Over the past decade, biodiesel has established itself as a greener alternative to mineral diesel. The requirements of this novel fuel are easy enough to accommodate, but switching over will entail some changes to your storage regime.
Biodiesel is, as the name suggests, extracted from farmed produce. Most of the biodiesel sold in the UK comes from plant sources, but some biodiesels are extracted from animal fats. Incidentally, did you know that, before the advent of the mineral oil business in the late nineteenth century, whale blubber was the most popular source of lamp oil?
Diesel from plant and animal sources tends to expire faster than the mineral oil variety — just as you’d expect. Take your supplier’s advice on storage times, and look for another fuel if you’re setting up an emergency backup generator for a remote site.
There is an upside to biodiesel’s relatively short lifespan. Spills will biodegrade more quickly than you’re used to. If your storage area is particularly busy, you may find that switching to biodiesel makes it a little easier to keep things clean and tidy.
All diesels are susceptible to microbial degradation, but biodiesels seem to suffer more than mineral equivalents. Microbes mean sludge, blocked filters, and increased maintenance. Minimizing your fuel’s exposure to water will help to control them. And, if you’re not already using a biocide to inhibit microbial growth, this may be the time to start!
Even when you have microbial contamination under control, water and biodiesel make a bad combination. If the water content of your fuel exceeds 1500 parts per million (ppm), the excess will emerge as acidic ‘free water’, rusting engines and storage tanks.
Some strategies against water contamination are obvious — like getting your storage tanks cleaned and dried before filling, and draining off any free water that has accumulated as soon as you detect it. You should also be aware that biodiesel absorbs moisture from the air, so that water is always going to be a problem. Minimizing the air gap above the fuel will help reduce these negative effects – allow just two per cent of the tank volume for thermal expansion.
Even when water contamination isn’t a factor, biodiesel displays a tendency to oxidize on contact with the air, leading to sedimentation and clogged fuel filters.
Unfortunately for UK companies, oxidation is more common in biodiesels derived from vegetable sources than in the animal fat variety, especially if the fuel has been bleached or deodorized to remove antioxidants. Once again, minimizing the air gap will help, but your best defence is to keep storage times as brief as possible.
Time and tanks
We’ve seen how throughput impacts both oxidation and water contamination. If you have to store biodiesel for more than a few months, you should consider adding chemical stabilizers. Your supplier will advise you on a product that’s appropriate for your particular blend.
In fact, your switch to biodiesel should be a cue for a full review of your tanks and pipework. Since biodiesel is more likely than mineral diesel to react with its storage vessel, you should eliminate any copper, brass, bronze, lead, tin or zinc componentry that may be lurking in your system. (Stick to aluminium, steel, plastic and fibreglass.)
Alert: biodiesel can attack some older rubber hoses, gaskets, and seals. Here’s your opportunity for some in-depth preventive maintenance!
Freezing and gelling
We’ve saved the biggest storage issue until last…
All diesels have a tendency to gel at low temperatures. Gelling is bad news for engines. It causes the formation of drifting, needle-shaped crystals, blocking fuel lines and filters. Biodiesels are more likely to gel than mineral equivalents, and some of them will do so above the freezing point of water. As a result, an English winter can be a challenge for biodiesel users.
The problems of gelling can be obviated by careful tank design. In the long term, this might mean underground storage, in-tank heaters, or insulated jacketing. In the short term, a chemical anti-gelling agent is your best defence. Just remember to add it before gelling has taken place!
If you’d like to find out more about our biodiesel storage solutions, get in touch with our expert team on 01264 243116.