Grantee Research Project Results
Final Report: NOx-Out – Selective Catalytic Reduction System for Emission Control of Small Off-Road Engines
EPA Grant Number: SU835702Title: NOx-Out – Selective Catalytic Reduction System for Emission Control of Small Off-Road Engines
Investigators: Tam, Kawai , Yan, Alyssa , Almario, Anna , Cruz, Brian , Cocker, David , Matson, Jonathan , Christopher, Phillip , Singh, Priyanka , Chow, Timothy , Ng, Wartini
Institution: University of California - Riverside
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: August 15, 2014 through August 14, 2015
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2014) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Sustainable and Healthy Communities , P3 Awards , Sustainable and Healthy Communities
Objective:
According to the U.S. Environmental Protection Agency (EPA), emissions from operating gasoline-powered lawn mowers for one hour are equivalent to the emissions produced by a single car driven for 45 minutes [1]. Small off-road engines (SOREs), such as lawn mowers, leaf blowers and generators, contribute an estimated 15 to 20 percent of unhealthy pollution in many U.S. cities [2]. Approximately 40 million lawn mowers in operation in the U.S. alone significantly add to the air pollution in the atmosphere. Large quantities of pollutants are emitted from SOREs due to poor or lack of emission control devices. When exposed to sunlight, these pollutants drive a process that generates ground-level ozone, a compound known to cause respiratory ailments, especially in children, seniors and those afflicted with chronic lung conditions. The Asthma and Allergy Foundation of America (AAFA) noted 44,000 people have asthma attacks each day perpetuated by poor air quality [3]. To address these issues, the NOxOut device was developed to reduce such pollutants, thus, indirectly producing cleaner air for the world to breathe.
The original NOx-Out created in 2012 mainly focused on reducing harmful exhaust from lawn mowers, which can emit up to 25% raw unburned fuel (or hydrocarbons, HC) and produce large amounts of pollutants [1]. The main pollutants include nitrogen oxides (NOx), carbon monoxide (CO), volatile organic compounds (VOCs), and particulate matter (PM). The new NOx-Out has extended its application to immobile power generators. The current muffler-like device utilizes several components that reduce emissions in a step-by-step process. The low-cost and userfriendly device includes a porous stainless steel filter that removes PM, HC and VOCs. After filtration, NOx and CO are reduced to non-hazardous nitrogen, carbon dioxide (CO2) and water at low concentrations through a Selective Catalytic Reduction (SCR) technology. The catalyst component consists of a urea injection system and an ammonia slip catalyst produced through an ion exchange of copper nitrate on a zeolite substrate. The last section contains a fiberglass filter that reduces noise emitted by the engine. The overall goal of this project was to further improve the SCR technology in the prototype to increase the catalytic efficiency and longevity of the device.
Summary/Accomplishments (Outputs/Outcomes):
A new prototype was manufactured to highlight the best features of the previous designs. The device had been modified to be 3 inches in diameter and 6.5 inches in length, which increases reaction time and surface area of the catalyst to improve reduction of pollutants. With the stock muffler’s threaded connector on one end, NOx-Out can be easily attached to the exhaust pipe of lawn mowers and generators without the use of additional adaptors.
To determine the applicability of NOx-Out on other types of SOREs, we conducted emissions testing on a 4.5-hp generator with a load bank that simulated operational conditions similar to a lawn mower in use. NOx-Out was connected to the generator and the emission was measured using a 5-gas analyzer that quantifies NOx and other compounds. Previous experiments for the first NOx-Out device showed a reduction in NOx, CO and PM emitted from a lawn mower by 70%, 87% and 44%, respectively [4]. In our preliminary tests, there was an observed reduction of NOx by 2 ppm in four minutes. We are still in the process of running experiments to collect more emissions data.
To test the sound reduction capabilities of NOx-Out, we used a standard decibel reader to measure the noise level emanating from a lawn mower. There was an average of a 10-dB reduction with the modified device, which is a significant increase from the 2-dB reduction with the previous prototype.
Additionally, the pressure differential contributed by NOx-Out was also measured in order to determine if the device contributed any significant backpressure to the engine. NOx-Out was attached to the generator through a connector piece with a port for pressure measurement that was read with a digital manometer. The generator was operated at no load, 1-kW, 2-kW, and 3kW loads. The backpressure from the device at the highest load was 6.25 kPa, which is comparable to standard mufflers and also well below the 40-kPa maximum allowable backpressure for small engines. These findings demonstrate that attaching NOx-Out to SOREs will not harm the engine and is safe for consumers to use.
All tests were performed at the Center for Environmental Research and Technology (CE-CERT) at the University of California, Riverside.
Conclusions:
A new NOx-Out prototype was developed and is compatible for use with lawn mowers and power generators. In preliminary experiments, the device contributes comparable backpressure to that of a stock muffler, which is significantly lower than the maximum allowable backpressure for small gasoline-powered engines. This ensures that the use of the NOx-Out device is safe for both engines and consumers. In addition, the prototype muffles noise emitted by the lawn mower by 13 dB. NOx-Out also shows emissions reduction; however, further testing is necessary to collect more data that will be used to optimize the SCR technology.
References:
- Green Landscaping: Greenacres. U.S. Environmental Protection Agency.
https://www.epa.gov/greenacres/wildones/handbk/wo8.html. - Nonroad Engines and Air Pollution. 1996. U.S. Environmental Protection Agency, Office of Mobile Sources. EPA Publication No. 420-F-94-003.
- Asthma Facts and Figures. Asthma Allergy Foundation of America. http://www.aafa.org/display.cfm?id=8&sub=42#_ftnref1
Journal Articles:
No journal articles submitted with this report: View all 4 publications for this projectSupplemental Keywords:
Non-road engine, air pollution control, criteria pollutant, sustainability, green landscaping, human welfareThe 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.