Final Report: Sustainable Anaerobic Digester/Cook Stove Design to Promote Health, Environment, and Economic Prosperity for Indigenous People of Ecuador

EPA Grant Number: SU833920
Title: Sustainable Anaerobic Digester/Cook Stove Design to Promote Health, Environment, and Economic Prosperity for Indigenous People of Ecuador
Investigators: Williams, Laurie , LaShell, Beth , May, Don , Kestenbaum, Emily , Melcher, Jim , Schooley, Megan , Shuler, Phil , Milofsky, Rob
Institution: Fort Lewis College
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2008 through August 14, 2009
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2008) RFA Text |  Recipients Lists
Research Category: P3 Challenge Area - Energy , P3 Challenge Area - Agriculture , Pollution Prevention/Sustainable Development , P3 Awards , Sustainability


During the 2008-09 academic year, Fort Lewis College students received a phase I, EPA P3 grant which was used to designed and build two biogas digester prototypes, design a low cost cook stove capable of burning the biogas produced, and evaluated biogas slurry application as an appropriate and effective soil fertility management method – both in terms of fertilizer potential and crop yield effects.

Proposed Phase II Objectives and Strategies:

In phase II of this EPA project we will optimize the prototype anaerobic digesters designed and constructed during the phase I project, develop a full scale digester, incorporate off-grid compression for biogas storage, optimize the cook stove design for burning biogas, and fully develop agricultural studies – over several growing seasons, to document the effects of biodigested manure on crops and soil health.

Summary/Accomplishments (Outputs/Outcomes):

Phase I prototype digesters demonstrated the feasibility of biogas generation, using simple materials such as trash cans, oil drums, and polyethylene bags – a full scale digester, based on prototype biogas production volumes, range from 5000 to 9000 liters, depending on the design implemented (fixed drum or polybag). This digester volume is projected to meet the cooking needs of a typical Ecuadorian family of six, 2m3/day.

A plant growth room study was conducted from January through March 2009 to evaluate the effects of field application of the anaerobically digested manure. The study included a pasture grass mixture and potatoes. Pasture grass was planted at a rate of 3 seeds per pot in 15 cm diameter pots containing a 2500 g sand/ 150 g potting soil mixture. Potatoes were planted, one per pot, in 35 cm diameter pots containing a soil mixture of 11,330 grams sand and 880 grams potting soil. Soil mixtures were designed to simulate the low organic matter, nutrient-poor volcanic ash soils of Chimborazo, Ecuador. The study utilized a completely randomized experimental design with 12 pots, 3 biodigested manure application rates, and 4 replications of each biodigested manure application rate. Rates of applied anaerobically digested manure were equivalent to approximately 0, 1660, and 3320 kg /ha manure fresh weight application.

For both potatoes and grasses, plant heights were measured and recorded. The averages of the heights for each test group (control, low application, and high application) were recorded. The dry weights of plant material were also recorded to determine yield differences. There is a clear growth difference for potato applications, and there was also a 132% and 131% yield difference over control for low and high applications of digested sludge, respectively. The growth data for pasture grass showed no significant results, however yield data indicated a clear difference. There was a 51% difference between the control group and low application yields for pasture grasses, and an 80% difference between the control group and high application group yields. There is a community cost savings of $2.59 - $5.17 per acre ($6.40 - $12.78 per hectare).


Biogas utilization for cooking, and for the production of anaerobically digested manure is a unique and realizable opportunity for a vast number of people and communities in both the developing and developed world. Positive impacts are possible in terms of quality of life (through reduced time for fuel collection, reduced fuel costs, and improved sanitation, increased crop yields), improved health (reduced indoor smoke from clean burning biogas), economic savings and/or earnings (eliminates need for purchasing traditional fertilizers and creates an opportunity to sell excess manure generated by digesters), and environmental responsibility (utilizes renewable resource, can enhance soil fertility, and anaerobically digested manure is pathogen free).

An especially interesting and exciting outcome of the phase I project were the results of the controlled experiments with pasture grass mixtures and potatoes, both principle crops in the mountainous villages of Ecuador. The prospect of local agriculturalists to utilize anaerobically digested manure as fertilizer fulfills one of the key tenets of sustainable agriculture, i.e. to minimize the use of external production inputs, and enhance nutrient cycling through the local agroecosystem. Even a partial replacement of purchased synthetic fertilizer by digested manure would enhance the sustainability of local agriculture.

Journal Articles:

No journal articles submitted with this report: View all 2 publications for this project

Supplemental Keywords:

Anaerobic digester, stoves, energy, efficiency, sustainable, health, environment, fertilizer, sustainable agriculture, Engineers Without Borders, Fort Lewis College;