Practivistas Chiapas biodigester: Difference between revisions

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Team Biogas

• Julia Balibrera
• Annie Bartholomew
• Garnet Empyrion
• Gina LaBar

International Renewable Resources Institute-Mexico

Appropedia Page: International Renewable Resources Institute-Mexico

Website:www.irrimexico.org

General Information: info@irrimexico.org

Executive Director Alex Eaton: alex@irrimexico.org

Director of the Board Ilan Adler: ilan@irrimexico.org

Telephone: 011 (52) 55 3547 0221 or 011 (52 1) 55 1886 8210

Instituto Internacional de Recursos Renovables, A.C. Tlacotalpan No. 6 Bis, Int 301, Col Roma Mexico D.F. 06760 (52) 55 3547 0221

"IRRI Mexico is dedicated to promoting sustainable use of natural resources. We provide education, develop new technologies, and install systems that help low income families meet their basic energy, water, and sanitation needs in a sustainable way. Our projects aim to empower families, communities, and businesses to produce their own clean energy, obtain their own water, and manage their own resources and wastes in ways that benefit them and the environment simultaneously."[18]

IRRI's Mission

To promote programs and businesses that produce sustainable goods and services and help reduce reliance on fossil fuels. IRRI supports rural and low-income communities with the objective of improving the quality of life through generating, developing, and conserving local resources. IRRI’s vision is sustainable and equitable prosperity in a world without contamination."[19]

Background

In Chiapas, Mexico, mismanagement of animal waste is problematic with consideration to both the health of the planet as well as the health of its inhabitants, humans and other animals alike.^[1] The odors themselves can be harmful to human health, causing irritation of the eye, nose, throat, headache, nausea, vomiting. ^[2] Raw, or partially digested, manure retains hazardous pathogens which can be spread to humans through premature composting, agricultural run off and contamination of the water table. ^[3]Furthermore, surface run off of manure contributes to the degradation of local ecology. ^[4] The unmanaged (uncontained) decomposition of animal manure releases a host of environmentally destructive gases into the atmosphere, byproducts of fermentation. Methane gas as a greenhouse gas is approximately 21 times more potent than carbon dioxide. ^[5]

One way to midigate these effects is to install a biodigester. Biodigestion describes the biological process by which organic matter is digested by anaerobic bacteria over the course of time. In the natural world, biodigestion occurs in a variety of anaerobic (oxygen-free) environments, such as within marshes, upon the ocean floor, inside the human body and in manure. A biodigestor is a system which uses the metabolism of anaerobic bacteria in order to digest animal manure producing biogas, a clean, renewable fuel source, as well as effluent, an organic fertilizer which in the case of our Biobolsa system we call Biol. ^[6]

The Biogas produced in a biodigester system is a key incentive. For rural populations in Mexico, wood is currenty used as a primary cooking fuel for one in four households. ^[7] Wood as a fuel has several drawbacks: it is labor intensive to collect, it contributes to deforestation, and upon combustion poses significant respiratory risks to users.^[8] The popular alternative to wood use is Liquid Petroleum (LP) gas and electricity, the both of which require money. ^[9] Biogas can be an alternative to shouldering such an economic burden by providing low cost energy and increasing energy security.^[10]

Typically, biogas is composed of 55 - 65% methane, 35-45% carbon dioxide, a small fraction of hydrogen sulfide gas, and other trace gases. Of these impurities, the presence of H₂S (hydrogen sulfide) is the most problematic. Although H₂S constitutes less than 0.5% of the gas stream, it is extremely corrosive. Any metal equipment used within a biogas system to convert the gas to either direct heat applications (a boiler) or to more complex energy exchanges (a generator) will therefore degrade relatively quickly. ^[11] The larger the system, the larger the impact the presence of gaseous impurties will have on biogas production. As we are building a small, size 3 Biobolsa system ^[12], the intended application of the biogas is relatively small and therefore will not require an industrial approach to gas scrubbing. In order to reduce the H₂S in the biogas, our system uses a packet of non- stainless steel wool in the gas regulator; with this type of filter, the the H₂S will corrode the non-stainless steel wool before it has a chance to degrade metal equipment interior to the biogas´s end-use.

Animal manure has its high macro nutrient content. It confers considerable amounts of nitrogen, potassium and phosphorous to germinating crops and can critically improve soil health. ^[13]. However, research has proven that manure that has undergone biodigestion is a more effective fertilizer than raw, or fresh, manure. ^[14] Furthermore, the application of raw manure to soil can potentially contaminate agricultural products with hazardous pathogens. These pathogens are heat-sensitive, generally destroyed by temperatures of 36 degrees celsius or greater. ^[15] Biodigestion, of which mesophilic bacteria are primary players, occurs optimally at 15-40 celsius.^[16] This means that the effluent produced is pathogen free.

