Regionalized estimates of enteric methane emissions from cattle raised in Italian territory

Within the framework of the Extended Partnership "Economic-Financial Sustainability of Systems and Territories" (GRINS Project Spoke 1, WP3), this work proposes a regional estimate of the amount of enteric methane produced by cattle raised in the Italian territory. These data will be used to create national and regional datasets that will be an integral part of the AMELIA platform and will be freely available for use by both public and private managers for environmental impact assessments in the livestock sector. To this purpose, the IPCC (level 2) provides statistical models capable of evaluating this parameter, considering population, daily weight gain, animal weight, type of breeding, and dietary intake for each considered breed. In particular, in the calculation of enteric emissions, 37 pure breeds with different attitudes (milk, meat, and dual-purpose) have been considered, whose population is significant (>1%) at the national and/or regional level. For each individual breed, six classes have been considered, considering age and gender of the cattle. In addition, 22 crossbred breeds have been added, 21 specifics to each region and one at the national level. Regional emissions have been estimated by considering the average population of each breed in the period 2019-2022, normalizing the contributions of the individual species in a delimited territory and/or geographic area. In this way, six contributions have been calculated for each Italian region, representing a statistical assessment of the emissions that will subsequently be confirmed in the field through direct measurements using innovative instrumental technologies. Overall, this analysis offers a comprehensive view of how regional factors, and the composition of cattle breeds can impact greenhouse gas emissions. These findings provide valuable guidance for advancing sustainability initiatives within the agricultural sector.


Introduction
The research highlights the significant role of methane (CH4) in the climate change, noting its Global Warming Potential (GWP) over 100 years (GWP100) as 28.5, which escalates to 81.7 in the short to medium term (GWP20).It points out that, unlike CO2, CH4 has a much shorter atmospheric lifespan of 15-20 years [1].This suggests that timely reduction of methane emissions could be a pivotal strategy in combating climate change.The agricultural sector emerges as a major contributor, responsible for roughly 20-25% of global greenhouse gas emissions in the past decade [2].At a national level, Italian agriculture generated 19.3 million tons of CO2 equivalent in methane emissions in 2020, making up 5.1% of the country's total greenhouse gas output [3].Livestock farming within the primary sector plays a substantial role, accounting for 14.5% of human-induced greenhouse gas emissions.Among these, ruminant livestock farming, particularly cattle, is a significant contributor, with nearly a third of 1269 (2023) 012028 IOP Publishing doi:10.1088/1755-1315/1269/1/012028 2 global anthropogenic CH4 emissions [4,5].
The predominant source of emissions within the agricultural sector is enteric fermentation in the digestive systems of ruminant animals, accounting for 70.2% of CH4 emissions in 2020, followed by manure management at 21.5%, and rice cultivation at 8.2%.Enteric methane of the bovine (79.6%) remains the primary contributor from the agricultural sector to global warming.Sheep contribute 9.3%, while buffalo produce 5.8% of enteric CH4 emissions [6].
Literature data highlight how the share of the livestock sector in greenhouse gas emissions is a variable parameter specific to each individual region and/or geographical area [4].For example, the United States Environmental Protection Agency reports that livestock contributes to less than 4% of direct emissions (excluding emissions from feed and fuel production) [2].In Australia, livestock is responsible for about 10% of direct emissions [7].In Brazil, direct emissions from livestock through enteric fermentation and manure management accounted for 20.8% of national emissions in 2016, which is 62% of the agricultural sector emissions [8].In 2000, India had the highest CH4 emissions among South Asian countries, with 61% originating from the agricultural sector (40% from enteric fermentation, 17% from rice cultivation, and 4% from manure management), and livestock accounted for emissions of 11.8 Tg CH4 [9], with a reduction of 22% (9.2 Tg of CH4) recorded over the following twenty years [10].
In the analysis of the entire life cycle (Life Cycle Assessment), various models were proposed to evaluate greenhouse gas emissions from different beef production systems in various countries of the European Union (Ireland, France, Italy, and Spain) [11][12][13].These studies suggest different strategies to reduce such emissions, but there are variations in the results due to differences in local conditions and methodologies used [14,15].
Within the framework of the Extended Partnership "Economic-Financial Sustainability of Systems and Territories" (GRINS Project Spoke 1, WP3), and in order to achieve the milestone "Set-up of LCI national and regional datasets for the main Italian production systems that will be part of AMELIA" and the Target "LCI national and regional dataset for the main Italian production system," this work has estimated enteric CH4 emissions for each of the Italian regions to provide a detailed picture of the existing situation in specific territorial areas.
Regarding the cattle rearing phase (enteric fermentation and management of livestock waste), the datasets (a total of 84) reported in the main international databases all pertain to livestock raised in foreign territories, specifically Brazil, South Africa, and New Zealand or are referred to the entire planet (Table 1).In particular, the need to create national and regional datasets arises from the necessity to carry out accurate environmental assessments that consider the local bovine population (breed and attitude), as well as the implemented rearing practices (barn, semi-barn, and pasture) and the pedo-climatic characteristics of the specific territory (forage crops and feeding).
To this regard, specific mathematical models (IPCC at level 2) were employed to accurately estimate methane emissions, considering various factors including animal weight and age, as well as feeding practices [16].The results highlight the regional variations in emissions and the specific impacts of different livestock categories, contributing to a comprehensive understanding of methane emissions within the Italian agricultural sector.

