The End

Hello readers!

Classes have finished, and on Wednesday we showed our project to the public in a poster presentation, along with the rest of the EXTD 120 and 160 students! We saw lots of professors, and even a few students came up to chat. A picture of our poster's attached, but a basic rundown of what we presented was that:

1. We were investigating a sustainable solution to cooking fuels in a small Nicaraguan community called Sabana Grande, communicating with the people there throughout the project,

2. We were specifically looking at biodigesters, which take cow manure and through anaerobic disgestion turn this into biogas which can be used for cooking,

3. We found that biogas is not an economically viable option at this time compared to using propane and wood (which are the currently used fuels), not even considering the high initial cost of the biodigester.

We have sent our calculations off to our community partners in Nicaragua, and they will check our assumptions to make sure they make sense. If our analysis is correct, we will save Grupo Fenix $1700 for the price of the biodigester!

It is unfortunate our biodigester was not profitable, and we had many comments from our presentation on Wednesday to make it so. Amazingly, we have done so much research that we were able to answer almost all of their questions!

Some answers to their questions:

-yes, about 75% of the biodigester cost is in the labor, and if that could be decreased (by perhaps a communal cow pasture, or using other kinds of waste) then the biodigester might be profitable. However, Sabana Grande is a rather spread-out community, and someone is needed to transport and sort the cow manure.

- yes, this biodigester model works in China, and they exist in India. We are not sure what makes it different there than here, but know that for our community the assumptions are different.

- no, we could not take advantage of economies of scale due to the relative scarcity of manure and water in the community, unfortunately.

- yes, the problem lies in how cheap propane and wood is, and if those prices rise, then perhaps biogas will be a good solution.

- there are perhaps other sustainable cooking fuels, and those lied outside the scope of our project. However, future semesters of EXTD 120 students will perhaps look into these solutions!

Our listeners were able to come up with many possible ways by which our conclusion could be changed to give a more positive solution. It shows the breadth of our research that we had already investigated many of these suggestions. It also shows the strength of Wellesley faculty that they were able to come up with almost all of the solutions we investigated, off the top of their heads, while it had taken us half a semester to think up and address these points!

In follow up for our work, some of us hope to visit Sabana Grande during Wintersession next year, to check in with our community. Further, Prof. Banzaert will be teaching EXTD 120 next semester, and those students will be able to perhaps do an analysis for a different product of Grupo Fenix, or perhaps adjust our calculations given the changing conditions or incorrect assumptions from the Sabana Grande community.

This Friday night, I and Audrey, another member of the EXTD 120 class, will be giving a one-minute presentation at MIT's D-Lab research conference on our work this semester. Looking forward to it!

Thanks to Gretty, Saebe, and Prof. Banzaert-- this project has been a completely different way of thinking and research that I haven't ever experienced, and will probably not have the chance to enjoy again. After documentation for this project, we are all done-- it has been great!

Monica

Our poster:

Cost Analysis sent to Lyndsay

Making a Product

Hello readers!

For next Thursday, we need something to show the class-- our final project! We have made a poster, and it is attached. Next time we will make edits to the poster and continue working on our final write-up, which is a summary of all we have done during the semester, nicely formatted. We will send this to Lyndsey and consult with our community partners, and also send her a version of the poster where the calculations are in terms of Nicaraguan cordobas.

We will also make sure we have completed everything on the rubric for our final project, and decide whether we will attend the Dlab presentations at MIT.

Cheers!

