"We speculate that the <i>B. bigelowii</i> endosymbiont may represent an early stage of endosymbiosis before it is fully established as an organelle, and it disappears under ammonia-rich conditions, in contrast to UCYN-A1." <spanclass="cite">CITE</span>, which is why we used the fixation rate for UCYN-A2, which is 151.1±112.7 fmol/(cell·day) of nitrogen. Let's suppose that each cell contains one and only one nitroplast (this is, an UCYN-A2). The number of cells in a crop plant can vary from the kind of crop and other multiple factors, but it is a number between a billion up to a trillion cells. Let's say that the average plant has 50 billion cells, as an approximation, depending on the specific variety of crop and its growth conditions. Using this value, we get that our genetically modified plant would fix 0.1511 mmol per day. If we take into consideration diatomic nitrogen's molar mass, 28.02 g/mol, our plant would fix 211.65 mg/day. Plants need less than 100 mg per day to survive, so our plants would be completely self-sufficient.
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<pre>
<p>
$$
\text{nº of cells in 1 plant} \times \text{nº UCYN-A2/cell} \times \text{UCYN-A2 fixation rate} \times \text{conversion rates} = 211.65 \text{ mg/day}
$$
</pre>
</p>
<divclass="h2">How Much Money Would We Save?</div>
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@@ -253,21 +253,21 @@ $$
The amount of money that we would save would also depend on the efficiency of our product. We say that our product is 100% efficient if the grown plant can fixate up to 211.65 mg of nitrogen per day. We will now do an estimation of how much money we would save as a function of the efficiency of our product. To make this as accurate as possible, we are going to focus on one crop type and country. As we are a Dutch team, we will focus on the Netherlands, and for crop we will go for maize, as it is one of the most popular ones: last year, the Netherlands exported 2,621,490 kg of maize<spanclass="cite">CITE</span>. In total, there are around 200,000 hectares of maize throughout the country<spanclass="cite">CITE</span>. The typical application rate is around 155 kg of nitrogen per hectare (as recommended by WUR), which would mean that approximately 31 million kilograms of pure nitrogen are applied. Depending on which kind of fertilizer is used, this would be one amount of fertilizer or another. We will assume that we are working with urea-based fertilizer, as it is one of the most used in the Netherlands. The nitrogen content of urea-based fertilizer is 46%. This means that, in total, 67.4 million kilograms of urea fertilizer would be applied; this is, 67,400 tons of fertilizers. The price of urea fertilizer is 350 euros per ton. This would mean that, if we follow our assumption of urea fertilizer use, the Netherlands would be spending 23.6 million euros only on fertilizer for maize.
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<pre>
<p>
$$
\text{nº ha of maize} \times \text{N}_2 \text{ application rate} \times \text{conversion to urea fertilizer} \times \text{price of fertilizer} = 23.6 \text{M euros}
$$
</pre>
</p>
<p>
We can also compute how many milligrams of nitrogen a maize plant needs per day. We already know that the general nitrogen requirement per hectare is 155 kg. As the typical plant density is 85,000 plants per hectare, and if we also consider that the typical maize growing season spans about 120 days, we get that a single maize plant in the Netherlands requires approximately 15.2 milligrams of nitrogen per day on average, as opposed to the 211.65 mg that it would be theoretically able to fix.
This would mean that we would only need a 7.18% efficiency to cover 100% of the plant's needs. As we can see in the following graph, even a small efficiency can lead to remarkable savings.
