This course is designed to introduce students to the issues of energy in the 21st century – including food and fuels – which are inseparably linked – and will discuss energy production and utilization from the biology, engineering, economics, climate science, and social science perspectives. This course will cover the current production and utilization of energy, as well as the consequences of this use, examining finite fossil energy reserves, how food and energy are linked, impacts on the environment and climate, and the social and economic impacts of our present energy and food production and use. After the introductory lectures, we will examine the emerging field of sustainable energy, fuel and food production, emphasizing the importance of developing energy efficient and sustainable methods of production, and how these new technologies can contribute to replacing the diminishing supplies of fossil fuels, and reduce the consequences of carbon dioxide release into the environment. This course will also cover the importance of creating a sustainable energy future for all societies including those of the developing world. Lectures will be prepared and delivered by leading UC San Diego and Scripps Institution of Oceanography faculty and industry professionals across these areas of expertise.
Office Hours- Algae Biofuel with Stephen Mayfield
Loading...
From the course by University of California San Diego
Our Energy Future
398 оценки
From the lesson
Office Hours
Recordings of live office hours from Dr. Mayfield and other course lecturers.
Meet the Instructors
Dr. Stephen MayfieldProfessor of Molecular Biology
University of California San Diego
[COUGH] Okay.
Welcome to week five, welcome to week five Hang Out.
You got just me today.
No no, no guest on the tonight show.
Looks like we've got some good questions though that a few people have sent in.
So we'll, we'll go through a couple of those.
First just want to say,
you know, thanks to everybody for you know sticking with the class.
You're half way through we've got about 9,000 students taking it right now.
That that's a good number.
Really glad for the questions we've, we've received so far.
And keep up the good work.
And then of course just on interesting topics for
the week the price of oil obviously has been in the news a lot.
81 bucks a barrel today.
It's kind of interesting for
me to read all the all the commentaries on why oil has gone down.
Some people think the Saudis are you know trying to teach the frackers a lesson,
other people are you know, just think the Saudi's are trying to keep you know,
market share.
And so they're keeping the spigots open and not shutting it back down.
Lot of, lot of kind of interesting discussion on whether $80
a barrel whether fracking can survive that or not.
You know, many many reports that I've read say that oil has to be about 85 bucks
a barrel in order for the average fracking operation to be commercially viable.
So I guess we'll know, we'll know in the next quarter.
I mean you, you, you can run a while without making a profit but
you can't run forever without making a profit.
And so I think what we'll,
we'll know in about another you know, probably, probably in early January.
I, if the price stays down to 80 bucks a barrel.
I, I guess we'll find out.
If, if there isn't much of a dent in fracking then I
would say they're probably producing at less than $85 a barrel.
People aren't always truthful with what it costs to, to produce things.
Sometimes it's your advantage to kind of say it costs you a little more than it
really does.
Then you, you don't seem like you're making such big profits.
And other times it's, it's actually better to say it costs you know,
less than it really does.
So you seem like you're, you're making a lot more profits.
That, that's especially true of companies that are out trying to raise money or
out trying to borrow money.
And a lot of the oil operations now, a lot of the fracking operations now
are running on borrowed money because it's not the big oil companies.
Chevron Exxon, British Petroleum,
they've all sold all their fracking properties last year.
They didn't think it was profitable when oil was 100 bucks a barrel.
It costs a lot more to, to let an oil well if you're
one of the big oil makers than it does if you're a little independent guy.
If you're a little independent guy,
you get away without paying health insurance for your workers.
You get away with maybe not being quite so you know, so safe in your operations.
You, you, you can do things a little cheaper a little quicker maybe sometimes.
A little you know, in general the safety record is,
is a little worse for the independents than it, than it is for the oil majors.
but, but I think it's really going to be interesting this,
this coming quarter to see what happens.
Unfortunately I think long-term there's no way the prices stand down.
In fact, there's a very famous oil guy named Harold Ham one of the big,
he made a fortune in, in Texas oil over the last 20 years.
Made several fortunes.
About, about 17 billion I think is what he's worth.
When last time I saw, he didn't get all of that from one oil company.
He bought and sold many oil companies over the time and
he had an interesting article in Barron's magazine earlier this
week which basically said oh look, this is short term.
Oil is, oil price is going to go back up to $100 a barrel and stay there,
that you know, the supposed over-supply is the overhang is what they
call it in the oil industry, the overhang is only about a million barrels a day.
So, that means that we're burning about 92 million barrels of oil, or
91 million barrels of oil per day, and we're producing about 92.
So you know, that, that's only about one what's that 1.1%
over production compared to you know, supply compared to demand.
But that, that's enough that it can impact the price and
it is right now but that can disappear pretty quick and, and his belief and
he's been in the business for a very long time is that that's going to disappear in
about another six months or may, maybe a year.
You know, as soon as it comes back.
So, it's really interesting.
I kind of like you know, following it just because you know, I've,
I've, from what I've read you know, fracking, you know,
was really profitable only at 100 bucks a barrel, and
I think at 80 bucks a barrel, these guys are going to take a beating.
And and, and like I said,
it's going to be really interesting to see if that's true or not.
So much of the energy industry I, I have to say it's just not transparent, right?
It's, it's really hard to tell how much oil is still in the ground and
it's really hard to tell how much it really costs to get out.
It's hard to tell who's selling what.
It's such an enormous industry.
Right?
I mean when you think about it, 91 million barrels of oil per day, per day.
Right? Changing hands around the globe.
It's just hard to keep track of all that stuff, so.
So, anyway, I will be watching that and keeping you guys informed.
But, that's not what we're going to talk about today.
You know, this week's lectures were all on sort of
biological processes including algae and so we got a bunch of questions on that.
And fortunately that's something that I happen to know about,
so even though we don't have a visiting you know,
lecturer to help answer these questions, I think I can take care of most of them.
Okay, so let's go down the list.
We'll pick this one first.
And what does it say?
It says our cyanobacteria diet comes in green algae ever combined in
the same commercial production ponds or bio reactors.
Or is it best to focus on only one type in each system?
So there is a couple ways to answer that.
And that obviously completely depends on who's producing it.
So I should say that the original ideas I think that most of the allege
oil companies had was that we were going to look like modern agriculture.
And modern agriculture is a monoculture.
Meaning you never go to a farm and see a row of corn and then right next to it
a row of soybeans and a row of, of wheat or something like that, right?
It's always rows and rows of corn.
