From Fossil to Solar Powered Chemistry in a Circular Economy
As most years during the past decade my family and I have been attending talks and events at the Cambridge Festival. This year one talk stood out for me as it resonated deeply with my view on necessary actions towards a solar-powered civilisation and a circular economy: “Capturing sunlight for a sustainable future” by Erwin Reisner. In this story I would like to share what I have learned so far and how it fits into a wider economic context. Bottom line: chemistry as such, even on an industrial scale is not bad per-se, only what our civilisation has made it to with regards to its inputs (fossil fuels) and outputs (pollution). There are sustainable alternatives.
Economic Context
Our Western civilisation has experienced an astounding development in the past 300 years, from the Industrial Revolution in the late 18th century over the Green Revolution to the current Information Age. All that has been, still is and may be for some time powered by fossil fuels in a take-make-waste manner: take natural resources (including fossil fuels as an industrial input), convert those into refined goods (using the energy in fossil fuels), finally dump waste and used goods into the environment. By doing so all the embodied energy is lost as well. This so-called linear economy may work on a small scale while well inside the regeneration capacity of said environment. The industrialised civilisation, however, takes, makes and wastes resources far beyond the planet’s carrying capacity which causes detrimental effects such as climate change, ocean acidification, plastics pollution, aquifer depletion, to name but a few, all crossing the planetary boundaries.
Over millions of years the planet’s biosphere has harvested solar energy and stored that energy in form of coal, oils and natural gas. This energy is now being released in a comparatively short time as the economic evolution really got off the ground once these energy source could be harnessed: starting with coal in the 18th century, oil from the late 19th century and more recently with natural gas. This happened and continues to happen in two aspects: fossil fuel proper and fossil feedstock.
Fossil fuel as energy vector
Fossil fuel in its proper sense as a substance releases the chemically stored energy upon combustion. This energy is used to power industrial processes, move goods and people, heat buildings and homes. It is also used to transform raw materials into refined goods yielding matter with more embodied energy than in its raw materials, i.e. a transfer of energy is taking place. To present an idea of the order of magnitude in fossil fuel consumption, according to the World Energy & Climate Statistics Yearbook, the global total in 2022 was:
- oil: 4.4·10¹²kg = 4,400Mt = 4.4Gt, for transport (64%), i.e. petrol and diesel, non-energy use (16%), industry (8%); percentages from Breakdown of oil consumption by sector.
- gas: 2.9·10¹²kg = 2,911Mt = 2.9Gt, for industrial use (30%), electricity generation (28%), domestic heat (20%); percentages from Natural Gas Global Consumption by End Use.
- coal: 8.5·10¹²kg = 8,500Mt = 8.5Gt, for electricity generation (58%), metallurgy (16%), residential heat (14%), industrial use (12%); percentages from The world coal consumption divided into subgroups.
The energy-related portions such as electricity or heat generation consumed 2.8Gt oil, 1.4Gt gas and 6.1Gt coal (in 2022). Each multiplied respectively with the CO2 multiplier 3.09, 2.75 and 3.67 yields about 35Gt/year CO2; these numbers stack up and align with values published on Our World in Data.
The good news about the energy part: once most industrial and domestic processes are electrified the majority of oil, gas and coal will not be needed any more (as well as its shipping); see Electrifying Everything Everywhere All At Once Is Key Climate Wedge. Our civilisation will then be fuelled by renewable energy such as solar PV & wind, with large global energy grids and utility scale storage to balance production and consumption (see Demand Response — one Response to the Anything Anytime civilisation).
Fossil fuel for the chemical product stack
Fossil matter, oil, coal and gas constitute an input into a large quantity of goods our civilisation relies on: petrochemicals and all its derivatives. The remainder of fossil fuels for industrial or non-energy use from above is still a staggering 1.9Gt oil, 1.5Gt gas and 2.4Gt coal (in 2022); most of these fossil matter constitute inputs to the petrochemical industry as shown in the layered chemical product stack below. This part of the economy delivers the material basis of our living standard: plastics, fertilisers, packaging, clothing, digital devices, medical equipment, detergents, clothing, tyres, and countless other everyday items.
