Where Do All Those Leaves Come From?!



I wanted to link my leaf raking drudgery to some scene

in a famous movie. No go. Raking leaves is so mundane

that I could only find one movie that showed someone

raking leaves – Disney’s The Odd Life of Timothy Green.

And heck, he sprang up from a garden, all those leaves

are his cousins!

It’s Fall if you hadn’t noticed. Apple cider, football, pumpkin, wonderful colors….. and raking leaves. I spent last weekend with a rake in my hand and hate in my heart.

Maybe that’s a little strong. But when you spend time trying to put the little beggars in piles and then have to watch the wind scatter them and blow more leaves off the trees – well, you know it’s exasperating.

My efforts resulted in seven 50 gallon bags stuffed with botanical death. All told, more than 400 pounds of biomass. I stare up at the bare branches and wonder, “where did all that matter come from?”

Matter is made of atoms, so the leaves in the trash bags represent literally trillions upon trillions of atoms joined together in specific molecules. So the question is really, what was the source(s) of those particular atoms?

The tree made the leaves, but it didn’t get smaller due to its effort to produce leaves, so the material in leaves didn’t come from the mass of the tree. They were certainly organized by the tree into those biomolecules (proteins, carbohydrates, DNA and RNA, and fats) that make up the leaves, but they didn’t come from the tree originally.

The tree has roots in the soil and pulls water and nutrients into its trunk via those roots. Could the soil be where all the mass comes from? Consider this. If you have a potted plant, do you have to add soil to it every year? Nope.

Jan Baptiste van Helmont was a successful scientist, even

though it may not look like it at first. He was wrong about

digestion’s stages, but did include a description of

something that sounds a lot like the enzymes we have.

He said that trees didn’t get there mass from the soil, but

said they did get it from water – wrong. However, he said

air was involved and proposed that air was made of gas –

a word he coined.

Six hundred years ago, a scientist named Jan Baptist von Helmont measured this more carefully. He grew a tree in 200 pounds of soil from a seed until it weighed 190 pounds. Then he weighed the soil again. He found all his original dirt except for 2 ounces. I very much doubt that 190 pounds of tree mass came from two ounces of soil.

Everyone knows that trees need water. During a drought, your trees die and your grass turns brown. If water is that crucial, maybe my 400 hundred pounds of dead leaves came from water.

Water is made up of hydrogen and oxygen (H₂O).  Can all the leaves be made from just water? No way; trees (and every other living thing on Earth) are carbon based. The proteins sugars, lipids, and nucleic acids are all built on a backbone of carbon atoms, with oxygen, hydrogen, and nitrogen atoms in some specific spots.

Carbon, hydrogen, oxygen, and nitrogen are the main elements of life. You can’t change one atom into another (with the exception of radioactive elements) so all the mass in my bags of leaves couldn’t have come from just water. Certainly some of the mass came from water, after all, living things are mostly water, but there’s no way the carbon came from water.

When a tree uses sugars to make energy, some water is produced. This is called metabolic water, and we do it too. You can prove this by breathing on a mirror. See that condensation? Much of that is metabolic water. Metabolic water is important in producing the molecules of life, so important that some animals, like the kangaroo rat, can live only on metabolic water, they never drink!

Kangaroo rats can live their lives without drinking even

though they live in Death Valley. Another fun fact – they

have fur-lined cheek pouches for carrying seeds back to

their den. No drinking and fur in their oral cavity – worst

case of dry mouth ever!

So a bit comes from water, even less from soil, and none of the leaf mass springs from the tree itself. What do we have left? Only one choice comes to my mind - and your breathing it right now. 

Air? Really? How could 400 hundred pounds of leaves come from the air? It seems silly, but it’s the basis of life on Earth. Air is 78% nitrogen (N₂), 21% oxygen (O₂), and 0.00397% carbon dioxide (CO₂) – plus some water vapor. This is almost everything a growing tree needs, except for some trace minerals that can be found in that 2 ounces of disappeared soil that von Helmont measured 600 years ago. 

Basically, those things we humans breathe out (CO₂, H₂O, O₂, and N₂) are exactly what plants need to grow. We actually use only a small portion of the oxygen that we breathe in, but we do add some carbon dioxide to the air when we exhale. This is a big reason why talking to your plants makes them grow better; you're increasing the concentration of carbon dioxide in their immediate vicinity.