And then, you know, in the same geographic area about maybe a couple miles away,
rows and rows and rows of soy bean.
So they can, those can grow in the same place.
They have a similar season.
So, why don't you do that?
There's, there's a couple of reasons but
the most important one is that the machines for automated harvesting, so
a corn combine, does not look anything like a soy bean combine.
And the plants come to maturity at different times, so it is impossible to
drive through a field efficiently if you're only harvesting two rows of
corn and then skipping a couple rows of soy bean and then harvesting corn again.
So because of that and, you know, people look at it early on and
said oh it will probably monocultures.
But it turns out that when you're growing algae in a pond and harvesting it,
it's, it's not really going through the same seed setting and
maturation cycle that terrestrial crops are, right?
Really what you do with algae is you just grow the algae up.
And they're, they're vegetatively dividing.
So they're not, you know, they're not setting seed, they're not going through
some developmental profile, they're just dividing every day.
You harvest all of those and then you extract the oil out of them.
Now mainly by hydrothermal liquefaction for the big guys.
So in that case.
You know, polycultures, as they're sometimes called, or
consortia other people call them.
Absolutely the way to go.
You can get increased productivity.
You certainly get increased crop protection.
Because when you think about it,
if you had five different species of algae in a pond, for example.
Okay.
And some fungus showed up.
That fungus is likely only to infect one of those five species.
So if a fungus infects one of those species and kills 20% of your pond,
you might imagine, well, I still have 80% of the yield.
But in fact what happens is you still get 100% of the yield,
because even though one of those five is decreased out,
light is the limiting resource, and when one of your, you know when one fifth of
your population goes away the others simply grow faster to make up for it.
So, in consortia, you get much more biological stability.
And that, that is really a good thing and really an important thing.
So, absolutely people are thinking about consortia.
they're, they're, they're thinking about growing multiple guys.
That's when you're making fuel.
If you are making a high-value product.
So suppose you're growing algae at large scale and you're going to harvest that.
And half of that is going to go to, you know,
well, whatever, 20% of that is going to go to oil for fuel.
And the other 80% you're going to ship down for animal feed or
something like that because you, you have a co-product in there.
In that case you have to have algae that are compatible with each other,
meaning that all of the algae that are growing in there have to be compatible as
animal feed.
And you know, with, with cattle that's always going to work.
I think, usually, because you know, un, unless it happened to be a toxic algae and
you wouldn't, you wouldn't put one of those in your pond.
But it didn't really matter.
It could be it could be cyanobacteria, and
all of those sort of get eaten by cows and digested.
Some of the algae that we grow are not edible by mono-gastric animals.
So what's a mono-gastric animal?
That's a human.
It means you have one stomach.
So a human and a pig, and a chicken.
Those are all mono-gastric.
And then other ones like you know, cattle they, they're ruminants.
That means they have multiple stomachs and
in one of those stomachs they have anaerobic digestion.
So they can breakdown cellulose mono-gastric animals can't.
So they're, they're generally a little more flexible on,
on the food they can eat but at, absolutely good question.
Now there is a company that is making ethanol from cyanobacteria,
called Algenol down in Florida, and theirs, because theirs is a single
type of cells secreting an ethanol, right now that has to be, mono-cultured.
I suppose someday they could come up with a consortion, you know, two or
three strains that are all taking sunlight, and, and secreting ethanol but
right now they only have one.
Okay, so, let's see, question number two here says,
can, can genetically modified algae, cynobacteria algae or
diatoms, if inadvertently released into nature cause natural ecosystem imbalance.
And then the second part is, is this part of your research process to access,
to, assess such risk.
So, we actually did an, an outdoor GMO trial this last winter.
EPA approved, that's the people who have to prove it.
First one in the world as far as we know.
And in that one what we did was we looked at two different aspects of
gianrolled algae.
So the algae we used is called senidoesmus.
And we put two, pretty benign genes into it.
We put a green fluorescent protein in, and we put that one in so
that we could follow it, even if it was, a very rare.
So, if, should, should it escape and we put traps all around the field so
that we could actually catch these guys when they escape.
But we could tell when it landed in that trap, you know,
what percent of the algae were transgenic with a really easy
flourescent screen because they were making green flourescent protein and
then we also put a second enzyme in it that altered lipid metabolism.
And we did that so we could identify could a trans gene
put into an algae and then put outdoors survive?
Because although what a very important question is do the, you know,
do the GMO algae escape and, and impact the natural ecosystem?
That's a very important question.
But an equally important question is do GMO algae still continue to
function outside or are they simply, you know, are, are outdoor environments so
harsh that we kind of kill, you know, we, we kill the poor little guys?
And and kind of a predictable thing showed up.
And that was we, so we grew the algae all of November and
December and, as I said, we put traps all around the field.
And what a trap is is just a bucket with media in it so
that if an algae lands in there it could grow.
So if a transgenic algae were to come out of the pond and
land in that trap we, we would be able to tell that.
And we put the pond, we put the traps at five meters, 25 meters, 50 meters,
100 and 200 meters in all directions away from the pond.
Now, what we found out was that over the two-month period, that the GMO algae
got into most of the five meter traps many of the 25 meter traps, and
several of the 50 meter traps.
They actually didn't make it up to the 100 or 200 meters.
Had we let the, the, you know, the trial go for, you know, for five or six months,
I suspect they would have got out to the, to the 100 and 200 meter traps.
But an interesting thing happened and that was that the minute we
put those traps out, long before the GM algae ever showed up,
even in the five meter you know, traps, they were dark green.
So wild type algae from who knows where, coming out of the air, coming out of bugs,
was already in the ground, raining out of the sky, we don't even know.
They immediately showed up, actually within about two days.
The traps started getting green and
within a week every trap, all the way out to 200 meters, was pretty dark green.
So that told us something a little shocking but
in retrospect, I guess something we should have predicted, and
that is that there's a huge amount of algae just blowing around in the air.
Perfectly viable, right, land in our traps and, and grows, and grew quite well.
Now we had any ecologist with us,
John Suran, who's here in at UC San Diego in the, in the ecology, department.
And we brought John on obviously because we wanted to
specifically address the question of what happens with the natural ecosystem when
a transgenic algae lands in that.
And John did a really important experiment, and that is that he went and
got water.
From five local water bodies.
And I, and I say water bodies, not lakes or rivers,
because we're here in San Diego which is, you know, more or less the desert.
