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.
Nutrient Utilization and Recycling Part 1
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來自 University of California San Diego 的課程
人类能源的未来
428 個評分
從本節課中
Biofuel Production and Downstream Processing
Covers the chemistry of biodiesel, looks at the different thermochemical processes used to convert biomass to fuel, and examines renewable biogas. It also looks at the production process of algae biofuel, how and why nutrient utilization and recycling is important in biofuel production, and the relationship between biofuel and water.
與講師見面
Dr. Stephen MayfieldProfessor of Molecular Biology
University of California San Diego
[MUSIC]
My name is Brian Palenik, I'm a professor marine biology
at Scripps Institution of Oceanography at the University of California San Diego.
I'm going to talk to you today about nutrient utilization and recycling.
Especially how it relates to bio fuel production.
So if we're going to grow any kind of crop for
for bio fuels we need to provide nutrients to that crop.
Basically plants will take nutrients out of the soil and
what we've learned though is with time they deplete those nutrients
and so to get really high bio mass yields we
need to provide those nutrients back in the form of fertilizer.
Se we'll add fertilizer to these, to the soil to get robust crop production.
The most important plant nutrients are nitrogen, potassium, phosphorous.
So those are the ones we've learned to provide to our crops.
So this is kind of an example data of that,
here we see crop yield, so here we have an unfertilized
corn crop and you can see as we add more
and more nutrients to that crop, we get increased carbohydrate production.
And with time or, or with the
addition of nutrients that saturates, and that's because
the plants either don't need anymore nutrients or
they've run out of something else like phosphorus.
Since in this case we are fertilizing with nitrogen.
Now an important idea is that different kinds of crops
are going to needs different amounts of nutrients and different ratios.
And you can kind of see this best here, here we have corn and soybeans.
So for example if we fertilize those, it turns out
we need to provide less nitrogen to soybean as a crop.
Partly because they have nitrogen fixing bacteria that
help them get additional nitrogen out of air.
So this is an important concept we need to consider, that as we grow
different crops for bio mass, they're going to
need different types and ratios of nutrients.
And I'll kind of talk about that in a second.
So even though fertilizers have been this tremendous benefit
to us we they've come with some really difficult problems.
First off to produce fertilizers you need energy to make those fertilizers.
And then fertilizer production produces green house gases,
and so we're while we producing fertilizers we're
con contributing to our problems with CO2 production
in the atmosphere and the consequences of that.
So we produce a couple of of important processes to produce fertilizers.
We produce ammonia.
Plus floric acid and nitric acid those are kind of the major
ones that we're producing and they're contributing to green house gas forming.
Probably the most important process is called the Haber- Bosch process.
This was invented a number of years
ago, and has really revolutionized fertilizer production.
Because we're able to take nitrogen gas out of the
air and using hydrogen we're able to make liquid ammonia.
Then we can process that ammonia and then apply it to fields,
and that dramatically increased crop production
on the, on the plant essentially.
So I mentioned phosphorus, phosphorus is a really important resource,
but as we think about the future of sustainable energy production.
Phosphorus is going to be a limiting resource.
It's been estimated that we have about a 50 to
100 year supply of phosphorous, in the form of phospherite.
That's the form that we mine it from, from the ground.
So while that doesn't seem like a problem right now, as we plan our
future, we really want to think about phosphorus
and how to use it more efficiently.
Another problem with fertilization is that we've created water quality problems.
So we use this, concept, eutrophication, and that's where we, we've ac, added
nutrients, in terms of fertilizers, and now
as nutrients flow into the water supply,
and they create algo blooms some of those algo actually algae actually have
toxins, and so it really affects our drinking water supply in a negative way.
And also causes smelling drink smelly drinking water and things like that.
So we have this problem of utrification that's really
arisen by because of our use of of fertilizers.
So I've just illustrated those here.
One of the major sources is going to be run off from fertilization of crops.
And then, also, run off, for example,
from, from mining, minerals to use as fertilizers.
So those are two major sources, of fertilizers,
that are used, that cause the problem of eutrophication.
No, eutrophication has caused some problems to our oceans as well.
So, what we see here, a lot of the crop
production, for example in the United States, occurs in this
middle part of the country, but that's also part of
this water shed that we call the Mississippi River basin.
So the fertilizers will run off the soil in some cases, end up in
the Mississippi River, and then all those
nutrients flow out into the Gulf of Mexico.
The problem with that is, you then have this body
of fresh water at the surface with high nutrients, it causes
and algae bloom, and then those algae essentially start to die
and they fall into the bottom of of the water column.
Bacteria eat them and as this bacteria do that they use up all the oxygen.
So what happens is you get what we call dead zones.
And those are regions where there's so little oxygen
that, that other organisms, like fish or crabs, just can't
survive anymore, so we've essentially caused, this, this death
in the, in the bottom part of the water column.
And it's a really severe problem, off, off the Louisiana coast.
Last problem with fertilizers is that they do have some direct human health problems.
So remember we said we use nitrate as a
fertilizer and so nitrate gets into the water supply.
