The commercialization of CRISPR gene-edited pork is advancing rapidly, following the U.S. Food and Drug Administration's approval of gene-edited pigs resistant to Porcine Reproductive and Respiratory Syndrome (PRRS). As these products move closer to market entry, understanding how consumers seek, process, and avoid information about them is critical for developing effective communication strategies. Guided by the Risk Information Seeking and Processing (RISP) model, this study examined factors influencing information seeking, information avoidance, and information processing related to CRISPR-edited pork products among U.S. consumers (n = 2,006). Results show higher information sufficiency thresholds were associated with greater information seeking and lower information avoidance. Information seeking was strongly and positively correlated with systematic processing. Relevant channel beliefs and perceived information gathering capacities were positively associated across communication channels, suggesting the need for integrated communication approaches. Relevant channel beliefs for news media and social media were positively associated with information seeking, while stronger relevant channel beliefs for Extension were associated with lower information seeking. Respondents with some college education reported higher information seeking than those with only a high school diploma or GED, while older adults and individuals with higher education levels reported lower information avoidance. Results also showed that respondents exhibited high intentions to seek information and low tendencies to avoid information, suggesting openness to learning about CRISPR-edited pork. Participants also reported engaging more in systematic processing than heuristic processing, indicating a preference for careful and analytical evaluation of information. Findings highlight the importance of audience segmentation, multi-channel communication strategies, and evidence-based messaging to support informed public engagement with CRISPR-edited food technologies.

This study evaluated the effects of air nanobubbles and conventional aeration on emissions of methane (CH4), nitrous oxide (N2O), carbon dioxide (CO2), and ammonia (NH3) from dairy lagoon wastewater. Wastewater collected from a commercial dairy in California was treated in duplicate drum systems under nanobubbles aeration, conventional aeration, and control (no aeration) over 31 days. Nanobubbles aeration significantly reduced CH4 emissions rates by 66.7% compared with the control. However, the reduction was not statistically significant relative to conventional aeration, although the average reduction was 29.4%, likely due to limited replication in this experiment. Nanobubbles aeration also significantly lowered NH3 emissions rates relative to both treatments. However, nanobubbles aeration and the associated increase in temperature led to significantly higher N2O and CO2 emissions rates, particularly during the initial phase of treatment. Across treatments, N2O became the dominant contributor to global warming potential (GWP100), resulting in higher net climate impacts for nanobubbles (2265.34 g CO2-eq/m3) and conventional aeration (1445.10 mg CO2-eq/m3) compared with the control (418.00 CO2-eq/m3). Changes in nitrogen dynamics indicated rapid nitrification under aerated conditions, with substantial decreases in ammonium and accumulation of nitrate, suggesting limited denitrification likely due to low organic carbon availability. Overall, under this controlled study, air nanobubbles aeration effectively reduced CH4 and NH3 emissions but shifted nitrogen losses toward N2O, resulting in a higher net climate impact. These findings highlight the importance of evaluating dairy manure and wastewater management strategies using full greenhouse gas accounting to avoid unintended tradeoffs.

Emissions of methane (CH4), ammonia (NH3), nitrous oxide (N2O), and hydrogen sulfide (H2S) were measured from a settling basin and lagoon before and after installation of a covered lagoon anaerobic digester at a commercial dairy in California. Three seasonal measurement campaigns were conducted pre-digester (2021-2022) and three post-digester (2025). A floating wind tunnel was used to quantify surface fluxes from both emission sources. Post-digester installation, the average CH4 emissions from the settling basin decreased by 39.8%, and H2S emissions decreased by 82.5%. In contrast, NH3 emissions increased, likely due to enhanced mineralization of organic nitrogen to ammonium during anaerobic digestion. No consistent trend was observed for N2O emissions. To ensure a consistent assessment of the digester's impact on methane emissions from manure storage in the settling basin and lagoon, emissions were modeled using the California Air Resources Board Dairy Digester Research and Development Program (CARB-DDRDP) calculator. The amounts of volatile solids loaded to manure storage (i.e., the settling basin and lagoon) were estimated for both pre- and post-digester installation periods and used as inputs to the model. Modeling indicated an annual reduction of 52.5% in average CH4 emissions from manure storage following digester installation. These results confirm substantial methane mitigation benefits under commercial conditions while highlighting nitrogen-related emission tradeoffs.