And so our water bodies are not natural lakes,
they're reservoirs or manmade lakes.
So he went and got water from five of those.
Three of them have pretty clean water.
And then one of them has a little bit of nitrogen in.
And then the fifth one was completely nutrified, meaning that there was,
because of where that where that reservoir is
placed there's runoff from agriculture that gets into it.
And from, and from houses as well, it's not, not, not just ag.
But there, there's runoff of so that had relatively high nitrogen and
high phosphate in it.
So what does that mean?
That means when you went to that lake it was already pretty thick with algae.
The other ones were pretty clean.
So if you looked at them, they were pretty clear water.
Why is water clear in one lake and green in another?
It's simply the nitrogen and phosphate content of it.
So here in California,
if you go up to lake Tahoe it's famously very deep blue water.
That, the reason it's blue water is because it's an alpine lake,
it's high up and there's not a lot you know industry and houses around it.
So the, there's not a lot of nitrogen and phosphate that run into that lake.
It started to be a problem lately because septic tanks that people have,
who build cabins around the lake, that stuff eventually leeches down and
starts to get into the water and and so now there's been
some debate on how we control that so that it doesn't turn green.
So at any rate, John went and got these waters, and then what he
did was he inoculated, he brought them back, put them in a greenhouse and
then he inoculated into those our GM strain at continuing,
you know, at, in, in a series with ever increasing concentration of the algae.
And, and the idea behind that was one okay.
If, if you had an algae escape but let's just say you know a,
a, a pretty small amount of it escape.
Would that be able to get in and colonize these bodies of water?
Well what happens if you had a massive you know, escape, and I don't know why.
There was an earthquake and it cracked one of your ponds and
it, all of that pond ran down and got into the water.
So we also did some where you inoculated it really heavy.
And what he found out was that the GM algae, or the parent wild type strain, so
it was the senedesmus that we had and so we grew not only the GM strain, we also
grew the wild type non-transgenic parent side by side with it out there because,
again, we wanted to test how does a GM strain do compared to a wild type.
So, the GM and wild type grew fine.
The gene stayed in them.
The GFP continue to express for two months.
So that was good.
We could show that we had a stable phenotype and it got outside.
And then like I say really interestingly put into these waters the GM
algae could grow so you know, that, that, that's what you'd expect.
We, we, we hadn't you know sort of beat it up so
bad with the GM trait that we put in that it was incapable of growing.
It grew in those strains.
But importantly it could not out compete the wild type in any of those ponds,
even the ones that were eutrophied, even the ones that had a great nitrogen and
phosphate source.
It sort of got in,
it grow, it grew, it colonized, but it never overtook the other algae.
Now as I say not unexpected result,
because remember those other algae that, that are in those lakes and
reservoirs here in San Diego have been there for many, many, many, many years.
So they have been selected over many seasons over many years to
survive in that water with the set of nutrients that had is,
and the set of light that it gets and the temperature that it gets.
And so that those have, they have a clear advantage.
So when we put in the GM strain it's kind of expected.
That, that they really didn't do any better.
But it's kind of nice to know that you now it's, it's one of things that we've got to
check, we've got to be very careful before we ever you know release GM you know,
algae outside.
You know, you hear a lot of hysteria from people which is not science based,
where they say oh, you're going to make a Frankenalgae.
You know, you'll make some algae that'll go out and take over the ecosystem.
And the truth of the matter is that, that's simply not true.
There, there's no domesticated species that we
ever release anywhere that goes and it takes over a natural environment.
And there's a really simple biological reason for that.
And that is that a domesticated species specifically means that you have
taken a wild type species and converted part of its metabolic flux, so part
of the energy that it makes, into making something which is beneficial for you.
So the simplest way to think about this is corn,
which is a grass, right, in traditional corn we have domesticated that so
it makes this enormous cobb, you know, with lots of seed on it.
Well when you do that you put a lot of your energy, you know,
the plants energy, a lot of it goes into making that really big cobb.
That doesn't make it more competitive in the environment with other grasses.
In fact you know I, I always tell people well look you're worried about GM algae I
understand that, we, we need to patch it up we need to be careful.
But you honestly think if you took a handful of you know American
domesticated corn seed and went down to the jungle in the Amazon and you know and
threw that seed all around that you'd come back in a couple years and
the whole place would be GM corn or corn.
No.
What would happened is, you'd throw that seed out there and all the animals there
would say, thanks very much for lunch, and they would eat it immediately.
And if, by chance, it did grow up, it would very quickly be
attacked by fungus and bacteria and all the rest of this stuff, because it
hasn't evolved to have a competitive advantage in that specific environment.
So, we always have that going for us in, in, in any kind of G.M.
strain that we put outside.
All of the things that we do, all of the domestication that we do that makes it
more beneficial for us, makes it less beneficial for the environment.
Where we have had problems and this continues to be a problem to this day,
is bringing in non native species, right?
And anybody who happens to be a scuba diver knows that if you now go to
the Caribbean and go scuba diving there, low and
behold there are lion fish everywhere.
They are not native to the Caribbean, they showed up because people bought them for
their aquarium because they are kind of cool looking fish and when they got
bored with them rather than you know kill them they decided oh well just go let them
go in the ocean and they did that and now they have colonized the entire Caribbean.
So why did they survive and you know and others not?
The reason for that is because where they come from which is Indonesia,
over there there are natural predators.
You know they evolved and they, they grew up there over tens of thousands,
hundreds of thousands of years, and as they did, even though they
have these nice little toxic spines and can't be eaten by you know every fish.
Some fish have, some other predators have figured out how to eat them.
And those predators do not exist in the Caribbean.
So when you bring something like that in, a non-native species that's already gone
through all of this selection to survive in an environment and
has a nice little thing like a lionfish do which is their beautiful you know
fins with their little toxic ends on them, then that does cause trouble.
So I'm much less worried about a GM algae you know escaping and causing trouble,
as I am a non-native species of algae brought into a new environment.
So I think the bad idea is to go bioprospecting for some algae in Utah.
You know, and
then bring it over here to California, that might cause problems, right?
But, but the GMs, at least to date, you know,
look like they're going to behave just the way GM crops do.
Which is they're going to survive outside.
They're going to be stable, but
they're not going to dominate any environment that they have to get at it.
And I should say, they are going to get out.
Right?
This, this idea and I've heard many people you know, sort of say, oh,
well, what we need to do is have these, you know, these GM algae and
double secret probation, you know, where we keep them inside photobioreactors and
then keep that inside a secondary containment.
