Research to investigate plant protection and fertiliser qualities of residue left after insect bioconversion using Black Soldier Fly (BSF) is underway in Newcastle and York.
Charles Brakspear, PhD candidate, based at Newcastle University and Fera Science Ltd in York, is examining the chemical, biological and physical properties of the residue remaining after insect bioconversion.
“There is significant potential for the residue of substrate left after rearing insect larvae to be used as fertilisers and growth media for a range of plants being produced in horticultural and agricultural environments,” confirms Charles.
“This residue is known as frass and has a fertilising value comparable to other farmyard manures. My research indicates that applying insect frass to the soil can lead to positive changes in soil quality indicators and enhanced soil ecosystem functions. Frass not only has fertilising value but contains chitin that is beneficial to soil microbes that induce systemic plant resistance. Invitro assays have also shown that frass contains microbes that inhibit the growth of a range of plant pathogens.”
Charles’ project is building on extensive work over the past few decades that has already established the concept of using insects to reduce volume of waste streams and derive high-value products from insect larvae. A growing number of companies have been established globally to utilise the protein in insect larvae for inclusion in animal feed, for example, and whilst more research papers are now being published, much research remains to be done.
“The insect species that has been the main focus of this research is the black soldier fly (BSF), Hermetia illucens,” adds Charles, “as they have extraordinary dietary plasticity and can be reared on a wide range of substrates from food waste to animal manures. BSF is excellent at converting waste streams into valuable protein and fertiliser.”
Collecting eggs from adult flies to trial them on a range of substrates produces frass with different physiochemical properties and evaluating their use as a fertiliser.
The chemical, physical and biological features of the rearing substrate residues from a range of organic materials are being examined at Fera, with glasshouse and field trials to determine the effect on tomato and potato plant growth, development of disease and soil quality. The results are being assessed to identify which agri-food sectors will benefit from insect bioconversion and the residues produced.
The impact of BSF bioconversion residue on soil microbiome diversity in bacteria and fungi on tomato plants has already started to be assessed using DNA metabarcoding and real-time PCR.[i]
“Fungal pathogens, such as Fusarium oxysporum and Verticillium dahliae are globally destructive diseases of the tomato plant, causing significant economic losses to farmers,” explains Charles. “Current chemical treatments against these fungal pathogens are often expensive, ineffective, and detrimental to long-term soil health”.
The initial results of Charles’ project suggest that applying insect frass to soil can stimulate plant growth by stimulating indigenous plant growth promoting rhizobacteria; which in turn provide nutrients to the plant and compete with fungal pathogens, thereby decreasing the fungal disease in the soil and disease severity in the plant.
“Our first findings suggest that insect frass provides an environmentally sound addition to the tools farmers can utilize in integrated pest management,” comments Charles, “making it ideal for use on organic farms and in glasshouse settings where pesticides are strictly controlled.”
Charles presented these initial and promising results at the 2022 Insects to Feed the World Conference (Quebec, Canada), where academics, commercial operators, farmers and policymakers gathered to discuss the continuing emergence of the potential of insects to reform the global food system.
“Thank you to my expert colleagues and supervisors at Fera’s innovative Insect Research Unit, for contributing their insights, practical help and facilities enabling me to progress my research,” adds Charles.
The project is funded by IAFRI (Institute for Agri-Food Research and Innovation) a joint venture between Newcastle University and Fera Science Ltd (Fera). Follow the progress of Charles’ work on Twitter using his handle @charleszimbabwe.
For more information on Fera’s insect bioconversion services, including its dedicated three packages of exploration with companies – Reduce, Repurpose and Redistribute, please visit https://www.fera.co.uk/insect-bioconversion-services
[i] Real-time polymerase chain reaction (real-time PCR) is commonly used to measure gene expression.