Italian cattle population
The Statistical section of the Veterinary Information System of the Italian Ministry of Health provides detailed data regarding the population of bovine species.For each individual Italian region, the data is further categorized by breed, gender, and age group [17].Specifically, the reported data covers the last fifteen years and is updated every six months.The cattle population is segmented into calves (0-6 months), yearlings (6-12 months), young steers and heifers (12-24 months), bulls, and cows (over 24 months).For this particular study, data from the four-year period of 2019-2022 were utilized.In each region, only breeds with an average population equal to or greater than 1% during the considered period were considered.

CH4 enteric emission evaluation
The estimates for enteric CH4 emissions were conducted using models provided by the IPCC (level 2).These models consider several parameters for each individual animal, including daily weight gain, weight, type of farming system (confined, semi-confined, pasture), forage/feed ratio characterizing the diet, and for lactating cows, the daily quantity of milk and its percentage concentration of fat [16].For each age category, enteric CH4 emissions were expressed as grams of CH4 per kilogram of live weight per day.
Similarly, annual enteric emissions were calculated, taking into consideration the population present for each category within the regional territory.Lastly, overall emissions were evaluated for each region, considering the aggregated contribution of all the individual age classes analyzed.

Selection of cattle breeds present in the Italian territory
This study specifically focused on the four-year period from 2019 to 2022, during which an average population of 5,582,393 cattle belonging to 110 different breeds was recorded [17].The breakdown by age class showed a predominance of cattle aged over 24 months (45.6%), while the female population exponentially increased with age, reaching nearly total representation (97.3%) for cows used in reproduction and milk production for the dairy industry.Within this distribution, the observed trend for different breeds is closely linked to the bovine species' purpose, primarily consisting of breeds specialized in either meat production or milk production (>90%).Additionally, there is a third category of cattle with a dual purpose (milk and meat production).
Specifically, considering the period from 2019 to 2022 and applying an 1% regional cut-off, a set of purebred cattle (37 in total) and one crossbred breed of significant national relevance and/or characteristic of specific Italian areas and territories were identified.Among these, four are specialized in milk production (mainly Frisian breed, constituting 45.7% of the total population), thirteen in raising cattle primarily destined for slaughter (mostly Crossbreeds accounting for 21.5% of the total), and the remaining breeds (9.3%) are characterized by a dual purpose.
The analysis of individual populations highlights that the Frisian breed, specialized in milk production, was the most numerous during the period from 2019 to 2022, with over 2.3 million head of cattle.Additionally, a quarter of the bovine population is represented by Crossbreeds, obtained from the crossbreeding of a bull specialized in meat production with a cow of dual purpose or specialized in milk production.While some breeds had limited national prominence, they held substantial regional importance.
For instance, Valdostana cattle reigned supreme in Valle d'Aosta, while Sardinian and derivative breeds played a significant role in Sardinia.The Podolica breed was of significance in Southern Italy.Noteworthy concentrations were also noted for breeds, such as Modicana and Cinisara in Sicily.Additionally, native breeds like Grigio Alpina, Reggiana, Sprintzen Pustertaller, and Rendena in the Alpine and Po Valley regions constituted a substantial segment of the bovine population in those areas.In sum, the study furnished a thorough panorama of Italy's diverse and regionally impactful cattle breeds during the 2019-2022 timeframe (Considered population equal to 5.563.668representing 99.7% of the entire cattles).

