A California-based waste and energy company has purchased an anaerobic digester in Dane County that converts manure from dairy farms into biogas, which is considered a more environmentally friendly replacement for natural gas.

Brightmark Energy, based in San Francisco, will use the digester — located northwest of Madison in Dane — to convert about 90,000 gallons of dairy waste per day into biogas that can be used for heating, electricity production or vehicle fuel.