Grantee Research Project Results
Final Report: Renewable Energy-Powered Bulk Milk Cooling for Smallholder Dairy Farmers
EPA Grant Number: SU834725Title: Renewable Energy-Powered Bulk Milk Cooling for Smallholder Dairy Farmers
Investigators: Kisaalita, William S. , Brahmbhatt, Khoshboo Devang , Jones, Jonathan , Ndyabawe, Kenneth
Institution: University of Georgia
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 15, 2010 through August 14, 2011
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2010) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Challenge Area - Air Quality , P3 Awards , Sustainable and Healthy Communities
Objective:
Smallholder dairy farmers in nine sub-Saharan African countries are not able to deliver their evening milk to market. Our long-term goal is to find a sustainable solution to this problem. The proposed solution not only addresses this problem but is also an excellent intervention in three sustainability challenges of deforestation, indoor air pollution, and greenhouse gas (methane) emissions. The proposed solution constitutes a design of vacuum zeolite adsorption cooling (evaporative cooling) that is technically simple for rural smallholder dairy farming communities. These communities do not have access to electricity and lack skills to maintain and repair “complicated technologies” like vapor compression cooling systems. The source of power for the vacuum cooling is biogas. Each farmer will operate their individual biogas plant (digester), which will enable them to add, in addition to milk cooling, lighting and cooking.
The burning of solid biomass fuels (woody biomass and charcoal) with inefficient stoves inside homes is widely recognized as a ubiquitous air pollution problem that has resulted in respiratory disorders among African children. Use of biogas, a clean-burning fuel, will address this problem.
With increasing populations and given that in most sub-Saharan African countries, the energy sector is dominated by traditional biomass-based energy sources, any substitution of biogas for a substantial fraction of the needed energy will constitute a much desired mitigation against deforestation (forests are the main source of energy). Deforestation is threatening biodiversity of plants and animals that depend on the forest for survival.
Currently, the management practice on smallholder farms in Uganda is to pile up the cow dung in a pit till it is ready for application to crops as fertilized. To be ready for fertilizer application, the cow dung slurry undergoes anaerobic fermentation, producing biogas that is emitted in the air. Bubbling pits are a common site on smallholder farms especially the zerograzing dairy operations (feed is brought to the cows in the stable). The 50% to 60% methane component of the biogas that is emitted is a potent greenhouse gas. The global warning potency of methane is 23 times that of CO2. Anaerobically fermenting the cow dung and utilizing methane for energy purposes reduces the global warming contribution from smallholder farms.
In a first step toward the solution, we successfully reengineered an evaporative cooler (based on vacuum and zeolite adsorption cooling technology) in collaboration with a Germany company and made it applicable to milk cooling at the smallholder level. Through a World Bank Development Marketplace grant, we deployed (or field tested) this cooler among Ugandan smallholder dairy farmers and it received a very favorable response. This cooler was designed for cooling a maximum 15.5 liters, however, our field experience is suggesting that there is a need for higher capacity (e.g., 50-100 liters) for smallholder farmers with a larger number of cattle (e.g., over 6 cows). Also, the larger capacity cooler will meet the needs of smallholder dairy farmers for whom the availability of on-farm cooling is likely to increase incomes and enable the farmers to expand their herd. The current cooler design is operable by biogas. Higher capacity coolers (50-100 liters) can also be powered by biogas (i.e., scaling-up the current zeolite adsorption technology). Other possibilities included: 1) using a biogas electricity generator that in turn powers a standard vapor compression cooler or an icemaker, and 2) using biogas or solar energy to directly power ammonia absorption type of cooling units. These possibilities are likely to result into higher cooling costs or lower sustainability due to either increased inefficiency from an additional power conversion unit (generator) or complicated maintenance requirements. Vapor compression and ammonia absorption systems tend to be expensive and require high level maintenance skills that would be lacking among our target customers. This probably explains why no deployable system exists from any of these approaches. To address the need for a higher capacity renewable-energy powered cooler we proposed the following specific objectives in our Phase I project:
- Design a renewable-energy (biogas) powered milk cooler with a capacity of at least 50-100 liters, capable of cooling milk from 30 to 4°C within four hours.
- Fabricate a first prototype and evaluate its performance with respect to cooling to 4°C within 4 hours and establish the cooling cost per liter.
- Show that student participants, in comparison to their nonparticipating counterparts, are more likely in the future to make decisions in and outside their professional practice that are consistent with sustainability.
As required, this project is being student-led following models the PI has used successfully with the International Engineering Design Project and Summer Research and Service-Learning Experiences Overseas Programs (outlined in details in Phase I proposal). The two American students working on the project are both in leadership positions with the University of Georgia Engineers without Borders Chapter.
