protein derived from the dry meal8 against the protein requirements of certain livestock: pigs, goats, chickens, and fish from aquaculture. The model was extended beyond Zimbabwe to analyze Africa as a whole and 10 additional African countries individually. The analysis for all of Africa included the same five crops studied in Zimbabwe—maize, wheat, soybean, groundnut, and sugarcane—to determine the potential production volume of BSFL and frass and the impact of each. The assessment of individual African countries included the 10 countries with the largest agricultural economies on the continent. These are, from largest to 10th largest, Nigeria, Kenya, the Arab Republic of Egypt, Ethiopia, Algeria, Tanzania, Morocco, Sudan, Ghana, and Angola. The analysis added cassava to the list of crops to reflect the agriculture sector in the 10 countries, although the analysis for each country was limited to only five of the six crops—the five with the highest production tonnage for each country (annex 4A provides details of the analysis and the full results). Achieving maximum conversion rates depends on how substrates are prepared. Crop residues, for example, may be fibrous and may not be fully consumed by BSFL. Therefore, grinding and fermenting fibrous materials before feeding them to BSFL allows the BSFL to consume them more completely, thus raising the substrate-to-BSFL conversion. Considering that BSF breeding is a nascent industry, more studies are required to establish best practices for crop waste preparation, determine crop-specific conversion rate estimates, and estimate more accurately BSFL’s final frass and crude protein outputs. Other wastes can be used as BSFL substrates but are not included in the model. These substrates include crops other than the five used in the modeling, including various types of processing waste. For example, rotten vegetables are ideal for BSFL consumption and can be collected from vegetable processing plants. Brewer spent grains (BSG) are another potential substrate for BSFL. BSG are an excellent source of crude protein for livestock and are in high demand for that reason. It is more efficient to feed BSG directly to livestock than to convert them to protein through BSFL. However, the shelf life of BSG is only a day or two at ambient temperatures or two or three days if kept refrigerated. Spoiled BSG should not be fed to livestock, but the
TABLE 4.7 BSF-Related Conversion Factors BSFL to dry meal 34%
Meal crude protein content
All other conversion factorsa
40%
Low
High
10%
30%
Source: Original table for this publication, using J. K. Tomberlin, personal communication. Note: BSF = black soldier fly; BSFL = black soldier fly larvae. a. Conversions of all crop-related wastes to BSFL and all crop-related wastes to frass.
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Insect and Hydroponic Farming in Africa
