Mapping the carbon footprint of milk production from cattle: A systematic review.

Recently, many studies have assessed the carbon footprint of bovine milk production. However, due to the complexity of life cycle assessment, most studies have analyzed research farms or "representative" farms, which do not capture farm variability. Furthermore, the lack of consistency in most studies means that we can seldom compare the footprint between different countries. To address this issue, we performed a systematic review of the literature, removing inconsistencies in life cycle assessment papers, namely the functional unit, allocation to milk, and global warming potential. We analyzed papers that accounted for many farms to address the variability of production systems within the countries. We found 21 papers from 19 countries; footprint recalculations were necessary for 16 papers. New Zealand, Uruguay, the United Kingdom, Australia, and the United States had a footprint <1 kg of carbon dioxide equivalents (CO2e) per kilogram of fat- and protein-corrected milk, whereas 5 countries had a footprint >2 kg CO2e·kg-1 fat- and protein-corrected milk. The change in functional unit resulted in a small effect on the final footprint, whereas the global warming potential change was dependent in on the greenhouse gas profile for each country. Countries where milk is produced mainly as a pasture-based system had most of their footprint (>50%) associated with the emission of methane from enteric fermentation, whereas other countries (especially from Europe and North America) had a significant share of emissions from manure management, feed production, and fertilizer use. This different greenhouse gas profile allow decision makers to tailor mitigation options specific for each country. The choice of the allocation method had a strong influence in the final footprint. We suggest that for future studies, authors adhere to the International Dairy Federation guidelines. When this is not possible, we suggest a set of extra information to be reported, allowing recalculations as done in this review.

In situ nitrous oxide and dinitrogen fluxes from a grazed pasture soil following cow urine application at two nitrogen rates.

Cattle grazing of pastures deposits urine onto the pasture soil at high nitrogen (N) rates that exceed the pasture's immediate N demands, increasing the risk of N loss. Nitrous oxide (N2O), a greenhouse gas, and dinitrogen (N2) are lost from the cattle urine patches. There is limited information on the in situ loss of N2 from grazed-pasture systems which is needed for understanding pasture soil N dynamics and balances. The 15N flux method was used to determine N2 and N2O fluxes over time following synthetic urine-15N application at either 400 or 800 kg N ha-1 to a grazed perennial pasture soil. Results showed that daily N2O fluxes were higher under 800 kg N ha-1 than under 400 kg N ha-1, but there was no significant difference in N2 fluxes. Cumulative N2O emissions from soil with 400 kg N ha-1 and 800 kg N ha-1 applied represented 0.16 ± 0.08% and 0.43 ± 0.08% of deposited N, respectively, while emitted N2 accounted for 32.1 ± 4.1% and 14.4 ± 1.7%, respectively, over 95 days after urine application. Codenitrification and denitrification co-occurred, with denitrification accounting for 97.9 to 98.5% of total N2 production. Recovery of urine-15N in pasture decreased with increasing N rate with 14.7 ± 0.5% and 9.9 ± 0.8% recovered at 400 and 800 kg N ha-1, respectively after 95 days. The N2O/(N2 + N2O) product ratio was generally higher during periods of nitrification of urine-N (the first month after urine application) but with no clear relationship to other measured variables. Contrary to our hypothesis, an elevated urine-N rate did not enhance N2 loss. This is speculated to be due to enhanced ammonia volatilisation and transfer of N as nitrate, to deeper soil layers. Soil relative gas diffusivity indicated that high N2 fluxes resulted from entrapped N2 diffusing from the draining soil.

Eutrophication and climate change impacts of a case study of New Zealand beef to the European market.

