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Citation of this paper

Effect of fertilization with biodigester effluent on substrates of fruit waste or fermented fish waste, each mixed with pig manure, for growth of larvae from house flies

Phounvisouk Latsamy and T R Preston*

Living Aquatic Resources Research Center (LARReC),
NAFRI, Vientiane, Laos
TOSOLY, UTA-Colombia, AA#48, Socorro, Santander, Colombia


An experiment was carried out to investigate the use of fermented fish or jackfruit, together with pig manure, as substrates for production of larvae, and to determine if there were advantages in adding biodigester effluent to the substrates. The experiment was a 2*4 arrangement, the factors being: Substrate (fermented fish waste + pig manure or Jackfruit waste + pig manure) and Biodigester effluent (application of 100, 150, 200 or 250 mg N/m2 of substrate surface). There were 2 replicates of each treatment in a completely randomized design. The substrates were put in brick-lined enclosures with floor area of 0.25 m². The substrates were rapidly colonized by house flies (Mosca spp) and the larvae appeared within 20 to 24 hours after introducing the substrates. Six days after introducing the substrates, the larvae were harvested by immersing the substrates in water, and collecting the larvae which remained floating on the water surface.

The production of larvae was higher on the substrate with fish waste than on the fruit waste. There was no effect of the level of effluent and no interaction between substrate and effluent. Conversion rates were better for the substrates with fermented fish: 9 kg waste DM to 1 kg larval DM and 3.5 kg crude protein in the waste to 1 kg of protein in the larvae.

It is concluded that pig manure mixed with fermented fish waste is a better substrate for growing larvae than Jackfruit waste and pig manure. There appeared to be no advantages from applying biodigester effluent to the substrates.

Key words: black soldier fly, Hermetia illucens, Musca spp, recycling


The cultivation of fly larvae using local resources such as livestock manure would seem to be a valuable intervention for generating a source of high quality protein that can be used as animal feed. The common housefly (Musca spp.) and the Black Soldier fly (Hermetia illucens) possess some merits such as a short life cycle (Greene et al 1998). The adult females can lay eggs in many breeding materials. The larvae that hatch from the eggs scavenge for the protein in waste materials and accumulate it in their biomass. Thus, for sustainable development and environment protection, fly larvae can be a valuable biological component to support use of farm residue management and recycling in integrated farming systems (Sheppard No date).

Based on the above discussion, it is important to draw attention to the need to begin culture of fly larvae using agricultural and industrial wastes as the substrate. If such wastes are not used nor managed effectively, they will be harmful to human health and the environment because wastes are birth place of diseases, which are harmful to both humans and animals (Marc et al  2004).

Because fly larval biomass is rich in both protein and fat (Sheppard No date), the larvae would seem to be especially appropriate for feeding to frogs, which are carnivorous animals requiring high levels of protein and energy in their diet. The objective of the following experiment was to investigate the use of different waste materials, from fermented fish and jackfruit, together with pig manure as substrates for production of larvae, and to determine if there were advantages in adding biodigester effluent to the substrates.

The hypotheses were that larval production will be higher:

Materials and Methods


The experiment was carried out from 15th May to 15th October the Living Aquatic Resource Research Center in Naong Taeng District, Vientiane Province, Laos

Experimental treatments and design

The experiment was a 2*4 arrangement of the following factors according to a Completely Randomized Design. The treatments were:

Biodigester effluent

There were 2 replicates of each treatment in a completely randomized design.

Cultivation of the larvae

The larvae were cultivated in enclosures made from bricks. Each enclosure had surface area of 0.25 m² (50*50 cm) and a depth of 20 cm (Photo 1). The floor of the enclosure was made of concrete with a 15% slope at the entrance to facilitate the escape of the larvae. The enclosures were roofed with panels made of dried grass.

Photo 1.  The enclosures for cultivating larvae (made from bricks)


These were composed of mixtures of fresh pig manure and the waste from either fermented fish or jackfruit (Artocarpus heterophyllus). The proportions (fresh basis) were: 70% manure and 30% fish or fruit waste.

