Decreasing the Environmental Impact in an Egg-Producing Farm through the Application of LCA and Lean Tools

Reviewer 1

Comments

Action

 We thank the reviewer for this comment.

The reference Wilkinson, J. (2011). Re-defining efficiency of feed use by livestock. Animal, 5(7), 1014-1022. doi:10.1017/S175173111100005X was added.

Before:

Poultry farming is one of the production processes necessary for world food security

Now the line reads in section 1:

Animal husbandry is one of the production processes necessary for world food security (Wilkinson, 2011); dairy farming, meat, poultry and aquaculture, being the most representative.

 We thank the reviewer for this comment.

“The aim of this research” was changed to “The research aimed”.

 We thank the reviewer for this comment.

“5.58 kg CO2 eq/kg” was corrected to “5.58 kg CO2 eq/kg produced egg”

 We thank the reviewer for this comment.

A comma was added after focus.

 We thank the reviewer for this comment.

“This” was substituted by “The implementation of the eco-efficient scheme…”

 We thank the reviewer for this comment.

To clarify the environmental economic concept of externality, this sentence was added:

“From the environmental economic point of view, that externalities, that is, those environmental damages which were not considered initially as part of the production cost, now they were included, it is, they are internalized”.

 We thank the reviewer for this comment.

Not really, that strong affirmation was deleted, and changed to “points out to a possible path…”

 We thank the reviewer for this comment.

The keywords were “Life cycle assessment; value stream mapping; egg-production; lean manufacturing; eco-efficiency; poultry; laying hens”

Now, only “Life cycle assessment; value stream mapping; egg-production; eco-efficiency” were used.

 We thank the reviewer for this comment

The sentence was rewritten, now it reads:

“Facing environmental degradation and a decrease in resources, eco-efficiency has been proposed as one of the main tools to promote sustainable development”.

 We thank the reviewer for this comment.

The in-text citation was deleted because Table 1 shows up the citation according to the countries.

We thank the reviewer for this comment.

The parentheses of the references have been removed.

 We thank the reviewer for this comment.

“in other words,” has been deleted

 We thank the reviewer for this comment.

The produced amount was updated to the year 2019.

In the original document, the manuscript reported 2.6E6 t of egg production, that was updated to 2.887E6 t in the year 2019. Besides, a reference was included.

Before:

“In other words, egg plate production amounted to 2.6 x 10 6 t in 2015 alone.

Now:

“According to the Mexican National Union of Poultry Producers (UNA, 2020), egg plate production in 2019 corresponded to 2.88 x 10 6 t.”

 We thank the reviewer for this comment.

The whole paragraph was intended to describe Mexico´s current state of the art regarding environmental assessments of the poultry sector. To clarify this issue, a sentence was added:

Before:

“... Despite the importance of this industry in food production, the environmental impact of its activity is poorly reported. There are no data reported on an environmental assessment to identify the environmental footprint of the poultry sector.”

Now:

“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 reported on environmental assessments.”

 We thank the reviewer for this comment.

Yes, because it provides the conjunction of both methods (LCA and VSM) for an industrial eco-efficient scheme.

No actions were taken.

 We thank the reviewer for this comment.

It was a typo mistake; it has been changed to “LCA” acronym for life cycle assessment.

 We thank the reviewer for this comment.

It has been changed from “Eco-efficient proposal” to “Eco-efficient scheme”.

 We thank the reviewer for this comment.

Yes, it meant “LCA”, and an “L” was added.

.

 We thank the reviewer for this comment.

“The” was added before “environmental impacts”

 We thank the reviewer for this comment.

The sentence has been changed removing “a” and adding “the” before semi-technified farm.

We thank the reviewer for this comment.

There are several indices to measure energy efficiency in the agricultural sector, these are commonly used:

●        Energy use efficiency (=total energy out/total energy in)

●        Energy productivity (=Yield/total energy input)

●        Specific energy (= Total energy in/Yield)

●        Net energy (=Energy out-Energy in)

Indeed, the level of a specific technology, the difference between energy productivity and specific energy is insignificant — one is simply the inverse of the other.

However, from a broader perspective, they are related to industry productivity, defined as the ratio of output to input. All input resources include personnel, machines, material, money and energy. The aforementioned energy indices are very useful performance indicators for industries (or the agricultural sector) and play an important role in enhancing the output in the respective area. Since input resources are partially-or in some cases totally- interrelated, optimization of these resources may lead to a better output or higher productivity. For better results, a breakup of these resources must be carried out to make appropriate control decisions.