Plants take carbon dioxide from the air, and using the energy of sunlight, turn it into carbohydrates – this is photosynthesis. But they don’t just use the carbs for energy. The sugars are the carbon basis for synthesizing every biomolecule the plant will need in order to build leaves and wood.

We have covered carbon (from CO₂), hydrogen (from rain and metabolic water), oxygen (from carbon dioxide and metabolic water), but what about the nitrogen in DNA and proteins? Believe it or not, that comes from the air too.

N₂ in the air is hard to tear apart so the nitrogen can be used in building biomolecules. Plants can “fix” carbon themselves, turning gaseous carbon to solid carbon during photosynthesis, but they can’t fix nitrogen. To turn nitrogen into a form they can use, plants rely on nitrogen fixing bacteria in the soil.

Many plants form a symbiotic relationship with nitrogen fixing bacteria, letting them live inside nodules of their roots. Therefore, the nitrogen the trees use comes from the air, even if it passes through the bacteria first.

The top image is from art student Melchiorri. He claims

that the silk mesh stabilizes the chloroplasts and lets them

produce oxygen via photosynthesis even though they aren’t

in a cell. There are problems here, like chloroplasts don’t live

very long. The bottom image is of an artificial leaf that can

produce hydrogen and oxygen gases from water in the

presence of light. Leaves use 1% of available light; this “leaf”

already uses 7x as much of the light.

Most trees don’t harbor nitrogen-fixing bacteria in their roots, they rely on the nitrogen that the bacteria spread around and leave in the soil, or that nitrogen that comes from dead plant material. One exception is the black locust tree. It is estimated that a black locust stand of trees (and their bacteria) can add 40-60 kg (88 –133 lb.s) of nitrogen to the soil every year.

Now I can rake my leaves confident in the knowledge that I'm raking up a true miracle. They can’t weigh too much, they’re basically nothing but air, water vapor and a bit of bacterial waste. So why does my back hurt so much?

Soon, we may have artificial leaves to deal with. One recent project by art school graduate Julian Melchiorri has used chloroplasts embedded in silk protein mesh in order to carry out photosynthesis. These can be used in space, where plants have a harder time growing in zero gravity. This might be our source of oxygen on the way to Mars.

In addition, new research describes a synthetic leaf made form metal films on either side of a silicon mesh can be used to split water as occurs in photosynthesis. These synthetic leaves might be helpful in producing hydrogen and oxygen for use in fuel cells. I just hope we don’t have to rake them up.



Contributed by Mark E. Lasbury, MS, MSEd, PhD
As Many Exceptions As Rules

Pijpers, J., Winkler, M., Surendranath, Y., Buonassisi, T., & Nocera, D. (2011). Light-induced water oxidation at silicon electrodes functionalized with a cobalt oxygen-evolving catalyst Proceedings of the National Academy of Sciences, 108 (25), 10056-10061 DOI: 10.1073/pnas.1106545108

The Electrical Grid Needs Fattening Up

Heimlich was the caterpillar from one of my kids’

favorite movies, A Bug’s Life. He ate and ate because

he needed to store energy. When the time came to

metamorphose into a butterfly, he would need to

convert that stored energy to forms his body could

use. We need the same thing for our national

energy grid.

When presented with food, you can convert it all to energy (stuff your face), or can save some for later (leftovers). We can make use of much food over time and not lose any of its energy, most of the food won't spoil before tomorrow or the next day. Likewise, your body can store energy it takes in, some as glycogen, and some as fat. We can go back later to burn the fat when we need extra energy – although we usually don’t.

This isn’t the case with the national energy grid. Whatever energy is generated, it goes directly into the copper wires of the transmission network. This is fine most of the time, because you can run more or fewer generators, and they can be made to work at higher or lower efficiency to meet immediate needs.

The real problem comes when we try to be green. Some fuel for generators can be used when needed, but other sources of energy have to be used when they are available. For example, it doesn’t matter whether you burn coal today or ten years from now, you still get the energy from it.

But think about wind power. If you don’t generate electricity from the wind as it blows, then you can’t go back later and use it – it’s gone with the wind. Same with solar energy, if you don’t harvest today’s sunshine, you can’t come back tomorrow and find it. Sure, you can use tomorrow’s sunshine, as long as it’s sunny – but not everyday is sunny.