Estimation of enteric CH4 emissions
To estimate enteric methane emissions resulting from ruminants, the Intergovernmental Panel on Climate Change (IPCC) developed and later refined predictive models, typically organized into various complexity levels [16].Level 1 employs default emission factors derived from general literature due to a lack of data specific to regions or particular geographic areas.It doesn't consider the characteristics of prevalent breeding systems in a region, such as cattle breeds, animal age, physiological states, productivity levels, and dietary factors (intake and composition).Level 2 utilizes improved emission factors to account for feed and animal characteristics, considering specific parameters dependent on bovine genetics, age, and breeding type.It also factors in the topography of the region under consideration [16].Level 3 is region-specific and relies on extensive research conducted within the particular region.
This study estimated enteric CH4 emissions from selected cattle breeds in Italy using the methodology outlined by the IPCC [16], which operates at Level 2. This approach considers various parameters for each individual animal, including daily weight gain, weight, breeding practices (e.g., stall-feeding, semi-stallfeeding, and grazing), the forage-to-feed ratio characterizing the diet, and, for lactating cows, daily milk quantity and its fat concentration.Employing this methodology allowed for the calculation of enteric CH4 emissions for each selected breed and age category, expressed in grams of CH4 per kilogram of live weight per day.Starting from this value and considering the average weight of animals in each age class, it's possible to estimate the contribution of the representative animal in each calculated class.
In this study, enteric CH4 emissions were estimated for six classes considering age and gender of the animals having an age higher than 6 months.Specifically, the 0-6 months category, for both male and female genders, was not considered because its contribution to enteric CH4 production is either negligible or limited, in some cases, to a few weeks.In these young cattle, milk is the primary source of nutrition, with a limited intake of forages and feeds, especially during the early weeks of life [18].Typically, full rumen development and subsequent weaning occur between five and six months of age, depending on the breed and geographic location of the farm.
The analysis of the morphological and nutritional parameters highlighted as cattle weight and forage/concentrate ratio into the daily diet play a crucial role on the enteric methane emissions.In particular, the data clearly showed that the size of the animal and the age of the cattle have a significant impact on CH4 emissions, reaching the highest value for ages over 24 months for all the analyzed breeds.The weight difference between bulls and cows results in higher emission levels for male cattle, despite cows experiencing pregnancy and lactation periods, that significantly affect the enteric emissions.This trend is closely dependent on the analyzed breed and appears more pronounced for meat specialized breeds, such as Piemontese, Chianina or Marchigiana, whose steers and bulls earlier reach considerable sizes.The feed is another important parameter that deeply influence CH4 emissions.High daily fractions of concentrates (>50% w/w) in the cattle diet are strictly related to a significant increase of the methane produced by enteric fermentation.These findings justify the high methane concentration estimated for the meat specialized breeds (concentrate fraction equal to 45-55% w/w of the daily ratio) during the cattle fattening phase.On the contrary, milk specialized breed and cattle at dual attitude returned lower emissions, due to the reduced size, as well as the highest forage amount in the daily diet (>70% w/w of the total ratio).
The results for individual regions, categorized by geographic area (North, Central, and South Italy), are presented below and closely correlate with the types and sizes of cattle breeds present on average in the considered territory during the monitored time period (2019-2022).
In Figure 1, the data concerning the regions of Northern Italy clearly demonstrate that methane production follows a similar trend across all regions, with higher emissions recorded for the two age classes M>24 and F>24.Male cattle, due to their larger size, emit a greater quantity of greenhouse gases daily compared to their female counterparts (on average +40%).The analysis of individual regions highlights that the highest daily emissions for all classes occur in Piedmont, while South Tyrol produced the lowest amount of greenhouse gas, with an average difference of 16%.The average methane emissions from enteric fermentation of cattle in Northern Italy range from 128.34 to 277.98 g per head per day, which in terms of annual CO2 equivalent yields values ranging from 1.72 to 2.16 tons per head, and an average value equal to 1.89 Mg CO2 equivalent per head.
This observed trend can be justified by the regional composition of cattle and, specifically, by the characteristics of the breeds raised.In particular, higher emissions are recorded in those geographical areas where cattle destined for slaughter are more widespread.These cattle, due to their size, growth rate, and type of diet, typically generate a higher production of enteric CH4.Indeed, in Piedmont and Liguria, there is a significant prevalence of the Piedmontese breed (>40%), while in South Tyrol and Valle d'Aosta, 90% of cattle belong to breeds which have a dual or milk purposes.
Similarly, CH4 emissions from cattle raised in the regions of Central Italy were also estimated, and the results are shown in In general, the main characteristics of cattle raised in Central Italy are a higher average weight (587.26 compared to 521.68 kg) and a greater prevalence of breeds intended for slaughter respect to the cattle of the Northern Italy.In these regions, the Marchigiana and Chianina breeds are the most numerous, significantly influencing the daily emissions of CH4 for all age classes.The average methane emissions from enteric fermentation of cattle in Central Italy range from 137.29 to 319.16 g per head per day, which in terms of annual CO2 equivalent yields values ranging from 1.98 to 2.07 tons per head, and an average value equal to 2.02 Mg CO2 equivalent per head.
Finally, enteric CH4 emissions were also estimated for the regions of Southern and Insular Italy, and the results are shown in Figure 3.The average methane emissions from enteric fermentation of cattle in Central Italy range from 125.74 to 291.04 g per head per day, which in terms of annual CO2 equivalent yields values ranging from 1.70 to 2.04 tons per head, and an average value equal to 1.89 Mg CO2 equivalent per head.

