Photosynthesis

Photosynthesis is the process by which organisms use energy from sunlight to convert carbon dioxide (CO2) into carbohydrates, such as sugar (glucose). Plants or algae derive energy from these carbohydrates, and use this to create building blocks from which different parts – such as tubers, seeds, stems and leaves in plants – grow.

Photosynthesis takes place in plants, algae and some bacteria that contain chlorophyll.  With the exception of some bacteria, all organisms capable of photosynthesis use water in addition to carbon dioxide to synthesize these sugars. A waste product of this reaction is oxygen. Although algae are simpler than higher plants, photosynthesis takes place in a similar way in these organisms.

This short film explains how plants use energy from the sun, CO2 and water to make sugars.

Light and dark reactions

Photosynthesis consists of two reaction paths: light reaction and dark reaction, the latter known as the Calvin cycle . In the light reaction, solar energy is converted into chemical energy (in the form of the compounds ATP and NADH). This chemical energy is used in the Calvin cycle to produce sugar (glucose).

Efficiency

Let’s assume that in 2050 the Netherlands will have a total energy requirement of 50 gigawatts. The amount of space we will need to be able to meet this requirement will depend on how efficiently we can convert solar energy. If we were only able to use about 1% of the sun’s energy, we would require a surface area of 3,000 square metres per inhabitant. That would mean that the entire land surface of the Netherlands would need to be covered with plants, purely for energy production. If we are able to use 10% of the sun’s energy, for example through photovoltaic solar cells or algae, an area equivalent to the built-up area plus all agricultural land would be sufficient. Even if we manage to achieve efficiency in the region of 50%, which would theoretically be possible using artificial leaves, we would still need an area equivalent to the entire Dutch road network and the IJsselmeer.

More knowledge is needed

We need to know much more in order to improve the efficiency of photosynthesis. We need to know more about exactly how the photosynthesis process works, and about the factors that influence it. We also need to know more about the genetic processes underlying photosynthesis and more about nanomaterials that can improve the absorption of sunlight.

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