Natalie Doran-Browne

Nutrient density as a metric for comparing greenhouse gas emissions from food production

Dietary Guidelines for many countries recommend that people should eat ‘nutrient dense’ foods, which are foods with a high nutrient to energy ratio; and that people should limit their intake of saturated fat, added salt or added sugar. In addition, consumers and environmentalists increasingly want their food to be produced with a low impact on the environment, including reduced greenhouse gas emissions (GHGE), yet agriculture is a major source of CH4 and N2O emissions, as well as producing CO2 emissions. Current research on GHGE from agriculture does not incorporate the nutritional value of the foods studied. However, the nutritional content of food is important, given the prevalence of malnutrition, including obesity (due to over-consumption of foods high in energy yet low nutritional density), and the negative health impacts they produce. This paper introduces the metric, emissions/unit nutrient density, and compares the results with three other metrics: emissions intensity (t CO2e/t product), emissions/t protein and emissions/GJ. The food products examined are wheat flour, milk, canola oil, lean lamb, lean beef, untrimmed lamb and untrimmed beef. The metric t CO2e/unit nutrient density was the preferred metric to use when examining GHGE from food production because it compares different types of products based on their nutritional value, rather than according to singular nutrients such as protein, or specific attributes such as product weight or energy content. Emissions/unit nutrient density has the potential to inform consumer choices regarding foods that have a higher nutritional content relative to the GHGE generated. Further analysis would be useful to develop and expand the use of this metric further.

Northern Australian pasture and beef systems. 1. Net carbon position

The beef industry in northern Australia manages ~15 million cattle, grazed on 250 million hectares of grassland and savanna woodland. The large size of the beef industry results in significant quantities of greenhouse gases being emitted to the atmosphere through ruminant livestock enteric methane production. However, livestock emissions are only one component of the carbon cycle in which grazing businesses operate. Livestock grazing also affects carbon stocks and fluxes in pasture, woody vegetation, soil and from fire through the consumption of forage and other landscape impacts. Little knowledge is available on the impact of different grazing management strategies on the ‘net carbon position’ incorporating carbon stocks and greenhouse gas emissions when grazing savanna woodlands. The Wambiana grazing trial in northern Queensland, Australia, provides an opportunity to assess carbon stocks and greenhouse gas emissions (reported as t CO2-e) associated with livestock, pasture, woody vegetation, soil and fire under alternative grazing management strategies (moderate and heavy stocking rate) over a 16-year period. The results indicate that tree biomass and woody vegetation dynamics dominate the carbon stocks and fluxes in grazed savanna woodlands. During the trial, both moderate and heavy stocking rate treatments had a positive net carbon balance, with the moderate stocking rate treatment having a better ‘net carbon position’ (19 t CO2-e per ha) than the heavy stocking rate treatment (9 t CO2-e per ha), primarily due to less livestock emissions and greater pasture biomass and soil C. These results add to the previously published benefits on land condition and economic return of grazing at moderate stocking rates, compared with heavy stocking rates.

Modelling the potential of birdsfoot trefoil (Lotus corniculatus) to reduce methane emissions and increase production on wool and prime lamb farm enterprises

In Australia in 2011 the Federal government introduced a voluntary offset scheme called the Carbon Farming Initiative, which allows farmers to receive carbon credits when they reduce or sequester greenhouse gas emissions. Various mitigation options have since been explored for their potential to reduce on-farm greenhouse gas emissions. Among these is the use of alternative pastures that lower methane (CH4) production of grazing animals such as Lotus corniculatus, a legume that contains condensed tannins that inhibit the formation of CH4 in the rumen. Lotus has other benefits for sheep production such as increased wool growth, liveweight gain and fecundity. This study modelled the potential emission, production and economic outcomes for wool and lamb enterprises that incorporate lotus in their pastures, evaluating the impact of existing farm productivity, lotus intake and carbon price. Depending on the amount of lotus consumed and the CH4 reduction rate, CH4 emissions fell by 0.02–0.38 t carbon dioxide equivalents (CO2e)/ha and 0.05–0.48 t CO2e/ha on wool and prime lamb enterprises, respectively. At a price of

Carbon-neutral wool farming in south-eastern Australia

6/t CO2e potential offset income attributable to use of lotus across all enterprises was

Northern Australian pasture and beef systems. 2. Validation and use of the Sustainable Grazing Systems (SGS) whole-farm biophysical model

0.12–2.91/ha. Increases in income from increased productivity were 15–30 times greater than from potential carbon offset income. Income was driven by the amount of lotus dry matter intake and the subsequent production benefits. Over a 10-year period prime lamb enterprises generated up to

A review of whole farm-system analysis in evaluating greenhouse-gas mitigation strategies from livestock production systems

50/ha in profit by using lotus, due to increased liveweight gain and fecundity. In most modelled scenarios wool enterprises would not cover the cost of lotus pasture establishment. This research demonstrated that 18–23% and 37–46% of lotus intake within the diet was required to generate production enough to cover pasture establishment costs on prime lamb and wool enterprises, respectively. Potential carbon offset income would not be sufficient for farmers to establish lotus without the productivity benefits. While extra profit may be gained on prime lamb enterprises through the use of lotus, problems with persistence must first be overcome for lotus to be adopted on farms.

