Summary:Aluminum Producers Emit Some of the World's Most Damaging Greenhouse Gases

This is a summary of an article from Inside Climate News, originally titled "Why Chinese Aluminum Producers Emit So Much of Some of the World’s Most Damaging Greenhouse Gases".

Problem

PFCs(...)( perfluorocarbons - especially the gases CF₄ and C₂F₆ ) are greenhouse gases that are less common than CO₂, but far more potent and long-lasting.

Some aluminum factories emit unreasonably large amounts of PFCs - especially in China where there are weak regulations.

More than half of the aluminum in the world is produced in China, but it is responsible for 81 percent of the industry’s emissions of PFCs. Simple automation could go a long way toward cutting them.

The following chart shows the PFC emissions, expressed in tonnes of CO₂-equivalent (CO2e) per tonne of aluminum produced. This varies widely by factory.

Just for perspective

Other greenhouse gas emissions:

Aluminum production requires a lot of electricity - which adds 5 to 16 tons of CO₂ per ton of aluminum, if the electricity is generated from fossil fuels (as most of the world's electricity currently is).

See mathsSee maths

Natural gas power plants (best case, high efficiency, no fugitive emissions):

aluminium.rq_electricity

17000 kWh/tonne

Energy required to produce aluminium metal

"Aluminium production is energy intensive. About 17,000 kWh of electricity are required to produce 1 tonne of aluminium."
[www.sciencedirect.com/topics/engineering/aluminum-production Aluminum Production - an overview - ScienceDirect Topics]

natural_gas.ghg_by_energy

53.07 kg / million btu

CO2 emissions of burning natural gas

Does not include the fugitive methane emissions from unburned fuel. Those vary by how the gas is burned.

https://www.eia.gov/environment/emissions/co2_vol_mass.php

natural_gas_combined_cycle_power_plant.efficiency

60%

How much of the natural gas's heat energy becomes electricity, in an advanced "combined cycle" power plant

This is considered a "maximum" value - the best natural gas power plants achieve this.
Simpler/older natural gas plants (no combined cycle) have only an efficiency of 33%, same as [coal_power_plant.efficiency].

Read more: https://energyeducation.ca/encyclopedia/Natural_gas_power_plant

tonnes per tonne (calculation loading) Coal power plants:

coal.ghg_by_energy

95.35 kg / million btu

CO2 emissions of burning coal

https://www.eia.gov/environment/emissions/co2_vol_mass.php

coal_power_plant.efficiency

33%

How much of the coal's heat energy becomes electricity

Transformative Power Systems | Department of Energy
https://www.energy.gov/fecm/transformative-power-systems

tonnes per tonne (calculation loading)

Solution

The article describes in detail how factories can avoid almost all PFC emissions.

Overview

How aluminum metal is made:

Smelting: Aluminum oxide (mined from the earth) is placed in a molten salt bath (which contains fluoride salts) and electricity is applied. This converts the aluminum oxide into pure metallic aluminum.

How PFCs are emitted:

When the concentration of aluminum oxide gets too low in the mix, the electricity causes the salts to react with the carbon anodes, producing the gases CF₄ and C₂F₆.

Which factories emit the most PFCs:

Any that rely on workers to visually monitor the aluminum oxide levels, manually turn the mixture by poking it with a stick, etc.

Solution:

Automated systems, controlled by sensors.

The article mentions that the solution could also be profitable (win-win), by improving energy efficiency.

Unanswered questions

There clearly needs to be more talk about the physical costs of such new systems. What would be the environmental impact of creating all this new factory equipment, and how would it compare to the PFC emissions avoided? ^{[RESEARCH needed]}

I would wager that the new systems would be a net benefit for the environment - but that's purely a guess from intuition. Detailed data is hard to come by, but we should at least try to make a rough estimate based on simple costs.