XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 167
leaching process. In effect, this process has carried out
reaction (2) in the pursuit of Ni dissolution from a later-
ite ore, providing a residual process stream that is suitable
for carbonation. Likewise, Mg and Ca represent major
constituents of the waste stream from both salar (Li) and
geothermal brines. Concentrations are much lower than in
their equivalent ores, but nonetheless these waste streams
may represent future opportunities for carbonation. These
sorts of opportunities might serve to improve project eco-
nomics (depending on carbon tax for a given project) or,
more likely, improve ESG credentials of a mining operation.
METHODOLOGY
Construction Emissions
Aside from energy emissions during processing, the usage
of concrete and steel in process plant construction are major
CO2 emitters. A review of concrete and steel-related carbon
emissions (see Tables 1 and 2) produced average emissions
of 0.146 t CO2/t concrete and 1.97 t CO2/t steel.
The range of concrete and steel usage for process plant
construction is dependent on plant layout, mill configura-
tion and also the design philosophy and can be as low as
0.02 t steel/kW installed and 0.19 t concrete/kW installed
(Ausenco averages) but often are around 0.08 t steel/kW
installed and 0.4 t concrete/kW installed (Lane et al., 2016).
The approach taken in this methodology is to ‘amortise’ the
construction emissions over the financial payback period of
the plant to convert these values to a t CO2/t ore.
Operational Emissions
For the purposes of this methodology, emissions from raw
materials extraction can broadly be attributed to mining
activities, ore processing and concentrate transportation. A
study by NRC Canada (2005) reported an energy consump-
tion of 5.8 kWh/t ore for the mining process. Assuming
this is fully delivered by burning diesel (11.0 kWh/L) at
30% efficiency and emissions of 2.7 kg CO2/L diesel that
leads to emissions of 4.8 kg CO2/t ore.
Emissions from ore processing are dependent on the
type of process, but generally arise largely from the con-
sumption of energy and grinding media (Ballantyne et al.,
2012) in the comminution process. Both factors are impor-
tant considerations in plant design and well monitored/
reported during operation. The embodied emissions in
steel production provide a direct conversion from steel con-
sumption in comminution to CO2 emissions and depend-
ing on energy source, the specific energy consumption can
be translated directly to CO2 emissions. Table 3 lists several
quoted figures for CO2 emissions related to the production
of ceramics, giving an average of 0.288 t CO2/t ceramic. No
reference could be found specifically for ceramic grinding
media but the tile/refractory emissions values in Table 3 are
considered comparable to ceramic media. As a side-note,
these emissions are significantly lower than those associated
with steel. Given the lower wear rates typically seen with
ceramic media in stirred milling applications, this would
imply that stirred milling is significantly better from a car-
bon emissions better but a detailed trade-off between these
two milling methods is outside the scope of this conference
paper.
For CO2 sequestration purposes it is assumed that a
bulk olivine ore (i.e., dunite) is mined and that no flotation
or other upgrading is required. Emissions associated with
maintaining the high pressure and temperature required
for the carbonation reaction are not included in this cal-
culation. This paper aims to characterise the CO2 ‘budget’
before starting this reaction to provide an envelope that this
reaction would have to work within to allow the reaction
to proceed.
CARBON BALANCE
Based on the methodology and benchmarks outlined in
this paper, a carbon balance was set up for a 100 t/h plant
processing grinding a dunite feedstock (90% olivine) to
Table 1. Concrete production CO
2 emissions
Data Source
Emissions
(t CO
2 /t concrete)
Samarin (1999) 0.180
Hammond and Jones (2011) 0.150
Nazari and Sanjayan (2017) 0.144
Heidelberg Cement 0.132
Lafarge Holcim 0.129
Cemex 0.139
Table 2. Steel production CO2 emissions
Data Source
Emissions
(t CO2/t steel)
Bernstein et al. (2007) 2.00
Hammond and Jones (2011) 2.03
World Steel Association (2020) 1.89
Table 3. Ceramics production CO2 emissions
Data Source
Emissions
(t CO
2 /t ceramic)
Ceramic Sector Report, 2019 0.29
Ecofys, 2009 (refractory products) 0.23– 0.34
Ecofys, 2009 (tiles) 0.30
Mezquita et al., 2009 (tiles) 0.265
leaching process. In effect, this process has carried out
reaction (2) in the pursuit of Ni dissolution from a later-
ite ore, providing a residual process stream that is suitable
for carbonation. Likewise, Mg and Ca represent major
constituents of the waste stream from both salar (Li) and
geothermal brines. Concentrations are much lower than in
their equivalent ores, but nonetheless these waste streams
may represent future opportunities for carbonation. These
sorts of opportunities might serve to improve project eco-
nomics (depending on carbon tax for a given project) or,
more likely, improve ESG credentials of a mining operation.
