A comparative analysis of on-farm greenhouse gas emissions from agricultural enterprises in south eastern Australia

Carbon sequestration and credit potential of gamhar (Gmelina arborea Roxb.) based agroforestry system for zero carbon emission of India

The agroforestry system is the best option to achieve the net zero carbon emissions target for India. Keeping this view, carbon sequestration and credit potential of gamhar based agroforestry system has been assessed. The experiment was carried out in randomized block design in seven different treatments with five replications. Gamhar tree biomass accumulation was higher in gamhar based agroforestry system compared to sole gamhar. Among different tree components, stem contributed a maximum to total gamhar tree biomass followed by roots, leaves and branches. The average contributions of stems, roots, leaves and branches in total tree biomass in two annual cycles (2016-17 and 2017-18) varied between 50 and 60, 19.8 and 20, 19.2 and 20, and 10.7 and 12.7 percent, respectively. In case of crops, above ground, below ground and total biomass was significantly higher in sole intercrops than gamhar based agroforestry system. Total (Tree + interrops + Soil) carbon stock, carbon sequestration, carbon credit and carbon price were significantly affected by treatments, and was maximum in Sole Greengram-Mustard. Net carbon emission was also recorded lowest in Sole Greengram-Mustard for which the values were 811.55% and 725.24% and 760.69% lower than Sole Gamhar in 2016-17, 2017-18 and in pooled data, respectively.

A meta-analysis of the genetic contribution to greenhouse gas emission in sheep

The objective of this study was to use a random-effects model of meta-analysis to merge various heritability estimates of different gas emission traits (methane yield [METY], methane production [METP], carbon dioxide production [CO₂ ], the sum of carbon dioxide and methane production [METP + CO₂ ], METP METP + CO 2 ratio, and oxygen consumption [O₂ ]) and their genetic association with growth and partial efficiency traits in sheep. A total of 53 genetic correlations and 47 heritability estimates from 13 scientific articles were used in the meta-analysis. The included papers were published between 2010 and 2022. To measure heterogeneity, Chi-square (Q) test was performed, and the I² statistic was determined. The average heritability estimates for the studied traits were low to moderate and ranged from 0.137 (for METY) to 0.250 (for METP + CO₂ ). The heterogeneity test of heritability estimates indicated that heritability estimates for METY, O₂ consumption, and METP METP + CO 2 had low Q values and non-significant heterogeneity (p > 0.10). However, the average heritability estimates for other traits experienced significant heterogeneities (p < 0.10). The genetic correlation estimate between METP with O₂ was -0.597 (p < 0.05), but its genetic correlations with other gas traits ranged from 0.593 (with METP + CO₂ ) to 0.653 (CO₂ ; p < 0.05). Also, mean estimates of genetic correlation between METP with live weight (LW), feed intake (FI), and residual feed intake (RFI) were 0.719, 0.598, and 0.408, respectively. The genetic correlations of CO₂ with performance traits varied from 0.641 (with RFI) to 0.833 (with FI; p < 0.05). This meta-analysis showed gas emission traits in sheep are under low-to-moderate genetic control. The average genetic parameter estimates obtained in this study could be considered in the genetic selection programmes for sheep, especially when there is no access to accurate phenotypic records or genetic parameter estimates for gas emission traits.

Carbon myopia: The urgent need for integrated social, economic and environmental action in the livestock sector

