Prof Michiel Scholtz, specialist researcher in applied animal genetics at the Agricultural Research Council, shares a South African perspective on livestock production and how it relates to greenhouse gases and water usage.
Prof Scholtz writes:
“Quoting percentages does not always make sense. In industrialised countries the Greenhouse Gas (GHG) emissions for agriculture are less than 6%, simply because the contribution of their energy sectors, mines, etc. to GHG emissions is very large. In non-industrialised countries the relative contribution by agriculture can be 40% to 50%, but the actual contribution can be considerably less than the 6% of the industrialised countries. When considering mitigation options, it is obvious that a 10% reduction in GHG emissions by the energy and mining sectors would be far more effective than a 10% reduction in the 5% to 10% contribution of agriculture. So, the proposed “meat free once a week” argument will not do much to rectify the problem, as other sources of protein for human consumption are required, and they may have an even higher carbon footprint.
Livestock has been accused of using large quantities of water to produce beef and milk. Some of the assumptions used to calculate the water footprint, or the amount of water required to produce livestock products, are questionable. In studies with more realistic and justifiable assumptions, the water requirement for red meat production and for the production of total milk solids in whole milk and in skim milk powder, is much lower.
It must be realised that ruminant livestock are important to mankind since most of the world’s vegetation biomass is rich in fibre. Only ruminants can convert this high fibre vegetation into high quality protein sources (i.e. meat and milk) for human consumption. This needs to be balanced against the concomitant production of methane. Despite this important role ruminants play, they are specifically targeted and singled out as producers of large quantities of GHG that contribute to climate change,
Livestock production and greenhouse gases
Livestock agriculture is the world’s largest user of land resources and Sub-Saharan Africa is no different to the rest of the world. In South Africa, approximately 84% of the surface area is available for farming, but only 13% of this area is arable. The greater part of South Africa (71%) is only suitable for extensive livestock farming. In Africa, subsistence farmers farm livestock for multiple purposes. Rural households depend on livestock for milk, meat, hides, horns, fertiliser and income, making it central to the livelihoods and wellbeing of rural communities.
Although primary beef cattle farming (cow-calf production cycle) is largely extensive in South Africa, more than 75% of cattle slaughtered in the formal sector are finished in feedlots on maize and maize by-products. The cow-calf portion of the production cycle (the extensive part in South Africa) accounts for 72% of the nutrient requirements from conception to harvest. Under natural rangeland conditions, decomposition of manure is aerobic, leading to the production of carbon dioxide (CO2)) and water (H2O) as end products. Part of the CO2 released from the aerobic digestion of manure is absorbed during the regrowth of the surrounding vegetation, rather than released into the atmosphere. The carbon sequestration measurement of this has been neglected and therefore the quantitative effect is not known.
This is in sharp contrast to intensive systems in large parts of Europe and North America, where great quantities of manure are stockpiled, often for long periods. These manure piles undergo anaerobic decomposition. Anaerobic decomposition of manure, as found in intensive cow-calf systems, feedlots and intensive dairy systems, produces methane (CH4) as one of the major end products.
It is also relevant to consider calf finishing systems, or the post weaning phase. Cattle in South Africa are fattened in feedlots for approximately 110 days, which means that they produce GHG for only 110 days before being slaughtered. Cattle on rangeland/pasture need more than 200 days to finish to the same carcass classification, because of the lower quality feed [they take in] compared to a feedlot diet. Furthermore, there is substantial evidence indicating that organic production systems consume more energy and have a bigger carbon footprint than conventional production systems. For example, grass-fed cattle require roughly three times more energy per kilogram of weight gain and release more than double the quantity of GHG per kilogram of weight gain than conventional feedlot cattle. Most consumers purchasing organic products do not know that such systems may have a higher carbon footprint [than that of conventional systems].
The effect of methane from livestock on global warming is totally overplayed by groups with their own agendas. They frequently quote values and figures that are based on questionable assumptions or they are just wrong.
The most important greenhouse gases are:
- Carbon dioxide – 49%
- Methane – 18%
- Nitrate gases – 6%
Sources of anthropogenic methane production:
- Gas and coal mining / Natural gas – 19%
- Enteric fermentation (ruminants) – 16%
- Rice cultivation – 12%
- Biomass burning (veld fires) – 8%
- Landfills (dumping sites) – 6%
- Animal waste (including manure) – 5%
A simple calculation can be made using this information. Ruminants contribute 21% of anthropogenic methane production (16% from fermentation and 5% from waste). However, methane forms only 18% of GHG, and 21% of 18% is less than 4%. Thus, the contribution of ruminants to GHG is less than 4%.
It should however be noted that the global warming potential of CH4 is approximately 23 times more than that of CO2, but its atmospheric lifetime is 12 years, compared to the 100 year to 200 year lifetime of CO2. Although it has a larger effect, the duration of the effect is much shorter. This is a frequently ignored aspect.
