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

Estimation and New Data

Hello everyone!

In our last class, we spent more time trying to make our estimations accurate. We are trying to estimate how the Sabana Grande women can make the construction of a new biodigestor profitable. As such, our main assumptions are 1) how much manure the women have available, 2) how much gas the women need/will make with their digestor, 3) how much this will cost and how much money this will earn (and all of the calculations within this), and 4) everything else that goes into the above calculations. With different assumptions, we get quite different values, and assumptions vary across websites (there is no one site that combines everything we need to know.) Thus, the first part of our class time was spent looking at the papers/websites together to determine how their information applied to our situation.

In the last twenty minutes of class, we were able to talk to Jorje, the man who maintains the existing biodigestor in Sabana Grande, to make our assumptions actual data! We asked him many questions, and luckily he spoke very slowly and clearly. Saebe did most of the talking, and we recoded the conversation and took notes (since all of us speak Spanish). We were even able to talk to a community member who happened to be near the phone!

Here is the information from our conversation:

Phone Call with Jorje 4/8/12

Saebe, Gretty, Monica

Where is the Cocina Solar?

Between Sabana grande y santa domingo

Tell me about the Cocina Solar’s biodigestor

It’s only for the restaurant. 8 m^3 large. Needs 65 kg manure every day. Produces 1 m^3 gas daily. Feeds 9-10 people per meal. We have 50 clients at the restaurant per day.

Can we share the Cocina Solar’s biogestor?

No, it’s too far away (poco arriba).

Could the community share a biodigestor of Cocina Solar’s size?

Yes, with good organization and maintenance

How many cows in the community?

Majority of the families have 4-6 cows.

How many people in the community use propane?

Few stoves that are propane.... most cook with wood. Would other people in the community like to use gas? Claro que si.  BUT they would need to buy new stoves, which are 30-40 dollars.

How many hours do people cook a day?

The majority cook with wood for 5-8 hours. Estufos singular. Madores?

How much does biodigestor cost?

Muy caro. Dolares?  He doesn’t know. The restaurant is fine though because it makes enough to keep it profitable.

How much does propane gas cost?

Propane gas (by itself, without cost of trip. )... 35-30 dolares. Sola el gas. 10-100 lbs. (For what he’s talking about-- check this site: http://gertodesing.blogspot.com/2011/05/gas-propano-y-butano-son-dos.html)

How much would they sell dung for?

Depending on what people need.... actually, people already give it for free. Transport?  People use carretas de metal, and on foot.

Would someone maintain the biodigestor?

Yes. The woman we talked to said she would. The biodigestor should be the center of the community though.

Are there people who can build a new biodigestor?

Yes.

Different model? Like their model?  Same model?

            They really like the same model.

Does the gas smell?

The first week it smelled, but then it didn’t after that.

Would people want to buy biogas instead of propane gas?

Yes, MUCH more convenient because it’s in the community.

------------

After our phone call with Jorje, we updated our assumptions in our excel file. The conclusions were drew were interesting. 

First, people have much more manure available than we expected. Also, they report much higher yields of gas from their manure than the values estimated on the internet. 

Second, gas is very unprofitable when compared to traditional wood. However, it is a good alternative for this community as compared to propane stoves. However, few members in the community use propane gas, so this biodigestor will be aimed at a pretty small population. 

We are still not sure of the best business plan for the biodigestor. We were originally envisioning a community biodigestor, but based on the values emerging from our estimations, it might be more useful to have it belong and used by a specific family. However, the initial cost is steep enough that this might not be the best option. 

Here is a copy of our excel document: 

In today's class, we want to determine the best business plan for this community, which is going to be one of the breakpoints in making this biodigestor plan happen. 

Monica

Post 4 - Estimations and Questions for Jorge

From our research, we found following assumptions for Chinese fixed-dome biodigester:

• 55 kg of dung requires 8 m^3 digester, which potentially produces about 0.45m^3 of gas
• .45 kg cow manure produces 1 ft³  of gas (.03 m³ gas) at 28 degrees C. This feeds about 4-6 people in India
• There are about 4-6 people in every household.
• There are about 20-25 households in the community Sabana Grande

Based on this assumption, we can calculate the following:

1/0.03=33.30.45 x 33.3 = 15kg ( for 1m^3gas, 15kg of cow manure is needed.)
55kg/8=6.88 ( 6.88kg dung requires 1m^3 digester.)

0.03 x 20 = 0.6m³
0.03 x 25 = 0.75m³
About 0.6-0.75m³ of gas needed in the community

15 x 0.6 = 9kg
15 x 0.75 = 11.25kg
About 9 - 11.25kg of dung required per day

9/6.88 = 1.3m³
11.25/6.88 = 1.64m³
About 1.3 - 1.63 m³ of biodigester needed.

