The Arithmetic of Decarburization - Part 7: Beyond Fossil Fuels: The Calculus of Nuclear Fission, Fusion, and 'Clean' Coal

The Non-Renewable Options

So far, this series has focused on renewable energy: hydro, wind, and solar. But a complete assessment of decarbonization pathways must also consider non-renewable low-carbon sources:

• Nuclear fission: Mature technology, controversial politics
• Nuclear fusion: The eternal promise, now perhaps closer
• Carbon capture and storage (CCS): Making fossil fuels “clean”
• Hydrogen from fossil sources: Currently the dominant production method

Nuclear Fission: The Numbers

Nuclear fission currently provides about 5% of global primary energy and 10% of global electricity. In the EU, the share is higher: approximately 14% of total electricity.

Austria is notably nuclear-free—the only EU country to have rejected nuclear power by referendum (1978). But neighboring countries rely heavily on nuclear:

The Physics of Fission

Nuclear fission releases energy through the splitting of heavy atomic nuclei (typically uranium-235 or plutonium-239). The energy density is extraordinary:

• Uranium fission: 82 TJ/kg (82 million MJ/kg)
• Gasoline: 46 MJ/kg
• Ratio: ~1.8 million to 1

This enormous energy density means nuclear plants require tiny amounts of fuel and produce small volumes of waste (albeit highly radioactive waste).

Economics and Challenges

New nuclear construction has become extremely expensive in Western countries:

The cost discrepancy between Western and Asian construction reflects:

• Loss of nuclear construction expertise
• Stricter safety regulations
• Complex project management
• Supply chain atrophy

For Austria, nuclear remains politically impossible. But imports of nuclear-generated electricity from neighbors are routine.

Nuclear Fusion: The Perpetual Future

Nuclear fusion—the process that powers the sun—has been “30 years away” for the past 60 years. But recent progress suggests commercial fusion might finally be approaching.

The Physics of Fusion

Fusion releases energy by combining light nuclei (typically deuterium and tritium) into heavier helium:

$$D + T \rightarrow He + n + 17.6 \text{ MeV}$$

The energy release per reaction is about 3.5 MeV/nucleon—roughly 4× greater than fission. Fuel is abundant (deuterium from seawater, tritium bred from lithium).

The Engineering Challenge

Creating the conditions for fusion requires:

• Temperature: 150 million °C (10× hotter than the sun’s core)
• Pressure: High enough for nuclei to collide and fuse
• Confinement: Long enough for energy output to exceed input

The leading approach—magnetic confinement in a tokamak—has made steady progress:

ITER: The Test of Fusion’s Promise

ITER, under construction in Cadarache, Provence, France, is the world’s largest fusion experiment. Key facts:

• Cost: €20+ billion (original estimate €5 billion)
• Timeline: First plasma 2025, full deuterium-tritium operation ~2035
• Partners: EU, US, Russia, China, Japan, South Korea, India
• Goal: Demonstrate Q ≥ 10 (net energy production)

If ITER succeeds, commercial fusion plants might be possible by 2050-2060. But fusion will not contribute to near-term decarbonization.

“Clean” Fossil Fuels

Several technologies aim to continue using fossil fuels while reducing carbon emissions:

Carbon Capture and Storage (CCS)

CCS captures CO₂ from power plant or industrial exhaust and stores it underground. The technology exists but is expensive:

• Capture cost: €40-100/tonne CO₂
• Transport and storage: €10-30/tonne CO₂
• Energy penalty: 25-40% (power plant efficiency reduction)
• Global deployment: ~40 Mt CO₂/year (vs. 36,000 Mt emitted)

CCS makes economic sense only with high carbon prices (>€80/tonne) or specific industrial applications.

Gasification

Coal or biomass gasification produces a synthesis gas (syngas: H₂ + CO) that can be:

• Burned in efficient gas turbines
• Converted to liquid fuels (Fischer-Tropsch)
• Used as hydrogen source

Integrated Gasification Combined Cycle (IGCC) plants can achieve 45-50% efficiency with easier CO₂ capture. But costs remain high and few commercial plants operate.

CO₂ Neutrality vs. CO₂ Freedom

It’s important to distinguish:

• CO₂-neutral: Net zero emissions (e.g., biomass, CCS, offsets)
• CO₂-free: Zero direct emissions (e.g., renewables, nuclear)

Hydrogen from natural gas with CCS is CO₂-neutral. Hydrogen from electrolysis with renewable electricity is CO₂-free. Both can contribute to decarbonization, but only CO₂-free sources are truly sustainable long-term.

Hydrogen from Fossil Sources

Currently, about 96% of global hydrogen production comes from fossil fuels:

Color Coding of Hydrogen

The industry has adopted a color scheme:

• Grey: From fossil fuels, no capture
• Blue: From fossil fuels with CCS
• Green: From electrolysis with renewable electricity
• Pink/Purple: From nuclear-powered electrolysis
• Turquoise: From methane pyrolysis (solid carbon byproduct)

Only green hydrogen is truly sustainable. Blue hydrogen can serve as a transition technology.

Hydrogen Purification

Industrial hydrogen often requires purification. The standard method is Pressure Swing Adsorption (PSA):

• Uses molecular sieves to selectively adsorb impurities
• Achieves 99.99%+ purity
• Recovery rate: 70-90%
• Essential for fuel cell applications (which require high purity)

The Role of Non-Renewables

For Austria specifically:

• Nuclear fission: Not politically viable domestically
• Nuclear fusion: Too far away to matter for 2030-2050 targets
• CCS: Limited domestic storage, not a priority
• Fossil-based hydrogen: Acceptable as bridge, not endpoint

The path to decarbonization runs through renewables, efficiency, and electrification. Non-renewable options may play supporting roles but cannot be the foundation of a sustainable energy system.

In the next installment, we examine the practical challenges of managing a grid powered predominantly by variable renewables—and the role of electric vehicles and hydrogen in stabilizing it.

Data from ITER Organization, IEA, World Nuclear Association