Grantee Research Project Results
Final Report: Design and Prototype of a Sustainable Egg-Washer
EPA Grant Number: SU835317Title: Design and Prototype of a Sustainable Egg-Washer
Investigators: Jung, Sunghwan , Kotch, Alex , Chang, Brian , Sherman, Katie , Fox, Kemper
Institution: Virginia Tech
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: August 15, 2012 through August 14, 2013
Project Amount: $14,986
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2012) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
The outcome of this project is the design and creation of an egg washer for use on small scale farms or in remote areas. Industrial egg washers are forbiddingly expensive and impractical to use in the small farm environment. This egg washer will give farmers an effective alternative to the slow and tedious task of hand washing. Also, primitive hand washing techniques do not kill dangerous bacteria that could be present on the surface of the shell. The goal of the project is to design and build and effective egg washer that is sustainable, eco-friendly, efficient, and cost- effective.
Many egg-washers are designed for industrial production and far exceed acceptable costs and operational needs of a small farm. In addition, these machines are hardly environmentally sound, as they require large water and energy usage as well as toxic chemicals to perform the cleaning. Such an approach is accepted as necessary to remove mud, feces, and other matter common to dirty eggs, and to adhere to USDA regulations. Local farmer’s markets however are not required to adhere to these regulations. With 7846 farmers markets reported in the US last year, a 9.6% increase from the previous year, the need for a more sustainable option to egg cleaning is becoming more evident1 . The design team has set out to design an egg-washer that is simultaneously inexpensive, compact, energy-efficient, waste-efficient, and effective in completely cleaning eggs. This machine will be designed specifically for the needs of small farms and will avoid the use of toxic solvents. Ideally, this egg washer will be able to work in regions that have little or no access to electricity and will be easy to repair with tools commonly found on small farms.
The primary mechanism for the machine will exploit the phenomenon of cavitation bubbles. When the pressure in a fluid is dropped below the vapor pressure, cavitation bubbles form. The bubbles result in high fluid velocities along a solid boundary in the fluid, which then causes large shear stresses that can remove particles stuck on the surface. Commercially, cavitation is used in sonic toothbrushes to effectively remove plaque. Hospitals also use cavitation to clean and disinfect medical equipment. Research shows many other examples of cavitation successfully being used as a means of cleaning and a means of killing bacteria. The proposed design will show that cavitation can eliminate the need for harmful chemicals to kill bacteria on the surface of eggs.
Ultimately, the goal of this project is to build a device which is beneficial to people, prosperity, and the planet. The egg washer will aid the owners of small chicken-and-egg operations to become economically competitive by efficiently preparing an attractive product for the market. The design will make it possible for them to not only afford the washer, but also to operate and maintain it under a wide variety of circumstances. On top of this, the machine will be able to function without negative impact to water or soil quality. This project is part of the senior design course for the Engineering Science and Mechanics program at Virginia Tech, a two-semester project required of undergraduates in the department. The educational goal of this project is to give the students insight on how to include sustainability as an intrinsic part of a product’s design.
Research and preliminary testing to date has indicated the pursued design will be able to wash eggs on a level that is commensurate with the set goals. The use of cavitation to clean surfaces is widely used to remove plaque using a sonic toothbrush and remove the results of bio- fouling on ships. Future research concerns the different methods of using cavitation to clean the surface of eggs. This research will not only optimize the machine’s effectiveness, but also to contribute to the fields of physics and engineering. Naturally, the results concerning whether contaminants were removed from the egg’s shell must also be tabulated, and the optimal distance between the egg and the acoustic transducer that achieves the best result must also be determined.
Summary/Accomplishments (Outputs/Outcomes):
During Phase I, there were two different designs. The first design incorporated a spiral shape in which the eggs would be cleaned as they tumbled through a rotating mesh corkscrew. The main idea behind this prototype was that gravity would pull the eggs to the bottom of the spiral and hold them there. Induced friction between the egg and the mesh would clean the eggs. It turns out that this method does not clean the poles of the egg and still requires some use of detergent. Based on the negative results of this helical design, this prototype was replaced by a more promising design using cavitation.
The second design utilizes cavitation bubbles to clean the surface of eggs. In order to make the research useful to small farmers, the design is encompassed in a small tank in which the eggs will be washed. A transducer array is mounted at the bottom so that cavitation can be generated when the tank is filled with water. The eggs are pushed along a series of guide rails that lowers them underwater, pushes them along above the transducers, and lifts them back out of the water. While the eggs are pushed above the transducers, the eggs rest on two rotating cylinders that rotate the eggs as they translate, so that the entire surface is exposed to the cavitation.
Conclusions:
The egg washer design makes the research conducted during this project beneficial to farmers. Over the course of this project the team was able to design and build a prototype egg washer that utilizes cavitation to clean the entire surface of an egg without the use of any chemicals. The prototype also automates the process to obtain an egg washing rate of 480 eggs per hour, exceeding a typical farmers hand washing rate of 60 eggs per hour.
Three parameters were tested in order to determine the optimum conditions for cavitation cleaning: 1) distance between the surface to be cleaned and the transducer, 2) the height of the water in the tank, and 3) the time the dirty surface is exposed to cavitation. The distance testing showed a downward trend in area of removed substrate compared to height of surface being cleaned as distance from the transducer increased. Because of the negative slope of the line representing cleaned area vs. height above transducer, it would be more efficient to place the transducer as close as possible to the egg. The design will place the eggs three centimeters away from the transducer, because closer distances do not provide any significant improvement in their cleaning while only being marginally better on average.
The testing also concluded that water height has little to no effect on cleaned area as long as it is above the surface being cleaned. Therefore, water height in the prototype will be above the lower surface of the egg. The time testing concluded that longer exposure times correlate to more cleaned area. There is a minimum cleaning time to clean off any egg yolk, which is approximately one minute. As a result, the design will expose the eggs to cavitation longer than one minute, but less than the two minute maximum underwater exposure time set by the U.S. Food and Drug Administration (FDA).
Supplemental Keywords:
Reduction of toxic chemicals, Eco-friendly technology, Minimizing water waste, Sanitation, Egg washerRelevant Websites:
Department of Engineering Science and Mechanics Exit
The 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.