Zimbabwe

TABLE 4.17 BSFL, Meal, and Frass Production from Wheat Output

Substrates, Zimbabwe

Waste/loss component Total waste/ loss (tons) BSFL (tons) BSFL meal (tons) Frass (tons) High Low High Low High Low

straw 31,874 9,562 3,187 3,251 1,084 9,562 3,187 postharvest losses 5,976 1,793 598 610 203 1,793 598 process waste 3,598 1,079 360 367 122 1,079 360 Consumption waste 247 74 25 25 8 74 25 TOTAL 41,696 12,509 4,170 4,253 1,418 12,509 4,170

Source: Original table for this publication. Note: BSFL = black soldier fly larvae; high = 30 percent conversion; low = 10 percent conversion.

3. Humans consume approximately 10 percent, or 174 kg/ha, of the marketable wheat, and livestock consume 5 percent, or 87 kg/ha, leaving 1,482 kg/ ha of wheat for processing. 4. A wheat kernel comprises three parts: endosperm, which makes up approximately 83 percent of the kernel; bran, which makes up 14.5 percent of the kernel; and germ, which makes up 2.5 percent of the kernel (BAKERpedia 2020). The wheat milling process separates the bran and germ from the endosperm, which is used to make flour. Endosperm extraction ranges from 72 to 76 percent of the kernel’s weight, but the model uses 74 percent.

This means that endosperm extraction leaves approximately 9 percent of the kernel’s weight as waste. This waste, along with the bran and germ byproducts, results in 27 percent of the kernel’s weight available for BSFL.

Bran and germ are often burned or otherwise discarded despite both having nutritional value for humans and livestock. This model assumes that 20 percent of bran and germ will be available as BSFL substrate. Given these percentages, the total potential available wheat processing–derived substrate is calculated to be the following: • Endosperm waste: 9 percent of kernel weight => 0.09*1,482 kg/ha = 133 kg/ha • Germ: 2.5 percent of kernel weight => 0.029*1,482*0.2 = 9 kg/ha • Bran: 14.5 percent of kernel weight => 0.145*1,482*0.2 = 43 kg/ha • Total available for BSFL substrate: 185 kg/ha. 5. According to the FAO, consumption waste for cereals in Sub-Saharan

Africa is roughly 1 percent. One percent of the approximately 1,297 kg/ha of milled wheat produced in processing equates to 13 kg/ha of consumption waste available as BSFL substrate (FAO 2011).

Economic and Social Benefits Associated with BSF Breeding

This subsection calculates the amount and value of protein and frass produced by BSFL from the various crop substrates and some of the environmental and employment benefits of BSF breeding. Table 4.18 summarizes the potential quantities of dry meal and frass derived from BSFL using wastes of the five crops as substrates. The table suggests that, on a per-hectare basis, sugarcane is the most favorable of the five crops for converting waste to BSFL and, eventually, to dry meal and frass. Maize provides the least waste that potentially can be used for BSF breeding. Per hectare, sugarcane produces more than 56 times the total waste as maize and greater than 18 times the total waste produced by wheat, the second leading crop in terms of per unit area waste production. The theoretical figures in table 4.18 assume full waste recovery at each step in the waste stream for all farms across Zimbabwe, but this is not realistic, nor is it realistic to assume that all farmers across the country will engage in BSF breeding. Even if a farmer captures 100 percent of the crop-related wastes for any or all of the five crops, the wastes can be used for purposes other than BSF breeding. Therefore, it would be unlikely that all the wastes would be used as BSFL substrate. As such, determining which crop has the most waste available for BSFL substrate would require knowing what percentages of each crop’s wastes are diverted for other uses, but this may vary depending on location.

Protein

BSFL are an excellent source of protein for livestock and are profitable for farmers. The dry meal weight rendered from wet (live) larvae will be 34 percent of the weight of the wet larvae, or rather 34 percent wet larvae to dry meal conversion rate. The crude protein content of the dry meal is about 40 to 50 percent.13 This compares favorably with the protein content of soy cake (47 to 49 percent) (Heuzé, Tran, and Kaushik 2020) and groundnut cake (45 to 60 percent) (Purohit and Rajyalakshmi 2011). Table 4.19 exhibits the protein demands of livestock in Zimbabwe, specifically, pigs, goats, chickens, and fish from aquaculture. Table 4.20 shows the crude protein derived from BSFL on the basis of the various crop residue substrates. BSFL dry meal meets between 6 percent (38,834 tons) and 17 percent (116,502 tons) of Zimbabwe’s crude protein demand when comparing livestock’s protein demand with BSFLderived protein supply.14 The model can also approximate the monetary value of BSFL crude protein by examining the international commodity price of soybean meal, which has similar protein content (48 percent) as BSFL. If the retail price of BSFL meal is assumed to be roughly the same as that of soybean meal (US$323 per ton),15 the retail value of BSFL protein falls in the approximate range of US$12.55 million (for 38,834 tons) to US$37.65 million (for 166,502 tons) (table 4.21).

BSFL can cover protein demands for livestock. The BSFL crude protein totals used in this model assume the nationwide theoretical high values, which