XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 171
Aside from the methodology presented herein, there are a
number of other conclusions are worth highlighting:
• Mining wastes, especially those from mining of Ni
and PGMs can represent a ready source of feedstock
for carbonation. Other opportunities such as Ni lat-
erite heap leaching can also provide Mg2+ in solution
as a starting point for carbon capture, and processing
of other serpentine, wollastonite-rich feeds or those
containing Mg clays (Li) can also present opportuni-
ties for carbonation.
• The CO2 emissions arising from construction of
process plants need to be amortised and are typically
an order of magnitude or more lower than opera-
tional CO2 emissions arising from the comminution
process.
• CO2 emissions associated with the mining and pro-
cessing of ore are strongly dependent on comminu-
tion, with both energy consumption and grinding
media consumption contributing significantly to the
overall CO2 footprint.
• Optimisation of the grind size for CO2 sequestra-
tion shares similarities with grind size optimization
for metal extraction. The optimum grind size is heav-
ily dependent on the rate of conversion for a given
grind size but for three scenarios assessed in this pub-
lication they were all very fine (P80s in the region of
2–5 µm).
• Long distance transportation of carbon sequestra-
tion feedstock can pose a significant additional CO2
footprint and ideally should be avoided to the largest
degree possible.
Transportation
Transportation is a highly energy-intensive process. Table 6
lists approximate emissions for barge, train and road trans-
port based on data published by the US EPA(SOURCE).
Train transport is the most favourable option and road trans-
port is by far the most taxing in terms of CO2 emissions.
To put this in perspective, shipping of olivine from
Sibelco’s Åheim quarry in Norway (largest producer of oliv-
ine in the western world) to Norfolk on the East Coast of
the US (Virginia, 6535 km distance) would emit around
0.17 t CO2/t olivine or around one third of the estimated
carbon capture budget after milling. This is approximately
the same value as all construction and operational CO2
emissions associated with the size reduction process from
plant feed to a 5 µm P80 olivine. Given the energy intensity
of the milling process and maintaining the optimum condi-
tions for the sequestration reaction it makes sense to build
these plants in locations with low CO2 electricity (e.g.,
high proportion of renewable or nuclear energy), but the
calculations in this section also highlight the importance
of keeping transportation distances as low as possible. It
is important to note that CO2 can also be transported by
pipeline, and the same goes for milled olivine, so shipping
of olivine may paint an overly pessimistic picture.
CONCLUSIONS
This paper presents a methodology for estimating the CO2
emissions embodied in the construction and operation of a
mine. This methodology incorporates the following steps:
• Estimation of CO2 emissions from construction of
a process plant based on embodied emissions from
steel and concrete used in plant construction
• Estimation of CO2 emissions based on specific energy
consumption in comminution and other plant pro-
cesses as well as consumption of steel grinding media
and liners and the CO2 emissions they embody.
• Optimisation of the grind size based on construction
and operational CO2 emissions
Table 5. Summary of sequestration capacities and optimum grind size for three scenarios
Scenario
Peak Carbon Sequestration Capacity
(t CO
2 /t olivine)
Optimum Grind Size (P
80 ,
µm)
Pessimistic 0.54 2
Intermediate 0.49 5
Optimistic 0.46 4
Table 6. Typical emissions per tonne-kilometer for different
transportation methods (US EPA, [ref])
Transportation Method Emissions (kg CO2/t/km)
Ship 0.026
Train 0.014
Truck 0.132
Aside from the methodology presented herein, there are a
number of other conclusions are worth highlighting:
• Mining wastes, especially those from mining of Ni
and PGMs can represent a ready source of feedstock
for carbonation. Other opportunities such as Ni lat-
erite heap leaching can also provide Mg2+ in solution
as a starting point for carbon capture, and processing
of other serpentine, wollastonite-rich feeds or those
containing Mg clays (Li) can also present opportuni-
ties for carbonation.
• The CO2 emissions arising from construction of
process plants need to be amortised and are typically
an order of magnitude or more lower than opera-
tional CO2 emissions arising from the comminution
process.
• CO2 emissions associated with the mining and pro-
cessing of ore are strongly dependent on comminu-
tion, with both energy consumption and grinding
media consumption contributing significantly to the
overall CO2 footprint.
• Optimisation of the grind size for CO2 sequestra-
tion shares similarities with grind size optimization
for metal extraction. The optimum grind size is heav-
ily dependent on the rate of conversion for a given
grind size but for three scenarios assessed in this pub-
lication they were all very fine (P80s in the region of
2–5 µm).
• Long distance transportation of carbon sequestra-
tion feedstock can pose a significant additional CO2
footprint and ideally should be avoided to the largest
degree possible.
Transportation
Transportation is a highly energy-intensive process. Table 6
lists approximate emissions for barge, train and road trans-
port based on data published by the US EPA(SOURCE).
Train transport is the most favourable option and road trans-
port is by far the most taxing in terms of CO2 emissions.
To put this in perspective, shipping of olivine from
Sibelco’s Åheim quarry in Norway (largest producer of oliv-
ine in the western world) to Norfolk on the East Coast of
the US (Virginia, 6535 km distance) would emit around
0.17 t CO2/t olivine or around one third of the estimated
carbon capture budget after milling. This is approximately
the same value as all construction and operational CO2
emissions associated with the size reduction process from
plant feed to a 5 µm P80 olivine. Given the energy intensity
of the milling process and maintaining the optimum condi-
tions for the sequestration reaction it makes sense to build
these plants in locations with low CO2 electricity (e.g.,
high proportion of renewable or nuclear energy), but the
calculations in this section also highlight the importance
of keeping transportation distances as low as possible. It
is important to note that CO2 can also be transported by
pipeline, and the same goes for milled olivine, so shipping
of olivine may paint an overly pessimistic picture.
CONCLUSIONS
This paper presents a methodology for estimating the CO2
emissions embodied in the construction and operation of a
mine. This methodology incorporates the following steps:
• Estimation of CO2 emissions from construction of
a process plant based on embodied emissions from
steel and concrete used in plant construction
• Estimation of CO2 emissions based on specific energy
consumption in comminution and other plant pro-
cesses as well as consumption of steel grinding media
and liners and the CO2 emissions they embody.
• Optimisation of the grind size based on construction
and operational CO2 emissions
Table 5. Summary of sequestration capacities and optimum grind size for three scenarios
Scenario
Peak Carbon Sequestration Capacity
(t CO
2 /t olivine)
Optimum Grind Size (P
80 ,
µm)
Pessimistic 0.54 2
Intermediate 0.49 5
Optimistic 0.46 4
Table 6. Typical emissions per tonne-kilometer for different
transportation methods (US EPA, [ref])
Transportation Method Emissions (kg CO2/t/km)
Ship 0.026
Train 0.014
Truck 0.132