OBJECTIVE: Beef production in the Lake Taupo region of New Zealand (NZ) is regulated for nitrogen (N) leaching. The objectives of this study were to 1) evaluate the implications of nitrogen emission limitations on eutrophication and climate change impacts of NZ beef through its life cycle to a European market and uniquely link it to 2) estimation of the reduction in these impacts that can be funded by the consumer's willingness to pay (WTP) a premium for a low environmental-impact product. METHOD: The cradle-to-market Life Cycle Assessment (LCA) of NZ beef on the European market included beef production on farms, meat processing, packaging and transport stages. Various beef production systems in the Lake Taupo region were modelled: farm systems with and without regulated N leaching limits in place (using N fertiliser inputs of 0 and 100 kg N/ha/year respectively) using suckler beef or beef derived from surplus calves from a dairy farm. The FARMAX model was used to model farm productivity and profitability under these various scenarios, whereas the OVERSEER® model was used to model field/farm emissions (N, phosphorus (P)) and the NZ greenhouse gas (GHG) Inventory model was used to estimate total GHG emissions. Eutrophication and climate change impacts of NZ beef to the European market were calculated using recent regionalised LCA indicators. We estimated freshwater and marine eutrophication impacts of European beef using published N emissions to water and air. We estimated the European consumer's WTP for beef with positive environmental attributes based on a meta-regression analysis based on 21 published studies and compared farmer's profit for the farm system scenarios. RESULTS: When using common P-driven eutrophication indicators, the farms using 100 kg fertiliser-N/ha/year appeared to have a lower freshwater eutrophication impact than farms using no N fertiliser, which is in contradiction with the local freshwater policy for N regulations. When the contribution of both N and P were accounted for, the farms using no N fertiliser had the lowest estimated impact. Comparison with published environmental footprint of beef from Europe showed lower climate change and eutrophication impacts for NZ beef, thus showing potential positive environmental attributes for NZ beef. The European consumer's WTP (32% price premium) for such a beef product with low environmental impacts could offset the cost to farmers for implementing the reduction of N emissions. CONCLUSIONS: Bridging the gap between local freshwater policy and LCA indicators starts by considering both P and N emissions and impacts. Combining an environmental LCA with an economic analysis revealed that the consumer willingness to pay could compensate for the environmental cost of protecting the lake that currently only the farmers are bearing.

Reducing Ammonia Emissions from Dairy Cattle Production via Cost-Effective Manure Management Techniques in China.

This study analyzed ammonia reduction potential and related costs and benefits of several ammonia emission reduction technologies applicable for dairy production from cattle in China. Specifically, these included diet manipulation, manure acidification, manure/slurry covers, and solid manure compaction. Ammonia emissions for China were estimated using the GAINS and NUFER models, while mitigation potentials of technologies were determined from laboratory studies. Ammonia reduction potentials from dairy production in China ranged from 0.8 to 222 Gg NH3 year-1 for the selected technologies. Implementation costs ranged from a savings of US$15 kg-1 NH3 abated to an expenditure of US$45 kg-1 NH3 abated, while the total implementation costs varied from a savings of US$1.5 billion in 2015 to an expenditure of a similar size. The best NH3 reduction technology was manure acidification, while the most cost-effective option was diet optimization with lower crude protein input. For most abatement options, material costs were the critical element of overall costs. The fertilizer value of manure could partly offset the implementation cost of the options tested. Furthermore, benefits due to avoided health damage, as a result of reducing NH3 emissions, could make all abatement options (except for manure compaction) profitable on the scale of a national economy.

The value of manure - Manure as co-product in life cycle assessment.

Livestock production is important for food security, nutrition, and landscape maintenance, but it is associated with several environmental impacts. To assess the risk and benefits arising from livestock production, transparent and robust indicators are required, such as those offered by life cycle assessment. A central question in such approaches is how environmental burden is allocated to livestock products and to manure that is re-used for agricultural production. To incentivize sustainable use of manure, it should be considered as a co-product as long as it is not disposed of, or wasted, or applied in excess of crop nutrient needs, in which case it should be treated as a waste. This paper proposes a theoretical approach to define nutrient requirements based on nutrient response curves to economic and physical optima and a pragmatic approach based on crop nutrient yield adjusted for nutrient losses to atmosphere and water. Allocation of environmental burden to manure and other livestock products is then based on the nutrient value from manure for crop production using the price of fertilizer nutrients. We illustrate and discuss the proposed method with two case studies.

Water scarcity footprint of dairy milk production in New Zealand - A comparison of methods and spatio-temporal resolution.