Offsets required to reduce the carbon balance of sheep and beef farms through carbon sequestration in trees and soils

Ruminant livestock production generates higher levels of greenhouse gas emissions (GHGE) compared with other types of farming. Therefore, it is desirable to reduce or offset those emissions where possible. Although mitigation options exist that reduce ruminant GHGE through the use of feed management, flock structure or breeding management, these options only reduce the existing emissions by up to 30% whereas planting trees and subsequent carbon sequestration in trees and soil has the potential for livestock emissions to be offset in their entirety. Trees can introduce additional co-benefits that may increase production such as reduced salinity and therefore increased pasture production, shelter for animals or reduced erosion. Trees will also use more water and compete with pastures for water and light. Therefore, careful planning is required to locate trees where the co-benefits can be maximised instead of any negative trade-offs. This study analysed the carbon balance of a wool case study farm, Talaheni, in south-eastern Australia to determine if the farm was carbon neutral. The Australian National Greenhouse Gas Inventory was used to calculate GHGE and carbon stocks, with national emissions factors used where available, and otherwise figures from the IPCC methodology being used. Sources of GHGE were from livestock, energy and fuel, and carbon stocks were present in the trees and soil. The results showed that from when the farm was purchased in 1980–2012 the farm had sequestered 11 times more carbon dioxide equivalents (CO2e) in trees and soil than was produced by livestock and energy. Between 1980 and 2012 a total of 31 100 t CO2e were sequestered with 19 300 and 11 800 t CO2e in trees and soil, respectively, whereas farm emissions totalled 2800 t CO2e. There was a sufficient increase in soil carbon stocks alone to offset all GHGE at the study site. This study demonstrated that there are substantial gains to be made in soil carbon stocks where initial soils are eroded and degraded and there is the opportunity to increase soil carbon either through planting trees or introducing perennial pastures to store more carbon under pastures. Further research would be beneficial on the carbon-neutral potential of farms in more fertile, high-rainfall areas. These areas typically have higher stocking rates than the present study and would require higher levels of carbon stocks for the farm to be carbon neutral.

Influence of climate variability and stocking strategies on greenhouse gas emissions (GHGE), production and profit of a northern Queensland beef cattle herd

The Sustainable Grazing Systems (SGS) model is a biophysical, mechanistic whole-farm model that simulates pasture production based on climate and soil data. While the SGS model has been extensively used for southern temperate systems, the model has yet to be evaluated for use in the tropical rangeland systems of Australia. New pasture parameter sets were developed in SGS to represent groups of grasses with the following common characteristics: (1) 3P grasses represented tropical rangeland grasses that were perennial, palatable and productive, and (2) annual tropical grasses that include both productive and less productive grass species. Fifteen years of data from the long-term Wambiana grazing trial ~70 km south-west of Charters Towers, Queensland, were used to validate the model. The results showed that SGS is capable of representing northern Australian beef systems with modelled outputs for total standing dry matter and steer liveweight in agreement with the year-to-year variation in measured data over three different soil types and two stocking rates. Recommendations for further model development are made, such as incorporating fire, tree growth and the use of urea supplementation in the model. Further testing is required to verify that the new pasture parameter sets are suitable for other regions in northern Australia.

Carbon farming futures: filling the research gap program - round 2 progress report 2: 1 December 2013 to 30 April 2014

Recognition is increasingly given to the need of improving agricultural production and efficiency to meet growing global food demand, while minimising environmental impacts. Livestock forms an important component of global food production and is a significant contributor to anthropogenic greenhouse-gas (GHG) emissions. As such, livestock production systems (LPS) are coming under increasing pressure to lower their emissions. In developed countries, LPS have been gradually reducing their emissions per unit of product (emissions intensity; EI) over time through improvements in production efficiency. However, the global challenge of reducing net emissions (NE) from livestock requires that the rate of decline in EI surpasses the productivity increases required to satisfy global food demand. Mechanistic and dynamic whole farm-system models can be used to estimate farm-gate GHG emissions and to quantify the likely changes in farm NE, EI, farm productivity and farm profitability as a result of applying various mitigation strategies. Such models are also used to understand the complex interactions at the farm-system level and to account for how component mitigation strategies perform within the complexity of these interactions, which is often overlooked when GHG mitigation research is performed only at the component level. The results of such analyses can be used in extension activities and to encourage adoption, increase awareness and in assisting policy makers. The present paper reviews how whole farm-system modelling has been used to assess GHG mitigation strategies, and the importance of understanding metrics and allocation approaches when assessing GHG emissions from LPS.

Whole farm systems analysis of greenhouse gas abatement options for the southern Australian grazing industries: progress report 5

The sustainability of farming is important to ensure that natural resources remain available into the future. Ruminant livestock production generates more greenhouse gas emissions than other types of agricultural production and most livestock mitigation options to date have a modest greenhouse gas reduction potential ( 20 DSE/ha) has yet to be studied in Australia. The challenge is to sequester enough carbon to offset the higher level of emissions that these higher stocked farms produce. This study calculated the carbon balance of wool, prime lamb and beef enterprises using a range of stocking rates (6–22 DSE/ha) and levels of tree cover in two agroecological zones. Emissions from livestock, energy and transport were offset by the carbon sequestered in trees and soils. Additionally, the carbon balance was calculated of a case study, Jigsaw Farms, an intensive sheep and beef farm in south-eastern Australia. The methods used to calculate emissions and carbon stocks were from the Australian National Greenhouse Gas Inventory. The majority of stocking rates were carbon positive over a 25-year period when 20% of the sheep or beef enterprises were covered with trees. This study demonstrated that substantial reductions can be made in greenhouse gas emissions through the use of carbon sequestration, particularly in trees. The results showed that from 2000 to 2014 Jigsaw Farms reduced its emissions by 48% by sequestering carbon in trees and soil. The analysis of different stocking rates and tree cover provides an important reference point for farmers, researchers and policy analysts to estimate the carbon balance of wool, prime lamb and beef enterprises based on stocking rate and the area of tree cover.