In the past few years, biodiesel production from insect oil is gaining interest in the scientific community (Leung et al. 2012; Li et al. 2011a, b). This technology is based on the fact that many insects possess a lipid body rich in monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids (Rumpold and Schluter 2013). MUFA are among the preferred fatty acids for biodiesel production due to their ability to improve the engine behavior under cold weather conditions, besides bio­diesel oxidative stability (Pinzi et al. 2009).

The amount of lipids and the fatty acid composition of the insect depend not only on the species but also on the diet used to grow it (Manzano-Agugliaro et al. 2012; Belluco et al. 2013) (Table 1). For the selection of suitable insects to produce fats to be used as biodiesel feedstock, the following parameters should be considered: fat content, duration of the life cycle, requirements of space to grow, reproductive capacity, and low-cost feeding (Manzano-Agugliaro et al. 2012). In the search of more economical nourishment, it is important to select insects that are able to consume waste both to produce oil and for recycling purposes. Therefore, the insect Hermetia illucens, also known as black soldier fly (BSF), has been investigated as a source of oil for biodiesel production (Li et al. 2011b; Zheng et al. 2012a) and also for its capability for waste manage­ment (St-Hilaire et al. 2007). Li et al. (2011b) used BSF larvae for the bioconver­sion of diary manure on biodiesel and sugar. Results showed a consumption of 78 % of the initial value of manure (1,248.6 g of fresh manure) in 21 days. They produced 15.8 g of biodiesel and 96.2 g of sugar from 70.8 g dry BSF larvae. Other wastes, i. e., lignocellulosic materials, have been tested. Zheng et al. (2012a) analyzed different mixtures of restaurant solid waste (RSW), rice straw, and Rid-X (bacteria that facilitate the breakdown of the solid organic wastes). Considering a ratio of 7:3 (RSW/rice straw) plus 0.35 % v/v Rid-X, they achieved 35.6 % of biodiesel per dry insect biomass. Animal waste is another residue that may cause health hazards and environmental pollution. From this group, cattle, pig, and chicken manure have been used to grow BSF larvae (Li et al. 2011a). The highest BSF larvae growth (327.6 g) resulted in 98.5 g of crude fat and 91.4 g of biodiesel.

In another study, Chrysomya megacephaly, a necrophagous blowfly, during its larvae development, was fed with restaurant garbage for 5 days and achieved an oil content in a range from 24.40 to 26.29 % (Li et al. 2012). But the most impor­tant finding is the oil acid value, lower than that of most insects and close to that of vegetable oils (Table 2).

Regarding the production of fatty acid methyl esters (FAME) from insect oil, a two-step process has been implemented in most cases: acid esterification (due to the high acidity of the oil) followed by basic transesterification. Reaction param­eters including temperature, amount of catalyst, time, and methanol-to-oil molar ratio were optimized (Table 3). Results showed that insect oil-based biodiesel properties fulfilled the ASTM D6751 and EN 14214 standards in terms of cetane number, density, flash point, water content, (Table 4), although only a few met the European standard methyl esters content (>96.5 %), kinematic viscosity, alcohol content, and both the acid number value and the oxidation stability required by both standards.