As more and more electricity is generated from green sources, we need to harvest as much of it as we can when we can. This means that we need to be able to store energy in some form. This large-scale energy storage is the focus of much current research and even more construction.

If we can’t store electricity as electricity, it means we have to convert (transduce) it to some form of potential energy. Research and engineering is showing that we can do this in several ways. Let’s look at a few:

Compressed air storage – One source of potential energy is air under pressure. Of course, it would have to be a whole bunch of air, like an abandoned mine volume of air - or one speech from a politician. Several of these large-scale energy storage mechanisms have been set up in Europe, using mines or caverns.

Here is a schematic for compressed air storage of

energy. The compressor motor uses energy from the

grid to pump air into a huge space – maybe somewhere

that has given up its natural gas. Then when it escapes,

it runs turbines that return electricity to the grid. I bet

fracking opponents might have a problem with this as

well – geologically speaking.

Some caverns are better than others. Salt caverns (McIntosh, Alabama) are good because the crystal is flexible without being porous; no reaction occurs between the walls and the oxygen. When there's less demand on the grid, air compressors use the extra electricity to pump air into a sealed mine. Newer proposals seek to use pipelines to store the compressed air.

Under pressure, the air can remain as a source potential energy for an undetermined time. When the grid needs more electricity, the pressurized air is allowed to escape, passing across turbine blades and turning a generator. Basically, it’s electricity to wind to electricity.

Compressed air storage is about 45% efficient. If you use the heat created by compressing the air (pushing the molecules together creates friction and heat) to heat the air when it expands (usually it cools greatly, like when you spray off your computer keyboard with that can of air and the long red straw), you can increase the efficiency to about 70%. That ain’t bad.

Hydrogen – Hydrogen gas is a very dense fuel source, meaning that you get a lot of energy for the amount of fuel you use. However, you first have to produce the hydrogen. One way is to split water, just like plants do during photosynthesis. While plants use the power of the sun to split water, we can use electricity – this is called power to gas generation. Gas generated is usually hydrogen from water, but methane can also be produced from carbon dioxide plus water.

The hydrogen gas produced is then stored, similar to the compressed air storage described above. For more efficiency in storage, the hydrogen can be cooled and pressurized to be stored as a liquid. When electricity needs to be generated, the gas can be burned to heat water for conventional turbine generators, or it could be put through large fuel cells, as we discussed two weeks ago.

Caverns and mines can be utilized for storage, but Germany uses mostly hydrogen pipelines for storage, and has done so for many years. In fact, German hydrogen storage is some 5000x greater then their pumped water storage capability. I’d worry about explosions. Remember the Hindenburg - that was hydrogen gas.

This is how pumped water storage works. They

picture shows the direction for daytime and nighttime,

but it could be anytime energy is excess or needed. The

reason for day and night labels is that you can make it

in the day when more is needed and store it at night,

when energy usage is lower. In addition, using electricity

at night is cheaper (less demand = less cost).

Pumped Water - A new pumped water storage facility is near the approval stage in Montana. The Gordon Butte project will build a pair of 1.3 billion gallon (6.4 billion liter) reservoirs, one atop the butte and one 1025 ft (312 m) below, at the bottom of the butte. The U.S. and China have many of these facilities, the largest of which is located on the Virginia, West Virginia border (Bath County, 3 GW).

When there is excess energy in the grid, it will automatically be used to power pumps that will move water from the lower reservoir to the upper. This mass of water, positioned in the top reservoir is a powerful source of potential energy.

During peak usage hours, the water is allowed to fall to the lower reservoir, through a turbine that then powers a generator. At this point, the system acts exactly like a typical hydroelectric plant. These mechanisms are very efficient, returning 75-85% of the energy invested in them. The problems: you need sufficient space at two nearby locations, but at very different elevations, and two, reservoirs are very expensive to dig. I wonder if drought would be a problem.

The real advantage to pumped water storage over other large-scale storage methods is the timing. Pumping or generating can begin within just 5-7 minutes of declared need, while compressed air storage facilities take more than 30 minutes to ramp up.

Electric vehicles will need be chargeable wherever they

are if we are to make them a source of energy storage

for the grid. Here is the new thing – wireless rechargers.

The top image shows them implanted in parking spots,

while the lower images has them embedded in the

parking blocks. Yes those concrete obstructions in

parking lots are called parking stops or parking

blocks – bet you didn’t know that.