From our research, we found following assumptions for plastic model biodigester:

Digester Dimensions of Existing Model in La Casita Solar

Volume= 8 m cubed
r= 1.6 m
d= 3.25 m
h= 1.5 m

Digester Dimensions of Our Model, tentatively
Volume= 2 m cubed
Curved Surface Area= 3 m squared
r= .68 m
d= 1.36 m
h= .62 m

Costs of materials
Cement: $3 per m cubed
Bricks and Mortar: $2 per m cubed
Stone (piedra): <$2 per m cubed

Anecdotal:
-Plan for approx. $150 for materials, per meter squared
-Cement to cover 3 m squared SA of dome should cost $105

Some important considers for location:

-Proximity to stable source of manure

-Distance from highly populated areas (scent)

-Distance from owner/operator's dwelling

-Rockiness of the land (avoid overly challenging installation process)

-Sun/shade (avg. temp in Nicaragua: 77-81 F)

Sources

http://learningstore.uwex.edu/assets/pdfs/a3601.pdf

http://journeytoforever.org/biofuel_biogas.html

http://journeytoforever.org/biofuel_library/MethaneDigesters/MD4.htm

https://wiki.umn.edu/pub/EWB/Haiti_Biogas/DOME_digestor.pdf

http://www.completebiogas.com/B_Plastic.html

http://www.adelaide.edu.au/biogas/poly_digester/aguilar/sld004.htm

From our research, we found some questions that have to be answered especially to calculate the cost of gas currently being acquired and the price of biogas that will be sold:

• Que es el precio de billete por autobus?
• Que tipo de molino tiene? Sabes para que los trabajadores en los molinos hacen con los restos de ______ (el sobrante o extra)?
• Cuantas vacas hay en la comunidad de el Frayle? en la Palmera? En colonia?
• A que distancia es la latina en relación de la casa de una familia?
• Cuanto cuestan el ladrillo, el cemente, la arena en tres metros cubicos (cuadrados)?
• Cuanto costó para fabricar la planta de biogas en La casita solar?
• Cuantas personas-- en una comunidad de ciento personas--usan gas propano?
• Qual tamaño del tanque de gas propano usan las familias normalmente?
• Cuanto cuesta el gas propano en general, talvez para un tanque?
• Por cuantas horas las familias cocinan?
• Cual tipo y tamaño de estufa tienen las familias en general?
• Cuanto estiércol se usan para la planta de biogas en La casita solar? Cuantas vacas hay para la produccion de biogas?
• Podriamos saber para cuanto las familias quieren vender estiércol de sus vacas y de la gente?

Post 3, Week 1

Professor Banzaert's talk with Lyndsay and our Response to the new Specifications

The Sabana Grande already has 2 existing biodigesters. They want another community biodigester, to be tentatively located near/operated by a community leader (who also lives in a dense community). The community members can sell their manure, and then the digester operator/s can sell its gas. 

Since the restaurant digester at La Casita Solar uses a combination of human waste and cow manure as raw materials, we plan to do the same. (we need to confirm with Jorge that the existing digester gets 20 pounds/week manure from cows, and find out if there is much more manure that could be collected). We did the following calculation to figure how many hours of cooking the existing digester can sustain:

• according to http://www.adelaide.edu.au/biogas/poly_digester/aguilar/sld004.htm: 22 kg (50 lbs.) of manure per day gives 12.7 hours of cooking
• The Women of Totogalpa have 20 lbs. of cow manure per WEEK, so 20/7  gives around 3 pounds manure/day. This gives (50/3 = 12.7/x) so x =.76 hours of cooking per day, so 40 mins of cooking per day.

Because 40 minutes is not much cook time, we tried to figure how much human waste would generate a more reasonable amount of daily cooking time:

• according to the book The Truth About Poop, people produce one ounce of poop for each 12 pounds of their body weight.
• So, if you've got a person of 150 lbs, they're pooping 150/12 = 12.5 oz poop per day, which equals .75 lbs/day. And if you've got a person of 75 lbs, they give about .3 lbs/day. People poop between 1-3 times per day, so if everyone in a household (say 2 adults and 2 children) were pooping, that’d give around 2 lbs of poop per day. This gives about .5 hour of cooking time.

If a biodigester got 3 pounds of cow manure a day and 2 lbs. of human waste a day, then there will be enough methane to sustain (40 min. and 30 min.) 70 min. of cooking a day.