Objective

In the summer of 2010, a collaboration between students of Humboldt State University and the International Institute of Renewable Resources (IRRI) will seek the construction and dissemination of a biodigestion system, the Biobolsa, within the community of San Cristobal de las Casas, Chiapas. The objective of this project is to promote the realization of further Biobolsa projects in the San Cristobal de las Casas area by constructing a successful Biodigester demonstration system in the eco-home of local architect Juan Hidalgo.

Criteria

Criteria	Description	Weight
Level of Energy Generation	Amount of Methane Produced	7
Level of Fertilizer Generation	Amount of Fertilizer Bi-product Produced	5
Durability	Needs to withstand use with no more than of $5-10 yearly maintenance.	8
Cost	Needs to have enough spending to support project but not enough to bankrupt the community	9
Adherence to the Mission of IRRI	Meets IRRI's educational standards	8
Level of Cultural Appropriateness	Project must be able to be incorporated in the cultural setting of client.	9
Potential for Community Involvement	Must be a demonstration biodigestor designed for educating the community.	10

Budget

Materials	Unit Price (Pesos)	Quantity	Cost
High Density Polypropylene Biobolsa (3000 liters) and Kit [17]	$8000	1	$8000
4" PVC pipe	$35/m	2 meters	$70
4" PVC wye fitting	$25	2	$50
3/8" flexible hose (gas)	$7/meter	55 meters	$385
Cement	$115/bag	2	$230
Chicken Wire	$22/meter	1	$22
nails	$0	1	$0
4" PVC pipe (for drainage system)	$46/meter	5meters	$232
Printing of Interpretive Signs	$2	6	$10
Laminating of interpretive signs	$16	14	$224
Glue (for PVC)	$12.5	1	$12.5
Corrugated Plastic Roofing Sheets	$360/sheet	9	$3240
Post for roof (wooden)	$50/post	6	$300
Buckets	$15/bucket	2	$30
Cross Beams	$30/beam	3	$90
Beams	$15/beam	7	$105
Plastic Sheeting	$45/5 meters	2	$90
bricks	found on site	12-18	$0
stove	$0	1	$0
Total			$0

Materials

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The Site Before

site evaluation: does anyone have this?

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  Site for the biodigester

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  Site (roughly 7m x 3m) cleared and ready to begin digging.

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  The pigpen used to be given a layer of sawdust to facilitate cleaning but this practice had to be given up since the biodigester is unable to break down the lignin in the sawdust. (ref.)

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  Juan has three grown pigs, two females and one male. It's recommended that there be at least 6 pigs for there to be enough waste to put into the biodigester. Fortunately, he also has four 4 week old piglets, the future generation. Once they're grown it will mean more Biol^[18] and biogas produced more quickly.

Waste Chute

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  Sand is sifted for concrete mixture.

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  Compacting bricks for base of waste chute.

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  Chicken wire is laid on top of crushed bricks for base.

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  Concrete and recycled brick is used to build the sides.

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  PVC pipe is cut to connect to Bio Bolsa.

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  Pipe is inserted and held with concrete.

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  Bricks are covered and sealed in concrete.

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  Waste chute is connected to the Bio Bolsa.

Digging the Biodigester Trench

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  A tamp is used to level out the sides of the hole.

Rubble Trench Construction

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Cleaning pig pen

Roof

Blanket & Costal Barrier

Installation of Biobolsa

Biol exit & Overflow

Superadobe Walls

Finishing Touches

Testing

Hydraulic Retention Time(HRT) = total liquid volume of system (L)/ daily input of water/effluent mixture (L/day)

This equation illustrates the amount of time that material (effluent) will reside within a biodigestion system before exiting as Biol^[19], however due to sedimentation not all material will have the same HRT.

In order to calculate the HRT, we measured the amount of waste produced by Juan´s pigs within a 24 hour period. Our HRT, based on three seperate collections, is:

3,000 liter / 2 liters of effluent + 12 liters of water = 187.5 days, or 6.25 months

This value indicates that the system will require 6.25 months to complete biodigestion given a daily input of 2 liters of waste. As we have stated, the pigs in question are 3 mature pigs and 4 young piglets. As the four piglets grow, the daily input of waste is sure to follow. That said, the HRT can be expected to decrease with time.

Àmortization = (cost of system) / ( (Energy Produced/Year) + (Emissions Reduced/Year) + (Fertilizer/Year) + (Health Benefits) + (Quality of Life)

This equation illustrates the amount of time the system will take to pay back its initial investment as a result of energy produced (displacing the cost of other fuel sources), emissions reduction (which can be translated financially due to carbon market equivalencies), fertilizer produced (displacing the cost of fertilizer) along with the non quantifiable benefits of improved health and quality of life.

