When doing an LCA that models processes like forestry, quarrying, mining, that rely on the use of heavy machinery, such as excavators, crushers, conveyors, dump trucks, it is necessary to account for the emissions associated with the production of that machinery/equipment that is deemed to be consumed in the process.
In order to work that out, you need to know the machinery unit numbers (how many of each are used), their service life, their weights, and the production volume (mass), i.e. how much product is the machine used to produce per year.
For example, we have two 50 metric tonne dump trucks on site that have a service life of 10 years each and help produce 10 000 tonnes of product per year. As there is no ecoinvent data point for a 50 t truck, we will use Lorry production, 40 metric ton (Reference product: lorry, 40 metric ton ), with a correction factor:
50 t / 40 t = 1.25 correction factor
2 units / 10 years = 0.2 units/year
0.2 / 10 000 tonnes = 0.00002 units/tonne
1.25 * 0.00002 = 0.000025 units/tonne
We have created an excel calculator (attached below) to help with your own calculations, where the above can be found as an example:
In this example, the chosen ecoinvent data point is in units (rather than in kg), so the transportation impacts need to be accounted for separately under Additional transport. The weight for transported mass is the quantity given in A3 multiplied by the weight of vehicle. Taking our example above, we have 0,000025 of Lorry production, and the lorry weighs 50 t, then the transported mass is 0,000025 * 50 000 = 1.25 kg.
The calculator includes some of the most common ecoinvent resources used for this purpose, however, you can add additional data to the sheet as needed.
Please note that only machinery directly involved in the manufacturing needs to be accounted for and usually it would not apply to simple factory-produced products, which can have the capital goods excluded.