Abstract
Livestock production has a major impact on the environment. Choosing a more environmentally-friendly livestock product in a diet can mitigate environmental impact. The objective of this research was to compare assessments of the environmental impact of livestock products. Twenty-five peer-reviewed studies were found that assessed the impact of production of pork, chicken, beef, milk, and eggs using life cycle analysis (LCA). Only 16 of these studies were reviewed, based on five criteria: study from an OECD (Organization for Economic Cooperation and Development) country, non-organic production, type of LCA methodology, allocation method used, and definition of system boundary. LCA results of these 16 studies were expressed in three ways: per kg product, per kg protein, and per kg of average daily intake of each product for an OECD country. The review yielded a consistent ranging of results for use of land and energy, and for climate change. No clear pattern was found, however, for eutrophication and acidification. Production of 1 kg of beef used most land and energy, and had highest global warming potential (GWP), followed by production of 1 kg of pork, chicken, eggs, and milk. Differences in environmental impact among pork, chicken, and beef can be explained mainly by 3 factors: differences in feed efficiency, differences in enteric CH4 emission between monogastric animals and ruminants, and differences in reproduction rates. The impact of production of 1 kg of meat (pork, chicken, beef) was high compared with production of 1 kg of milk and eggs because of the relatively high water content of milk and eggs. Production of 1 kg of beef protein also had the highest impact, followed by pork protein, whereas chicken protein had the lowest impact. This result also explained why consumption of beef was responsible for the largest part of the land use and GWP in an average OECD diet. This review did not show consistent differences in environmental impact per kg protein in milk, pork, chicken and eggs. Only one study compared environmental impact of meat versus milk and eggs. Conclusions regarding impact of pork or chicken versus impact of milk or eggs require additional comparative studies and further harmonization of LCA methodology. Interpretation of current LCA results for livestock products, moreover, is hindered because results do not include environmental consequences of competition for land between humans and animals, and consequences of land-use changes. We recommend, therefore, to include these consequences in future LCAs of livestock products. © 2009 Elsevier B.V. All rights reserved.
Generated Summary
This review article compares the environmental impacts of livestock products, utilizing life cycle assessment (LCA) as the primary methodology. The study examines 16 peer-reviewed studies from OECD countries, focusing on the production of pork, chicken, beef, milk, and eggs. The research employed a cradle-to-farm-gate approach for the LCA, expressing results per kg of product, per kg of protein, and per average daily intake (ADI) for an OECD country. The objective was to evaluate and compare the environmental impacts of different livestock products to identify more environmentally friendly choices within a diet. The study’s scope was limited to attributional LCAs and economic allocation methods. The review aimed to provide a scientific overview of the LCA results for livestock products and to identify any consistent patterns in their environmental impacts, particularly concerning land use, energy consumption, climate change, acidification, and eutrophication. The research contributes to the ongoing discussion about the environmental effects of food production and aims to offer insights into mitigating these impacts through informed dietary choices.
Key Findings & Statistics
- Land Use: Production of 1 kg of pork required 8.9–12.1 m²; 1 kg of chicken 8.1–9.9 m²; and 1 kg of beef required 27-49 m² of land. Production of 1 kg of milk required 1.1-2.0 m², and 1 kg of eggs required 4.5-6.2 m². When expressed per kg of protein, milk production required 33–59 m², pork 47–64 m², chicken 42–52 m², eggs 35–48 m², and beef 144–258 m².
- Energy Use: Production of 1 kg of pork used 18-45 MJ; chicken 15-29 MJ; and beef 34 to 52 MJ. When expressed in terms of protein, production of milk required 37–144 MJ/kg, pork 95–236 MJ/kg, chicken 80–152 MJ/kg, eggs 87–107 MJ/kg, and beef production required 177–273 MJ/kg.
- GWP (Global Warming Potential): Production of 1 kg of pork resulted in 3.9–10 kg CO2-e; chicken 3.7–6.9 kg CO2-e, and beef 14 to 32 kg CO2-e. In terms of protein, production of milk had a range of 24-38 CO2-e/kg, pork 21-53 CO2-e/kg, chicken 18-36 CO2-e/kg, and eggs 30-38 CO2-e/kg, whereas production of beef resulted in a GWP of 75-170 CO2-e/kg.
- Acidification Potential (AP): The AP of pork varied from 43 to 741 g SO2/kg.
- Average Daily Intake (ADI): Consumption of beef had the highest land use (1.65–2.96 m²); followed by consumption of milk (0.62–1.1 m²), chicken (0.60–0.73 m²) and pork (0.73–0.99 m²); whereas consumption of eggs (0.16–0.22 m²) resulted in the lowest land use.
Other Important Findings
- The review identified a consistent ranging of results for use of land and energy and for climate change. No clear pattern was found, however, for eutrophication and acidification.
- Production of 1 kg of beef used most land and energy, and had the highest global warming potential (GWP).
- Differences in environmental impact among pork, chicken, and beef were mainly explained by feed efficiency, enteric CH4 emissions, and reproduction rates.
- The environmental impact per kg of meat (pork, chicken, beef) was high compared with milk and eggs.
- The largest part of land use and GWP in an average OECD diet was due to beef consumption.
- The study found that in terms of protein, chicken protein had the lowest impact.
- The review did not show consistent differences in environmental impact per kg protein in milk, pork, chicken, and eggs.
Limitations Noted in the Document
- The study acknowledges the limitations of not including environmental consequences of competition for land between humans and animals.
- It also notes that the environmental consequences of land-use changes were not incorporated.
- The interpretation of current LCA results for livestock products is hindered because the results do not include environmental consequences of competition for land between humans and animals and consequences of land-use changes.
- The review is limited to attributional LCAs and economic allocation methods.
- The review did not show consistent differences in environmental impact per kg protein in milk, pork, chicken, and eggs.
- The study is limited to comparing the environmental impact of livestock products and does not assess the impact of fish production.
- The studies did not consider the impact of post-farm-gate stages in as much detail as those involved in production until the farm gate.
Conclusion
The review of existing LCA studies on livestock products reveals significant environmental impacts associated with their production, particularly regarding land use, energy consumption, and climate change. Beef production consistently demonstrates the highest environmental footprint across these categories, followed by pork and chicken. The relatively lower impacts of milk and eggs, especially on a per-kg basis, highlight potential benefits of shifting dietary choices. The authors emphasize that the differences in environmental impact among pork, chicken, and beef are primarily influenced by factors such as feed efficiency, methane emissions from ruminants, and animal reproduction rates. The study also highlights that the current LCA results may not fully capture the complexities of livestock production. A significant limitation is the exclusion of environmental consequences related to competition for land between humans and animals, and the impacts of land-use changes. The authors recommend incorporating these factors into future LCAs to provide a more comprehensive and accurate assessment. The comparison of the environmental impacts of livestock products necessitates further harmonization of LCA methodologies and additional comparative studies, particularly for a deeper understanding of the differences in impact per kg of protein across milk, pork, chicken, and eggs. The findings underscore the need for a broader assessment framework that considers the complete life cycle of livestock products and their interactions with the broader food system. The ultimate goal is to facilitate informed dietary choices that mitigate the environmental impact of livestock production.