Last week, the United Nations' Intergovernmental Panel on Climate Change (IPCC) released its “Climate Change and Land” report, which detailed how climate change is already threatening food and water supplies for humans. The report also states that one significant source of anthropogenic greenhouse gas emissions come from global food production, including landfilling of food waste. Yet it is already within our power to reduce these emissions.
David Shonnard is a professor of chemical engineering at Michigan Technological University, the Richard and Bonnie Robbins Chair in Sustainable Materials and the director of the Sustainable Futures Institute. To demonstrate how anaerobic digestion can reduce food-related emissions, Shonnard and other Michigan Tech researchers used life cycle assessment (LCA) in a carbon footprint and energy analysis of biomethane (Bio-CH4) from a mixture of food waste and dairy manure in Denver, Colorado.
Anaerobic digestion is a promising alternative to landfilling of food waste and to conventional dairy manure management in order to reduce methane emissions. Key results show that life cycle greenhouse gas emissions for Bio-CH4 production and combustion from anaerobic digestion conversion of food waste and dairy manure, compared to waste landfilling and conventional management of dairy manure emits -3.5 kg carbon dioxide (CO2) equivalents/kg Bio-CH4 produced.
This emission intensity compares favorably to fossil natural gas, which is equal to +4.3 kg CO2 equivalents/kg CH4. The study also suggested that by diverting all of the food waste and dairy manure in the U.S. to anaerobic digestion, 0.41% of overall U.S. GHG emissions (approximately 7 billion tons CO2) can be saved annually.
“Engineers handle complexity by simplifying it into different stages of the life cycle and focusing their efforts on one piece at a time,” Shonnard said. “Life cycle assessments enable us to look at a product’s environmental impact; it can help focus our attention on how to improve the performance over the whole life cycle.”