Careful How You Calculate Urban Agriculture’s Carbon Intensity
While the methods in the Hawes et al paper seem sound, the results made no sense to me.
By Sally Brown
Sally Brown, BioCycle Senior Adviser, is a Research Professor at the University of Washington in the College of the Environment.
BioCycle
Feb 27, 2024
Excerpt:
A best case is gardeners who amend their soil with compost made from material that would have otherwise gone to the landfill (biosolids or food scraps). The compost is made in a commercial facility with strong odor controls that also destroy any fugitive emissions. The compost is delivered to the site in bulk and no additional fertilizer is used. The plant waste at the garden is composted in a well- maintained bin with browns routinely added. Here methane avoidance from landfill diversion is likely enough to more than level the playing field. Add to that soil carbon sequestration, fertilizer avoidance, increased yield from quality amendments and you might just come out ahead.
A worst-case scenario is gardeners who amend their soil with fertilizer and “boutique” compost purchased in small bags from a big box store. The local feedstocks for composts (biosolids and food scraps) are sent to the landfill. Plant waste at the site is piled up without any attention paid to addition of browns or turning, resulting in fugitive methane emissions. Here those landfill methane emissions would likely dig a hole deep enough to bury any benefits. Driving to and from the store to get those 20-pound bags of compost only adds insult to injury.
Read the complete article here.
Comparing the carbon footprints of urban and conventional agriculture
