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Recycling of coffee pulp by Hermetia illucens (Diptera: Stratiomyidae) larvae
Biological Wastes 33 (1990) 307-310
Short Communication Recycling of Coffee Pulp by Hermetia illucens (Diptera: Stratiomyidae) Larvae
ABSTRACT The digestion of coffee pulp by larvae of the soldier fly Hermetia illucens (L.) was studied in a small-scale experiment to obtain preliminary data pertaining to this method of treating the waste. After 13 days the coffee pulp was converted into a slurry-like material and lost 29.8% of the initial dry matter, the pH increasedfrom 7"6 to 8"85, the odour was reduced significantly, and the total weight of larvae was 6.2 times that at the beginning. It was concluded that H. illucens larvae could be utilized in recycling coffee pulp under controlled conditions.
INTRODUCTION Insect larvae growing on decaying materials can be thought of as agents for biological stabilization of noxious organic residues and as a potential source of protein usable in animal production. The first approach has been investigated for house fly larvae digesting fresh poultry manure (Miller et al., 1974) and beef cattle waste inoculated with Hermetia illucens (L.) larvae (Booram et al., 1977), whereas the latter approach has been studied by feeding swine and poultry on ground H. illucens larvae harvested from beef and swine feces (Hale, 1973; Booram et al., 1977; Newton et al., 1977). Larvae of H. illucens are also able to grow on coffee pulp, a very polluting waste generated in coffee-producing zones throughout the tropics. In a previous work (Lard+, 1989), larval populations of this species ranging from 165 to 625 individuals were found in sample volumes, 5.3 dm 3 each, taken 307 Biological Wastes 0269-7483/90/$03-50 © 1990 Elsevier Science Publishers Ltd, England. Printed in Great Britain
308
Gerardo Lard~
from a coffee-pulp bed, which is an indication of the potential that the larvae have as organisms for recycling coffee pulp; however, collecting the larvae from the decaying material was found to be a troublesome task under the management conditions employed. The experiment presented here was carried out to obtain preliminary data mainly pertaining to the digestion of coffee pulp by H. illucens larvae but also to their growth on this waste, since they can be utilized as a supplemental feed for animals.
METHODS Fresh coffee pulp (CP) was stored in airtight plastic bags for six months. Under this anaerobic condition CP underwent an alteration very similar to that occurring during the ensilage of much larger amounts. This procedure was followed bearing in mind that fresh CP is produced seasonally (3-4 months a year) and, hence, the use of CP preserved by ensiling would probably be necessary to keep a continuous recycling with larvae. To obtain an inoculum of larvae, the plastic bags were slightly opened so as to fully expose to the air only a small portion of the CP. After an exposure of 27 days, seven young larvae ofH. illucens collected from the bags were put in a glass Petri dish (10cm diameter, 2"5cm high) filled with CP from the inner zone of the bags where aerobic decomposition was slowest. The study consisted of just one experiment conducted at room temperature, 24"9 ___ 1.2°C. For a period of 13 days changes in the substrate were observed, and the larvae were individually weighed and their length measured at the same time so as to correlate these two body characteristics. Moisture was determined by drying at 105°C to constant weight and pH potentiometrically.
RESULTS A N D DISCUSSION Table 1 summarizes the results from the experiment. The progressive decaying of CP showed up in the increase o f p H as well as in the total solids reduction. The loss of dry matter was not much above that (20.3 and 21-7%) reported by Booram et al. (1977) for a period of 14 days. The texture of the substrate changed noticeably from the normal appearance of CP to a slurry-like material, and the odour was reduced significantly, indicating that H. illucens larvae could be utilized effectively in the treatment of anaerobically stored CP under controlled conditions. Miller et al. (1974) found comparable alterations of the substrate since in this
Recycling of coffee pulp by Hermetia iUucens larvae
309
TABLE 1
Changes in Substrate and Growth of Hermetia illucens Larvae Decomposing Coffee Pulp °
on
Time elapsed
Substrate weight (g) Moisture (g kg-1) pH Dry matter lost (%)b Larva length (ram)c Larva weight (rag)c Total larval weight (g) Overall growth rate (mg day-~)d Gain in weightfrs lost (gg-1) Gain in weight/initial TS (mg g - 1)
0 days
13 days
79.6 877.0 7.6 0 8.7 _+ 1.2 (7) 23"5 _+ 6' 1 (7) 0.165 __ _ 0
64.8 894.0 8.85 29"8 17.6 _+ 1.1 (7) 147.0 -t- 21-7 (7) 1.029 66"5 0.296 88.3
° Wet matter unless noted otherwise. b (Initial TS - Final TS)/initial TS. c Mean +_standard deviation (number of observations). a Gain in weight/time elapsed. TS, total solids.