Besides, both parameters are important because their value is used to prioritize agricultural activities when comparing and evaluating amongst different production processes.

 We thank the reviewer for this comment.

The contribution of the posture phase is detailed in (new) Table 5. Section 3.1. was updated to clarify this point.

Section 3.1 now reads:

Within the limits of the system (section 2.1.3), the environmental impact assessment of shelf egg production shows that the egg-laying stage accounted for 79 % of the environmental impact of the product (Figure 6). Of 18 middle-point impact categories (Table 2), 10 were identified as significant and represent at least 75% of the contribution in each category (Table 5). Of 10 identified categories in the egg-laying phase, seven are related to broiler compound feed. Therefore, this last one is the input with the largest number of impact categories. Other reports about egg-production also identify the compound feed as the input with the most significant contribution of environmental impact in the entire system product (Abín, Laca, Laca, & Díaz, 2018).

 We thank the reviewer for this comment.

The sentence was rewritten, as Table 4 indeed showed only 11 contribution categories.

Before:

The results of the analysis of the 18 contribution variables concerning the potential environmental impacts of egg posture phase are indicated in Table 5

Now:

Of 18 middle-point impact categories (Table 2), 10 were identified as significant and represent at least 75% of the contribution in each category (Table 5)

 We thank the reviewer for this comment.

Table 4 presents significant impact categories for posture phase and total process.

It was re-organized to group all categories corresponding to one single input.

Only significant impact categories were listed. “Significant” means that they represent at least 75% of the contribution of the total process. For example, Climate Change impact category is 5.6 kg CO2-eq for the total process. Posture phase alone contributes with 4.4 kg CO2-eq of the total value, from broiler feed compound.

Values of impact categories are definitively similar, because they are significant, as explained before, otherwise, they would not be considered.

Actions:

Table caption was edited, lines were re-grouped and a column was added to show the total value of impact categories across all shelf egg production phases.

 We thank the reviewer for this comment.

Table 3 with the global inventory of materials was included in the manuscript to clarify issues such as chicken manure and bird carcasses management.

This table shows that management for manure and carcasses is composting. Besides, Figure 6 was edited to include both chicken manure and mortality. This figure also shows that their contribution to the farm environmental footprint is less than 1% when considering a life cycle assessment approach.

 We thank the reviewer for this comment.

The digits were changed all of them to “XXx10^x”. The abbreviations are measuring for midpoint impact categories. Table 2 was added to show 18 impact categories, measuring unit and indicators.

 We thank the reviewer for this comment.

It’s corrected by adding a “x” before “10”

 We thank the reviewer for this comment.

-All typographic errors for CO2 were corrected.

-Regarding the CO₂ emissions:

In fact, in the referred Table (table 1), the reported range cover from 3.9-6.18 kg CO₂-eq and our calculated value was 5.58 kg CO₂-eq. Differences or similarities are hard to present because all studies differ in the system limits of the LCA, functional unit, farm technification type, geographical characteristics, climate conditions, evaluation method, cage accommodation system, etc. These differences in characteristics were mentioned in the limitations section (section 4.1).

Quite questions:

According to the Hy-Line International Management Guide (2018) of the Hy-Line commercial layers, in performance graph for mortality and age (weeks old), and in performance tables, state that mortality rates (cumulative, %) are expected between 0-8.4%. Thus, 5% is not considered the high mortality of this type of breeds.

The Management Guide is available at:

https://www.hyline.com/UserDocs/Pages/BRN_COM_ENG.pdf

Actions:

None were taken.

We thank the reviewer for this comment.

The treatment at the farm is composting.

As explained in Table 4, the dead chicken was considered as waste output in the LCA model, thus, for the model in the software SimaPro we used:

Biowaste {MX} treatment of, composting | Alloc Def, U.

 Regarding the amount of water:

This comment is much appreciated. Indeed, the reported amount (0.06 m³) was not correct. The amount should be 60.32 m³ (around 106 mL/chick-day), the amount suggested by the Hy-Line Management Guide (2018).

Action:

Figure 7 was edited to present the correct value for water consumption.

