How Biochar Helps Plants Grow

Biochar Update 2

💡 TLDR:

Part 1: Photosynthesis and why biochar increases plant yield.

  1. The 2 largest components of biochar is carbon (70 to 80%) and nitrogen is about (18% to 25%).

  2. Nitrogen is about 15% of RuBisCO an enzyme which cause the reaction in the Calvin cycle which is involved in photosynthesis helping plant grow. The more nitrogen you have the higher the concentration in RuBisCO.

  3. Carbon Dioxide (CO2) is required for light independent reaction (2nd part of photosynthesis). The CO2 with biochar comes from biochar distributing its carbon in the soil and interacting with water to create a useable form of CO2 that can be used by the plant.

Part 2: Choosing Region

  1. Picked Iowa (they represent about 4% of the world’s food through just corn and 99% of their corn is field corn (1 of the 6 types of corn)

  2. Interesting trend in Central Iowa where 10 out of the 12 counties had more than 2X decrease in yield compared how much arable farm land decreased.

Part 3: Testing if biochar is feasible.

  1. In the scenario where biochar can capture 4.35 tons of CO2 (when we add potassium). To make enough biochar to capture all of the world’s CO2 we would need less than 8.99% of the world’s biomass (used to make biochar) and 7.69% of the world’s farming land to hold the biochar.

Part 1: Understanding How Biochar Nutrients Help Plants

Biochar Break Down

Carbon and Nitrogen are the needle movers.

How Photosynthesis Works

(Explanation of How Carbon and Nitrogen are important to plant growth is here) — Source

High Level Definition

Photo — refers to light

synthesis — the process of building compounds from simple substances — in this case the process of making sugars for plants.

Stages of Photosynthesis

Light Dependent Reaction

Location: In the chlorophyll there is a section call chloroplast which is where the reactions for plant growth happens.

When Photosystem 2 (PSII) — named #2 because it was discovered second — Photosystem (PSI) — named #1 because it was discovered first — receive the photons from the nuclear fusion of the sun. In order to activate the PSII and PSI the energy needs to have a specific wave length of visible light.

In the example above, P680 is Chlorophyll type A variation called P680 is what donates the electron to PSII. P is pigment and 680 refers to 680 nano-meters — the wave length of light that this photosystem absorbs best. Between 625–740 nano-meters is the color is red.

Energy levels lower than those represented by red light are insufficient to raise an orbital electron to a excited (quantum) state or create enough activation for the electrons to start the process of photosynthesis.

This is why if a most regular plants die when they go too long without sunlight because they can not use their food to survive — their photosystems don’t have enough energy to activate.

How Plants Get Their Colour and Store Energy:

Chlorophylls and carotenoids are the two major classes of photosynthetic pigments found in plants and algae. Chlorophyll’s role is to absorb light for photosynthesis, while carotenoids as efficient molecules for the disposal of excess energy. When a leaf is exposed to full sun, the light-dependent reactions are required to process an enormous amount of energy; if that energy is not handled properly, it can do significant damage. Therefore, many carotenoids reside in the thylakoid membrane, absorb excess energy, and safely dissipate that energy as heat.

The excited state comes from the light energy received by the plant. The electron comes from the water. The reason this happens because Photosystem II when it does not have an electron it is noted at P680+ which is when it lack an electron. P680+ is the strongest biological oxidizing agent known in biology which means it has the ability to take away electrons. The molecule that is being oxidized is H2O. Water has 10 electrons (8 from oxygen and 2 from hydrogen). The H2O conceptually looks like this:

Background Info: The reason this bond seems to have only 8 electrons is even though oxygen has 8 electrons it only has 6 valence electrons. Valence electrons is the number of electrons that an atom has in an incomplete orbital. The first orbital has a maximum of 2 electrons and the second orbital has a maximum of 8 electrons. This means that the first 2 electrons for oxygen are in a stable orbital. The other 6 electrons of oxygen since they do not fulfil the 8 maximum of the orbital they are valence electron. With each individual hydrogen there is only 1 electrons. Which means their first orbital is not fulfilled so it would be a valence electrons. When you have valence electrons it means your atom is not stable. The goal of every atom is to have a full orbital to make it stable. When you have valence electrons the way you do that is by bonding with another atom. In the case of oxygen and hydrogen that is exactly what happens. The 6 valence electrons connect with 2 one electron hydrogen. This fulfils the 8 electrons that oxygen requires and the 2 electrons that each hydrogen needs to fulfil the first orbital.

When the H2O bonds are broken by P680+ an electron is taken which serves as the starting point of photosystem one. Once this electron is in the photosystem 2 it makes P680+ turn into a stable non oxidizing P680. As a result of the broken H2O bond you are left with 1/2 an O2 (the same as 1 oxygen) and 2H+ (which refers to 2 hydrogen with 1 less electron — which was the one lost to P680+.