So if you do that, you,
you, you probably reduce the likelihood of having a large spill.
But you're still going to get small stuff out there.
That's just the way it goes.
Nothing stays in captivity forever, right?
Anybody who's ever had any pet snakes knows that,
and I've had many you know, king snakes.
They they're beautiful little animals and you put them in a thing and
then somehow they miraculously get out.
Algae would do the same thing okay?
So it's, it's we have to plan that these things are going to escape.
And then they have to make sure that they do not cause problems to the environment.
And we're on our way to do that, okay, enough about that one.
Various approaches to growing, harvesting, and processing algae are complicated
enough, yes they are but from the lectures I am given the impression that anyone
pursuing bio-fuels from algae will need to have genomic skills, do you agree?
Okay, so that's, that,
that's, there, there's, you know, that, that's a gray area.
I would say that, certainly not
everyone pursuing bio-fuels from algae will need to have genomic skills.
That doesn't mean that genomic skills won't be something that is important for
you know biofuel production from algae so we,
we've got to do a couple things to make this economically viable.
So over the last several years a company that I started Sapphire energy but
several other companies as well you know Soul Design,
Algonal, Solona you know there, there are many out there.
Have shown that the proof of concept works just fine.
Meaning that we can grow up algae whether that's in bags or ponds.
We can grow algae.
That algae produce lipid.
We can extract that lipid from the algae.
We can convert that lipid into fungible, meaning drop in fuel.
So we can make diesel.
We can make gasoline.
We can make jet fuel from it.
So the proof of concept is done.
All that stuff works right?
Chatwood challenge, challenge is economic.
How do we get this to really large scale and
how do we ever compete with fossil fuel?
Because that's still really cheap even at 100 bucks a barrel,
it's relatively cheap and at 80 bucks a barrel it's even cheaper.
Okay? So how are we going to
compete with those guys?
Well there's a couple ways that we have to do.
You know one thing we've got to get,
the cap backs, meaning the money you pay to build the facility.
That price has to come down.
We cannot make these expensive ponds.
You know the, the sort of pond design that,
that we use here on campus for our you know, sort of our research, you know,
this lined with, with plastic and has a paddle wheel to push the water around.
Too much energy, too expensive to build.
We gotta get the cost of that down.
We've gotta find cheaper ways to motivate the water, as they say,
to mix the water so you get good gas exchange we have to get much cheaper
ways to do things rather than, than have plastic lined ponds.
So we have ways to do that.
We can do dirt lined ponds.
We can do, you know there's 375 million acres of rice paddies on the planet.
They seem to work really well and they're, they do not have plastic liners on those.
All right, so, there, there's a path forward.
We, we got to get that done.
That's part one.
Part two, we still have to increase bio mass shield.
So how do we increase bio mass shield?
we, we do it by prospecting, by going out and finding the best rains possible.
We do that by traditional breeding.
Meaning we cross strains together and
select for the ones that have the highest biomass yield.
And then I think we also have to have some genomic strategies in there as well.
Partly because the genomics strategies, you might not ever make a GM strain.
But the genomic strategies can still be enormously helpful because you can
now do what's called marker assisted breeding.
So, so by being able to look at the genome really quick, and then having
a correlation between a specific gene, or sometimes just a specific piece of DNA.
You don't even know what the gene is.
But that, that,
that, that locust, that piece of DNA correlates with high biomass shield.
Okay so if you look at that at the DNA level rather than have to
grow that out all the way up measure its growth rate,
you know, measure how it does in the environment.
So that's called marker assisted breeding or gnomic breeding so
those things help you do traditional breeding much quicker as well.
So, it I would say it's not a requirement that you know that everybody who
works in bio-fuels have that, but it will certainly be beneficial and
I think all of the companies that are thinking about doing algae to
bio-fuels certainly have a, a component of molecular genetics and genomics involved.
Then one other thing that we also get out of that and
that is co-products so, I spend most of my time, as some of you may know,
actually making really high value products, I make nutraceutical,
I make therapeutic proteins, I make animal feeds, I make vaccines.
All these things can be produced in allege.
None of those are fuel, okay, but all of those have the potential to
be co-products, which means I grow the algae up.
I harvest the protein out of it and
within that protein I have some high value animal feed protein in it, maybe it's a,
maybe it's a zilonaide, maybe it's a fitaides, maybe it's some other
enzyme that helps in digestion, maybe it's a nutrosuedical that just helps, you know,
helps, helps the animal feel better, or the human feel better, right.
I sell that protein as a high valued product and then I take the rest of
the biomass and through HTL, or some other process I convert that into fuel.
This is the only way agriculture works.
Right?
The expression in agriculture for pigs is in pigs you sell everything but the oink.
Right?
Meaning that if you have a pig and all you did was take the hams and
the bacon from that pig, you would go broke as a farmer.
You have got to sell everything.
You've got to sell, you know, the pork ribs.
You've gotta sell the pig feet.
You gotta turn those ears into dog treats or whatever you do with them.
You sell every single part of that animal.
And when you monetize every single part of that animal then you
can make a living with, with pigs and, and, and being a pig farmer, okay?
And so we have to do the same thing with algae.
There's no way you could think oh, I'm going to pull out algae.
I'm going to take the 30 or 40% lipid, I'm going to sell that as fuel and
then I'm not going to worry about the other 60% of the, of the algae.
You can't, you not only have to worry about it,
you have to make a profit out of that.
So that is co-products, and those co-products could be animal feed, but
they could be high value products as well.
Okay?
So, genomic skills help enormously on that front because then you
can engineer a really high value protein co-product to go with it.
Okay.
Next question,
diesel engines are well known to emit a lot more pollutants and particles.
Well, biodiesel from green algae or diatoms or cyanobacteria or jatropha emit
the same amount of greenhouse gas and pollutant that traditional diesel does.
Okay, so Fisa let me start out by saying the diesel
engines from years ago are well known to emit a lot more pollutants and particles.
And the reason for
that has nothing to do with the general properties of the diesel engine.
Diesel engines are in fact more efficient than gasoline engines.
And more efficient means they actually put out less greenhouse gas than
a gasoline engine.
What you're thinking about, and
the sort of traditional diesel engines that spew out all that black soot,
that is because a diesel engine just by its nature can run on lower quality fuel.
Doesn't mean it has to run on lower quality fuel.
