Sustainable alumina production
Sustainability in ultra high pure alumina production
Richard Foster
The first steps in reducing the carbon
footprint
How can the carbon footprint for High Purity
Alumina be reduced or even eliminated?
The conventional process for manufacturing
HPA is a notorious “energy hog”. The
alkaloid process yields a typical carbon
footprint of 12.3 tonnes of CO2 emitted per
tonne of HPA(1). This is an incredibly high
ratio compared to even the huge energy
consumers of the cement and steel
industries with their respective ratios of
only 0.6 and 1.85 tonnes of CO2 emitted per
tonne of cement(2,3) and steel(4,5,6)
respectively. The alkaloid process for HPA
relies on expensive, carbon-intensive
aluminium metal as its feedstock(1), which
clearly will not be acceptable in the future.
Shocked by numbers like these, consumers
and investors are making decisions on the
basis of sustainability. For example, the
Norwegian sovereign fund, one of the
largest with more than 1.1 trillion euros
invested(7), now requires all 9,000+
companies it invests in to show a plan to
reduce net greenhouse gas emissions to
zero by 2050(8). In this light, it is clear that
the alumina industry needs an alternative
manufacture 99.999%-pure 5N HPA at a
competitive price.
This is because HPA is valued for its
excellent properties in terms of chemical
stability; very high melting point; and high
mechanical strength and hardness,
particularly as sapphire. It has good thermal
conductivity but high electrical insulation. It
takes on several crystalline structures, such
as alpha (α), beta (β) and gamma (γ). α-HPA
has a low specific surface area and is very
resistant to high temperature. Inert, it has
almost no catalytic activity. γ-alumina has
excellent dispersion and a higher specific surface area, but it is inert and provides high
activity(9).
The first step in reducing the carbon
footprint and environmental effects is to
reduce the power requirement for the
manufacturing processes. This starts with
the design of the processes and the
manufacturing plant to implement
them. As a basis to reduce power
consumption: hydro metallurgy processes
use much less power than thermal process
steps.
With AEM’s proven chlorine leach –
crystalline purification (CLCP) process, for
example, the carbon footprint for HPA is
currently less than 12% of that from the
alkaloid process and can potentially be
reduced to zero in Q3 2023. Close
cooperation with the laboratory is the basis
for continuous improvement in the plant.
This is the plan for eliminating the Scope 1
category of emissions.
The CLCP process produces almost zero
waste. Hydrochloric acid, an important
input, is recycled many times within the
process before being discharged,
predominantly in the form of aluminium
chloride, which is sold as a by-product for
use in water treatment. The water from our
processes that we do not recycle is treated
and released under strict guidelines.
The next step is to source the required
power from green sources. A location rich in
hydro power and wind farms is of the
essence. This leads to both predictable
pricing and fulfilment of environmental
criteria. By-products are produced with
hydro power. As a result, there are no Scope
2 emissions.
Manufacturing HPA does not occur in a
vacuum. Reducing Scope 3 emissions means
paying attention to inputs and outputs of
production. The feedstock must arrive
bringing with it a carbon footprint of zero.
This can be achieved if the supplier uses
hydro or wind power exclusively, ideally
within the company from its own dams or
Sustainability in ultra high
pure alumina production
Richard Foster
wind installations. It is of course simplest if
the supply is from a secured source located
nearby. An alternative feedstock is
aluminium from decommissioned factories.
The product going out must match the customers’
requirements exactly so that they can minimise
their own process steps and maximise their own
productivity.
This means that HPA cannot be seen as a
commodity product where the customisation is left
to the customer; a wide and versatile product
portfolio is needed. Powder particle size can be
controlled both at the crystal-growing stage and via
subsequent milling (although the latter requires
careful control to avoid contamination by the
grinding media). Powder must be tailored to a
customer’s specific requirements for particle size,
densification, and doping. Pellets (compacted
powder in a ‘puck’ shape) must also meet exacting
specifications to fulfil their applications(9).
Customisation to meet special requirements
involves simulation, development in the laboratory
and transfer to production. Quality controls after
manufacturing complete the technical involvement
to the benefit of the customer. A location
convenient to North American and European
markets simplifies shipping.
Even if the site is not in a location where every turn
of a spade is audited and certified, transparency
must be maintained for internal and external
purposes. All systems are running to clearly identify
where things come from and where they are going.
Logging of operations is ongoing in preparation for
internal and external audits.
As we have seen, sustainability depends on many
factors large and small. Process design, reduction
of power requirements, an advantageous site,
green energy sources, clean feedstocks, and
customised products are all important to sustainably produce and deliver ultra high pure
alumina.
Emissions Scopes according to the Greenhouse
Gas Protocol(10,11)
Scope 1 – emissions from sources that a company
owns or controls directly
Scope 2 – emissions that a company causes
indirectly when the energy it purchases and uses is
produced
Scope 3 – emissions not produced by the company
itself, and not the result of activities from assets
owned or controlled by them, but by those that it’s
indirectly responsible for, up and down its value
chain.
Scope 3 emissions include all sources not within
the boundaries of Scopes 1 and 2.
References
1. Cicero Shades of Green report “Altech
Chemicals Limited”
2. https://news.wttw.com/2022/06/22/cement-carbon-dioxide-emissions-quietly-double-20-years
3.https://essd.copernicus.org/articles/13/1667/20
21“CDIAC-FF: global and national CO2emissions
from fossil fuel combustion and cement
manufacture: 1751–2017”
4.https://www.recyclingtoday.com/news/worldste
el-co2-report/
5. https://www.iea.org/reports/iron-and-steel
6. https://www.mckinsey.com/industries/metals-and-mining/our-insights/decarbonization-challenge-for-steel
7. https://www.reuters.com/business/sustainable-business/norways-sovereign-wealth-fund-tells-companies-set-zero-emission-goals-2022-09-20/
8.https://www.weforum.org/agenda/2022/09/nor
ways-massive-sovereign-wealth-fund-sets-net-zero-goal/
9.https://www.innovationnewsnetwork.com/ultra
-high-purity-alumina-sustainably-manufactured-canada/20960/
10. https://www.nationalgrid.com/stories/energy-explained/what-are-scope-1-2-3-carbon-emissions
https://ghgprotocol.org/
