Fuel inputs in the food system could be reduced by 50%

Here is the abstract from David Pimentel's recent article in Human Ecology:

Petroleum and natural gas are the primary fuels in the US food system. Both fuels are now in short supply and significant quantities are being imported into the USA from various nations. An investigation documented that fossil energy use in the food system could be reduced by about 50% by appropriate technology changes in food production, processing, packaging, transportation, and consumption. The results suggest that overall, farmers benefit as well as consumers.

Somebody tell me, why not?