We don't think this is enough. And if it isn't enough, then must consider how much will be enough. A digester that is one meter cubed can hold up to 50 lbs. of manure. If 20 lbs of cow waste and 14 pounds (the amount of poop of one family, per week) of human waste a week generates too little gas, then we are talking about building a digester that may be as big as 2 meters cubed.

The digester cannot cost more than $200, either… With this, we proceed with our project statement and initial specs

Project Statement: 

The purpose of our project is to design a plan for the effective implementation of a new community biodigester in the Nicaraguan community of Sabana Grande. The biodigester will consume as much human, animal, and food waste as possible, and convert it to valuable propane that can be sold back to community members. Output waste from the digester will be used as a fertilizer that supports local crops.

Specifications: 

Scale: Digester will be an underground, permanent structure that is larger than 1 meter cubed in size. 

Base scale on output gas (based on how much manure we estimate we will have, and also considering how much gas we imagine the people in the community will need)

Digester Material: Digester will be constructed primarily with local bricks and concrete. 

Base on the local materials in the area, building the most sustainable model that is affordable

Location: Digester will be located near a community leader's home, who will also oversee/operate the digester. It will also be far enough away from homesteads that smell is not an issue.

Specify how far away the digester must be for smell to not be an issue. Also need to find out how discouraging biodigester fuel is, as a result of its stench.

Raw Material for Digester input: Combination of human, cow, and food wastes. The local community is interested in a system that flushes human waste directly to the digester. More than 35 lbs a week total will be needed if we wish to generate more than 70 minutes of cooking time for one family. Note that a digester that is 1 meter cubed in size can only hold 50 lbs. of waste. We therefore likely want a digester that is close to 2 meters cubed in size.

Confirm with Jorge how much manure is being used by the current digester-- is it really 20 lbs?

Cost: Underground digester will cost an initial $300-500. This is more than the $200 budget we have. 

Maintenance: System can clog, and it is hard to clean out. Putting the digester in an ideal location, that has a slope, is essential to allowing the decomposed waste filter out of the digester and be used as fertilizer.

Speculations on Differences between 3 different digester models

Below is a chart we made that compared three different digester models: Underground (based on the Indian model), Plastic Bag, and Floating Drum

	Underground	Plastic Bag	Floating Drum
Efficiency	High efficiency (0)	The dairy digester produced 0.32 m3/day of biogas per m3 of digester volume, 5.5 m3/cow/day. The swine digester produced 0.10 m3/day of biogas per m3 of digester volume per day, 0.15 m3/pig/day. (0)	Low. 20% of gas loss. (-1)
Cost	$300-500 initial (0)	$33-100/ probably more realistic $200 (+1)	550 Euro. $706.64 (in current exchange rate). High material cost for the drum. (-1)
Maintenance	System can clog, nearly impossible to clean out-- must have effective output component for collection of waste for fertilizer (0)	after 3 years need to replace plastic bags completely. (or two years or less-- all depends on plastic quality) Needs to be fed and watered every day. (-1)	Hard. Experts or instructions required. Drums have short lifespan (0)
Installation	Hard, labor intensive (0)	intense. very instructions-intensive, though not that much actual work (0)	Relatively easy. Compact design for household. (+1)
Scale	2 x 2 x 2 m digester requires about 12 lbs manure/ day, yielding 3 meals for family of 4-6 (0)	3x10m, 7.2m^3 volume. produces 1.9m^2 per day,12.7 hours of cooking. need 22 L of manure per day, so 3 cows manure per day (0) 3.5 m long, 1.2 m diameter (520 L liquid) (plastic) = $33 vs PVC ($100)... produces 65 L gas/day.... 80% of the total volume is liquid... (cubic meter of gas will do 3 meals a day for a family of 4-6)... going to produce less than 1/10 a cubic meter a day  excreta produced by 10 fattening pigs will require a biodigester of 4 m³ liquid capacity....	2m^2, 2.5m height. (Dimension of water tank: 1000L. Effective usable volume: 850L) Treats 1-2kg kitchen waste per day. The usable gas volume of the 750L-gasholder is 400L. (-1)
Location	Underground, near pig sty/cow pen (0)	underground, near pig sty/cow pen (0)	Above the ground. (0)
Output (and Time to Produce)	1x1x1 m methane, daily		30Nl (FW) and 103Nl (MW) per day, 8.6% and 109.6% of the measured gas production. 100L biogas=22min burning on cookstove. 2kg kitchen waste = 200L gas. Retention time depends on feedstock (foodstock about 10-40days)
Other  Comments  on Advantage	-underground is best for tropical countries (doi:10.3390/en5082911)The larger scale models, like this one, relate to very large scale factories. This model may be a stepping stone for the construction of bigger bioenergy factory	cheaper than most other types	Constant gas pressure
Other Comments  on Disadvantage (toxic?)	gas can escape through concrete pores, difficult to clean, takes up a lot of space (0)	not very pretty at all, needs to be protected. (-1) a lot of problems with plastic quality
Rank	0	-1	-2

Diagram of Existing Digester in La Casita Solar, from Lyndsay

Find out what community members think of the current digester design-- if it is liked and well understood, then it is probably a good model to go with

Scale-- output

Cost of materials

Location and smell of fuel

Questions for Monday/in Spanish

First Post!