Conclusions
The study provided an estimation of enteric CH4 emissions from cattle in Italy, considering breedspecific parameters.To this purpose, IPCC models were employed, factoring in cattle population, daily weight gain, individual weight, farming system (stable, semi-stable, or pasture), and provided diet.This allowed for the calculation of CH4 emissions expressed in grams of CH4 per kilogram of live weight per day.Specifically, enteric emissions were calculated for 37 pure breed cattle with different aptitudes (milk, meat, or dual-purpose), whose population was significant (>1%) at a national and/or regional level, as well as 22 national and regional Crossbreeds.For each breed, six classes (3 age and 2 gender) were considered, starting from 6 months of age.Bulls showed the highest emissions (44.23-120.43 g CH4 d -1 ), and the total estimated enteric emissions over the 2019-2022 period amounted to 319.21 Gg.Among the regions, Marche showed the highest emissions per head, followed by other regions in Central Italy, where the prevalence of cattle destined for slaughter was the determining factor.On the contrary, Sardinia, Aosta Valley, and South Tyrol, with smaller-sized cattle populations and/or a prevalent focus on milk production, were among the least impactful regions.
Due to the absolute lack of national and regionalized datasets relating to Italian cattle breeding, this research represents a valuable source of specific data.These ones can be useful to develop targeted strategies for mitigating greenhouse gas emissions in specific regions and/or geographical areas.
For instance, regions with higher emissions could benefit from initiatives aimed at optimizing livestock farming practices or transitioning to breeds with lower emission profiles.Conversely, regions with lower emissions can serve as models for sustainable livestock farming practices.It is also crucial to consider broader implications for agricultural policy, such as supporting the selection and adoption of more environmental-friendly cattle breeds or encouraging practices that reduce CH4 production, like choosing an appropriate forage/feed ratio.
In general, this analysis provides a clear picture of how regional factors and cattle breed composition can influence greenhouse gas emissions, offering valuable insights for sustainability efforts in the agricultural sector.
While the systematic analysis of enteric emissions from cattle nationwide is a major factor, it's not the sole one contributing to greenhouse gas production in the cattle farming phase.The analysis of other factors (manure management and forage cultivation) will allow for the creation of comprehensive national and regional datasets capable of effectively estimating the environmental impact of the livestock sector.In future perspectives, the obtained results represent a statistical evaluation that will be confirmed in the field with direct measurements, utilizing innovative instrumental technologies like drone-based monitoring with specialized greenhouse gas sensors.Literature data support this strategy, as enteric CH4 estimates using the IPCC methodology (level 2) have been subsequently validated in the field through measurements employing both established analytical techniques [19,20] and innovative methodologies [21], ensuring a high number of measurements over an extensive and/or rugged area, while simultaneously reducing sampling times.

Fig. 1 .
Fig. 1.Daily enteric CH4 emissions (Et) by age classes and sex in the regions of the Northern Italy.

Figure 2 . 6 Fig. 2 .
Fig. 2. Daily enteric CH4 emissions (Et) by age classes and sex in the regions of the Central Italy.

Fig. 3 .
Fig. 3. Daily enteric CH4 emissions (Et) by age classes and sex in the regions of the Southern and Insular Italy.

Table 1 .
Datasets related to cattle farming found in the main international databases.