We thank the reviewer for this comment

Manure’s related emissions were indeed calculated in the waste management process, as part of the environmental impact assessment, nevertheless, its contribution was less than 1% of the total shelf egg-production process (Figure 6), thus, they were not reported as significant in the overall process.

However, this does not mean that when looking only at waste management scenarios, these emissions should be underestimated.

Actions:

None were taken.

33.   Use English

 We thank the reviewer for this comment.

It has been changing from “huevo” to “produced egg”.

34.   Studied farm

 We thank the reviewer for this comment.

“farm study” has changed to “studied farm”.

35.   What about farm size, breed quality, waste management strategies?

 We thank the reviewer for this comment

Yes, indeed some other factors might also influence these values. However, farm size might not be the case, as poultry houses tend to be had a standard measure and this work studies intensive shelf egg production. Moreover, breed quality might not be the case either, regardless of the breed, the physiology of the bird requires illumination (lumens) for egg production (ovulation).  Waste management strategies for poultry droppings do not influence the electricity requirements at the farm, as they are processed manually outside the poultry houses. However, different degrees of farm technification are directly related to fuel/electricity demand and therefore to the two indices in question: specific energy and energy productivity.

Actions:

A line was added at the end of section 2.1.1., to make it clear that the farm size corresponds to an intensive system.

.” The system at this farm is intensive for shelf egg-production.”

36. Any fan operation in the farm?

We thank the reviewer for this comment.

Yes, fans are operating in the farms, to extract air from the poultry houses.

They are mentioned in two sections of the manuscript:

First, in Table 4 (Fuel Inventory database from poultry farm per production phases), in the breeding phase, described as “air extraction” process, and in Figure 8, “extraction, 189 h…” in the breeding phase.

Table 4 shows the electric operations of the farm. In there, the “breeding phase” indicates that extraction refers to extraction air.

Actions:

None were taken.

37.   How you decide that numbers? Based on what?

 We were not able to understand the comment of the reviewer, as the highlighted text of the comment refers to several ideas but none of them reports numbers.

We ask the reviewer kindly to clarify the question.

No actions were taken.

38.  Questions

 We thank the reviewer for this comment

1) How did you come with those numbers?

An on-site analysis was carried out, where the equipment plate data were reviewed, and the information of the equipment manufacturers was consulted. The equipment(s) with the highest energy consumption at the farm were identified to propose more efficient alternatives. The concepts of energy billing (energy consumption, power factor, demand factor) were also considered as relevant data in decision making for the ecoefficient scheme.

Action:

In section 2.2, a brief description was added to specify the general methodology to examine the electrical equipment features at the farm.

b) What is your pump efficiency?

The efficiency of the current pumps is below 40%. In the ecoefficient scheme (breeding phase) the efficiency of the replacement pump would be 66.3%. In the posture phase, efficiency would be 82.5%. For water supply, the proposed pump would have an efficiency of 85.5%.

Action:

No actions was taken

c) Changing pump will mostly include changing pipping system, is that the case here?

No, a change of pipes would not be necessary, because the flow demand would remain the same.

Action:

No actions were taken

d) How do you justify your proposal

The operation way of the system is not optimal. By making a change with more efficient equipment, the producer obtains economic benefits in each production cycle, which allows him to keep product costs low. This scheme is beneficial as it decreases the carbon footprint of shelf egg-production.

Action:

No action were taken

39.   Change this

 We thank the reviewer for this comment.

“i.e. sub-index” has changed to “i.e. normal”.

Reviewer 2

Action

1.   Page 2, first paragraph, line 1-3: Reference could be added to strengthen the statements.

 We thank the reviewer for this comment. The reference Wilkinson, J. (2011). Re-defining efficiency of feed use by livestock. Animal, 5(7), 1014-1022. doi:10.1017/S175173111100005X was added.

Before:

Poultry farming is one of the production processes necessary for world food security

Now the line reads:

Animal husbandry is one of the production processes necessary for world food security (Wilkinson, 2011); dairy farming, meat, poultry and aquaculture, being the most representative.

2.   Page 2, second paragraph, line 7-9: These sentences seem like this article presents the environmental impact of poultry farm for the first time. But there are plenty of reports assessing the environmental impact of different types of poultry farms. Thus, the sentences can be modified to specifically say that the data from Mexico is new in this field.