It just means the way that a diesel engine works, because a diesel engine works by
compressing the gas and that gets really hot and then squirting the fuel in a, a,
as the cylinder expands so there's no spark to set it off.
And so when you don't have to do that you can actually put in lower,
lower quality fuel.
Because you're squirting it in and it's burning all, simultaneously.
So because of that you used to u, u, just for economic reasons we would use
low quality diesel fuel that would spew out lots of you know soot.
Lots of black particles.
You had sulfur in it.
You had a bunch of stuff.
That is no longer allowed.
That is no longer the case.
That is not allowed in the United States, that is certainly not allowed in Europe.
There are still trucks that drive down the road and
you will see those guys spewing black soot out the back.
That is because that truck probably has a 20 year old engine in it and
the states that that truck can come from,
they haven't forced it to upgrade to the higher quality stuff.
But that is absolutely not a, a component of a diesel engine.
A, a, a diesel engine can run perfectly clean.
You see these things now are sometimes referred to as clean diesel.
If you go to Europe where they have lots of these things,
you would have no idea if the car in front of you is driving on gasoline or diesel.
There, there is not more pollution coming out the tailpipe, okay?
So, but, having said that, what's the difference between a now clean diesel,
as they're called, that is running a petroleum-based diesel versus running a,
a biodiesel from jatropha or algae?
Once you get it into the gas station.
So, once you have made diesel, whether you made it from jatropha, or
whether you made it from cyanobacteria or algae.
It doesn't matter, okay.
It is indistinguishable.
In fact, you can tell the difference between the two of
them by very sophisticated sort of mass spectrometry,
because the molecules inside of them are subtly different.
But in terms of spec, what people call spec, which is fuel specification.
That means that those things are going to burn exactly the same.
So, algae based diesel, petroleum diesel are putting the same amount of CO2
out of the tailpipe on your clean diesel Audi no matter whether it's,
it's fossil fuel or algae fuel, okay?
The difference is that, that fossil fuel before it was pulled out of the ground,
that had CO2 sequestered underground.
So when you pull petroleum out of the ground, convert it to diesel,
you put out a certain amount of CO2 just by pulling it out of the ground and
converting it in a refinery, CO2's already going up.
Then you put it into a gas station and put it into your car.
More CO2 comes out.
That CO2 was sequestered underground last week.
Now it's out in the atmosphere, okay?
That's traditional diesel fuel.
Biofuel was, there was CO2 in the atmosphere two weeks ago.
Photosynthesis fixed all that CO2, put it into lipids inside the algae.
You harvested the algae, extracted the lipid from it.
Turn that into fuel and then that,
that CO2 when you burned it in the car went back out into the environment.
Okay, so what does that mean?
That means that you're recycling the CO2.
So we call that beneficial reuse of CO2, right?
That means that the CO2 that came out of the tailpipe for
biodiesel was in the air two weeks ago and now it's back in the air.
And then we just cycle that over, and over, and over, and over again.
Now, that's not a 100% efficient process meaning that we have to spend some energy
you know, to har, to grow the algae, to harvest the algae, to refine it, etc.
So, it, it's not that a lot, lot of people say that, that's carbon neutral fuel.
Meaning that it's exactly the same amount of CO2 out into the atmosphere that
was pulled out in photosynthesis.
That's not exactly right.
But there's about a 70% reduction right now in algae fuels.
Some people think cellulosic ethanol will get you an 80% reduction in CO2 you know,
total what's called a life cycle assessment of it.
so, you know, you basically get five, you know, five for
one you know, bang, bang for your buck if you're in a, in a renewable fuel, okay.
So, depends what you mean by pollution.
CO2 come out of the tailpipe is the same but it's captured,
you know, it was captured from, from the, you know, the air two weeks ago.
And if you release now it will be captured again when we grow the algae up next week.
Okay, okay here's one from Mitchell.
He's a good guy, he's always asking questions on here.
And he says, when bioprospecting for cyanobacteria green algae and
diatom, is your research limited to a general area or
more specific a latitude on which you expect to go into production?
So, when, when, you know,
I would say when people in earnest started to go out and do bioprospecting,
we had a general idea that it would be, you know, sort of a latitude, right?
That what we would do is we would go bioprospecting in, you know,
in Arizona, in Texas, and whatever, and we would get strains.
And, and we'd find the best one of all those and
then that would universally be deployed.
And that turns out to be not the way it worked out.
The way it worked out, is you almost always go to the local environment where
you're going to grow something.
So, with sapphire, they happen to be down in Las Cruces,
New Mexico, and in Columbus, New Mexico.
So they set up traps all around that.
They found a bunch of algae.
And lo and behold, the algae that you catch locally have already sort of
pre-selected to grow very well in that specific environment.
So they're growing well in that temperature, in that sunlight you know,
in that you know in,
in that elevation because that tells you how much UV you're getting and, you know.
So they, they, they sort of come pre-selected.
The other interesting thing that we found was though, that if you go prospecting in
Utah and you go prospecting in New Mexico and you go prospecting in California.
Although you will find a lot of different species of algae in there,
hundreds in each site that you go to, you find kind of a core 20 or 30 genuses.
So it's a different species, but a genus.
So, every place you prospect you will find scenedesmus.
Scenedesmus is, is the, is the genus.
And then the one we grow here is called dimorphous, that's the one we grow out in,
in our ponds locally.
And you will find a lot of scenedesmus, they're not all dimorphous,
some of them are scenedesmus elongatus, whatever species, but
you'll find a lot of scenedesmus, that genus always shows up.
Chlamydomonas always shows up.
Chlorella always shows up.
Dunaliella always shows up.
You, you, you sort of keep repeating,
it's clear that some species are sort of ubiquitous everywhere in the planet.
And so you know there's scenedesmus in Australia, there's scenedesmus in Florida.
They're in Europe, they're in the Middle East.
Tho, those guys just sort of seem to be everywhere.
Same with chlorella.
Different species, so when you sequence the genomes and compare them you realize,
oh these guys aren't identical but they're pretty close cousins.
So nowadays what you do is you simply go to a place,
you say I want to send up my pond here in the Imperial Valley.
You do bio, bio-prospecting all around that.
You'll find about 200 different species and
then pretty quick what you'll find out is, hey, I already know that chlorellas and
scenedesmus and maybe chlamydomonas are, are generally good growers.
Here's a couple of those guys.
Now I'm going to take the local ones and I'm going to grow them here.
'Kay?
