Researchers in Nigeria have reviewed a technology that mixes small amounts of water into diesel fuel to reduce emissions. This water-in-diesel emulsion, or WiDE, lowers nitrogen oxide and particulate matter by more than 60 percent without needing engine modifications. The approach may also boost fuel efficiency in some cases.
Diesel engines power much of the world's transportation, agriculture, and industry due to their reliability and power. However, they contribute significantly to air pollution through emissions of nitrogen oxides and particulate matter, which are associated with smog, respiratory issues, and climate change. Existing solutions like catalytic converters and filters help but add cost and complexity.
A team from the Federal University of Technology Owerri in Nigeria has analyzed global studies on water-in-diesel emulsion (WiDE) technology as a simpler alternative. WiDE involves blending tiny water droplets into diesel using surfactants to maintain stability for up to 60 days. During combustion, the water vaporizes quickly, causing micro-explosions that enhance fuel-air mixing and reduce peak temperatures.
This process leads to substantial emission cuts: nitrogen oxide levels fell by as much as 67 percent, and particulate matter by up to 68 percent, compared to standard diesel. Some experiments also showed gains in brake thermal efficiency, meaning better conversion of fuel to mechanical power.
"Water-in-diesel emulsions are a practical and cost-effective way to make diesel engines cleaner," said lead author Dr. Chukwuemeka Fortunatus Nnadozie. "Because the technology does not require redesigning the engine, it offers an immediate path toward lower emissions in developing and developed countries alike."
The review highlights the role of surfactants, noting that combinations of multiple types yield the best stability and combustion quality. While promising, the researchers call for further work on optimizing surfactants and assessing long-term engine impacts.
WiDE could complement other technologies, such as biodiesel and advanced controls. "This technology can bridge the gap between conventional diesel use and a cleaner energy future," said co-author Professor Emeka Emmanuel Oguzie. "With proper formulation and testing, it could become an important part of sustainable transportation and industrial power systems."
The findings appear in Carbon Research (2025; 4(1)), based on materials from Shenyang Agricultural University.
