Carbon and water footprint of beef cattle

Carbon and water footprint of beef cattle

Total life cycle measurement of the carbon and water footprint of beef cattle in South Africa

Industry Sector: Cattle and Small Stock

Research Focus Area: The economics of red meat consumption and production in South Africa Livestock production with global competitiveness: Breeding,physiology and management

Research Institute: Agricultural Research Council – Animal Production Institute

Researcher: Dr. Susanna Maria Grobler PhD

Title Initials Surname Highest Qualification Research Institution
Prof MGG Chagunda PhD UoH
Mr M Ferreira B(Agric) ARC
Dr B Greyling PhD ARC
Mr J Hendriks MSc ARC
Ms Z King RPL ARC
Prof FWC Neser PhD UFS

Year of completion : 2020

Aims of the project

  • To generate results from a complete extensive beef cattle production cycle to calculate the carbon and water footprint
  • To measure water intake and requirements of different breeds and quantify the effect of season on the water intake of young bulls
  • To measure enteric methane emission on an extensive beef cattle production cycle

Executive Summary

With the media often reporting alarming figures of water use and greenhouse gas emissions, without discussing the methods and context of the calculation, consumers have the perception that meat consumption is damaging to the environment. However, it is important to consider the broader context of ruminants in semi-arid to mesic pastoral agricultural ecosystems. Grazing cattle are an integral part of the grassland ecosystem and play a critical role in the recycling of nutrients within these ecosystems. Plant communities depend on grazing for removal of aftermath and the distribution of seeds.

The objectives of the project were: to generate results from a complete production cycle of extensive beef cattle to calculate the carbon and water footprint; to measure water intake and requirements of different breeds and quantify the effect of season on the water intake of young bulls; and to measure methane emission from an extensive beef cattle production cycle.

The blue water footprint from a full production cycle of extensive beef cattle (weaned heifers producing and weaning their first calves) was calculated at the end of the production cycle (July 2017 – July 2019). There is an on-going debate regarding the use of blue water and green water in the water footprint of beef cattle. Some literature state that environmental impacts are predominantly associated with blue water, and argue that green water could be excluded from the equation. It is also argued that green water consumption does not contribute to regional freshwater scarcity. It is claimed that freshwater problems are primarily associated with blue water scarcity and lesser associated with competition over green water resources. However, there is also the argument that both blue water and green water must be accounted for. Average water consumption differed between 22.8 liter per animal per day when the heifers were still growing to 55.5 liters when animals were lactating, relating to between 6.3 and 12.3 percent of live weight. The blue water footprint for an extensively managed heifer from weaning until her first calf is weaned (weaning weight 185kg) were 25 890 liters (25-month cycle).

Water consumption for post-weaning bulls between 196 and 454kg differed between 12.5 and 55 liters per day per animal. Water intake was the highest during the hot summer months with average water intake 10.5% of body weight and lowest at spring with average water intake 6.4% of body weight.

Green water footprint was linked to the dry matter produced per unit of water evapotranspired by making use of water-use efficiency. However, this method used to calculate the green water footprint did not render sensible results. It is therefore suggested that evapotranspiration should be physically measured in the grazing camps within the different plant communities at different grazing heights, physiological stages of the grass and over different seasons. This will produce a much more accurate and more sensible water-use efficiency for natural veld.

Significant less methane was produced during spring 2017 (76g/day) with average heifer weight of 296kg and summer 2018 (88g/day) with average heifer weight of 347kg. This may be due to higher grazing quality when the rangeland was in a vegetative growth state and heifers were growing. The highest methane production was obtained in winter 2018 (134kg/day) with average heifer weight of 421kg and summer 2019 (149g/day) with average weight of 437kg after calving when heifers were in early lactation.

