Production of Biodiesel from Vietnamese Waste Coffee Beans: Biofuel Yield, Saturation and Stability are All Elevated Compared with Conventional Coffee Biodiesel

The suitability of biodiesel produced from spent Vietnamese coffee was examined. Previous work shows that the geographical origin of coffee beans has little effect on the composition and physical properties of the biodiesel produced Jenkins et al. [1]. Vietnamese coffee, however, is roasted in a range of fats and oils for flavour enhancement and therefore has a unique fatty acid profile. The oil yield and biodiesel properties of three Vietnamese coffees were assessed and compared to a coffee of more typical composition—Colombian—and traditional biodiesel feedstocks (rapeseed, sunflower and palm). The oil yield from fresh Vietnamese coffee was higher (12.0–14.0 %) than Colombian coffee (9.3 %), while the oil yield from spent Vietnamese coffee (9.3–10.4 %) was comparable to the Colombian coffee (9.5 %). The unsaponifiable matter was only present in low levels in the Vietnamese coffee (1.9–4.9 %) compared to Colombian coffee (30.4 % fresh, 21.4 % spent). Vietnamese coffee biodiesel was more saturated than Columbian coffee biodiesel. It was therefore more viscous and had a higher pour point than the Colombian coffee, and possessed properties more akin to palm biodiesel. Vietnamese coffee biodiesel would therefore be a suitable feedstock for use locally due to the more suitable climate and compatibility with the palm feedstock that is currently used.