## 1 Introduction  
Facing environmental degradation and a decrease in resources, eco-efficiency has been proposed as one of the main tools to promote sustainable development. Eco-efficiency means that a system provides an affordable service while satisfying human needs and reducing the intensity of consumption of inputs and environmental impacts [1]. Consumers are looking for better quality products through environmentally friendly production. Thus, producers are obliged to increase or maintain a level of production while reducing their environmental impact, without compromising either the quality of performance of their processes [2; 3]. Animal husbandry is one of the production processes necessary for world food security [4]; dairy farming, meat poultry, and aquaculture are the most representative. These processes are the world's primary industries that transforms vegetable protein into animal protein. This production process maintains an intensive specialized egg production sector, which consists of separating chicken meat and shelf egg production. The hatching egg sector is not taken into account in this work. Shelf egg production demands food and water inputs due to the biological need for birds and environmental conditions [5; 6]. The energy consumption is a consequence of the farm operations and their level of automation. It has been reported that the most energy-demanding processes in the poultry industry are climate control and lighting, with variable energy consumption of 3 to 4.4 kWh/bird/m\({}^{2}\)/year [7]. The analysis of egg production is gaining importance, which is why studies have been carried out in countries such as Germany, Australia, Canada, the United Kingdom, and Switzerland to create a history of the consumption of energy inputs and materials to estimate the carbon footprint for each kilogram of egg produced according to its housing system (Table 1). Mexico is the world's leading egg consumer, with an estimated annual per capita consumption of 23.3 kg [15]. There is a high demand in the national diet, so the poultry sector has considerable participation in the production of shelf eggs and gross domestic product (GDP). In 2018, the poultry sector represented 63.3% of the country's agricultural activities, of which 28.2% corresponded to the generation of egg products. According to the Mexican National Union of Poultry Producers [15], shelf egg production in 2019 reached \(2.88\times 10^{6}\) t. Expectations for growth in this field are 1.45% per annum [16; 17]. Despite the importance of shelf egg production in Mexico, as it represents 17% of the protein contribution by the livestock sector, there is no national data reporting on environmental assessments. As part of the contribution to food sovereignty, the aim is for agricultural production to be carried out under eco-efficient production schemes. Therefore, it is essential to identify significant environmental issues and opportunities for improvement in this sector. There are tools such as life cycle assessment (LCA) that allow us to estimate potential environmental impacts within a supply chain, and that can integrate improvement strategies into the process [18]. Globally, LCA has been applied to the study of egg production, considering inputs such as diets, electricity, water expenditure, and land-use change [14]. Value stream mapping (VSM) is one of the techniques that can be integrated into LCA. This tool allows visualization of the flow of information in terms of the unitary productivity, efficiency, and reduction of process wastage [19; 20]. The solution obtained through the integration of these instruments reduces waste by 20%-50%, understood as being due to reducing problems in the supply chains of a process [21]. For example, [20] reported a 25% decrease in material consumption, 19% decrease in energy consumption, and 7% decrease in the carbon footprint of an automotive production line in India. To the best of the author's knowledge, there are no reports on the integration of LCA and VSM for shelf egg production.