High Biosolids Transport Costs and Carbon Footprint

All the UK utilities transport bio-solids from rural and smaller sites, and some of the larger sites by tankers. Due to the process, the content is predominately water with some solids, possibly 2-3%. The cost is enormous in £ and the carbon footprint is extremely high. These costs of are readily available on the government site and run in multi-millions for them all.  Why are they not doing more to reduce cost and carbon footprint? What is the biggest obstacle?