Variable oil properties and biomethane production of grease trap waste derived from different resources

- Evaluated variation in fuel characteristics of restaurant grease trap waste (GTW).
- Acid value (AV) and saturation degree of oil have more than 50% standard deviation.
- All types of de-oiled GTW have a high bio-methane yield.
- Oils can be classified according to AV and chemical stability.

Restaurant grease trap waste (GTW) is a potentially feasible energy source that can be used as an alternative to liquid fossil fuels and natural gas. However, GTW must be collected from many different resources for energy production because restaurants in Japan only produce an average of 486 kg GTW per year. This study investigated the variation in oil properties and methane generation potential of 44 GTW samples from 13 types of restaurants during different seasons. The GTW samples had high variation in oil content and oil properties. Biofuel oil was extracted from most GTW samples at a high efficiency (more than 80 wt%). In contrast, the methane yield varied little among de-oiled GTW samples. All types of GTWs are potential sources of biomethane generation. GTW samples are classified into five major oil property clusters according to solid chemical stability. Oil properties depend little on the season and heavily on the restaurant type.