Modelling the amount of materials to improve inventory datasets of greenhouse infrastructures

Purpose

Previous studies have shown the importance of including agricultural capital goods in environmental assessments. In particular for protected crops, greenhouse structural components may account for nearly 30 % of the total in environmental impact categories such as resource depletion and global warming. The lack of appropriate datasets can make it difficult to include these structural components. The present paper provides a modelling approach for the greenhouse inventory stage to provide better assessments of greenhouse production systems.

Methods

In this study, four main greenhouse structures were assessed: a glass greenhouse, a multi-tunnel greenhouse, a local Mediterranean type known as the parral greenhouse and a low-tunnel greenhouse. After selecting the main materials of the structure, we generated equations to calculate the amount of the main structural materials as a function of the main greenhouse dimensions. We performed a quality assessment of the data used for different greenhouse structures. We also calculated a simplified environmental assessment made by the different structures to the climate change category in order to test the effects of the different amounts of material in the four greenhouse types.

Results and discussion

Equations to calculate the amount of the main greenhouse materials as a function of greenhouse size are provided. For the four greenhouse types under consideration, statistical correlations showed a good fit between the amounts of greenhouse materials and the parameters related to the main greenhouse dimensions, such as greenhouse perimeter, surface and volume. The results from the complementary impact assessment study show that glass greenhouses contributed the most in the climate change category, with an average value of 2.9 kg CO₂ eq m^?2. After variability was taken into account, multi-tunnel and parral greenhouses showed similar values of between 0.5 and 1.3 kg CO₂ eq m^?2, while low-tunnel greenhouses had the lowest ranges, between 0.4 and 0.6 kg CO₂ eq m^?2. The environmental assessment was done using the square metre as a reference flow, so the actual impact depends on the functional unit selected, which is usually the yield.

Conclusions

Application of the equations developed in this study provides an easy way to calculate the quantity of materials used to make greenhouses of different dimensions, thus resulting in more accurate calculation of greenhouse production system impacts. This analysis also highlights the importance of the different amounts of materials used to build these structures and, therefore, the need to include ranges of uncertainty in environmental analyses.