Zimbabwe

TABLE 4.11 BSFL, Meal, and Frass Production from Sugarcane

Output Substrates, Zimbabwe

Waste/loss component Total waste/ loss (tons) BSFL (tons) BSFL meal (tons)

Frass (tons) High Low High Low High Low

trash 542,733 162,820 54,273 55,359 18,453 162,820 54,273 postharvest losses 36,182 10,855 3,618 3,691 1,230 10,855 3,618 process waste 1,156,998 347,099 115,700 118,014 39,338 347,099 115,700 TOTAL 1,735,913 520,774 173,591 177,063 59,021 520,774 173,591

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

4. Bagasse and filter mud are the key components of sugarcane processing waste. Filter mud amounts to 1 to 9 percent of output, although this model uses a conservative 2 percent. Bagasse, the fibrous remains of crushed and juice-extracted sugarcane, amounts to 30 to 34 percent of output and the model uses 32 percent (Nikodinovic-Runic et al. 2013).

Bagasse is used as fuel to generate steam for processing sugarcane into sugar. According to the FAO, 70 percent of bagasse can be used to generate steam, leaving 30 percent for substrate. However, this model assumes that all bagasse is substrate, although a cost-benefit comparison would be necessary to determine whether the best use of bagasse is as a fuel or substrate. 5. Additional sugarcane losses during distribution and consumption are not considered for this model.

Soybean

Figure 4.12 shows the food supply chain and associated waste stream for soybean in Zimbabwe. The following analysis determines BSFL meal and frass production based on the five-year (2013–17) averages for total annual soybean production (52,504 tons) and harvested area (43,713 ha). The numbered bullets below show the kilogram per hectare calculations for each type of soybeanassociated waste. These are then multiplied by the total area under cultivation (hectares) and divided by 1,000 (kg/ton) to determine the total tons per hectare per waste. Table 4.12 summarizes the total soybean-derived wastes recoverable and suitable as substrates for BSF breeding. Table 4.13 applies the 10 and 30 percent conversion rates to the wastes in table 4.12 to calculate the rate of converting soybean wastes to BSFL meal and frass.