Biodiesel is a cleaner fuel alternative to petroleum diesel, but making it still creates pollution—especially harmful wastewater and carbon dioxide (CO₂).
Now, a team of researchers from the University of Michigan is working on a new way to treat that wastewater while capturing CO₂ and creating useful products, like green fuels and chemicals.
When biodiesel is made, fats from things like vegetable oil, animal fat, or used cooking grease are turned into fuel through a process called transesterification.
This process uses alcohol (usually methanol) and a catalyst to break fat molecules into two parts: fatty acid esters, which become biodiesel, and glycerol, a waste product.
Glycerol ends up in the wastewater, and if left untreated, it can harm the environment by lowering oxygen in the water, which can kill fish and other wildlife.
Traditionally, treatment methods focus on removing the glycerol.
But now, scientists are trying to recover valuable materials from the wastewater, which could help reduce the cost of making biodiesel.
One method under development is called electrochemical CO₂ reduction (eCO₂R). It uses electricity to turn CO₂ into useful chemicals. However, this method typically requires very pure water and expensive materials like precious metals, making it hard to use on a large scale.
To make the process more affordable and energy-efficient, researchers are testing a different method: the electrochemical glycerol redox reaction (GOR).
This approach uses glycerol’s natural ability to exchange electrons easily, which lowers the energy needed for the reaction by 23% to 53%, depending on the materials used.
The type of catalyst used is important. Nickel is especially promising because it’s cheap, easy to make, and can help produce formate—a chemical used in food processing and worth up to $146 per liter.
Combining GOR with CO₂ capture could create a single system that treats wastewater, reduces CO₂, and makes valuable chemicals all at once. But there’s still work to be done before this can be used in real-world biodiesel factories.
One big challenge is making sure the nickel catalyst stays effective over time. In the study, researchers created a fake version of biodiesel wastewater and ran it through a special flow cell with nickel and platinum electrodes. After just 24 hours, the system lost 99.7% of its power, mainly because particles blocked the nickel electrode.
The team says regular cleaning will be needed to keep the system working. Their study also gives scientists a new way to test how long catalysts can last, helping future designs become more durable.
This research is an early but important step toward greener biodiesel production that turns waste into something useful.
