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Not illuminated
HPS lamps. This is the ‘old fashioned' types type of greenhouse lighting
LED illumination. As LED lighting becomes affordable, many growers switch to this efficient system.
HPS lamps + CHP (combined heat and power). The CHP produces most of the electricity demand.
LED lamps + CHP. As LEDs use less electricity, the greenhouse becomes a net electricity producer.
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Conclusions
Using illumination increases both costs and crop production significantly
The scenario with the highest electricity consumption (HPS and no co-generation) has the lowest CO2 emission. This is because it is assumed that the electricity from the grid is all coming from sustainable sources. In case the average CO2 emission of electricity in the public grid of the Netherlands (350 gram per kWh in the early twenties) is assumed to be associated to the bought electricity, the HPS greenhouse without CHP becomes the greenhouse with the highest CO2-emission, although the largest emission is then produced elsewhere. The CO2 emission of option 2 would then be 51.5+234.6 x 0.350 = 134 kg/(m² yr).
Assigning this 350 gram CO2-emission to public grid electricity would mean that the CO2-emission associated with option 4 would increase with 87.1 x 0.35 = 20 kg/(m² yr), whereas the CO2-emission associated with option 5 would decrease by 32.7 x 0.35=11.4 kg/(m² yr).
This shows that LED-lighting is always to be preferred compared to HPS-lighting.
