Digesters may not be the best fit for milk being dumped in Wisconsin.  David Crass, partner at Michael Best law firm in Madison explains.
Farmers need to think through a few important considerations. These include: 

1. Putting milk into the digester substrate mix, and taking it out again down the road could cause big technical issues: Digesters substrates must be carefully controlled in order to maintain the microorganism balance in the digester. Introducing too much high-energy milk can cause microorganism die-off, or imbalance in the microorganism mix. If those things are avoided, other problems can result when milk is removed from the substrate stream. Put simply, the ramp up and ramp down of milk introduction into the digester needs to be managed carefully and scientifically.
    
2. If your digester is producing gas to generate RFS credits, putting milk in the digester will change the type and value of those credits. Gas produced exclusively from manure generates credits known as “D3 RINS” under the RFS Program. But, when you add food sources in addition to manure, the digester loses its D3 RINS qualification, and may be eligible only for “D5 RINS” under the RFS, which are generally only about half as valuable as D5 RINs at today’s prices. Impact on RINS needs to be considered. For now, the U.S. Environmental Protection Agency (EPA) has taken the position that qualification for D3 RINS is solely based on the cellulosic content of the digester feedstock. However, EPA is expected shortly to release guidance for industry regarding enforcement of this distinction during the ongoing milk disposal crisis.