Inventor wants to slow climate change with modern steam engine

A Canterbury man has invented a better steam engine and thinks it can help mitigate climate change. Reports by Will Harvie.

Sam Mackwell wants to “eliminate diesel from food production”.

Some New Zealand farmers burn 200,000 to 300,000 liters of dirty fuel a year, he says, and every drop contributes to global warming.

Mackwell insists he has a better alternative – a steam engine. Burn wood chips.

His steam tractor »matches weight, speed and performance of the equivalent diesel tractor”. Most farmers have more than enough trees to power a steam tractor all day, every day. And they would save all that diesel cost. For him, it adds up.

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Mackwell claims to have improved the steam engine. His model burns fuel at around 900°C, compared to around 400°C in conventional steam engines. This means that all fuel is consumed. There is no smoke and no sparks. It’s zero carbon, he says.

How it achieves this is a company secret, but involves an “advanced combustion system” and heat exchange system that uses only 3% of the water of a conventional steam engine. The result is “high pressure superheated steam”. In a brochure, he speaks of “very pure steam”.

It powers a motor that spins the wheels. Everything has been independently peer reviewed and a patent applied for.

It has not been possible to convince the farmers that a 150 horsepower steam tractor is practical. Surely it is unnecessary that the first steam tractors cost about twice what the equivalent diesel tractors cost.

So he turned to trains. Or rather, he’s gone back to trains because he’s been to that market before. Indeed, he had almost struck a deal to build a steam engine for Dunedin Railways, best known for running heritage trains across the Taieri River Gorge.​

Alas, the pandemic collapsed the Dunedin historic train market and the sale was shelved.

Yet there are hundreds of heritage trains in circulation around the world and the cost of maintaining old – and very old – steam boilers can be enormous. Mackwell’s new and improved steam engine might be a better alternative. Especially considering that many heritage steam engines burn cursed coal.

“Climate change is my whole motivation,” Mackwell says in a corporate video.

He had this motivation at a young age. While still in high school in Christchurch, he was experimenting with hydrogen as a fuel – not an average teenage interest. But he set off “many explosions” in his parents’ living quarters west of Christchurch.

He switched to liquid and gaseous biofuels and, at age 18, designed a turbine engine and mounted it on a kart machine. There is video of him driving it down a side road in Canterbury, but little evidence that he met vehicle safety standards.

Mackwell quickly concluded that liquid and gaseous biofuels burn almost as much energy to produce as they contain, which is inefficient and wasteful for climate change.

So in 2015, at age 21, he switched to solid biofuels – trees. They are “nature’s solar panels and batteries,” he says on the video. He’s been on the project ever since.

Mackwell, now 28, has no formal qualifications. He enrolled in engineering at the University of Canterbury but dropped out six weeks later because it was eating away at his steam engine time.

He had already taught himself to weld on his parents’ lifestyle block. He had acquired a large lathe, later a milling machine and other manufacturing equipment – ​​and taught himself how to operate them.

And he was deeply learning how conventional steam engines work and how to improve them. There are maybe 50 people working on “modern steam” around the world – Argentina is a hotspot – and Mackwell tapped into their expertise and adopted some of their technology.

He also found private investors willing to fund this quest. One is Philip Royds, a co-founder of Christchurch Link Engine Managementwhich develops and manufactures motorsport electronics and performance technologies sold in 65 countries.

Royds is managing director of Mackwell’s two companies, Mackwell Locomotive​ and AgLoco.​

The duo have now identified a new niche that combines food production and trains – sugarcane farmers in Australia and Fiji. The sugarcane becomes tall and bulky. Many of Queensland’s 4,000 sugar cane growers already transport harvested cane on narrow gauge railways instead of trucks. Anyone who has driven through sugar cane country in Queensland will have seen these operations.

In the state, rail infrastructure and rail expertise already exist.

The biofuel would be the bulky straw left after harvesting and processing the cane. Indeed the tares, or “bagassewas burned in steam locomotives that historically served the cane industry in Queensland, before being replaced by diesel.

The industry also burns bagasse at its sugar processing plants to generate electricity and sells excess electricity to the grid.

Obviously Mackwell’s steam engine can burn different solid biofuels. He chose New Zealand wood because it is widely available and woodchips because they are easy to handle and store. But he could burn down a sawn-off picnic table (and probably did).

And in case anyone imagines a farmer madly shoveling woodchips into a firebox, Mackwell has an answer: Mechanize it. Many coal-fired locomotives are equipped with these systems which replace manual labor.

Mackwell has yet to sell any of his steam engines. It fights “perception barriers” that steam is “no longer relevant”. Its investors don’t seem to care. Mackwell’s businesses have hired – there are now seven employees.

And the carbon footprint of the atmosphere continues to climb. In mid-August, the atmospheric CO2 reading at Baring Head, Wellington was 415.4 parts per million, down from 400ppm in 2016.

“We need to move away from fossil fuels as quickly as possible and current technology… doesn’t allow us to do that,” Mackwell says.