NOx-Out – Selective Catalytic Reduction System for Emission Control of Small Off-Road Engines

EPA Grant Number: SU835702
Title: NOx-Out – Selective Catalytic Reduction System for Emission Control of Small Off-Road Engines
Investigators: Tam, Kawai , Chow, Timothy , Christopher, Phillip , Cocker, David , Cruz, Brian , Matson, Jonathan , 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 - Built Environment , P3 Awards , Sustainability


The NOx-Out prototype is designed to be an inexpensive selective catalytic reducer (SCR) which can be retrofitted to any small off-road engine (SORE) for the reduction of harmful emissions. Currently our design is focused on lawn mowers, which can emit up to 25% raw unburned fuel and produce large amounts of carbon monoxide (CO), nitrogen oxides (NOx), volatile organic compounds (VOCs), and particulate matter (PM). These pollutants, originating from lawn mowers contribute to approximately five percent of the nation’s air pollution; contributing to respiratory ailments. The ongoing development of this innovative prototype will encompass the optimization of emissions removal, extended durability of compartments within the prototype, and construction of an affordable, user-friendly unit using low-cost materials. The overarching goal of this project is to further develop a sustainable and inexpensive NOx-Out prototype.


A selective catalytic reduction (SCR) system was proposed to be integrated within the prototype. SCR technology is commonly found on diesel trucks to regulate their NOx emissions; nonetheless, expensive catalysts are being utilized for this application. A cheaper alternative catalyst has to be obtained because the cost of a lawn mower is relatively inexpensive. The components of the prototype include 1) a filter to prevent catalyst coking, 2) urea injection prior to the catalyst compartment to act as reducing agent, 3) catalyst to convert nitrogen oxides into nitrogen gas with the presence of urea, 4) a muffler to reduce the noise transmissions from the lawn mower.

Expected Results:

The innovative prototype is expected to reduce both pollutants and noise emissions from the lawn mower. The original NOx-Out prototype showed a reduction in nitrogen oxides (NOx), carbon monoxide (CO) and particulate matter (PM) emissions from a traditional four-stroke lawn mower exhaust by 67%, 87% and 44% respectively. Once the prototype is fully tested, prototypes will be implemented onto lawn mowers on campus to aid in reaching zero emissions by 2020.

Supplemental Keywords:

air quality, innovative technology, gasoline-powered lawn mower, air pollution control, criteria pollutant, human welfare, sustainability, green landscaping

Progress and Final Reports:

  • Final