The Science Behind Frass: Why This Natural Fertiliser Works Wonders
In the world of natural gardening, few products strike the perfect balance between plant health, soil vitality, and sustainability. One standout? Mealworm frass – a light, low-odour, microbe-rich fertiliser that’s gaining traction with green thumbs across the globe. You might’ve come across the term insect frass, but what exactly is it – and why are so many gardeners turning to it as a go-to organic feed?
Let’s dig into the science behind this natural soil booster and explore how it can help your plants thrive.
What Is Insect Frass?
Insect frass is a fancy name for a very natural thing: insect manure. In the case of mealworms (Tenebrio molitor larvae), frass refers to their dried excrement mixed with fine fragments of shed exoskeletons and tiny traces of uneaten plant matter. It’s dry, crumbly, and looks a lot like a fine organic powder or sand.
What makes mealworm frass so special is what’s inside:
- Balanced nutrients (like nitrogen, phosphorus, and potassium – the trio plants love)
- Beneficial microbes from the mealworm gut
- Chitin, a natural compound from insect shells that’s been shown to boost plant immunity
Unlike animal manures, mealworm frass is virtually odourless, dry, and ready to use straight from the bag – no composting or waiting period required.
Source: Rich Roots Fertilisers | Hand Holding Sand-Like Raw Mealworm Frass
Why Insect Frass Outperforms Traditional Fertilisers
This is where things get really interesting. While compost and animal manure can be great for long-term soil conditioning, mealworm frass offers higher immediate nutrient availability – and without the mess or strong smell.
In fact, recent research suggests that insect frass outperforms traditional organics in key areas. One study found that insect frass could supply up to 159 kg of nitrogen per hectare, nearly double the nitrogen provided by poultry litter in some cases (Amorim et al., 2024). That means plants can access more nutrition, faster – without the risk of overfeeding or chemical runoff.
And because the nutrients are organically bound, they’re released gradually as soil microbes break them down. That means fewer applications, better nutrient retention, and healthier soil over time.
Better for the Planet, Too
Mealworm frass isn’t just good for your plants – it’s also part of a smarter, more sustainable way to garden. Because mealworms can be raised on food scraps and agricultural by-products, their frass forms part of a circular economy: turning waste into a high-value resource for growers.
Plus, it comes with built-in peace of mind. Compared to some animal-based fertilisers, high-quality frass is typically low in heavy metals like cadmium or chromium and carries minimal pathogen risk. That makes it a safer choice for long-term use – especially in edible gardens.
A Natural Fit for Eco-Conscious Gardeners
Whether you’re growing herbs on a windowsill or managing a full veggie patch, mealworm frass fits beautifully into chemical-free gardening. It’s a slow-release, plant-safe, and soil-building option that supports healthy growth without the harshness of synthetic alternatives.
Source: Amorim 2024.¹
And unlike liquid fish-based fertilisers or animal manures, you won’t need to hold your nose to use it. The scent is mild and earthy – somewhere between grain and soil – and disappears almost completely once watered in.
How to Use Mealworm Frass in the Garden
It’s easy to apply frass in a way that fits your routine:
- Top-dress garden beds or pots every 2-4 weeks by sprinkling frass around the base of plants and watering it in.
- Mix into soil at planting time – aim for roughly 150g per square metre in garden beds, or a small handful per pot.
- Brew a frass tea for liquid feeding by steeping it in water, straining, and applying as a root drench or foliar spray.
Your plants will respond with stronger roots, lusher growth, and improved resilience over time – thanks to both the nutrients and the living microbes frass brings to your soil. Learn more about how to apply frass and how much to use in our step-by-step guide.
In Summary
Mealworm frass is more than just an organic fertiliser – it’s a sustainable, low-effort way to feed your plants, support healthy soil biology, and keep your garden thriving naturally. It’s lightweight, odour-free, and safe for virtually all plant types, indoors and out.
Whether you’re a beginner or a seasoned grower, it’s an easy swap that delivers long-lasting results – without compromising your values or your plants’ wellbeing. Learn more about the Rich Roots story and what drives our approach.
Worm frass, healthy soil, and circular growing 👉 Find out how it all connects.
Not sure how to use frass? We've got your soil covered – top tips and more 👉 Read the guide
Ready to Give Frass a Go?
Choose the size that suits your patch:
- 🌱 10 g Sample Sachets – Perfect test-run for pots.
- 🌿 160 g Raw Frass Pouches – Everyday feed for balcony beds & veggie boxes.
- 🪴 480 g Packs – Great value for keen growers.
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References:
- Amorim, H. C. S. et al. (2024). Insect frass composition and potential use as an organic fertilizer in circular economies.