Okay.
Here's the next one, and that says, are there already commercial facilities for
growing algae on wastewater?
So the answer to that is yes, and
we'll get back to a more deep answer on that in a second.
And what values of CO2, nitrogen, phosphate, or
other elements would be adequate for safe placement of algae and wastewater?
Okay.
So the first part of that is there,
there are commercial facilities that are growing algeon wastewater, but
their commercial facilities not to produce biofuel or some other bioproduct.
Those are commercial facilities in which they're using the algae to
pull the nitrogen and
phosphate out of the wastewater so that they're pulling the pollutants,
in this case nitrogen and phosphate fertilizer for the algae, but pollutants.
Right? For that wastewater,
to clean the wastewater up before you discharge it either out into the ocean or
pump it back underground.
That's called tertiary treatment.
It's now a requirement in, in California.
It should be a requirement everywhere but, but, but it, it's not yet.
Where in places where that, that is not a requirement and
hasn't been a requirement, what happens is if you go through secondary treatment, so
when wastewater comes into a facility, the first thing is called primary treatment.
And what primary treatment is, is you let the solids all settle out of it and, and
you, you, you just take the water off the top of it.
That's primary treatment, okay?
Secondary treatment is then I take that stuff and I put bacteria into it and
I bubble air through.
So, that's called anaerobic digestion, and what does that do?
That gets rid of all the organic carbon that's in there, and
there's a huge amount of organic carbon in there.
So that organic carbon means sugars, means acetate,
means all of the breakdown products, you know, that come from, you know,
what, whatever we poop and whatever else goes into that wastewater, okay?
A fair amount of cellulose, you know.
[NOISE] There's a lotta toilet paper that goes into that stuff.
And so bacteria will degrade all that stuff.
So that's called secondary treatment.
Then again you've got that bacteria, which is a solid settle out.
You take that water off the top.
That is now secondary treated water.
By the time you get to there, in general, you know, you, you've cleaned up 90,
I don't know 95% of the stuff that is in waste water.
You certainly got rid of all the pathogenic bacteria.
You've certainly got rid of, you know, all of the viruses that were in there.
At that point traditionally we have said, okay,
you can now safely discharge this, either here, you know in California, and
in many places you dump it down in the ocean if you're close to the ocean.
Or in other places you might dump it into a river or
you might pump it, pump it underground.
Okay?
Secondary treatment.
That water is still loaded with nitrogen and phosphate.
So if you do that, if you take that stuff and pump it back down into the water,
eventually, that is going to get back into the aquifer, and
if that aquifer, if you're pulling it out to drink it, will have nitrates in it and
nitrates in water are not a good thing for humans.
They're a great thing for plants.
So if you take that water, and you pull it out and use it for agriculture, benefit.
Right?
Nitrogen and phosphate, those plants are just waiting for it.
They're, they love inorganic nitrogen.
They love inorganic phosphate.
They take them right up and eat them.
Animals, like humans, do not take up inorganic nitrogen or
phosphate, so for us it's a bad thing, right?
In fact nitrogens interact with amino acids and
you get things called nitrosamines, and they're carcinogens.
So, nitrate in the water system is not a good thing.
We consider that polluted.
If you get above very low levels parts per million, 10 to 15 parts
per million of nitrogen in your water it's recommended that you no longer drink it.
Great for plants, but you shouldn't drink it.
So, if you take that water and feed it to algae, or
grow algae in it, the algae pull all the nitrogen and phosphate out of it.
Boop. Now that water can
go right back into the aquifer, can go right back into the ocean.
Where should that water go?
That water should go to a reverse osmosis system and be recycled.
Especially out here in the west where, where we are, you know,
sort of in desperate need of water, right?
We should be recycling that water.
We don't do that right now, mainly because people don't like this idea of
what out here we unfortunately one of our,
our mayor a few years ago called toilet to tap, right?
Meaning we're going to take waste water, we're going to,
we're going to do primary treatment.
We're going to do secondary treatment.
We're going to do tertiary treatment of algae.
Then we're going to put it through a reverse osmosis,
then you're going to drink it.
And people said I don't know about you, but I'm not drinking toilet water.
I don't care what you've done to it.
Now that's a little ironic, because you're allowed to dump it back underground.
You're allowed to pump it underground.
So in the city of Riverside, they get their water,
runs off the San Gabriel Mountains, which are just to the east of Riverside, so
they get a nice flow of water that comes off those mountains.
They pull that water in.
They use it in their city.
They take that water, they do primary treatment, they do secondary treatment.
And then they dump that water into the San Gabriel River.
The San Gabriel River flows from Riverside out to the coast in Newport Beach.
But the water dumped into that river, which is perfect, you know,
it's clean except its got a little bit of nitrogen and phosphate in it, right.
and, and now they're even they're, they're,
Riverside is starting to do tertiary treatment to get rid of that,
but any rate, that water they put in flows a little way down the river and
then it goes underground.
And in fact there is no running water for most of the year that ever
gets from Riverside and, and empties into the ocean in Newport Beach.
When we have a big, you know, in the winter time, when there's a big rain,
yeah, okay, you get rain runoff, that river flows all the way down.
But for most of the year it doesn't do that, it goes underground.
Where does it go when it goes underground?
It replenishes the aquifer that Newport Beach pulls out of the ground to use for
their drinking water.
So here in San Diego and
in a bunch of other places we say oh, we can't take, you know, wastewater and
run it through, you know, treatment and then do reverse osmosis and drink it.
But, miraculously, up in Newport Beach and Huntington Beach, you do exactly that,
except rather than directly do it, you sort of dump it
into the San Gabriel River and let it go underground and then pull it out.
And I don't know what they think.
May, maybe they think that running through all that sand in
the riverbed cleans it up better than reverse osmosis.
I don't really know, right?
I, I suspect most people just don't know that's where their water comes from.
How much of their water comes from that?
So much of Newport's water comes from that, that when
the city of Riverside a couple of years ago decided that, that water was so clean,
you know, that they were dumping back into the San Gabriel.
That they were better off running it through reverse osmosis, and recycling it,
and proposed to the state to do that.
They were sued by the city of Newport Beach because the city of
Newport Beach said, and they knew, you know what,
the minute Riverside stops doing that, our water table is going to go down.
And it's going to go down fast enough that in a couple of years,
we're going to be out of water.
So they sued in the state of California and said that is a resource that we need.
