TABLE 4.17 BSFL, Meal, and Frass Production from Wheat Output Substrates, Zimbabwe Waste/loss Total component waste/ loss (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 TOTAL
BSFL (tons)
BSFL meal (tons)
Frass (tons)
247
74
25
25
8
74
25
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). Mainstreaming Insect Farming
157
