The present invention is generally directed to systems and methods for processing biomass for the production of biofuels, wherein carbon dioxide (CO2) produced as a by-product of such processing is reacted with ammonia (NH3) to produce urea (NH2)2CO, a common agricultural fertilizer. In some such embodiments, the urea so produced can be used as fertilizer for biomass production, such biomass ultimately being channeled back into the systems/methods for conversion to biofuels.