Riverside you dumped it there for a hundred years, you can't stop dumping it
because we rely on it, and the state of California agreed with Newport beach.
They said, yes this is exactly how that aquifer gets replenished.
That's historically how it gets replenished.
Traditionally it was water flowing down from the San Gabriel Mountains that
replenished it, but since New Riverside.
Pull that water out and don't let it flow into there and
use it for your own use, you have to dump it back in there.
So, we do toilet to tap here in California.
We just call it something different.
All right.
Okay.
Let's see.
Next question.
It seems that the use of wastewater for algae growth could be very beneficial for
producers and the environment, is that right?
Yeah, I think I just sort of answered that right?
Absolutely beneficial, we should do this with all wastewater.
One of the biggest expenses for algae is buying the nitrogen and
phosphate fertilizer to feed to those algae, so if you can get that for
free from wastewater, benefit for the algae growers, okay?
If you use that waste water and pull the nitrogen and phosphate out of it,
whatever you do with that wastewater after that, whether you put it back into
an aquifer, whether you release it into the ocean, or whether you take it and
go through reverse osmosis and recycle it, it is much higher quality.
So, a win-win situation.
All right, it can be done.
It should actually, I believe,
be required of every single city in the state of California.
This is also true in Arizona,
this is also true in New Mexico, Nevada, any state where,
where water is becoming an issue we should be required to recycle it that way, right.
So is there a potential here?
There's a great potential here.
Water has becomes so expensive here in the state of California now,
it's $2400 here an acre foot San Diego.
At that price economics now will work out really well.
So we're, we already started to do this in some communities I think its
just a matter of time until it spreads to every community and this is how we do it.
The challenge is,
what do you do with the algae that you've grown in that wastewater?
Because you can't really use it for human food.
There's some debate on whether you could use it for animal food.
In general I think most, you know, the, the scientific literature sort of
says it would be perfectly safe to use that for cattle food.
The reason you don't want to use it for human food is because even though coming
out of, out of you know, secondary treatment, that water's pretty clean,
there's no bacteria and viruses in it anymore.
Wastewater tends to have a lot of funky stuff in it, right.
You know, people throw medicines down the toilet you know, so hormones get in there.
Heavy metals get in there.
You know, people just throw a lot of stuff down the sink.
And so because of that, wastewater turns out to be not nearly as clean as
river water and, you know, and certainly not, I mean rain water is very clean, but,
but, but it's not [INAUDIBLE] play into that.
So, so you tend to get a couple of those things in there and they'll build up
over time, so you kind of don't want to take that stuff and use it as human food.
Maybe if you got rid of the heavy metals.
I, I think the rest of the organics would probably be okay.
The algae would eat up,
you know, if there's a lot of, I don't know, Advil or whatever.
You know ,estrogen or what, what, whatever gets pitched down there.
The algae, the, the algae will take those organic stuffs and kind of, you know.
Break those up and, and use those for energy, but, but heavy metals,
they tend to accumulate and so you gotta be real careful with that, all right?
So, we can't use it for human food.
Great for green fertilizer, so if you take that stuff and then go put it on crops,
it's, it's loaded now with nitrogen and phosphate which the plants lead, need.
And more importantly it's actually sequestered inside the algae, so
it's slow released fertilizer.
So a couple of studies have been done on this,
where you take algae biomass and, and put it on to soils.
Absolutely fantastic remediator for soils.
You know, soils that have sort of been depleted, agricultural soils that have
been depleted over the years, because you grew plants on them for
many, many years you know, always harvesting those and, and.
Didn't allow some, some sort of green you know,
plant growth to be recycled back in there, algae helps enormously on that.
So that's, that's absolutely one market it could go to.
I think it could also go to animal feed.
You know, certainly that stuff fed to pigs or cows that, that heavy metal is
not going to end up in their muscle, and we're not going to eat it again.
So, I, I think there's some, some very valuable things that can be done with it.
I think by and large it we, we can make it safe but but
there's a few things that we have to be careful with.
Heavy metals is one that I know about you know, hormones and drugs are another.
Drugs specifically because some of those things work at such low quantities, right,
that it, I don't know, if someone throws a bottle of, you know vancomycin in there.
You know, even though that's going to be very low dose,
a few molecules of that can kind of screw things up.
And in fact many people think that you know, some of the amphibians and
fish you know, are screwed up, because of the you know,
the, the, the drugs that we pitch into there, and
some of the breakdown products of this end up having an impact on them.
Because you end up with these hormone-like molecules that, that are very bioactive.
And there's actually some good evidence on that and in some of the amphibians.
Okay we got time for just a couple more questions here.
Is there a group from UCSD looking into the possibility of using at least part of
the salt in the sea for research and/or implementation of a system?
Absolutely.
In fact, I, I, I had a very nice discussion with governor Jerry Brown's one
of his science advisors a couple weeks ago.
The biggest.
So, algae grows great out in the Salton Sea.
Earthrise is a company that grows spirulina and
sells it as a human nutriceutical.
That had been out there for 30 years.
Very profitable.
Very high levels of productivity.
So we know it is a great environment in terms of sunlight and temperature, etc.,
to grow allege.
That, that, that, that's a done deal, great flex, 'kay.
The second question then becomes, okay,
what else can allege do out of the Salton Sea?
So, we signed something you know, several years ago called the QSA,
the quantitative settlement agreement.
And, and what that is, is the Colorado River flows from Colorado,
you know, down through you know, Nevada, and then California and
then eventually into Mexico.
So, a lot of water flows through the Colorado, right?
That's most of the Rockies, all the water that comes from there flows down.
So, traditionally people have divided that, that sort of water up.
You know, agriculture along the way, and homes along the way.
A lot of the water and
more than half the water we get here in San Diego comes from the Colorado River.
And up till a couple years ago we were sort of taking most of that water,
and actually the Colorado river never quite flowed into Mexico anymore.
We actually drained the river dry before it got to Mexico.
And you know, the Mexicans didn't like that.
You know, because certainly 50 years ago and, and even 20 years ago.
Right? Before there was so
much demand on water because of population growth and
agricultural growth, water was flowing into Mexico and they were using it.
And they're like, hey, come on America, what the hell,
you guys are using up all our water.
So, big international agreement got together.
We had to settle everything.
And, and the, and the end of that.
What happen was 400,000 acre feet of water per year, by law now,
by, by, by agreement we let flow into Mexico, 400,000 acre feet.
So what's an acre feet of water?
