Solid particulate emissions from blasting, greenhouse gases from engines and electricity generation, soil loss, desertification, altered rivers, damaged land, poisoned waters, injured communities, fines, fees and changing regulations have costs. Deciding which costs to include and how within a Strategic Mine Plan depends on strategic questions and the right modelling tools.
To incorporate ecological costs into a Strategic Mine Planning methodology, planners need a set of workflows capable of delivering traditional multi-scenario analyses of NPV optimized with the following ecological cost models:
- Value depreciation of direct ecological services
- Value depreciation of indirect ecological services
- Carbon emission costs
- Restoration costs
Dassault Systemes Strategic Mine Planning Industry Process Experience offers workflows enabled by the 3DEXPERIENCE platform and GEOVIA Whittle and SIMULIA Process Composer and Results Analyzer (formerly known as Isight in early development).
Mine planners use GEOVIA Whittle to determine investment strategy and to deliver robust mine plans that maximize profitability while factoring real mining constraints. Whittle is used in scoping, feasibility, life-of-mine scheduling, and ongoing re-evaluation of mine plans throughout the production phase. SIMULIA Process Composer provides simulation-driven design and process automation. In Strategic Mine Planning its Design of Experiments capabilities are employed to automate the Whittle workflows.
With these versatile software tools, mine planners can integrate ecological costs to arrive at a Green NPV reflecting real costs of doing business.
Solution in Stages: Ecosystem Values and Strategic Objectives
Ecological services, a relatively new term, are defined as the direct and indirect contributions to human well-being. There are four types: provisioning, regulating, cultural and supporting services.
Before a mine is established, a Green NPV depends on first characterizing and putting values to those contributions. Acquisition cost of the land or estimates of net profits for that land in the future. Land values expressed in terms of net primary productivity based on soil protection, local climate regulations, disturbance mediation, atmospheric gasses regulation, and nutrient cycling. Quantifying landscape, culture, flora or fauna is more subjective.
Once the ecosystem is defined, companies must establish clear strategic objectives with control parameters defining technical, economic and ecological project performance indicators such as NPV, payback period, total ecological cost, damaged area or carbon emissions.
These are the first two steps in a nine-stage Green NPV solution. Additional stages cover carbon estimates, damaged area costs, pushbacks, production schedules and restoration.
Estimate Carbon Emissions
One way to combat global warming is by using carbon capture and storage. This requires estimating carbon emissions during the mine operations by assessing energy consumption (mainly concentrated in extraction and processing operations) and its corresponding emission factors. An emission factor (EF) is a coefficient used to convert mining activity data into estimates of greenhouse gases (GHG) released into the atmosphere.
In an open pit mine direct energy consumption is concentrated in extraction operations (diesel/gasoline and electricity) and ore processing (electricity).
The carbon emissions from the direct consumption of fossil fuels are estimated according to carbon emission factors and energy use per unit amount of mined rock. Indirect carbon emissions are estimated through electricity consumption which must be converted into an equivalent amount of carbon by considering the country’s energy matrix or according to the proportion of electricity that comes from coal combustion. Finally, the carbon emission costs for a particular mine are determined by the estimated amounts of carbon emitted and the carbon capture and storage costs. This is included in the planning workflow through an increase in the mining and processing costs compared to the base case.
Generate Strategic Pit Shell Sequence
The strategic pit shell sequence in the SMP process considers additional mining and processing costs for carbon emissions as mining and processing operational expenses.
Estimate Damaged area and Associated CAPEX
Damaged areas include pits, waste dumps and tailings dams, each determined from the ultimate pit. Generally, investment costs (CAPEX) estimates depend on an operation’s extraction and processing rates. Additionally, an analysis includes estimated value of associated direct ecological services, determined by the area affected by the operation.
Define pushbacks for mine scheduling
The pushback definition is based on the specific requirements of each project. Mining phases can be chosen according to the amount of contained ore, a specific sequence or chain, vertical development constraints or the maximization of the NPV.
Generate Preliminary Production Schedule
At this stage, using the results of the previous stages, develop a preliminary plan to estimate the growth of the damaged area by pushback expansions, waste dumps, and tailings dams in combination with the area to be recovered.
Include Restoration and Indirect Ecological Costs
Using the estimation of the lost value of each indirect ecological service, the recovery cost and the damaged area growth according to the preliminary mine plan, it is possible to estimate total indirect ecological and restoration costs from the first period until the ecological function recovery after the life of the mine.
Generate alternative and final production schedule
Across four cost categories mentioned at the beginning of this article, a Strategic Mine Plan quantifies the technical, economic and ecological parameters.
Conclusion: Quantifying Ecosystems
For at least the past 25 years, earth scientists, economists and industry planners have worked to place a price tag on what’s left of the natural world that benefits human society, or “ecological services.” Best estimates put it somewhere around US$125 trillion, but it’s probably much higher, figured at 1.8 times global gross domestic product (GDP).
With quantified ecological values in hand, and powerful modelling and simulation tools in reach, mine planners can now plan for a more financially, ecologically and socially balanced and inclusive future.
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Ross MILNE is a Mining Engineer with 36 years experience and knowledge and knowhow in open-pit mining operations. He has built extensive cross-functional experience in the mining industry in EMEAR. Starting in mining operations, he advanced to lead bauxite exploration, mining, processing and shipping operations. Subsequently he moved into OEM earthmoving equipment consulting and sales and then FMS, high-precision guidance and equipment health solutions. He now consults on processes and solutions for the Minerals & Materials Industry, capitalizing on his knowledge to advise mining organizations on their people, process and technology transformational journeys