Water scarcity footprinting now has a consensual life cycle impact assessment indicator recommended by the UNEP/SETAC Life Cycle Initiative called AWaRe. It was used in this study to calculate the water scarcity footprint of New Zealand (NZ) milk produced in two contrasting regions; "non-irrigated moderate rainfall" (Waikato) and "irrigated low rainfall" (Canterbury). Two different spatial and temporal resolutions for the inventory flows and characterisation factors (CFs) were tested and compared: country and annual vs. regional and monthly resolution. An inventory of all the consumed water flows was carried out from cradle to farm-gate, i.e. from the production of dairy farm inputs to the milk and meat leaving the dairy farm, including all water uses on-farm such as irrigation water, cow drinking water and cleaning water. The results clearly showed the potential overestimation of a water scarcity footprint when using aggregated CFs. Impacts decreased by 74% (Waikato) and 33% (Canterbury) when regional and monthly CFs were used instead of country and annual CFs. The water scarcity footprint calculated at the regional and monthly resolution was 22 Lworld eq/kg FPCM (Fat Protein Corrected Milk) for Waikato milk, and 1118 Lworld eq/kg FPCM for Canterbury milk. The contribution of background processes dominated for milk from non-irrigated pasture, but was negligible for milk from irrigated pasture, where irrigation dominated the impacts. Results were also compared with the previously widely-used Pfister method (Pfister et al., 2009) and showed very similar ranking in terms of contribution analysis. An endpoint indicator was evaluated and showed damages to human health of 7.66 × 10-5 DALY/kg FPCM for Waikato and 2.05 × 10-3 DALY/kg FPCM for Canterbury, but the relevance of this indicator for food production needs reviewing. To conclude, this study highlighted the importance of using high-resolution CFs rather than aggregated CFs.

Global environmental costs of China's thirst for milk.

China has an ever-increasing thirst for milk, with a predicted 3.2-fold increase in demand by 2050 compared to the production level in 2010. What are the environmental implications of meeting this demand, and what is the preferred pathway? We addressed these questions by using a nexus approach, to examine the interdependencies of increasing milk consumption in China by 2050 and its global impacts, under different scenarios of domestic milk production and importation. Meeting China's milk demand in a business as usual scenario will increase global dairy-related (China and the leading milk exporting regions) greenhouse gas (GHG) emissions by 35% (from 565 to 764 Tg CO2eq ) and land use for dairy feed production by 32% (from 84 to 111 million ha) compared to 2010, while reactive nitrogen losses from the dairy sector will increase by 48% (from 3.6 to 5.4 Tg nitrogen). Producing all additional milk in China with current technology will greatly increase animal feed import; from 1.9 to 8.5 Tg for concentrates and from 1.0 to 6.2 Tg for forage (alfalfa). In addition, it will increase domestic dairy related GHG emissions by 2.2 times compared to 2010 levels. Importing the extra milk will transfer the environmental burden from China to milk exporting countries; current dairy exporting countries may be unable to produce all additional milk due to physical limitations or environmental preferences/legislation. For example, the farmland area for cattle-feed production in New Zealand would have to increase by more than 57% (1.3 million ha) and that in Europe by more than 39% (15 million ha), while GHG emissions and nitrogen losses would increase roughly proportionally with the increase of farmland in both regions. We propose that a more sustainable dairy future will rely on high milk demanding regions (such as China) improving their domestic milk and feed production efficiencies up to the level of leading milk producing countries. This will decrease the global dairy related GHG emissions and land use by 12% (90 Tg CO2eq reduction) and 30% (34 million ha land reduction) compared to the business as usual scenario, respectively. However, this still represents an increase in total GHG emissions of 19% whereas land use will decrease by 8% when compared with 2010 levels, respectively.

Environmental impacts and resource use of milk production on the North China Plain, based on life cycle assessment.