The objective of this study was to evaluate the effect of air nanobubbles technology on the emissions of methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O), and ammonia (NH3) from dairy manure collected after a settling basin on a commercial dairy farm in California. Manure was stored in stainless steel drums for one month under ambient conditions. During storage, manure was treated with air nanobubbles and conventional aeration, and compared with the control (i.e., without aeration). Duplicate drums were tested under each condition. Each drum was covered with a flux chamber to collect gas samples that were continuously analysed for different gases. Results showed that nanobubbles treatment achieved significantly lower CH4 and NH3 emission rates than conventional aeration treatment and control. However, it significantly increased the emissions of CO2 and N2O. The reduction of CH4 emission rates by nanobubbles treatment was 97.9% and 97.5% as compared to control and conventional aeration treatment, respectively, while the emissions of N2O increased by 99 and 21.5 times, respectively. The decreased emissions of CH4 by air nanobubbles treatment may be due to the greater oxidation-reduction potential (ORP) and Dissolved Oxygen (DO) in nanobubbles treatment than in conventional aeration treatment and control. The increased CO2 and N2O emissions could be attributed to the confounding effects of enhanced oxygen transfer and elevated temperatures associated with the nanobubble treatment. Compared with conventional aeration treatment and control, there was a substantial decrease in ammonium concentrations and an increase in nitrate concentrations in manure treated with air nanobubbles; nitrate concentrations substantially increased.

The effects of pyrolysis temperature (400–500 °C) and time (30–90 min) on the yield and chemical and physical properties of biochar produced from almond and pistachio shells were studied using a fixed-bed pyrolyzer. Thermogravimetric analysis (TGA) was employed to characterize the kinetics of thermal degradation of the shells. This study compared the thermal behavior observed by TGA with biochar yields obtained from a fixed-bed pyrolyzer, providing insight into the agreement between laboratory-scale thermogravimetric measurements and fixed-bed pyrolysis performance. Fourier transform infrared spectroscopy (FTIR) was performed for each type of biochar. Results showed higher biochar yields from almond shells (35.0–41.3% dry basis) than from pistachio shells (26.8–36.7% dry basis). Shell type, pyrolysis temperature, pyrolysis time, and their interactions had significant effects on biochar yield. The Derivative Thermogravimetric (DTG) profiles showed distinct thermal decomposition patterns for almond and pistachio shells. Almond shells exhibited broader decomposition regions, while pistachio shells showed more distinct decomposition stages. FTIR analysis of both shell biochars indicated reduced O–H and oxygen-containing groups with increasing pyrolysis temperature and residence time, suggesting greater carbonization, aromatic enrichment, and formation of carbonaceous compounds. Greater biochar yields were obtained from the fixed-bed pyrolyzer than from TGA. A first-order kinetics model adequately described the thermal decomposition of both shell types. Apparent activation energies were 41.83–44.99 kJ mole−1 for almond shells and 58.19–63.58 kJ mole−1 for pistachio shells. Model validation showed a good agreement between the experimental and predicted conversion values. The results provide a basis for evaluating the potential of TGA-derived thermal behavior to inform biochar production conditions in fixed-bed pyrolysis.

Several metrics have been developed for combining the warming effects of various GHG. The metric used can affect the life cycle assessment and comparison of dairy production systems due to the weighting placed on long- versus short-lived gases in the atmosphere. Global warming potential (GWP) with a time horizon of 100 years (GWP-100) has become the standard, but metrics are also available for other time horizons. Metrics for 20-, 100-, and 500-year horizons gave average farm-gate emission intensities of 2.08, 0.98, and 0.50 kg of CO2 equivalents per kilogram of fat- and protein-corrected milk produced for current US dairy farms. Compared with the use of GWP metrics, which represent energy absorption, use of global temperature change potential (GTP), combined global temperature change potential (CGTP), or global warming potential star (GWP*) reduced the warming effect of methane relative to other GHG. These metrics representing temperature change reduced the warming potential of US dairy farms by 17% to 49% compared with the use of GWP-100. The metrics used also affected the comparison of individual production systems, providing different life cycle assessments of management practices. Use of GWP-100 metrics indicated that warming from GHG emissions of US dairy farms increased 11 % to 15% between 1971 and 2020, whereas the use of GTP, CGTP, and GWP* metrics showed little or no effect on global temperature change over the 50-year period. Use of GWP-100 metrics indicated that GHG emissions related to milk production on dairy farms represented 1.6% of all US GHG emissions in 2020 whereas use of other metrics ranged from 0.9% to 1.8%. Although all approaches for representing the integrated warming impact of GHG have benefits and challenges, approaches such as CGTP and GWP*, which account for the rate of methane emission relative to the oxidation rate in the atmosphere, provide a more process-based assessment of the long-term impact of dairy farms on global temperature and perhaps offer a more scientifically sound approach for assessing strategies to mitigate the warming effect of dairy farms.

