Table 1.
Selected physical and chemical characteristics of brewery spent grain, biochar and gypsum used in the experiments.
Fig 1.
Effect of biochar and gypsum amendments on wet (a) and dry (b) black soldier fly larval yields during experiment set 1 and 2.
Key: 5Gypsum, 10Gypsum, 15Gypsum = substrate amended with 5, 10 and 15% gypsum, respectively, 5Biochar, 10Biochar, 15Biochar and 20Biochar = substrate amended with 5, 10, 15 and 20% biochar, respectively, control = unamended substrate.
Table 2.
Waste degradation, biomass conversion rates and frass fertilizer yield by black soldier fly larvae reared on biochar and gypsum amended substrates.
Table 3.
Effect of biochar and gypsum amendments on substrate nitrogen retention and uptake by black soldier fly larvae.
Fig 2.
Changes in temperature (a), pH (b) and electrical conductivity (c) during experiment set 1 of BSF frass composting.
Key: 5Gypsum, 10Gypsum, 15Gypsum = substrate amended with 5, 10 and 15% gypsum, respectively, 5Biochar, 10Biochar, 15Biochar and 20Biochar = substrate amended with 5, 10, 15 and 20% biochar, respectively, control = unamended substrate.
Fig 3.
Changes in temperature (a), pH (b) and electrical conductivity (c) during experiment set 2 of BSF frass composting.
Key: 5Gypsum, 10Gypsum, 15Gypsum = substrate amended with 5, 10 and 15% gypsum, respectively, 5Biochar, 10Biochar, 15Biochar and 20Biochar = substrate amended with 5, 10, 15 and 20% biochar, respectively, control = unamended substrate.
Fig 4.
Trends of ammonium (a and c) and nitrate (b and d) concentrations during BSF frass composting.
Key: 5Gypsum, 10Gypsum, 15Gypsum = substrate amended with 5, 10 and 15% gypsum, respectively, 5Biochar, 10Biochar, 15Biochar and 20Biochar = substrate amended with 5, 10, 15 and 20% biochar, respectively, control = unamended substrate.
Fig 5.
Changes in concentrations of total organic carbon (a), nitrogen (b), phosphorus (c) and potassium (d) during experiment set 1 of BSF frass composting.
Key: 5Gypsum, 10Gypsum, 15Gypsum = substrate amended with 5, 10 and 15% gypsum, respectively, 5Biochar, 10Biochar, 15Biochar and 20Biochar = substrate amended with 5, 10, 15 and 20% biochar, respectively, control = unamended substrate.
Fig 6.
Changes in concentrations of total organic carbon (a), nitrogen (b), phosphorus (c) and potassium (d) during experiment set 2 of BSF frass composting.
Key: 5Gypsum, 10Gypsum, 15Gypsum = substrate amended with 5, 10 and 15% gypsum, respectively, 5Biochar, 10Biochar, 15Biochar and 20Biochar = substrate amended with 5, 10, 15 and 20% biochar, respectively, control = unamended substrate.
Table 4.
Ratios of total organic carbon to total nitrogen contents at selected periods during frass composting.
Table 5.
Concentrations of nitrogen (N), phosphorus (P) and potassium (K) in amended mature black soldier fly frass fertilizers.
Table 6.
Seed germination and germination indices of mature frass fertilizers generated from substrates amended with biochar and gypsum.
Fig 7.
Bi-plot graphs based on PC analysis of parameters that measure frass fertilizer quality (a) and black soldier fly larval yields (b) as a function of the different biochar and gypsum amendments for nitrogen conservation in the rearing substrates.
Key: NO3 = nitrate nitrogen, NH4 ammonium nitrogen, N = total nitrogen, K = total potassium, P = total phosphorus, C:N = carbon to nitrogen ratio, EC = electrical conductivity, Temp = temperature, WSC = water soluble carbon, iN = initial nitrogen content in the rearing substrates, Nbsf = nitrogen accumulated in BSF larval biomass, Nret = nitrogen retained in the frass, WR = waste degradation, BCR = biomass conversion rate, FLY = wet BSF larval yield, DLY = dry BSF larval yield. 5Gypsum, 10Gypsum, 15Gypsum = substrate amended with 5, 10 and 15% gypsum, respectively, 5Biochar, 10Biochar, 15Biochar and 20Biochar = substrate amended with 5, 10, 15 and 20% biochar, respectively, control = unamended substrate.