Slurry from roughly this many dairy cows would fill Welsh Water's stated spare digester capacity

2,000–4,500 cows2024-25estimatelow confidence

A pilot, not a solution, unless capacity is built. Welsh Water does not say it would accept farm slurry.

7,053 tDS of spare capacity ÷ 9% dry matter = about 78,000 tonnes of slurry a year; ÷ 23 tonnes a cow a year = about 3,400 cows housed all year. That is roughly 1.3% of Wales' 254,100 dairy cows. Capacity for a watery feedstock is often limited by volume, not only dry solids, so this may overstate it; cows housed for part of the year make less slurry, so it may understate the herd. Hence the wide range.