GHG Balance of Agricultural Intensification & Bioenergy Production in the Orinoquia Region, Colombia

Round 1

Reviewer 1 Report

Dear authors,

I have read and reviewed your manuscript submitted to Land on GHG balances of agricultural intensification.

Overall, I find the manuscript and the analyses behind topical and relevant to the readers of Land.

 

General comments

I find it hard to see what you actually compare in the 2030 scenarios. You have the same output of crops and cattle, but not the same land occupation and obviously not the same bioenergy production. While it is clear how the bioenergy production is dealt with in terms of avoided fossil emissions, it is not so clear how differences in land occupation is dealt with. It is probably there, but could be highlighted further.

 

Length is an issue. The manuscript is very long and repetitive. In the discussion you repeat many of the explanations presented in the results, and then again in the result section. The manuscript could benefit from a stringent look through to avoid repetition and to ensure a logical sequence of presentation throughout the manuscript.

 

Specific comments.

 

Line 41

Typo, gases should be gas.

 

Line 157

Typo, capital should be capita.

 

Line 174-175

It’s a repetition of lines 127-130.

 

Line 183-184

You state that the low intensification scenario does not achieve higher yields than the reference scenario. Table 1 contradicts that.

 

Line 229-232

I don’t understand the argument here. You state that land used for cattle production in the reference and low intensification scenario is assumed degraded land, i.e. 100% degraded land. As these scenarios has the highest land use, then the subset of that land used for cattle in the medium and high scenarios can also only be degraded land, but as I read it, you assume that land allocated for cattle in the medium and high scenarios is not degraded land. Please clarify.

 

Line 253-254

I don’t understand your functional unit. Kg CO2 per ton product is not a function. The functional unit must be the same in all scenarios. As I read it, you should have a composite functional unit made up of a certain land area + an amount of agricultural crops + an amount of beef.

 

Line 258

Why do you emphasize methane emissions from rice production? You explain earlier that it is dry rice, not paddy rice. Are methane emissions particularly high from dry rice compared to the other crops you model?

 

Line 431-436

These in not results, but underlying assumptions and should be listed in the methodology section.

 

Line 440-442

Same comment as above.

 

Line 452 and 457

You use the term sustainable intensification, but you do not measure or explore the broader sustainability impacts of your intensification scenarios. The paper is about agricultural intensification and I would avoid using sustainable here. At least in the result section.

 

Line 556-557

Whether a land use is acceptable or not is a normative statement and you haven’t defined your boundary between acceptable and not acceptable. You can state that based on your analysis, using savanna land has serious GHG emission issues, but you can’t state whether it is acceptable or not.

 

Line 589 onwards

The conclusion repeats to a large extent the result section. The conclusion should briefly summarise the key messages of the study, not repeat the result section or discuss potential implications of the results.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The paper is high quality and certainly worthy of publication and seems appropriate for this journal. I only have a few‌ minor suggestions. 

I found Figure 5 a bit too busy (too many variables); is there any way to split this chart into two charts? 

In Figure 6 the legend is too small, along with too many variables. It should be split into two charts, or numbered figures, particularly since the two Y-axes do not have the same scale.  

I suspect Figures 5, 6 and 7 might work better as bar charts (bars running horizontally). 

Lines 207-208 - Did the authors consider modelling the field operations from the required field operations and field areas? There are agricultural Engineering coefficients that would allow this to be done, and at least paper in Elsevier journals that shows how to do it. While this addition might add a bit more precision to the model (maybe a future consideration), it is not critical, as fossil fuel use is generally a small quantity when dealing with the other terms in any analysis involing beef, soil carbon and LUC. 

Lines 287-288 - It is unclear what "emissions related to cultivation (fertilization..." means. Was the term, fertilization, the fuel cost of applying and/or manufacturing N-fertilizers, or the CO2equivalent of N2O emissions from N-fertilizer applications? I see that, at Lines 260-262, the model includes all three of these N-fert terms, but it would be helpful to the reader at this point in the text to clarify this a bit more. 

Somewhere in the Discussion, a comment on the impact of the proposed LUC on farm labour and livlihoods or local employment and land tenure/holdings might add an interesting dimension, at least to future extensions of this work. 

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Overall, the thesis structure is well structured, and evidence and supporting data are well provided, so it is judged to be sufficient for publication. I think it will be interesting to readers as well.

However, if the following content can be added, it will be a better thesis.

 

As the paper focuses on Land Use, it is judged that no further analysis has been conducted, but in the end, the GHG reduction effect of using the produced bioenergy has not been analyzed.

In the case of bioenergy, most of it is used as an oil, so after calculating the amount of GHG reduction due to the application of bioenergy in the energy sector (energy replacement in oil-fired power generation and mobile combustion (by vehicle use)), these are reduced to some extent in the entire Columbia GHG. It will be a better thesis if it is analyzed as well.

As the authors are well aware, CO2 emissions are not calculated during biofuel combustion, but CH4 and N2O must be calculated. Therefore, if the reduction is expressed together with this consideration, it will be interpreted more broadly. The emission factors of CH4 and N2O are presented in the IPCC guidelines, so if there are no actual values, they may be used.

If it is difficult to calculate the reduction amount, it is considered that it may be suggested as a limitation of the research and future research direction.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Dear Authors,

Your revised manuscript submitted to Land has improved and you have addressed the issues I raised in the first review.

I have only one issue remaining.

Line 258-261:

The use of the term functional unit is still confusing particularly if you are familiar with LCA literature, where the functional unit expresses the function different product alternatives provides and is compared against. Your kg CO2eq t^-1 is not a function; rather it’s the unit you use to measure or report GHG emissions. I recommend you reconsider the term ‘functional unit’. You could call it a ‘reporting unit’, a ‘measurement unit’ or alternatively add units, where appropriate to the first column boxes in figure 2.

Author Response

Point 1: Line 258-261:

The use of the term functional unit is still confusing particularly if you are familiar with LCA literature, where the functional unit expresses the function different product alternatives provides and is compared against. Your kg CO2eq t^-1 is not a function; rather it’s the unit you use to measure or report GHG emissions. I recommend you reconsider the term ‘functional unit’. You could call it a ‘reporting unit’, a ‘measurement unit’ or alternatively add units, where appropriate to the first column boxes in figure 2.

Response 1: Thanks for the comment, you are right, we are mistaken to use the term functional unit according to the context of LCA. We decided to rephrase in the text as follow: The emissions for all crop systems are expressed as kg CO2eq t-1 of product, which corresponds to tons of rice, tons of corn, tons of soybean, tons of plantain, tons of cassava, and tons of oil palm-fresh fruit bunches. For beef production, the emissions are expressed as kg CO2eq t-1 beef.  Please see line 261-265.