Pig City in Denmark is an example of an integrated production system combining cultivation of tomatoes and pig production. In order to determine the environmental impact from the Pig City concept, it is necessary to form a map of its nutrient cycle. In particular the nitrogen cycle is essential.
Integrated agricultural production systems are considered attractive for their opportunity to close nutrient cycles and reduce environmental impact compared to conventional production. Pig City in Denmark is an example of an integrated production system combining cultivation of tomatoes and pig production. However, it is not clear how the nutrient cycle is integrated and what the environmental performance of this system is. In order to determine the environmental impact from the Pig City concept, it is necessary to form a map of its nutrientcycle. In particular the nitrogen cycle is essential, because nitrogen emits at several places in the system in gaseous and dissolved form. The purpose of this research, therefore, was to get insight into the nutrient cycle, specifically nitrogen, and environmental impact, in terms of greenhouse gas emissions, of Pig City as a future integrated agricultural production system. Calculations were based on the main concept of Pig City and by using Dutch production figures. The total production was based on 20,000 pigs per year. These pigs, together with the parents and grandparents, require 8.849 animal places a year, corresponding to a total area of 11.503m2. The tomato greenhouse had the same area. Based on 2.25 tomato plants per m2, the greenery produced 690.224 kg of tomatoes annually. Important components of the Pig City concept include: tomato plants with rock-bedding used as an air filter for nitrogen enriched air from the pig farm; a biodigester to convert manure, slaughterhouse waste and tomato-biomass into biogas; conversion of biogas into energy in a combined heat and power system. A flow diagram is made as a representation of the total mass balance and N-flow in the Pig City system. Furthermore the Global Warming Potential (100 year) for the system as a whole is calculated with a value of 2,85 kg CO2 equivalents per kg protein (from meat and tomato’s) produced. Based on the information from the system, we were able to create a mass and nitrogen flow chart of the complete system that included all inputs and outputs. The calculation of the environmental impact should be extended to a full life cycle assessment for further comparison with other pig and tomato production systems.
Student: YATFH de Bruin
Supervisors: ir J de Vries, prof dr ir IJM de Boer