Once this electron is in PSII it goes into two special chlorophyll a molecules in the reaction center that have the electron interact with the light energy. This creates the excited electron or an electron with energy which then goes into the primary electron accepter which acts as a place holder of energy. As the electron leaves the primary electron accepter. Then P680 turns into P680+ and then you get low energy electrons from the water bonds like described above.

In the image below you can see the electron transport chain from PSII to PSI. You can see the transport chain of the electron from plastoquinone (Pq) to cytochrome complex (CYT) to plastocyanine (Pc) enabling the the transfer of the electron from PSII to PSI. In the process of the electron being moved across the transport chain it also loses energy. That lost energy goes taking the H+ ions that are in the stroma (outside layer) to inside the Thylakoid lumen.

How Light dependent Reactions Work (PSI)

Again the same process happen with photosystem. The electron has low energy and it use light energy from the sun to power the process. The key difference in PSI is that is P700. Meaning that it best absorbs light at 700 nano-meters which is a shade of red. The electrons and the light energy interact when both are in the chlorophyll type a pair.

P700 is oxidized (losing electrons) and sends a high-energy electron to the ferredoxins which are proteins that mediate electron transfer to the NADP+ reductase which is the enzyme the oxidizes both the NADP+ and H+ ions — meaning that that enzyme provides both of them with an electron creating a neutral NADP and H. When you add both of them together you get NADPH

NADP+ to form NADPH. Thus, PSII captures the energy to create proton gradients to make ATP, and PSI captures the energy to reduce NADP+ into NADPH. The two photosystems work in concert, in part, to guarantee that the production of NADPH will roughly equal the production of ATP.

Creating ATP

The buildup of hydrogen ions that are moving from the stroma to the thylakoid lumen plus the ones produced by splitting water (to create the electron for PSII) accumulate in the thylakoid lumen. The ions build up energy because of diffusion and because they all have the same electrical charge, repelling each other.

To release this energy, hydrogen ions will rush through any opening, similar to water jetting through a hole in a dam. The energy released by the hydrogen ion stream allows ATP synthase to attach a third phosphate group to ADP, which forms a molecule of ATP The flow of hydrogen ions through ATP synthase is called chemiosmosis because the ions move from an area of high to an area of low concentration through a semi-permeable structure.

In the thylakoid, that opening is a passage through a specialized protein channel called the ATP synthase. The ATP synthase is a mitochondrial enzyme localized in the inner membrane which is responsible for the activation of the reaction to create ATP from ADP and phosphate.

Light Independent Reactions

After the energy from the sun is converted into chemical energy and temporarily stored in ATP and NADPH molecules, the cell has the fuel needed to build carbohydrate (sugar) molecules for long-term energy storage. The products of the light-dependent reactions, ATP and NADPH, have lifespans in the range of millionths of seconds, whereas the products of the light-independent reactions (carbohydrates and other forms of reduced carbon) can survive for hundreds of millions of years.

In plants, carbon dioxide (CO2) enters the leaves through stomata (plural of stoma) and reaches the mesophyll cells. Once in the mesophyll cells, CO2 diffuses into the stroma of the chloroplast — the site of light-independent reactions of photosynthesis. These reactions are called the Calvin cycles — named after the man who discovered it: Dr. Melvin Calvin. These reactions actually have several names associated with them.

Generally there are 3 stages of the Calvin cycle: fixation, reduction, and regeneration.

High Level of all 3 stages

In stage 1, the enzyme RuBisCO incorporates carbon dioxide into an organic molecule, 3-PGA. In stage 2, the organic molecule is reduced using electrons supplied by NADPH. In stage 3, RuBP, the molecule that starts the cycle, is regenerated so that the cycle can continue. Only one carbon dioxide molecule is incorporated at a time, so the cycle must be completed three times to produce a single three-carbon GA3P molecule, and six times to produce a six-carbon glucose molecule

Stage 1: Fixation

In the stroma, in addition to CO2, two other components are present to initiate the light-independent reactions: an enzyme called ribulose bisphosphate carboxylase (RuBisCO) which includes 5 carbon atoms, and three molecules of ribulose bisphosphate (RuBP). RuBisCO has about ≈15% nitrogen. RuBisCO catalyzes a reaction between CO2 and RuBP.

For each CO2 molecule that reacts with one RuBP, two molecules of another compound (3-PGA) form. 3-PGA has three carbons and one phosphate. Each turn of the cycle involves only one RuBP and one carbon dioxide and forms two molecules of 3-PGA. The number of carbon atoms remains the same, as the atoms move to form new bonds during the reactions (3 atoms from 3CO2 + 15 atoms from 3RuBP = 18 atoms in 3 atoms of 3-PGA). This process is called carbon fixation, because CO2 is “fixed” from an inorganic form into organic molecules. When carbon is fixated it turned into a form that can be used by plants.

How CO2 helps the plant — carbon fixation same as nitrogen fixation — making it useable.

