Miscanthus – Renewable Diesel, the Fuel
Information article #13
2 May 2019
One of the many positives about Miscanthus is its ability to be used to make Renewable Diesel Fuel (RDF). In a general sense this was covered in the previous article but it does seem worthwhile to expand somewhat on the fuel itself and the use of Miscanthus for this purpose.
Firstly you need to know what RDF is. The important thing to remember is that it is not biodiesel. Biodiesel is so different from fossil fuel diesel that it has to have its own set of specifications. In most jurisdictions because of this significant difference, it can only be blended with fossil fuel diesel up to 5% biodiesel.
On the other hand, RDF from Miscanthus and other cellulosic feedstocks, is a direct and complete substitute for fossil fuel diesel. A sample of RDF that had been made from Miscanthus in the USA has been checked against the New Zealand diesel specifications by Independent Petroleum Laboratories Ltd (IPL) at Marsden Point. The IPL report showed that it met all of the New Zealand standards other than physical density. But because RDF has higher energy density the amount of energy per litre of RDF is equal to or perhaps slightly higher than the amount of energy per litre from fossil fuel diesel. The fact that each litre of RDF is lighter than a litre of fossil fuel diesel was thought by Miscanthus New Zealand Limited (MNZ) to be an advantage rather than a disadvantage. So it is hard to understand why physical density is included in the New Zealand specifications at all. The Minister of Energy needs to change or perhaps remove this.
One of the very important things about RDF is that its use does not impact in any way on diesel engine manufacturers’ warranties. RDF is produced and used commercially in the USA, and California also imports large quantities of it from Singapore. It is used extensively in the USA where its green credentials are fully understood and valued.
RDF is also better than carbon neutral because as mentioned in the previous article, one of the key co-products is biochar. As long as the char is not burned, biochar effectively represents permanently sequestered carbon. So use of RDF is significantly better in terms of greenhouse gas footprint than even New Zealand electricity which, while excellent by world electricity standards, is not carbon neutral. In addition, the tailpipe emissions from use of RDF are significantly less than those from engines using fossil fuel diesel.
In the USA, the Environmental Protection Agency has approved RDF for sale and use as diesel without any constraints. So it is mystifying that New Zealand officialdom and politicians seem determined to ignore these issues. One would have thought that they would be promoting the production and use of RDF, particularly when made from Miscanthus.
The first RDF plant to be set up in New Zealand is, with current plans, to be based on 100% Miscanthus - apart from some initial short-term feedstock supply from alternative sources. But it is likely to export its RDF to California rather than have it used locally. This is because in spite of the transport cost, extra revenue from renewable energy credits can be generated by sale of such a recognised renewable carbon-friendly fuel in the USA. It works out to three times the price that we are assuming for New Zealand so it can significantly improve the already good economics of RDF production.
Other feedstocks produced in New Zealand are also likely to be used in future RDF plants. These feedstocks will include forest industry processing residues such as wood offcuts or chips. Cereal straw which is produced in large quantities in Canterbury without a good market for the quantities involved, could also conceivably be used. A plant that is currently operating in Tennessee, is using wood chips. Radiata pine chips have been successfully evaluated through the RDF system there. Another plant that uses the same system to produce electricity has been operating for some years using switchgrass as the feedstock.
In the view of MNZ, New Zealand needs to start getting serious about greenhouse gas emissions. Part of this is the need to recognise the net benefit of growing Miscanthus in New Zealand and having it processed regionally into RDF which can then be used locally. Users of diesel will then be able to benefit from a locally produced price-stable fuel that is better than carbon neutral and is made from a local “green” feedstock.
So the more that RDF is produced and used in NZ, the better will be NZ’s carbon foot print. But with the current NZ emissions trading scheme rules, converting land to Miscanthus either receives no benefit whatsoever or, if the conversion is from pre-1990 plantation forest, it attracts a penalty! This is in spite of the fact that Miscanthus is capable of absorbing at least twice as much CO2 from the atmosphere as radiata pine.
Perhaps Shane Jones with his Provincial Growth Fund may eventually wake up to this and encourage investment in RDF production from Miscanthus in New Zealand.
The next article will be about high quality Miscanthus biochar.