064 - Back to School - USLD and Corrosion

In this educational episode, Erik Bjornstad explores the relationship between biodiesel and corrosion in fuel systems. He explains that while pure biodiesel (B100) can have corrosive properties, the common low-percentage blends (B2-B20) used in today's diesel fuel don't pose significant corrosion risks.

The episode clarifies that modern fuel systems using materials like stainless steel and aluminum are well-equipped to handle these blends. The real concerns with biodiesel additions center around increased water retention and potential microbe growth, rather than corrosion issues that are more commonly associated with higher-concentration blends.

What You'll Learn:

• The definition and composition of biodiesel blends
• Why biodiesel is added to conventional diesel fuel
• The truth about biodiesel's impact on fuel mileage
• Water retention properties of different biodiesel blends
• How biodiesel affects modern vs. older fuel systems
• Real concerns vs. common misconceptions about biodiesel
• Impact of different biodiesel concentrations on corrosion

Ideas Worth Sharing:

Here are three notable quotes from the podcast episode:

• "Virtually all the diesel fuel that you get has some amount of biodiesel in it, usually between two and 5%."
• "A B5 blend can hold 70 percent more dissolved water than what they call a B0 fuel without any bio in it."
• "Studies have shown that lower level biodiesel blends like B5 and B20 generally do not exhibit the same level of corrosiveness as a B100 does."

Resources Mentioned:

• ASTM D975 (fuel specifications)
• Renewable Fuels Standard Legislation
• Erik Bjornstad: LinkedIn

Show Notes:

[00:00:00] - Introduction and episode overview
[00:01:00] - Definition of biodiesel and blending basics
[00:02:00] - Reasons for biodiesel addition in fuel
[00:03:00] - Addressing common misconceptions about biodiesel
[00:04:00] - Water retention properties of biodiesel
[00:05:00] - Microbe problems and corrosion concerns
[00:06:00] - Chemical properties and metal interactions
[00:07:00] - Effects on rubber and plastic components
[00:08:00] - Analysis of different biodiesel blend impacts
[00:09:00] - Real concerns vs. theoretical problems
[00:10:00] - Episode summary and outro

Episode Transcript

(00:00):
Welcome to the Fuel Pulse Showpodcast, where we talk about all
things fuel for all kinds of people.
I'm your host, Eric Bjornstedt,and I'll be your guide through
the ever changing world of fuel.
Today, it's another episode of the FuelPulse Show Back to School, where we're
going to talk about some other aspectsof ultra low sulfur diesel fuel that we

(00:22):
didn't really get a chance to get intobefore in previous episodes, and that
is the influence of biodiesel on them.
Now, biodiesel is the term for fats oroils that have been chemically converted
into a fuel that burns like diesel fuel.
You can make biodiesel from virtuallyany kind of fat or oil, which is

(00:43):
why you hear about biodiesel madefrom soy or canola or chicken fat.
But the term biodiesel is alwaysgoing to refer to the 100 percent
converted fat, what they call B100.
But, you can take that B100 biodiesel,and you can mix it or blend it into

(01:04):
diesel fuel at a given percentage,and when you do that, it's now a
biodiesel blend, despite the commonreference to it also as biodiesel.
biodiesel.
So we mentioned before on other episodesthat virtually all the diesel fuel that
you get has some amount of biodieselin it, usually between two and 5%.

(01:28):
Now they don't label it because such a lowlevel of bio content doesn't materially
change Any of the core specificationsof that number two diesel fuel.
And if it still meets the corespecifications defined in ASTM D975,
they can still call it diesel fuel witheven with that little bit of bio in it.

(01:50):
Why do they put it in there?
Well, they do this for two reasons.
First reason is it helps meet therequirements of the renewable fuels
standard, which is the legislationfrom Congress that defines each year,
how many gallons of renewable fuelsmust be used by the country for 2024.
Second big reason is adding just thatlittle bit of biodiesel, restores,

(02:14):
any lubricity lost from processingthe fuel to take out the sulfur.
So by adding that little bit ofbiodiesel, you actually get to kill
two birds with one stone, so to speak.
Now there are some goodaspects of biodiesel.
like we just named, but it's hardto avoid talking about biodiesel
without mentioning its downsides.

(02:35):
Now, they used to key in onaccusations that biodiesel blends
cut into fuel mileage and alsothat they had poor stability.
So let's address thoseones first real fast.
Yes, biodiesel does have a lowerenergy content than straight petrodiesel
does, but really the difference isn'tgoing to be that much to worry about,

(02:59):
especially when you're talking just 2to 5 percent or even going up to 20%.
The mileage difference justisn't that meaningful, so we
don't really worry about it.
And neither is thedifference in stability.
Some kinds of pure biodiesels do havestability problems because of some
aspects of their chemical makeup.

(03:20):
But when you start blending thoseinto diesel fuel at those typical low
concentrations, any stability probleminherent in that biodiesel just materially
isn't gonna affect the overall blend.
Now, beyond those, you most commonlyhear three other critiques of biodiesel.

(03:42):
It's linked to corrosion, it's linked tomicrobes, and it's propensity for water.
So let's take the last two ones first.
If you're talking about straightB100 biodiesel, it definitely
has more water problems thanstraight ultra low sulfur diesel.

