Chemistry 101 for climate tech investors

Credits: ThisisEngineering RAEng, Unsplash

This article is part of our CO2 valorisation series. Read the main CO2 valorisation article here. Keen to know about the market opportunity? See this article. Want to deep dive into the CO2 conversion methods? Get all the details here.

Contrary to many generalist venture capital investments, understanding popular buzzwords like blockchain and B2B SaaS won’t be enough for climate technology. To fully leverage the carbon utilisation market opportunity, we need to focus more on hardware rather than software. Moreover, we need to know what the potential pathways and outcomes are for carbon utilisation.

Chemistry is a central pillar to understanding CO2 conversion methods, so let’s take a look at some essentials:

Carbon is an atom and carbon dioxide (CO2) is a molecule. Hydrogen can both be an atom (H) and a molecule (H2). Have a look at Figure 1: the left-hand side of this figure shows two examples of atoms. The simplest and smallest atom is hydrogen (H), which consists of a positively charged core, a proton, with a negatively charged particle (electron) circling around it. You can think of it as a fruit fly circling around an apple. The weight of the electron is negligible compared to the weight of the proton. The proton thus determines the atom’s weight, which is conventionalised to atomic number 1 (equal to 1.66*10–24 grams) in the case of H.

Carbon (C), another important atom for climate tech, has six protons, six electrons, and to hold the core together carbon also has six neutrons. These are particles without charge: neutral. Carbon’s atomic number is the sum of the protons and neutrons, resulting in atomic number 12. Molecules are formed when multiple atoms are sharing electrons and consequently form chemical bonds. The right-hand side of Figure 1 displays a methane (i.e. natural gas) molecule, which consists of one carbon atom and four hydrogen atoms, resulting in CH4.

Figure 1. Schematic overview of atoms (left) and molecules (right). Atoms consist of protons (red), neutrons (green), and electrons (blue). Molecules are formed by sharing electrons between atoms, leading to a chemical bond. Credits: Extantia.

CO2 valorisation: the process of creating value from emissions

The issue with valorising CO2 molecules is that they are relatively stable and therefore require high energy input to be transformed. Each oxygen atom shares two electron pairs with the carbon atom and therefore the strong carbon-oxygen bonds need a lot of energy to be broken. This energy is typically delivered in the form of heat, electricity, and/or light. To lower the energy barrier and speed up the transformation process, a catalyst can be used.

Due to the thermodynamic stability of CO2 molecules, the use of this greenhouse gas as a chemical feedstock is currently limited to a small number of industrial processes. Several approaches like thermochemical (using heat), electrochemical (using electricity), photochemical (using light), and biological (using microorganisms) conversion of CO2 into more valuable products are being investigated in academic as well as industrial settings.

For hydrocarbons (also referred to as alkanes or alkenes in more technical terms), a molecule with two carbon atoms would be called ethane (or ethene if the bond between the two carbon atoms is a double bond). Methane (i.e. natural gas) is the simplest hydrocarbon, containing only one carbon atom. Ethane has two carbon atoms. Methanol is the simplest alcohol with one carbon atom, while ethanol has two carbon atoms. Molecules with a carbon chain length between 5 and 11 are typically used as gasoline, between 10 and 16 as kerosene, and between 12 and 18 as diesel. See Figure 2 below for the molecular structures of such molecules.

Figure 2. Molecular structures of alkanes and alkenes (i.e. hydrocarbons) as well as alcohols that can be created from carbon dioxide (CO2) and hydrogen (H2). Credits: Extantia.

Up to now, only thermochemical CO2 conversion has been proven to produce long-chain hydrocarbons (5 or more carbon atoms) at high yields. Creating products with longer hydrocarbon chains than methane is beneficial because they store more energy and are easier to transport off-grid compared to gaseous methane. Creating long-chain hydrocarbons from CO2 is therefore a promising pathway toward a circular economy and will be useful in the next decade to produce, for example, sustainable fuels for aviation and for diesel engines. With that said, let’s look at the four CO2 conversion methods.