May 2015

An ex-shepherd has built a business that recycles abbatoir and food waste using tiger worms

Central Wormworx Ltd was established in 2000 with a view to providing a clean and green solution to what was a growing community waste issue. Research had shown that using tiger worms to convert waste could reduce those problems.

Robbie Dick was a shepherd at an abattoir and wondered about all the waste that was sent from there to be dumped. In 2000 in a partnership he bought half a ton of worms from a company in the North Island to start up a worm farming business. After 18 months, the partnership was dissolved and Robbie and his wife became sole owners.

The worms are known under various common names such as redworm, brandling worm, tiger worm, and red wiggler worm. They’re a species of earthworm particularly adapted to living in organic material. These worms thrive in rotting vegetation and manure. They have groups of bristles (called setae) on each segment that move in and out to grip nearby surfaces, as the worms stretch and contract their muscles to push themselves forward or backward.

Tiger worms are the most common earthworm in compost bins (Eisenia foetida) and can eat their own body weight in food each day. The worms mate and lay egg capsules. These can lie dormant, only hatching when the temperature of the beds is favourable.

These days Wormworx operates on a hectare of land leased from the council in industrial land near downtown Cromwell. They have fourteen windrows, each sixty metres long containing tiger worms, which convert thirty-five tonnes of household, supermarket fruit and vege waste, and orchard and wintering shed waste. The end product produced is worm castings, which is sold in bags or bulk supply. Each one of the 60m rows takes 2 tons of waste every 10 days.

Tiger worms thrive in warm moist conditions to they’ve installed a soak hose along the top of each row. Luckily, given the winter climate in Cromwell, the worms will also tolerate cold conditions.

The cycle of waste to worms to worm castings is a simple one. Worms multiply two-fold every thirty days and consequently the company has not bought any additional tiger worms, even though the quantity of waste has increased substantially over the years.

Part of the success of the business has to do with the low capital intensity of the operation.

Robbie says around 80kg of worms are sold each week. A kilo of warms equates to about 4000 worms. Robbie and his staff harvest them from the rows and then weigh and pack them in a layer of moist peat. 1kg costs around $45, although prices vary according to the size of the order. Customers include plumbers who need worms for composting toilets to home gardeners, right through to commercial operators using worms for composting.

Rural Delivery has already filmed two businesses that successfully use tiger worms to process waste. One is the Biofiltro business that uses the tiger worms on a dairy farm in Southland – the other is a meat processor near Ashburton who uses the worms to deal with stomach paunch from the processing. The latter business has turned a high dumping cost problem into a revenue generator.

Robbie acknowledges there is a need for further scientific research to be done in analysing the end product but he reckons the worm castings are a great product. “Worms, in my view, are a viable waste management option.” He says many hundreds of households now have a worm bin to recycle their kitchen and garden waste.

Robbie says one area of interest is the conversion of the animal waste from the local transport’s truck wash in Cromwell. Their pit is emptied three times per year, and the semi-solid waste material is delivered to the worm farm. Once the product has stabilised through natural evaporation, it can be fed out to the worms. This waste material is completely converted and reused as a farm or garden soil conditioner.

Robbie also sees a commercial opportunity in managing dairy farm effluent, converting this product with worms, and then returning it to the land in a solid state, at a controlled rate.

Dairy wintering shed waste has been trucked to the worm farm, fed to the worms, and samples sent for analysis. The analysis shows neutral pH, excellent water retention capabilities and the NPK is very good. Most importantly, the fungal and bacterial properties are in balance.

At Central Wormworx Robbie says they are handling approx 1500 tons of waste annually. This amount has increased over the years as the need for worm food escalates which is relative to the demand for worm castings.

During the fruit harvest season Robbie’s worms also deal with fruit waste, in particular cherries from local orchards.

The worm castings are primarily used in the Central Otago Region, but latterly have been distributed throughout the South Island with orchards, vineyards and private gardeners using this high quality soil conditioner to improve the quality, yield and vibrancy of their plants.

Robbie has also trialed the worm castings to grow grass and believes returning worm cast to farms will improve soil structure and increase the population of worms in the soil. He says this would be an ideal way to recycle shed waste and the spin-off for farmers would be a large reduction in fertilizer costs.

There’s an increasing demand for worm castings from commercial and home gardeners. The vermicast can be used as a soil conditioner in gardens, pot plants and crops. Studies of the castings show they contain five times more nitrogen, seven times more potassium and 1.5 times more calcium than standard soil. It is also pH neutral.