Appreciate the link to the paper. Will be an interesting read.

But at first glance here's a wee problem with the study: It takes the worst practices of urban farms and compares them with the best practices of industrial farms. It is not comparing "home grown produce" from the OP, where some of the principle offenders - not using materials for a long time - may, in fact, be used for a long time. It also doesn't study small-scale non-urban farms. Which to me IS a decentralization but by people who know what they are doing.

One example is composting, where it correctly surmises that people who don't know how to compost correctly.... wait for it now, don't compost correctly and produce higher GHGs.

And you are mischaracterizing the results and omitting a key finding: "However, some UA crops (for example, tomatoes) and sites (for example, 25% of individually managed gardens) outperform conventional agriculture. "