Monica, Gretty, and Saebe

Final Price Comparison of Biogas vs. Propane ("A Discouraging Result")

Final assumptions for the price comparison of Biogas vs. Propane

1. 8m^3 chamber produces 1m^3 gas

2. This model requires 65kg of manure, provided by 4 cows

3. 1m^3 of gas covers 18 meals per day (3 meals for a household of 6 people)

4. 1m^3 of biogas = 2.19 lb

5. People use a 25 lb tank for biogas, which can hold 11.4 m^3 that lasts for 12 days

6. Biogas costs $1.36 (34 cords) per m^3, so a 25 lb tank costs $15.58 (390 cords)

7. People use a 25 lb tank for propane that lasts for 30 days

8. Propane costs $11.49 (287 cords) for a 25 lb tank

9. Propane plus cost of obtaining propane: $13.82 (346 cords)

BOTTOM LINE

25lb tank propane costs $13.82 (346 cords for 30 days propane)

       11.52 cords per day of cooking needs

25lb tank biogas costs $15.58 (390 cords) and lasts for 12 days (1023 cords for 30 days biogas)

       34.11 cords per day of cooking needs

ASSUMPTIONS

assumptions of biogas price

-ignore initial cost, but initial cost is $1700, 42,500 cords

-ongoing maintenance: manure, water, labor

• Manure: 65kg added daily, $.005/kg = $.36 daily, 9 cords

• Water: $.325 per m3 or $.000325 per kg = $.02 daily, .5 cords

• Labor: Nicaraguan minimum wage ~ $.49/hour, 25 cords

Assuming 2 hours/daily, 50 cords daily

Total daily cost per household:

biogas: $1.36, 34 cords

propane (without opportunity cost): $.76, 19 cords

firewood: $.43, 11 cords

assumptions of propane price

-$11.49 (287 cords) for 25 lb tank

-plus 6 hours every 30 days for travel time ($2.33 every 30 days) = $13.82 (346 cords)

NOW FOR OUR POSTER TO EXPLAIN THE PROCESS AND FINAL COST ANALYSIS...

Comparing Biogas and Propane gas

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From all the assumptions that we have accumulated, we decided to compare the cost and usage of biogas and propane gas. We visually wrote down our calculations on the board to have more clear sense of estimations:

 Then we listed out different scenarios of using these gas so that the community can decide a scenario more convenient for people. Below is all calculations, comparisons, and scenarios that we made during last class:

Assumptions for the Model

1.     8m^3 chamber produces 1m^3 gas

2.     This model requires 65kg of manure, provided by 4 cows

3.     1m^3 of gas covers 18 meals per day (3 meals for a household of 6 people)

4.     1m^3 of biogas = 2.19 lb

5.     Propane gas costs about $5 per m^3.

6.     Biogas costs about $0.87 per m^3.

People currently uses 25lb tank for propane gas, which provides a month of gas for a household. From assumption 1 and 4, we can calculate that for a 25lb tank of biogas, it takes 11.4 days (25lb/2.19lb=11.4) to produce from 8m^3 chamber. Using assumption 3 and 4, this also means that 25lb tank of biogas covers 18 meals daily for 11.4 days. 

To summarize the information above:

·      25lb tank of propane provides 30 days of usage for a household

·      25lb tank of biogas provides 11.4 days of usage for a household.

*For 30 days of usage, a household requires:

·      6m^3 of propane gas, which costs $40 (Assump 5). Each household may spend ½ day for a trip to buy the tank.

·      34m^3 of biogas, which costs $21 (Assump 6). Each household has to make three trips a month because users need to wait 11.4 days for biogas to be produced from the camber. This process can be further explained below:

o   Leave the chamber for 11.4 days ->make first trip and use biogas for 11.4 days

o   Leave the chamber for 11.4 days ->make second trip and use biogas for 11.4 days

o   Leave the chamber for 11.4 days ->make third trip and use biogas for 11.4 days

We thought of two different scenarios to compare the cost of using propane gas and biogas produced from 8m^3 digester.

Scenario 1: 1 household using 100% of biogas produced from the digester

·      The household will have to pay $21 for monthly usage of biogas.

·      If the household did not use biogas but only propane, it needs to pay $40 for monthly usage.

->All of these calculations come from the section above with *

Scenario 2: 4 families share biogas from 8m^3 digester while using other gas or methods of cooking (ex. Propane gas or firewoods).

·      The household will have to pay $5.25 (21/4) for using biogas three rounds of 11.4 days.

