Thank you for the comments! To respond in general to both -
Mitch, yes, agree that a driver in most cases is for a municipality or a company (food industry in particular, or in rural locations related to agriculture) to reduce waste disposal costs, and in a sustainable manner, and usually with a regulatory compliance driver. And agree that most often there must be some aspects of infrastructure already in place in order for this niche collection issue to be viable. Evelyn - my focus is more about biosolids handling that can incorporate pulped waste food, than on grey water.
There is a European company that has been installing smaller systems for years that I really admire, that could be implemented in the US in situations that perhaps don't have the existing infrastructure for biosolids handling - http://www.schmack-biogas.com/. I think these smaller systems if coordinated regionally, could go a long way to processing of household food waste and produce a 'cleaner' biosolids product for land application, and capture of methane for fuel.
In the absence of such a food waste collection system at present, Philadelphia has added to their building code the requirement of garbage disposals on all new construction. We know that the added organic matter to wastewater processing improves the biology, and produces a better sludge for land application. And the food waste is kept out of the landfill loop. Our biosolids residual processing uses the digester-produced methane to dry the biosolids, both to remove all possible pathogen impact, and so the dried pellets can also be used as fuel in addition to fertilizer.
In short, we know how to do this, but some entrepreneurial spirit in this realm could expand it much further.