There is no point in adding a co-digestion product to a digester unless the co-digestion product has a higher wet mass methane potential than the primary substrate. Since the swine manure slurry has the lowest wet mass potential of all the substrates graphed in Figure 2, any of the other substrates should increase gas production when mixed with the swine manure. On the other hand, adding corn processing plant byproduct to the dairy manure would probably decrease overall biogas production. Adding food scraps to the dairy manure would increase gas production.