Pig manure

Manure was collected from the floor of the pens of pigs fed a diet of maize (30%), brewer's grains (30%) and concentrate supplement (20%).

Fermented fish waste

The waste was the residue from fish which had been processed for production of fish sauce. In this process the fish, after removal of the digestive tract, are fermented with rice bran, salt, garlic, yellow grass and water during a period of from 6 months to 1 year. At the end of this time, the fermented product is boiled and the liquid separated for sale for human consumption. The residue after separation of the liquid is normally thrown into the Mekong River as feed for fish. For the experiment the waste was collected from the market at weekly intervals.

Jackfruit waste

This was the flesh and fibrous residue from Jackfruit, not used for human consumption, which normally is used as feed for cattle and buffaloes. It was collected daily from the local market.

Biodigester effluent

The effluent was collected from a tubular polyethylene biodigester (photo 2) charged with the same pig manure used as substrate for the larvae. The biodigester was 6m long with diameter of 1m giving a total volume of 4.7m3. It was filled initially with 270 kg of pig manure and 300 litres of water. Subsequently, at weekly intervals, 36 kg pig manure and 130 litres water were added.


Photo 2.
 Biodigester and effluent

Production of larvae

The first step was to put 7 kg of fresh pig manure in each of the enclosures. Three kg of fermented fish waste or 3 kg of jackfruit waste (3 kg) were then placed on top of the pig manure. The appropriate quantities of biodigester effluent were sprayed on the surface of the substrates on days 1, 3 and 5. In a preliminary observation it was observed that larvae appeared within 24 hours of putting the substrate in the containers. The larvae were white in colour (Photo 3) and were very active.

Photo 3.
 Larvae of common house fly

On the basis of the colour and size of the larvae, and the short period (less than 24 hours) from introduction of the substrate to appearance of larvae, it was concluded that they were from the common house fly (Mosca spp) (Figure 1).

Figure 1.  Life cycle of the common house fly (Mosca spp)

On day 6 the larvae/pupae were harvested by putting the contents of each enclosure (substrate plus larvae) into a pond filled with water. The substrate sank to the bottom of the pond leaving the larvae floating on the surface. The larvae were then collected.


Samples of fresh larvae and of the fresh substrates were analysed for dry matter (DM), nitrogen and fat, according to AOAC (1990) procedures.

Statistical analysis

The data were analysed using the General Linear Model option in the ANOVA programmer of Minitab (2002) (version 3.2). Sources of variation in the model were: Source of substrate (fish waste or fruit waste), quantity of biodigester effluent, the interaction substrate*effluent and error.


The dry matter content and the content of nitrogen in the dry matter were higher for the fermented fish waste than for the fruit waste (Table 1). The values for the jackfruit waste were similar to those reported in Indonesia (19.8% DM and 1.33% N in DM) (Kusmartono, 2007). The N concentration of the biodigester effluent and the proportion in the form of ammonia were in the range (889 to1690 mg N/litre and 0.40 to 0.60 for proportion of N as ammonia) reported by (San Thy et al 2003) for tubular plastic biodigesters charged with pig manure in Cambodia.

Table 1.  Mean values for concentration of DM, ether extract and nitrogen in the substrates and of N in the biodigester effluent



Jackfruit waste

Fermented fish waste


DM,  %





Nitrogen, % in DM





Ether extract, % in DM





Total N, mg/litre





NH3-N/total N





ND: Not determined

 Composition of the larvae in the present experiment compared with reports in the literature are in Table 2.

Table 2. Composition of the larvae in the present experiment compared with reports in the literature



Crude protein,
 % in DM

Ether extract,
% in DM

Fermented fish








House fly larvae




House fly larvae#




# Shepherd (No date)

The production of larvae was higher on the substrate with fish waste than on the fruit waste (P=0.028). There was no effect of the level of effluent and no interaction between substrate and effluent. The results are therefore presented for the main effects (Tables 3 and 4). Conversion rates were better for the substrates with fermented fish, with conversion rates for DM of 9 kg waste DM to 1 kg larval DM and for protein of 3.5 kg crude protein in the waste to 1 kg of protein in the larvae.

