http://cdiac.ornl.gov/SOCCR/pdf/SAP2.2_Entire_Report_Draft4.pdf p.264
"Practices that substantially reduce (reduced-till) or eliminate (no-till) tillage-induced disturbances are being increasingly adopted and generally increase soil carbon stocks while maintaining or enhancing productivity levels (Paustian et al,. 1997; Ogle et al., 2003) (Fig. 10-2). Estimates of the technical potential for annual cropland soil carbon sequestration are on the order of 50–100 Mt C per year† in the United States (Lal et al., 2003; Sperow et al., 2003)"
p. 266
"Methane emissions from manure storage are proportional to duration of storage under anoxic
conditions. Handling solid rather than liquid manure, storing manure for shorter periods of time, and
keeping storage tanks cool can reduce emissions from stored manure (CAST, 2004).
More important,
capture of CH4 produced during anaerobic decomposition of manure—in covered lagoons or small- or
large-scale digesters—can reduce emissions by 70–80% (Mosier et al., 1998b). Use of digester systems is spreading in the United States, with 50 digesters currently in operation and 60 systems in construction or planned (NRCS, 2005). Energy production using CH4 captured during manure storage will reduce energy demands and associated CO2 emissions."
Anaerobic digesters are what closed-loop ethanol plants are designed to use to produce energy from cattle poop. You reduce fossil fuel usage to almost nothing and reduce methane pollution at the same time.
http://www.xldairygroup.com/pressrelease.cfm?ContentKey=620"The concept is to use waste produced by the dairy cows to make energy that would be used to turn corn into ethanol and biodiesel, said Dennis Corderman, chief executive and chairman of XL Dairy Group. Byproducts of the ethanol and biodiesel production will be cycled back to produce internal energy for the biorefinery and to provide feed for the dairy cows, he said. "The biggest difference between us and other ethanol plants is we will use waste streams from the dairy to produce our own energy," he said. "It will provide the electrical and heat and steam energy for the entire facility." Because the plant will supply its own power, the operation will have an energy efficiency ratio of 10-to-1, he said. That means for every one British Thermal Unit of energy put into the process - including indirect energy consumption such as fuel needed to grow corn - the equivalent of 10 units of energy in the form of ethanol and biodiesel will be produced. Conventional ethanol plants have an energy efficiency ratio of about 1.2-to-1, he said."