As highlighted in the Global Methane Pledge, reducing methane emissions has been identified as a core strategy and the best short-term solution against atmospheric warming. Well before the release of the United Nations Environmental Program's Global Methane Assessment in 2021, California had set aggressive targets for reducing methane 40% below 2013 levels by 2030 with the passing of SB 1383 in 2016. All methane sources including those from the dairy and other livestock industries are required to reduce emissions. Dairy comprises approximately 45% and other livestock make up 10% of the total anthropogenic annual methane emitted in California. This analysis focuses on California's efforts to reduce dairy methane emissions and the progress it has made toward the target over the past 7+ years. The California dairy industry is on track to achieve these emission reduction targets based on falling cow numbers, constructing anaerobic digesters and manure management infrastructure, and the potential to implement feed additives for enteric methane reduction. Looking into the future, this case study highlights the additional methane emission reduction efforts that are underway that will enable the California dairy industry to achieve its full contribution toward the 40% reduction goal by 2030.

Tannins are plant secondary metabolites that bind organic carbon (C) and nitrogen (N), potentially altering substrate bioavailability for enteric fermentation in ruminants. This interaction may reduce greenhouse gas (GHG) emissions and influence nitrogen partitioning. Given tannins' resistance to ruminal degradation and persistence through the gastrointestinal tract, this study investigated the effects of a tannin-based feed additive on fecal microbial diversity, fecal chemical composition, and GHG emissions. Twenty-four early- to mid-lactation dairy cows were randomized to receive either a tannin-based feed additive (TRT; containing condensed and hydrolyzable tannins from Schinopsis quebracho-colorado [Schltdl.]) or a control diet (CON) for 64 days. Cows were blocked by parity, dry matter intake, milk yield, body weight, and days in milk. Fecal samples were collected on days 0, 16, 32, and 64 and analyzed using 16S rRNA gene amplicon sequencing. Fecal C, N, and indole-3-lactate were measured, and GHG emissions (N2O, CH4, CO2) were assessed via 14-day laboratory incubation. A total of 1,538 amplicon sequence variants were identified, with Firmicutes as the dominant phylum. Fecal phylogenetic diversity showed a significant treatment × day interaction (p < 0.01), with TRT cows exhibiting reduced microbial diversity from day 16 to 64. Fecal C and N concentrations were significantly lower (p < 0.01) in TRT cows on day 16, while indole-3-lactate levels were higher on day 64 (p = 0.02). GHG emissions did not differ significantly between treatments. The tannin-based feed additive influenced fecal microbial community structure and select chemical parameters but did not significantly affect GHG emissions from feces. These findings suggest that dietary tannins may modulate gut microbial ecology with minimal impact on downstream manure-related emissions.

Feed additives in beef cattle diets can reduce enteric greenhouse gas (GHG) emissions. However, subsequent effects on soil carbon (C) and nitrogen (N) after land application of manure from additive-fed animals remain largely unknown. In this study, manure (mainly feces) from beef cattle fed either an un-supplemented diet (UN) or a diet containing one of two essential oil-based feed additives, Agolin® (AG; 1 g/steer/day) or Mootral® (MT; 23.5 g/steer/day), were collected and applied to soils with different textures (clay or sandy loam). The soil-feces mixtures were incubated in a completely randomized block design at two moisture levels, 50 % and 90 % water holding capacity (WHC). The AG treatment, versus MT and UN, yielded lower cumulative mineralized N (Nmin; p < 0.01) in clay at 90 % WHC, but not at 50 % WHC. Similarly, AG, versus MT and UN, had lower carbon dioxide (CO2) emissions in clay at 90 % WHC (p < 0.01), but higher emissions in sandy loam at 90 % WHC (p < 0.01). There were no differences in CO2 among treatments at 50 % WHC. Nitrous oxide (N2O) emissions were only affected by soil type (p = 0.01) regardless of soil moisture or feed additives. Methane (CH4) emissions were affected by soil moisture (p = 0.03) and the interaction soil × moisture × manure (p < 0.01), however the feed additives had no effect. These findings indicate that the feed additives tested may affect C dynamics and Nmin in a soil and/or moisture-dependent manner.