Table 3.   Mean values for production parameters of larvae growing in pig manure mixed with either fish or fruit waste and biodigester effluent






Substrate, g fresh material



Pig manure





Fish waste





Fruit waste










Total DM





Total N*6.25





Larvae, g



Fresh matter















Conversion of substrate to larvae













# g DM in substrate/g of  larvae DM
## g N*6.25 in substrate/g N*6.25 in larvae

Table 4. Mean values for production parameters of larvae growing in pig manure and either fish or fruit waste according to application of biodigester effluent


 mg N/m2 of substrate surface










Substrate, g






Pig manure







Fish or fruit waste














Total DM














Larvae, g

Fresh matter





















Conversion of substrate to larvae















# g DM in substrate/g of  larvae DM
## g N*6.25 in substrate/g N*6.25 in larvae

The higher rate of production of larvae and the apparently better conversion rates for the substrates with fish compared with fruit waste were logical consequences of the higher content of protein in the former. As the analysis of the substrates and the larvae were done on bulked samples, it was not possible to make a statistical analysis of the conversion rates for DM and crude protein.


Papp (1974) (cited by Sheppard No Date) reported an 8% conversion (DM basis) of pig manure to house fly larvae (equivalent to a DM conversion of 12.5), which is similar to the overall mean of 10.5 observed in the present study (range of 8 to 14). There appear to be no reports on the protein scavenging capacity of the house fly larvae. However, the observed conversion rates (range of 2.8 to 4.8 kg protein in waste to larval protein) indicate that they are highly efficient in recovering the protein from waste materials.

Reports in the literature indicate similar conversion rates for manure into larvae. Sheppard et al. (1995) described an inexpensive manure management system to convert poultry manure to house fly larvae (containing 42% protein, 35% fat) with an 8% DM conversion rate. According to Newton et al (2005), pig manure is the principal food of many insects in nature, especially the larvae of the black soldier fly and house fly. Chiou and Chen (1982) (cited by Sheppard No Date) found that house flies converted 50 to 60% of swine fecal mass to larval mass (presumably on fresh basis), including recovery of up to 55% of the manure organic carbon as larval carbon. BSF larvae converted manure in a 460 hen facility to pre-pupal biomass at a 7.8% (DM basis) rate (Sheppard et al 1995), which would represent 58 tonnes of pre-pupal biomass from 100,000 hens in 5 months. House flies under optimum laboratory conditions converted poultry manure to pupae at a 7.6% rate (Miller et al 1974).

Conclusions and recommendations


The authors are grateful to the Swedish International Development Agency-Swedish Agency for research Cooperation with Developing countries (Sida-SAREC) for supporting this study. Thanks are also given to the staff at the pig station in Naong Thaeng Village, Mr. Young Thong, who supported and make it possible to conduct this study on fly larvae. Thanks are given to Mr. Thanh, for help in installing the biodigester. Appreciation is given to the Laboratory of the Livestock Research Center of the National Agriculture and Forestry Institute of Laos, for analysis of the samples.


AOAC 1990   In: Helrick (Editor ) Official methods of analysis. Association of Official Analytical Chemists, Arlington, Virginia, 15th edition, 1298 pp.

ANOVA 2002   Programmer of Minitab Statistical software Release version 3.2. Minitab Inc, USA.

Chiou Y Y and Chen W J 1982  Production of maggot protein produced from swine manure. K'o Hsueh Fa Chan Yueh K'an, 10: 667-682. (cited by Sheppard C, No Date).

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Papp L  1974  House fly larvae as protein source from pig manure. Folia Entomol. Hungarica. 28: 127-136.(cited by Sheppard, C   No Date)

Sheppard D C,  Newton G  L, Thompson S A and Savage S E 1994   A value added manure management system using the black soldier fly. Bioresource Technology 50 : 275-279

Sheppard D C  No date Black Soldier Fly and Others for Value-Added Manure Management.

San Thy, Preston T R and Ly J 2003  Effect of retention time on gas production and fertilizer value of biodigester effluent.  MSc Thesis, MEKARN-SLU

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