Consumptive water use in livestock production

נשלח 23 ביולי 2011, 2:06 על ידי Sustainability Org   [ עודכן 8 באוג׳ 2014, 13:04 ]
יוני 2011

כמה ליטר מים נדרשים לצורך ייצורו של סטייק?
בעבודת המחקר שלהלן, אשר נכתבה באוניברסיטת גוטבורגס בשבדיה, נמצא כי בתהליך הייצור של בשר בקר למאכל, נדרשים בממוצע כ-115,000 ליטר מים (יש שונות גדולה בהיקף צריכת המים לגידול בקר, בהתאם לאזור הגיאוגרפי בו מגדלים את הבקר).

אם סטייק ממוצע שוקל כ-300 גרם, הרי שלצורך ייצורו של סטייק בודד נדרשת כמות מים של כ-35,000 ליטר.

מקטעים רלבנטיים מהמחקר מובאים להלן:

Consumptive water use in livestock production – Assessment of green and blue virtual water contents of livestock products

Ylva Ran, Göteborgs university, June 2010

Summary
Distribution and use of fresh water resources are a widely discussed matter and the competition and requirement is increasing while resources are decreasing globally. Amongst the largest consumers are households, industry and food production where food production requires by far the largest amount of water. The role and scale of the consumptive water use for food production associated with livestock production is quite unknown but definitely of a significant magnitude. In a situation with increasing world population coupled to rising food requirements the role of livestock productions is predicted to grow even faster. An assessment of the livestock sector is therefore of great importance. A thorough calculation of water productivity of livestock production enables a valid picture of the situation and what possibilities that is available for development towards a more sustainable use of water resources and increased water productivity in livestock production.

This study aims to estimate the consumptive water use of livestock production in terms of green and blue water and virtual water content of livestock products. Six animal production systems have been analyzed for seven selected regions to generate results that will enable assessment for the role of livestock production in water resource requirements and what improvements can be adapted to enable increased water productivity.

Results primarily illustrate that consumptive water use and virtual water content of livestock production is largest in Asia, in particular South and Central Asia. The division between blue and green water resources further pinpoints that withdrawal and product virtual water content of blue water resources is strongly dominated by South and Central Asia. The values are generally larger for ruminant products and beef in particular whereas milk constitutes an exception with the lowest virtual water content. Another important result from this research is the distinctly higher consumptive water use as well as virtual water contents in the developing world in relation to developed regions.

1. Introduction
In this study water is considered as virtual water which is water used for agricultural or industrial production and further divided into
Blue water resources which is the liquid water resources in aquifers, rivers and lakes
Green water resources which is rainfall as soil moisture and the flows of such in form of
evapotranspiration.

All food we eat requires a green water flow as transpiration from plants. For animal products in the food production green water is indirectly connected to the product in form of pasture, fodder and grains that are eaten by the animals. This feature is considered to multiply the overall water consumption of the animal food stuffs and constitutes the majority of water used for such production.

With increasing population the overall food demand will rise. It is predicted that not only will the demand of animal food stuffs increase also but the fraction of which animal food stuffs constitute of the per capita intake. Therefore it is fundamental to estimate and understand the water used for livestock production and how it differs between livestock products, systems and regions.

2. Background
2.4 Water use in livestock production
The overall demand for water in livestock production is influenced by several factors such as type of animal, its activity, feed intake and diet, quality of available water, temperature of water and temperature of the ambient environment.

Different products will require different amounts of water in their production. This requirement is as mentioned also depending on production site, water use efficiency of feed baskets and specific time as well as other production conditions. To produce a certain amount of meat, milk or egg it is necessary to take into consideration a number of parameters. What kind of animal is used for production, where the animal is kept, what the animal diet constitutes of, where the feed is
produced etc. will have an impact on the water requirement of the product.

Livestock production requires high amounts of water. One kilogram of grain used in livestock feed requires about 1000 to 2000 kg of water if the feed is grown in the Netherlands or Canada. The same grain will, however, require approximately 3000 to 5000 kg of water if grown in an arid region like Egypt or Israel. That difference in water requirement will have an impact on the total water use for a specific product relying on the grain from a particular region. Livestock in itself contains between 5 and 20 times more virtual water per kg product than crop products (Chapagain & Hoekstra, 2003).

Consumptive water use in livestock are generally divided into two categories
• Drinking and process water – direct blue water use
• Water use for production of feed, fodder and grazing – blue and green water use

2.4.1 Drinking and process water
Water is consumed by the animal itself in terms of drinking needs to support the physiological functions of the animal. Approximately 60-70 % of an animal body is water and animals need water for services that maintain vital physiological functions. The water intake of livestock is maintained by drinking and eating. Water leaves the body through respiration, evaporation, defecation and urination.

Processing of animal products, including slaughtering and tanning of skins, demand a high level of hygiene and quality when processed. This in turn results in a large consumption of water and a large amount of waste water generated from these activities. Generally poultry processing facilities and dairy products have a higher demand for water per unit of weight than processing facilities for carcasses of cattle and pork. Tanning consumes large amounts of water as well. However, the
environmental impact of the emitted pollutants from such processing is considered to be of greater concern.

There is also a water requirement for services such as cooling and washing of the animal and feed production. Production facilities need to be kept clean and animal product production need processing, which also requires water. The water use per animal differs with different production systems. In extensive systems the water requirement per animal will be greater than for intensive (industrialized) production systems. However, the intensive system will have a larger service water demand for cooling and cleaning of the facilities. Extensive systems tend to use more water for the animals´ feed supply. In some regions, where extensive livestock systems are dominating, the fresh water withdrawal for the drinking and servicing of livestock will be a large fraction of the total withdrawal. In most regions, however, the water use for drinking and servicing livestock constitutes only a small fraction of the total water requirement for the livestock production. Globally the water consumption of these processes is estimated to be only 0.6 percent of all freshwater use.

2.4.2 Water for production of feed, fodder and grazing
Undoubtedly the largest amount of water used in livestock production is the amount used for feed production and the amount of feed produced is growing globally. Livestock stand for the largest anthropogenic land use in the world where the majority of land and water are dedicated to feed production.

Feed production is argued to affect green and blue water flows in three ways - through withdrawal of blue water for irrigation, through land cover change (e.g. when rain forest is converted to agricultural land) and through alterations in water division due to changes in land use management.

The different approaches in allocation of water use will generate widely different results when it comes to livestock production. If, as in the first approach, a grazing ecosystem is healthy and the extra cost of water use is not included in the water requirement is estimated to 12 000 liters of water per kg meat. If, instead conditions follows the second approach, the water requirements will be as high as 30 300 liters of water per kg of meat.

2.7 Virtual water
The amount of water that is required for producing a certain industrial or agricultural product or service is defined as “virtual water”. The virtual water is simply water embodied in the product and not real water.

2.7.1 Virtual water content and water footprints

The virtual water content of a product is simply the freshwater embodied in that particular item. It refers to the volume of water required for the complete production chain of the product.

4.2 Virtual water content
The results of total consumptive green, blue and total water use and virtual water content for each livestock products and regions are summarized and presented in table 5 below. The total consumtive water use estimated in this research constitutes of 9,680 km3 of water where 8,600 km3 is constituted by green and 1,085 km3 is constituted by blue water resources.

Table 5: Summary of results calculated with FPD and LPJmL models in this study.
livestock production water consumption

Source:
Consumptive water use in livestock production – Assessment of green and blue virtual water contents of livestock products

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