Life cycle analysis of a biogas-centred integrated dairy farm-greenhouse system in British Columbia

This study investigates the potential integration of a dairy farm and a greenhouse into an eco-industrial system to promote waste-to-energy and waste-to-material exchanges. Natural gas consumption is substituted by renewable biogas generated from anaerobic digestion (AD) of the dairy manure; CO₂ for plant enrichment in greenhouses is supplied by biogas combustion and the digestate (digestion residue) from digesters is used as animal bedding, plant growing media and liquid fertilizers.A life cycle analysis (LCA) was conducted to quantify the environmental impacts of the eco-industrial system in comparison to the conventional agriculture practices. The results show that the integrated system reduces non-renewable energy consumption, climate change impact, acidification, respiratory effects from organic emissions, and human toxicity by more than 40%. If the digestate surplus is treated as a waste, the integrated system shows an increase in eutrophication and respiratory effects from inorganic emissions while all the analyzed impacts are reduced if the digestate can be used for substituting chemical fertilizers.