The energy usage and environmental impact assessment of spent coffee grounds biodiesel production by an in-situ transesterification process

Abstract

Spent coffee grounds (SCG) waste has been drawing attentions in the biodiesel industry due to the promising of oil content. However, SCG sources is very disperse and requires a transportation system. Moreover, a complexity of oil extraction steps using hazardous n-hexane can hinder the SCG biodiesel promotion. Therefore, an alternative approach using in-situ transesterification (in-situ TE), an n-hexane free process, was introduced for producing biodiesel at an on-site SCG source. Life cycle assessment was performed to compare the energy usage and environmental impacts between a conventional process, which requires transportation and n-hexane, and an on-site in-situ TE process. Producing SCG biodiesel using conventional process required 43% less energy and produced fewer environmental impacts than those of the on-site in-situ TE. Much of the difference was attributable to 73% of the energy in the in-situ TE being consumed in methanol recovery. Nevertheless, the in-situ TE process gained better scores in terms of respiratory organs and land occupation. A sensitivity analysis of energy usage on transportation distances and fuel consumption rates suggested that an on-site in-situ TE process could be viewed as more favorable once the transportation distance is greater than 180km with 7km/L of fuel consumption rate.