Combined heat and power (CHP) as a possible method for reduction of the CO2 footprint or organic greenhouse horticulture

In recent years, the horticultural sector has been confronted with questions about the carbon footprint of its products. In greenhouse cultures, energy consumption is the main component of the CO2 emission. To save energy, many Dutch greenhouse companies use CHP to heat their greenhouses. These growers may sell the superfluous electricity produced by the CHP to the national grid, thereby generating two products; the horticultural product, e.g. a tomato, and the electricity. The CO2 emission of the electricity production should be deducted from the total CO2 production of the CHP, in order to calculate the CO2 emission that should be assigned to the production of the crop. To investigate the carbon footprint of a greenhouse production system to cases are compared: with and without a CHP system to heat the greenhouse. An example for grown tomatoes in The Netherlands is worked out. It shows the specific input factors and their impact on the CO2 footprint. The functional unit used is kg CO2 per 1000 kg product, and the system boundary is from seedling production until the delivery of product at the distribution centre of wholesalers or supermar-kets. The CO2 footprint of the tomato crop grown without cogeneration is 55% higher than that of the crop grown without cogeneration and more than triple that of the conventional crop grown with CHP. The use of CHP is a way to reduce the CO2 footprint for tomato growers.