Before making substantial changes and a large investment to add a methane digester to a dairy, there are many questions that need to be answered. For starters, Paul Sousa, director of Regulatory and Environmental Affairs for Western United Dairies, said a dairy should review its current manure storage and handling practices.
“Unless you want to change your manure management, you should select the digester that fits your current manure system,” Sousa advised during a Farm Credit East webinar. If a producer is happy with the current system, it is best to not modify that for the sake of a digester.
For example, Sousa pointed out that sand and digesters don’t go well together. A digester is a sealed container, and the sand must be cleaned out when it builds up. “Keeping sand out of the digester is very important,” he noted. If a dairy is committed to sand bedding, a digester may not be the right choice.
However, if there is room for improvement in the manure system, the addition of a digester could become an opportunity.
“Can the digester and related equipment improve your manure system? This is a definite yes,” Sousa stated, noting it can be a time to replace worn out equipment or make changes that were needed anyway. “You can get benefits for your dairy and manure management,” he added.
Also consider how digested manure will be handled and applied. “It will be different than the manure you are handling today,” Sousa explained.
Digestion breaks the manure down into a more liquid form. This can be a benefit if a farm wants to pump manure.
The digestion process also makes nutrients more plant available, but it does not reduce nutrient levels, so that must be considered in a nutrient management plan. Any nonmanure co-products that are added to the digester will also affect nutrient content of the digested manure.
If working with an outside partner, Sousa said to read any contracts carefully and consider how they may affect the operation. If a contract requires the farm to supply manure for the digester for 10 or 20 years, a farmer must determine if they plan to be in the business that long or if the next generation will be committed to the project.
He shared that many contracts give the developer a say about what goes into the digester, and this could include what cows on the dairy are fed, as that impacts the manure’s content. Sousa said this is something a farm must be willing to work with.
He said it is important to clarify who will maintain what equipment related to the digester, and whether or not the digester operator can utilize equipment that belongs to the dairy.