(04:03):
That has to do with how much dissolvedwater the biodiesel can hold.
B100 can hold around 1, 500 partsper million of dissolved water.
That compares to ULSD toppingout at between 100 and 200 ppm.
So just from the beginning,that's a big difference.

(04:25):
Having just 2 5 percent biodieselstill means it holds more water than
straight ULSDs without any bio in it.
A B5 blend can hold 70 percent moredissolved water than what they call
a B0 fuel without any bio in it.
And that's gonna matter because Youhave temperature changes that the fuel

(04:49):
goes through , that extra dissolvedwater that got in there during the day
is going to come back out of the fuelat night, building up as free water
over time in the bottom of that tank.
So even just blending thatlittle bit of bio, which doesn't
sound like a whole lot, it doessubstantially increase water problems.
in ULSD, which also means it substantiallyincreases microbe problems as well, since

(05:15):
microbes can grow and thrive virtuallyanywhere that there's free water.
And then that brings us back to thethird perceived problem with biodiesel,
the rumor that it's corrosive.
So, we should not only ask, is biodieselactually corrosive, but also we
should ask, at what level of biodieselcontent do you really have to worry

(05:38):
about that kind of problem emerging?
The truth is, just like with any otherkind of fuel, biodiesel does have
certain chemical properties that doinfluence how it interacts with the
metal and the rubber materials commonlyfound in engines and fuel systems.
But having said that, does that meanthat we should conclude it's corrosive?

(06:00):
In reality, you could say that biodieselis corrosive for a couple of reasons.
Now, first reason is it's inherentlyless stable than petroleum diesel.
We touched on that briefly earlier.
So it is more prone to undergooxidation reactions, and those
oxidation reactions will create bothacidic compounds, and they'll also

(06:23):
create these peroxide compounds, bothof which have the potential to be
corrosive to metals in the fuel system.
Although, having said that, thisis a bigger problem with older fuel
systems that use things like brass,and tin, and copper, and zinc.
In the newer systems, the metalsthat tend to be there are stainless

(06:44):
steel and aluminum, both of whichare inherently less reactive and
more resistant to corrosion fromthat kind of oxidative degradation.
So the answer to the corrosion questionfor biodiesel is both yes, but also no.
Biodiesel does also haverecognized effects on certain

(07:05):
kinds of rubber and plastics.
Again, a bigger problemin the older fuel systems.
Some materials like nitrile, rubber,and PVC, they can absorb fuel, which
causes them to swell and degrade.
And that's a problem.
For the kinds of things that they'reused in these systems, but the newer
materials in the newer systems,things like Viton, Teflon, HDPE,

(07:28):
they're more resistant to this.
And so they don't actuallyhave this problem.
So having said that, we have to stophere and we have to ask the question,
are these problems with biodiesel blendsgoing to show up at the concentrations
that you are likely to be working with?
Remember, conventional diesel isgoing to have 2 percent or 3%, maybe

(07:52):
up to 5 percent biodiesel in it.
That's what we'd say is a low level blend.
Some areas you may come across 20percent biodiesel, what they call B20.
But the right question to askis not, is biodiesel corrosion
with B 100 going to affect me?
No, the question really should be, iscorrosion and metal or rubber degradation

(08:16):
a problem with B 2 or B 5 or B 20?
The answer to that is pretty clearly no.
In lower blends, lower level blendslike B 10, B5 and B20, the biodiesel
content is significantly dilutedwith regular petroleum diesel.
And that means the blend is less likely toform those acidic or corrosive compounds

(08:41):
versus comparing them to pure biodiesel.
And they're also less likely tocompromise the rubber and plastics, too.
Studies have shown that lower levelbiodiesel blends like B5 and B20
generally do not exhibit the samelevel of corrosiveness as a B100 does.
Their effect on rubbers andplastics and metals is basically

(09:05):
the same as regular ULSD.
No, so you don't have to worry about that.
Instead, what you need to worry aboutare how the changes to the ultra
low sulfur diesel itself, how thosechanges lead to stability issues and
water issues and affinity for microbeproblems, all things that you do really

(09:26):
have to pay attention to as opposedto worrying about corrosion in that
little 2 percent of bio that's in there.
So, in summary, It's very rareto encounter diesel fuel that
has 0 percent biodiesel in it.
Virtually all diesel fuel has at leasta small amount of biodiesel in it.
Put in there both to increase the amountof renewable fuels we use as a country,

(09:49):
also to help restore lost lubricity.
Biodiesel itself has a reputationfor problems like being
corrosive or being unstable.
But while those may be true forhigh concentration biodiesel like
B100, Those problems don't showup in diesel fuel unless you go
above a 20 percent threshold.

(10:12):
Below that threshold, you justhave to worry about the problems
that the regular ultra low sulfurdiesel fuel has on its own.
So, that's going to do it fortoday's Fuel Pulse show, back
to school, quick dive into thequestion of ultra low sulfur diesel.
biodiesel and corrosion.
If you liked what you heard and youhaven't done so already, feel free

(10:33):
to subscribe at your podcast platformof choice, whether that's iTunes
or Stitcher or Google Podcasts orwherever you happen to like to listen.
Leave us a review if you can, because thatreally does help other people find us.
So until next time, I am Eric Bjornstedtthanking you for joining us, and
we'll see you next time, the nextepisode of The Fuel Pole Show Podcast.