Livestock have long been integral to food production systems, often not by choice but by need. While our knowledge of livestock greenhouse gas (GHG) emissions mitigation has evolved, the prevailing focus has been-somewhat myopically-on technology applications associated with mitigation. Here, we (1) examine the global distribution of livestock GHG emissions, (2) explore social, economic and environmental co-benefits and trade-offs associated with mitigation interventions and (3) critique approaches for quantifying GHG emissions. This review uncovered many insights. First, while GHG emissions from ruminant livestock are greatest in low- and middle-income countries (LMIC; globally, 66% of emissions are produced by Latin America and the Caribbean, East and southeast Asia and south Asia), the majority of mitigation strategies are designed for developed countries. This serious concern is heightened by the fact that 80% of growth in global meat production over the next decade will occur in LMIC. Second, few studies concurrently assess social, economic and environmental aspects of mitigation. Of the 54 interventions reviewed, only 16 had triple-bottom line benefit with medium-high mitigation potential. Third, while efforts designed to stimulate the adoption of strategies allowing both emissions reduction (ER) and carbon sequestration (CS) would achieve the greatest net emissions mitigation, CS measures have greater potential mitigation and co-benefits. The scientific community must shift attention away from the prevailing myopic lens on carbon, towards more holistic, systems-based, multi-metric approaches that carefully consider the raison d'être for livestock systems. Consequential life cycle assessments and systems-aligned 'socio-economic planetary boundaries' offer useful starting points that may uncover leverage points and cross-scale emergent properties. The derivation of harmonized, globally reconciled sustainability metrics requires iterative dialogue between stakeholders at all levels. Greater emphasis on the simultaneous characterization of multiple sustainability dimensions would help avoid situations where progress made in one area causes maladaptive outcomes in other areas.

Mitigation of yield-scaled nitrous oxide emissions and global warming potential in an oilseed rape crop through N source management

Enhanced-efficiency nitrogen (N) fertilizers, such as those containing nitrification or urease inhibitors, can mitigate the carbon (C) footprint linked to the production of bioenergy crops through a reduction in direct nitrous oxide (N₂O) emissions and indirect N₂O losses. These indirect emissions are derived from ammonia (NH₃) volatilization, which also have important environmental and health implications. The evaluation of the global warming potential (GWP) of different N sources using site-specific data of yield and direct and indirect emissions is needed for oilseed rape under rainfed semi-arid conditions, especially when meteorological variability is taken into account. Using urea as a N source, the N₂O mitigation efficacy of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) alone or combined with the nitrification inhibitor 2-(3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture (DMPSA) was evaluated under field conditions in a rainfed oilseed rape (Brassica napus L.) crop. Two additional N sources from calcium ammonium nitrate (CAN), with and without DMPSA, were included. The GWP of the treatments was estimated considering the emissions from inputs, operations and other direct and indirect emissions of greenhouse gases (GHGs), such as methane (CH₄) and the volatilization of NH₃. We also measured the abundance of key genes involved in nitrification and denitrification to improve the understanding of N₂O emissions on a biochemical basis under the conditions of our study. The results show that due to the intense rainfall after fertilization and a rewetting event, N₂O losses from fertilizers without inhibitors were greater than those previously reported under Mediterranean conditions, while NH₃ losses were low and not affected by the urease inhibitor. The cumulative N₂O emissions (which were greatly influenced by a rewetting peak three months after fertilization) from the urea fertilization were significantly higher than those from CAN. The presence of NBPT significantly reduced N₂O losses by an average of 71%, with respect to urea. The use of DMPSA with CAN resulted in an abatement of N₂O emissions (by 57%) and a significant increase in oil yield in comparison with CAN alone. All inhibitor-based treatments were effective in abating N₂O emissions during the rewetting peak. The abundances of the nitrifier and denitrifier communities, especially ammonia-oxidizing bacteria (AOB), significantly decreased relative to the urea or CAN treatments as inhibitors were applied. Under the conditions of our study, the sustainability of a bioenergy crop such as oilseed rape can be improved by using inhibitors because they mitigated N₂O emissions and/or enhanced the oil yield.

Beef cattle production impacts soil organic carbon storage

Grazing of natural rangeland and seeded pasture is an important feeding strategy for the Canadian beef cattle industry. As a consequence, beef cattle population has a direct influence on the proportion of land base maintained as perennial forage, which in turn changes soil organic carbon (SOC) stocks. We examined historical relationships between the net change in SOC resulting from perennial/annual crop conversion and beef cattle populations. We observed strong negative linear relationships, both regionally and nationally, between the population of beef cattle and the estimated change in SOC (negative sign indicating soil C sink) resulting from the conversion of annual crops and vice versa. These relationships indicate that as beef cattle population declines there is a corresponding loss of SOC resulting from a reduction in the relative proportion of perennial to annual crops on the landscape. The annual C loss resulting from land use conversion was roughly equivalent to 62% (±13%) of the combined enteric and manure annual emissions of CH₄ and N₂O [(1400 (±440) kg CO₂ eq head^-1 yr^-1] resulting in net greenhouse gas emissions of 850 (±360) kg CO₂ eq head^-1 yr^-1. These results highlight the importance of an integrated analysis that considers land use conversion and its impact on SOC when assessing the environmental footprint associated with beef cattle production.

