When Peter Brown started investigating establishing miscanthus in New Zealand in 2009, decarbonisation was barely in the lexicon, biofuels had been given the boot by the National government and dairying was seen as the growth answer for the primary sector.
But a lifetime spent in the energy sector had left Brown convinced the planet was on borrowed time for hydrocarbon sources and the impact it was having on climate systems, so he set out to find an alternative fuel source that could be grown here as a viable crop by farmers.
His answer is miscanthus grass. Grown across a range of climates from Sweden to Greece in the Northern Hemisphere, it is used as a bulk biofuel source for boilers to replace burning coal and is also capable of being turned into renewable diesel and generating gas for electricity production.
At considerable personal expense, Brown imported tissue culture of the plant that he has managed to multiply across several field plantings today, growing as a sterile triploid hybrid.
Lincoln University trials with centre pivot irrigation have the plant consistently yielding 30-plus tonne a hectare, but Brown conservatively quotes 20t/ha, similar to a maize crop.
While less known in NZ, miscanthus has become a biofuel staple in the United Kingdom since the early 1990s.
Recently, interest has lifted further as the UK’s Committee on Climate Change called for a lift in perennial energy crop plantings to accelerate to 30,000ha a year by 2035, ensuring 700,000ha would be planted by 2050.
From a farming perspective, miscanthus could offer some physical and financial benefits as a perennial crop that can be planted once and left growing and harvested for multiple seasons.
“The biggest cost is up front, getting it established and keeping the weeds out for the first year until the plants grow high enough to shade them out,” Brown said.
The crop is suited to a wide climatic regime, requiring only 600mm-plus of rainfall a year.
Harvest can commence economically at year two, and crops have been known to last for over 20 years.
Lincoln University and Fonterra trials indicate miscanthus absorbs high levels of nitrogen into its rhizome system, and the Fonterra research indicates that N losses under miscanthus crops were less than a tenth of low-loss pine plantations.
As the crop senesces the moisture level drops below 20%, and harvesting is over winter using conventional harvesting headers. This makes it a “dry” source of fuel compared to forestry biofuels that can be as high as 50%-plus in moisture.
As an energy source it also ranks well.
Research by ex-Plant & Food scientist Dr Rocky Renquist cites an “energy use ratio” – gross output of energy divided by energy required to produce it – of 129:1.
Miscanthus NZ has a stand of miscanthus growing next to the Oji Fibre mill at Kinleith, which supplied a mill boiler with a miscanthus-sawdust fuel mix.
Brown says interest in the crop from farmers has grown strongly in the past two years, partly driven by demand for it as a bedding in bloodstock and indoor dairy/calf rearing operations.
He counts Spring Sheep Dairy as a major client, using it in their dairy sheep operation.
“We could easily have sold two to three times more than we have had in the past 12 months, and we have already sold this year’s winter harvest. We are desperate for an increased area to grow on,” he said.
Brown says cropping miscanthus could include a five-year supply contract, working on $200-$250/t payment.
His company has about 25ha of its own land already growing the crop, with an additional 40-50ha growing elsewhere around NZ. Brown says plantings of 10ha-plus would be welcome additions to their inventory.
He is also encouraged by what the Climate Change Commission’s views on renewable low-carbon fuels may mean for miscanthus as a future crop. The commission is recommending 140 million litres of low-carbon liquid fuels be sold by the end of 2035.
The crop is an ideal feedstock for renewable diesel, with low moisture content and low natural sulphur levels compared to other crops.
“And along with the benefits of not importing hydrocarbons while reducing carbon dioxide emissions, is the benefit of high-quality biochar, which can be used for soil improvement, effectively permanently sequestering carbon, with possible carbon benefits under ETS (Emissions Trading Scheme),” he said.
Brown says it may take underwriting by a large energy-using processor to give miscanthus the critical mass it needs for farmers to get on board with it as a long-term crop.
Bio Energy Association executive officer Brian Cox says of the possible biofuel crops, miscanthus offers some multiple income streams and could integrate well into many farm systems.
“In Canterbury, for example, where irrigators mean you can’t have high shelter trees, miscanthus is ideal,” Cox said.
He is keen to see farmers pick up on crops like miscanthus and start looking at fuel as a third income stream to complement their traditional fibre and food income streams.
