The Dutch greenhouse horticulture sector has emitted 6-8 megatons of CO2 per year between 2000-2015 and emissions are expected to decrease to ~4 megatons of CO2 per year in 2020 [1]. 7 megatons is approximately 4% of national emissions [2].
[1] pdf, https://www.wur.nl/upload_mm/c/e/c/f827af2c-9ae6-4bb5-bb47-9...
[2] https://www.cbs.nl/nl-nl/nieuws/2018/37/co2-uitstoot-in-2017...