Manganese Life Cycle Assessment Results

Manganese Life Cycle
Assessment Results
This fact sheet presents selected key findings of the
Manganese Life Cycle Assessment (LCA), building on the
methods published in the 5th fact sheet of the series. The
study, conducted by Hatch Ltd. on behalf of the IMnI,
provides the most complete measure of the environmental
footprint of global manganese alloy production and was the
flagship project of IMnI’s Sustainability Programme.
1. Project Overview
LCA is the most recognized, comprehensive tool for
measuring the environmental performance of a product or
service across its entire supply chain. The Manganese LCA
was undertaken to serve simultaneously as a tool for
benchmarking site performance and as a source of reliable
environmental data for external stakeholders. The study was
compliant with ISO 14040 standards and peer-reviewed by
an independent third party. The study encompassed the
entire production chain leading to SiMn, FeMn and refined
FeMn alloys, including mining, smelting, power generation
and other associated indirect processes (Figure 1).
2. LCA Environmental Impacts
The LCA used mass-energy models of 17 mines and
smelters scattered across 5 continents to calculate the
potential environmental impacts for three standardized impact
categories: Global Warming Potential (GWP), measuring
greenhouse gas (GHG) emissions contributing to climate
change; Acidification Potential (AP), measuring emissions of
acid-rain-generating gases; and Photochemical Ozone
Creation Potential (POCP), measuring emissions of gases
contributing to the formation of smog and ground-level ozone.
Each impact category is expressed in equivalent units of
common gases associated with each category (e.g. CO2
equivalent) and can be used to compare manganese to other
products and processes. Table 1 reports the impact category
results for manganese alloy production, listed according to
where they occur along the manganese life cycle.
Table 1: Environmental impact category results for the production life
cycle of 1 kg of manganese alloy.
LCA Impact
Category
Direct/
Primary
Indirect
Power
Indirect
Other
Total Life
Cycle
GWP (kgCO2e)
1.9
3.5
0.5
6.0
AP (gSO2e)
6.3
36.5
1.8
45.0
POCP (gC2H4e)
0.8
2.0
0.2
3.0
3. Criteria Air Contaminants
The LCA also tabulates emissions data for conventional
pollutants including nitrogen oxides (NOX), sulphur oxides
(SOX), and particulate matter (PM). Each pollutant is typical
of combustion-related processes observed in mobile
equipment, furnaces and in fossil-fuel-based power
generation.
NOX emissions are dependent on the
characteristics of the combustion zone, increasing with higher
temperatures and nitrogen and oxygen concentrations.
Combustion-related SOX emissions are sensitive to the sulfur
content of the fuel source. PM, while generated during
combustion, are also related to fugitive emissions sources
such as dusts generated through the handling of raw
materials. Life cycle results for each pollutant are reported in
Table 2.
Table 2: Criteria air contaminant emissions results for the production life
cycle of 1 kg of manganese alloy.
LCA Impact
Category
Figure 1: Schematic representation of LCA system boundaries, including
primary manganese production steps and indirect, upstream processes.
Direct/
Primary
Indirect
Power
Indirect
Other
Total Life
Cycle
NOX (g)
4.7
12.3
1.7
18.7
SOX (g)
2.8
27.5
0.6
30.9
PM (g)
3.3
3.4
3.0
9.6
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4. Energy
5. Smelter Byproducts & Waste
Environmental impacts and air emissions in the manganese
life cycle are closely tied to the fuels, carbon reductants and
electricity required to power the mining equipment and
electric arc furnaces essential for manganese production.
Figure 2 compares the energy delivered directly to the
manganese process with the associated upstream energy
sources from which they originate. While 1 kg of alloy uses
35.5 MJ of energy, the associated upstream energy required
is more than doubled. Electricity and carbon reductants such
as coal and coke contribute 93% of all energy delivered to
manganese processes, primarily consumed in the smelting
process. The significant fraction of coal-fired electricity and
the carbon reductant required for smelting result in 69% of all
energy originating from coal-derived sources. Shifting the
reliance of upstream electricity generation away from coal will
have the most significant impact on air emissions associated
with manganese alloy production.
Waste materials generated directly from manganese
processes consist of mine waste rock, overburden and
tailings and smelter slag. Slag, consisting mostly of the inert,
non-metallic products of smelting, is an important source of
recoverable manganese and aggregate material for road
construction. Figure 3 shows the average flows of slag
generated from SiMn and FeMn furnaces. On average, the
manganese industry finds alternative uses for 86% of all slag
generated. Slag recovery helps reduce the waste generated
from manganese production and offsets a portion of the
environmental impacts associated with manganese mining.
Figure 3: Slag generation and recovery flows for average SiMn and
FeMn smelters for 1 kg of manganese alloy production.
6. Conclusions
Figure 2: The energy demanded by the manganese process requires
upstream resources to be extracted, transformed, and transported to the
gates of manganese mines and smelters. Roughly half of the energy
contained in the resources at extraction is lost before entering the
primary manganese supply chain.
The Manganese LCA Project provides a range of metrics to
measure and continuously improve the environmental
performance of the manganese industry. More information
and additional results including average consumption rates,
manganese throughput, and other process parameters, are
available on-line at http://www.manganese.org.
Further Information:
There are more fact sheets in this series: Fact Sheet 1. The derivation of limit values for manganese and its compounds in freshwater: data availability,
Fact Sheet 2. Construction of the biotic ligand models for manganese, Fact Sheet 3. Accounting for bioavailability in assessing potential risks of
manganese in freshwater, Fact Sheet 4. Assessing the potential terrestrial risks from manganese, and Fact Sheet 5. Life Cycle Assessment (LCA)
aimed at measuring the overall environmental performance of the global manganese alloy industry, Fact Sheet 6. Manganese in Groundwater:
Research and potential risks, Fact Sheet 7. Occupational Exposure Levels for Manganese (OEL), Fact Sheet 8. Manganese - reassuring evidence
about male reproductive health effects. Fact Sheet 9. Manganese Industry - Socio-Economic Assessment. Fact Sheet 10 Electrolytic Manganese
Dioxide and Pyrolusite Ore: What’s the Difference? You can find them at: http://www.manganese.org. For more information please contact:
[email protected].
December 2014
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