Miscanthus – for boiler fuel

3 April 2019

The international norm for use of Miscanthus on a commercial scale is as boiler fuel and particularly for generation of electricity. This is already done on a large scale in the UK. It is also happening in Europe. Alain Jeanroy, the president of France Miscanthus has said that the area of Miscanthus planted in France is expanding at 10% per year and two thirds of their production is used for boiler fuel. There is over 5,500 ha of Miscanthus growing in France. In the UK there is considerably more.

In the USA Miscanthus plantings are expanding, with one major project being at the University of Iowa which is moving to become carbon neutral. Miscanthus will play a large part in this process.

So use of Miscanthus for boiler fuel is well established internationally and Miscanthus New Zealand Limited (MNZ) sees no reason why New Zealand should not be able to follow suit and try to catch up to some extent. But because NZ boiler operators are generally completely unfamiliar with Miscanthus, they often do not make the effort to search out information about it that is available on the Internet. This information can teach them how they can use Miscanthus as carbon neutral (or better) boiler fuel.

But there are a few enlightened companies around. One of the first businesses to plant Miscanthus in NZ was Carter Holt Harvey – now Oji Fibre Solutions (Oji). They established an area adjoining the Kinleith pulp and paper mill and used the annual harvest to evaluate use of Miscanthus through their boiler system. The first time it was used, there was a small problem in that the Miscanthus – straight from harvest - was considerably drier than fuel they had previously used. So over time they have determined the best combination of their normal much wetter fuel and Miscanthus, to enable the boiler to operate efficiently.

Farms in the vicinity have not yet taken up the idea of growing Miscanthus, largely, in the opinion of MNZ, because the price that is offered by Oji for Miscanthus as feedstock for their boiler is too low. But in actual fact, alternative uses of the harvested product from the Kinleith site have already shown themselves to be very profitable. However Oji still deserves a lot of credit for taking the chance on what was then an unknown crop in NZ and getting a moderately good stand established. We were all learning the techniques of establishment at the time so it is far from perfect, but in the 2018 season it achieved in the order of 20 tonnes of dry matter per stocked hectare.

MNZ has now been approached by three major dairy groups in NZ about the possibility of using Miscanthus to replace coal. One dairy processor already has in the order of 6 ha planted - with plans to plant more in 2019 and 2020. Another has planted a couple of tiny trial areas while a third is looking seriously at the possibility of growing its own Miscanthus at some scale. One of the advantages to such a business of growing Miscanthus adjoining the dairy factory is that the dairy factory effluent can be spray irrigated onto the Miscanthus with a dramatic reduction in nitrogen leaching. At the same time a useful carbon neutral biomass product will be produced for their boiler.

MNZ has detailed analyses showing such things as ash fusion temperatures (980 - 1540 (softening temperature) for Miscanthus versus 1060 – 1170 for coal). Miscanthus ash content is significantly lower than coal while Miscanthus gross calorific value is only slightly lower than the gross calorific value per tonne for commonly used NZ boiler coal. Miscanthus ash can also be incorporated into soils.

It is probably not overstating the case to say that Miscanthus is an extremely useful addition to the variety of products that can be used as feedstock for boilers. When this is combined with its nitrogen catching ability while growing, it is a very logical choice for some industries. Dairy processors, meat processors, breweries, etc, that produce high nitrogen effluent but also have a need for industrial heat, can benefit significantly from Miscanthus. There will be another article coming out later in this series, specifically on this.

Potential users should remember that there is a wealth of experience internationally that can be drawn upon because in the northern hemisphere businesses are clearly using it successfully for boiler fuel for a variety of purposes. Feedstock format covers the whole range from bales through to pellets.

The Bioenergy Association of New Zealand (BANZ) has been actively promoting use of biomass for boiler fuel for quite some time and there are a several very experienced engineers within BANZ who can provide advice about wood fuels in general. They will be able to get themselves up to speed very rapidly in relation to use of Miscanthus. The beauty of Miscanthus is that as shown in earlier articles in this series, it performs many other valuable environmental functions while producing the biomass and it is not dependent on the market for other products in the way that forest industry residues are.

The next article will be on the use of Miscanthus for bedding. It is an article that all farmers and other landowners should make a point of reading.

ENDS

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