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Nutrient Utilization and Recycling Part 1

Course video 48 of 84

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.

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.

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Energy, Sustainable Energy, Energy Systems, Environmental Protection

教學方

Dr. Stephen Mayfield
Professor of Molecular Biology

腳本

[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.

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