How does it work?
The user can enter the most sensitive parameters of the life cycle of biofuels. Subsequently, the life cycle inventories of all process steps are computed and normalized to the functional unit of “driving one person km (pkm) with an average car”. On this basis, life cycle impact assessment methods are applied with focus on greenhouse gas emissions (global warming potential, GWP100) and on total environmental impact points (Swiss method of ecological scarcity, UBP06). The results are graphically compared to a biofuel reference path and to a fossil reference. In addition, the environmental impacts are checked against sustainability criteria. If the criteria are not fulfilled, the user may change his entry data and get more insights on the measures he should take to fulfil them. Figure 2 shows the workflow of the SQCB.
Although the life cycle of biofuels is influenced by a large number of factors, only few have a high relevance on the overall environmental impact assessment. The questionnaire of the SQCB strongly focusses on data entry for the agricultural step (mineral and organic fertilizers, pesticide use, irrigation, yield, former land use) and the processing step (energy use, chemicals, allocation, etc.). In addition, compliance with the requirements for social criteria has to be confirmed.
Life Cycle Inventory (LCI) calculation
As shown by Figure 2, different paths for the transformation of questionaire data into LCI data are used. In general, some of the data entered by the user can directly be used as inventory data, e.g. the amount of mineral fertilizer applied per ha (step 1). Another part of the life cycle inventory is used by default from the background data, e.g. the machine use on the field (step 2). In addition, the LCI is supplemented with data resulting from models using (i) questionnaire data as input (step 3) or (ii) already determined LCI flows (step 4). For example, the CO2 emissions from land use change are modelled on the basis of quentionnaire data, whereas the N2O emissions or Nitrat emissions are calculated according to the amount of mineral fertilizer applied, i.e. the already determined LCI flows. When all required LCI flows are completed, the life cycle inventory is calculated (step 5). In this step, all LCI flows are allocated and normalized to the functional unit of ‘driving one person km (pkm) with an average car’.
Life Cycle Impact Assessment (LCIA)
In the next step, the normalized inventory flows are multiplied with their respective environmental impacts. The life cycle impact assessment is applied with focus to greenhouse gas emissions (global warming potential, GWP100) and the Swiss method of ecological scarcity (UBP06). This endpoint method evaluates environmental damages by means of the difference between environmental impacts and legal limit values in the context of the Swiss legal framework. This method is chosen in order to reflect accurately the overall effects on the environment, as the driving parameter of the changes in the system is placed in Switzerland. However, if required additional impact methods could be added simply.
The results are graphically compared to an average biofuel reference path (e.g. biodiesel from rape calculated with user data is compared with reference data of biodiesel from rape) and to a fossil reference (petrol, low sulphur, at regional storage). Moreover, the results are benchmarked against the Swiss criteria for the tax exemption of biofuels. Furthermore, the user can evaluate the critical factors of his value chain. If the criteria are not fulfilled, the user can change his entry data and get more insights on the measures he should take to fulfill them. If the results are positive, the user has a first indication that deposing a request for tax exemption can be worthwhile.