The blue water footprint from a full production cycle of extensive beef cattle (weaned heifers producing and weaning their first calves) was calculated at the end of the production cycle (July 2017 – July 2019). Average water consumption differed between 22.8 liter per animal per day when the heifers were still growing to 55.5 liters when animals were lactating, relating to between 6.3 and 12.3% of live weight. The blue water footprint for an extensively managed heifer from weaning until her first calf is weaned (25-month cycle) was 25 890 liters. The method used to calculate the green water footprint did not present sensible results. With approval of phase 2 of the project, evapotranspiration (ET) will be physically measured in the grazing camps within the different plant communities over different seasons. This will produce a much more accurate water-use efficiency for natural veld. It will also give a better picture regarding ET differences between parts of dense shrubs and trees which is present in the camps but not utilized by the animals, which can then be excluded from the green water footprint. Water consumption from post-weaning bulls differed between 13 and 55 liters per day per animal weighing between 196 and 454kg. Water intake was the highest during the hot summer months with average water intake 10.5% of body weight and lowest at spring with average water intake 6.4% of body weight. The highest methane production per livestock unit (LSU) was obtained in summer 2019 (76kg/LSU/year) with average heifer weight of 437kg and autumn 2019 (166kg/LSU/year) with average weight of 448kg after calving when heifers were in early lactation. Methane production results from the current project is lower than results published by Du Toit et al. (2013). The calculations from Du Toit et al. (2013) were based on the Tier 2 level (IPCC, 2006) whereas current results were measured from individual animals with a laser methane detector.

POPULAR ARTICLE

Water intake and methane production of extensive beef cattle

By Dr SM Grobler and Prof MM Scholtz

The carbon and water footprints associated with livestock production should be recognized. With water being one of the top five likely global risks, as reported by the World Economic Forum (2017), it is predicted that in 2025, 64% of the world population will live in a water-deprived basin, compared to 38% in 2009. It is also predicted that South Africa will be facing high levels of water stress by 2040. With the media often reporting alarming figures of water use and greenhouse gas emissions, without discussing the methods and context of the calculation, consumers have the perception that meat consumption is damaging to the environment in terms of water use. It has even been suggested by some groups that reductions in global ruminant numbers could make a substantial contribution to climate change mitigation goals. The popular press is fueling these sentiments with slogans telling consumers to eat less meat. It is therefore understandable that consumers increasingly demand that the production of food should be sustainable in relation to resource availability. However, the broad context of ruminants in semi-arid to mesic pastoral agricultural ecosystems must be considered. News related to the implications for greenhouse gas emissions from the beef industry and its impact on the environment in the popular press often relates to examples where animal production has not followed best management practices. When considering good management practices, a balance can be found between the need for agricultural products without destroying the natural resource base.

Grazing cattle forms part of the grassland ecosystem and plays a critical role in the recycling of nutrients within these ecosystems. Plant communities depend on grazing for removal of moribund material, the distribution of seeds, and the provision of open niches that can increase sward biodiversity. It must also be remembered that livestock are important to mankind since most of the world’s vegetation biomass is rich in fibre. Only ruminants can convert this high fibre containing vegetation into high quality protein sources for human consumption. Indirectly, the environmental footprint of beef is a reflection of mankind’s demand for high quality protein in their diet. The arguments to substitute livestock products with grain and vegetables to feed people implies that all sources of food production require a similar and equal quantity and quality of resources. However, large regions worldwide are completely unsuitable for growing grains or vegetables. In South Africa ruminant animal production is the most sustainable way of food production in these areas.

The largest source of greenhouse gases in beef production comes from the methane produced in the gastrointestinal tract, accounting for 28% of global methane emissions. It is important that the actual methane production and water intake of different breeds, cattle at different physiological stages and in different seasons is accurately measured.

A study was undertaken to (1) generate results from a complete production cycle of extensive beef cattle to calculate the carbon and water footprint; (2) measure water intake and requirements of different breeds and quantify the effect of season on the water intake of young bulls; and (3) measure methane emission from an extensive beef cattle production cycle.

To calculate the water footprint of extensively managed heifers from weaning until they wean their first calf, only blue water (water consumed by the animals from surface and ground water) was taken into account as the animals grazed natural rangeland (sourish mixed bushveld), not suitable for crop production. It can be argued that the rain would nourish the natural rangeland, irrespective if the cattle were grazing the land or not. Therefore, unless the cattle destroy or harm the rangeland, or if the rangeland has the potential to be converted into highly producing crop production land, the inclusion of the green water footprint (from the rainwater that grows the natural veld), does not make sense. If extensively managed beef cattle are produced under sensible management strategies, the grazing cattle can actually be a net benefit to the water cycle and assist climate stability. This is achieved through the role natural rangeland plays in carbon sequestration, improving soil nutrient cycling, increased soil stability, enhanced watershed function and enhanced biodiversity.

