Reducing emissions from byproducts: [2] Black soldier flies - the 'biological machine'

Cutting CO2 by nearly 90% compared with composting

The black soldier fly (scientific name Hermetia illucens) requires large amounts of nutrition during its larval stage to grow. The larvae can feed on many types of decomposing organic matter, converting it into nutrient-rich biomass. Black soldier fly larvae are now used as livestock feed, providing an important protein source for pigs, poultry, and aquaculture.

This capacity to convert organic matter also offers a way to process agricultural byproducts while reducing greenhouse gas emissions. Rather than becoming waste that must be treated, byproducts are returned to the production cycle to create valuable biomass, reducing the volume of residual organic matter and creating a raw material that can partially replace conventional livestock feed ingredients.

This is also the approach taken by the project "Research and Application of Technology in Black Soldier Fly Farming to Treat Agricultural Waste and Produce Livestock and Aquaculture Feed in Ba Ria-Vung Tau Province (pre-merger)," led by Prof. Dr. Duong Nguyen Khang and carried out by the Center for Research and Technology Transfer at Nong Lam University Ho Chi Minh City.

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Reducing emissions from byproducts: [1] An overlooked resource

From an environmental standpoint, the black soldier fly model helps return organic waste to the production cycle rather than simply treating and disposing of it. Byproducts serve as feed for the larvae. The resulting larval biomass then becomes a protein source for livestock and aquaculture.

As a result, a portion of the waste is converted into a valuable raw material while reducing demand for conventional protein sources. The remaining substrate after the rearing process can also continue to be used as fertilizer or fed into other organic treatment processes.

Research from Nong Lam University Ho Chi Minh City found that black soldier fly larval biomass reaches approximately 5.20–5.38 kg of fresh larvae, equivalent to 1.55–1.60 kg after drying. The average gross profit margin reached 57.92%. Notably, compared with composting, the black soldier fly model reduced CO₂-equivalent emissions by approximately 89.91%.

"This shows that reducing waste and reducing emissions can happen simultaneously with creating economic value," Prof. Dr. Duong Nguyen Khang affirmed.

To support this point, Prof. Dr. Khang cited a study published in Waste Management, which found that treating food waste with black soldier fly larvae achieved an average substrate reduction of about 49%, while direct greenhouse gas emissions from the process were relatively low. The study calculated combined CH₄ and N₂O emissions at approximately 0.38 kg CO₂-eq per ton of food waste treated.

Another study published in the Journal of Cleaner Production likewise found substantial reductions in material volume when black soldier fly larvae were used to treat fruit and vegetable byproducts. For vegetable byproducts such as broccoli and cauliflower, material reduction reached as high as 84% under certain experimental conditions.

More notably, a life-cycle assessment conducted in Indonesia found that direct greenhouse gas emissions from a black soldier fly waste treatment system were significantly lower than those from composting. The study calculated direct CO₂-equivalent emissions to be 47 times lower, with the composting system's total global warming impact roughly double that of the black soldier fly system under the study's conditions.

"The effectiveness of this method depends on the type of feedstock, moisture content, nutritional composition, rearing conditions, scale, and how the residual substrate is handled afterward. But these findings make one thing fairly clear: using black soldier fly larvae to convert organic waste into valuable biomass is a low-emission approach to byproduct treatment," Prof. Dr. Khang explained.

Substantial environmental value

From an environmental perspective, black soldier flies offer several notable benefits. First, the larvae consume organic byproducts as feed, thereby reducing the volume of waste that must be treated. This model also has the potential to reduce greenhouse gas emissions compared with certain conventional treatment methods. When organic matter is treated improperly, decomposition can generate methane (CH₄) and nitrous oxide (N₂O).

Notably, the nutrients in byproducts are not simply discarded but are converted into protein-rich larval biomass. The remaining residue can be processed into organic fertilizer or soil amendments, returning the material to production.

Findings from a scientific project recently approved by the Ho Chi Minh City Department of Science and Technology show that black soldier fly larvae can utilize byproducts for 60-70% of their feed ration. The model reduces CO₂-equivalent emissions by 89.91% compared with composting.

The 89.91% reduction in CO₂-equivalent emissions achieved by the Ho Chi Minh City model demonstrates this technology's potential contribution to low-carbon agriculture goals. It also aligns with the city's efforts to build circular, low-carbon agricultural models that reduce greenhouse gas emissions.

Beyond the research stage, the black soldier fly model in Ho Chi Minh City has moved into industrial-scale production and has begun connecting with byproduct streams generated directly by factories.

In the Ba Ria-Vung Tau area, Entobel (a Belgian company) is partnering with Heineken Vietnam to purchase brewer's spent grain as feedstock for raising black soldier fly larvae. Spent grain, along with byproducts from cassava, rice, and other food processing industries, are among the raw materials the company currently uses.

For Heineken Vietnam, partnering with Entobel to repurpose spent grain as black soldier fly feed represents an effective environmental solution. The partnership offers the company two benefits: easing waste treatment pressure while turning a byproduct into a source of revenue.

According to Pham Kim Dang, Deputy Director of the Department of Animal Production and Health, black soldier flies are among the solutions expected to transform the livestock industry, opening up numerous opportunities for developing green livestock farming. Beyond that, raising black soldier flies also effectively addresses the problem of byproducts in livestock and crop production and delivers strong results in aquaculture.