·      The household will have to use propane as simultaneously when using biogas for 11.4 days.  It will have to pay $15.2 ($40/30days=x/11.4days, x=15.2).

·      In total, the household will have to pay 5.25+15.2=$20.75 a month for using gas.

All of these calculations are for villagers to choose what they prefer to do. Would they prefer to pay $40 and make 1/2 day trip a month for propane gas? Would they prefer paying $20.75-$21 for using only biogas or using both biogas and propane simultaneously while making three trips a month to biodigester? This is their decision.

'Break-Even Scenario' Assumptions & Calculation

'Break-even scenario' assumptions and calculations word-document shared with Professor Banzaert.

'Prezi' with document facts created to share with Lyndsay from Grupo Fenix (link: http://prezi.com/r8irrknjqvzq/break-even-biodigester-assumptions-and-calculations/)

Cost Analysis

Hello readers!

We've been trying to decide how cost-effective putting in a biodigestor might be. The first part of this calculation was how big we should make the biodigestor.

When we talked to Jorje, who is in charge of the current biodigestor, he informed us that they have much more dung available than we expected. If this is true, then a household-wide biogas system would be better than a community system. We have been told to stick with the community system because then people will be able to pay off the high initial cost.

Nevertheless, it is possible to design a household system, if the assumptions of how much manure is produced per household are true. If we also assume families aren't paying for water, aren't paying for this dung,  would spend 1 hour maintaining the biodigestor every day, are spending 4 hours collecting firewood every day, and if they weren't collecting firewood would be earning minimum wage, the cost-analysis curve looks like this for biogas. (This is not selling the biogas, this is just in terms of opportunity costs).

In this scenario, the biogas pays itself off at about 600 days (2 years) if the family was only buying propane gas, and 800 days (less than 3 years) if the family was using only firewood as their source of fuel. 

Another scenario is to have the family again supply its own dung and not pay for water, but instead decide to pay off the initial costs in five years by selling the dung. This ignores maintenance costs of the biodigestor and opportunity costs of earning minimum wage if not collecting firewood. 

If this occurs, the family sells the gas for $.79 daily, and it's great deal for the families using propane (who are spending $1.08 daily), but doesn't do anything for the families using firewood ($.43 daily)). 

Doubtless the actual scenario lies between these two scenarios, and their assumptions need to be combined. 

However, this is just on a household level. We were told originally to design this for a community level. 

We emailed Gunther, the engineer of the original biodigestor, this week. He was very helpful, and asked us a whole bunch of questions that basically outlined our entire project :). Two important things he brought up is that the village is drawing water from a single well, and there is probably not enough dung to expand the biodigestor beyond 8 m^3. This implies that our estimate for how much dung each household has access to is too high, and also that we can't make a bigger biodigestor because of water supply issues. Thus, we need to run all of the household simulations on the community biodigestor idea. 

Additionally, Gunther pointed out that there will be lots of issues with a community biodigestor, because what if some families are contributing more than others, and how will this be organized? Beyond all of the calculations that need to take place regarding how much to sell the gas for and opportunity costs, we also need to design a plan for how this will work with the actual users. Much remains to be done here. 

As for what we have accomplished, last class we spent much of the time collecting assumptions for the true cost of the biodigestor. This is why we now have estimates for how much water costs, maintenance costs, fertilizer costs (selling it is not worth it in this village), manure costs, opportunity costs, propane costs, etc. An interesting part of this project is that it takes a lot of time to collect each of these assumptions, and then the assumptions are definitely not guaranteed anyway. Plus, the actual analysis of all of these assumptions (via Excel-- or I actually think I'm going to move to Matlab for some of this) takes much more time than originally anticipated. 

Next time, we hope to generate more graphs for a cumulative scenario, with different estimates of price and opportunity costs, as well as refine the scenarios we already have (there are almost always problems). It would also be nice to make progress on a community-wide system for how the biogas would work on a people-level. 

Ciao!

Monica