 We thank the reviewer for this comment. The paragraph was referring to Mexico, but we added “in Mexico” at the middle of the paragraph for further clarification of the idea.

3.   Page 3, methodology section: Overall, more information should be shown in method section such as detailed study site, LCA variables, input data, and scenarios. More detailed comments are listed below.

4.   Page 3, second paragraph: LA might be “LCA”

  We thank the reviewer for this comment.

Yes, it meant “LCA”, and an “L” was added.

5.   Page 4, section 2.1.1.: What is the definition of “semi-technified farm”?

Other information about the study site can be included such as area of the farm, breed of the chicken, cage type, number of interior lights, and egg packing method/material, etc. This information can help other researchers to generalize this study results and apply the proposed method in other places.

  We thank the reviewer for this comment.

The definition of a semi-technied farm is:

 “A technified farm is characterized first, by high technology and automated processes that allow handling large numbers of animals and reduce costs depending on the volume of production; secondly, by the forms of disposition of credit or risk capital and integration of social capital. The technified and semi-technical schemes make use of the maximum possible efficiency of the food conversion index, so that they produce more efficient food and conditions for production, with rigid sanitary controls (Nava, 2012).”

This explanation was added to section 2.1.1., along with additional information of the studied farm. Section 2.1.1. now reads:

The study of shelf egg-production for the present work was conducted on a semi-technified farm, located in Tepatitlán de Morelos, Jalisco, Mexico, known as “Laguna Colorada”; (N 20° 45’, 48.811’’; O 102° 49’, 47.504’’). The location has an average elevation of 1,880 m above sea level and an annual average T of 19.1 °C. In Mexico, there are three different production systems, characterized by their technological level: i) Technified, ii) semi-technical and iii) backyard system. The differences between these systems are due to the technology that is handled. A technified farm is characterized first, by high technology and automated processes that allow handling large numbers of animals and reduce costs depending on the volume of production; secondly, by the forms of disposition of credit or risk capital and integration of social capital. The technified and semi-technical schemes make use of the maximum possible efficiency of the food conversion index, so that they produce more efficient food and conditions for production, with rigid sanitary controls (Nava, 2012). In the studied farm, only two parts of the process were automatized (breeding and posture phases). The laying phase was handled manually by farmworkers. The chicken breed was Hy-Line W-36, a battery cage system (450 cm² or three birds/cage) was used to house 96,000 1-day old chicks per poultry house. Adult laying hens were accommodated in three poultry houses.

 The characteristics of poultry houses at the studied farm were: dimensions 10m x 3m x 100m, controlled environment (31.46°C for breeding, 20.81°C for laying and 21.92°C for posture; humidity 50% and forced ventilation). A total of 917 incandescent bulbs were used per poultry house. Laying hens required illumination 16-17 h/day, thus, the mentioned amount of bulbs provided the needed 15 luxe.  Eggs were manually collected and packed in cardboard boxes containing 360 eggs. Waste such as manure and bird carcasses were manually removed from the poultry houses and composted. The obtained data of the life cycle inventory correspond to the summer of 2016. The system at this farm is intensive for shelf egg-production.

Also, this reference was added to the manuscript:

NAVA NAVARRETE, Juan de Jesús et al. Impactos del nivel tecnológico en la eficiencia productiva y variables económicas, en granjas porcinas de Guanajuato, Jalisco, Sonora y Yucatán. Revista Mexicana de Ciencias Pecuarias, [S.l.], v. 47, n. 2, p. 157 a 172, jan. 2012. ISSN 2448-6698. Available at: <https://cienciaspecuarias.inifap.gob.mx/index.php/Pecuarias/article/view/1479/1474>.

6.   Page 4, section 2.1.2: The reference flow is comparable to other farms? Is the total production period (76 weeks) similar with other egg production farms? Are 6, 10, and 60 weeks of system-product stages standard for all other off farms for breeding, development, and egg production, respectively?

  We thank the reviewer for this comment.

The reference flow might be comparable to other farms. However, this particular value is defined freely for each LCA model as required by the international standard ISO 14040:2016/14044:2006:

The reference flows are the specific product flows for each of the compared product alternatives. The reference flow is thus a quantified amount of the product(s), including product parts, necessary for a specific product system to deliver the performance described by the functional unit.

However, laying hens specific breed is definitively comparable with other production farms. According to the Hy-Line Management Guide, cumulative productivity rates at week 76 are 341-350.5 eggs (63 g/egg). Differences might reside in good practices at each farm.

