A Spongey Catalyst Transforms Cooking Oil into Biodiesel

Biodiesel, a low-carbon liquid fuel comprised of fatty acid methyl esters, is a sustainable alternative to fossil fuels. It is typically derived from feedstocks such as oil-rich plants, algae, and food waste. The chemical makeup of biodiesel is similar to regular diesel, but burning biodiesel ultimately creates fewer greenhouse gas emissions.

Industrial facilities produce biodiesel by reacting triacyl-glycerides (TAG) contained in the oil-rich feedstock with light alcohols. This process is catalyzed by liquid bases such as sodium hydroxide or sodium methoxide, but separating these chemicals from the final product can be challenging and energy-intensive.

Thus, biodiesel production generates large quantities of undesired soaps and aqueous waste. Moreover, leftover catalyst may contaminate the biodiesel due to incomplete separation of the final product and catalyst. Most commercial engines can only handle extremely pure fuels with as little as 1–2% contaminants, as an impure fuel can corrode engines and fuel lines.

Many of the available liquid catalysts used for biodiesel production are incompatible with waste cooking oils — a copious, low-grade feedstock that has a high concentration of free fatty acid (FFA) impurities. At RMIT Univ. in Australia, researchers have developed a novel catalyst that can efficiently convert cooking oil into biodiesel and is easily recovered from the final product.

The team fabricated the solid catalyst from a ceramic sponge containing interconnected small and large pore networks. Active sites...