For instance, hydrogen is an important feed stock at the bottom of the chemical product stack, at about 120Mt/year. According to Fast Facts About Hydrogen, 30% or 36Mt/year is produced using coal (through the coal gasification producing syngas, i.e. hydrogen and carbon monoxide) and 70% or 84Mt/year is produced using natural gas (through steam reforming). The latter alone requires 340Mt/year of natural gas, about 1/4 of the non-energy natural gas usage. Hydrogen from both sources (120Mt/year) is usually generated on site and used 37% for ammonia production (converted to urea to become fertiliser, about 220Mt/year), 43% for oil refining (hydro-cracking of long hydro-carbon chains) and 14% for ethanol production. At the top of the stack, these 220Mt/year fertiliser are needed to increase crop yields in order to produce enough food for the world population.
There are more links from basic chemicals at the bottom of the stack to aspects of modern life at the top. Plastic is another one, i.e. synthetic materials produced from chemicals lower down; about 400Mt have been produced in 2022 with the trend still increasing to a forecast of 600Mt/year by 2050 (see above), some predict even values beyond 1Gt/year. It is obvious to see the critical role chemistry plays in our lives despite its bad reputation due to pollution (and being at the “bottom” end of the industry everybody denies but depends on); chemistry at an industrial scale is a necessity for maintaining our civilisation (e.g. think fertiliser) and the life style most people would not like to miss. However, in its current shape it is not sustainable, neither on the input side (fossil fuels), nor the output side (waste and pollution). What can be done about it?
Solar circular economy
This civilisation has to evolve towards a solar powered circular economy meeting the Sustainable Development Goals; this entails many actions to change the economic system. The main focus for actions these days is on aspects such as decarbonisation of the energy market, net-zero, the electrification of all possible aspects of our economy, most notably transport and heating; all of that is necessary but unfortunately not sufficient (see Living within Planetary Limits — a Piece of Cake). One less often talked about but nevertheless very important aspect is the petrochemical industry as stated before. The incumbent fossil-fuel based industry has to be evolved into a circular chemistry fuelled by the sun, too.
Some part of the necessary feedstock into the chemical product stack can be produced through electrification, most importantly green hydrogen through hydrolysis on-site from renewable electricity delivered from utility scale solar PV installations or wind farms, if necessary through large HVDC links (it is more efficient to transport electrons than low density molecules, see HVDC Transmission Is A Key Climate Wedge & Spreading Rapidly). It is also worth mentioned that with the electrification of the industry, transport and heating, much less hydrogen is needed, e.g. no hydro-cracking. In addition, by transitioning to Regenerative Agriculture much less or no ammonia based fertiliser is needed, hence even less hydrogen.
Most feedstock into the chemical product stack, however, has to come from somewhere else, mostly by recycling what is already in use in a circular economy, the revolving and valuable mass of chemical substances. And some will have to be produced from alternative sources. Novel approaches for both have been developed by the Reisner-Lab in Cambridge, UK.
Solar Chemistry
Reisner’s chemistry starts from the greenhouse gas carbon dioxide (e.g. from traditional industrial processes, or from the air), biomass (e.g. cellulose that does not compete with food production) and plastic waste. Both biomass and plastic waste have a very high embodied energy content and are composed of hydro-carbons. There are now novel ways to process these inputs using sunlight in order to make renewable energy carriers and sustainable materials. In most cases a cocktail of smaller hydrocarbons and even hydrogen is generated; they can become an the alternative input into the chemical product stack as shown below.
The result is in essence solar-powered conversion of waste, water and air into practical fuels and chemicals through the following:
- Semi-artificial photosynthesis — “Why not combine the best that materials science and biology has to offer to develop new concepts for solar energy conversion?”
- CO2 utilisation — “Why release CO2 into the atmosphere if you could use it to make fuels and chemicals?”
- Solar Reforming — “Why make oxygen when you could make useful chemicals instead?”
All these efforts are very promising for the production of necessary inputs to the traditional chemical product stack, harnessing natural processes, and eventually replacing the need for fossil fuel inputs. Erwin Reisner is currently in the process of setting up and fund-raising for the Cambridge Circular Chemistry Centre. I do hope that this work will receive the required funding needed; the returns will be tremendous for our planet.