180 E t60
~140 ~120
100 8( eo
6(
•
4( 2( 5
10
I
15
I
20
LENGTH (mm) Fig. 1. Relationship between length and weight (wet basis) of ttermetia illucens larvae grown on decomposing coffee pulp. Regression function: y = 0.051 038 x 2"783°29 (r = 0"991). ( 0 ) This experiment; ( I ) additional observations.
310
Gerardo Lardk
case the poultry manure was converted into a residue granular in texture and with less odour. As expected, a strong correlation between the weight and length o f the larvae was found (Fig. 1). The final mean values of both characteristics were lower than the mean values o f 250 mg and 25 m m reported for full-grown larvae o f H. illucens (Hale, 1973). The final total weight of larvae was 6.2 times that at the beginning which indicates a rapid growth in a short period of digestion, this being clearly an advantage from a practical standpoint. The gain in weight as related to the initial dry matter was low (Table 1). Denser populations of larvae would probably have produced higher yields in this type o f experiment. However, in practice yields would probably not be much higher as difficulties o f separating larvae have resulted in low yields when harvesting o f larvae from waste has been attempted (Eby & Dendy, 1978; Lard6, 1989). This should be taken into account if the ultimate use of the larvae as feedstuff is to be considered.
REFERENCES Booram, C. V. Jr, Newton, G. L., Hale, O. M. & Barker, R. W. (1977). Manure residue as a substrate for protein production via Hermetia illucens larvae. In Proc. 1977 Cornell Agricultural Waste Management Conference, ed. R. C. Loehr. Ann Arbor Science, Ann Arbor, pp. 599-604. Eby, H. J. & Dendy, W. L. (1978). An attempt to mechanize nutrient recovery from animal excreta. Transactions of the ASAE, 21, 395--8. Hale, O. M. (1973). Dried Hermetia illucens larvae (Diptera: Stratiomyidae) as a feed additive for poultry. Journal of the Georgia Entomological Society, 8, 16-20. Lard6, G. (1989). Investigation on some factors affecting larval growth in a coffeepulp bed. Biological Wastes, 30, 11-19. Miller, B. F., Teotia, J. S. & Thatcher, T. O. (1974). Digestion of poultry manure by Musca domestica. British Poultry Science, 15, 231-4. Newton, G. L., Booram, C. V., Barker, R. W. & Hale, O. M. (1977). Dried Hermetia illucens larvae meal as a supplement for swine. Journal of Animal Science, 44, 395-400.
Gerardo Lard6 Instituto Salvadore~o de Investigaciones del Caf~, Final Primera Avenida Norte, Nueva San Salvador, El Salvador (Received 10 September 1989; revised version received 5 March 1990; accepted 4 April 1990)
Short Communication Recycling of Coffee Pulp by Hermetia illucens (Diptera: Stratiomyidae) Larvae
ABSTRACT The digestion of coffee pulp by larvae of the soldier fly Hermetia illucens (L.) was studied in a small-scale experiment to obtain preliminary data pertaining to this method of treating the waste. After 13 days the coffee pulp was converted into a slurry-like material and lost 29.8% of the initial dry matter, the pH increasedfrom 7"6 to 8"85, the odour was reduced significantly, and the total weight of larvae was 6.2 times that at the beginning. It was concluded that H. illucens larvae could be utilized in recycling coffee pulp under controlled conditions.
INTRODUCTION Insect larvae growing on decaying materials can be thought of as agents for biological stabilization of noxious organic residues and as a potential source of protein usable in animal production. The first approach has been investigated for house fly larvae digesting fresh poultry manure (Miller et al., 1974) and beef cattle waste inoculated with Hermetia illucens (L.) larvae (Booram et al., 1977), whereas the latter approach has been studied by feeding swine and poultry on ground H. illucens larvae harvested from beef and swine feces (Hale, 1973; Booram et al., 1977; Newton et al., 1977). Larvae of H. illucens are also able to grow on coffee pulp, a very polluting waste generated in coffee-producing zones throughout the tropics. In a previous work (Lard+, 1989), larval populations of this species ranging from 165 to 625 individuals were found in sample volumes, 5.3 dm 3 each, taken 307 Biological Wastes 0269-7483/90/$03-50 © 1990 Elsevier Science Publishers Ltd, England. Printed in Great Britain
308
Gerardo Lard~
from a coffee-pulp bed, which is an indication of the potential that the larvae have as organisms for recycling coffee pulp; however, collecting the larvae from the decaying material was found to be a troublesome task under the management conditions employed. The experiment presented here was carried out to obtain preliminary data mainly pertaining to the digestion of coffee pulp by H. illucens larvae but also to their growth on this waste, since they can be utilized as a supplemental feed for animals.
