Many readers of this site will probably also have an interest in railways. Thus many will have heard of the story of the UK’s narrow gauge railways using ‘yellow coal’ as a possible substitute for Welsh Steam coal which is no longer readily available. This brief article attempts to explain what has been going on and to consider how it could affect steam boating since the lack of coal is also a problem for those of us who boat.
In much of England it is common to see large fields with sweeps of yellow flowers swaying gently in the breeze in April and May. It is most likely that these fields will have been sown with Oilseed Rape, Brassica napus, which is a member of the mustard family, Brassicaceae. As the name suggests the plant is grown for its seed which is pressed into oil that is then used for cooking, to make soap and margarine and can also be used as a combustible fuel (diesel substitute).
The question that most people passing such fields might ask, but probably seldom do, is what happens to the crop next. In June and July the flowers complete their cycle and turn into seeds and the plants begin to die back. Thus in about mid July the crop is ready for harvest and those same fields are traversed by large combined harvesters that cut the stems, shake out the seeds and fill trailers with the crop for return to the farm sites. The average yield of seed per hectare is about 3.4 metric tonnes. Generally, farms will have grain stores into which the seeds will be placed until they are either sold on or pressed into ‘own brand’ farm based oil for food use. The storage stage may also include drying the seed down to 6-8% moisture at which level they can be stored safely for some time.
Besides food use the other main use for rape seeds is for bio diesel (B100 Biodiesel RME Premium). This is made from seed that might otherwise be processed as a food product and thus there are some serious questions about the morality of this use. The market price for oilseed rape on 3rd June 2024 was £528.99 with the market reports suggesting that demand as a fuel stock was rising and pushing up the price. This brings the food versus fuel debate into sharper focus.
The seeds are not simply poured into a press as one might at first expect. They need to be ‘fractured’ first and then go through a de-hulling process which removes the extra fibrous material and weed seeds. Once that is done the seeds are ready to be pressed. For food oil the ‘cold processing’ method requires temperatures to be kept below 27 degrees C. The pressing process removes 75% of the oil which is taken off to be filtered and stored and to settle out fine particles. The residue from the pressing process, known as ‘cake’, is a by-product that can be used for a variety of purposes. The bio-fuel processing does not apply the same approach as it uses solvents such as hexane to speed up the process. This method prioritizes maximizing oil yield and can extract up to 90% or more of the oil. However, both approaches leave the processer with a by-product; oil seed rape cake.
Rapeseed oil cake is a by-product that has all the properties that have dogged extractive industries over the years. To get a small amount of the valuable product a great deal of the by-product must be produced. However, unlike some by-products oilseed cake can be put to other uses.
One of the main alternative purpose is as animal feed since there is still quite a high oil content plus the fibrous material from food oil production. The bio-fuel cake has a much lower food value since it has less oil content and can be converted into fertiliser (compost) or low quality animal feed. The going market price for rapeseed oil cake as feed was £295 per tonne (Defra May 2024).
More recently the cake from food oil processing has been seen as having a potential as solid fuel for burning. One of the largest oilseed rape pressing company in the UK has developed briquettes that are approximately the same size as the coal used by narrow gauge heritage railways. The latter are finding themselves with serious problems as Welsh Steam Coal is no longer mined and the Russian war in Ukraine has stopped imports of Russian steam coal.
Tests have been widely carried out using the Talyllyn railway, the Lynton & Barnstaple Railway and several others to see if the material would make a good coal substitute. The reported results suggest that the time to raise steam tends to be somewhat slower, but in use the product is excellent, burning well with minimal ash. Like many of the ‘manufactured’ coal substitutes the yellow coal needs to be kept dry or it can turn to mush.
For this application an important issue is the cost of the ‘yellow coal’ as it needs to be comparable with the traditional Welsh Steam Coal that was normally used. That costs around £600 per ton, when available, but is becoming more expensive and in some areas unavailable. It has been suggested by some of the participants in the Yellow Coal experiment that coal is still the cheaper product with other coal substitutes such as Ecoal which is around £800 per tonne.
If oilseed rape briquettes will work for narrow gauge locomotives the next question is whether they might work in steam launches. The big difference is that the typical steam launch firebox is tiny compared to even a narrow gauge locomotive firebox. Thus to support steam boaters the producers would need to develop a smaller ‘house coal’ sized briquette. Another difference is that the narrow gauge loco will probably use 10 times more than the typical steamboat which can manage a day’s steaming on a bucket of coal. That means that the steam boater market is very much smaller than the locomotive market. However, given that the briquette size is also ideal for the domestic market it is possible that the combined demand might be viable.
Once again market economics will probably decide the final outcome. Domestic coal consumption is in competition with solid logs and composite logs which are widely available. At the premium end of this market are kiln dried logs and typical prices are as follows (June 2024):
Briquettes - £550 tonne Hardwood Logs £660 tonne
All oak logs £780 tonne All Ash logs £770 tonne
Oak/Ash mix £750 tonne Hornbeam - £780 tonne
However this is for logs sold in tonne loads which is quite unusual. Most local log merchants sell logs by the ‘tunny bag’ which in fact works out at around 250kg of logs of varying dryness. However even these sellers are charging around £560 per tonne. By comparison it has been suggested that ‘Yellow Coal’ could be perhaps £750 per tonne which puts it up in the same category as premium logs.
There is a big market for logs in much smaller quantities as few houses have the space to store a tunny bag of logs. Thus Yellow Coal would need to be sold in 20kg packs. Currently composite wood waste briquettes are offered at around £20 for a 20kg pack. If Yellow Coal could match that price it ought to be able to grab a share of the domestic market and thus be available to steam boaters. Perhaps we might yet see Yellow Coal in steamboats.
References
https://www.lynton-rail.co.uk/news/view/lbr-trials-ecoal-update
Various YouTube videos and firewood vendor sites.