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

Previous studies of greenhouse gas emissions (GHGE) from beef production systems in northern Australia have been based on models of ‘steady-state’ herd structures that do not take into account the considerable inter-annual variation in liveweight gain, reproduction and mortality rates that occurs due to seasonal conditions. Nor do they consider the implications of flexible stocking strategies designed to adapt these production systems to the highly variable climate. The aim of the present study was to quantify the variation in total GHGE (t CO2e) and GHGE intensity (t CO2e/t liveweight sold) for the beef industry in northern Australia when variability in these factors was considered. A combined GRASP–Enterprise modelling platform was used to simulate a breeding–finishing beef cattle property in the Burdekin River region of northern Queensland, using historical climate data from 1982–2011. GHGE was calculated using the method of Australian National Greenhouse Gas Inventory. Five different stocking-rate strategies were simulated with fixed stocking strategies at moderate and high rates, and three flexible stocking strategies where the stocking rate was adjusted annually by up to 5%, 10% or 20%, according to pasture available at the end of the growing season. Variation in total annual GHGE was lowest in the ‘fixed moderate’ (~9.5 ha/adult equivalent (AE)) stocking strategy, ranging from 3799 to 4471 t CO2e, and highest in the ‘fixed high’ strategy (~5.9 ha/AE), which ranged from 3771 to 7636 t CO2e. The ‘fixed moderate’ strategy had the least variation in GHGE intensity (15.7–19.4 t CO2e/t liveweight sold), while the ‘flexible 20’ strategy (up to 20% annual change in AE) had the largest range (10.5–40.8 t CO2e/t liveweight sold). Across the five stocking strategies, the ‘fixed moderate’ stocking-rate strategy had the highest simulated perennial grass percentage and pasture growth, highest average rate of liveweight gain (121 kg/steer), highest average branding percentage (74%) and lowest average breeding-cow mortality rate (3.9%), resulting in the lowest average GHGE intensity (16.9 t CO2e/t liveweight sold). The ‘fixed high’ stocking rate strategy (~5.9 ha/AE) performed the poorest in each of these measures, while the three flexible stocking strategies were intermediate. The ‘fixed moderate’ stocking strategy also yielded the highest average gross margin per AE carried and per hectare. These results highlight the importance of considering the influence of climate variability on stocking-rate management strategies and herd performance when estimating GHGE. The results also support a body of previous work that has recommended the adoption of moderate stocking strategies to enhance the profitability and ecological stability of beef production systems in northern Australia.

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

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.

A new perspective on managing the onset of puberty and early reproductive performance in ewe lambs: a review

Global changes in industry and society have led us to reassess the numerous factors that combine to influence the time of onset of puberty and the efficiency of reproduction in young sheep. Age and weight have long been considered the dominant factors that influence the onset of puberty and, for many years, it has been accepted that these relationships are mediated by the hormone, leptin, produced by body fat. However, recent studies showing that muscle mass also plays a role have challenged this dogma and also presented new options for our understanding of metabolic inputs into the brain control of reproduction. Moreover, the possibility that an improvement in meat production will simultaneously advance puberty is exciting from an industry perspective. An industry goal of strong reproductive performance in the first year of life is becoming possible and, with it, a major step upwards in the lifetime reproductive performance of ewes. The concept of early puberty is not well accepted by producers for a variety of reasons, but the new data show clear industry benefits, so the next challenge is to change that perception and encourage producers to manage young ewes so they produce their first lamb at 1 year of age.