To calculate the blue water footprint, 26 Bonsmara heifers at the Roodeplaat campus were divided into two uniform groups of 13 heifers each according to date of birth and weaning weight. Water meters were installed at the water troughs and weekly water intake of both groups were measured.

The blue water footprint from a full production cycle of extensive beef cattle (weaned heifers producing and weaning their first calves) was calculated at the end of the production cycle (July 2017 – July 2019). Average water consumption differed between 22.8 liter per animal (269 kg) per day in July 2017 when heifers were still growing to 55.5 liters when animals (462 kg) were lactating. This water intake results relate to water intake as percentage of live weight of between 6.3% and 12.3%. Water intake per 1 livestock unit (LSU) was 34 liters for both groups, which is lower than the expected water intake of 44 liters per LSU published by other authors. However, it was observed that animals consume some water from rain puddles after heavy rain. It must also be noted that rangeland dry matter content differs constantly throughout the seasons. The blue water footprint for an extensively managed heifer from weaning until her first calf with a weaning weight of 185 kg is weaned was 25890 liters (25-month cycle).

Water meters were installed at the Bull Testing Stations at Irene, Pretoria and Armoedsvlakte, Vryburg, with water intake recorded weekly per pen. Water intake from 83 post-weaning bulls of different breeds including Afrisim, Angus, Boran, Brahman, Braunvieh, Chianina, Hereford, Santa Gertruides and Simbra was measured over a 12-week period. Water consumption was measured during spring, summer and autumn months. Unfortunately, no water intake was measured during mid-winter. Water consumption from these bulls with body weight ranging between 196 kg and 454 kg differed between 12.5 and 55.0 liters per day per animal. Water intake was the highest during the hot summer months with average water intake 10.5% of body weight and lowest at spring with average water intake of 6.4% of body weight.

Enteric methane production was measured on individual heifers using the Laser Methane Detector (LMD). Four 60 second repeated measurements were taken on 10 consecutive days every 3rd month throughout the production cycle. The LMD gives its measurements as parts per million per meter (ppm/m) which accounts for the plume effect. Assuming that the plume density in the cow’s breath has a 1 m radius from the point source, this simply gives us a concentration in ppm (ml/m3). Results from this study was reported in grams per day by means of a reworked version of the deterministic model developed in 2009. Significant less methane was produced during spring 2017 (19 kg/LSU/year) with average heifer weight of 296 kg and summer 2018 (26 kg/LSU/year) with average heifer weight of 347 kg. This may be due to higher grazing quality when the rangeland was in a vegetative growth state and heifers were still growing. The highest methane production per LSU was obtained in summer 2019 (76 kg/LSU/year) with average heifer weight of 437 kg and autumn 2019 (66 kg/LSU/year) with average weight of 448 kg after calving when heifers were in lactation. Although the high methane production in summer 2019 cannot be solely explained by dry matter intake, several studies have suggested that the level of intake rather than digestibility, is the main determinant of methane emissions. Methane yield (g/day) to animal weight (kg) ratio differed between 0.26 for growing heifers and 0.34 for lactating heifers.

From this study it was found that the blue water footprint of a production cycle from a weaned heifer producing and weaning her first calf over a 25-month period was 25 890 liter water. Water intake was measured from post-weaning bull calves at both the Irene bull testing station in Gauteng and the bull testing station at Vryburg, North West. Water intake was measured during spring, summer and autumn months. Results from this study indicated that water intake from these bulls was the highest during the hot summer months (10.5% of body weight) and lowest during spring (6.7% of body weight). Methane production differed between 19 kg/LSU/year (average weight 296 kg) when heifers were still growing and 76 kg/LSU/year (average weight 437 kg) when heifers were lactating.

Please contact the Primary Researcher if you need a copy of the comprehensive report of this project – Dr Grobler on mgrobler@arc.agric.za

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