Abstract Dairy manure management is responsible for a significant amount of greenhouse gas emissions (GHG) in California. Aside from redesigning infrastructure to adopt alternative manure management systems, there are few options available to farmers to mitigate emissions without substantial financial investment. Calcium cyanamide, a new manure additive, showed significant reductions in GHG emissions when applied to fresh dairy cow slurry, but has not been tested on dairy lagoon water. The aim of the present study was to investigate the effects of calcium cyanamide on GHG and NH3 emissions and the microbiome of dairy lagoon water. Lagoon water was collected from a commercial dairy, and distributed into 12 stainless steel barrels. Three treatments (n = 4/treatment) of different doses of calcium cyanamide were tested: high (LW-HD; 1 kg/m3 lagoon water), low (LW-LD; 0.5 kg/m3 lagoon water), and control with no calcium cyanamide (LW-CONT; n = 4). Each barrel was sampled over two, 14-d periods, staggered to four barrels at a time, using OdoFlux chambers to monitor emissions for carbon dioxide (CO2,), methane (CH4), nitrous oxide (N2O), and ammonia (NH3). Treatments LW-LD and LW-HD contained significantly more total solids, total nitrogen and total carbon compared with LW-CONT. There was also a significantly greater concentration of acetic acid in LW-LD and LW-HD treatments compared with LW-CONT. CO2 emissions in LW-LD and LW-HD were 2.96% and 12.03% less than LW-CONT. CH4 emissions in LW-LD and LW-HD were 80.9% and 85.13% less compared with LW-CONT. N2O emissions in LW-LD and LW-HD were 81.1% and 82.66% less than LW-CONT. However, NH3 fluxes were greater in LW-LD and LW-HD compared with LW-CONT by 65.26% and 65.73%, respectively. The microbiome of the lagoon water was also affected, with reductions in relative abundance of the Proteobacteria phylum responsible for nitrification in LW-LD and LW-HD and increases in the Firmicutes phylum containing acetogenic bacteria. Calcium cyanamide could inhibit methanogenesis by increasing acetogenic bacteria that compete with methanogens for fermentation substrates. Further research is needed to investigate the efficacy of calcium cyanamide in a commercial lagoon setting.

Abstract Meat and dairy will continue to be an essential part of diets around the world, but as demand increases so does pressure to reduce the environmental impact of farming. There is no single solution that will allow the global community to meet demand and improve sustainability in our food system. We will need a toolkit of solutions to meet the needs of producers in various regions and production systems.

The increase in average global temperatures presents a challenge for the beef industry, especially in the feedlot sector where heat stress is a major animal welfare and economic concern. To combat this, shade stands out as one of the most practical methods to mitigate heat stress in feedlot cattle. An experiment was conducted as a completely randomized design with Bos indicus bulls (n = 1,560) with initial body weights (BW) of 287 kg. Three shade structure types were used to investigate the effects of different heat stress mitigation methods on cattle growth performance, environmental, and economic outcomes using live animal data, and a partial lifecycle assessment (LCA) using the Integrated Farm System Model (IFSM). The live animal portion of the experiment was done once a year over a 2-yr period with three pen replications per treatment per year (n = 6 per treatment). Four shade structures used were: conventional shade (SC; steel shade 1.8 m2 of shade/animal), double conventional shade (DS; steel shade 3.6 m2 of shade/animal), dome structures without fans (DSA; 8.5 m2/animal with 98% solar radiation blocked), and domes with fans (DCA; three large sized low-speed fans). Each pen held 65 bulls in an area of 570 m2. Live animal data were analyzed as a completely randomized design using the GLM procedure of SAS (version 9.4) with shade type as fixed effect, pen as the experimental unit, and repetition (year) considered a random effect. Cattle housed under DCA had 22 kg and 20 kg heavier final body BW (P < 0.05) compared with those housed under SC and DS, respectively. Final BW of DCA and DSA cattle were similar (P > 0.10). Average daily gain, feed efficiency, and hot carcass weight (HCW) were greater (P < 0.05) for cattle housed under DCA compared with the rest of the shade types. Dry matter intake was not affected (P > 0.10). When treatment results were extrapolated to the annual feedlot turnover of 209,700 animals, cattle in DSA and DCA versus SC and DS had 3 to 8 % reductions in greenhouse gas and ammonia emissions intensities. Compared with SC, DCA increased profitability by $29.66/animal, followed by DSA and DS with profit increases of $5.79 and $8.90/animal, respectively. Overall, the implementation of advanced shade structures improved cattle performance and profitability while reducing the environmental impact of beef production.

