Fuel from manure and food waste offers diesel efficiency

Researchers have claimed a “huge step” towards more sustainable fuels for existing diesel engines after successfully converting waste into a fuel with the same combustion efficiency and emissions profile as diesel.

The team from the University of Illinois used manure and food waste to create the fuel, which could be blended with diesel to help tackle the huge amounts of waste from urbanisation and increased farming. 

The US produces 79m tonnes of wet biowaste from food processing and animal production every year, with that number set to rise. High water content has previously been a barrier to using it as fuel, however, with almost as much energy required to dry the waste as would be extracted from it. 

To tackle the issue, the researchers used hydrothermal liquefaction. The process uses water as the reaction medium and converts even non-fatty waste components into biocrude oil, which can be further processed into engine fuels.

Previous studies have struggled to distill the biocrude into usable fuel, the researchers said, so they combined distillation with a process called esterification. The technique converted the most promising fractions of distilled biocrude into a liquid fuel that could be blended with diesel. With a blend containing 10-20% biofuel, the power output from the fuel was 96-100% of diesel, with similar pollutant emissions.

“The demonstration that fuels produced from wet waste can be used in engines is a huge step forward for the development of sustainable liquid fuels,” said co-author Brajendra K. Sharma.

Many governments around the world are introducing restrictions or total bans on the sale of new diesel vehicles, but it will nonetheless still be used for many industrial and agricultural vehicles. Supplementing diesel with a sustainable biofuel could be an attractive use for growing amounts of biowaste.

The team is now building a pilot-scale reactor with the potential to process one tonne of biowaste and produce 136l of biocrude oil per day.

The research was published in Nature Sustainability.