What is a good mass efficiency?
Somehow I am not convinced there exists something like a "good value of mass efficiency". It is a relative thing that can be used to compare different processes yielding the same final product, but I doubt in sense of comparing processes yielding different products.
Producing one ton of steel uses 280 m3
of water, producing one ton of beef requires 4000 m3
of water*. Do you thin you can draw any conclusions from comparing these numbers?
*different sources give different numbers, exact values don't matter here.