Dissemination of Different Models

Worldwide, the dissemination of different models of biodigestion systems has seen three general trends of biodigestor design which are identified by their different countries of origin. ^[20]

China

From A CHINESE BIOGAS HANDBOOK ^[21] "Since the 1950s China has experimented with the production of biogas from agricultural wastes, a practice based upon an age-old Chinese tradition of cornposting human, animal and piant wastes to produce an organic fertilizer of high quality. The breakthrough came in 1975 when a process was developed to ferment the materials in an airtight and watertight container in order to produce methane gas." This "breakthrough" describes the innovation of the Chinese Fixed Dome biodigestor, which has been reproduced in over 7 million systems around the world although the majority of these systems operate in China. The system is constructed of cement, thereby requiring skilled labor and an extensive installation time. In the field, the design has shown structural weakness in the low production of gas and the frequent occasion of gas leaks. ^[22]

India The floating cover, or Indian, biodigestor was designed to address the problem of gas leaks in the Chinese Fixed Dome. In this model, the gas storage mechanism consists of a floating cover, typically constructed of fiberglass, which rises in response to the generation of gas, therefore having a larger gas storage capacity. Although over 3 million have been constructed around the world, this system too is difficult to effectively demonstrate as the system consists of moving parts of high industrial cost (fiberglass). ^[23]

Taiwan The Taiwenese, or "tubular plastic", design is the most economical of the 3 models discussed. As a result of high installation costs and difficulty in replacing parts, a continuous flow digester contained withing a plastic bag was developed in order to achieve 1) greater weatherability 2) more efficient gas production 3) cheaper and more uniform manufacture and 4) a shorter installation time. ^[24]

Our project is based on this tubular plastic model for a biodigestor. Specifically, we will be building a Biobolsa system, engineered by Sistema Biobolsa ^[25]

Mexico

• Current:
  • Of the approximately 250 industrial biodigester projects that the Clean Development Mechanism (a mechanism of the Kyoto Protocol) has funded 200 of those are in Brazil and Mexcio. Additionally, nearly 30% of all the 'waste gas recovery projects' are in Mexico making up about 110 projects of which the great majority are anaerobic digesters. ^[26]
• Future:
  • Anaerobic digester systems may not be possible in some areas of Mexico due to water shortages. ^[27]

Logistical Analysis of Site

• Address + GPS

Client: Juan Hidalgo Calle Tapachula #55 San Cristóbal de las Casas, Chiapas Mexico 16° 44’ 27.46’’ N 92° 37’ 39.78’’ W Elev. 2154m Espacio: 7m x 2.7m

Climate of San Cristobal

• Monthly temperature averages for San Cristóbal de las Casas

"January Avg low: 17° Avg hi: 29° Avg precip: 0.03 cm February Avg low: 18° Avg hi: 30° Avg precip: 0.19 cm March Avg low: 19° Avg hi: 33° Avg precip: 0.02 cm April Avg low: 21° Avg hi: 35° Avg precip: 0.61 cm May Avg low: 22° Avg hi: 34° Avg precip: 3.45 cm June Avg low: 22° Avg hi: 32° Avg precip: 14.23 cm July Avg low: 21° Avg hi: 31° Avg precip: 9.64 cm August Avg low: 21° Avg hi: 31° Avg precip: 12.78 cm September Avg low: 21° Avg hi: 30° Avg precip: 12.15 cm October Avg low: 20° Avg hi: 30° Avg precip: 3.45 cm November Avg low: 19° Avg hi: 30° Avg precip: 0.77 cm December Avg low: 18° Avg hi: 29° Avg precip: 0.28 cm"

Foreca 2010 <http://weather.msn.com/monthly_averages.aspx?&wealocations=wc%3a7246&q=San+Crist%C3%B3bal+de+las+Casas%2c+MEX&setunit=C> (July 11, 2010)

• Daytime temperatures average from 19° C. (66° F.) in winter and 23° C. (73° F.) in summer. Overnight lows average from 5° C. (41° F.) in winter and 13° C. (55° F.) in summer. < http://www.innvista.com/culture/travel/mexico/sclc.htm > (July 11, 2010)

Thermophilic Bacteria

Micro-organisms which live in temperatures of 40°C-80°C are "thermophiles" and those that live in 10°C-47°C "mesophiles."^[28] A study was performed to assess the effect of temperature variations on the performance of a mesophilic (35 degreesC) and a thermophilic (55 degreesC) upflow anaerobic filter treating a simulated papermill wastewater. It was found that the thermophilic produced much less diversity in bacteria than the mesophilic. The study showed that both systems had a decrease in productivity (produced less biogas) when temperatures were dropped to 35 degrees C.^[29]

Tentative Schedule

• Week 1:
  • Literature Review
  • Criteria
  • Meeting with IRRI (7/8)
  • Set up Site Visit with Kiva

• Week 2:
  • Continue Investigation
  • Site Evaluation (Wed 7/14)
  • Arrange Site with IRRI and report to Lonny

• Week 3:
  • Class Installation (Tue/Wed)

• Week 4:
  • Assist IRRI with public course
  • Second Installation
  • Tests and Infrastructure

• Week 5:
  • Complete page on biodigestion on IRRI's website

Thought you might want this

The videos below include:

• Alex Eaton on how to install the biogas system
• Super adobe;Julia y Gina
• Films brought to you by Enrique Díaz

References