Full steam ahead with clean energy from forestry waste

Mackwell & Co Ltd was established in 2016 by founder Sam Mackwell, with a focus on energy resilience and fossil-fuel-free transport. Mackwell realised the two concept needed to address this are the use of accessible and low value biomass as fuel, and a technology that can safely and cleanly convert this, often waste product, into useful work without relying on an extensive infrastructure.

The Mackwell A35 features a unique biomass-fired water tube boiler that is compact and responsive enough for use in transport as well as statically for fixed shaft power or electricity generation. The A35 traction engine is designed for horticultural and small farm towig up to seven tonnes at 40 km/h, with the developers suggesting that it could be a direct replacement for the myriad of MF 35 and 135's operating around New Zealand and elsewhere.

The same boiler and engine will also be produced as a 26kW generator set offering up to 180kW of heat. Once the concept is proven in the market, the design will be scaled to 600kW for industrial and marine use.

Customers can expect more than 35% in overall cost savings when replacing diesel engines, alongside a 96% reduction in CO2 emissions. Small engines are said to be suitable for manual fuelling, while the larger applications will require a mechanical feed system to maintain the 2.5 kg/kWh input requirement.

Mackwell engines can also deliver additional value where heat is needed, such as in hydronic underfloor heating or food processing situations. In this way, Mackwell engines go beyond traction to complement a range of renewable energy systems, but without the need for expensive storage or distribution.

Looking at practical considerations, biomass fuelling can make abundant use of the supply of waste timber sitting in forests around the country. Dry fuel consumption is 2.5 kg/kWh which will increase with moisture, but a key advantage is the ability to utilise any unprocessed biomass of up to 55% moisture content. Able to start from cold to working pressure in 10 to 15 minutes, the combustion chamber burns the range of 900 - 1000 degrees centigrade, with no smoke or sparks from the stack and the resultant ash able to be used as a fertiliser.

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Earlier this year, Mackwell partnered with Biocare Pty Ltd to design and manufacture four large combustion chambers for a project in Kangaroo Island, off the coast of Adelaide, which is set to become one of the largest biochar projects globally.