Standardized emissions inventory methodology for open-pit mining areas

Abstract

Introduction

There is still interest in a unified methodology to quantify the mass of particulate material emitted into the atmosphere by activities inherent to open-pit mining. For the case of total suspended particles (TSP), the current practice is to estimate such emissions by developing inventories based on the emission factors recommended by the USEPA for this purpose. However, there are disputes over the specific emission factors that must be used for each activity and the applicability of such factors to cases quite different to the ones under which they were obtained. There is also a need for particulate matter with an aerodynamic diameter less than 10 μm (PM₁₀) emission inventories and for metrics to evaluate the emission control programs implemented by open-pit mines.

Standardized emission inventory methodology

To address these needs, work was carried out to establish a standardized TSP and PM₁₀ emission inventory methodology for open-pit mining areas. The proposed methodology was applied to seven of the eight mining companies operating in the northern part of Colombia, home to the one of the world’s largest open-pit coal mining operations (∼70 Mt/year).

Results

The results obtained show that transport on unpaved roads is the mining activity that generates most of the emissions and that the total emissions may be reduced up to 72% by spraying water on the unpaved roads. Performance metrics were defined for the emission control programs implemented by mining companies. It was found that coal open-pit mines are emitting 0.726 and 0.180 kg of TSP and PM₁₀, respectively, per ton of coal produced. It was also found that these mines are using on average 1.148 m² of land per ton of coal produced per year.

Appendix A

Table 3 Activities involved in open-pit mining and its classification by area source

Table 4 TSP and PM₁₀ emission factors used for each activity involved in open-pit mining

List of symbols

A :

Blasting horizontal area with a dept <21 m (square meter)

A _i :

Intensity of activity i

b :

Days of stocking or exposition (days)

c:

Dry days during the year (days)

d :

Average high where the material is released (meter)

e :

Percentage of wind speed >5.33 m/s (percent)

E _i :

Estimate the mass of TSP or PM₁₀ that is released into the atmosphere by activity i (kilograms per year)

E _f,l :

Emission factor for aggregate handling and storage in piles of granulated material (kilograms of TSP/ton)

E _f,i :

Emission factor for activity i (kilogram per intensity of activity i)

k :

Intensity of the applications (liters per square meter)

m :

Number of days in the period (days)

M::

Moisture content of the handled material (percent)

M _p :

Material's properties

M _c :

Meteorological conditions

p :

Average daytime evaporation rate (millimeter per hour)

n :

Number of rainy days in the period with precipitation levels exceeding 0.254 mm (days)

r :

Average daily traffic (vehicles per hour)

R ² :

Coefficient of determination

S _a :

Emitting activity

S :

Average vehicle speed (kilometers per hour)

s :

Silt content (mesh 200) of the handled material or on the surface of the road (percent)

t :

Average time between spray applications (hour)

U :

Wind speed (meters per second)

U*:

Average train speed (meters per second)

VKT:

Kilometers traveled per vehicle (kilometers per vehicle)

W::

Truck average weight (tons)

i, j :

Indexes

α, β, γ, ζ :

Experimental constants.

η _j :

Efficiency of the emission control measure j (percent)

η _s :

Efficiency of emission controls for spraying water (percent)

* :

Constant values area applied whenever equations are not applicable