Energy use in farm buildings
In Sweden, the agricultural sector uses an estimated 3.7 TWh per year as electricity or fuel. About 34% of this total is estimated to be used in the production of beef, pork, eggs and milk, including the spreading of manure. Some energy is also used for harvesting ley and cereals as feed, which is not included. Most of the energy used is in the form of electricity (approx 63%). All these estimates are based on a 1981-1984 survey by Nilsson & Påhlstorp (1985). Most of the technical equipment is still the same today on farms of comparable size and production methods. However, herds of pigs and cattle are larger now, and therefore new equipment is being used. The average Swedish dairy farm is 39% larger (49 cows) than the EU-15 average (35.5 cows) and herd size is growing rapidly. The climate in winter at the study farms is not as cold as that in central Europe or northern Sweden, although air temperature was below 0ºC for about 3 months in 2006 (average -0.1ºC, Dec-Feb.) In the period June-August, the average temperature was 17.8ºC in 2005 and 19.1ºC in 2006. It only exceeded 30ºC for a period longer than three hours on seven occasions. Because of the climate, it is necessary to have artificial heating in buildings for sows (farrowing section). In all other buildings the animals produce enough heat themselves to keep the house warm. When breeding cattle or dry sows some farmers accept a low inside temperature. Swedish animal welfare legislation requires more space per animal than most other countries. Slatted floors in lying areas are only permissible for fattening steers. Cages for laying hens have to include a sand-bath, nest and perches. Another difference is that sows can only be kept in crates occasionally and can never be tied up. The purpose of this study was to collect data on energy use on modern farms of a size and with a level of technical equipment that could be expected to be in use for the next 10-15 years. The data obtained were then added to data from Nilsson & Påhlstorp (1985).The survey was conducted on 16 farms with buildings mainly constructed during the past 10 years and with modern equipment. All these farms except one were in the south of Sweden (Skåne, Halland, Lat. 55-56ºN) and the last one 180 km south-east of Stockholm (Lat. 58ºN). The study was structured as follows: - Four complete dairy farms were studied in detail and another three were studied because they had interesting technical equipment that was not installed on the first four farms. - Three farms with pigs were studied. One had an FTS-system (Farrowing To Slaughter in the same pen), one a farrowing-growing system (Farrowing to approx. 25 kg/11 weeks in the same pen), and one had fattening pigs (approx. 25-110 kg). - Two farms with laying hens were studied. One had furnished cages and the other had laying hens on floors. - Two broiler houses were studied. - Four different types of grain dryers were studied: batch drier, circulating batch drier, continuous drier and batch-in-bin drier with multiple stirring augers. To measure electricity use, electricity meters of the type used by power companies were installed. These meters distinguishing between feeding, ventilation, light, manure handling and, for some plants, cleaning/disinfection, heating, milking and packing of eggs. When all these were measured there was still some more electricity that was impossible to measure or to distribute to the right category. This was categorised as Miscellaneous. Meters were also installed for estimating the power (W) used at one piglet farm and at two dairy farms. The data were processed and are included in the appendices in order to allow estimations to be made for other farms and evaluations to reduce the use of energy (power). In milk production, energy use was between 930 and 1540 kWh/cow per year (0.125-0.203 kWh/L milk). The functions that used most energy were milking and feeding, which together used 65-75% of total energy. On farms that used a wheel loader and tractor for mixing Total Mixed Ration (TMR), energy consumption was higher than on those farms that used electrical engines for mixing. One litre of diesel was set to 9.8 kWh. Production of piglets (approx. 25 kg) used 689 kWh/sow per year, which means about 28.7 kWh/25 kg pig (assuming 24 piglets/sow & year). During the fattening period (25-110 kg), energy use was 20 kWh per pig. The total energy requirement to produce finishing pigs from birth to 110 kg was thus 48.7 kWh/110 kg pig or 1163 kWh/sow per year, assuming a sow produces 24 piglets per year. This can be compared with the FTS-system, which uses 2431 kWh/sow per year. This difference is not completely caused by different breeding systems but is more likely to be due to difference in buildings, and therefore to a greater need for energy for lighting and ventilation, and a higher temperature in the farrowing unit. The farm that used less energy heated the breeding areas with a heat-pump, while another used diesel as fuel. Most energy was used for heating (including the use of heat lamps). If the building for dry sows needs mechanical ventilation and artificial light, then this leads to a greater use of energy. Egg production with laying hens in furnished cages used 3.1 kWh/year per hen, while a system with free hens used 5.0 kWh/year per hen. Light and ventilation fans used most energy, but were also the functions that showed the greatest differences between the systems. The difference in energy used for light is most probably due to the higher light intensity and to the two extra hours of light each day in the system with free layers. In broiler production, the largest use of energy was heating (84%), followed by light (10.7%) and ventilation (3.6%). The energy needed to produce one broiler (1.5 kg) was an estimated 0.91 kWh. This value is an average of five batches due to large variations between batches. The use of electricity differed from 6% to 20% between similar houses. All the grain driers except the batch-in-bin drier used between 4.2 and 9.1 kWh per 1000 kg of grain during 2005 and 2006. Due to bad weather conditions the use of energy was 30% higher in 2006. The batch-in-bin dryer used 12.0 kWh per 1000 kg of grain 2006. Due to different technical standards the values are not directly comparable, but the data are valid for the separate functions.
energy; power; farm buildings; lighting; heating
Landskap, trädgård, jordbruk : rapportserie
Publisher: Faculty of Landscape Planning, Horticulture and Agricultural Sciences, Swedish University of Agricultural Sciences
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