An acre feet of water is 43,000 square feet of water, okay.
So, it's water that would cover an acre of land one foot deep.
And an acre is 43,000 square feet.
yeah, square feet.
So, 43,000 cubic feet of water.
So, 400,000 acre feet.
It's a lot of water.
We let that flow back into Mexico now.
Well, where did that water used to go?
That water used to go to agriculture in the Imperial Valley.
So they've had to cut down their agriculture a little bit.
And a lot of it use to flow into the Salton Sea.
So that now no longer flows into the Salton Sea.
That means the Salton Sea is shrinking.
As the Salton Sea shrinks, right?
Because it's less water going in evaporation continues,
it's going to get smaller and smaller.
As that happens you start to get, the beaches get bigger and bigger, bigger.
So that's called the playa, beach, Spanish for beach.
And that means the playas get bigger, and bigger, and bigger, okay?
The, these are places that are sand and
silt now dried out because the, the Salton Sea's no longer on top of them.
But what happens to those?
What happens to those is a big wind shows up, and picks up those particles and
blows 'em down wind.
Either into El Centro, which is the California city just
southeast of the Salton Sea because the wind comes from the northwest to
the southeast here every afternoon, that's sort of where the wind goes.
And then below that is Calexico.
So, between those two cities about a million people.
And, the Salton Sea has been there about 100 years.
It's not a natural body of water.
It used to be a dry lake bed.
And when we built the All-American Canal we diverted the water, you know,
to put it someplace else.
And we had a big rain, and
it kind of broke its banks, and it made the Salton Sea.
So it's a man made lake.
It, it actually came from diverting the Colorado River into it,
its full flow into it, for about three years.
Back in a time in 1919 when when we weren't using that much water.
So, a lot of water flowed there, that's where the Salton Sea came from.
But it's now, you know, birds like it.
It's, it's, it's a, you know for
a while it was a nice functional place where you could go swimming.
But what happened over a hundred years is people dumped crap into it.
Because for many years we didn't take very good care of our environment or
our waters, and so agricultural runoff went into it.
So lots of pesticides and
especially the old pesticides that don't break down so easily.
If Mexico actually has a,
a river that flows into below sea level so water actually flows toward it.
They built something called the new river and
they just dumped a bunch of crap into that thing and it flood in there.
So unfortunately Salton Sea is full of crap.
And most of that over 100 years settled to the bottom, it's covered with water.
So by and large there's some nasty things at the bottom down there,
some old pesticides, some heavy metals, some things that you don't, but
they've been covered by water.
But now as the Salton Sea shrinks and, and
that playa becomes exposed, the wind picks that up and blows that dust.
And those dust particles are covered with heavy metals, they're covered with,
with old insecticides and herbicides, and they're covered with a lot of crap.
That lands on the million people who live downwind of that, and
they get adverse health risks.
And, and in fact, someone went and did a study and came up with a number.
You know, they said this is a $8 billion liability.
That means that medical issues.
Loss to the economy.
Some agriculture will not be able to go on because you'll blow heavy metals on it.
So maybe, you know, spinach and, and salad things that you would eat fresh.
They're going to have to be processed more to get that dust off, and
so it is an expensive liability.
So one of the things we think is, hey.
Rather than just, you know, mitigate those medical liabilities from the dust blowing
down there, why don't we cover the playa with, you know, algae ponds.
And, and although we won't have fresh water flowing in from the Colorado River
anymore to fill those up, we could take municipal wastewater from Los Angeles and
truck it, you know, pipe it down.
We wouldn't truck it down.
We'd pipe it down.
Or, we can go right underground there, and there is lots and
lots of salt water sitting underneath the Salton Sea.
So we could pump that salt water out, algae grow great in salt water.
And now we would have a way to have economic activity out there, so
we're making biofuels.
That helps pay for the entire enterprise.
Why we're mitigating this environmental problem and
this medical problem that's coming as the Salton Sea recedes.
So, absolutely a big group here, you know, that are thinking about this.
You know, right now, everybody's sort of in a holding phase.
We signed the agreement a couple years ago.
It started to kick in this year.
It really gets into high gear next year 15, 16, and 17.
And, and the numbers are that by 2017,
so sort of three years from today, the sea, the Salton Sea will have receded
enough that we will start to see then the environmental consequences from that.
So we've got a couple of years before the really bad stuff shows up.
And what I'm hoping is that between the federal government and
the state government, they will take this opportunity to mitigate that
environmental you know, catastrophe that's sort of coming and very expensive one.
$8 billion is a lot of money.
It certainly won't cost us $8 billion pond's on there, and as we put on ponds on
there and make algae, either for biofuel or for, you know, for livestock feed or
whatever we use it for, there's good economics to be gained from that.
So again, I, I, I think a potential for
a win-win situation and and I hope they'll do that.
But you know, you guys have probably heard me say this many times before.
Humans only operate under two modes.
They do nothing and then they overreact.
All right?
So we're in the do nothing mode because gee,
that environmental consequences haven't shown up yet.
They're still three years away.
And my guess is in 2017 after we have our first big wind storm, and all
of that crap blows onto crops and blows onto other people's you know, houses.
And we start to worry about our health and the lawyers come out, and start suing.
You know, the people who own that part of the Salton Sea you know, and
the farmers that dump stuff into it and
the irrigation district that sold the water to, to other people.
Once those lawsuits show up, then maybe we'll do something then.
Unfortunately.
I, I, I'm hoping that the state of California's a little more savvy than that
and we actually plan ahead and get something into place, but
it'll probably be, it'll probably be the latter.
We'll do nothing for three years and then in a panic we'll try to run out there, and
put a Band-Aid on it.
But any rate, there, there's great potential and we do think about it.
Okay.
Any rate, look, there's a couple more questions here.
But we, we've run out of time today.
So either, you know,
ship them back next week if I didn't ask, answer your question.
Or if you really want to know, and you just can't wait til next week,
send me an email, and I,
I'll answer it when I have some time later, there's, later this week.
Okay. Well look, thanks again for your time.
Keep up the good work on the class, and and I will see you all next week.
And that's all we have for today.
[SOUND]
Ознакомьтесь с нашим каталогом
Присоединяйтесь бесплатно и получайте персонализированные рекомендации, обновления и предложения.
Coursera делает лучшее в мире образование доступным каждому, предлагая онлайн-курсы от ведущих университетов и организаций.
© Coursera Inc., 2018 Все права защищены.