Greenhouse gas emissions and carbon sequestration by agroforestry systems in southeastern Brazil

Agrosilvopastoral and silvopastoral systems can increase carbon sequestration, offset greenhouse gas (GHG) emissions and reduce the carbon footprint generated by animal production. The objective of this study was to estimate GHG emissions, the tree and grass aboveground biomass production and carbon storage in different agrosilvopastoral and silvopastoral systems in southeastern Brazil. The number of trees required to offset these emissions were also estimated. The GHG emissions were calculated based on pre-farm (e.g. agrochemical production, storage, and transportation), and on-farm activities (e.g. fertilization and machinery operation). Aboveground tree grass biomass and carbon storage in all systems was estimated with allometric equations. GHG emissions from the agroforestry systems ranged from 2.81 to 7.98 t CO₂e ha^-1. Carbon storage in the aboveground trees and grass biomass were 54.6, 11.4, 25.7 and 5.9 t C ha^-1, and 3.3, 3.6, 3.8 and 3.3 t C ha^-1 for systems 1, 2, 3 and 4, respectively. The number of trees necessary to offset the emissions ranged from 17 to 44 trees ha^-1, which was lower than the total planted in the systems. Agroforestry systems sequester CO₂ from the atmosphere and can help the GHG emission-reduction policy of the Brazilian government.

The effect of earlier mating and improving fertility on greenhouse gas emissions intensity of beef production in northern Australian herds

Approximately 5% of Australian national greenhouse gas (GHG) emissions are derived from the northern beef industry. Improving the reproductive performance of cows has been identified as a key target for increasing profitability, and this higher efficiency is also likely to reduce the GHG emissions intensity of beef production. The effects of strategies to increase the fertility of breeding herds and earlier joining of heifers as yearlings were studied on two properties at Longreach and Boulia in western Queensland. The beef production, GHG emissions, emissions intensity and profitability were investigated and compared with typical management in the two regions. Overall weaning rates achieved on the two properties were 79% and 74% compared with typical herd weaning rates of 58% in both regions. Herds with high reproductive performance had GHG emissions intensities (t CO2-e t–1 liveweight sold) 28% and 22% lower than the typical herds at Longreach and Boulia, with most of the benefit from higher weaning rates. Farm gross margin analysis showed that it was more profitable, by $62 000 at Longreach and $38 000 at Boulia, to utilise higher reproductive performance to increase the amount of liveweight sold with the same number of adult equivalents compared with reducing the number of adult equivalents to maintain the same level of liveweight sold and claiming a carbon credit for lower farm emissions. These gains achieved at two case study properties which had different rainfall, country types, and property sizes suggest similar improvements can be made on-farm across the Mitchell Grass Downs bioregion of northern Australia.

The concordance between greenhouse gas emissions, livestock production and profitability of extensive beef farming systems

Here we examine the concordance among emissions, production and gross margins of extensive beef farming systems by modelling a range of scenarios for herd management, animal genotype and pasture nutritive quality. We based our simulations on a case-study farm in central Queensland, Australia, and studied the influence of interventions designed for emissions mitigation, increasing productivity, or increasing gross margin. Interventions included replacing urea supplementation with nitrate, finishing cattle on the perennial forage leucaena (L), herd structure optimisation (HO), higher female fecundity (HF), and a leucaena finishing enterprise that had net farm emissions equal to the baseline (leucaena equal emissions; LEE). The HO intervention reduced the ratio of breeding cows relative to steers and unmated heifers, and lowered the ratio of costs to net cattle sales. Gross margin of the baseline, nitrate, L, LEE, HO and HF scenarios were AU$146 000, AU$91 000, AU$153 000, AU$170 000, AU$204 000 and AU$216 000, respectively. Enterprises with early joining of maiden heifers as well as HO and HF further increased gross margin (AU$323 000), while systems incorporating all compatible interventions (HO, HF, early joining, LEE) had a gross margin of AU$315 000. We showed that interventions that increase liveweight turnoff while maintaining net farm emissions resulted in higher gross margins than did interventions that maintained liveweight production and reduced net emissions. A key insight of this work was that the relationship between emissions intensity (emissions per unit liveweight production) or liveweight turnoff with gross margin were negative and positive, respectively, but only when combinations of (compatible) interventions were included in the dataset. For example, herd optimisation by reducing the number of breeding cows and increasing the number of sale animals increased gross margin by 40%, but this intervention had little effect on liveweight turnoff and emissions intensity. However, when herd optimisation was combined with other interventions that increased production, gross margins increased and emissions intensity declined. This is a fortuitous outcome, since it implies that imposing more interventions with the potential to profitably enhance liveweight turnoff allows a greater reduction in emissions intensity, but only when each intervention works synergistically with those already in place.