Stage 2: Reduction

ATP and NADPH are used to convert the six molecules of 3-PGA into six molecules of a chemical called glyceraldehyde 3-phosphate (G3P). That is a reduction reaction because it involves the gain of electrons by 3-PGA. Recall that a reduction is the gain of an electron by an atom or molecule. Six molecules of both ATP and NADPH are used. For ATP, energy is released with the loss of the terminal phosphate atom, converting it into ADP; for NADPH, both energy and a hydrogen atom are lost, converting it into NADP+. Both of these molecules return to the nearby light-dependent reactions to be reused and reenergized.

Stage 3: Regeneration.

Interestingly, at this point, only one of the G3P molecules leaves the Calvin cycle and is sent to the cytoplasm to contribute to the formation of other compounds needed by the plant. Because the G3P exported from the chloroplast has three carbon atoms, it takes three “turns” of the Calvin cycle to fix enough net carbon to export one G3P. But each turn makes two G3Ps, thus three turns make six G3Ps. One is exported while the remaining five G3P molecules remain in the cycle and are used to regenerate RuBP (since it requires 5 carbon atoms), which enables the system to prepare for more CO2 to be fixed. Three more molecules of ATP are used in these regeneration reactions.

How Nitrogen is Fixated in Corn

The reason why this is important to understand is to see how the nitrogen in biochar can turn into a beneficial nutrient for plant growth.

How Does Nitrogen Fertilizer for Plants?

Commercial fertilizer can contain a variety of different chemical forms of nitrogen, including ammonium (NH4), nitrite (NO2), nitrate (NO3), and urea (CH4N2O), but plants can directly use nitrate (NO3) and ammonium (NH4).

How Does This Work For Corn?

Corn specifically use ammonium (NH4) more efficiently when comparing to Nitrate (NH3). When taken up by roots , the ammonium form (NH4) is directly converted into amino acids.

While Nitrates (NO3) must be transported to the leaves before being transformed into amino acids. More steps = less efficient.

How is Nitrogen Helpful to Plants

As mentioned in the photosynthesis section, nitrogen represent about 15% of RuBisCO which is an enzyme that is responsible for the starting of light independent reactions (part 2 of photosynthesis process).

In the N2 it is nitrogen triple bonded to another nitrogen

Add picture of N (triple bond) N.

Nitrogen Fixation: The Process of Turning N2 into Useable Ions for Plants.

Nitrogen Fixation: Where atmospheric nitrogen to ammonia (NH3), Nitrite (NO2), Nitrate (NO3).

Types of Nitrogen Fixation:

There is atmospheric, industrial, and biological. The one that is relevant is biological since biochar is in the soil.

Biological nitrogen Fixation At a high level

Nitrogen (N2) enter the soil (from the atmosphere or fertilizer). Then diazotrophs — organisms capable of assimilating atmospheric nitrogen — create can create ammonium (which can be used by corn).

The enzyme (which is a protein catalyst — meaning they speed up reactions) in the process of biological nitrogen fixation is called Nitrogenase also known as Mo-Fe

Process of Nitrogenase

Step 1: Since the enzyme is a diazotroph they live in habitats low in oxygen, such as soils and decaying vegetable matter. When the N2 gets into the soil it binds with the nitrogenase (the enzyme).

Step 2: Then the mixture goes through a process called reduction which means that they are gaining electrons. This comes from the 2H+. The 2H comes from water molecules within the soil.

Step 3: Continue repeating step 2 until you have an ion that is useable for plants like ammonia (NH3) or ammonium (NH4).

Once the the ammonia is released the nitrogenase breaks off from the released products and is now available to bind to the next N2 molecule.

Part 2: Choosing a region and plant species to focus on

19.5% of the world’s calories comes from Maize (corn). The highest producer is the U.S, they produce 36.3% of the world’s maize. 578.6M tons of are produced in Iowa (54.5% of US total). Basically almost 4% of the world’s calories come from Iowa.

99% of Iowa’s corn is field corn (1 of the 6 types of corn). I picked specifically counties in central Iowa. In the image below you can see the yield of corn of Iowa in 2020. A bushel = 56 pounds of product harvested

Red Highlights Central Iowa.

The reason I chose central Iowa because

Boone — 0.006% decrease in land — 14% decrease in yield

Dallas — 3% increase in land — 3.7% decrease in yield

Grundy — 1.8% decrease in land — 7% decrease in yield

Hamilton — 2.5% increase in land — 1.2% increase in yield

Hardlin — 0.7% land decrease — 8% yield decrease

Jasper and Marshall — info was not disclosed

Polk — 3% land decrease — 9% yield decrease

Poweshiek — 3% land decrease — 7% yield decrease

Story — 1.7% land decrease — 10% yield decrease

Tama — 0.2% land decrease — 17% yield decrease

Webster — 2.1% land increase — 1.4% yield increase.

Apart from Hamilton and Webster. There has been a decrease of yield minimum 2 times more than area of land planted.

Part 3: How Feasible is Biochar to Mass Scale?

Below is a description of how much biochar it takes to get to net zero CO2 emissions, what percentage of the world’s biomass (which is used to make biochar), and how much land is need for all of the biochar.