The contribution of capital goods in agricultural LCAs
The aim of life cycle assessment (LCA) studies is to model a product’s life-cycle as completely as possible, in order to make accurate calculations. This comprehensiveness makes a study time-consuming and extensive. Not all details are relevant. Therefore, it could be useful to define the elements which are included, or not, prior to the study. One of the detailed elements involved in these studies concerns capital goods, such as agricultural machinery and buildings. Mike van Paassen, a masters student of Industrial Ecology at TU Delft and Leiden University, is currently investigating this topic at Blonk Consultants. His masters thesis examines the influence of capital goods on the production of strawberries, cereals and milk. The aim of his research is to find out if it really is necessary to include capital goods in detail in an LCA or to simple leave this out. The intention is to use the results of his study in Agri-footprint of Blonk Consultants. It is the ideal study for a grower’s son with a background in chemical technology and industrial ecology.
Comparative study of 3 productsThe first step in the study was to determine what exactly is meant by the term ‘capital goods’. A practical definition is chosen: capital goods are all goods with a useful life of more than one year, such as machinery, instruments and buildings, that are used during the life cycle of a product. Everything that is used for less than one year, such as fertilisers, diesel, natural gas, pesticides and substrate, are considered as ‘operational inputs’, also qualified as consumables.
To obtain a picture of the contribution of these capital goods on LCA results, Mike is carrying out a comparative study of 3 products (strawberries, milk and cereals) using a model with and without capital goods included. To keep the study manageable its scope is restricted to capital goods used on the farm.
Filtering and combining the available dataA fair amount of data is available on the operational inputs. For example, Wageningen University regularly publishes reports of yields, prices, propagation material (seeds, plants or parts of plants) and the use of chemical fertilisers, pesticides and energy per crop. Supplementing these data with assumptions and data on emissions from chemical fertilisers and heavy metals makes the LCA without capital goods more or less complete. Capital goods can be roughly divided into two groups: machinery and buildings. Data on machinery is abundant, but they are not available in a collated form, which means that they have to be filtered and combined to ensure the model is representative.
The example of a tractorThe useful life of a tractor can be derived from the depreciation period in years. From information on the use of the tractor per year it is possible to calculate how many hours the tractor is used during its useful life. From information on other factors, such as material composition, transport, maintenance and repairs, it is possible to determine the contribution of a tractor or machine per hour or per hectare.
This is much more complicated for buildings. In the absence of information from the literature and rules of thumb, the researcher is forced to obtain primary data from suppliers. This primary data can then be used to calculate weights and useful life.