The increase in average global temperatures presents a challenge for the beef industry, especially in the feedlot sector where heat stress is a major animal welfare and economic concern. Shade is one of the most practical methods to mitigate heat stress in feedlot cattle. An experiment was conducted as a completely randomized design with 1 560 Bos indicus bulls (initial BW=287 kg) where three shade structure types were used to investigate the effects of different heat stress mitigation methods on cattle growth performance, environmental, and economic outcomes using live animal data, and a partial lifecycle assessment using the Integrated Farm System Model. The live animal portion of the experiment was done once a year over a 2-year period with three pen replications per treatment per year (n = 6 per treatment). Four shade structures used were conventional shade (SC; steel shade 1.8 m(2) of shade/animal), double conventional shade (DS; steel shade 3.6 m(2) of shade/animal), dome structures without fans (DSA; 8.5 m(2)/animal with 98% solar radiation blocked), and domes with fans (DCA; DSA plus three large sized low-speed fans). Each pen held 65 bulls in an area of 570 m(2). Live animal data were analyzed as a completely randomized design using the GLM procedure of SAS (version 9.4) with shade type as fixed effect, pen as the experimental unit, and repetition (year) considered a random effect. Cattle housed under DCA had 22 and 20 kg heavier final body BW (P < 0.05) compared to those housed under SC and DS, respectively. Final BW of DCA and DSA cattle were similar (P > 0.05). Average daily gain, feed efficiency, and hot carcass weight were greater (P < 0.05) for cattle housed under DCA compared to the rest of the shade types. Dry matter intake was not affected (P > 0.05). When treatment results were extrapolated to the annual feedlot turnover of 209,700 animals, cattle in DSA and DCA versus SC and DS had 3-8% reductions in greenhouse gas and ammonia emission intensities. Compared to SC, DCA increased profitability by $29.66/animal, followed by DSA and DS with profit increases of $5.79 and $8.90/animal, respectively. Overall, the implementation of advanced shade structures improved cattle performance and profitability while reducing the environmental impact of beef production.

Abstract Black Angus steers [n = 112; body weight (BW) = 401 ± 3.6 kg] were used in a randomized incomplete block design to evaluate the effects of 3 rumen available protein to microbial crude protein ratios (RAP:MCP) on growth performance, and gaseous emissions from feedlot steers. Steers were blocked by initial BW and randomly assigned to 1 of 3 treatment rations. Diets were fed rations either Deficient (-150 gּ animal-1ּ d-1; DEF), Balanced (0 gּ animal-1ּ d-1; BAL), or Excess (+150 gּ animal-1ּ d-1; EXS) in RAP: MCP. Steers were allocated and housed in cattle pen enclosures (CPE), and treatment diets were delivered daily as a total mixed ration. The present study consisted of two 42-d periods. Refusals were collected weekly and BW every 14 d. Gas measurements were obtained daily in sequential order from all CPE. Data were analyzed with R statistical software (4.2.3). The linear mixed effect model procedure within the “lme4” package was used with CPE as the experimental unit, treatment and week as fixed effects, and block and period as random effects. A contrast coefficient matrix was constructed to test for linear and quadratic effects. Initial, intermediary and final BW were not different for steers receiving the varying RAP:MCP (P ≥ 0.239). A treatment effect (P = 0.004) was observed for mean dry matter intake (DMI) where EXS steers consumed 0.46 kg more DM compared with BAL steers, but DEF steers had similar DMI to those fed EXS and BAL (P = 0.189). Average daily gain (ADG) was only affected by treatment (P = 0.007) on d 0 to 14 where steers receiving DEF gained 0.6 kg more than those fed BAL (P = 0.010), but those fed EXS had similar ADG. Similar to ADG, gain to feed (G:F) was affected by treatment (P = 0.012) only during d 0 to 14. Mean CH4 production from steers fed DEF and EXS were 20% and 13% greater (P = 0.010) compared with those fed BAL, respectively; however, CH4 from EXS vs. DEF steers was not different (P = 0.149). Mean cumulative NH3 emissions increased linearly by treatment with EXS steers emitting up to 52% more NH3 compared with those receiving DEF (P < 0.001). Similarly, EXS steers had increased SO2 emissions by up to 44% compared with those fed DEF (P < 0.001). Emissions of CO2, N2O, and H2S were similar (P > 0.100). The manipulation of RAP:MCP in the diets of feedlot steers can drastically reduce NH3 emissions without affecting growth performance and may be a valuable tool to reduce air pollution from beef production systems.