METHODS Fresh coffee pulp (CP) was stored in airtight plastic bags for six months. Under this anaerobic condition CP underwent an alteration very similar to that occurring during the ensilage of much larger amounts. This procedure was followed bearing in mind that fresh CP is produced seasonally (3-4 months a year) and, hence, the use of CP preserved by ensiling would probably be necessary to keep a continuous recycling with larvae. To obtain an inoculum of larvae, the plastic bags were slightly opened so as to fully expose to the air only a small portion of the CP. After an exposure of 27 days, seven young larvae ofH. illucens collected from the bags were put in a glass Petri dish (10cm diameter, 2"5cm high) filled with CP from the inner zone of the bags where aerobic decomposition was slowest. The study consisted of just one experiment conducted at room temperature, 24"9 ___ 1.2°C. For a period of 13 days changes in the substrate were observed, and the larvae were individually weighed and their length measured at the same time so as to correlate these two body characteristics. Moisture was determined by drying at 105°C to constant weight and pH potentiometrically.
RESULTS A N D DISCUSSION Table 1 summarizes the results from the experiment. The progressive decaying of CP showed up in the increase o f p H as well as in the total solids reduction. The loss of dry matter was not much above that (20.3 and 21-7%) reported by Booram et al. (1977) for a period of 14 days. The texture of the substrate changed noticeably from the normal appearance of CP to a slurry-like material, and the odour was reduced significantly, indicating that H. illucens larvae could be utilized effectively in the treatment of anaerobically stored CP under controlled conditions. Miller et al. (1974) found comparable alterations of the substrate since in this
Recycling of coffee pulp by Hermetia iUucens larvae
309
TABLE 1
Changes in Substrate and Growth of Hermetia illucens Larvae Decomposing Coffee Pulp °
on
Time elapsed
Substrate weight (g) Moisture (g kg-1) pH Dry matter lost (%)b Larva length (ram)c Larva weight (rag)c Total larval weight (g) Overall growth rate (mg day-~)d Gain in weightfrs lost (gg-1) Gain in weight/initial TS (mg g - 1)
0 days
13 days
79.6 877.0 7.6 0 8.7 _+ 1.2 (7) 23"5 _+ 6' 1 (7) 0.165 __ _ 0
64.8 894.0 8.85 29"8 17.6 _+ 1.1 (7) 147.0 -t- 21-7 (7) 1.029 66"5 0.296 88.3
° Wet matter unless noted otherwise. b (Initial TS - Final TS)/initial TS. c Mean +_standard deviation (number of observations). a Gain in weight/time elapsed. TS, total solids.
180 E t60
~140 ~120
100 8( eo
6(
•
4( 2( 5
10
I
15
I
20
LENGTH (mm) Fig. 1. Relationship between length and weight (wet basis) of ttermetia illucens larvae grown on decomposing coffee pulp. Regression function: y = 0.051 038 x 2"783°29 (r = 0"991). ( 0 ) This experiment; ( I ) additional observations.
310
Gerardo Lardk
case the poultry manure was converted into a residue granular in texture and with less odour. As expected, a strong correlation between the weight and length o f the larvae was found (Fig. 1). The final mean values of both characteristics were lower than the mean values o f 250 mg and 25 m m reported for full-grown larvae o f H. illucens (Hale, 1973). The final total weight of larvae was 6.2 times that at the beginning which indicates a rapid growth in a short period of digestion, this being clearly an advantage from a practical standpoint. The gain in weight as related to the initial dry matter was low (Table 1). Denser populations of larvae would probably have produced higher yields in this type o f experiment. However, in practice yields would probably not be much higher as difficulties o f separating larvae have resulted in low yields when harvesting o f larvae from waste has been attempted (Eby & Dendy, 1978; Lard6, 1989). This should be taken into account if the ultimate use of the larvae as feedstuff is to be considered.
REFERENCES Booram, C. V. Jr, Newton, G. L., Hale, O. M. & Barker, R. W. (1977). Manure residue as a substrate for protein production via Hermetia illucens larvae. In Proc. 1977 Cornell Agricultural Waste Management Conference, ed. R. C. Loehr. Ann Arbor Science, Ann Arbor, pp. 599-604. Eby, H. J. & Dendy, W. L. (1978). An attempt to mechanize nutrient recovery from animal excreta. Transactions of the ASAE, 21, 395--8. Hale, O. M. (1973). Dried Hermetia illucens larvae (Diptera: Stratiomyidae) as a feed additive for poultry. Journal of the Georgia Entomological Society, 8, 16-20. Lard6, G. (1989). Investigation on some factors affecting larval growth in a coffeepulp bed. Biological Wastes, 30, 11-19. Miller, B. F., Teotia, J. S. & Thatcher, T. O. (1974). Digestion of poultry manure by Musca domestica. British Poultry Science, 15, 231-4. Newton, G. L., Booram, C. V., Barker, R. W. & Hale, O. M. (1977). Dried Hermetia illucens larvae meal as a supplement for swine. Journal of Animal Science, 44, 395-400.
Gerardo Lard6 Instituto Salvadore~o de Investigaciones del Caf~, Final Primera Avenida Norte, Nueva San Salvador, El Salvador (Received 10 September 1989; revised version received 5 March 1990; accepted 4 April 1990)