CINCINNATI — Researchers are developing emissions control systems that could someday replace the selective catalytic reduction setups now found on diesel-powered medium-duty trucks.

Their work is driven, in part, by concerns that diesel exhaust fluid, the urea-based solution used by all SCR systems, presents problems that alternative technologies could overcome.

“DEF is extremely peculiar. It is a harsh and aggressive liquid,” said Richard Petti, the chief operating officer of Wema System, a Norwegian firm that makes components for SCR systems. Petti and others discussed the engineering challenges of working with DEF and potential alternatives during a conference on diesel emissions and DEF hosted here in October by market analysis firm Integer Research Ltd., London.

DEF is mainly distilled water — more than 65% — and dissolved urea, a nitrogen-carbon-hydrogen-oxygen compound making up 32.5%. It is a necessary ingredient for reducing nitrogen oxide emissions in a truck’s SCR system. And that system has become the uncontested method of emissions compliance for North American medium-and heavy-duty trucks.