METHODOLOGY
Construction Emissions
Aside from energy emissions during processing, the usage
of concrete and steel in process plant construction are major
CO2 emitters. A review of concrete and steel-related carbon
emissions (see Tables 1 and 2) produced average emissions
of 0.146 t CO2/t concrete and 1.97 t CO2/t steel.
The range of concrete and steel usage for process plant
construction is dependent on plant layout, mill configura-
tion and also the design philosophy and can be as low as
0.02 t steel/kW installed and 0.19 t concrete/kW installed
(Ausenco averages) but often are around 0.08 t steel/kW
installed and 0.4 t concrete/kW installed (Lane et al., 2016).
The approach taken in this methodology is to ‘amortise’ the
construction emissions over the financial payback period of
the plant to convert these values to a t CO2/t ore.
Operational Emissions
For the purposes of this methodology, emissions from raw
materials extraction can broadly be attributed to mining
activities, ore processing and concentrate transportation. A
study by NRC Canada (2005) reported an energy consump-
tion of 5.8 kWh/t ore for the mining process. Assuming
this is fully delivered by burning diesel (11.0 kWh/L) at
30% efficiency and emissions of 2.7 kg CO2/L diesel that
leads to emissions of 4.8 kg CO2/t ore.
Emissions from ore processing are dependent on the
type of process, but generally arise largely from the con-
sumption of energy and grinding media (Ballantyne et al.,
2012) in the comminution process. Both factors are impor-
tant considerations in plant design and well monitored/
reported during operation. The embodied emissions in
steel production provide a direct conversion from steel con-
sumption in comminution to CO2 emissions and depend-
ing on energy source, the specific energy consumption can
be translated directly to CO2 emissions. Table 3 lists several
quoted figures for CO2 emissions related to the production
of ceramics, giving an average of 0.288 t CO2/t ceramic. No
reference could be found specifically for ceramic grinding
media but the tile/refractory emissions values in Table 3 are
considered comparable to ceramic media. As a side-note,
these emissions are significantly lower than those associated
with steel. Given the lower wear rates typically seen with
ceramic media in stirred milling applications, this would
imply that stirred milling is significantly better from a car-
bon emissions better but a detailed trade-off between these
two milling methods is outside the scope of this conference
paper.
For CO2 sequestration purposes it is assumed that a
bulk olivine ore (i.e., dunite) is mined and that no flotation
or other upgrading is required. Emissions associated with
maintaining the high pressure and temperature required
for the carbonation reaction are not included in this cal-
culation. This paper aims to characterise the CO2 ‘budget’
before starting this reaction to provide an envelope that this
reaction would have to work within to allow the reaction
to proceed.
CARBON BALANCE
Based on the methodology and benchmarks outlined in
this paper, a carbon balance was set up for a 100 t/h plant
processing grinding a dunite feedstock (90% olivine) to
Table 1. Concrete production CO
2 emissions
Data Source
Emissions
(t CO
2 /t concrete)
Samarin (1999) 0.180
Hammond and Jones (2011) 0.150
Nazari and Sanjayan (2017) 0.144
Heidelberg Cement 0.132
Lafarge Holcim 0.129
Cemex 0.139
Table 2. Steel production CO2 emissions
Data Source
Emissions
(t CO2/t steel)
Bernstein et al. (2007) 2.00
Hammond and Jones (2011) 2.03
World Steel Association (2020) 1.89
Table 3. Ceramics production CO2 emissions
Data Source
Emissions
(t CO
2 /t ceramic)
Ceramic Sector Report, 2019 0.29
Ecofys, 2009 (refractory products) 0.23– 0.34
Ecofys, 2009 (tiles) 0.30
Mezquita et al., 2009 (tiles) 0.265