It depends. For example, in some jurisdictions, it may be less costly to use biogas because of the alternative cost of the fugitive methane emissions and what they need to pay for those. It depends on what the total value proposition is for that particular project.
For example, if you operate a large landfill in California, you're going to be paying some cost for your methane emissions. So by offsetting those methane emissions, capturing them, defraying the cost of diesel fuel, and instead using that fuel in your vehicles, it may be more cost effective than just doing some alternative method.