Manure management emits large quantities of greenhouse gases (GHG) in California. Eminex®, a manure additive, previously demonstrated significant GHG reductions in slurry. However, it has not been tested in lagoon wastewater. The aim of the present study was to investigate the effects of Eminex® on GHG, ammonia (NH3), and ethanol (EtOH) emissions from fresh dairy slurry and dairy lagoon wastewater. Both manures received the following treatments: high (1.0 kg Eminex®/m3 manure), low (0.5 kg Eminex®/m3 manure). Experiments were conducted in four replicates with an untreated manure control. The physical characteristics of the manure were determined during the monitoring periods of emissions: 7 days for slurry and 28 days for lagoon wastewater. All slurry emissions, except for N2O, declined over time (p < 0.05). Lagoon wastewater total N increased with treatment (p < 0.05) possibly due to the urea provided by Eminex®. Most lagoon wastewater emissions also decreased over time (p < 0.05). However, Eminex®, compared to control, increased lagoon wastewater NH3 volatilization (p < 0.05). With improvements to manure composition through increasing N content, as well as reductions in emissions, Eminex® is a promising tool to mitigate the negative environmental impacts of manure management.

California is the leading dairy state in the United States. The total sale of milk and its products represents about $6.3 billion annually out of the $50 billion generated from all agricultural production in the state. However, methane emissions from dairy manure and enteric fermentation represented nearly half of all annual methane emissions in California, with dairy manure accounting for 25%, and enteric fermentation for 20%. Methane emissions originating from manure are produced primarily from anaerobic settling basins and lagoons, which are the most common manure storage systems in the state. To achieve sustainability on dairy farms and to comply with state regulations for air and climate pollutants, dairy farms have implemented technologies such as anaerobic digestion and alternative manure management technologies. In addition, governmental incentive programs have been deployed to partially fund these technologies for eligible dairies in the state. The present article reviews the design and operations, effectiveness, and economics of the most common technologies employed in Californian dairies in reducing methane emissions. The technologies studied include anaerobic digesters, mechanical separators, compost-bedded pack barns, manure vacuuming followed by drying, and weeping walls. The current status and estimated effectiveness of government incentive programs are reviewed and recommendations for improvements presented. Finally, future trends and research needs for mitigating the emissions in Californian dairies are identified.

Between 2010 and 2020, an average of 36,037 hectares of grassland burned in wildfires in California each year, emitting greenhouse gasses (GHGs) and particulate matter (PM). These emissions impact climate and human health. Cattle grazing removes herbaceous fuel through the consumption of forage; however, ruminant digestion also emits GHGs. The purpose of this study was to examine the GHG and PM impact of livestock grazing in grasslands that go on to burn. We used Monte Carlo simulation to determine whether forage consumption by livestock led to reductions in grassland wildfire emissions and whether these reductions outweighed the emissions from the digestion of that forage. We estimate that between 2010 and 2020, an average of 11,590 metric tons (MT) of herbaceous fuel were removed by cattle annually from grasslands in California that went on to burn. This resulted in annual wildfire emission reductions ranging between 0.001 and 0.025 million metric tons (MMT) of CO2 equivalents (CO2e) and between 11 and 314 MT of PM2.5; a small fraction of total GHG and PM emissions from wildfires in California. We also evaluated the change in emissions if burned grasslands in California’s Central and North Coast regions—where removing grazing can lead to the encroachment of shrubs into grasslands—were instead shrublands. If the grasslands that burned in these regions in 2020 had instead been shrublands, we estimate that as much as 0.90 MMT more CO2e and 8448 MT more PM2.5 would have been emitted by wildfires, highlighting the long-term implications of livestock grazing.