Hello!

Saebe, Gretty, and I (Monica) will be working together to find the best design for a biodigestor in the coming weeks. The Women of Totogalpa are looking to improve their existing biodigestor, and we will be communicating with them, along with doing extensive research, to figure out how we can best contribute.

Here is some background on the Women of Totogalpa, and the project in general.

Here's an article that describes the Women of Totogalpa, who belong to the second poorest municipality (Totogalpa) in the second poorest nation of the Western hemisphere (Nicaragua).[1] Grupo Fenix was founded in 1996 by university students and their professor at the U of Managua, and is focused on researching and delivering sustainable technologies to Nicaragua. So far, they have " install[ed] solar pumps, solar drip irrigation systems, micro-hydroelectric systems, PV battery charging centers and hundreds of photovoltaic systems in rural communities. They also built solar dryers, solar water heating systems, biogas digesters, dozens of solar ovens, hundreds of photovoltaic panels and a hand full of miniature solar cars." [2] Many new organizations also arose because of their efforts. The Women of Totogalpa is one of these organizations, that was developed after solar cookers were brought to the area. 

The Women of Totogalpa built a solar center, a solar restaurant, host visitors from Grupo Fenix and improve their homes through a microloan program, improve solar cookers, are working on many other solar projects, established a scholarship fund for secondary education, have access to electricity (mostly solar). Details about their solar cooker: "The cooker design is based on a model originally promoted by Bill Lankford throughout Central America. It’s a box cooker on a stand with wheels so it can be moved easily. It has one reflector in the front of the cooker for easy accessibility. Throughout the years the women have been adapting the cooker to their specific needs, and constantly improving it and updating the design. The cookers, which have been used to roast coffee and cook rice, vegetables, chicken, cakes and cookies, don’t replace wood 100%, but definitely help reduce the amount of wood used for cooking, and the amount of smoke the women breathe throughout their day." [1] 

Image [1]: 

 

[1] http://ases.conference-services.net/resources/252/2859/pdf/SOLAR2012_0230_full%20paper.pdf

[2] http://grupofenix.org/about-us/our-story/

Each of us did some research on the topic, and our observations are recorded here!

Saebe:

Biodigestor

"Currently there are two examples of biodigestors in the community of Sabana Grande.  One that is located at the Green Energy Restaurant “La Casita Solar” which runs on a combination of human waste and cow manure and another that uses the tunnel design run on cow manure.  We would like to come up for a design that could be used in the households of Sabana Grande.  Few people have access to large quantities of either cow or pig manure.  We would like the design to be an affordable alternative to cooking with firewood.  The initial installation of the system should cost no more than US$200 and should use materials locally available.  Fuel to be added to the biodiogester should be on a par of what is spent weekly in firewood consumption (approximately US$3) so that this can be a viable alternative."

Unfamiliar with biodigestors, I first had to research their basic definition. A biodigestor essentially takes in manure and produces usable cooking gas and organic fertilizer. According to one blogger, "It's basically a huge plastic bag laying on top of straw, insulated between adobe walls and covered with a roof." It serves as a cheap and reliable source of energy. It has great social and environmental benefits. This project is geared towards the same community as the solar cookers, where cooking with firewood is common but dangerous to the women's health.

Existing designs:

This image from the Grupo Fenix website shows a man putting well-mixed cow manure into the biodigestor for the restaurant's use.

Another example of biodigestors.

Questions: 

Will this be installed in the home, or outside of it?

If few people have access to pig or cow manure, is it going to be processing mostly human waste?

How complex must the design be in order to ensure sanitary outputs?

--

Gretchen:

1.) Develop a bio-digester that is suitable for household use in the community (see attachment).  