Life cycle assessment methodology was used to quantify the environmental impacts and resource use of milk production on the North China Plain, the largest milk production area in China. Variation in environmental burden caused by cow productivity was evaluated, as well as scenario analysis of the effects of improvement practices. The results indicated that the average environmental impact potential and resource use for producing 1kg of fat and protein corrected milk was 1.34kgCO2eq., 9.27gPO43-eq., 19.5gSO2eq., 4.91MJ, 1.83m2 and 266L for global warming potential (GWP), eutrophication potential (EP), acidification potential (AP), non-renewable energy use (NREU), land use (LU) and blue water use (BWU; i.e. water withdrawal), respectively. Feed production was a significant determinant of GWP, NREU, LU and BWU, while AP and EP were mainly affected by manure management. Scenario analysis showed that reducing use of concentrates and substituting with alfalfa hay decreased GWP, EP, AP, NREU and LU (by 1.0%-5.5%), but caused a significant increase of BWU (by 17.2%). Using imported soybean instead of locally-grown soybean decreased LU by 2.6%, but significantly increased GWP and NREU by 20% and 6.9%, respectively. There was no single perfect manure management system, with variable effects from different management practices. The environmental burden shifting observed in this study illustrates the importance of assessing a wide range of impact categories instead of single or limited indicators for formulating environmental policies, and the necessity of combining multiple measures to decrease the environmental burden. For the North China Plain, improving milking cow productivity and herd structure (i.e. increased proportion of milking cows), combining various manure management systems, and encouraging dairy farmers to return manure to nearby crop lands are promising measures to decrease multiple environmental impacts.

Nutrient losses and greenhouse gas emissions from dairy production in China: Lessons learned from historical changes and regional differences.

The dairy industry in China was rapidly expanded and intensified from 1980 to 2010, engendering potential long-term impacts on the environment and natural resources. However, impacts of dairy intensification on nitrogen (N) and phosphorus (P) losses and greenhouse gas (GHG) emissions were unknown. This study was undertaken to examine these relations using the NUtrient flows in Food chains, Environment and Resources use (NUFER)-dairy model. Results showed that milk yield increased by 64% from 1980 to 2010 on average, and the use of concentrate feeds increased by 57% associated with a shift of production from traditional and grassland systems to collective and industrialized systems. At herd level, the N use efficiency (NUE; conversion of N inputs to products) doubled from 7 to 15%, and the P use efficiency (PUE) increased from 10 to 17%, primarily resulting from increased milk yield per cow. In contrast, at the system level, NUE showed a small increase (from 10 to 15%, associated with reduced gaseous losses) while PUE decreased from 46 to 30% due to a large increase in manure discharges. This is attributed to decoupling of feed and dairy production, as the proportion of manure N and P recycled to cropland decreased by 52% and 54%, respectively. Despite this, the average total N loss decreased from 63 to 48gkg-1 milk, and the average GHG emissions from 1.7 to 1.1kgCO2equivalentkg-1 milk associated with increased per-cow productivity. However, average P loss increased from 1.4 to 2.8gPkg-1 milk due to higher discharge rate to wastewater and landfill in collective and industrialized systems. Anyhow, average N and P losses exceeded levels in developed countries. There were large regional variations in nutrient use efficiency, nutrient losses and GHG emissions in China, largely determined by the dairy production structure. Average N losses and GHG emissions per unit of milk showed a negative correlation with production intensification based on the proportion of farms in collective or industrialized systems, while average P losses per unit of milk in different regions showed a positive relationship with intensification. In conclusion, dairy intensification was associated with increased milk yield per cow and reduced average N losses and GHG emissions per unit of milk, but reduced system level PUE and manure recycling contributed to high levels of total N and P losses. Dairy production in China is likely to continue to be intensified as a result of rising milk demand, and significant improvements must be made in manure management to control N and P losses and GHG emissions.

Salt as a mitigation option for decreasing nitrogen leaching losses from grazed pastures.

BACKGROUND: The main source of nitrogen (N) leaching from grazed pastures is animal urine with a high N deposition rate (i.e. per urine patch), particularly between late summer and early winter. Salt is a potential mitigation option as a diuretic to induce greater drinking-water intake, increase urination frequency, decrease urine N concentration and urine N deposition rate, and thereby potentially decrease N leaching. This hypothesis was tested in three phases: a cattle metabolism stall study to examine effects of salt supplementation rate on water consumption, urination frequency and urine N concentration; a grazing trial to assess effects of salt (150 g per heifer per day) on urination frequency; and a lysimeter study on effects of urine N rate on N leaching. RESULTS: Salt supplementation increased cattle water intake. Urination frequency increased by up to 69%, with a similar decrease in urine N deposition rate and no change in individual urination volume. Under field grazing, sensors showed increased urination frequency by 17%. Lysimeter studies showed a proportionally greater decrease in N leaching with decreased urine N rate. Modelling revealed that this could decrease per-hectare N leaching by 10-22%. CONCLUSIONS: Salt supplementation increases cattle water intake and urination frequency, resulting in a lower urine N deposition rate and proportionally greater decrease in urine N leaching. Strategic salt supplementation in autumn/early winter with feed is a practical mitigation option to decrease N leaching in grazed pastures.