Introduction Carbon dioxide (CO 2 ) and methane (CH 4 ) are two of the primary greenhouse gases (GHG) responsible for global warming. The “stock gas” CO 2 accumulates in the atmosphere even if rates of CO 2 emission decline. In contrast, the “flow gas” CH 4 has an e-folding time of about 12 years and is removed from the atmosphere in a relatively short period of time. The climate impacts of cumulative pollutants such as CO 2 and short-lived climate pollutants (SLCP) such as CH 4 are often compared using Global Warming Potential (GWP), a metric that converts non-CO 2 GHG into CO 2 -equivalent emissions. However, GWP has been criticized for overestimating the heating effects of declining SLCP emissions and conversely underestimating the heating impact of increasing SLCP emissions. Accurate quantification of the temperature effects of different CH 4 emissions scenarios is particularly important to fully understanding the climate impacts of animal agriculture, whose GHG emissions are dominated by CH 4 . Methods A modified GWP metric known as Global Warming Potential Star (GWP * ) has been developed to directly quantify the relationship between SLCP emissions and temperature change, which GWP cannot do. In this California dairy sector case study, we contrasted GWP- versus GWP * -based estimates of historical warming dynamics of enteric and manure CH 4 from lactating dairy cattle. We predicted future dairy CH 4 emissions under business-as-usual and reduction scenarios and modeled the warming effects of these various emission scenarios. Results We found that average CO 2 warming equivalent emissions given by GWP * were greater than those given by GWP under increasing annual CH 4 emissions rates, but were lower under decreasing CH 4 emissions rates. We also found that cumulative CO 2 warming equivalent emissions given by GWP * matched modeled warming driven by decreasing CH 4 emissions more accurately than those given by GWP. Discussion These results suggest that GWP * may provide a more accurate tool for quantifying SLCP emissions in temperature goal and emissions reduction-specific policy contexts.

Ruminant livestock is a large contributor of CH4 emissions globally. Assessing how this CH4 and other greenhouse gases (GHG) from livestock contribute to anthropogenic climate change is key to understanding their role in achieving any temperature targets. The climate impacts of livestock, as well as other sectors or products/services, are generally expressed as CO2-equivalents using 100-year Global Warming Potentials (GWP100). However, the GWP100 cannot be used to translate emission pathways of short-lived climate pollutants (SLCPs) emissions to their temperature outcomes. A key limitation of handling long- and short-lived gases in the same manner is revealed in the context of any potential temperature stabilisation goals: to achieve this outcome, emissions of long-lived gases must decline to net-zero, but this is not the case for SLCPs. A recent alternative metric, GWP* (so-called 'GWP-star'), has been proposed to overcome these concerns. GWP* allows for simple appraisals of warming over time for emission series of different GHGs that may not be obvious if using pulse-emission metrics (i.e. GWP100). In this article, we explore some of the strengths and limitations of GWP* for reporting the contribution of ruminant livestock systems to global temperature change. A number of case studies are used to illustrate the potential use of the GWP* metric to, for example, understand the current contribution of different ruminant livestock production systems to global warming, appraise how different production systems or mitigations compare (having a temporal element), and seeing how possible emission pathways driven by changes in production, emissions intensity and gas composition show different impacts over time. We suggest that for some contexts, particularly if trying to directly infer contributions to additional warming, GWP* or similar approaches can provide important insight that would not be gained from conventional GWP100 reporting.

Enteric methane is a major source of greenhouse gas emissions from milk production systems. Two organizations based in the United States, the Foundation for Food and Agriculture Research and the Dairy Research Institute, have developed a collaborative program to align resources and fund projects to identify, develop, and validate new and existing mitigation options for enteric methane emissions from dairy and beef cattle. This collaborative program is called the Greener Cattle Initiative. The program will develop requests for proposals and award grants on projects that address challenges within, but not limited, to the following research areas: dairy and beef cattle nutrition, rumen microbiome, dairy and beef cattle genetics, sensing and data technology for enteric methane measurement and prediction, and socioeconomic analysis of enteric methane mitigation practices. The program is structured as a consortium with closed participation and a flat governance collaboration model. The Greener Cattle Initiative program will continue incorporating participants from the food and agriculture industry, commodity groups, and nonprofit organizations who share common objectives and contribute in-kind and matching funds to the program, up to a total of 10 organizations. Research findings will be communicated broadly, after a waiting period for exclusive access to program participants, to create shared knowledge on enteric methane mitigation. The Greener Cattle Initiative is expected to award up to $5 million in research grant funding in a 5-year period, which will contribute to advancing the voluntary greenhouse gas reduction goals established by both the United States and global dairy sectors.