Determination of fossil-derived carbon ratio of tomato plants in greenhouse with CO2 enrichment using biobased content method

Abstract

CO2 enrichment is an important technology, but it is unclear how much of the enriched CO2 is utilized by plants in greenhouses with CO2 enrichment. Recently biobased carbon (C) was detected in hydrocarbon fuels using ASTM D6866–21 Method. We obtained the fossil-derived C ratio (FDCR) by subtracting the biobased C ratio (%) from 100. We determined the FDCR of tomatoes using this method in the greenhouse with CO2 enrichment. Tomatoes were grown in a growth chamber (GC) and tomatoes with CO2 enrichment using a CO2 gas cylinder and in a greenhouse with kerosene-burning CO2 enrichment in winter. The CO2 released from the cylinder had a FDCR of 100 %, but tomatoes grown in the GC over time had a FDCR of about 60 %. Those of open-air tomatoes, on the other hand, were only about 2 %. The tomatoes grown in the GC used about 60 % from cylinder CO2 and 40 % from outside air CO2. A positive correlation was observed between the FDCRs in the plants and the ratios of each period when the number of days grown open air and GC were changed. It was thought that the FDCR could be accurately measured. Every week, lateral shoots from a tomato plant in a greenhouse with CO2 enrichment were analyzed. Using environmental data, the percentage of photosynthesis during the CO2 enrich period to the total period (PPCO2) was calculated using simulation software. The PPCO2 was calculated for 1 to 8 days before lateral shoot sampling correlated positively with the FDCR in lateral shoots. Because their FDCR of the lateral shoots that appeared during CO2 enrichment at about 600 μmol·mol−1 (PPCO2=100 %) was around 35 %, it was determined that 65 % of their C came from CO2 in the outside air. This is thought to be due to the influx of CO2 from outside air during CO2 enrichment due to ventilation, etc. FDCR using standard test methods for determining the biobased content can help clarify the amount of fossil fuel absorbed from CO2 enrichment, making it useful for efficient CO2 enrichment in a greenhouse.