per cent was direct and 80 per cent was indirect energy. Figure 1 shows the relative share of total energy use by the major energy consuming farm inputs. About 57 per cent of this energy use was accounted for by the application of chemical fertilisers (range 40-80 per cent). Other significant energy consuming processes included production and transport of purchased concentrate feed 21 per cent (range eight-36 per cent), electricity 12 per cent (range 8-21 per cent), and liquid fuels such as diesel, petrol and kerosene eight per cent (range 1-15 per cent). Other items such as seeds and herbicides represented a small portion of total energy use two per cent (range 0-15 per cent).

Of particular interest were findings in relation to energy consumption in the following categories:
• fertiliser: there were large differences in the chemical fertiliser application rates in this study. Mean energy input by chemical fertiliser was 1.14 MJ/L (range 0.87-2.44 MJ/L). The main fertiliser applied was chemical fertiliser nitrogen.
• feed: The average farm fed 542 kg of feed per milking cow per annum, which equated to 0.5 MJ/L of milk produced.
• electricity: consumption was centred around milk harvesting operations, with 80 per cent of electricity being consumed in the milking parlour and the remaining 20 per cent being used by water pumps and the winter housing facilities. Electricity consumption amounted to 0.31 MJ/L.
• fuel: this accounted for 66 per cent of total fuel energy input and amounted to 0.2 MJ/L. These inputs were specifically: diesel (97.5 per cent of on-farm fuel use), gear oil and transmission oil (1.3 per cent) and kerosene (1.2 per cent). Fuel used by contractors accounted for 31.7 per cent of fuel use and transport of feed, fertilisers and forage to the farm accounted for just 2.3 per cent of fuel use.

Opportunities for improvements and future work
The most significant areas for improving overall energy efficiency on Irish dairy farms are:
• sensible fertiliser management, particularly in relation to the use of chemical fertiliser nitrogen, to reduce indirect energy requirements for fertiliser manufacture;
• careful use of supplementary concentrate feed, to reduce indirect
energy use embodied in the feed;
• improving the efficiency of electricity consumption through adoption of energy efficient working practices and technologies; and,
• optimising fuel use by careful selection of tractors and other farm vehicles to reduce direct use of diesel.

Monitoring of energy indicators should continue in the dairy production sector to build up a picture of trends over time. The majority of the necessary information on the direct and indirect inputs collected in this study are already collected in existing farm analysis tools, albeit in financial terms.

It would be possible to convert these into energy terms, although some accuracy may be lost. Reporting energy indicators in conjunction with the usual production indicators would give useful information relating to the direction of the industry towards a sustainable path.
We acknowledge INTERREG IVB North-West Europe for financial support through the ‘Dairyman’ project: www.interregdairyman.eu/

By John Upton,Research Officer, Livestock Systems Research, Department, Animal and  Grassland Research and Innovation Centre, Moorepark, Fermoy, Co Cork
This feature first appeared in Teagasc’s TResearch publication, which is available here.

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