Peat extracted for horticulture  has the potential to release approximately 880,000 tonnes of CO2 in a single year — the equivalent emissions of driving to the moon and back 4,600 times, according to The Wildlife Trusts. To reduce its environmental impact, a UK based manufacturer of composts and growing substrates, wanted to expand its peat-free product range. To achieve this, it turned to Technidrive, a specialist supplier of motors and drives, to engineer the system that would make it possible.
Peat has long been a component in horticultural products, especially in potting mixes and composts for its water retention and nutrient properties. However, peat extraction contributes to the destruction of valuable ecosystems, releasing carbon and contributing to greenhouse gas emissions.

In fact, the Department of Agriculture, Environment and Rural Affairs, responsible for these sectors in Northern Ireland, has highlighted the potential negative effects of peat cutting. This includes the direct loss of biodiversity and negative effects on the hydrological system leading to localised flooding and repercussions on a national level due to the depletion of a significant carbon store.

The challenge

To produce eco-friendly alternatives of its growing products and mix substrates, the manufacturer began investigating peat-free wood-based material possibilities. Wood chips can be added to a compost pile to provide a better carbon nitrogen ratio and, with their rigid structure, also enhance the flow of air through the compost since they are less prone to compact.

Wood chip is a common byproduct of tree trimming and landscaping, which meant that the manufacturer could improve its sustainable practices by leaning on waste wood byproducts from local sawmills in Ireland, as opposed to importing the product. 

As an alternative, it chose to invest in its own processing facility, by creating a brand-new wood fibre processing plant. The goal was to ensure its own supply of this material and significantly extend its peat-free range of products.

Technidrive was brought in to support with the creation of a complete system for the wood fibre processing plant. The set-up was required to transport wood chip to the feed bin, transfer it to a primary conveyor and pass it through the bottom extruder, before it emerged from the offload conveyors. This process can be compared to pressing modelling clay through a mould — the extruder shapes the wood chip into fine fibres resembling pulled pork, which are then blended into different compost products.

The primary challenge involved synchronising the system’s speed and feed rates with the  extruder’s operational capacity. Moisture levels, density and particle size of the raw wood could all vary, requiring precise torque and speed control throughout the process.                                            

A key specification was that the equipment needed to transition smoothly from a low-frequency operation at 5 Hertz (Hz) to a significantly higher 100 Hz.  This was made possible by WEG's advanced technology in Variable Speed Drives (VSDs) using Optimal Flux technology, which allows the system to deliver 100 per cent torque at frequencies as low as 5Hz, without requiring external forced cooling.

This shift was crucial to ensure better control over the speed of process. Achieving this demanded meticulous evaluation of the extruder’s adaptability to changing conditions.

Product selection

Technidrive took a strategic approach to product selection. As a WEG Premier Partner and a BEST Partner of Italian motor manufacturer, Bonfiglioli, Technidrive had an impressive portfolio of products to choose from. For this project, WEG IE3 motors were chosen and fitted to Bonfiglioli Gearboxes.

Technidrive carried out calculations for power and speed and opted for two 0.25kW geared motors with a combined gear reduction of 6881:1 using High Efficiency Pre-Stage Helical and final output Bevel Helical Gear units. As a result, this led to a very low speed of 0.2 RPM but with a very high torque. This ensured a low and constant flow of product onto the main conveyor.

Lastly, two more Bonfiglioli gearboxes were also installed onto two large bins, each of which holds six tons of wood chip for the overall process. The gearboxes act as material beaters, creating a uniform flow of product onto the main conveyor.

“The project is a fantastic example of our team’s engineering knowledge,” explained Johnathan Johnston, internal sales and project engineer at Technidrive. “The state-of-the-art facility has been engineered with the best possible products from our industrial partners, ensuring the plant can manufacture environmentally friendly products in a smart and efficient way.”

Achieving sustainability

With a strategic blend of WEG products and Bonfiglioli components, the result was a system that aligns with the manufacturers goal to prioritise eco-friendly practices. IE3 rated motors with premium efficiency, resulted in energy savings and reduced operating costs but also, importantly, reduced CO2 emissions due to low power consumption.

Investing in a brand-new wood fibre processing plant, installed in June 2023 with production fully underway that same month, was a key part of the manufacturers sustainability journey.

The investment in the new wood fibre plant is a step forward in the manufacturer’s sustainability initiative. By reducing its reliance on peat and making greater use of locally sourced wood byproducts, the company is lowering its carbon footprint while supporting the regional economy. The installation supports the production of a wider range of peat-reduced and entirely peat-free growing media.

The new wood fibre processing facility will enable the manufacturer to produce greener and more sustainable composts and growing materials for years into the future.

For more information on how Technidrive can provide industrial drive solutions for the horticulture and processing industries please visit www.technidrive.co.uk.