3.9 Feed Conversion Rates of Various Insect and Livestock Species

management is a challenge.11 In such cases, it is still important to avoid waste substrates with high levels of heavy metals. Using BSFL for feed and composting can reduce GHG emissions. A study in Indonesia found that composting segregated kitchen waste with BSFL can reduce direct CO2-eq emissions by 47 times (Mertenat, Diener, and Zurbrügg 2019). It also found that organic waste composting with BSFL as opposed to open-air composting reduces GWP by half.

Farmed insect species convert the organic substrate they feed on very efficiently compared with conventional livestock. The growth efficiency of farmed animals is expressed as the FCR. The FCR evaluates how much feed substrate is needed to produce 1 kg of meat. Insect species have the potential of efficient growth with an FCR as low as 1.4. This is well below the FCR for chicken, which has the most optimized FCR among traditional livestock species (table 3.9). Insects can efficiently convert low-grade organic waste into high-quality fat and protein. When insects are dried, up to 70 percent of their dry matter is protein

TABLE 3.9 Feed Conversion Rates of Various Insect and Livestock

Species

Species Feed conversion ratio Description of the farming system Reference

Cricket (Acheta domestica and Gryllus bimaculatus) house cricket (Acheta domesticus) Black soldier fly (Hermetia illucens) mealworm (Tenebrio molitor) swine 1.82 sheltered, open-walled system (thailand) halloran et al. 2017

2.3–6.1 experiments in a laboratory setting oonincx et al. 2015

1.4–2.6 experiments in a laboratory setting 3.8–19.1 experiments in a laboratory setting 4.04 national average (united states) broiler chicken 2.68 national average (united states) layer chicken 2.26 national average (united states) turkey 3.58 national average (united states) beef cow 23.5 national average (united states)

Striped catfish (Pangasianodon hypophthalmus) 1.57 intensive farming systems (vietnam) hasan and soto 2017

Source: Original table for this publication. mekonnen et al. 2019

(Rumpold and Schluter 2013) and, similar to other foods of animal origin, the protein is rich in essential amino acids (Rumpold and Schluter 2013; Makkar et al. 2014). Therefore, insects contribute high protein quality and important micronutrients to human diets (Rumpold and Schluter 2013) and animal feeds (Makkar et al. 2014).

Insects’ low FCR is partly why insect farming has fewer climate and environmental impacts than traditional livestock farming. A low FCR indicates higher efficiency in producing a kilogram of meat, or milk in the case of dairy cows. The FCR is calculated in different ways for different animals, so caution should be taken when directly comparing different animals’ FCRs. Table 3.9 shows the FCR values for different insect production systems. The table indicates promising efficiencies from insect farming despite insect farming systems being in their infancy and not yet fully optimized. For example, livestock species with a long history of animal husbandry have significantly decreased their FCRs over time; between 1944 and 2017, the FCR of dairy cows for milk production dropped by 77 percent (Mekonnen et al. 2019).

BSFL have the biological capacity for efficient conversion of a broad range of organic substrates to food and protein (Li et al. 2011; St-Hilaire et al. 2007; Tinder et al. 2017; Chen et al. 2019). These substrates include vegetable waste, mixed household waste, animal waste such as manure or slaughter offal, and industrial waste from breweries, wineries, or other industries (table 3.10). These wastes and by-products increase larval performance and nutritional composition (Meneguz et al. 2018). The type of feed substrate can also affect the BSFL’s growth rate and nutritional composition. Higher protein in the feed substrate generally translates into greater growth and protein content of the larvae. For example, brewery waste contributes low-grade protein to the feed substrate, which converts into high-quality protein in the BSFL. Studies show that even small amounts of brewery waste were effective at increasing larval performance (Meneguz et al. 2018). A Ghanaian farmer said, “The hatched larvae of the black soldier fly help to break down domestic and industrial waste and contribute to keeping our communities clean and safe for all.”

Insects can reduce organic waste in urban settings by converting it into highquality protein (Nyakeri et al. 2019; Nyakeri et al. 2016, 2017). This is especially valuable in high-density urban areas with poor sanitation and human waste management. In these areas, insects address health problems by reducing the amount of human waste (Banks, Gibson, and Cameron 2014). In Africa, two companies, BioCycle and Sanergy, use BSFL to break down human waste and create animal feed. The larvae that feed on this waste are always heat treated to kill any pathogens prior to using them for animal feed.

Insects convert all sorts of waste substrates into protein. Three-quarters of farms in the farm-level survey used mixed organic waste substrates. Nearly half (43 percent) of the farmers using organic waste substrates used household waste, such as vegetable peels and similar waste. Table 3.10 shows the types of substrates farms use to feed domesticated insects. The high diversity of substrates demonstrates the potential of insects to convert all sorts of low-value organic