Robert Rapier has his “Renewable Diesel Primer” up on his site R-Squared Energy Blog and its in Mr. Rapier’s classic technologically top form. It’s a read and bookmark kind of page. If you use diesel, sell, or invest in the market this is a great piece to have ready access to and for giving to others. Keep in mind that the point of the piece is to address the cold weather attributes of alternative diesel sources. But it’s not a buyer’s guide by any means. More on that further down.

It’s a primer, very basic. And the engineer in Mr. Rapier comes through in his good form, helping others understand the attributes of fuels. But Mr. Rapier has an agenda that runs contrary to his expertise. The primer is based on a chapter he wrote for “Biofuels, Solar and Wind as Renewable Energy Systems: Benefits and Risks” a book edited by David Pimentel. The book is very expensive and surely is outdated now. Not on my list by any means.

Without an explanation of petroleum diesel which is a middle distillate from crude oil that varies from kerosene up to C15 long molecules that are thicker than jet fuel, Rapier’s work covers the renewable diesel products from “biodiesel” and “green diesel,” which he does make clear is chemically the same as petroleum diesel and finally straight vegetable oil which is really one of the bio diesel forms. Confused?

As a practical matter Mr. Rapier could simply reorganize the page. But the page is well written enough that just reading it will provide good information. Petroleum diesel and its chemical twin green diesel are simply two paths to the same result. Rapier explains adroitly just what the two existing paths are to get green diesel. The green diesel segment is well worth reading and keeping in mind.

Rapier makes clear that bio diesel is a different chemical. The brief and accurate description offered is a good view into what must be dealt with to get a product to market. For those with an interest in the chemistry, Rapier makes clear that oxygen in the main difference to the molecules in a comparison to petroleum or green diesel.

What goes unsaid is that bio diesel is a product of molecules that are consistent in the number of carbon atoms, whereas petroleum diesel and green diesel can be a mix of several molecules of different carbon atom counts so allowing the mix to work at varying temperatures. The other significant missing bit is the additive packages that can be added. Most any diesel buyer knows that as temperatures fall the needed diesel products will become lower in energy density and also operate at lower temperatures. Convicting bio diesel for lower energy values isn’t accurate unless compared to equivalent carbon counts. So some of Rapier’s assertions are off the mark. Nothing serious though.

A bit of thanks is due Mr. Rapier for new page on bio diesel. If it weren’t for buying into global warming those victims of diesel gelling both from overly high percentages of bio diesel and low proportions of low carbon atom count diesel products shipped too far north, there wouldn’t have been any problems.

But the problems offered Mr. Rapier an opportunity to shed some light on the market and what to look out for in the coming years. Remember, it looks like most of the very high productivity bio diesel ideas are going to be bio diesel, not green diesel.

Now for some buyer’s information. Contrasted to gasoline diesel is a more complex market. There is #1 and #2 diesel, both of which are slightly variable in their energy density due to temperature requirements. Truckers know this and routinely keep and use antigel additives to avoid trouble. In some cases its more cost efficient to buy #2 and use an additive than to mix #1. But filling up in Memphis and expecting to get to Minneapolis last week across a –30F patch of weather with tanks of #2 wouldn’t work. To use diesel, you have to have a basic knowledge and some managerial common sense.

The other matter is that some distributors are less than honest about their diesel mixes. Bio diesel is sold marked as “B2” or “B5” etc. with the number meaning the percentage of bio derived fuel. But unscrupulous sellers used much higher percentages of bio products using price signals to overdose the mix, so increasing their profits. As diesel is a long-term storage product for many, some consumers will have difficult problems that have little to do with bio diesel itself and everything to do with the honesty of the supplier.

Lastly is that the additive business hasn’t yet closed in on the high biodiesel percentage fuel mixes. A quick walkthrough a major truck stop’s stack of antigel products offered no information on biodiesel to start, which leaves considering the percentage of bio diesel simply mute. I can only assume they will catch on to what needs formulated and put information on the labels.

Today where the temperature can get below freezing using high percentage bio diesel mixes isn’t a good idea. Clear rules of how to mix high proportions of bio diesel with light petroleum diesel are not universally accepted. This will change. In the meantime the amount of bio diesel available isn’t in the kind of volume that would dictate big “B” percentages allowing time for the industry and if required some regulation to clean up the market.

But diesel requires more know-how to use than gasoline. A little management and common sense will always be needed however much the bio diesel share grows to be.


1 Comment so far

  1. Clean Diesel on January 29, 2009 12:58 AM

    Great information given by you and there is a lot of information about clean diesel and variations in diesel products.

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