If we confine the debate specifically to energy then we get approximately 25% net energy gain. The key is the use of lignin, a waste product from the hydrolysis of cellulose which cannot be fermented.

The error committed by previous ethanol producers was to gasify the lignin and use anaerobic bacteria in a bioreactor to convert the CO, CO2, and H2 into more ethanol. This produced more ethanol but resulted in a net energy loss. Other products derived from lignin which, although are useful products in-and-of-themselves, resulted in a net energy loss include livestock feed, soil fertilizer, conductive inks, conductive polymers, biodegradable plastics, high-temperature conductive adhesives, pH & moisture sensors, anti-static coatings for clean-room garments and packaging applications, anti-corrosion coatings, non-linear optical coatings, smart windows, radar-invisible stealth coatings, light-emitting diodes, transistors, electronics, the list goes on...

People erred very creatively. But the real solution was very simple: Waste lignin can be burned as boiler fuel to generate electricity, or to produce heat to aid the distillation process. This gives us a net energy gain.

With respect to other non-energy products from ethanol production, many are marketable as well:

Waste glycerin from the fermentation process can be used as compost fertilizer, livestock feed, boiler fuel, cosmetics, medicinal products, dental products, soap, dynamite, food & beverages, polyether polyols for tobacco industry, alkyd resins, suppository, humectant and emollient, moisturizers, hair care products, toothpaste, sports beverages use glycerol to prevent dehydration, lubricants, epoxy resins, paper, drying foliage with glycerin, fabric softeners, cellophane packaging material, phenol resin cementing compound, nonionic surfactant extracted from glycerin, triglyceride that substitutes for fat in food products, and so on...