Electric Cars – One intriguing idea is to use privately and publicly owned electric vehicles as a storage dump for energy. The batteries of such cars can be connected to the grid in a two-way fashion. You plug them in at night to recharge the battery, but a V2H (vehicle to home) system also allows you to draw energy from the car battery in case your house power lines are down.

A study from 2011 used mathematics (eww!) to estimate the viability of electric vehicles as a large scale energy storage mechanism. In general, two things will have to happen. One, 10 million or more people (in U.S.) need to own these cars. And two, they have to be able to plug in their cars at work. Only with work and home charging will enough cars be plugged in at any one time so that a grid need will be met, either by pumping more energy into the car batteries or taking a bit of energy from each car.

There are several other methods – large, rechargeable batteries are starting to be used. Painesville, OH has a 1 MW vanadium battery in use, as well as large flywheels, or thermal storage. You can investigate these yourself and figure out how best to make green energy pay off in the long run..

Contributed by Mark E. Lasbury, MS, MSEd, PhD

As Many Exceptions As Rules

F. K. Tuffner, Member, IEEE, and M. Kintner-Meyer, Member, IEEE (2011). Using Electric Vehicles to Mitigate Imbalance Requirements Associated with an Increased Penetration of Wind Generation Power and Energy Society General Meeting, 2011 IEEE , 1-8

Where Do All Those Leaves Come From?!

I wanted to link my leaf raking drudgery to some scene

in a famous movie. No go. Raking leaves is so mundane

that I could only find one movie that showed someone

raking leaves – Disney’s The Odd Life of Timothy Green.

And heck, he sprang up from a garden, all those leaves

are his cousins!

It’s Fall if you hadn’t noticed. Apple cider, football, pumpkin, wonderful colors….. and raking leaves. I spent last weekend with a rake in my hand and hate in my heart.

Maybe that’s a little strong. But when you spend time trying to put the little beggars in piles and then have to watch the wind scatter them and blow more leaves off the trees – well, you know it’s exasperating.

My efforts resulted in seven 50 gallon bags stuffed with botanical death. All told, more than 400 pounds of biomass. I stare up at the bare branches and wonder, “where did all that matter come from?”

Matter is made of atoms, so the leaves in the trash bags represent literally trillions upon trillions of atoms joined together in specific molecules. So the question is really, what was the source(s) of those particular atoms?

The tree made the leaves, but it didn’t get smaller due to its effort to produce leaves, so the material in leaves didn’t come from the mass of the tree. They were certainly organized by the tree into those biomolecules (proteins, carbohydrates, DNA and RNA, and fats) that make up the leaves, but they didn’t come from the tree originally.

The tree has roots in the soil and pulls water and nutrients into its trunk via those roots. Could the soil be where all the mass comes from? Consider this. If you have a potted plant, do you have to add soil to it every year? Nope.

Jan Baptiste van Helmont was a successful scientist, even

though it may not look like it at first. He was wrong about

digestion’s stages, but did include a description of

something that sounds a lot like the enzymes we have.

He said that trees didn’t get there mass from the soil, but

said they did get it from water – wrong. However, he said

air was involved and proposed that air was made of gas –

a word he coined.

Six hundred years ago, a scientist named Jan Baptist von Helmont measured this more carefully. He grew a tree in 200 pounds of soil from a seed until it weighed 190 pounds. Then he weighed the soil again. He found all his original dirt except for 2 ounces. I very much doubt that 190 pounds of tree mass came from two ounces of soil.

Everyone knows that trees need water. During a drought, your trees die and your grass turns brown. If water is that crucial, maybe my 400 hundred pounds of dead leaves came from water.

Water is made up of hydrogen and oxygen (H₂O).  Can all the leaves be made from just water? No way; trees (and every other living thing on Earth) are carbon based. The proteins sugars, lipids, and nucleic acids are all built on a backbone of carbon atoms, with oxygen, hydrogen, and nitrogen atoms in some specific spots.

Carbon, hydrogen, oxygen, and nitrogen are the main elements of life. You can’t change one atom into another (with the exception of radioactive elements) so all the mass in my bags of leaves couldn’t have come from just water. Certainly some of the mass came from water, after all, living things are mostly water, but there’s no way the carbon came from water.

