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Creating Renewable Energy on a Yakima Dairy

4/23/2025

These Yakima dairy cows are creating energy in the form of milk and manure.

OUTLOOK, Wash. – Dan DeRuyter, owner at George DeRuyter & Sons Dairy, sums up the dairy farm storyline well: “Without the manure, you don’t have fertilizer for your crops, but if you use it in the right way, it can be a benefit in many different ways.” For this Yakima dairy farm, manure provides an opportunity not just for improved crop production, but also for increasing sustainability far beyond the farm’s borders.

Like any dairy farm, the focus is milk production, but the by-product of manure turns out to be a renewable resource that is equally valuable. Not only does George DeRuyter & Sons Dairy use their manure as fertilizer, it is also creating clean energy through a manure digester.

The dairy industry in the Yakima Valley is highly regulated. The DeRuyter family responded to this by seeking new technologies for their farm. The advancements they have chosen to utilize meet quality standards and improve the environment. These technological elements, which include the digester, are features considered to be the most advanced water and clean air measures that can be taken at a dairy production facility.

DeRuyter collaborates regularly with energy and soil specialists to improve existing manure technologies on his farm.

DeRuyter shares that his perspective on dairy farming is creating an “ecosystem.” Dairy farming is a closed-loop system where cows produce milk and manure. The manure is then used as a fertilizer for the crops that cows consume. Manure is truly a valuable resource to a dairy farm.

“We shouldn’t think of manure as a waste,” says DeRuyter’s Soil Scientist, Scott Stephen at AgriManagement Inc.. “When handled properly, it meets all the nutritional demands a crop needs to grow effectively.”

In addition to spreading the manure on their crops in the recommended timeline as provided by his state-required Dairy Nutrient Management Plan and CAFO permit, the manure provides additional resources for DeRuyter’s farm.

DeRuyter’s manure digester is one such feature. A manure digester is a closed separation system, usually in the form of a tank that uses anaerobic digestion to convert manure into other products such as biogas, bedding material, and/or soil nutrients. With the absence of oxygen, microorganisms are able to break down the manure, eliminating nearly all the potentially harmful bacteria, and turning the manure into more readily available forms of nutrients, perfect for plants. And, of course, it also produces renewable energy!

For this dairy farm specifically, the digester is able to convert methane and other gases in the manure into compressed natural gas. Once the gas is collected, the solids are separated out and used as bedding for the cows. Thus, not only is it creating something beneficial for the cows, it is providing renewable energy for the surrounding community.

A second separation system called a Dissolved Air Flotation system (or DAF), creates solids that are used for crop enhancement. DAF is a technology that separates solids and nutrients from wastewater or manure. This helps to produce a nutrient-dense solid that serves as a vital source of nutrients for dairy farm crops. The DAF also plays a role in creating a low-solids water that can be used for irrigation and other purposes. Using this process, ensures that the farm is reducing water waste.

Solids from the manure digester act as a comfortable and clean bedding that is preferred by dairy cows.

Solids from the dissolved air flotation system serve as a nutrient-packed fertilizer for dairy crops.

It is crucial that a dairy manages its manure well, since manure is such a vital resource for crops. By incorporating these steps to the processing of manure, George DeRuyter & Sons dairy ensures that the manure is being managed properly and in a way that positively affects the environment. It also supplies the crops with the exact nutrients it needs to thrive.

Dan Evans, President of Promus Energy LLC, spoke to the greater value of these projects for the animals and the community. “Using these systems, there are benefits to cow comfort and health. The flush flume system is cleaner and [the cows] are more comfortable using digested dairy fiber as bedding. But the most rewarding thing is the environmental footprint of this dairy is much smaller…this farm is reducing the amount of methane that comes off their lagoon by about 70%.”

Taking care of land and animals is an investment in the future. George DeRuyter & Sons Dairy cares about their cows, employees, and community. Manure management is simply one part of that investment.