Technology for small-engine emissions reduction

Swiss researchers used a modern four-stroke engine in conjunction with a commercially available catalytic converter and special gasoline to develop a significantly cleaner-running walk-behind mower.

Small-equipment spark-ignition engines have come under increasing scrutiny for the high specific exhaust-gas emissions they produce. Table 1 shows many current and future regulatory emissions levels such as Swiss off-road inventory, German Environment Agency (UBA) tests, and the first limits enacted by California in 1996. Despite the regulations in California, lawnmower engines there have emissions 100 times greater than those of modern automobiles. However, small-engine emissions can be reduced with technology developed by a team of Swiss researchers, the results of which are shown in the table as Frey/EMPA.

The CO and HC emissions contributions of small engines to total Switzerland emissions have been on the increase in comparison to those from road vehicles, the main sources being from the agriculture and horticulture sectors. Because the relative proportion of these emissions is forecast to substantially increase, in 1998 the Swiss environmental protection agency (BUWAL) enacted a program to curtail these emissions in a revised clean air act.