When a tree uses sugars to make energy, some water is produced. This is called metabolic water, and we do it too. You can prove this by breathing on a mirror. See that condensation? Much of that is metabolic water. Metabolic water is important in producing the molecules of life, so important that some animals, like the kangaroo rat, can live only on metabolic water, they never drink!

Kangaroo rats can live their lives without drinking even

though they live in Death Valley. Another fun fact – they

have fur-lined cheek pouches for carrying seeds back to

their den. No drinking and fur in their oral cavity – worst

case of dry mouth ever!

So a bit comes from water, even less from soil, and none of the leaf mass springs from the tree itself. What do we have left? Only one choice comes to my mind - and your breathing it right now. 

Air? Really? How could 400 hundred pounds of leaves come from the air? It seems silly, but it’s the basis of life on Earth. Air is 78% nitrogen (N₂), 21% oxygen (O₂), and 0.00397% carbon dioxide (CO₂) – plus some water vapor. This is almost everything a growing tree needs, except for some trace minerals that can be found in that 2 ounces of disappeared soil that von Helmont measured 600 years ago. 

Basically, those things we humans breathe out (CO₂, H₂O, O₂, and N₂) are exactly what plants need to grow. We actually use only a small portion of the oxygen that we breathe in, but we do add some carbon dioxide to the air when we exhale. This is a big reason why talking to your plants makes them grow better; you're increasing the concentration of carbon dioxide in their immediate vicinity.

Plants take carbon dioxide from the air, and using the energy of sunlight, turn it into carbohydrates – this is photosynthesis. But they don’t just use the carbs for energy. The sugars are the carbon basis for synthesizing every biomolecule the plant will need in order to build leaves and wood.

We have covered carbon (from CO₂), hydrogen (from rain and metabolic water), oxygen (from carbon dioxide and metabolic water), but what about the nitrogen in DNA and proteins? Believe it or not, that comes from the air too.

N₂ in the air is hard to tear apart so the nitrogen can be used in building biomolecules. Plants can “fix” carbon themselves, turning gaseous carbon to solid carbon during photosynthesis, but they can’t fix nitrogen. To turn nitrogen into a form they can use, plants rely on nitrogen fixing bacteria in the soil.

Many plants form a symbiotic relationship with nitrogen fixing bacteria, letting them live inside nodules of their roots. Therefore, the nitrogen the trees use comes from the air, even if it passes through the bacteria first.

The top image is from art student Melchiorri. He claims

that the silk mesh stabilizes the chloroplasts and lets them

produce oxygen via photosynthesis even though they aren’t

in a cell. There are problems here, like chloroplasts don’t live

very long. The bottom image is of an artificial leaf that can

produce hydrogen and oxygen gases from water in the

presence of light. Leaves use 1% of available light; this “leaf”

already uses 7x as much of the light.

Most trees don’t harbor nitrogen-fixing bacteria in their roots, they rely on the nitrogen that the bacteria spread around and leave in the soil, or that nitrogen that comes from dead plant material. One exception is the black locust tree. It is estimated that a black locust stand of trees (and their bacteria) can add 40-60 kg (88 –133 lb.s) of nitrogen to the soil every year.

Now I can rake my leaves confident in the knowledge that I'm raking up a true miracle. They can’t weigh too much, they’re basically nothing but air, water vapor and a bit of bacterial waste. So why does my back hurt so much?

Soon, we may have artificial leaves to deal with. One recent project by art school graduate Julian Melchiorri has used chloroplasts embedded in silk protein mesh in order to carry out photosynthesis. These can be used in space, where plants have a harder time growing in zero gravity. This might be our source of oxygen on the way to Mars.

In addition, new research describes a synthetic leaf made form metal films on either side of a silicon mesh can be used to split water as occurs in photosynthesis. These synthetic leaves might be helpful in producing hydrogen and oxygen for use in fuel cells. I just hope we don’t have to rake them up.


Contributed by Mark E. Lasbury, MS, MSEd, PhD
As Many Exceptions As Rules



Pijpers, J., Winkler, M., Surendranath, Y., Buonassisi, T., & Nocera, D. (2011). Light-induced water oxidation at silicon electrodes functionalized with a cobalt oxygen-evolving catalyst Proceedings of the National Academy of Sciences, 108 (25), 10056-10061 DOI: 10.1073/pnas.1106545108