It is also important to ask the question, what will happen to the vegetation if it is not consumed by productive (meat, milk, fibre) ruminants? There are three possibilities:
- It can be consumed by other animals that will also emit CH4
- It can burn and produce CO2 that is released into the atmosphere with an atmospheric lifetime of 100 years to 200 years
- It can rot and produce Nitrate gases with a global warming potential of approximately 300 times more than that of CO2.
Livestock production and water usage
The water footprint or the amount of water required to produce 1kg of product is of relevance. Some of the assumptions on which published figures are based, are debatable. For example, in one calculation where it is claimed that the water requirement is 15 500 L/kg beef, it is assumed that it takes three years to produce 200kg of boneless beef. In the estimate, only 155 L of water were calculated for drinking, cleaning and post farm gate activities; the remainder was accounted for by irrigation of the crops used for cattle feed and the rain that fell on the property. The estimates of water utilised for 1 kg pork (4 800 L), 1 kg chicken (3 900 L) and 1 L milk (1 000 L) also appear extreme. These figures have been widely quoted by anti-livestock activists. In studies with more realistic and justifiable assumptions, it was calculated that the water requirement for red meat production was 18L to 540 L/kg, and 80L to 320 L/kg. The significant variation is due to differences in production systems and management efficiency. The water requirement for the production of total milk solids in whole milk, and in skim milk powder, is respectively 14.4 L/kg and 15.8 L/kg.
In extensive conditions (such as those found in Sub-Saharan Africa) the water need of the animal itself is a major contributor to the total requirement, which amounts to about 4 L per kg feed dry matter intake, with a 50 % increase in hot weather.
The argument is sometimes advanced that the water used in livestock production should rather be channelled to crop and vegetable production which requires less water, but this is not true for areas where crop and vegetable production is not viable. In South Africa, agriculture takes up 74.5% of the rainfall. From this, 60% is utilised by the natural vegetation, 12% by dryland crop production and 2.5% by irrigation.
However, natural vegetation (rangelands) and dryland crop production uses only ‘green’ water, which is rain water stored in the soil after precipitation. It is called ‘green’ water because only green plants growing in the soil utilise this water. It cannot be used by, or for, anything else. In extensive grazing systems the natural vegetation, which is the food source of livestock, uses only ‘green’ water. This water cannot be used for crop production. It is often in areas unsuitable for crop production because of inadequate rainfall and/or the poor quality of soils. The quantity of water used for livestock production (e.g. kgs meat) in the extensive rangeland areas is therefore irrelevant in the calculation of water consumption for beef production. Natural rangelands not utilised by livestock or game would result in water being wasted.
In terms of food production, it means that green water can only be used for the production of meat or other animal produce under extensive grazing systems on natural rangelands, as is the case in South Africa. These systems are critical for the provision of food security in such areas, which dominate almost all less-developed countries. Natural rangelands in these areas do not use ‘blue’ water (runoff water to streams, dams etc.) or water stored in underground aquifers. This is completely different from the intensive systems of Europe and North America. Since only the rain that infiltrated the soil is used, there is no water cost for the production of the rangeland. Nothing needs to be done to capture or extract this water other than applying good rangeland management to ensure a dense basal vegetation cover, thus avoiding excessive runoff that would lead to damaging floods, erosion and silting up of dams.
A balance between food and nutrition needs
In addition to the formulation of strategies aimed at greener food environments, health considerations (such as nutrient-density), in addition to carbon footprint calculations, should be considered. Choosing nutrient-rich foods and reducing the intake of nutrient-poor, energy dense foods is one way of reducing the amount of food (and resources) required to meet nutritional needs.
Food systems should produce more nutritious food, not just more food, and guarantee an adequate supply of animal source foods. Any reduction in the consumption of meat and dairy products may compromise the dietary intakes of those nutrients that meat and dairy products supply in relatively large proportions. The risk is greatest where those nutrients are already in short supply or where there is evidence of low nutrient status. For children in South Africa this includes energy, protein, vitamin A, vitamin C, thiamine, riboflavin, niacin, vitamin B6, folate, Vitamin B12, iron, zinc and calcium.
The lower bio-availability and quality of these nutrients from plant-based sources should also be taken into consideration when comparing different food sources. In terms of protein produced per unit of water, animal products are more efficient than fruit and other food crops such as grains and vegetables. It is therefore important not to overlook the importance of animal products in providing bio-available mineral nutrients.
Differences in production systems between countries and regions can affect the carbon and water footprint of livestock products. Current methods to estimate these footprints are largely based on generic values from northern hemisphere countries, that do not make provision for different production systems. – Prof Michiel Scholtz, ARC.
For more information, contact Prof Michiel Scholtz at GScholtz@arc.agric.za.