Methane joins milk as dairy profit item

Monday 25 May 2015

A few California dairymen are dispensing home-grown natural gas as well as milk as a profit item, pleasing their environmentalist friends as well as their neighbors.
They are turning their dairies' most reliable by-product — cow manure — into odorless natural gas, which they can sell easily and profitably or use to meet costly energy requirements on the farm.

But the digesters, key to converting the waste, each require an investment upward of a million dollars, so the decision to increase product output demands serious consideration. Financial assistance from the California Department of Food & Agriculture and a few other sources helps tip the balance in favor of conversion.
So far, about a dozen of California's 1,500 commercial dairies have installed the digesters, which turn a daily helping of cow manure, plus some green waste if available, into methane, being referred to by the environmentally sensitive as biogas. Its properties are identical to natural gas mined from deep in the earth.

The main unit of a digester installation is the vessel in which the manure and other convertible materials ferment. At the same time, it is the most vulnerable piece of the installation. Heat and pressure in it must be carefully maintained and monitored. It can't be taken for granted as its cousin the compost pile can. Decomposition can be accelerated or slowed down by control mechanisms, producing biogas at a manageable rate.

A working digester at the 4J Dairy in Pixley was chosen as a demonstration site in February. Located only about 20 miles from the World Ag Expo show grounds in Tulare, it offered dairymen and others visiting the farm show an opportunity to observe it in operation by taking a short side trip from the Ag Expo site.

On hand were representatives of DVO Inc. its manufacturer, Calgren Renewable Fuels and Regenis, the company that installed the unit. DVO Inc. and Regenis were exhibitors and World Ag Expo. The sponsors of the occasion emphasized that the Pixley unit was the first in California to be manufactured and installed entirely by American companies.

Daily supplies of manure keep the digester operating nonstop. The methane gas created by the fermentation process is captured and can be stored or bottled in convenient sized containers. Sale of the gas — to natural gas distributors, for example — necessitates storage in truckload sized tanks. Low- volume users can be accommodated by smaller containers.

After its 20-day journey through the digester's fermentation vessel, spent manure exits the structure as inert organic material, perfect for mulching yards, gardens and crops. It is closer to a liquid form than when it entered, is purged of harmful bacteria and full of nutrients.
Dairymen can encourage dumping of lawn clippings and other green waste in large quantities by dealing with homeowners, of course, but also commercial landscapers, even municipalities. Green waste and the manure make perfect companions for the journey through the digester. Experts say mayonnaise, salad dressing and restaurant grease trap collections also spice up the ride through the digester.

Dairies generally consume large amounts of energy, so creating it in the form of biogas saves dairy farmers from having to purchase it from commercial suppliers. One California dairy with an adjacent cheese factory employs a digester to create biogas to energize cheese-making equipment in addition to meeting his dairy's energy requirements.

The use of digesters by dairymen is still in its infancy but destined to grow. The presence of American companies that can create and install all the elements required for profitable operation is sure to boost acceptance and growth.
One day, consumers might be able to toddle off to the dairy outlet and pick up a canister of biogas to accompany their dairy purchase. Homogenized, of course.

This article appeared on www.appeal-democrat.com

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