And nitrate itself isn't particularly toxic but it gets reduced to nitrite.
And nitrate can be a problem it gets it binds to proteins
in blood and particularly young children and babies are very sensitive to nitrites.
So we have EPA standards for for nitrites in water because of that.
So moving forward, what we're trying to do then is
develop a bio energy future based on using bio mass.
And a number of people have put forward some recommendations and goals for how to
increase bio mass production so that we can get bio energy from the bio mass.
So for example the one goal is by 2030 to
supply 5% of the nation's power for example, using bio mass.
Or 20% of the transportation fuels.
Now to produce this much bio mass
is going to require as we kind of talked about
it's going to need fertilizers to, to grown
that plant material to then convert into energy.
And so under various scenarios we'll need to supply fertilizer
just to get increased crop production to meet those energy needs.
[SOUND]
And this is kind of an example of that scenario.
Where, if we start to ramp up our production of crop material for biofuels.
Some estimates are that we'll need something like
five times more, fertilization to actually achieve that.
And that's a tremendous amount of fertilizer.
So the question is, how can we try to reduce
our fertilizer use or recycle fertilizers, recycle those nutrients more efficiently?
And what I'm going to point out is a couple of strategies to do that.
One is to use plants that have very high yield under low fertilization.
So as I mentioned in the beginning, some crops really just
need a lower fertilizer levels to achieve similar bio mass yields.
So some of these are are miscanthus and switch grass so these are grasses.
And grasses tend to grow extremely well on low fertilizers.
Then we have a trees would be another possibility, and then algae ponds,
which are, algae are very efficient at utilizing nutrients and grow very rapidly.
So again, one strategy would be to, as we develop these
biomass stocks, we use certain kinds of plants to do that.
Another strategy is to use nitrogen fixing bacteria more efficiently.
So
bacteria, some bacteria able to fix nitrogen out of
the air and they provide ammonia to the plant.
And some plants have developed a symbiosis with these bacteria.
So one strategy is to try to use more of these bacterial plants symbiosises.
Or actually engineer plants so that they can develop these symbioses.
And, another example, I know Susan Golden talked about cyanobacteria.
So some cyanobacteria have this, ability to also take nitrogen out
of the air to fix ammonia to use that for growth.
And so if we were to use certain nitrogen fixing cyanobacteria to produce biofuels.
We would really reduce our need to put nitrogen into the system.
So, another strategy, again, related to algal biofuels, is really develop algal
biofuel systems from the ground up, that take advantage of, of nutrient recycling.
So this is an example of that we could grow algae in a pond.
Harvest the algae, and then use this process called hydro thermo liquefaction.
And that will generate a green crude which we can use for bio
fuel, and then we can use this waste water to regrow the algae.
So the idea is that we can develop kind of a, a closed system or
a relatively closed system where we, we don't
have to continually be putting in, nutrient supplies.
The challenge will be to find algae that grow, grow well in this, this
kind of environment, and that's because this
wastewater is actually toxic to lots of algae.
So we have to find particular strains that are going to be
really good at growing in this kind of closed, loop system.
Another strategy which is really a huge area, and I just sort of outlined it in
this diagram is, we need to be more
efficient in u, recycling nutrients in, in agricultural systems.
So there are many, crops and, crop waste
that we could really be recycling much more efficiently.
[BLANK_AUDIO]
So the last example that we could think about is
really a much better use of waste water, to produce, algobiofuels.
So remember, we talked about utrefecation.
And right now, water from wastewater treatment, and from,
for example, manure run off, goes into our water supply.
So, typically, this is what we do now.
We take raw sewage, and we clarify it.
We put it through some aerobic and anaerobic digestion systems.
And then we essentially put the wastewater back in to, to rivers or lakes.
it, but it's actually often full of nutrients.
So instead, what we could learn to do, is to
try to put those nutrients, for example here, right into algae
photo bioreactors, and then grow a supply of algae that
we could then use for, for biomass or for liquid fuels.
So these systems could be very simple, or very technologically sophisticated.
For example we could put the waste water into simple
pond systems that would grow up the algae that way.
But people are trying to come up with
very ingenious ways of doing these sorts of things.
For example, there's something called the algae wheel.
Where we have a cycling wheel system and the algae and bacteria grow
on that system, increasing the yield of the algae, while treating the waste water.
And NASA for example, has even come up with some interesting ideas where we use
large plastic enclosures, and we put waste water directly into those plastic systems.
And the algae grow up contained in that using the nutrients that
are in the waste water and then we can harvest those algae.
In this way we wouldn't be putting this,
this waste water right into the oceans, we'd
actually be getting some benefit out of those
nutrients that are still in the waste water.
[BLANK_AUDIO].
So what I've tried to do today is to convince you that
biomass production for, for biofuels is going to require a lot of nutrients.
And particularly,nitrogen and phosphorus are going to be the most important ones.
And what we need to do is figure out how to reduce those
nutrient requirements by, by using particular plants
or recycling nutrients in, in clever ways.
So that we can really develop a sustainable energy future.
So thank you for listening.