Modelling the influence of soil carbon on net greenhouse gas emissions from grazed pastures

Sequestering carbon (C) in soil organic matter in grassland systems is often cited as a major opportunity to offset greenhouse gas (GHG) emissions. However, these systems are typically grazed by ruminants, leading to uncertainties in the net GHG balance that may be achieved. We used a pasture model to investigate the net balance between methane (CH4), nitrous oxide (N2O) and soil C in sheep-grazed pasture systems with two starting amounts of soil C. The net emissions were calculated for four soil types in two rainfall zones over three periods of 19 years. Because of greater pasture productivity, and consequent higher sheep stocking rates, high-rainfall sites were associated with greater GHG emissions that could not be offset by C sequestration. On these high-rainfall sites, the higher rate of soil organic carbon (SOC) increase on low-SOC soils offset an average of 45% of the livestock GHG emissions on the modelled chromosol and 32% on the modelled vertosol. The slow rate of SOC increase on the high-SOC soils only offset 2–4% of CH4 and N2O emissions on these high-rainfall sites. On low-rainfall sites, C sequestration in low-SOC soils more than offset livestock GHG emissions, whereas the modelled high-C soils offset 75–86% of CH4 and N2O emissions. Greater net emissions on high-C soils were due primarily to reduced sequestration potential and greater N2O emissions from nitrogen mineralisation and livestock urine. Annual variation in CH4 and N2O emissions was low, whereas annual SOC change showed high annual variation, which was more strongly correlated with weather variables on the low-rainfall sites compared with the high-rainfall sites. At low-soil C concentrations, with high sequestration potential, there is an initial mitigation benefit that can in some instances offset enteric CH4 and direct and indirect N2O emissions. However, as soil organic matter increases there is a trade-off between diminishing GHG offsets and increasing ecosystem services, including mineralisation and productivity benefits.

Comparative analysis of greenhouse gas emissions from three beef cattle herds in a corporate farming enterprise

This study provided a gate-to-gate Life Cycle Assessment that modelled the greenhouse gas emissions (GHG) of three herds bred and grown by an integrated beef cattle enterprise across northern Australia. It involved modelling the GHG emissions of current herd management by the enterprise as a ‘baseline’ compared with ‘alternative scenarios’ of herd management. There were three herds (one herd of steers and two herds of heifers) each consisting of 5000 head of cattle. The baseline consisted of the steer herd grazing on growing then backgrounding properties and being finished at a feedlot. The two heifer herds grazed one respective backgrounding property each and were finished in a feedlot for their respective baselines. The alternative scenarios involved the steer herd bypassing the growing property and spending increased time at the backgrounding property. The heifer herds bypassed their respective backgrounding properties and they were grown and finished at a feedlot. The results show a 14% reduction of GHG emission intensities between the baseline and alternative scenario for steers and reductions of 29% and 4% between the baseline and alternative scenarios for the respective heifer herds. The variance in GHG emissions between the heifer herds can be explained by relative time spent grazing on the respective backgrounding properties and associated liveweight gain, versus time spent being grown and finished in the feedlot. In our modelling, herd GHG emission reductions occurred in the scenarios when time grazing on the growing or backgrounding properties (and associated liveweight gains) in the respective baselines exceeded 225–229 days for the heifer herds and between 206 days for the steers (depending on the relative liveweight gains on the properties). This means that if the cattle herds were to spend a longer time grazing on a property in their respective baselines than the number of days noted in our analysis, bypassing these properties would then result in net reductions in GHG emissions for the herds.

Carbon-neutral wool farming in south-eastern Australia

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.