The Organization

Solar Center in Sabana Grande of Puerto Rico or Venezuela

The local community

Sabana Grande is a municipality of Puerto Rico

Existing Solutions to the problem

ARTI (Appropriate Rural Technology Institute), in India: Biogas from food waste, not manure

-https://www.youtube.com/watch?v=BGSl72xZHNk

Biodigesters: At the bottom of the tank is the fermentor, and then at the top is the gas holder. At the bottom is the manure with water, that ferments and produces methane. Apparently the tank in this particular model is separated in two-- the top part, which fills with gas, raised as the bag within the tank fills with methane. It lowers when it is empty. A cap at the top lets the methane out for use. It is good to use manure/food waste that can be totally digested by the bacteria. Bacteria feed on the food waste-- they themselves exist in the manure. They produce more methane when there is more raw food material present.

http://earthedintl.blogspot.com/2011_06_01_archive.html

Waste is pumped into an anaerobic digester where naturally occurring microbes digest the waste and make gas. That biogas (methane and CO2 is taken to a generator). 

A list of questions about the project

-is the local community in Puerto Rico or Venezuela? I could not find more information on the organization or the individuals involved

-are there food wastes in the community? Is there an existing system of food waste disposal?

--

Monica

Project: develop a bio-digester that is suitable for household use in the community.

Estado de Proyecto

Este breve resumen sirve para reclutar nuevos voluntarios adecuados para el proyecto.

Nombre de Proyecto: Biodiogestor

Colaboradores de proyecto: Solar Center

Descripción de proyecto: To design a biodigestor that will work in the reality of Sabana Grande

Estado actual: Currently there are two examples of biodigestors in the community of Sabana Grande.  One that is located at the Green Energy Restaurant “La Casita Solar” which runs on a combination of human waste and cow manure and another that uses the tunnel design run on cow manure.  We would like to come up for a design that could be used in the households of Sabana Grande.  Few people have access to large quantities of either cow or pig manure.  We would like the design to be an affordable alternative to cooking with firewood.  The initial installation of the system should cost no more than US$200 and should use materials locally available.  Fuel to be added to the biodiogester should be on a par of what is spent weekly in firewood consumption (approximately US$3) so that this can be a viable alternative.

Próximos pasos: To determine if this is a viable project.

--

My research: 

Here is a picture of the biodigestor, located in the Casita Solar, which is the restaurant built by the Women of Totogalpa (see above description). He is loading cow manure into it, and I assume it's the brick on the group. Look, you can see the solar panels in the background! Here is a website, where they also describe the new project of generating portable solar cookers, which also seem to rely on wood. Note that the solar cookers have to be sturdy enough to cook coffee, jams, and other restaurant foods... (pic also comes from the above link)

Biodigestors can be very simple systems; essentially, you put the excrement (animal or human) into a tank, which does not have much airflow and is warm. You'll get methane gas (you can take it out of a pipe for cooking) and fertilizer due to the anaerobic bacteria digestion. If placed underground, it can be used year round, and the more complicated systems store the gas for when it needs to be used. They can be built with less than $100 with a tank and some inner tubes, and are being used increasingly in developing countries. [4]

[4] http://www.slideshare.net/raddieman/an-introduction-to-biodigestors

My questions: this sounds wonderful. I'd like to learn more about how to construct a biodigestor, what kind of scale they can be operated on, what are their drawbacks, and what are the women currently using in their restaurant. 

--

On our first day, we established our goals for this group. We will not be trying to construct a biodigestor from scratch, because that would take much longer than the few weeks we have (additionally, it’s too cold outside). Thus, our plans are to communicate with the Solar Women, and research to come up with existing biodigestor solutions.

We each planned to do some research on the topic, and create a sketch for a possible design based on our research. Gredy already did a post on her research, and uploaded the three designs!

We also came up with questions to ask Lyndsey, who is at GrupoFenix and is our coordinator with the Solar Women.

Do you have any documentations/pictures of the biodigester that you can share?

Why and how did the community start using the biodigester? (Could you specify the what the goals were for the project? ex reduce reliance on trees, take care of extra animal waste)

How much gas is it producing so far?

What are the challenges that arose while designing the biodigester?

What are the current challenges of using the biodigester?

How familiar are people with the design and are they willing to install biodigesters in their households?

Could you connect us to potential users?

The current biodigester:

            -who operates it? Can we talk?

            -where does the waste (manure) come from? Does everybody contribute? Are there pipes involved? etc

            -do some people in the community have problem with the system?

            -are you primarily looking for more biodigesters or better ones?

            -What is the community structure? Do people live in homes that are close to one another-- (perhaps answer this question by google maps)

 Additionally, we came up with group roles:

Goal Minder- Gretty: is what we are doing getting us closer to goal?

Timeline Minder- Monica: are we hitting our dates? What can we do right now?

Community Partner liaison- Saebe: communicating with Lyndsey.

Finally, we found most of our information on practicalaction.org.

Until then,

Monica

Ps, we will alternate on who has responsibility for posting every week :)