Nitrous oxide and greenhouse gas emissions from grazed pastures as affected by use of nitrification inhibitor and restricted grazing regime.

Integration of a restricted grazing regime in winter with the use of a nitrification inhibitor can potentially reduce N2O emissions from grazed pasture systems. A three year field study was conducted to compare annual N2O emission rates from a "tight nitrogen" grazed farmlet with those from a control farmlet. The control farmlet was managed under a conventional rotational all-year grazing regime, while the "tight nitrogen" farmlet was under a similar grazing regime, except during winter and early spring seasons when cows grazed for about 6h per day. A nitrification inhibitor (dicyandiamide, DCD) was applied onto the "tight nitrogen" farmlet immediately after grazing through winter and early spring. A chamber technique was used to measure N2O emissions in several paddocks from each farmlet during three contrasting seasons each year. The IPCC (Intergovernmental Panel on Climate Change) inventory methodology was used to estimate CH4 and indirect N2O emissions and the life cycle assessment (LCA) methodology was used to calculate CO2 emissions from the farm systems. The individual and combined effects of restricted grazing and DCD use on N2O emissions were also determined. During the late spring/summer and autumn periods, N2O emission rates were generally similar between the two farmlets. The use of a restricted grazing regime and DCD reduced N2O emissions from the grazed farmlet during the winter/early spring seasons by 43-55%, 64-79% and 45-60% over each of the three years, respectively. The use of restricted grazing and DCD both resulted in a similar reduction in N2O emissions, but there was no significant further reduction from the combination of these technologies. For the three study years, the annual N2O emission rate from the "tight nitrogen" farmlet was 20% lower, on average, than from the control. Total annual greenhouse gas (GHG) emissions, however, were only 5% less in the "tight nitrogen" system.

Use of labelled nitrogen to measure gross and net rates of mineralization and microbial activity in permanent pastures following fertilizer applications at different time intervals.

Measurements of some of the main internal N-cycling processes in soil were obtained by labelling the inorganic N pool with the stable isotope of nitrogen ((15)N). The (15)N mean pool dilution technique, combined with other field measurements, enabled gross and net N-mineralization rates to be resolved in grassland soils, which had previously either received fertilizer N (F), or had remained unfertilized (U) for many years. The two soils were subdivided into plots that received N at different time intervals (over 3 weeks), prior to (15)N measurements being made. By this novel approach, possible 'priming' effects over time were investigated to try to overcome some of the temporal problems of isotopic labelling of soil N (native plus fertilizer) and to identify possible changes in a range of primary N-transformation processes. The results suggested that an overall stimulation of microbially mediated processes occurred with all N treatments, but there were inconsistencies associated with the release of N, both in the timing and the degree to which different processes responded to the application of fertilizer N. The rates of these processes were, however, within the range of previously reported data and the (15)N measurements were not adversely affected by the differences in N pools created by the treatments. Thus, the mean pool dilution technique was shown to be applicable to agricultural soils, under conditions relevant to grass swards receiving fertilizer. For example, between the U and F treatments, the size of inorganic N pools increased by five-fold and gross rates of mineralization reached 3.5 and 4.8 microg N g(-1) (dry soil) d(-1), respectively, but did not vary greatly with the timing of N applications. A correlation (r(2) = 0.57) was found between soil respiration (which is relatively simple to measure) and net mineralization (which is more time consuming), suggesting that the former might be used as an indicator of the latter. Although this relationship was stronger in previously unfertilized soils, the similarities found with fertilized soils suggest that this approach could be used to obtain information of wider agronomic value and would, therefore, warrant further work under a range of soil conditions.