Summary/Accomplishments (Outputs/Outcomes):
A heat and mass transfer calculation has been done to ascertain the technical feasibility of the 50-100 liter capacity design. The vacuum will be generated on site with a vacuum hand pump as opposed to being sealed in, as in the lower capacity design in fieldtesting right now. To minimize cost, we decided to use off the shelf components that we could easily obtain. For the milk and cooler water containers, we sourced heavy gauge aluminum cooking pots of 70 and 100 liters, respectively. We welded a flange on the milk pan and added a rubber gasket. To render the water vaporization process efficient, it is necessary to surround the outer wall of the milk chamber with a wicking material. We had no way of telling in advance how well any cloth material would wick. Our initial thinking was that any cotton material would do well. We were surprised at cotton’s poor performance. The best wicking fabric among the many that were tested was COOLMAX® (used in for example sports clothing to absorb sweat and keep the wearer cool). We avoided “reinventing” the vacuum seal for the zeolite chamber. It turned out that the pressure seal on standard kitchen pressure cookers works well in reverse as a vacuum seal. The only problem was that the capacity for a single cooker was not adequate. We combined two pressure cooker vessels in series to meet the capacity required. In the second generation cooler (Phase II), we will fabricate a single container. For the hand-operated vacuum pump, we initially obtained a standard bicycle tire pump and reversed it. To vaporize water at a room temperature of 22°C, an absolute pressure of 0.026422 bars is required. Since these bicycle tire pumps are not rated for vacuum by their manufacturers, we just had to test several of them ourselves. All models tested did not meet the desired performance. Fortunately, after an exhaustive long search, we have sourced a hand vacuum pump marked by a German Company (HEDINGER) that is rated to 0.002 bars, well below our target vacuum. At the time of writing, the pump has been ordered but has not arrived. As such, we do not have any cooling results to report. We also experienced delays in securing the zeolite drying oven (the wrong model was delivered and had to be returned). It is being installed as we complete this report. Despite these setbacks, according to our Phase I timeline, our project is on schedule. We hope to have zeolite regeneration results and at least some cooling results by the time we present in Washington DC.
One of the PI’s pedagogical research interests is short and long term outcomes of servicelearning. Although the students participating in this project do not get academic credit, the project has all the elements of a service-learning course. The PI has pre- and post-tested other students that have participated in two global service learning programs he directs. The students participating in this project have also been pre-tested and will be post-tested at the end of Phase I, after their experience overseas in Uganda. The instruments used test for world-mindedness and interethnic communication apprehension. Students are also required to write an 800-word reflection on the experience. As with other service-learners in the PIs other programs, these participants will be followed at least five years after graduating in a longitudinal study
Conclusions:
It is too early to make any conclusive remarks. Perhaps we can use this pace to summarize the significance of the project. The resulting impact of success of this project will be in five related areas of: 1) Poverty alleviation (increased incomes of smallholder dairy farmers) and overall prosperity (more milk in the cold chain creating export opportunities; local manufacturing of coolers establishing a new viable and sustainable commercial sector), 2) Food security and nutrition (increased availability of milk for consumption), 3) Improved health (the burning of solid biomass fuels with inefficient stoves inside homes is widely recognized as a ubiquitous indoor air pollution problem, leading to a growing number of respiratory disorders; enough biogas capacity can be installed to provide not only for cooling but also cooking and lighting), 4) Reduced deforestation (by using biogas for cooking, less woody biomass will be needed; currently woody biomass-based energy sources are contributing around 95% to the total primary energy consumption), and 5) Green house gas (GHG) emission reduction (buy using the cow dung in biogas digesters and burning the methane to CO2, a less potent GHG, in the zeolite regeneration process; currently, smallholder farm open cow dung pits emit methane, a more potent GHG directly in the air).
We are confident in successful completion of our Phase I studies and we will be very grateful for the opportunity to continue to Phase II and take this project to completion. Below, we outline our phase II objectives and strategies.
Supplemental Keywords:
Poverty alleviation, Service-learning, STEM (science, technology, engineering, and mathematics), Social entrepreneurship, Food security, Sub-Saharan Africa, Sustainable development, Environmental sustainability, Smallholder or small-scale or small-acreage farmers, Diffusion of technological innovations, Renewable energy or biogas, Change-making, Study abroad, Rural studiesRelevant Websites:
Bringing It All Back Home Exit
Kisaalita Engineers Solutions for Africa’s Rural Poor Exit
P3 Phase II:
Renewable Energy-Powered Bulk Milk Cooling for Smallholder Dairy FarmersThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.