Environmental performances of Sardinian dairy sheep production systems at different input levels

Although sheep milk production is a significant sector for the European Mediterranean countries, it shows serious competitiveness gaps. Minimizing the ecological impacts of dairy sheep farming systems could represent a key factor for farmers to bridging the gaps in competitiveness of such systems and also obtaining public incentives. However, scarce is the knowledge about the environmental performance of Mediterranean dairy sheep farms. The main objectives of this paper were (i) to compare the environmental impacts of sheep milk production from three dairy farms in Sardinia (Italy), characterized by different input levels, and (ii) to identify the hotspots for improving the environmental performances of each farm, by using a Life Cycle Assessment (LCA) approach. The LCA was conducted using two different assessment methods: Carbon Footprint-IPCC and ReCiPe end-point. The analysis, conducted "from cradle to gate", was based on the functional unit 1 kg of Fat and Protein Corrected Milk (FPCM). The observed trends of the environmental performances of the studied farming systems were similar for both evaluation methods. The GHG emissions revealed a little range of variation (from 2.0 to 2.3 kg CO2-eq per kg of FPCM) with differences between farming systems being not significant. The ReCiPe end-point analysis showed a larger range of values and environmental performances of the low-input farm were significantly different compared to the medium- and high-input farms. In general, enteric methane emissions, field operations, electricity and production of agricultural machineries were the most relevant processes in determining the overall environmental performances of farms. Future research will be dedicated to (i) explore and better define the environmental implications of the land use impact category in the Mediterranean sheep farming systems, and (ii) contribute to revising and improving the existing LCA dataset for Mediterranean farming systems.

Does producing more product over a lifetime reduce greenhouse gas emissions and increase profitability in dairy and wool enterprises?

Australian agriculture generated 15% of national greenhouse gas emissions (GHGE) in 2011, with CH4 and N2O accounting for 12 and 3% of national emissions, respectively. In 2011, the Australian government introduced a voluntary carbon offset scheme called the Carbon Farming Initiative, which enables farmers to earn carbon credits by lowering GHGE or sequestering carbon. One way of reducing emissions is to decrease the number of replacement animals required on-farm and increase the amount of product that animals produce across their lifetime. This study explores two options for reducing GHGE over an animal’s lifetime: (1) changing from an annual calving system to extended lactation system on dairy farms; and (2) increasing the longevity of ewes on wool enterprises to produce an extra year of wool and offspring. The biophysical models DairyMod and GrassGro were used to simulate the dairy and wool enterprises, respectively, and GHGE were calculated using the Australian National Inventory methodology. Extended lactation produced lower total emissions and emissions intensity (t CO2e/t milk fat plus protein) than annual calving and also resulted in higher operating profits. The GHGE from increasing longevity on sheep enterprises was similar to the baseline scenario, largely as a result of similar stocking rates. Extended lactation had greater potential of reducing emissions than increasing longevity on wool enterprises because there was a larger increase in the production of milk fat plus protein across cows’ lifetimes, as well as greater reductions in the number of replacement animals required on the enterprise. This research demonstrated that the profitability of farm enterprises would be driven more by productivity than claiming carbon offsets from these management changes.

Greenhouse gas emissions profile for 1 kg of wool produced in the Yass Region, New South Wales: A Life Cycle Assessment approach

The use of Life Cycle Assessment (LCA) to determine environmental impacts of agricultural production, as well as production by other industry sectors has increased. LCA provides an internationally accepted method to underpin labelling and marketing of agricultural products, a valuable tool to compare emissions reduction strategies and a means to identify perverse policy outcomes. A single-issue LCA focussing on greenhouse gas emissions was conducted to determine the emissions profile and carbon footprint of 19-micron wool produced in the Yass Region on the Southern Tablelands of New South Wales. Greenhouse gas emissions (in carbon dioxide equivalents; CO2-e) from the production of all enterprise inputs and from the production of wool on-farm were included. Total emissions were found to be 24.9 kg CO2-e per kg of greasy wool at the farm gate, based on a 4941 breeding ewe enterprise on 1000 ha, with a total greasy wool yield of 65.32 t per annum. The co-products included 174 t sheep meat as liveweight from wethers and cull ewes plus 978 maiden ewes sold off-farm as replacement stock. Total emissions from all products grown on 1000 ha were 2899 t CO2-e per annum. The relative contribution of greenhouse gas emissions from different components of the production system was determined. Direct emission of methane on-farm (86% of total) was the dominant emission, followed by nitrous oxide emitted from animal wastes directly (5%) and indirectly (5%), and decomposition of pasture residue (1%). Only 2% of total emissions were embodied in farm inputs, including fertiliser. The emissions profile varied according to calculation method and assumptions. Enteric methane production was calculated using five recognised methods and results were found to vary by 27%. This study also showed that calculated emissions for wool production changed substantially, under an economic allocation method, by changing the enterprise emphasis from wool to meat production (41% decrease) and by changing wool price (29% variability), fibre diameter (23% variability) and fleece weight (11% variability). This paper provides data specific to the Yass Region and addresses broader methodological issues, to ensure that future livestock emissions calculations are robust.