Yes, the production period is similar to other farms that use this breed.  Hy-line W36 is advertised as “the most efficient laying breed worldwide” and it is used by the largest egg producers in Mexico.

Again, 6,10, 60 and even 90-week periods are suggested by the breed Management Guide.

7.   Page 4, section 2.1.4: Additional information for the input data (material/energy input, etc.) and 18 midpoint impact categories should be given to understand the model results. Further, developer and details of the used software and method need to be included.

  We thank the reviewer for this comment.

Actions:

Table 2 was added, which lists the 18 midpoint categories, indicators and measuring unit for each category of the method “ReCiPe Midpoint V 1.13 / World ReCiPe H”.

Also, Table 3 was added, which describes the inventory database related to material data inputs/outputs for each production phase.

8.   Page 6, Table 2: LCA inventory and environmental impact should be well explained. Input information and modeling approach (e.g., NL Mass MX Lq, Alloc Def, U, etc.) should be explained well in method section and removed when it is presented in the result section to minimize misunderstanding. Impact parameters should also be explained (e.g., what is CFC-11, de 1,4-DB?).

There are several typos such as CO2 and PM10.

  We thank the reviewer for this comment.

Actions:

●        Table 2 was added to describe impacts parameters such as impact category, indicator and measure unit.

●        Software input information was removed in the Results section.

●        Typos were corrected.

9.   Page 11 and Page 12, first paragraph: Did the authors considered initial cost and environmental impact between the current system and the eco-efficient scenario? Operational costs of the eco-efficient scenario could be much lower than current scenario but the reduction ratio might be changed if their initial cost/carbon-footprint is considered.

We thank the reviewer for this comment.

  We were not completely clear about this question/comment. We considered the initial cost OF the current system and then the cost of the eco-efficient scheme, for comparison purposes.

The period of study was summer 2016, and all data were collected at that particular time.

If the reviewer would kindly clarify the question, we would much appreciate it and act accordingly.

Actions:

None were taken

10.   Page 12: This reviewer strongly suggests to add limitation section at the end of discussion to indicate limitation, implication, and future research plan. For example, animal waste disposal and treatment can cause a critical environmental impact in poultry farms but it is not included in the life cycle.

We thank the reviewer for this comment. Some of the limitations were indeed mentioned in sections 2.1.1. -2.1.4. However, a limitation section was added as Section 4.1.

The section lists some of the limitations of this study. As explained before, animal waste disposal and carcasses management were actually included for the calculation of the life cycle assessment of this study. The manuscript now includes that information in section 4.1.

Action:

4.1. Limitations of the study

●        Comparisons of LCA are complicated even when using the same methodology, as results can differ with particular assumptions in each study.

●        LCAs focused on national or regional level may not be suitable for local applications, or vice versa. In the studied case, results from a semi-technified may not be suitable for small farms handled manually. Also, there is an important geographical limitation. The studied farm is located at the main egg producer location in central Mexico (Jalisco State), with benign weather conditions. Other important egg producer farms in Mexico are located in hot dry or hot humid weathers. In order to provide thermal comfort to laying hens, technified farms are likely to use different technologies than those reported here. Different, additional or even more modern equipment would imply variations on energy productivity as well.

●        The VSM results are also related to the limitations described for LCA.

Future research plan

The technification index for farms has not been reported in Mexico for the poultry sector. Therefore, the official reports of national greenhouse gases (GHG) for this sector do not consider differences among national shelf/hatching egg or poultry production. For this reason, it is important to develop new research in this sector to recognize the real efficiency, impacts and opportunities on energy management and environmental footprint.

Reviewer 3

Comments

Refutation answer

1.   Reference

 We thank the reviewer for this comment.

The typographic error was corrected.

2.   Analysis

 We thank the reviewer for this comment.

the typographic error was corrected.

3.   Table 2 “eq” and “de”

 We thank the reviewer for this comment.

“de” was deleted and “eq” was corrected

and now it reads “-eq” according to the ISO 14040:2016.

4.   3.3 “CO²”

 We thank the reviewer for this comment.

The upper-index was changed to sub-index.

5.   Figure 7 “huevo”

 We thank the reviewer for this comment.

The image was modified from “huevo” to “produced egg”.