Turning Food Waste into Sustainable Insect Frass Fertiliser with Inspro
- Growing Kent & Medway
- Jan 9
- 4 min read
Updated: 5 days ago
Inspro, supported by Growing Kent & Medway, successfully demonstrated a circular solution for organic waste using Black Soldier Fly larvae. By converting waste streams into nutrient-rich "frass", the project validated a sustainable alternative to synthetic fertilisers that boosts soil health and microbial diversity.
At A Glance: Project Quick Facts
Project Lead: Inspro (Richard Small)
Collaborators: Wanstall Holdings (Doug Wanstall), University of Kent (Dr Anastasios Tsaousis)
Total Funding: £45,633 (Grant Awarded: £22,816 / Co-investment: £22,816)
Key Finding: Insect frass acts as a powerful biostimulant, significantly increasing specific beneficial bacterial species in the soil.
Food System Areas:
The Challenge: Closing the Loop in a Linear Economy
Organic food waste streams from local breweries, bakeries, and vegetable processors represent a massive, underutilised resource. Currently, much of this material is discarded, while farmers simultaneously rely on expensive, imported synthetic fertilisers to maintain crop yields. This disconnect creates a linear system that is both economically inefficient and environmentally costly.
Richard Small, founder of Inspro, recognised the difficulty of changing these established practices. As he noted regarding the systemic barriers, "We are seeking to operate a circular business plan in a linear economy which is like pushing water uphill". To break this cycle, he needed to prove that a local, circular alternative could not only manage waste but also outperform traditional chemical inputs.
The Innovative Idea: Insect-Powered Bioconversion
The solution lay in the insatiable appetite of the Black Soldier Fly larva. Inspro developed a system to bio-convert organic waste – such as brewer's spent grain – into two valuable products: protein-rich larvae for animal feed and a nutrient-dense manure known as "frass".
While the larvae are a known protein source, this project focused specifically on the frass – the "poo from the black soldier fly". The idea was to validate frass as a novel, slow-release fertiliser and plant stimulant that could match the macronutrient profile of farmyard manure while adding unique biological benefits, such as chitin-based insect deterrents – a natural material found in insect exoskeletons.
The Approach: 'Live and Local' Trials
Supported by one of our medium-sized grant programmes, Inspro launched a dual-track investigation. On the commercial side, they partnered with regenerative farmer Doug Wanstall to conduct field trials, alongside distributing "Live and Local" breeding kits to local smallholders. This allowed them to test the frass across diverse environments, from market gardens to polytunnels.
Simultaneously, the University of Kent provided rigorous scientific validation. Using high-throughput sequencing, researchers analysed the microbiome of the larvae and the resulting soil. They tested various application rates and substrate mixes to determine how dietary manipulation of the flies could enhance the quality of the fertiliser produced.
The Results: Unlocking Soil Potential
The research delivered a significant breakthrough in understanding soil health. The University of Kent found that applying the frass led to measurable improvements in nutrient availability and soil structure. Crucially, they observed an increase in specific bacterial species that act as biostimulants, enhancing root growth and resilience against diseases.
Commercially, the trials highlighted both the potential and the hurdles. While the product proved effective, the project identified that legislation requiring frass to be heated to 70°C for 60 minutes remains a cost barrier for small-scale producers. Despite this, the project successfully demonstrated that food waste-derived frass is not just a fertiliser, but a tool for increasing microbial diversity in the soil.
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Looking Forward: Scaling Up with ADOPT Funding
The success of these initial trials has laid the foundation for a significant scale-up. Inspro has recently been awarded an ADOPT grant to lead a major 12-month demonstration project: "Low Carbon Poultry Feed".
Working in a consortium with Wanstall Holdings (Kent), Loddington Farm (Kent), and Planton Farm (Shropshire), the project will deploy modular Bioconversion Units (mBCU) directly onto farms. This trial aims to prove the business case for farmers producing their own insect protein on-site, drastically reducing the UK poultry sector's reliance on imported soya and creating a true circular economy.
Our Support: Enabling Essential R&D
This project was supported by one of our medium-sized grant programmes, which provided the necessary capital for the "Live and Local" kits and the academic partnership with the University of Kent. This funding de-risked the experimental phase of the business, allowing Inspro to generate the data needed to challenge market norms.
Richard Small highlighted the value of this specific intervention: "The Growing Kent and Medway grant is just one of several grants we've had, but a very useful one... With the benefit of that grant, which we frankly wouldn't have done without... we are working with a dozen smallholders in the Kent area".