The Influence of Climate, Soil and Pasture Type on Productivity and Greenhouse Gas Emissions Intensity of Modeled Beef Cow-Calf Grazing Systems in Southern Australia

Simple Summary

Livestock production systems and the agricultural industries in general face challenges to meet the global demand for food, whilst also minimizing their environmental impact through the production of greenhouse gas (GHG) emissions. Livestock grazing systems in southern Australia are low input and reliant on pasture as a low-cost source of feed. The balance between productivity and GHG emission intensity of beef cow-calf grazing systems was studied at sites chosen to represent a range of climatic zones, soil and pasture types. While the climatic and edaphic characteristics of a location may impact on the emissions from a grazing system, management to efficiently use pasture can reduce emissions per unit product.

Abstract

A biophysical whole farm system model was used to simulate the interaction between the historical climate, soil and pasture type at sites in southern Australia and assess the balance between productivity and greenhouse gas emissions (expressed in carbon dioxide equivalents, CO₂-eq.) intensity of beef cow-calf grazing systems. Four sites were chosen to represent a range of climatic zones, soil and pasture types. Poorer feed quality and supply limited the annual carrying capacity of the kikuyu pasture compared to phalaris pastures, with an average long-term carrying capacity across sites estimated to be 0.6 to 0.9 cows/ha. A relative reduction in level of feed intake to productivity of calf live weight/ha at weaning by feeding supplementary feed reduced the average CO₂-eq. emissions/kg calf live weight at weaning of cows on the kikuyu pasture (18.4 and 18.9 kg/kg with and without supplementation, respectively), whereas at the other sites studied an increase in intake level to productivity and emission intensity was seen (between 10.4 to 12.5 kg/kg without and with supplementary feed, respectively). Enteric fermentationand nitrous oxide emissions from denitrification were the main sources of annual variability in emissions intensity, particularly at the lower rainfall sites. Emissions per unit product of low input systems can be minimized by efficient utilization of pasture to maximize the annual turnoff of weaned calves and diluting resource input per unit product.

Whole-farm systems analysis of Australian dairy farm greenhouse gas emissions

The Australian dairy industry contributes ~1.6% of the nation’s greenhouse gas (GHG) emissions, emitting an estimated 9.3 million tonnes of carbon dioxide equivalents (CO2e) per annum. This study examined 41 contrasting Australian dairy farms for their GHG emissions using the Dairy Greenhouse Gas Abatement Strategies calculator, which incorporates Intergovernmental Panel on Climate Change and Australian inventory methodologies, algorithms and emission factors. Sources of GHG emissions included were pre-farm embedded emissions associated with key farm inputs (i.e. grains and concentrates, forages and fertilisers), CO2 emissions from electricity and fuel consumption, methane emissions from enteric fermentation and animal waste management, and nitrous oxide emissions from animal waste management and nitrogen fertilisers. The estimated mean (±s.d.) GHG emissions intensity was 1.04 ± 0.17 kg CO2 equivalents/kg of fat and protein-corrected milk (kg CO2e/kg FPCM). Enteric methane emissions were found to be approximately half of total farm emissions. Linear regression analysis showed that 95% of the variation in total farm GHG emissions could be explained by annual milk production. While the results of this study suggest that milk production alone could be a suitable surrogate for estimating GHG emissions for national inventory purposes, the GHG emissions intensity of milk production, on an individual farm basis, was shown to vary by over 100% (0.76–1.68 kg CO2e/kg FPCM). It is clear that using a single emissions factor, such as milk production alone, to estimate any given individual farm’s GHG emissions, has the potential to either substantially under- or overestimate individual farms’ GHG emissions.